Antibiotic resistance of bacteria in raw and biologically treated sewage and in groundwater below leaking sewers

More than 750 isolates of faecal coliforms (>200 strains), enterococci (>200 strains) and pseudomonads (>340 strains) from three wastewater treatment plants (WTPs) and from four groundwater wells in the vicinity of leaking sewers were tested for resistance against 14 antibiotics. Most, or at least some, strains of the three bacterial groups, isolated from raw or treated sewage of the three WTPs, were resistant against penicillin G, ampicillin, vancomycin, erythromycin, triple sulfa and trimethoprim/sulfamethoxazole (SXT). Only a few strains of pseudomonads or faecal coliforms were resistant against some of the other tested antibiotics. The antibiotic resistances of pseudomonads, faecal coliforms and enterococci from groundwater varied to a higher extent. In contrast to the faecal coliforms and enterococci, most pseudomonads from all groundwater samples, including those from non-polluted groundwater, were additionally resistant against chloramphenicol and SXT. Pseudomonads from sewage and groundwater had more multiple antibiotic resistances than the faecal coliforms or the enterococci, and many pseudomonads from groundwater were resistant to more antibiotics than those from sewage. The pseudomonads from non-polluted groundwater were the most resistant isolates of all. The few surviving faecal coliforms in groundwater seemed to gain multiple antibiotic resistances, whereas the enterococci lost antibiotic resistances. Pseudomonads, and presumably, other autochthonous soil or groundwater bacteria, such as antibiotic-producing Actinomyces sp., seem to contribute significantly to the gene pool for acquisition of resistances against antibiotics in these environments.     

Incidence of multiple antibiotic resistant Escherichia coli in the Bhavani River

Of 107 Escherichia coli strains isolated from the water, sediment and fish of the Bhavani River, all of which are considered potential causes of human enteric disease, 62% were resistant to more than four antibiotics. Levels of resistance to bacitracin, penicillin, and novobiocin were generally high whereas those to polymyxin-B and chloramphenicol were much lower. A high incidence of multiple antibiotic resistant E. coli was noted in all samples and the multiple antibiotic resistance index of the strains showed that 95% of the strains originated either from man or cattle.     

<Emphasis Type="Italic">Campylobacter</Emphasis> spp., <Emphasis Type="Italic">Salmonella</Emphasis> spp., Verocytotoxic <Emphasis Type="Italic">Escherichia coli</Emphasis>, and Antibiotic Resistance in Indicator Organisms in Wild Cervids

Faecal samples were collected, as part of the National Health Surveillance Program for Cervids (HOP) in Norway, from wild red deer, roe deer, moose and reindeer during ordinary hunting seasons from 2001 to 2003. Samples from a total of 618 animals were examined for verocytotoxic E. coli (VTEC); 611 animals for Salmonella and 324 animals for Campylobacter. A total of 50 samples were cultivated from each cervid species in order to isolate the indicator bacterial species E. coli and Enterococcus faecalis/E. faecium for antibiotic resistance pattern studies. Salmonella and the potentially human pathogenic verocytotoxic E. coli were not isolated, while Campylobacter jejuni jejuni was found in one roe deer sample only. Antibiotic resistance was found in 13 (7.3%) of the 179 E. coli isolates tested, eight of these being resistant against one type of antibiotic only. The proportion of resistant E. coli isolates was higher in wild reindeer (24%) than in the other cervids (2.2%). E. faecalis or E. faecium were isolated from 19 of the samples, none of these being reindeer. All the strains isolated were resistant against one (84%) or more (16%) antibiotics. A total of 14 E. faecalis -strains were resistant to virginiamycin only. The results indicate that the cervid species studied do not constitute an important infectious reservoir for either the human pathogens or the antibiotic resistant microorganisms included in the study.     

