Antibacterial activity of avocado extracts (Persea americana Mill.) against Streptococcus agalactiae

Abstract

Plants contain numerous constituents and are valuable
sources of new biologically active molecules. Avocado (Persea
americana Mill.) is cultivated and used as food in most tropical and
subtropical countries. Its high nutritional value and biological activities,
as antioxidant, antimicrobial and analgesic properties, have been
thoroughly investigated. Interest in plant extracts with antimicrobial
properties has increased as a result of the indiscriminate use of
antibiotics, leading to the emergence of resistant bacterial strains.
Among bacterial species with clinical importance to multiple hosts,
Streptococcus agalactiae is outstanding, as it can cause infections especially
in humans, fish and cattle. The current study aimed to evaluate
the antimicrobial activity of two extracts (ethanol and dichloromethane)
from avocado seeds, ‘Margarida’ variety, against isolates of S.
agalactiae. Extracts were diluted in ethanol / water (1:1) at a concentration
of 100 mg/mL. Antimicrobial activity was tested by the
disk diffusion method (antibiogram) against isolates of S. agalactiae
of human and fish origin.The ethanol extract showed antimicrobial
activity only for some isolates of S. agalactiae of human origin. The
dichloromethane extract showed activity against all isolates of S. agalactiae
of both origins. A comparison of the results obtained with dichloromethane
extract from isolates of S. agalactiae of human or fish
origin demonstrated the existence of phenotypic variability among
isolates from the same host. However, when comparing measurements
obtained in each of the groups, they were statistically similar,
showing a lack of interpopulation variability. Thus, it can be verified
that the resistance profile of isolates of S. agalactiae was independent
of host origin and typical of the species

Full text

FYTON ISSN 0031 9457 (2016) 85: 218-224
Antibacterial activity of avocado extracts (Persea americana Mill.) against
Streptococcus agalactiae
Actividad antibacteriana de extractos de aguacate (Persea americana Mill.) sobre
Streptococcus agalactiae
Cardoso PF1, JA Scarpassa1, LG Pretto-Giordano2, ES Otaguiri3, SF Yamada-Ogatta3,
G Nakazato3, MRE Perugini4, IC Moreira5, GT Vilas-BÔas1*
Resumen. Las plantas contienen numerosos constituyentes y son
fuentes ricas de nuevas moléculas biológicamente activas. El aguacate
(Persea americana Mill.) es cultivado y utilizado como alimento en la
mayoría de los países tropicales y subtropicales, ya que tiene alto valor
nutricional, y sus actividades biológicas han sido muy investigadas, en-
tre las cuales la actividad antioxidante, analgésica o antimicrobiana. El
interés en extractos vegetales con propiedades antimicrobianas se ha
intensicado como consecuencia de la utilización indiscriminada de
antibióticos, que llevó a la selección de cepas bacterianas resistentes.
Entre las especies bacterianas de relevancia clínica para variados hos-
pederos, se puede destacar la bacteria Streptococcus agalactiae, que pue-
de causar infecciones, principalmente en humanos, peces y ganado. El
objetivo de ese trabajo fue evaluar la actividad antimicrobiana de dos
extractos (etanólico y diclorometanico) de hueso de aguacate variedad
margarita en relación a aislados de S. agalactiae. Los extractos fueron
resuspendidos en etanol/agua en la concentración de 100 mg/mL. La
actividad antibacteriana de los extractos fue comprobada usando el
método de difusión en discos frente a aislados de S. agalactiae de origen
humano y peces. El extracto etanólico presentó actividad antimicrobia-
na solamente para algunos aislados de S. agalactiae de origen humano.
El extracto diclorometanico presentó actividad antimicrobiana para
todos los aislados de S. agalactiae de ambos orígenes. La comparación
de los resultados obtenidos con el extracto diclorometanico enfrente a
los aislados de S. agalactiae de origen humano y peces mostró la exis-
tencia de variabilidad fenotípica entre aislados del mismo hospedero.
