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Urban waste piles are reservoirs for human pathogenic bacteria with high
levels of multidrug resistance against last resort antibiotics: A
comprehensive temporal and geographic eld analysis
Madalitso Mphasa
a,1
, Michael J. Ormsby
b,*,1
, Taonga Mwapasa
c
, Peter Nambala
a,g
,
Kondwani Chidziwisano
c,d
, Tracy Morse
e
, Nicholas Feasey
a,f,g,1
, Richard S. Quilliam
b,1
a
Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Kamuzu University of Health Sciences, Blantyre, Malawi
b
Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA. UK
c
Centre for Water, Sanitation, Health and Appropriate Technology Development (WASHTED), Malawi University of Business and Applied Sciences, Private Bag 303,
Chichiri, Blantyre 3, Malawi
d
Department of Public and Environmental Health, Malawi University of Business and Applied Sciences, Private Bag 303, Chichiri, Blantyre 3, Malawi
e
Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow, UK
f
The School of Medicine, University of St. Andrews, St.Andrews KY16 9AJ, UK
g
Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, UK
HIGHLIGHTS GRAPHICAL ABSTRACT
•Potentially pathogenic bacteria are
recovered at all times of the year from
urban waste piles.
•Pathogen prevalence on waste materials
increases before the traditional season-
ally reported increase in community
cases.
•Environmentally recovered bacteria
encode resistance against multiple last-
resort antimicrobials.
•Pathogens bound to plastic pose a
heightened environmental and public
health risk.
ARTICLE INFO
Keywords:
Plastisphere
Antimicrobials
Human health
LMICs
Environmental health
ABSTRACT
Inadequate waste management and poor sanitation practices in Low- and Middle-Income Countries (LMICs) leads
to waste accumulation in urban and peri-urban residential areas. This increases human exposure to hazardous
waste, including plastics, which can harbour pathogenic bacteria. Although lab-based studies demonstrate how
plastic pollution can increase the persistence and dissemination of dangerous pathogens, empirical data on
pathogen association with plastic in real-world settings are limited. We conducted a year-long spatiotemporal
sampling survey in a densely populated informal settlement in Malawi, quantifying enteric bacterial pathogens
* Corresponding author.
E-mail address: Michael.ormsby1@stir.ac.uk (M.J. Ormsby).
1
These authors contributed equally
Contents lists available at ScienceDirect
Journal of Hazardous Materials
journal homepage: www.elsevier.com/locate/jhazmat
https://doi.org/10.1016/j.jhazmat.2024.136639
Received 19 September 2024; Received in revised form 15 November 2024; Accepted 22 November 2024
Journal of Hazardous Materials 484 (2025) 136639
Available online 26 November 2024
0304-3894/© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (
http://creativecommons.org/licenses/by/4.0/ ).
including ESBL-producing E. coli, Klebsiella pneumoniae, Salmonella spp., Shigella spp., and Vibrio cholerae.
Culture-based screening and molecular approaches were used to quantify the presence of each pathogen,
together with the distribution and frequency of resistance to antibiotics. Our data indicate that these pathogens
commonly associate with urban waste materials. Elevated levels of these pathogens precede typical infection
outbreaks, suggesting that urban waste piles may be an important source of community transmission. Notably,
many pathogens displayed increased levels of AMR, including against several ‘last resort’ antibiotics. These
ndings highlight urban waste piles as potential hotspots for the dissemination of infectious diseases and AMR
and underscores the need for urgent waste management interventions to mitigate public health risks.
1. Introduction
In Africa there has been a dramatic increase in plastic use, which
together with poor waste management infrastructure and resources, and
an inability to recycle or dispose of plastic waste adequately, has led to
the continent becoming an important source of plastic pollution [1].
With improvements in the standards of living and the adoption of a
‘single use’ economy, Africa produces almost 18 million tonnes of plastic
waste annually [2], with projections indicating that by 2060, Africa will
produce an estimated 116 million tonnes of plastic waste each year [3].
Although plastics in the environment are unsightly, plastic pollution can
also have substantial impacts on human health (e.g., [4-6]). Plastic is a
major constituent of urban waste piles in sub-Saharan Africa, which are
common in informal settlements ([7] in prep), and due to a lack of waste
management facilities and incentives for complying with environmental
regulations, communities living in slums and informal settlements are
particularly at risk of exposure to the negative effects of waste and
plastic pollution.
In urban areas, plastic pollutants, such as water bottles, sachets and
bags, often block drains and sewage channels and during heavy rains can
lead to localised ooding, increasing the transmission risk of waterborne
diseases such as cholera, and provide breeding grounds for medically
important mosquitoes [8,9]. There is now increasing evidence that
plastics in the environment can also act as a reservoir for human path-
ogenic bacteria, viruses, and fungi [10-12]. Microbial biolm associated
with the surface of plastics, known as the plastisphere, provides pro-
tection from environmental stressors such as temperature and UV,
facilitating the persistence of human pathogens and providing the po-
tential for further dissemination [13,14]. Importantly, pathogens colo-
nising plastic pollutants can retain, and even enhance, virulence
following their association with the plastisphere, highlighting the
inherent health risk associated with contaminated plastic waste in the
environment [14,15].
Sub-Saharan Africa has the highest mortality rate from bacterial
disease anywhere in the world, with 230 deaths per 100,000 population
[16]. Enteric pathogens transmitted via the faecal-oral route, such as
Salmonella spp., Escherichia coli, Klebsiella spp., Shigella spp. and Vibrio
cholerae, are responsible for substantial numbers of these infections; and
due to poor sanitation infrastructure, and high rates of open defecation,
are routinely introduced into the environment. Importantly, many
pathogenic bacteria now demonstrate resistance against ‘last resort’
antibiotics [17]. These critical drugs are used to treat severe infections
caused by multidrug-resistant (MDR) bacteria when other antibiotics
have failed and are often reserved for cases where conventional treat-
ments are ineffective due to high levels of resistance. It is estimated that
by 2050, almost 10 million deaths will be caused by anti-microbial
resistant (AMR) bacteria, making AMR a bigger global killer than can-
cer [18]. Africa is disproportionately affected by the rise in AMR due to
insufcient environmental health practices, poor household and
healthcare infrastructure, and misuse and overuse of antibiotics, which
all contribute to the transmission of AMR pathogens and a concomitant
higher risk of mortality from common infections that are now resistant
to standard treatments [19,20].
