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.     

Whole-genome sequencing and gene sharing network analysis powered by machine learning identifies antibiotic resistance sharing between animals,humans and environment in livestock farming

Anthropogenic environments such as those created by intensive farming of livestock, have been proposed to provide ideal selection pressure for the emergence of antimicrobial-resistant Escherichia coli bacteria and antimicrobial resistance genes (ARGs) and spread to humans. Here, we performed a longitudinal study in a large-scale commercial poultry farm in China, collecting E. coli isolates from both farm and slaughterhouse; targeting animals, carcasses, workers and their households and environment. By using whole-genome phylogenetic analysis and network analysis based on single nucleotide polymorphisms (SNPs), we found highly interrelated non-pathogenic and pathogenic E. coli strains with phylogenetic intermixing, and a high prevalence of shared multidrug resistance profiles amongst livestock, human and environment. Through an original data processing pipeline which combines omics, machine learning, gene sharing network and mobile genetic elements analysis, we investigated the resistance to 26 different antimicrobials and identified 361 genes associated to antimicrobial resistance (AMR) phenotypes; 58 of these were known AMR-associated genes and 35 were associated to multidrug resistance. We uncovered an extensive network of genes, correlated to AMR phenotypes, shared among livestock, humans, farm and slaughterhouse environments. We also found several human, livestock and environmental isolates sharing closely related mobile genetic elements carrying ARGs across host species and environments. In a scenario where no consensus exists on how antibiotic use in the livestock may affect antibiotic resistance in the human population, our findings provide novel insights into the broader epidemiology of antimicrobial resistance in livestock farming. Moreover, our original data analysis method has the potential to uncover AMR transmission pathways when applied to the study of other pathogens active in other anthropogenic environments characterised by complex interconnections between host species.     

Detection of Extended-Spectrum Beta-Lactamase (ESBL)-Producing Escherichia coli on Flies at Poultry Farms

In the Netherlands, extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli bacteria are highly prevalent in poultry, and chicken meat has been implicated as a source of ESBL-producing E. coli present in the human population. The current study describes the isolation of ESBL-producing E. coli from house flies and blow flies caught at two poultry farms, offering a potential alternative route of transmission of ESBL-producing E. coli from poultry to humans. Overall, 87 flies were analyzed in 19 pools. ESBL-producing E. coli bacteria were detected in two fly pools (10.5%): a pool of three blow flies from a broiler farm and a pool of eight house flies from a laying-hen farm. From each positive fly pool, six isolates were characterized and compared with isolates obtained from manure (n = 53) sampled at both farms and rinse water (n = 10) from the broiler farm. Among six fly isolates from the broiler farm, four different types were detected with respect to phylogenetic group, sequence type (ST), and ESBL genotype: A₀/ST3519/SHV-12, A₁/ST10/SHV-12, A₁/ST58/SHV-12, and B1/ST448/CTX-M-1. These types, as well as six additional types, were also present in manure and/or rinse water at the same farm. At the laying-hen farm, all fly and manure isolates were identical, carrying bla_TEM-52 in an A₁/ST48 genetic background. The data imply that flies acquire ESBL-producing E. coli at poultry farms, warranting further evaluation of the contribution of flies to dissemination of ESBL-producing E. coli in the community.     

Multi‐locus sequence types of Campylobacter carried by flies and slugs acquired from local ruminant faeces