Sin embargo, la comparación de las medias obtenidas en cada uno de
los grupos fue estadísticamente semejante, demostrando la ausencia de
variabilidad interpoblacional. De esta manera, se pudo observar que el
perl de resistencia de aislados de S. agalactiae fue independiente del
hospedero de origen y característico de la especie.
Palabras clave: Extractos vegetales; Método de difusión en disco.
Abstract. Plants contain numerous constituents and are valu-
able sources of new biologically active molecules. Avocado (Persea
americana Mill.) is cultivated and used as food in most tropical and
subtropical countries. Its high nutritional value and biological activi-
ties, as antioxidant, antimicrobial and analgesic properties, have been
thoroughly investigated. Interest in plant extracts with antimicro-
bial properties has increased as a result of the indiscriminate use of
antibiotics, leading to the emergence of resistant bacterial strains.
Among bacterial species with clinical importance to multiple hosts,
Streptococcus agalactiae is outstanding, as it can cause infections espe-
cially in humans, sh and cattle. e current study aimed to evaluate
the antimicrobial activity of two extracts (ethanol and dichlorometh-
ane) from avocado seeds, ‘Margarida’ variety, against isolates of S.
agalactiae. Extracts were diluted in ethanol / water (1:1) at a con-
centration of 100 mg/mL. Antimicrobial activity was tested by the
disk diusion method (antibiogram) against isolates of S. agalactiae
of human and sh origin.e ethanol extract showed antimicrobial
activity only for some isolates of S. agalactiae of human origin. e
dichloromethane extract showed activity against all isolates of S. aga-
lactiae of both origins. A comparison of the results obtained with di-
chloromethane extract from isolates of S. agalactiae of human or sh
origin demonstrated the existence of phenotypic variability among
isolates from the same host. However, when comparing measure-
ments obtained in each of the groups, they were statistically similar,
showing a lack of interpopulation variability. us, it can be veried
that the resistance prole of isolates of S. agalactiae was independent
of host origin and typical of the species.
Keywords: Plant extracts; Disk diusion method.
1 Departamento de Biologia Geral, Centro de Ciências Biológicas, Universidade Estadual de Londrina.
2 Departamento de Medicina Veterinária Preventiva, Centro de Ciências Agrárias, Universidade Estadual de Londrina.
3 Departamento de Microbiologia, Centro de Ciências Biológicas, Universidade Estadual de Londrina.
4 Departamento de Patologia, Análises Clínicas e Toxicológicas, Centro de Ciências da Saúde, Universidade Estadual de Londrina.
5 Universidade Tecnológica Federal do Paraná- Campus Londrina, Brazil.
Address correspondence to: Gislayne Trindade Vilas-BÔas, e-mail: gvboas@uel.br
Received 17.X.2014. Accepted 17.IV.2015.

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Avocado extracts against Streptococcus agalactiae
INTRODUCTION
e control of bacterial infections is mostly carried out
with antibiotics. However, the emergence of resistant bacte-
rial strains has become more frequent, leading to the need of
new sources of molecules with antimicrobial activity, which
have been found mainly in microorganisms and plants (Cow-
an, 1999; Mlynarczyk et al., 2010). Natural plant products
have been used since ancient times for medicinal purposes as
they comprise numerous components and valuable sources of
new biologically active molecules (Cowan, 1999; Gupta et al.,
2004).
Many plants synthesize antimicrobial secondary metabo-
lites as part of their normal growth and development, often
keeping them in tissues that need protection against micro-
bial attack (Gupta et al., 2004). e antimicrobial activity of
plant extracts may reside in a variety of dierent phytochemi-
cal constituents, namely terpenoids, essential oils, alkaloids,
lectins, polypeptides and polyphenolics and phenolic sub-
stances (simple phenols, phenolic acids, quinones, avones,
avonols and avonoids, tannins and coumarins) (Gonçalves
et al., 2005). e antibacterial activity of these extracts may
be ascribable to the combined eects of the polyphenols ad-
sorption on bacterial membrane, leading to its rupture and
subsequent leakage of cellular content, and the generation of
hydroperoxides (Negi, 2012).