Incidence of Staphylococcus aureus, coliforms and antibiotic-resistant strains of Escherichia coli in rural water supplies in Port Harcourt

The bacteriological quality of some rural water supplies in Port Harcourt was monitored over a 3 month period. The supplies were unsatisfactory as judged by standard plate counts (10³/ml) and the presence of presumptive and faecal coliforms and Staphylococcus aureus. The recovery of potentially pathogenic bacteria (e.g. Pseudomonas aeruginosa ) further substantiated the existence of health hazards. The most frequently isolated coliforms were Escherichia coli, Enterobacter aerogenes and Klebsiella pneumoniae. Coliform contamination was greater in well water than in river or stream water samples. An antibiotic sensitivity test revealed that 17.5–27.2% of E. coli strains were resistant to three or more antibiotics. Escherichia coli isolated from well water samples exhibited the greatest degree of multiple resistance. Some strains were resistant to all the six antibiotics tested. The danger of an epidemic of waterborne diseases in the communities as a result of drinking water from these non-potable sources is noted.     

Assessment of three indigenous South African herbivores as potential reservoirs and vectors of antibiotic-resistant <Emphasis Type="Italic">Escherichia coli</Emphasis>

Due to limited data available on the presence of antibiotic-resistant (ABR) bacteria in faeces of wild herbivores in South Africa, this study analysed resistance patterns for Escherichia coli isolates from wildebeest, zebra and giraffe in addition to pet and farm pig faeces. Total and faecal coliforms and E. coli were quantified in faecal matter using a most probable number (MPN) guideline procedure. Antibiotic resistance profiles against 12 selected antibiotics representing seven classes were determined for 30 randomly selected E. coli isolates from each animal using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) disk diffusion procedure. While log₁₀ MPN values per gram of animal faeces for total/faecal coliforms ranged from 4.51/4.11 to 5.70/5.50, the E. coli MPN values were in a range of 3.43–5.14. The proportion of ABR E. coli isolates ranged from 43% (giraffe) to 93% (zebra). About 47% of E. coli isolates from zebra faeces were categorized as multidrug-resistant (MDR), while for wildebeest and giraffe, no MDR isolates were detected. In comparison, 10% of E. coli isolates from pet pig and about 7% from farm pig faeces were categorized as MDR. Although most MDR isolates were resistant to at least one β-lactam antibiotic, only one MDR isolate from farm pig faeces was resistant to both norfloxacin and ciprofloxacin, the two fluoroquinolones tested. However, no resistance was detected to the tested carbapenems and tigecycline. The results of this study indicate that indigenous South African herbivores may serve as potential reservoirs and vectors for the dissemination of ABR E. coli strains.     

Incidence of Staphylococcus aureus, coliforms and antibiotic-resistant strains of Escherichia coli in rural water supplies in Port Harcourt

The bacteriological quality of some rural water supplies in Port Harcourt was monitored over a 3 month period. The supplies were unsatisfactory as judged by standard plate counts (10(3)/ml) and the presence of presumptive and faecal coliforms and Staphylococcus aureus. The recovery of potentially pathogenic bacteria (e.g. Pseudomonas aeruginosa) further substantiated the existence of health hazards. The most frequently isolated coliforms were Escherichia coli, Enterobacter aerogenes and Klebsiella pneumoniae. Coliform contamination was greater in well water than in river or stream water samples. An antibiotic sensitivity test revealed that 17.5-27.2% of E. coli strains were resistant to three or more antibiotics. Escherichia coli isolated from well water samples exhibited the greatest degree of multiple resistance. Some strains were resistant to all the six antibiotics tested. The danger of an epidemic of waterborne diseases in the communities as a result of drinking water from these non-potable sources is noted.     

Identification of sources of Escherichia coli in South Carolina estuaries using antibiotic resistance analysis

Fecal pollution from nonhuman (pets, livestock or wildlife) and human sources is often one of the major factors associated with urbanization that contribute to the degradation of water quality. Methods to differentiate animal from human sources of fecal coliform contamination could assist resource managers in developing strategies to protect shellfish harvesting areas and recreational waters. In this study, surface water samples were collected from both a developed and an undeveloped watershed in coastal South Carolina. Influent and effluent samples from several wastewater treatment plants (WWTPs) in the same area were also collected. Most Probable Numbers (MPNs) of fecal coliforms were determined for all samples. Escherichia coli isolates were analyzed for antibiotic resistance (AR) to 10 antibiotics. Then, AR indices (no. of resistant/total no. of antibiotics tested), were calculated for each isolate and site. Results indicated that MPNs from the WWTP samples were significantly higher than those from the developed watershed which were significantly higher than those from the undeveloped watershed (p<0.0001). The AR analyses suggested that there was a trend toward increased antibiotic resistance in samples for the urbanized Broad Creek (BC) watershed. In the Okatee River (OR), E. coli isolates from three sites (20%) showed resistance to a single antibiotic (penicillin) but in BC, isolates from seven sites (47%) were resistant to multiple antibiotics, and the predominant resistance pattern was chlortetracycline-oxytetracycline-tetracycline. Raw sewage isolates from most WWTPs contained E. coli that exhibited resistance to multiple antibiotics. Cluster analysis indicated that all resistant OR sites had antibiotic resistant isolates that matched AR patterns found in isolates from WWTPs. Similarly, six of the seven sites in BC had AR patterns that matched with resistance patterns in WWTPs. These results suggest that AR testing may be a useful tool for differentiating E. coli from human and wildlife sources. Further testing of bacterial isolates from known animal sources is necessary to better assess the utility of this approach.     