Aims: To assess whether flies and slugs acquire strains of Campylobacter jejuni and Campylobacter coli present in local ruminant faeces. Methods and Results: Campylobacter was cultured from flies, slugs and ruminant faeces that were collected from a single farm in Scotland over a 19‐week period. The isolates were typed using multi‐locus sequence typing (MLST) and compared with isolates from cattle and sheep faeces. Campylobacter jejuni and Camp. coli were isolated from 5·8% (n = 155, average of 75 flies per pool) and 13·3% (n = 15, average of 8·5 slugs per pool) of pooled fly and slug samples, respectively. The most common sequence type (ST) in flies was Camp. coli ST‐962 (approx. 40%) regardless of the prevalence in local cattle (2·3%) or sheep (25·0%) faeces. Two positive slug pools generated the same ST that has not been reported elsewhere. Conclusions: Despite their low carriage rate, flies are able to acquire Campylobacter STs that are locally present, although the subset carried may be biased when compared to local source. Slugs were shown to carry a previously unreported Campylobacter ST. Significance and Impact of the Study: This study has demonstrated that flies carry viable Campylobacter and may contribute to the transfer of STs within and between groups of animals on farms. Further, they may therefore present a risk to human health via their contact with ready‐to‐eat foods or surfaces.     

Occurrence of verocytotoxin-producing <Emphasis Type="Italic">Escherichia coli</Emphasis> in the faeces of free-ranging wild lagomorphs in southwest Spain

Verocytotoxin-producing Escherichia coli (VTEC) is an important group of emerging food-borne pathogens and represents a major public health concern worldwide. The aim of this work was to analyse faecal samples from hunted wild lagomorphs for the presence of E. coli O157:H7 and non-O157 VTEC. During two hunting seasons, faecal samples from 241 animals were collected, including wild rabbit (Oryctolagus cuniculus) and hare (Lepus granatensis) and were examined for VTEC. Overall, VTEC were detected and isolated in four (1.66%) of the 241 animals sampled. E. coli O157:H7 was isolated only from one of 124 (0.81%) wild rabbit faecal samples while non-O157 VTEC were isolated from two of 124 (1.61%) wild rabbit faecal samples and one of 117 (0.85%) hare faecal samples. VTEC isolates obtained in the present study (four in total) belonged to four different O:H serotypes, including two serotypes (O84:H− and O157:H7) previously associated with human infection and in particular with causing the life-threatening haemolytic–uraemic syndrome. Although these results indicate a low prevalence of VTEC infection in free-ranging wild lagomorphs, they may play an important role as a source of exposure to human beings and livestock and as a vehicle for dispersing these pathogens. These findings have implications for the zoonotic risk to hunters, people consuming meat from wild animals and others in contact with wild animal faeces, and also in the development of programmes for controlling VTEC at the farm level.     

Occurrence of ESBL-Producing Escherichia coli in Livestock and Farm Workers in Mecklenburg-Western Pomerania,Germany

In recent years, extended-spectrum β-lactamases (ESBL) producing bacteria have been found in livestock, mainly as asymptomatic colonizers. The zoonotic risk for people working in close contact to animal husbandry has still not been completely assessed. Therefore, we investigated the prevalence of ESBL-producing Escherichia spp. in livestock animals and workers to determine the potential risk for an animal-human cross-transmission.In Mecklenburg-Western Pomerania, northeast Germany, inguinal swabs of 73 individuals with livestock contact from 23 different farms were tested for ESBL-producing Escherichia spp. Two pooled fecal samples per farm of animal origin from 34 different farms (17 pig farms, 11 cattle farms, 6 poultry farms) as well as cloacal swabs of 10 randomly selected broilers or turkeys were taken at each poultry farm. For identification, selective chromogenic agar was used after an enrichment step. Phenotypically ESBL-producing isolates (n = 99) were tested for CTX-M, OXA, SHV and TEM using PCR, and isolates were further characterized using multilocus sequence typing (MLST). In total, 61 diverse isolates from different sources and/or different MLST/PCR results were acquired. Five farm workers (three from cattle farms and two from pig farms) harbored ESBL-producing E. coli. All human isolates harbored the CTX-M β-lactamase; TEM and OXA β-lactamases were additionally detected in two, resp. one, isolates. ESBL-producing Escherichia spp. were found in fecal samples at pig (15/17), cattle (6/11) and poultry farms (3/6). In total, 70.6% (24/36) of the tested farms were ESBL positive. Furthermore, 9 out of 60 cloacal swabs turned out to be ESBL positive. All isolated ESBL-producing bacteria from animal sources were E. coli, except for one E. hermanii isolate. CTX-M was the most prevalent β-lactamase at cattle and pig farms, while SHV predominated in poultry. One human isolate shared an identical MLST sequence type (ST) 3891 and CTX-M allele to the isolate found in the cattle fecal sample from the same farm, indicating a zoonotic transfer. Two other pairs of human-pig and human-cattle E. coli isolates encoded the same ESBL genes but did not share the same MLST ST, which may indicate horizontal resistance gene transfer. In summary, the study shows the high prevalence of ESBL-producing E.coli in livestock in Mecklenburg- Western Pomerania and provides the risk of transfer between livestock and farm workers.     