Among plants, avocado (Persea americana Mill), originated
from Central America, presents a high nutritional value and
is cultivated and used as food in most tropical and subtropi-
cal countries. Its peel, fruit and leaves are commonly used in
America, Antilles and Africa for the treatment of various dis-
eases such as menorrhagia, hypertension, stomach pain, bron-
chitis, diarrhea and diabetes (Adeyemi et al., 2002). However,
avocado seeds are usually discarded during consumption or
industrial processes generating residues that could be an eco-
nomical alternative for treatment of some diseases.
e avocado leaf, stem, fruit and peel have biological ac-
tivities scientically proven (Miranda et al., 1997; Adeyemi
et al., 2002; Quing-Yi et al., 2005; Gomez-Flores et al.,
2008; Castro et al., 2010; Rodríguez-Carpena et al., 2011).
Studies with seed demonstrated antioxidant activity and an-
timicrobial activity against Bacillus cereus, Staphylococcus au-
reus, Listeria monocytogenes, Escherichia coli, Pseudomonas spp.
and Yarrowia lipolytica. e Gram-positive bacteria are more
sensitive than Gram-negative bacteria (Rodríguez-Carpena
et al., 2011). Other seed properties already studied are larvi-
cidal (in Aedesaegypti), antifungal (Candida spp., Cryptococ-
cus neoformans and Malassezia pachydermatis) (Leite et al.,
2009) and antimicrobial activities against several species
including S. aureus, Enterococcus faecalis, Salmonella Enteriti-
dis, Citrobacter freundii, Pseudomonas aeruginosa, Salmonella
Typhimurium, Enterobacter aerogenes and Zygosaccharomyces
bailii (Chia & Dykes, 2010).
Phytochemical studies of the avocado seed allowed the
identication of several classes of active compounds such as
avonoids, anthocyanins, condensed tannins, alkaloids and
triterpenoids in methanolic extracts, while sterols and triter-
penes were detected in the hexane extract (Leite et al., 2009).
Several bacterial species are considered of clinical impor-
tance because they cause a number of diseases in various hosts.
Among these, the species Streptococcus agalactiae, a Gram pos-
itive, catalase negative and facultatively anaerobic bacteria is
remarkable.is species can cause infections in cattle, humans
and sh. Furthermore, it can occasionally infect mice, cats,
dogs, camels and frogs (Elliot et al., 1990; Figueiredo, et al.,
2006; Pereira et al., 2010).
Streptococcus agalactiae is one of the most common causes
of perinatal bacterial infections in humans. It is also an op-
portunistic pathogen of the elderly and immunocompromised
people, and may cause pneumonia, meningitis, bacteremia and
skin or soft tissue infections (Gibbs et al., 2004; Nakamura et
al., 2011). Penicillin is the treatment of choice. However, for
patients allergic to β-lactam, erythromycin or clindamycin are
prescribed. Mammal isolates are preferably β-hemolytic, but
some nonhemolytic have been isolated, and are usually culti-
vated at 37 °C (Evans et al., 2002; Gibbs et al., 2004).
Besides humans, S. agalactiae can infect freshwater and
marine sh, either in sh farming or free in the environment
(Figueiredo et al., 2006). It is considered the main pathogenic
bacteria of dierent species of sh with high mortality. Natu-
rally or experimentally infected sh exhibit symptoms, such
as unilateral or bilateral exophthalmia, corneal opacity, er-
ratic swimming, changes in skin color, skin lesions and ascites
(Figueiredo et al., 2006; Pretto-Giordano et al., 2010a). Fish
isolates of S. agalactiae are usually not hemolytic and are culti-
vated at 30°C, which may indicate phenotypic adaptations to
host (Elliot et al., 1990; Evans et al., 2002; Castro et al., 2008).