Multidrug-Resistant Enterococci in Animal Meat and Faeces and Co-Transfer of Resistance from an <Emphasis Type="Italic">Enterococcus durans</Emphasis> to a Human <Emphasis Type="Italic">Enterococcus faecium</Emphasis>

Forty-eight isolates resistant to at least two antibiotics were selected from 53 antibiotic-resistant enterococci from chicken and pig meat and faeces and analysed for specific resistance determinants. Of the 48 multidrug-resistant (MDR) strains, 31 were resistant to two antibiotics (29 to erythromycin and tetracycline, 1 to erythromycin and vancomycin, 1 to vancomycin and tetracycline), 14 to three (erythromycin, tetracycline and vancomycin or ampicillin) and 3 to four (erythromycin, vancomycin, ampicillin and gentamicin). erm(B), tet(M), vanA and aac (6′)-Ie aph (2′′)-Ia were the antibiotic resistance genes most frequently detected. All 48 MDR enterococci were susceptible to linezolid and daptomycin. Enterococcus faecalis (16), Enterococcus faecium (8), Enterococcus mundtii (2) and Enterococcus gallinarum (1) were identified in meat, and E. faecium (13) and Enterococcus durans (13) in faeces. Clonal spread was not detected, suggesting a large role of gene transfer in the dissemination of antibiotic resistance. Conjugative transfer of resistance genes was more successful when donors were enterococcal strains isolated from faeces; co-transfer of vanA and erm(B) to a human E. faecium occurred from both E. faecium and E. durans pig faecal strains. These data show that multidrug resistance can be found in food and animal species other than E. faecium and E. faecalis, and that these species can efficiently transfer antibiotic resistance to human strains in inter-specific matings. In particular, the occurrence of MDR E. durans in the animal reservoir could have a role in the emergence of human enterococcal infections difficult to eradicate with antibiotics.     

Antimicrobial resistant coliform bacteria in the Gomti river water and determination of their tolerance level

The distribution of resistance to ampicillin, chloramphenicol, sulfonamides, tetracycline, and streptomycin among coliform in the Gomti river water samples was investigated. The coliform populations were isolated on Mac Conky and eosin methylene blue (EMB) agar plates supplemented with antibiotics. The incidence of resistance among the coliform population varied considerably in different drug and water sampling sites. Coliform bacteria showed lower drug resistant viable count in sampling site-III (receiving treated wastewater) as compared to more polluted site-I and site-II. Viable count of coliform population obtained on both medium was recorded higher against erythromycin from sampling site-III. Lower viable count of coliforms was recorded against tetracycline in site-II and III. Similar resistance pattern was obtained in the frequency of E. coli and Enterobacter species from all the three sampling sites. Percentage of antibiotic resistant E. coli was observed higher than Enterobacter spp among the total coliforms against all antibiotics tested without Erythromycin and penicillin in site-I and II respectively. Isolates of E. coli and Enterobacter spp. showed their tolerance level (MIC) in the range of 2-100 against the antibiotics tested. Maximum number of isolates of both genus exhibited their MICs at lower concentration range 2-5µg/ml against ciprofloxacin, tetracyclin and amoxycillin.

Abbreviations

EMB - Eosin methylene blue, IMViC tests - Indole, Methyl Red, Voges Proskauer and Citrate Utilization Tests, MIC - Minimum inhibitory concentration.     