Patterns of Antimicrobial Resistance Observed in Escherichia coli Isolates Obtained from Domestic- and Wild-Animal Fecal Samples, Human Septage, and Surface Water

A repeated cross-sectional study was conducted to determine the patterns of antimicrobial resistance in 1,286 Escherichia coli strains isolated from human septage, wildlife, domestic animals, farm environments, and surface water in the Red Cedar watershed in Michigan. Isolation and identification of E. coli were done by using enrichment media, selective media, and biochemical tests. Antimicrobial susceptibility testing by the disk diffusion method was conducted for neomycin, gentamicin, streptomycin, chloramphenicol, ofloxacin, trimethoprim-sulfamethoxazole, tetracycline, ampicillin, nalidixic acid, nitrofurantoin, cephalothin, and sulfisoxazole. Resistance to at least one antimicrobial agent was demonstrated in isolates from livestock, companion animals, human septage, wildlife, and surface water. In general, E. coli isolates from domestic species showed resistance to the largest number of antimicrobial agents compared to isolates from human septage, wildlife, and surface water. The agents to which resistance was demonstrated most frequently were tetracycline, cephalothin, sulfisoxazole, and streptomycin. There were similarities in the patterns of resistance in fecal samples and farm environment samples by animal, and the levels of cephalothin-resistant isolates were higher in farm environment samples than in fecal samples. Multidrug resistance was seen in a variety of sources, and the highest levels of multidrug-resistant E. coli were observed for swine fecal samples. The fact that water sample isolates were resistant only to cephalothin may suggest that the resistance patterns for farm environment samples may be more representative of the risk of contamination of surface waters with antimicrobial agent-resistant bacteria.     

Agricultural fertilization with poultry manure results in persistent environmental contamination with the pathogen Clostridioides difficile

During a field experiment applying broiler manure for fertilization of agricultural land, we detected viable Clostridioides (also known as Clostridium) difficile in broiler faeces, manure, dust and fertilized soil. A large diversity of toxigenic C. difficile isolates was recovered, including PCR ribotypes common from human disease. Genomic relatedness of C. difficile isolates from dust and from soil, recovered more than 2 years after fertilization, traced their origins to the specific chicken farm that had delivered the manure. We present evidence of long-term contamination of agricultural soil with manure-derived C. difficile and demonstrate the potential for airborne dispersal of C. difficile through dust emissions during manure application. Clostridioides genome sequences virtually identical to those from manure had been recovered from chicken meat and from human infections in previous studies, suggesting broiler-associated C. difficile are capable of zoonotic transmission.     

Multiple‐locus variable‐nucleotide tandem repeat subtype analysis implicates European starlings as biological vectors for Escherichia coli O157:H7 in Ohio,USA