S. agalactiae isolates of human source present resistance
to tetracycline, clindamycin, erythromycin, chloramphenicol,
rifampicin, noroxacin, levooxacin, ciprooxacin, moxioxa-
cin (Borger et al., 2005; Correa et al., 2011; Nakamura et al.,
2011; Ki et al, 2012; Usein et al., 2012). Fish isolates may be
resistant to nalidixic acid, gentamicin, neomycin, noroxacin
and streptomycin (Evans et al., 2002; Figueiredo et al., 2006).
e susceptibility of S. agalactiae to natural extracts was
analyzed in dierent works. According to Cueva et al. (2012),
S. agalactiae presented sensitivity to phenolic compounds iso-
lated from wine, epicatechin and gallic acid, and was not sen-
sitive to oenological extracts. It was also sensitive to extracts
of wild mushrooms (Alves et al., 2012) and to the essential
oil from eight eucalyptus species (Elassi et al., 2012). Leaf
extracts of Calyptranthes clusiifolia, Croton oribundus, Heiste-
ria silvianii, Merremia tomentosa and Zanthoxylum riedelianum
also inhibited S. agalactiae growth (Castro et al., 2008).
us, the aim of this study was to investigate the antibacte-
rial activity of avocado (P. americana Mill) seed extracts against

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Cardoso PF et al., FYTON 85 (2016)
S. agalactiae isolates of human and sh origin. erefore, com-
parison of intra- and inter-population variability of resistance
proles was evaluated and indicated the potential therapeutic
use of the avocado seed against this bacterial species.
MATERIALS AND METHODS
Plant extracts. In order to obtain seed extracts of avocado
(P. americana Mill., ‘Margarida’ variety), the seed was initially
separated from the pulp, fragmented, dried and ground into
powder. e seed powder was then exposed to a maceration
process for a period of seven days, either using ethyl alcohol as
solvent, resulting in an extract termed “ethanolic extract”, or
using dichloromethane as solvent, yielding an extract termed
“dichloromethane extract”. Subsequently, the extracts were l-
tered and concentrated in a rotary evaporator. Procedures of
maceration, ltration and concentration were repeated once
more with both extracts. In order to measure the eciency of
extraction, the obtained extracts were weighed and the ratio
between 500g of the initial seed powder and the nal weight
calculated. Extracts were dissolved in ethanol / water (1:1),
stored at room temperature and protected from light until use.
Bacterial strains and culture conditions. e evalua-
tion of 29 S. agalactiae isolates recovered from vaginal-rectal
swabs and urine of female patients at the University Hos-
pital of Universidade Estadual de Londrina (originally used
by Otaguiri et al., 2013) was performed. ese isolates had
already been characterized for bacterial species conrmation
by phenotypic tests (CAMP, KEA, NaCl, hippurate, baci-
tracin, trimethoprim-sulfamethoxazole, Gram staining and
catalase). ese isolates were incubated for 24 hours at 37 °C
in Muller Hinton blood agar plates (supplemented with 5%
sheep blood).
e assessment of 26 isolates of S. agalactiae obtained from
the Nile tilapia (Oreochromis niloticus) with bacterial infection
symptoms was conducted. e isolates were collected from
dierent organs, including eyes, brain, liver, heart, blood, vis-
ceral uid and kidney sh collected at sh farming properties
located in the northern region of Paraná state and northwest
region of São Paulo state, Brazil.e strains had been previ-
ously identied as S. agalactiae by Gram stain and biochemical
assays, and conrmed by more accurate tests, such as API 20
Strep Microtest (BioMerieux) and SlidexStrepto-kit (BioM-
erieux) (Pretto-Giordano et al., 2010b). ese isolates were
incubated for 48 hours at 30 °C in Muller Hinton blood agar
plates.