Antibiotic resistance and detection of β-lactamase in bacterial strains of Staphylococci and Escherichia coli isolated from foodstuffs

Seventy strains of Staphylococcus spp. and Escherichia coli (35 each) were isolated from various foodstuffs and identified on the basis of cultural, morphological and biochemical characteristics and were further tested for their antibiotic susceptibility with commonly used antibiotics/drugs. 69.2% of the strains of Staphylococci were resistant to co-trimazine and 34.6% were resistant to penicillin-G. 19.2% of the staphylococcal isolates exhibited resistance to cloxacillin, nalidixic acid, methicillin and tetracycline whereas 15.3% of the staphylococcal isolates were resistant to amoxycillin and nitrofurantoin. The isolated E. coli strains exhibited sharp peaks of resistance to antimicrobial agents such as tetracycline (72%), doxycycline (60%) and nalidixic acid (48%). Forty-four percent of the E. coli strains were resistant to nitrofurantoin and penicillin-G respectively. Among the 13 antibiotics/drugs tested for resistance, six different resistance patterns were observed in staphylococcal isolates and seven different resistance patterns were observed in the E. coli isolates from various foodstuffs. Bacterial strains exhibiting MIC values 100 g/ml for ampicillin and cloxacillin were screened for -lactamase activity and out of 10 staphylococcal isolates, seven were found to be positive for -lactamase, whereas out of 13 E. coli isolates tested for -lactamase production, only three were found to be positive.     

A set of novel multiplex Taqman real-time PCRs for the detection of diarrhoeagenic Escherichia coli and its use in determining the prevalence of EPEC and EAEC in a university hospital

Background

Escherichia coli isolates of equine faecal origin were investigated for antibiotic resistance, resistance genes and their ability to perform horizontal transfer.

Methods

In total, 264 faecal samples were collected from 138 horses in hospital and community livery premises in northwest England, yielding 296 resistant E. coli isolates. Isolates were tested for susceptibility to antimicrobial drugs by disc diffusion and agar dilution methods in order to determine minimum inhibitory concentrations (MIC). PCR amplification was used to detect genes conferring resistance to: ampicillin (TEM and SHV beta-lactamase), chloramphenicol (catI, catII, catIII and cml), tetracycline (tetA, tetB, tetC, tetD, tet E and tetG), and trimethoprim (dfrA1, dfrA9, dfrA12, dfrA13, dfr7, and dfr17).

Results

The proportion of antibiotic resistant isolates, and multidrug resistant isolates (MDR) was significantly higher in hospital samples compared to livery samples (MDR: 48% of hospital isolates; 12% of livery isolates, p < 0.001). Resistance to ciprofloxacin and florfenicol were identified mostly within the MDR phenotypes. Resistance genes included dfr, TEM beta-lactamase, tet and cat, conferring resistance to trimethoprim, ampicillin, tetracycline and chloramphenicol, respectively. Within each antimicrobial resistance group, these genes occurred at frequencies of 93% (260/279), 91%, 86.8% and 73.5%, respectively; with 115/296 (38.8%) found to be MDR isolates. Conjugation experiments were performed on selected isolates and MDR phenotypes were readily transferred.

Conclusions

Our findings demonstrate that E. coli of equine faecal origin are commonly resistant to antibiotics used in human and veterinary medicine. Furthermore, our results suggest that most antibiotic resistance observed in equine E. coli is encoded by well-known and well-characterized resistant genes common to E. coli from man and domestic animals. These data support the ongoing concern about antimicrobial resistance, MDR, antimicrobial use in veterinary medicine and the zoonotic risk that horses could potentially pose to public health.     