Aims: To provide molecular epidemiological evidence of avian transmission of Escherichia coli O157:H7 between dairy farms in Ohio, this study was designed to identify genetic relatedness between isolates originating from bovine faecal samples and intestinal contents of European starlings captured on these farms. Methods and Results: During a three‐year period (2007–2009), cattle (n = 9000) and starlings (n = 430) on 150 different dairy farms in northern Ohio were sampled for the presence of E. coli O157:H7. Isolates were subjected to multiple‐locus variable‐nucleotide tandem repeat analysis (MLVA). Distinct allelic groups were identified on most farms; however, isolates clustering into three MLVA groups originated from both cattle and birds on different farms. Conclusions: Sharing of indistinguishable epidemiologically linked E. coli O157 MLVA subtypes between starlings and cattle on different farms supports the hypothesis that these birds contribute to the transmission of E. coli O157:H7 between dairy farms. Significance and Impact of Study: A continued need exists to identify and to improve preharvest measures for controlling E. coli O157:H7. Controlling wildlife intrusion, particularly European starlings, on livestock operations, may be an important strategy for reducing dissemination of E. coli O157:H7 between farms and thereby potentially decreasing the on‐farm prevalence of E. coli O157:H7 and enhancing the safety of the food supply.     

A survey of fluoroquinolone resistance in Escherichia coli and thermophilic Campylobacter spp. on poultry and pig farms in Great Britain

Aims: To estimate the proportions of farms on which broilers, turkeys and pigs were shedding fluoroquinolone (FQ)-resistant Escherichia coli or Campylobacter spp. near to slaughter. Methods and Results: Freshly voided faeces were collected on 89 poultry and 108 pig farms and cultured with media containing 1·0 mg l⁻¹ ciprofloxacin. Studies demonstrated the specificity of this sensitive method, and both poultry and pig sampling yielded FQ-resistant E. coli on 60% of farms. FQ-resistant Campylobacter spp. were found on around 22% of poultry and 75% of pig farms. The majority of resistant isolates of Campylobacter (89%) and E. coli (96%) tested had minimum inhibitory concentrations for ciprofloxacin of ≥8 mg l⁻¹. The proportion of resistant E. coli and Campylobacter organisms within samples varied widely. Conclusions: FQ resistance is commonly present among two enteric bacterial genera prevalent on pig and poultry farms, although the low proportion of resistant organisms in many cases requires a sensitive detection technique. Significance and Impact of the Study: FQ-resistant bacteria with zoonotic potential appear to be present on a high proportion of UK pig and poultry farms. The risk this poses to consumers relative to other causes of FQ-resistant human infections remains to be clarified.     

Moderate Prevalence of Antimicrobial Resistance in Escherichia coli Isolates from Lettuce,Irrigation Water,and Soil

Fresh produce is known to carry nonpathogenic epiphytic microorganisms. During agricultural production and harvesting, leafy greens can become contaminated with antibiotic-resistant pathogens or commensals from animal and human sources. As lettuce does not undergo any inactivation or preservation treatment during processing, consumers may be exposed directly to all of the (resistant) bacteria present. In this study, we investigated whether lettuce or its production environment (irrigation water, soil) is able to act as a vector or reservoir of antimicrobial-resistant Escherichia coli. Over a 1-year period, eight lettuce farms were visited multiple times and 738 samples, including lettuce seedlings (leaves and soil), soil, irrigation water, and lettuce leaves were collected. From these samples, 473 isolates of Escherichia coli were obtained and tested for resistance to 14 antimicrobials. Fifty-four isolates (11.4%) were resistant to one or more antimicrobials. The highest resistance rate was observed for ampicillin (7%), followed by cephalothin, amoxicillin-clavulanic acid, tetracycline, trimethoprim, and streptomycin, with resistance rates between 4.4 and 3.6%. No resistance to amikacin, ciprofloxacin, gentamicin, or kanamycin was observed. One isolate was resistant to cefotaxime. Among the multiresistant isolates (n = 37), ampicillin and cephalothin showed the highest resistance rates, at 76 and 52%, respectively. E. coli isolates from lettuce showed higher resistance rates than E. coli isolates obtained from soil or irrigation water samples. When the presence of resistance in E. coli isolates from lettuce production sites and their resistance patterns were compared with the profiles of animal-derived E. coli strains, they were found to be the most comparable with what is found in the cattle reservoir. This may suggest that cattle are a potential reservoir of antimicrobial-resistant E. coli strains in plant primary production.     