Rapidly increasing urbanisation in sub-Saharan Africa has increased
population density and the emergence of unplanned and informal
settlements in urban environments, which increases the pressure on
health, environmental, and waste management resources [19,21]. Here,
we have conducted a comprehensive year-long sampling survey of waste
piles in a densely populated informal settlement (Ndirande) in Blantyre,
Malawi, and quantied the presence of important enteric pathogens
colonising the surfaces of hard plastics (e.g., PET and HDPE) and soft
plastics (PE and LDPE), fabrics and organic material. Specically, we
aimed to: (1) quantify the temporal and geographic distribution of
pathogenic Salmonella spp., E. coli, Shigella spp., K. pneumoniae and
V. cholerae on waste materials in fourteen different urban waste piles;
and (2) quantify the level of resistance of these pathogens to commonly
used antibiotics.
2. Materials and methods
2.1. Location of sampling sites and temporal sample collection
This study was conducted in Ndirande township, an urban settlement
in Blantyre, Malawi (Fig. 1). Ndirande has a population of approxi-
mately 118,000 people (15 % of the total population in Blantyre). There
are no formal waste collection services in Ndirande which leads to open
dumping of domestic solid waste directly into the urban environment, or
on the banks of streams and rivers owing through the settlement.
Samples were collected monthly from 14 distinct waste piles (Fig. 1,
Table S1) between June 2022 and July 2023. Following heavy rain, four
waste piles (50, 52, 53 and 56; Fig. 1) were completely washed away,
meaning samples could not be collected from each waste pile at every
timepoint ([7], in prep).
2.2. Sample collection and processing
Samples of organic material (e.g., food waste and vegetation), fabric
(e.g., cotton, wool, linen), hard plastics (Polyethylene terephthalate
[PET] and high-density polyethylene [HDPE] [e.g., plastic bottles],
subsequently called P1), and soft plastics (Low-density polyethylene
[LDPE] and polyethylene [PE], e.g., plastic bags), subsequently called
P2) were collected from each waste pile in triplicate from randomly
allocated areas of the pile at (1) the surface and (2) 60 cm below the
surface where the waste had become more compacted. Samples were
placed in sterile collection bags, with a unique identifying barcode, and
transported back to the laboratory for immediate processing.
Enrichment or selective culture was carried out to isolate extended-
spectrum beta-lactamase (ESBL) producing E. coli and other ESBL-
producing Enterobacteriaceae (i.e., Klebsiella, Enterobacter and Cit-
robacter); Salmonella spp.; V. cholerae; and Shigella spp. Briey, each
piece of waste material was divided into three equal sections to permit
culture through three pathways, a general enrichment pathway for
Enterobacterales, a pathway enriching for Vibrio spp. and a pathway
selecting and enriching for Salmonellae. Accordingly, one section was
placed into buffered peptone water (BPW) and grown overnight at
37 ◦C; the second section was placed into alkaline peptone water (APW)
and grown for 6 h at 37 ◦C; and the third piece grown in bile broth
(modied Enterobacteriaceae Enrichment [EE broth; Neogen] with
0.2 g/L iron pyrophosphate [Oxoid]) at 37 ◦C for 24 h, and then in
selenite cysteine broth (Oxoid, UK) at 37 ◦C for a further 24 h [22].
M. Mphasa et al.
Journal of Hazardous Materials 484 (2025) 136639
2
Following enrichment in BPW, samples were plated onto ESBL CHRO-
Magar (24 h at 37 ◦C) for identication of ESBL producing E. coli (pink
colonies) and other Enterobacteriaceae (Klebsiella/Enterobacter/Ci-
trobacter; blue colonies), and onto Xylose Lysine Desoxycholate (XLD)
agar for putative identication of Shigella. Samples enriched in APW,
were plated onto Thiosulphate Citrate Bile Salts Sucrose (TCBS) agar
(24 h at 37 ◦C) to allow putative identication of V. cholerae (2–3 mm,
at, yellow colonies). The samples enriched in bile broth and selenite
cysteine broth, were plated onto mCASE agar for putative Salmonella
identication. These approaches will henceforth be referred to as ‘cul-
ture-based screening’.
2.3. qPCR conrmation of culture-based identication
An individual colony of each isolate putatively identied by culture
was picked and resuspended in 1 ml of nuclease-free water. The resul-
tant suspension was then heated to 95 ◦C for 15 min to fully denature
the DNA, which was subsequently used as a template for qPCR reactions
and molecular-based conrmation. Strain-specic genes were targeted
(primers listed in Table S2) for the identication of K. pneumoniae (khe),
Salmonella spp. (t tr ) Shigella spp. (ipaH) and toxigenic V. cholerae
(ctxA). A second PCR was performed (tviB) on positively identied Sal-
monella to determine whether they were Typhoidal or non-Typhoidal
strains. For amplication of K. pneumoniae specic genes, a Typeit 2X
HRM Master mix kit (Qiagen, UK) was used; and for amplication of
genes specic for Salmonella spp., Shigella spp., and V. cholerae, a LUNA
Universal qPCR Master Mix (New England Biolabs, UK) was used. In
both cases, the manufacturer’s instructions were followed. qPCR was
conducted in a QuantStudio 7 Flex PCR machine thermocycler. Due to
condence in the positive identication of E. coli on ESBL CHROMagar,
qPCR conrmation was not performed.
2.4. Determination of antimicrobial susceptibility and resistance
Antimicrobial resistance testing was performed using the Kirby-
Bauer disc diffusion assay. Briey, microbank stored isolates were sub-
cultured onto selective media (ESBL E. coli and K. pneumoniae on ESBL
Chromagar; Shigella spp. on XLD; Salmonella spp. on mCASE; and
V. cholerae on TCBS) and grown overnight at 37 ◦C. A colony of each was
then further sub-cultured onto nutrient agar and grown overnight at
37 ◦C to obtain pure colonies. Next, pure colonies were selected from the
nutrient agar, and resuspended in 5 ml sterile saline solution to obtain a
turbidity of 0.5 McFarland standard. Cells were then plated on Muller-
Hinton agar (Oxoid, UK). Discs (all Oxoid, UK) containing antibiotics
amikacin [AK30: 30 µg]; ampicillin [AMP2: 2 µg]; co-amoxiclav
[amoxicillin and clavulanic acid; AMX/CA30: 30 µg]; azithromycin
[AZM15: 15 µg]; cefoxitin [FOX30: 30 µg]; ceftazidime [CAZ10: 10 µg];
cefpodoxime (CEF10: 10 µg]; ciprooxacin [CIP5: 5 µg]; cotrimoxazole
[SXT25: 25 µg]; doxycycline [DO30: 30 µg]; meropenem [MEM10:
10 µg]; peoxacin [PEF5: 5 µg]; or tetracycline [TET30: 30 µg] were
placed onto the agar using a multidisc dispenser, and the plates incu-
bated at 37 ◦C for 24 h. Inhibition zones surrounding the discs were then
measured, and strains were categorised as ‘resistant’, ‘intermediate
resistance’, or ‘sensitive’ based on zones of inhibition (Table S3).