Antibiograms. e antibacterial activity of avocado seed
extracts against S. agalactiae was evaluated by the Disc dif-
fusion method on Muller Hinton blood agar plates, as rec-
ommended by CLSI (Clinical Laboratory Standard Institute,
2010). For this purpose, bacteria concentration followed the
0.5 MacFarland scale, yielding an inoculum density of ap-
proximately 108 CFU/mL (Ostrosky et al., 2008) which was
homogeneously distributed over the plates using sterile swabs.
Discs of 6 mm diameter (Laborclin, Brazil) received the
application of 10 µL of 100 mg/mL ethanol or dichloro-
methane extracts. Additionally, other discs received 10 µL of
solvents and were used as a negative control. All discs were
kept for an hour under a laminar ow for solvent evaporation
(Ostrosky et al., 2008).
Biplates were used, forming a duplicate of each isolate per
plate. ree discs were placed on each plate side: control, etha-
nol and dichloromethane extract. In other words, two disks
were tested for each extract per strain. Samples of human
source were incubated at 37 °C for 24 hours. Strains of sh
origin were maintained at 30 °C for 48 hours. At the end of
this time, the inhibition zone diameter was measured.
Statistical analysis. e susceptibility test results were an-
alyzed using the Analysis of Variance (ANOVA) followed by
the Tukey test or the Mann-Whitney test for interpopulation
analysis, at 95% condence level. Tests were performed with
the GraphPad InStat program, version 3.05.
RESULTS
After the extraction procedures, the nal weight of extracts
was 12.76 g for the ethanolic and 7.48g for the dichlorometh-
ane extract. Bacterial inhibition by extracts was evaluated
visually by measuring the inhibition zone diameters around
disks (disk diameter included) recorded in millimeters. e
antimicrobial activity was classied into three levels: low ac-
tivity (inhibition zone ≤12 mm), moderate activity (inhibition
zone between 12 and 20 mm) and strong activity (inhibition
zone ≥20 mm), following the criteria adopted in other studies
with plant extracts (Rota et al., 2008; Fei et al, 2011).
Antibiogram results of S. agalactiae isolates are shown in
Table 1 and exemplied in Figures 1 and 2. Both human and
sh isolates showed statistical variability in intra-group analy-
sis, exhibiting an inhibition zone between 7 mm e 13 mm
for human isolates, and between 9 mm and 12 mm for sh
isolates.
For the intergroup analysis, the average of inhibition zones
obtained for each group (human and sh origin) was com-
pared. Statistical analysis for ethanolic extract could not be
performed, since inhibition zones on plates with sh isolates
were not observed. However, dierences in susceptibility be-
tween strains of human and sh could be observed, given that
the rst show some susceptible isolates, while in the latter, no
susceptible isolates were found (Table 1). e antimicrobial
activity of the ethanolic extract, when present, was considered
weak, with an inhibition zone between 7 mm and 9.5 mm.
e mean ± standard deviation of the inhibition zonediam-
eter for the isolates of human origin observed for the dichlo-

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Avocado extracts against Streptococcus agalactiae
Table 1. Antimicrobial activity of avocado seed extracts against S. agalactiae strains.
Tabla 1. Actividad antimicrobiana de extractos de semilla de aguacate contra cepas de S. agalactiae.