VIM‐1 carbapenemase‐producing Escherichia coli in gulls from southern France

Acquired carbapenemases currently pose one of the most worrying public health threats related to antimicrobial resistance. A NDM‐1‐producing Salmonella Corvallis was reported in 2013 in a wild raptor. Further research was needed to understand the role of wild birds in the transmission of bacteria resistant to carbapenems. Our aim was to investigate the presence of carbapenem‐resistant Escherichia coli in gulls from southern France. In 2012, we collected 158 cloacal swabs samples from two gull species: yellow‐legged gulls (Larus michahellis) that live in close contact with humans and slender‐billed gulls (Chroicocephalus genei) that feed at sea. We molecularly compared the carbapenem‐resistant bacteria we isolated through culture on selective media with the carbapenem‐susceptible strains sampled from both gull species and from stool samples of humans hospitalized in the study area. The genes coding for carbapenemases were tested by multiplex PCR. We isolated 22 carbapenem‐resistant E. coli strains from yellow‐legged gulls while none were isolated from slender‐billed gulls. All carbapenem‐resistant isolates were positive for bla_VIM‐1 gene. VIM‐1‐producing E. coli were closely related to carbapenem‐susceptible strains isolated from the two gull species but also to human strains. Our results are alarming enough to make it urgently necessary to determine the contamination source of the bacteria we identified. More generally, our work highlights the need to develop more bridges between studies focusing on wildlife and humans in order to improve our knowledge of resistant bacteria transmission routes.     

Toxin Production and Antibiotic Resistances in Escherichia coli Isolated from Bathing Areas Along the Coastline of the Oslo Fjord

The presence of enterovirulent and/or antibiotic resistant strains of Escherichia coli in recreational bathing waters would represent a clear health issue. In total, 144 E. coli isolated from 26 beaches along the inner Oslo fjord were examined for virulence determinants and resistance to clinically important antibiotics. No isolates possessed the genetic determinants associated with enterotoxigenic strains and none showed the prototypic sorbitol negative, O157:H7 phenotype. A small number (～1 %) produced alpha-hemolysin. Occurrences and patterns of antibiotic resistances were similar to those of E. coli isolated previously from environmental samples. In total, 6 % of the strains showed one or more clinically relevant resistances and 1.4 % were multi-drug resistant. Microarray analyses suggested that the resistance determinants were generally associated with mobile genetic elements. Resistant strains were not clonally related, and were, furthermore not concentrated at one or a few beach sites. This suggests that these strains are entering the waters at a low rate but in a widespread manner. The study demonstrates that resistant E. coli are present in coastal bathing waters where they can come into contact with bathers, and that the resistance determinants are potentially transferable. Some of the resistances registered in the study are to important antibiotics used in human medicine such as fluoroquinolones. The spread of antibiotic resistant genes, from the clinical setting to the environment, has clear implications with respect to the current management of bacterial infections and the long term value of antimicrobial therapy. The present study is the first of its kind in Norway.     

The microbiology of a pharmaceutical effluent and its public health implications

The effluent of a pharmaceutical company was examined microbiologically. Its bacterial count was 2.15 × 10⁵ c.f.u./ml and there was evidence of faecal contamination with MPN of > 1800. The organisms encountered included Staphylococcus aureus, Escherichia coli, Proteus vulgaris, Serratia marcescens and Pseudomonas aeruginosa. The resistances of the 25 bacterial strains isolated from the effluent to the commonly used antibiotics were studied. About 80% of the isolates were resistant to Amoxycillin, 76% to Nitrofurantoin, 64% to Cotrimoxazole and Augmentin, 60% were resistant to Nalidixic acid, 52% were resistant to Tetracycline and Ofloxacin, while resistance of 12% was obtained for Gentamicin. Among the eight antibiotics tested, seven patterns of drug resistance were obtained and all of them were multiple-drug resistance with the number of antibiotics ranging from 2–8. All the strains of E. coli and S. aureus had high MIC values for Cloxacillin and Amoxycillin. In all, 13 strains of the bacterial isolates had evidence for the production of -lactamases. The potential of the effluent in spreading drug resistance and the public health implications are discussed.     

Antimicrobial resistance of Escherichia coli isolated from freshwaters and hospital effluents in Belgium

The purpose of this work was to evaluate the level of antimicrobial resistant Escherichia coli isolates in freshwaters and hospital effluents in Belgium. The samples were collected from 24 locations along the Ourthe, Vesdre, Amblève and Meuse rivers and in the wastewater effluents of several hospitals. The sampling stations in rivers were classified according to the dominant land covers of the rivers (rural, urban and forest areas). Two sampling campaigns were organized in May and October 2019 to highlight a possible seasonal effect. A total of 938 E. coli strains were isolated on Chromogenic Selective Tryptone Bile X-glucuronide (TBX) and TBX supplemented with amoxicillin (TBX+AMX) media. Disk diffusion assays were performed following the EUCAST's recommendations to assess the antimicrobial resistance against 12 antibiotics. A total of 32·7% of strains were at least resistant to one antibiotic and 24·6% were multiple antimicrobial resistant strains on TBX. The highest resistance rates were found for ampicillin (AMP), amoxicillin coupled with clavulanic acid (AMC) and sulfamethoxazole/trimethoprim (SXT). The lowest resistance rates were observed for meropenem (MEM) and ertapenem (ETP), which are last resort antibiotics. No significant difference was observed between both campaigns for the resistance rate to antibiotics.     