2.5. Statistical methods
All statistical analyses were conducted using Prism Software
(Version 10.3.2, GraphPad). P values ≤0.05 were considered signi-
cant. To determine differences in the temporal and geographic distri-
bution of pathogens putatively identied by the culture-based screen
and conrmed by molecular methods, a mixed-effects analysis with
Tukey multiple comparisons post-hoc test was performed. To determine
differences between pathogens putatively identied by culture-based
screen and conrmed by molecular methods, a two-way ANOVA with
Holm-ˇ
Síd´
ak multiple comparisons post-hoc test was performed.
3. Results
Between June 2022 and July 2023, samples of organic material
(n=128 surface; 140 compacted), fabric (n=129 surface; 140
compact), hard plastics (P1; n=130 surface; 139 compact), and soft
plastics (P2; n=130 surface; 139 compact) were collected from 14
distinct waste piles in Ndirande, Blantyre (Table S4), to examine the
temporal and geographic distribution of major enteric bacterial patho-
gens. The sampling period covered three distinct seasons, dened as the
‘cold and dry season’ between May and August; the ‘hot and dry season’
between September and November; and the ‘rainy season’ between
Fig. 1. : Location of urban waste piles. Fabric, organic material, and plastics were collected from urban waste piles (blue dots) in Ndirande urban settlement,
Blantyre, Malawi between June 2022 and July 2023. Each distinct waste pile was located by GPS (coordinates given in Table S1).
M. Mphasa et al.
Journal of Hazardous Materials 484 (2025) 136639
3
December and April (Fig. S1).
3.1. Temporal and spatial distribution of pathogens in waste piles
Through culture-based screening, no signicant differences were
observed in the recovery of putative Salmonella spp., Shigella spp., or
V. cholerae isolates between the rainy (Salmonella spp: 26; Shigella spp.:
45; V. cholerae: 192), cold and dry (Salmonella spp: 39; Shigella spp.: 41;
V. cholerae: 127), or hot and dry seasons (Salmonella spp: 25; Shigella
spp.: 37; V. cholerae: 147) (Fig. 2; Fig. S2). However, the recovery of
putatively identied V. cholerae isolates was greater during the rainy
season, and warmer periods. Signicantly more (P<0.05) E. coli and
other Enterobacteriaceae (Klebsiella, Citrobacter, and Enterobacter) were
recovered during the hot and dry season than the rainy season. Conr-
matory PCR analysis supported the culture-based screen observations,
with no signicant differences observed in the identication of Salmo-
nella spp., Shigella spp., or V. cholerae between any of the three dened
seasons (Fig. 2; Fig. S3). PCR conrmation indicated that recovery of
K. pneumoniae was signicantly higher (P<0.05) during the hot and dry
season (97 isolates) than the rainy season (50 isolates), suggesting that
the Enterobacteriaceae culture screen is proportionally representative of
K. pneumoniae. Molecular examination revealed that all conrmed Sal-
monella spp. isolates were non-typhoidal.
ESBL E. coli, Salmonella spp., Shigella spp., V. cholerae, and ESBL
Enterobacteriaceae were recovered at every waste pile examined
(Fig. S2). However, the culture-based screening approach demonstrated
no correlation between any of the target pathogens and the waste pile
location, indicating no obvious spatial pattern within the settlement.
Due to extreme weather events during the rainy season, waste piles 50,
52, 53, 54, 55, and 56 were completely washed away in December 2022,
meaning that there is an incomplete temporal dataset for these waste
piles.
Culture-based screening approaches putatively identied more
target pathogens than via PCR (Table S5; Fig. S4); however, molecular
conrmation gives a more detailed and condent identication. PCR
conrmation of Salmonella spp. isolates suggested a degree of
geographic distribution, with all isolates recovered from waste piles 55
and 56, however as several waste piles, including waste pile 56 were
washed away, the dataset is incomplete. The number of positively
identied isolates of Shigella spp., and toxigenic V. cholerae was too small
to condently correlate spatial distribution. PCR of candidate
K. pneumoniae isolates conrmed they was present at each waste pile,
although with no clear geographic distribution. Molecular conrmation
was not conducted for ESBL E. coli due to the stringency and condence
in the culture-based screen for this pathogen based on genomic studies
of pink isolates from ESBL-chrome in this setting [23]. There were no
signicant differences in the numbers of target pathogens isolated from
the different types of material (Fig. S5).
3.2. Antimicrobial resistance proles of waste-pile-associated pathogens
All isolates conrmed by PCR were screened against clinically rele-
vant antimicrobials. In all cases, there were no signicant differences in
resistance proles of isolates recovered from different waste materials,
nor depending on whether the material came from the surface or the
compacted portion of the waste pile (Fig. 3). Most Salmonella (6/14),
Shigella (9/14), and V. cholerae (2/3) isolates were sensitive to all anti-
biotics tested. Resistance was observed in Salmonella isolates against
cefoxitin (5/14) and peoxacin (2/14); in Shigella isolates against
cefoxitin (8/14), cefpodoxime (9/14), ampicillin (5/14) and cotrimox-
azole (10/14); and in V. cholerae isolates against amoxicillin (1/3),
ampicillin (1/3), doxycycline (1/3) and tetracycline (1/3). Out of the
346 E. coli isolates, 177 (51 %) were resistant, or showed intermediate
(64; 18.4 %) levels of resistance, against at least one antibiotic. Ninety-
six percent of all ESBL E. coli isolates were resistant to peoxacin, and
83.8 % resistant to cotrimoxazole. One hundred percent of all ESBL
E. coli isolates were resistant (70.2 %) or showed intermediate resistance
(29.8 %) against ceftazidime. Out of the 242 K. pneumoniae isolates, 150
(62 %) were resistant or showed intermediate (50; 20.8 %) levels of
resistance against at least one antibiotic. Almost 98 % of all
K. pneumoniae isolates were resistant to peoxacin, and 98.7 % resistant
to cotrimoxazole. K. pneumoniae isolates also showed high levels of
resistance against ceftazidime (69.8 %); cefoxitin (48.7 %); and mer-
openem (35.9 %).