Grazing intensity is a poor indicator of waterborne Escherichia coli O157 activity

Contamination of watercourses with fecal matter represents a significant risk to public health due to the associated risk from human pathogens (e.g. Escherichia coli O157, norovirus). In addition, water contamination may also perpetuate the re-infection cycle of human pathogens within domesticated and wild animal populations. While diffuse pollution from agricultural fields has been identified as a major source of these pathogens, the relationship between livestock grazing intensity and subsequent pathogen persistence in water is not well established. Our aim was to critically evaluate the importance of land use management on the activity of E. coli O157 in freshwaters collected from a livestock dominated catchment in the UK. We inoculated replicate batches of both filter-sterilised and non-sterile freshwaters with a chromosomally lux-marked E. coli O157 and monitored pathogen survival and activity over a 5 d period. Our results indicate that the greatest risk for pathogens entering freshwater is probably associated with high intensity livestock areas, although their subsequent survival is greatest in waters from low intensity livestock areas. We ascribe this enhanced persistence in the latter to reduced competition and predation within these aquatic environments. These results have serious implications for the reliability of pathogen risk exposure maps which are based on grazing intensity alone.     

Extraintestinal Pathogenic and Antimicrobial-Resistant Escherichia coli Contamination of 56 Public Restrooms in the Greater Minneapolis-St. Paul Metropolitan Area

How extraintestinal pathogenic Escherichia coli (ExPEC) and antimicrobial-resistant E. coli disseminate through the population is undefined. We studied public restrooms for contamination with E. coli and ExPEC in relation to source and extensively characterized the E. coli isolates. For this, we cultured 1,120 environmental samples from 56 public restrooms in 33 establishments (obtained from 10 cities in the greater Minneapolis-St. Paul, MN, metropolitan area in 2003) for E. coli and compared ecological data with culture results. Isolates underwent virulence genotyping, phylotyping, clonal typing, pulsed-field gel electrophoresis (PFGE), and disk diffusion antimicrobial susceptibility testing. Overall, 168 samples (15% from 89% of restrooms) fluoresced, indicating presumptive E. coli: 25 samples (2.2% from 32% of restrooms) yielded E. coli isolates, and 10 samples (0.9% from 16% of restrooms) contained ExPEC. Restroom category and cleanliness level significantly predicted only fluorescence, gender predicted fluorescence and E. coli, and feces-like material and toilet-associated sites predicted all three endpoints. Of the 25 E. coli isolates, 7 (28%) were from phylogenetic group B2(virulence-associated), and 8 (32%) were ExPEC. ExPEC isolates more commonly represented group B2 (50% versus 18%) and had significantly higher virulence gene scores than non-ExPEC isolates. Six isolates (24%) exhibited ≥3-class antibiotic resistance, 10 (40%) represented classic human-associated sequence types, and one closely resembled reference human clinical isolates by pulsed-field gel electrophoresis. Thus, E. coli, ExPEC, and antimicrobial-resistant E. coli sporadically contaminate public restrooms, in ways corresponding with restroom characteristics and within-restroom sites. Such restroom-source E. coli strains likely reflect human fecal contamination, may pose a health threat, and may contribute to population-wide dissemination of such strains.     

Houseflies (Musca domestica) as Vectors for Extended-Spectrum β-Lactamase-Producing Escherichia coli on Spanish Broiler Farms