Antibiotic resistance in faecal bacteria (Escherichia coli,Enterococcus spp.) in feral pigeons

Aims: To determine the presence of antibiotic‐resistant faecal Escherichia coli and Enterococcus spp. in feral pigeons (Columba livia forma domestica) in the Czech Republic. Methods and Results: Cloacal swabs of feral pigeons collected in the city of Brno in 2006 were cultivated for antibiotic‐resistant E. coli. Resistance genes, class 1 and 2 integrons, and gene cassettes were detected in resistant isolates by polymerase chain reaction (PCR). The samples were also cultivated for enterococci. Species status of enterococci isolates was determined using repetitive extragenic palindromic‐PCR. Resistance genes were detected in resistant enterococci by PCR. E. coli isolates were found in 203 of 247 pigeon samples. Antibiotic resistance was recorded in three (1·5%, n_E. coli = 203) isolates. Using agar containing ciprofloxacin, 12 (5%, n_samples = 247) E. coli strains resistant to ciprofloxacin were isolated. No ESBL‐producing E. coli isolates were detected. A total of 143 enterococci were isolated: Ent. faecalis (36 isolates), Ent. faecium (27), Ent. durans (19), Ent. hirae (17), Ent. mundtii (17), Ent. gallinarum (12), Ent. casseliflavus (12) and Ent. columbae (3). Resistance to one to four antibiotics was detected in 45 (31%) isolates. Resistances were determined by tetK, tetL, tetM, tetO, aac(6′)aph(2′′), ant(4′)‐Ia, aph(3′)‐IIIa, ermB, pbp5, vanA and vanC1 genes. Conclusions: Antibiotic‐resistant E. coli and Enterococcus spp. occurred in feral pigeons in various prevalences. Significance and Impact of the Study: Feral pigeon should be considered a risk species for spreading in the environment antimicrobial resistant E. coli and enterococci.     

Viability and survival capability of quinolone-resistant uropathogenic <Emphasis Type="Italic">Escherichia coli</Emphasis>

Uropathogenic strains of E. coli isolated from urine of patients with urinary tract infections were tested for antibiotic sensitivity using bio-Merieux kits and ATB-UR 5 expression system. The virulence of strains was evaluated by serum bactericidal assay, macrophage “killing” and bacterial adhesive tests. Survival capability of strains was assessed under starvation in saline. The results showed that quinolone-resistant uropathogenic strains of E. coli exhibit significantly reduced adhesive potential but relatively high resistance to serum and macrophage bactericidity. In contrast to laboratory strains, the quinolone-resistant uropathogenic clinical isolate demonstrated increased viability during starvation in saline. Our study suggests that quinolone-resistant uropathogenic strains are highly adaptable clones of E. coli, which can exhibit compensatory viability potential under unfavorable conditions. The clinical occurrence of such phenotypes is likely to contribute to the survival, persistence and spread strategy of resistant bacteria.     

Antimicrobial‐resistant faecal Escherichia coli in wild mammals in central Europe: multiresistant Escherichia coli producing extended‐spectrum beta‐lactamases in wild boars