4. Discussion
Urban waste piles in informal settlements can represent a consider-
able reservoir for pathogenic and multidrug-resistant (MDR) human
pathogenic bacteria. Potentially dangerous bacterial pathogens were
identied on all materials (including organic material, fabrics, and
plastics) recovered from waste piles, and at all times of the year,
increasing the likelihood of interaction between humans and pathogens
and the subsequent human health risk. Importantly, many of the path-
ogens recovered from these waste piles showed resistance against
several of the so-called ‘last resort’ antibiotics (i.e. Klebsiella to mer-
openem). Taken together, this study emphasises the considerable haz-
ards associated with environmental waste and accentuates the urgent
need for mitigation and intervention strategies directed towards plastic
and other waste materials, particularly in low- and middle-income
countries (LMICs) such as Africa.
In LMICs, incidences of infection by pathogenic bacteria often
correlate with warmer temperatures and periods of heavy rain, which
provide conducive growth conditions for bacterial enteric pathogens in
the environment with greater opportunities for dissemination through
irrigation, run-off, and ooding [24,25]. In Malawi, where the warmest
daily temperatures are in September and October, and the heaviest rains
fall between November and April [26], infections caused by Shigella,
E. coli, Salmonella, and V. cholerae are most frequent ([19,27-29]). While
Klebsiella is responsible for many infections in Malawi, particularly
associated with healthcare settings [30,31], there is limited temporal
data available indicating prevalence correlating with a particular sea-
son. In other global settings however, infections caused by Klebsiella are
often more frequent during warmer and more humid periods [32,33].
Recently, it has been shown that pathogens including ESBL E. coli and
K. pneumoniae frequently contaminate drains, standing water and soil,
and that their abundance correlates with increased urbanisation and
rainfall [34]. Our study has demonstrated that in informal settlements,
the materials commonly found in waste piles are also frequently
contaminated with these pathogens and clearly represent a potential
exposure route for people living in close proximity to them. This risk is
particularly heightened for informal waste pickers who regularly come
into direct contact with these waste piles, as well as for residents using
nearby rivers for domestic purposes, where waste accumulation along
the banks increases the likelihood of exposure to harmful pathogens
[35].
ESBL E. coli and K. pneumoniae were recovered most frequently from
waste piles during the hot and dry season (Sept-Nov). Seasonality can
inuence the levels of infection with ESBL E. coli and K. pneumoniae in
the population, with a decrease in infection prevalence during the colder
season followed by an increase during the warmer, rainier months [36,
37] However, our data suggests that the increase in abundance of ESBL
E. coli and K. pneumoniae in the environment likely precedes infections in
the community, with continued environmental persistence observed
throughout the typical infectious ‘season’. This implies that as envi-
ronmental conditions become warmer and more favourable for bacterial
growth, isolates of ESBL E. coli and K. pneumoniae associating with waste
materials in the environment, transition from biolm-associated,
dormant lifestyles, to more infectious, transmissible lifestyles.
Higher temperatures enhance metabolic processes in bacteria, with
enzymes involved in degrading the extracellular biolm matrix and
those necessary for cell division and metabolism becoming more active,
M. Mphasa et al.
Journal of Hazardous Materials 484 (2025) 136639
4
Fig. 2. : Culture-based screening and PCR conrmation of target pathogenic bacteria in 14 urban dumpsites over one year. Each square in the heat map is
representative of the combined number of isolates recovered from samples of either fabric (F); organic material (O); hard plastics (P1), (e.g., PET and HDPE); and soft
plastics (P2) (e.g., PE and LDPE) from 14 different waste piles. PCR of “Other Enterobacteriaceae” was used to conrm whether blue colonies growing on ESBL-
chrome were ESBL K. pneumoniae; and PCR conrmation of V. cholerae isolates was conrmatory of toxigenic V. cholerae. E. coli isolates were conrmed by
culture-based methods only.
M. Mphasa et al.
Journal of Hazardous Materials 484 (2025) 136639
5
allowing bacteria to resume active division and growth [38,39]. Envi-
ronmental factors such as increasing temperature [40], can promote
biolm dissociation and dispersal in several bacterial species, together
with a concomitant upregulation of virulence genes indicating that
biolm dispersal can be a critical step for increasing bacterial virulence
[41,42]. The abundance of ESBL E. coli and K. pneumoniae recovered
from materials in waste piles increased in the periods preceding the
traditional infectious period, suggesting that an increase in temperature
could be a critical step in the resuscitation of these pathogens before the
increased rainfall promotes their dissemination into the environment.
Therefore, continuous environmental monitoring of pathogens (e.g., in
urban waste piles) could be used as a surveillance tool to predict likely
increases in community infections.
The low abundance of Salmonella spp., Shigella spp., and toxigenic
V. cholerae found was possibly due to an inability to associate with the
examined materials, however, in vitro studies have indicated that this is
unlikely [13,15]. The lack of recovery was likely inuenced by some
species entering a viable but non-culturable (VBNC) state in the envi-
ronment. The VBNC state allows bacteria to remain alive, metabolically
active, and even able to acquire and spread genetic material; however,
they cannot be cultured using standard laboratory techniques [43]. This
allows bacteria to survive adverse environmental conditions including
temperature extremes, nutrient limitations, and exposure to chemicals
while waiting for more favourable conditions for proliferation. E. coli,
Salmonella spp., Shigella spp., and Klebsiella spp. are all capable of
entering a VBNC state in environmental settings [44-47]; however, the
most well-studied organism in this context, is V. cholerae. Research has
indicated that V. cholerae can transition to a VBNC state on plastics
under simulated environmental conditions, before resuscitation to in-
fectious levels [15]. Therefore, the culture-based screening approach in
this study likely underestimated the abundance of these pathogens in the
environment. Malawi has recently experienced one of its worst cholera
outbreaks, with over 59,000 reported cases and approximately 1770
deaths as of January 2024, and isolation of the aetiologic agent from
plastic waste piles is of considerable concern [48].
Enteric pathogens are associated with poor sanitation infrastructure
and waste management, and a lack of healthcare provision, all of which
are characteristic of informal settlements, and are further amplied in
densely populated areas. Our study site encompassed 14 distinct urban
waste piles, all contained within a single densely populated informal
settlement (Ndirande) along a single river (the Nasolo), with many
different households contributing to the same waste pile. The intestinal
Fig. 3. AMR proles of bacterial isolates recovered from urban waste piles. Sensitivity, intermediate resistance, and resistance were calculated using a Kirby-Bauer
disc diffusion assay on isolates positively identied by PCR. Susceptibility was examined against amikacin [AK30: 30 µg]; ampicillin [AMP2: 2 µg]; coamoxiclav
[amoxicillin and clavulanic acid; AMX/CA30: 30 µg]; azithromycin [AZM15: 15 µg]; cefoxitin [FOX30: 30 µg]; ceftazidime [CAZ10: 10 µg]; ciprooxacin [CIP5:
5µg]; cefpodoxime (CEF10: 10 µg]; cotrimoxazole [SXT25: 25 µg]; doxycycline [DO30: 30 µg]; meropenem [MEM10: 10 µg]; peoxacin [PEF5: 5 µg]; or tetracycline
[TET30: 30 µg] and resistance determined according to inhibition zones as detailed in Table S3. Note different scales on the y axes.