Isolate
(human source)
Inhibition zone diameter (mm)
Isolate
(sh source)
Inhibition zone diameter (mm)
Ethanolic extract Dichloromethane
extract Ethanolic extract Dichloromethane
extract
Mean ± Standard
Deviation Mean ± Standard
Deviation Mean ± Standard
Deviation Mean ± Standard
Deviation
67.75 ± 0.35 10.75 ± 0.35 15 0.00 ± 0.00 10.75 ± 0.35
97.75 ± 0.35 11.75 ± 0.35 16 0.00 ± 0.00 10.50 ± 0.00
10 4.00 ± 5.66 11.00 ± 0.00 18 0.00 ± 0.00 10.75 ± 0.35
11 8.75 ± 1.06 11.00 ± 0.71 19 0.00 ± 0.00 11.00 ± 0.00c
12 0.00 ± 0.00 11.00 ± 0.00 23 0.00 ± 0.00 11.00 ± 0.00c
13 0.00 ± 0.00 11.25 ± 0.35 25 0.00 ± 0.00 10.75 ± 0.35
14 0.00 ± 0.00 12.75 ± 0.35 26 0.00 ± 0.00 11.25 ± 0.35 c.e
21 0.00 ± 0.00 11.25 ± 1.06 29 0.00 ± 0.00 10.50 ± 0.00
24 0.00 ± 0.00 10.75 ± 0.35 30 0.00 ± 0.00 10.75 ± 0.35
25 0.00 ± 0.00 11.25 ± 0.35 34 0.00 ± 0.00 10.50 ± 0.00
26 0.00 ± 0.00 10.25 ± 0.35 a 35 0.00 ± 0.00 9.75 ± 0.35 d
27 0.00 ± 0.00 10.50 ± 0.00 a 37 0.00 ± 0.00 9.75 ± 0.35 d
28 0.00 ± 0.00 10.25 ± 0.35 a 38 0.00 ± 0.00 11.00 ± 0.00 c
29 0.00 ± 0.00 10.50 ± 0.00 a 39 0.00 ± 0.00 10.25 ± 0.35
33 4.25 ± 6.01 10.50 ± 0.71 a 40 0.00 ± 0.00 9.25 ± 0.35d
37 7.25 ± 0.35 11.00 ± 0.00 42 0.00 ± 0.00 11.75 ± 0.35 c.e
42 3.50 ± 4.95 11.25 ± 0.35 44 0.00 ± 0.00 10.75 ± 0.35
43 0.00 ± 0.00 11.75 ± 1.06 45 0.00 ± 0.00 11.25 ± 0.35 c.e
49 0.00 ± 0.00 10.50 ± 0.00 a 46 0.00 ± 0.00 10.75 ± 0.35
50 0.00 ± 0.00 11.00 ± 0.71 47 0.00 ± 0.00 10.50 ± 0.00
52 0.00 ± 0.00 12.00 ± 0.00 48 0.00 ± 0.00 9.50 ± 0.00 d
54 0.00 ± 0.00 10.25 ± 0.35 a 50 0.00 ± 0.00 10.50 ± 0.71
56 0.00 ± 0.00 9.75 ± 0.35 a.b 52 0.00 ± 0.00 11.00 ± 0.71 c
59 0.00 ± 0.00 11.00 ± 0.71 53 0.00 ± 0.00 10.25 ± 0.35
60 0.00 ± 0.00 10.25 ± 0.35 a 55 0.00 ± 0.00 10.75 ± 1.06
61 3.50 ± 4.95 10.25 ± 0.35 56 0.00 ± 0.00 11.00 ± 0.00 c
62 0.00 ± 0.00 11.00 ± 0.00
70 0.00 ± 0.00 11.00 ± 0.00
96 0.00 ± 0.00 11.25 ± 1.06
a: statistically diers from strain 14; b: statistically diers from strain 52; c: statistically diers from strain 40; d: statistically diers from
strain 42; e: statistically diers from strain 48 (P<0.05).
a: diere estadísticamente de la cepa 14; b: diere estadísticamente de la cepa 52; c: diere estadísticamente de la cepa 40; d: diere estadísticamente de la
cepa 42; e: diere estadísticamente de la cepa 48 (P<0,05).

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Cardoso PF et al., FYTON 85 (2016)
Fig. 1. Antibiogram of S. agalactiae isolates of human source: a) strain 6, b) strain 14 and c) strain 25. Disc 1: ethanol/water control;
Disc 2: ethanolic extract (100 mg/mL); Disc 3: dichloromethane extract (100 mg/mL).
Fig. 1. Antibiograma de aislados humanos de S. agalactiae: a) cepa 6, b) cepa 14 y c) cepa 25. Disco 1: control etanol/agua; Disco 2: extracto
etanólico (100 mg/mL); Disco 3: extracto diclorometanico (100 mg/mL).