Aims: To determine the presence of antibiotic‐resistant faecal Escherichia coli in populations of wild mammals in the Czech Republic and Slovakia. Methods and Results: Rectal swabs or faeces collected during 2006–2008 from wild mammals were spread on MacConkey agar and MacConkey agar containing 2 mg l^?1 of cefotaxime. From plates with positive growth, one isolate was recovered and identified as E. coli. Susceptibility to 12 antibiotics was tested using the disk diffusion method. Resistance genes, class 1 and 2 integrons and gene cassettes were detected in resistant isolates by polymerase chain reaction (PCR). Extended‐spectrum beta‐lactamases (ESBL) were further characterized by DNA sequencing, macrorestriction profiling and determination of plasmid sizes. Plasmid DNA was subjected to EcoRV digestion, transferability by conjugation and incompatibility grouping by multiplex PCR. The prevalence of resistant isolates was 2% in small terrestrial mammals (rodents and insectivores, n_E. coli = 242), 12% in wild ruminants and foxes (n_E. coli = 42), while no resistant isolates were detected in brown bears (n_E. coli = 16). In wild boars (Sus scrofa) (n_E. coli = 290), the prevalence of resistant isolates was 6%. Class 1 and 2 integrons with various gene cassettes were recorded in resistant isolates. From wild boars, five (2%, n_{rectal smears} = 293) multiresistant isolates producing ESBL were recovered: one isolate with bla_CTX‐M‐1 + bla_TEM‐1, three with bla_CTX‐M‐1 and one with bla_TEM‐52b. The bla_CTX‐M‐1 genes were carried on approx. 90 kb IncI1 conjugative plasmids. Conclusions: Antibiotic‐resistant E. coli occured in populations of wild mammals in various prevalences. Significance and Impact of the Study: Wild mammals are reservoirs of antibiotic‐resistant E. coli including ESBL‐producing strains which were found in wild boars.     

Antimicrobial susceptibility and molecular characterization of <Emphasis Type="Italic">Vibrio cholerae</Emphasis> from cholera outbreaks in Chennai

The genotype and antibiotic resistance pattern of the toxigenic Vibrio cholerae strains associated with cholera outbreaks vary frequently. Fifty-one V. cholerae strains isolated from cholera outbreaks in Chennai (2002–2005) were screened for the presence of virulence and regulatory genes by multiplex polymerase chain reaction (PCR) assay. Genotyping of the isolates was done by VC1 primers derived from enterobacterial repetitive intergenic consensus (ERIC)-related sequence in V. cholerae. All the isolates possessed toxigenic genes, such as ctxA, ctxB, tcpA, ace, ompU, toxR and zot. Two different El Tor genotypes and one O139 genotype could be delineated by VC1-PCR. One of the El Tor genotypes was similar to the El Tor strains isolated from Bhind district and Delhi during 2004. Antibiotic susceptibility testing revealed greater variability among the isolates tested. All the isolates were found to be susceptible to norfloxacin, ciprofloxacin and tetracycline. Thiry-three per cent of the isolates were found to be resistant to more than 4 antibiotics and could be termed as multiple antibiotic resistant. Coexistence of O139 serogroup along with the El Tor biotype could be identified among the strains recovered during the period 2002–2004. The O139 isolates were found to be more susceptible to the antibiotics tested when compared to the El Tor isolates.     

Diarrheagenic <Emphasis Type="Italic">Escherichia coli</Emphasis> Strains Recovered from Urban Pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>) in Brazil and Their Antimicrobial Susceptibility Patterns

Urban pigeons (Columba livia) come into close contact with humans and animals, and may contribute to the spread of infectious agents. These may include human pathogens such as diarrheagenic Escherichia coli strains, which are able to survive in pigeon feces, thus creating potential for human exposure and infection. Our objectives were to determine the occurrence of diarrheagenic E. coli strains in fresh feces from urban pigeons and their drug susceptibility patterns. E. coli strains were isolated from 100 fresh feces samples and presumptive phenotypic species identification was carried out, confirmed by amplification of specific 16S ribosomal RNA encoding DNA. Multiplex PCR was performed to characterize pathogenic strains. Drug susceptibility patterns were determined by the agar dilution method. Enteroinvasive E. coli, Shiga toxin-producing E. coli, enteropathogenic E. coli, and enterotoxigenic E. coli were detected at an overall rate of 12.1%. Among the isolated E. coli strains, 62.1% were susceptible to all tested drugs, whereas 37.9% were resistant to at least one of the antimicrobials tested. Amikacin was the less effective drug (36.8% resistance), followed by ampicillin (7.8%). No resistance was detected to gentamicin, ceftriaxone, and ceftazidime and almost all the isolates were susceptible to ampicillin-sulbactam (98.4%), levofloxacin (97.8%), and trimethoprim-sulfametoxazole (96.1%). Since these pigeons may harbor multidrug-resistant pathogens, their presence in an urban environment could be an important component of infection spread, with impact on public health.