M. Mphasa et al.
Journal of Hazardous Materials 484 (2025) 136639
6
microbiome of communities living in close proximity to each other is
shaped by a combination of dietary practices, environmental exposures,
social behaviours, and genetic factors, which contribute to a shared
microbiome [49]. Consequently, it is likely that the composition of in-
testinal microora, together with associated pathogen carriage and
shedding, is widely shared and spread within specic communities in
Ndirande, a process that could be further exacerbated by exposure to
shared waste piles and this warrants further investigation.
While no signicant differences were observed in the association of
each pathogen with different material types in this study, the association
of pathogens with plastic waste has important implications for pathogen
survival, dissemination, and for human health. Plastics are durable and
highly recalcitrant materials, able to withstand degradation from envi-
ronmental factors including sunlight, water, and biological processes
[50]. While organic materials can persist for up to six weeks and fabrics
for up to ve months, soft plastic polymers, such as LDPE, can persist for
up to 20 years, while hard plastic polymers such as HDPE, can persist for
considerably longer [50,51]. The lightweight and buoyant properties of
plastics compared to organic material and fabrics, increases the poten-
tial for environmental dissemination of pathogens colonising the surface
of plastics. This was particularly highlighted when extreme weather
events (e.g., cyclone ‘Freddy’ in March 2023) disrupted and dispersed
several of the waste piles in this study, with wide dissemination of the
waste pile components around the settlement and to downstream re-
ceptors. In informal settlements, enteric pathogens, which are primarily
faecal-orally transmitted, frequently enter urban waste piles through
open defaecation and via soiled single-use diapers, which are becoming
more common in LMICs [52,53]. The subsequent mixing of human
faeces with waste materials provides opportunity for interactions be-
tween enteric bacterial pathogens and materials, which once on the
surfaces of plastics can persist and retain their virulence even after pe-
riods of environmental stress such as desiccation, high and low tem-
peratures, and ultraviolet (UV) radiation [11,15,54].
It is common for wild and domestic animals, e.g., ies, rodents, birds,
and dogs, to interact with waste piles in urban settlements [4], which
increases the opportunity for human pathogens to be transported by
animals but also for animal faeces to further contaminate waste piles. In
turn, this heightens the potential for wider dissemination within the
community, with the additional infection risk from the spread of zoo-
notic pathogens [55]. Human pathogens in waste piles will encounter
uctuations in temperature and pH, which may facilitate the rapid
adaption to the animal digestive tract and increase the likelihood of the
evolution of novel zoonoses [56]. Future work needs to examine both
veterinary and zoonotic pathogens on urban waste piles, to more fully
ascertain the risk of waste piles acting as hotspots for pathogen emer-
gence and dispersal. While this study has focused on major enteric
bacterial pathogens, there are many other bacterial, viral, and eukary-
otic pathogens responsible for infections in sub-Saharan Africa, although
how these pathogens interact with waste materials, including plastics, is
still not clear [57,58].
Although our broader culture-based screening approach commonly
revealed putative isolates of Salmonella spp., Shigella spp., V. cholerae,
ESBL E. coli, and ESBL Enterobacteriaceae (Klebsiella, Citrobacter or
Enterobacter) colonising waste materials in urban waste piles, more
targeted PCR indicated that only a small portion of the V. cholerae iso-
lates were toxigenic (encoding cholera toxin gene ctx), and that all the
Salmonella spp. were non-Typhoidal. However, many of these “non-
pathogenic” isolates may also contain AMR genes with the potential for
acquisition by pathogenic variants. Biolms, including the plastisphere,
are recognised hotspots for the exchange of genetic material and hori-
zontal gene transfer (HGT) [59]. Biolm offers greater opportunities for
inter- and intra-species interaction, with a high frequency of plasmid
transfer between bacteria in the plastisphere [60]. Biolms on plastic
debris can also concentrate antibiotics, which can further promote the
development of AMR bacteria [61,62]. Importantly, all ESBL E. coli
isolates recovered from materials in waste piles were resistant or showed
intermediate resistance against the so-called ‘last resort’ antibiotic cef-
tazidime, and large numbers of K. pneumoniae isolates showed high
levels of resistance against ceftazidime (69.8%) and meropenem
(35.9%). Meropenem resistance is being observed with increasing fre-
quency globally and is of major clinical concern in healthcare settings
[63].
5. Conclusions
Urban waste piles are a reservoir of potentially pathogenic bacteria,
and waste materials such as plastic, can pose a threat to public health by
providing protection from harsh environmental conditions and facili-
tating pathogen replication and dissemination. Enteric human patho-
gens were associated with urban waste piles throughout the year, which
increases the opportunities for people to be exposed to them. Impor-
tantly, many of these pathogens encode multi-drug resistance against
last-resort antibiotics, which has serious ramications for human health
in the wider context of global AMR. The lack of waste management
systems highlights the disproportionate burden faced by communities
living in informal settlements. The potential for urban waste piles to act
as hotspots for disseminating potentially pathogenic organisms further
reinforces the urgent need for mitigation and intervention strategies to
tackle environmental waste and the associated human health risks. This
underscores the principles of One Health, emphasising the intercon-
nectedness of human, animal, and environmental health, where un-
managed waste threatens not only human populations but also the
broader ecosystem, potentially leading to zoonotic disease transmission
and further exacerbating global health challenges.
Environmental implications
Plastic waste could play a critical, but as yet unrecognised, role in
both the spread of infectious diseases and the amplication of antimi-
crobial resistance in urban environments. The persistence and distri-
bution of plastic contamination increases the risk of direct human
exposure. This study provides novel, real-world data on the association
with and persistence of multiple enteric bacterial pathogens associated
with plastics and other urban waste materials. These results have global
signicance, as plastic pollution becomes more pervasive, and climate
change is altering the behaviour of enteric pathogens in the environ-
ment. This highlights an urgent need for public health interventions
targeting waste management and sanitation in LMICs, with a focus on
reducing plastic waste to mitigate associated health risks. Comprehen-
sive management strategies could greatly reduce the burden of disease
and curb the spread of AMR.
Funding
This work was supported by the UKRI Natural Environment Research
Council (NERC) as part of the GCRF SPACES project [grant number NE/
V005847/1] and the NERC Plastic Vectors project, “Microbial hitch-
hikers of marine plastics: the survival, persistence & ecology of micro-
bial communities in the ‘Plastisphere’” [grant number NE/S005196/1].
