Sampling the Antibiotic Resistome

Antimicrobial Research Centre, Department of Biochemistry and Biomedical Sciences, McMaster University, Ontario, Canada, L8N 3Z5.
Science (Impact Factor: 33.61). 02/2006; 311(5759):374-7. DOI: 10.1126/science.1120800
Source: PubMed


Microbial resistance to antibiotics currently spans all known classes of natural and synthetic compounds. It has not only hindered our treatment of infections but also dramatically reshaped drug discovery, yet its origins have not been systematically studied. Soil-dwelling bacteria produce and encounter a myriad of antibiotics, evolving corresponding sensing and evading strategies. They are a reservoir of resistance determinants that can be mobilized into the microbial community. Study of this reservoir could provide an early warning system for future clinically relevant antibiotic resistance mechanisms.

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Available from: Vanessa D'Costa, Nov 13, 2015
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    • "Antibiotic resistance has in the last decades put an increasing pressure on human healthcare globally, estimated to account for 700,000 deaths every year (Review on Antimicrobial Resistance, 2014). The environment has repeatedly been identified as a source for resistance genes to pathogens (D'Costa et al., 2006, 2011; Finley et al., 2013; Martinez, 2008; Pruden et al., 2013; Wright, 2010), however, it is unclear to what extent antibiotics in the environment contribute to this development. Furthermore, current regulatory systems on pharmaceutical pollution do not account for resistance (Ashbolt et al., 2013; Boxall et al., 2012). "
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    ABSTRACT: There are concerns that selection pressure from antibiotics in the environment may accelerate the evolution and dissemination of antibiotic-resistant pathogens. Nevertheless, there is currently no regulatory system that takes such risks into account. In part, this is due to limited knowledge of environmental concentrations that might exert selection for resistant bacteria. To experimentally determine minimal selective concentrations in complex microbial ecosystems for all antibiotics would involve considerable effort. In this work, our aim was to estimate upper boundaries for selective concentrations for all common antibiotics, based on the assumption that selective concentrations a priori need to be lower than those completely inhibiting growth. Data on Minimal Inhibitory Concentrations (MICs) were obtained for 111 antibiotics from the public EUCAST database. The 1% lowest observed MICs were identified, and to compensate for limited species coverage, predicted lowest MICs adjusted for the number of tested species were extrapolated through modeling. Predicted No Effect Concentrations (PNECs) for resistance selection were then assessed using an assessment factor of 10 to account for differences between MICs and minimal selective concentrations. The resulting PNECs ranged from 8ng/L to 64μg/L. Furthermore, the link between taxonomic similarity between species and lowest MIC was weak. This work provides estimated upper boundaries for selective concentrations (lowest MICs) and PNECs for resistance selection for all common antibiotics. In most cases, PNECs for selection of resistance were below available PNECs for ecotoxicological effects. The generated PNECs can guide implementation of compound-specific emission limits that take into account risks for resistance promotion.
    Environment International 11/2015; 86:140-149. DOI:10.1016/j.envint.2015.10.015 · 5.56 Impact Factor
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    • "Environmental and anthropogenic factors play a key role in the spread of Legionella spp., as ecological factors, geographical area, and the efficacy of disinfection methods influence their multiplication and survival. In addition, it has been shown that the presence of antibiotics in the environment may promote the evolution of microbial resistance mechanisms (D'Costa et al., 2006). This is particularly important for Legionella spp. that colonize environmental water systems, where they may be exposed to antibiotics from medical or veterinary practices, or even to those secreted by other microorganisms (Almahmoud et al., 2009). "
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    ABSTRACT: The purpose of this study was to describe the susceptibility of environmental strains of Legionella spp. to 10 antimicrobials commonly used for legionellosis therapy. A study of environmental strains could be useful to timely predict the onset of antibiotic resistance in the environment before it is evidenced in clinical specimens. The minimum inhibitory concentrations (MICs) of 100 environmental Legionella pneumophila (Lpn) strains belonging to serogroups (sgs) 1, 6, 8, and 10 were tested using the E-test methodology on buffered charcoal yeast extract agar supplemented with α-ketoglutarate. The most frequent sgs were selected from those obtained during microbiological surveillance conducted in 2014 in a hospital in Southern Italy. The MICs were read after 2 days of incubation at 35°C in a humidified atmosphere without CO2. All isolates were inhibited by low concentrations of fluoroquinolones and macrolides. Rifampicin was the most active drug against the isolates in vitro. All Lpn isolates were inhibited by the following drugs (in decreasing order of their MICs): doxycycline>tigecycline>cefotaxime. The MICs of azithromycin, ciprofloxacin, levofloxacin, moxifloxacin, and tigecycline were significantly lower for Lpn non-sg 1 than Lpn sg 1 isolates. Susceptibility testing of Legionella strains to appropriate antibiotics should be performed often to evaluate the possible emergence of resistance, to improve the outcomes of patients, and to reduce the direct costs associated with hospitalization. Copyright © 2015. Published by Elsevier Inc.
    Environmental Research 08/2015; 142:ER15780. DOI:10.1016/j.envres.2015.08.013 · 4.37 Impact Factor
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    • "It is not yet clear and arguments among scientists increase daily about the involvement of man and his many anthropogenic activities in the spread of resistance elements in microorganisms . Several studies have reported lack of tangible relationship between anthropogenic activities and antibiotic resistance in bacteria and many believe that the elements that selects for resistance are naturally present within microbial genome (Davis and Anandan, 1970; Hughes and Datta, 1983; Barlow and Hall, 2002; Hall and Barlow, 2004; D'Costa et al., 2006, 2011; Wright, 2007, 2010; Baltz, 2008; Brown and Balkwill, 2009; Thaller et al., 2010; Toth et al., 2010; Bhullar et al., 2012; Cox and Wright, 2013). On the other hand, evidence abound that increased bacterial resistance to antibiotics and the transfer of resistance elements is a modern phenomenon having a strong link with anthropogenic activities (Knapp et al., 2010; Bhullar et al., 2012). "
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    ABSTRACT: Antibiotics are emerging environmental contaminants, causing both short-term and long-term alterations of natural microbial communities due to their high biological activities. The antibiotic resistance pattern of bacteria from anthropogenic polluted Oluwa River, Nigeria was carried out. Microbial profiling and antibiotic sensitivity tests were carried out on water and sediment samples using 13 different antibiotics. Microorganisms isolated include those in the genera Bacillus, Micrococcus, Pseudomonas, Streptococcus, Proteus and Staphylococcus. The microbial count of isolates from water samples ranged between 94.10 × 102 Cfu/100 ml and 156.20 × 102 Cfu/100 ml while that of sediment samples ranged from 2.55 × 104 Cfu g−1 to 14.30 × 104 Cfu g−1. From the water isolates, 100% resistance to antibiotics was found in Micrococcus spp. and Pseudomonas spp. while another Micrococcus, Streptococcus, Staphylococcus and Bacillus spp. showed between 40% and 90% resistances. From the sediment isolates, 100% resistance to antibiotics was found in a Bacillus spp. and Pseudomonas spp. while another Bacillus, Micrococcus, Staphylococcus, Streptococcus and Proteus spp. showed between 70% and 90% resistances. Multiple antibiotic resistance (MAR) was shown by all the isolates and Bacillus, Micrococcus and Pseudomonas spp. showed the highest resistances (100%) to all antibiotics. Thus, Oluwa River is not safe for public consumption.
    Egyptian Journal of Aquatic Research 10/2014; 40(3). DOI:10.1016/j.ejar.2014.09.002
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