Fig. 2. Antibiogram of S. agalactiae isolates of fish source: (a) strain 26, (b) strain 34 and (c) strain 55. Disc 1: ethanol/water control; Disc
2: ethanolic extract (100 mg/mL); Disc 3: dichloromethane extract (100 mg/mL).
Fig. 2. Antibiograma de aislados de peces de S. agalactiae: (a) cepa 26, (b) cepa 34 y (c) cepa 55. Disco 1: control etanol/agua; Disco 2:
extracto etanólico (100 mg/mL); Disco 3: extracto diclorometanico (100 mg/mL).
romethane extract was 10.93 ± 0.62 mm. On the other hand,
sh isolates presented a mean ± standard deviation of 10.61 ±
0.56 mm. e comparison between means was not statistically
signicant, with p = 0.0897. e dichloromethane extract an-
tibacterial activity was considered weak.
DISCUSSION
Plant extracts are sources of a variety of biotechnology
products. erefore, countless studies have been conducted
in order to evaluate characteristics of these extracts, which
can be used for the treatment of diseases, due to their an-
timicrobial, antifungal, analgesic, anti-inammatory and
antitumor activities (Miranda et al., 1997; Adeyemi et al.,
2002; Qing-Yi et al., 2005; Leite et al., 2009; Rodríguez-
Carpena et al., 2011). Among the commonly evaluated
properties, the antimicrobial activity has received special
attention, and numerous studies have been conducted, in-
cluding dierent avocado extracts (Gomez-Flores et al.,
2008; Castro et al., 2010; Chia & Dykes, 2010; Rodríguez-
Carpena et al., 2011).
However, although widely used, there are not yet any
standardization methods to analyze the antimicrobial activ-
ity of extracts of natural products (Ostrosky et al., 2008). e
Disk diusion test is indicated by the FDA (Food and Drug
Administration / USA) and established as standard by the

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Avocado extracts against Streptococcus agalactiae
CLSI (Clinical Laboratory Standard Institute / USA, 2010),
and, therefore, was the method chosen to conduct this study.
Several S. agalactiae isolates of human and sh origin were
used in this work, aiming to comprise dierent phenotypic
variations found in isolates from each of the two sources, as
well as verify what kind of host presents isolates more suscep-
tible to the evaluated extracts.
Human source isolates used in this study have already been
analyzed for capsular type, genotyping by MLVA, antibiotics
susceptibility and genetic virulence determinants. e results
suggest that even commensal S. agalactiae isolates have high
potential for virulence and are susceptible to most antimi-
crobial agents tested (penicillin, ampicillin, vancomycin, etc.)
(Otaguiri et al., 2013). However, they presented moderate re-
sistance to erythromycin (19%) and clindamycin (13%) which
demands the search for new treatment alternatives, especially
for patients allergic to β-lactam antibiotics.
e dierence in eciency of the two extracts can be ex-
plained by the dierence in polarity of solvents. During the
extraction process, polarity inuences solubility of the main
active substance, leading to dierence in their chemical com-
position and consequently, in their biological activity (Idris
et al., 2009). e yield of extraction and concentration of the
extract solution can also intervene in the results.
e antimicrobial activity of avocado extracts may be as-
cribable to its chemical composition. Phytochemical screen-
ing highlighted the presence of phenolic compounds in avo-
cado tissues, whose antimicrobial activity is well documented
(Idris et al., 2009; Rodriguez-Carpena et al., 2011).
Avocado seed extracts showed low antimicrobial activity
against of S. agalactiae isolates. is can probably be overcome
by increasing extract concentration. e results indicate that
the avocado seed is a potential source of antimicrobial sub-
stances and arouses considerable interest in new research with
more puried extracts for the identication of compounds re-
sponsible for the antimicrobial activity.
ACKNOWLEDGEMENTS
is work was supported by grants from Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and
Conselho Nacional de Desenvolvimento Cientíco e Tec-
nológico (CNPq).
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