Ethical statement
A waiver for the work in the study was granted by the Kamuzu
University of Health Sciences College of Medicine Research Ethics
Committee (COMREC P.07/20/3089). Permission to sample the envi-
ronment was also obtained from the Blantyre City Council who are
responsible for waste management in Blantyre City including the study
area. Community engagement in conducting the research was under-
taken with community leaders through the Group Village Headmen
(GVH).
M. Mphasa et al.
Journal of Hazardous Materials 484 (2025) 136639
7
CRediT authorship contribution statement
Nicholas Feasey: Writing – review & editing, Supervision, Meth-
odology, Conceptualization. Tracy Morse: Writing – review & editing,
Supervision. Richard S. Quilliam: Writing – review & editing, Super-
vision, Project administration, Methodology, Funding acquisition,
Conceptualization. Peter Nambala: Writing – review & editing, Su-
pervision. Taonga Mwapasa: Writing – review & editing, Methodology.
Kondwani Chidziwisano: Writing – review & editing, Methodology.
Madalitso Mphasa: Writing – review & editing, Writing – original draft,
Methodology, Formal analysis, Data curation, Conceptualization.
Michael J. Ormsby: Writing – review & editing, Writing – original
draft, Visualization, Methodology, Formal analysis, Data curation,
Conceptualization.
Declaration of Competing Interest
The authors declare that they have no known competing nancial
interests or personal relationships that could have appeared to inuence
the work reported in this paper.
Appendix A. Supporting information
Supplementary data associated with this article can be found in the
online version at doi:10.1016/j.jhazmat.2024.136639.
Data availability
Data will be made available on request.
References
[1] Shomuyiwa, D.O., Onukansi, F.O., Ivanova, M., Lucero-Prisno, D.E., 2023. The
plastic treaty: what is in it for Africa? Public Health Chall 2 (2). https://doi.org/
10.1002/puh2.83.
[2] Sadan, Z. and De Kock, L. 2022. Plastic Pollution in Africa: Identifying policy gaps
and opportunities. Cape Town, South Africa.
[3] OECD. 2022. Global Plastics Outlook: Plastics use projections to 2060. Paris: OECD.
doi: 10.1787/aa1edf33-en.
[4] Krystosik, A., Njoroge, G., Odhiambo, L., Forsyth, J.E., Mutuku, F., LaBeaud, A.D.,
2020. Solid wastes provide breeding sites, burrows, and food for biological disease
vectors, and urban zoonotic reservoirs: a call to action for solutions-based research.
Front Public Health 7. https://doi.org/10.3389/fpubh.2019.00405.
[5] Wu, D., et al., 2021. Commodity plastic burning as a source of inhaled toxic
aerosols. J Hazard Mater 416, 125820. https://doi.org/10.1016/j.
jhazmat.2021.125820.
[6] Wang, X., Firouzkouhi, H., Chow, J.C., Watson, J.G., Carter, W., De Vos, 2023.
Characterization of gas and particle emissions from open burning of household
solid waste from South Africa. Atmospheric Chemistry and Physics 23 (15),
8921–8937. https://doi.org/10.5194/acp-23-8921-2023.
[7] Mwapasa, T., et al., 2024. Key environmental exposure pathways to antimicrobial
resistant bacteria in southern Malawi: a saniPath approach. Sci Total Environ 945,
174142. https://doi.org/10.1016/j.scitotenv.2024.174142.
[8] Maquart, P.-O., Froehlich, Y., Boyer, S., 2022. Plastic pollution and infectious
diseases. Lancet Planet Health 6 (10), e842–e845. https://doi.org/10.1016/S2542-
5196(22)00198-X.
[9] Stoler, J., 2017. From curiosity to commodity: a review of the evolution of sachet
drinking water in West Africa. WIREs Water 4 (3). https://doi.org/10.1002/
wat2.1206.
[10] Gkoutselis, G., Rohrbach, S., Harjes, J., Obst, M., Brachmann, A., Horn, M.A., et al.,
2021. Microplastics accumulate fungal pathogens in terrestrial ecosystems. Sci Rep
11 (1), 13214. Available at: /pmc/articles/PMC8282651/ [Accessed: 26 July
2022].
[11] Metcalf, R., White, H.L., Moresco, V., Ormsby, M.J., Oliver, D.M., Quilliam, R.S.,
2022. Sewage-associated plastic waste washed up on beaches can act as a reservoir
for faecal bacteria, potential human pathogens, and genes for antimicrobial
resistance. Mar Pollut Bull 180, 113766. https://doi.org/10.1016/J.
MARPOLBUL.2022.113766.
[12] Moresco, V., Charatzidou, A., Oliver, D.M., Weidmann, M., Matallana-Surget, S.,
Quilliam, R.S., 2022. Binding, recovery, and infectiousness of enveloped and non-
enveloped viruses associated with plastic pollution in surface water. Environ Pollut
308, 119594. https://doi.org/10.1016/J.ENVPOL.2022.119594.
[13] Ormsby, M.J., White, H.L., Metcalf, R., Oliver, D.M., Feasey, N.A., Quilliam, R.S.,
2024. Enduring pathogenicity of African strains of Salmonella on plastics and glass
in simulated peri-urban environmental waste piles. J Hazard Mater 461. https://
doi.org/10.1016/j.jhazmat.2023.132439.
[14] Ormsby, M.J., Woodford, L., White, H.L., Fellows, R., Quilliam, R.S., 2024. The
plastisphere can protect salmonella typhimurium from UV stress under simulated
environmental conditions. Environ Pollut 358, 124464. https://doi.org/10.1016/j.
envpol.2024.124464.
[15] Ormsby, M.J., Woodford, L., White, H.L., Fellows, R., Oliver, D.M., Quilliam, R.S.,
2024. Toxigenic Vibrio cholerae can cycle between environmental plastic waste
and oodwater: implications for environmental management of cholera. J Hazard
Mater 461, 132492. https://doi.org/10.1016/J.JHAZMAT.2023.132492.
[16] Ikuta, S, K., et al., 2022. Global mortality associated with 33 bacterial pathogens in
2019: a systematic analysis for the global burden of disease study 2019. Lancet 400
(10369), 2221–2248. https://doi.org/10.1016/S0140-6736(22)02185-7.
[17] Sharma, E., Chen, Y., Kelso, C., Sivakumar, M., Jiang, G., 2024. Navigating the
environmental impacts and analytical methods of last-resort antibiotics: colistin
and carbapenems. Soil Environ Health 2 (1), 100058. https://doi.org/10.1016/j.
seh.2024.100058.