Flies may act as potential vectors for the spread of resistant bacteria to different environments. This study was intended to evaluate the presence of Escherichia coli strains resistant to cephalosporins in flies captured in the areas surrounding five broiler farms. Phenotypic and molecular characterization of the resistant population was performed by different methods: MIC determination, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and phylotyping. The presence of extended-spectrum beta-lactamase (ESBL) genes, their plasmid location, and the mobile genetic elements involved in their mobilization were studied. Additionally, the presence of 35 genes associated with virulence was evaluated. Out of 682 flies captured, 42 yielded ESBL-producing E. coli. Of these isolates, 23 contained bla_CTX-M-1, 18 contained bla_CTX-M-14, and 1 contained bla_CTX-M-9. ESBL genes were associated mainly with the presence of the IncI1 and IncFIB replicons. Additionally, all the strains were multiresistant, and five of them also harbored qnrS. Identical PFGE profiles were found for E. coli isolates obtained from flies at different sampling times, indicating a persistence of the same clones in the farm environment over months. According to their virulence genes, 81% of the isolates were considered avian-pathogenic E. coli (APEC) and 29% were considered extraintestinal pathogenic E. coli (ExPEC). The entrance of flies into broiler houses constitutes a considerable risk for colonization of broilers with multidrug-resistant E. coli. ESBLs in flies reflect the contamination status of the farm environment. Additionally, this study demonstrates the potential contribution of flies to the dissemination of virulence and resistance genes into different ecological niches.     

Shiga Toxin 2e-Producing Escherichia coli Isolates from Humans and Pigs Differ in Their Virulence Profiles and Interactions with Intestinal Epithelial Cells

Thirteen Escherichia coli strains harboring stx_2e were isolated from 11,056 human stools. This frequency corresponded to the presence of the stx_2e allele in 1.7% of all Shiga toxin-producing E. coli (STEC) strains. The strains harboring stx_2e were associated with mild diarrhea (n = 9) or asymptomatic infections (n = 4). Because STEC isolates possessing stx_2e are porcine pathogens, we compared the human STEC isolates with stx_2e-harboring E. coli isolated from piglets with edema disease and postweaning diarrhea. All pig isolates possessed the gene encoding the F18 adhesin, and the majority possessed adhesin involved in diffuse adherence; these adhesins were absent from all the human STEC isolates. In contrast, the high-pathogenicity island encoding an iron uptake system was found only in human isolates. Host-specific patterns of interaction with intestinal epithelial cells were observed. All human isolates adhered to human intestinal epithelial cell lines T84 and HCT-8 but not to pig intestinal epithelial cell line IPEC-J2. In contrast, the pig isolates completely lysed human epithelial cells but not IPEC-J2 cells, to which most of them adhered. Our data demonstrate that E. coli isolates producing Shiga toxin 2e have imported specific virulence and fitness determinants which allow them to adapt to the specific hosts in which they cause various forms of disease.     

Zoonotic Enterobacterial Pathogens Detected in Wild Chimpanzees

Infectious diseases including those acquired through direct or indirect contact with people and livestock threaten the survival of wild great apes. Few studies have reported enterobacterial pathogens in chimpanzees. We used multiplex PCR to screen faeces of chimpanzees sharing a landscape with villagers and livestock in Bulindi, Uganda for Salmonella spp., enterohemorrhagic Escherichia coli (E. coli) and Shigella spp./enteroinvasive E. coli. All three potentially zoonotic pathogens were detected. Individual prevalence ranged between 7 and 20%, with most infections observed in mature male chimpanzees. These preliminary findings suggest detailed investigation of enterobacterial infections in people, primates and livestock in this ecosystem is warranted.     

Genetic diversity and population structure of <Emphasis Type="Italic">Escherichia coli</Emphasis> from neighboring small-scale dairy farms

The genetic diversity and population structure of Escherichia coli isolates from small-scale dairy farms were used to assess the ability of E. coli to spread within the farm environment and between neighboring farms. A total of 164 E. coli isolates were obtained from bovine feces, bedding, cow teats and milk from 6 small-scale dairy farms. Ward’s clustering grouped the isolates into 54 different random amplified polymorphic DNA (RAPD) types at 95% similarity, regardless of either the sample type or the farm of isolation. This suggests that RAPD types are shared between bovine feces, bedding, cow teats, and milk. In addition, transmission of RAPD types between the studied farms was suggested by the Ward grouping pattern of the isolates, Nei’s and AMOVA population analyses, and genetic landscape shape analysis. For the first time, the latter analytical tool was used to assess the ability of E. coli to disseminate between small-scale dairy farms within the same producing region. Although a number of dispersal mechanisms could exist between farms, the genetic landscape shape analysis associated the flow of E. coli RAPD types with the movement of forage and milking staff between farms. This study will aid in planning disease prevention strategies and optimizing husbandry practices.     