[18] Murray, C.J.L., et al., 2022. Global burden of bacterial antimicrobial resistance in
2019: a systematic analysis. Lancet 399 (10325), 629–655. https://doi.org/
10.1016/S0140-6736(21)02724-0.
[19] Cocker, D., et al., 2023. Investigating one health risks for human colonisation with
extended spectrum β-lactamase-producing Escherichia coli and Klebsiella
pneumoniae in Malawian households: a longitudinal cohort study. Lancet Microbe
4 (7), e534–e543. https://doi.org/10.1016/S2666-5247(23)00062-9.
[20] Sartorius, B., et al., 2024. The burden of bacterial antimicrobial resistance in the
WHO African region in 2019: a cross-country systematic analysis. Lancet Glob
Health 12 (2), e201–e216. https://doi.org/10.1016/S2214-109X(23)00539-9.
[21] Nadimpalli, M.L., et al., 2020. Urban informal settlements as hotspots of
antimicrobial resistance and the need to curb environmental transmission. Nat
Microbiol 5 (6), 787–795. https://doi.org/10.1038/s41564-020-0722-0.
[22] Rigby, J., et al., 2022. Optimized methods for detecting salmonella typhi in the
environment using validated eld sampling, culture and conrmatory molecular
approaches. J Appl Microbiol 132 (2), 1503–1517. https://doi.org/10.1111/
jam.15237.
[23] Lewis, J.M., et al., 2023. Genomic analysis of extended-spectrum beta-lactamase
(ESBL) producing Escherichia coli colonising adults in Blantyre, Malawi reveals
previously undescribed diversity. Microb Genom 9 (6). https://doi.org/10.1099/
mgen.0.001035.
[24] Asadgol, Z., Mohammadi, H., Kermani, M., Badirzadeh, A., Gholami, M., 2019. The
effect of climate change on cholera disease: the road ahead using articial neural
network. PLOS ONE 14 (11), e0224813. https://doi.org/10.1371/journal.
pone.0224813.
[25] Schwab, F., Gastmeier, P., Meyer, E., 2014. The warmer the weather, the more
gram-negative bacteria - impact of temperature on clinical isolates in intensive care
units. PloS One 9 (3), e91105. https://doi.org/10.1371/journal.pone.0091105.
[26] Malawi Meteorological Services 2024. Department of Climate Change and
Meteorological Services, Malawi.
[27] Miggo, M., et al., 2023. Fight against cholera outbreak, efforts and challenges in
Malawi. Health Sci Rep 6 (10), e1594. https://doi.org/10.1002/hsr2.1594.
[28] Ndungo, E., et al., 2022. Dynamics of the gut microbiome in shigella-infected
children during the rst two years of life. mSystems 7 (5), e0044222. https://doi.
org/10.1128/msystems.00442-22.
[29] Wilson, C.N., et al., 2022. Incidence of invasive non-typhoidal salmonella in
Blantyre, Malawi between January 2011-December 2019. Wellcome Open Res 7,
143. https://doi.org/10.12688/wellcomeopenres.17754.1.
[30] Heinz, E., et al., 2024. Longitudinal analysis within one hospital in sub-Saharan
Africa over 20 years reveals repeated replacements of dominant clones of Klebsiella
pneumoniae and stresses the importance to include temporal patterns for vaccine
design considerations. Genome Med 16 (1), 67. https://doi.org/10.1186/s13073-
024-01342-3.
[31] Lester, R., et al., 2022. Effect of resistance to third-generation cephalosporins on
morbidity and mortality from bloodstream infections in Blantyre, Malawi: a
prospective cohort study. Lancet Microbe 3 (12), e922–e930. https://doi.org/
10.1016/S2666-5247(22)00282-8.
[32] Anderson, D.J., et al., 2008. Seasonal variation in Klebsiella pneumoniae
bloodstream infection on 4 continents. J Infect Dis 197 (5), 752–756. https://doi.
org/10.1086/527486.
[33] Kito, Y., et al., 2022. Seasonal variation in the prevalence of gram-negative bacilli
in sputum and urine specimens from outpatients and inpatients. Fujita Med J 8 (2),
46–51. https://doi.org/10.20407/fmj.2021-003.
[34] Mwapasa, T. , Robertson, T. , Kazembe, D. , Mnkhwama, A. , Kalonde, P. , Feasey,
N. , , and et al. 2024b. Mapping and quantifying plastic pollution in informal
settlements of Urban Malawi. In prep.
[35] Adams, E.A., Byrns, S., Kumwenda, S., Quilliam, R., Mkandawire, T., Price, H.,
2022. Water journeys: household water insecurity, health risks, and embodiment in
slums and informal settlements. Soc Sci Med 313, 115394.
[36] Lewis, J.M., et al., 2022. Colonization dynamics of extended-spectrum beta-
lactamase-producing enterobacterales in the gut of Malawian adults. Nat Microbiol
7 (10), 1593–1604. https://doi.org/10.1038/s41564-022-01216-7.
[37] Sammarro, M., et al., 2023. Risk factors, temporal dependence, and seasonality of
human extended-spectrum β-lactamases-producing Escherichia coli and Klebsiella
pneumoniae colonization in Malawi: a longitudinal model-based approach. Clin
Infect Dis 77 (1), 1–8. https://doi.org/10.1093/cid/ciad117.
[38] Ortiz-Cort´
es, L.Y., Ventura-Canseco, L.M.C., Abud-Archila, M., Ruíz-Valdiviezo, V.
M., Vel´
azquez-Ríos, I.O., Alvarez-Guti´
errez, P.E., 2021. Evaluation of temperature,
pH and nutrient conditions in bacterial growth and extracellular hydrolytic
activities of two Alicyclobacillus spp. strains. Arch Microbiol 203 (7), 4557–4570.
Available at: 〈https://link.springer.com/article/10.1007/s00203-021-02332-4〉.
M. Mphasa et al.
Journal of Hazardous Materials 484 (2025) 136639
8
[39] Scoeld, V., Jacques, S.M.S., Guimar˜
aes, J.R.D., Farjalla, V.F., 2015. Potential
changes in bacterial metabolism associated with increased water temperature and
nutrient inputs in tropical humic lagoons. Front Microbiol 6, 310. https://doi.org/
10.3389/fmicb.2015.00310.
[40] Guilhen, C., Forestier, C., Balestrino, D., 2017. Biolm dispersal: multiple elaborate
strategies for dissemination of bacteria with unique properties. Mol Microbiol 105
(2), 188–210. https://doi.org/10.1111/mmi.13698.
[41] Elpers, L., Deiwick, J., Hensel, M., 2022. Effect of environmental temperatures on
proteome composition of Salmonella enterica serovar typhimurium. Mol Cell
Proteom 21 (8), 100265. https://doi.org/10.1016/j.mcpro.2022.100265.
[42] Poimenidou, S.V., Caccia, N., Paramithiotis, S., H´
ebraud, M., Nychas, G.-J.,
Skandamis, P.N., 2023. Inuence of temperature on regulation of key virulence
and stress response genes in Listeria monocytogenes biolms. Food Microbiol 111,
104190. https://doi.org/10.1016/j.fm.2022.104190.
[43] Ramamurthy, T., Ghosh, A., Pazhani, G.P., Shinoda, S., 2014. Current perspectives
on viable but non-culturable (VBNC) pathogenic bacteria. Front Public Health 2
(JUL), 91118. Available at: www.frontiersin.org [Accessed: 1 August 2024].
[44] Centeleghe, I., Norville, P., Hughes, L., Maillard, J.Y., 2023. Klebsiella pneumoniae
survives on surfaces as a dry biolm. Am J Infect Control 51 (10), 1157–1162.
https://doi.org/10.1016/J.AJIC.2023.02.009.
[45] Jayeola, V., Farber, J.M., Kathariou, S., 2022. Induction of the viable-but-
nonculturable state in Salmonella contaminating dried fruit. Appl Environ
Microbiol 88 (2). Available at: 〈https://pubmed.ncbi.nlm.nih.gov/34731057/〉.
[46] Trevors, J.T., 2011. Viable but non-culturable (VBNC) bacteria: gene expression in
planktonic and biolm cells. J Microbiol Methods 86 (2), 266–273 (Available at)
〈https://linkinghub.elsevier.com/retrieve/pii/S0167701211001667〉.
[47] Ye, C., Lin, H., Zhang, M., Chen, S. and Yu, X. 2020. Characterization and Potential
Mechanisms of Highly Antibiotic Tolerant VBNC Escherichia coli Induced by Low
Level Chlorination. Scientic Reports 2020 10:1 10(1), pp. 1–11. Available at: 〈htt
ps://www.nature.com/articles/s41598–020-58106–3〉[Accessed: 1 August 2024].
[48] CDC. 2024. Cholera Response in Malawi.
[49] Dill-McFarland, K.A. et al. 2019. Close social relationships correlate with human
gut microbiota composition. Scientic Reports 2019 9:1 9(1), pp. 1–10. Available
at: https://www.nature.com/articles/s41598–018-37298–9 [Accessed: 1 August
2024].
[50] Chamas, A., et al., 2020. Degradation rates of plastics in the environment. ACS
Sustain Chem Eng 8 (9), 3494–3511 (Available at) 〈https://pubs.acs.org/d
oi/full/10.1021/acssuschemeng.9b06635〉.
[51] Zhang, K., Hamidian, A.H., Tubi´
c, A., Zhang, Y., Fang, J.K.H., Wu, C., et al., 2021.
Understanding plastic degradation and microplastic formation in the environment:
A review. Environ Pollut 274, 116554. https://doi.org/10.1016/j.
envpol.2021.116554.
[52] Kretchy, J.P., Dzodzomenyo, M., Ayi, I., Dwomoh, D., Agyabeng, K., Konradsen, F.,
et al., 2020. Risk of faecal pollution among waste handlers in a resource-deprived
coastal peri-urban settlement in Southern Ghana. PLoS ONE 15 (10). Available at:
/pmc/articles/PMC7531843/ [Accessed: 1 December 2022.
[53] White, H.L., et al., 2023. Open defaecation by proxy: tackling the increase of
disposable diapers in waste piles in informal settlements. Int J Hyg Environ Health
250. https://doi.org/10.1016/j.ijheh.2023.114171.
[54] Woodford, L., Fellows, R., White, H.L., Ormsby, M.J., Pow, C.J. and Quilliam, R.S.
2024a. Survival and Transfer Potential of Salmonella enterica Serovar
Typhimurium Colonising Polyethylene Microplastics in Contaminated Agricultural
Soil. Environmental Science and Pollution Research.
[55] Wierucka, K., et al., 2023. Human-wildlife interactions in urban Asia. Glob Ecol
Conserv 46, e02596. https://doi.org/10.1016/j.gecco.2023.e02596.
[56] Ormsby, M.J., Woodford, L., Quilliam, R.S., 2024. Can plastic pollution drive the
emergence and dissemination of novel zoonotic diseases? Environ Res 246,
118172. https://doi.org/10.1016/j.envres.2024.118172.
[57] Gerba, C.P., 2020. Microbial pathogens in municipal solid waste. In: Microbiology
of Solid Waste. CRC Press,, pp. 155–174. https://doi.org/10.1201/
9780138747268-5.
[58] Ormsby, M.J., Akinbobola, A., Quilliam, R.S., 2023. Plastic pollution and fungal,
protozoan, and helminth pathogens – a neglected environmental and public health
issue? Sci Total Environ 882. https://doi.org/10.1016/J.
SCITOTENV.2023.163093.
[59] Zhu, D., Ma, J., Li, G., Rillig, M.C., Zhu, Y.-G., 2022. Soil plastispheres as hotpots of
antibiotic resistance genes and potential pathogens. ISME J 16 (2), 521–532.
https://doi.org/10.1038/s41396-021-01103-9.
[60] Arias-Andres, M., Klümper, U., Rojas-Jimenez, K., Grossart, H.P., 2018.
Microplastic pollution increases gene exchange in aquatic ecosystems. Environ
Pollut 237, 253–261. https://doi.org/10.1016/J.ENVPOL.2018.02.058.
[61] Liu, Y., Liu, W., Yang, X., Wang, J., Lin, H., Yang, Y., 2021. Microplastics are a
hotspot for antibiotic resistance genes: progress and perspective. Sci Total Environ
773, 145643. https://doi.org/10.1016/j.scitotenv.2021.145643.
[62] Murray, A.K., Zhang, L., Snape, J., Gaze, W.H., 2019. Comparing the selective and
co-selective effects of different antimicrobials in bacterial communities. Int J
Antimicrob Agents 53 (6), 767–773. https://doi.org/10.1016/j.
ijantimicag.2019.03.001.
[63] Wise, M.G., et al., 2024. Global trends in carbapenem- and difcult-to-treat-
resistance among World Health Organization priority bacterial pathogens: ATLAS
surveillance program 2018–2022. J Glob Antimicrob Resist 37, 168–175. https://
doi.org/10.1016/j.jgar.2024.03.020.
M. Mphasa et al.
Journal of Hazardous Materials 484 (2025) 136639
9