Antimicrobial Resistance in Escherichia coli Isolates from Swine and Wild Small Mammals in the Proximity of Swine Farms and in Natural Environments in Ontario, Canada

Wild animals not normally exposed to antimicrobial agents can acquire antimicrobial agent-resistant bacteria through contact with humans and domestic animals and through the environment. In this study we assessed the frequency of antimicrobial resistance in generic Escherichia coli isolates from wild small mammals (mice, voles, and shrews) and the effect of their habitat (farm or natural area) on antimicrobial resistance. Additionally, we compared the types and frequency of antimicrobial resistance in E. coli isolates from swine on the same farms from which wild small mammals were collected. Animals residing in the vicinity of farms were five times more likely to carry E. coli isolates with tetracycline resistance determinants than animals living in natural areas; resistance to tetracycline was also the most frequently observed resistance in isolates recovered from swine (83%). Our results suggest that E. coli isolates from wild small mammals living on farms have higher rates of resistance and are more frequently multiresistant than E. coli isolates from environments, such as natural areas, that are less impacted by human and agricultural activities. No Salmonella isolates were recovered from any of the wild small mammal feces. This study suggests that close proximity to food animal agriculture increases the likelihood that E. coli isolates from wild animals are resistant to some antimicrobials, possibly due to exposure to resistant E. coli isolates from livestock, to the resistance genes of these isolates, or to antimicrobials through contact with animal feed.     

Verocytotoxin-Producing Escherichia coli in Wild Birds and Rodents in Close Proximity to Farms

Wild animals living close to cattle and pig farms (four each) were examined for verocytotoxin-producing Escherichia coli (VTEC; also known as Shiga toxin-producing E. coli). The prevalence of VTEC among the 260 samples from wild animals was generally low. However, VTEC isolates from a starling (Sturnus vulgaris) and a Norway rat (Rattus norvegicus) were identical to cattle isolates from the corresponding farms with respect to serotype, virulence profile, and pulsed-field gel electrophoresis type. This study shows that wild birds and rodents may become infected from farm animals or vice versa, suggesting a possible role in VTEC transmission.     

<Emphasis Type="Italic">Escherichia coli</Emphasis> Diversity in Livestock Manures and Agriculturally Impacted Stream Waters

Escherichia coli (E. coli) isolate diversity enhances the likelihood of survival, spread, and/or transmission of the organism among environments. Understanding the ecology of this important organism is requisite for development of more accurate protocols for monitoring and regulatory purposes. In this study, E. coli diversity, gene profiles and transport properties of isolates from different livestock and water sources were evaluated. Strain diversity was evaluated by BOX-PCR, phylotyping, and profiling for 15 genes associated with adhesion, toxin production, iron acquisition or capsular synthesis. Attachment efficiencies were calculated for 17 isolates following transport through saturated porous media. Richness of genotype profiles for livestock isolates was relatively low (25, 12, and 11 for swine, poultry and dairy, respectively) compared to those from stream-water (115 and 126 from dry or wet weather events, respectively). Attachment efficiencies varied by an order of magnitude (0.039–0.44) and the isolate with the highest attachment efficiency possessed the largest suite of targeted genes including those for adherence (iha, agn43, and fimH), surface exclusion (traT) and the siderophore iroN _E.coli . Variation in E. coli isolates based on temporal and ecological source was found to translate to equally broad ranges in transport efficiency underscoring the large degree of genotypic and phenotypic variation that exists among E. coli isolates. The impact of this diversity on genetic exchange and the concomitant effect on the organisms’ fate and transport under in situ environmental conditions warrant further investigation. These factors also require careful consideration for purposes of modeling, source tracking, and risk assessment.