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Antimicrobial resistance in E. coli isolated from lettuce, irrigation water and soil

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Abstract
Introduction: Fresh vegetables normally carry natural non-pathogenic epiphytic microorganisms, but during growth, and harvest, the produce might become contaminated with antibiotic resistant pathogens or commensals from animal and human sources. The contamination of produce by resistant bacteria can occur in the field by contaminated soil, by exposure to contaminated water (such as crop irrigation, application of pesticides or flooding) or by deposition of feces by livestock or wild animals. In this study was investigated whether lettuce or its production environment (irrigation water, soil) was able to act as a vector or reservoir of antimicrobial resistant E. coli. Materials and Methods: Over a one year period, eight lettuce farms were visited on multiple times and a total of 738 samples among which lettuce seedlings (leaves and soil), soil, irrigation water and lettuce crops were collected. From these samples, 473 isolates of Escherichia coli were obtained and tested for resistance against 14 antimicrobials. Results: A total of 54 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 was observed for amikacin, ciprofloxacin, gentamicin and kanamycin. One isolate showed resistance for cefotaxim. Among the multi-resistant isolates (n = 37), ampicillin and cephalothin showed the highest resistance rate, respectively 76 % and 52 %. The E. coli isolated from the lettuce showed higher resistance rates compared to E. coli isolates obtained from the soil or irrigation water samples. Discussion: Because fresh produce (such as lettuce) is directly consumed without further microbial inactivation treatment, it may directly contribute to the human exposure of antimicrobial resistant bacteria. The study emphasizes the need for ‘good agricultural practices’ to keep the fecal contamination and E. coli levels low and thus not only reducing the probability of exposure to human zoonotic pathogens but also to the exposure of antimicrobial resistant commensal E. coli. The percentage of multi-resistance to antibiotics occurring among the E. coli isolates in the present study was lower compared to other publications involving E. coli isolates from a variety of animal species (Casteleyn et al., 2006; Persoons et al., 2010). The antimicrobial resistance patterns suggested cattle as the main source for commensal resistant E. coli contamination as the presence of resistance and resistance patterns with animal profiles were the most comparable with what is found in cattle.
Keywords
antimicrobial resistance, E. coli, lettuce

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Chicago
Holvoet, Kevin, Imca Sampers, Benedicte Callens, Jeroen Dewulf, and Mieke Uyttendaele. 2013. “Antimicrobial Resistance in E. Coli Isolated from Lettuce, Irrigation Water and Soil.” In Food Microbiology, 18th Conference, Abstracts. Belgian Society for Food Microbiology (BSFM).
APA
Holvoet, Kevin, Sampers, I., Callens, B., Dewulf, J., & Uyttendaele, M. (2013). Antimicrobial resistance in E. coli isolated from lettuce, irrigation water and soil. Food Microbiology, 18th Conference, Abstracts. Presented at the 18th Conference on Food Microbiology, Belgian Society for Food Microbiology (BSFM).
Vancouver
1.
Holvoet K, Sampers I, Callens B, Dewulf J, Uyttendaele M. Antimicrobial resistance in E. coli isolated from lettuce, irrigation water and soil. Food Microbiology, 18th Conference, Abstracts. Belgian Society for Food Microbiology (BSFM); 2013.
MLA
Holvoet, Kevin, Imca Sampers, Benedicte Callens, et al. “Antimicrobial Resistance in E. Coli Isolated from Lettuce, Irrigation Water and Soil.” Food Microbiology, 18th Conference, Abstracts. Belgian Society for Food Microbiology (BSFM), 2013. Print.
@inproceedings{4147562,
  abstract     = {Introduction: Fresh vegetables normally carry natural non-pathogenic epiphytic microorganisms, but during growth, and harvest, the produce might become contaminated with antibiotic resistant pathogens or commensals from animal and human sources. The contamination of produce by resistant bacteria can occur in the field by contaminated soil, by exposure to contaminated water (such as crop irrigation, application of pesticides or flooding) or by deposition of feces by livestock or wild animals. In this study was investigated whether lettuce or its production environment (irrigation water, soil) was able to act as a vector or reservoir of antimicrobial resistant E. coli.
Materials and Methods: Over a one year period, eight lettuce farms were visited on multiple times and a total of 738 samples among which lettuce seedlings (leaves and soil), soil, irrigation water and lettuce crops were collected. From these samples, 473 isolates of Escherichia coli were obtained and tested for resistance against 14 antimicrobials.
Results: A total of 54 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 was observed for amikacin, ciprofloxacin, gentamicin and kanamycin. One isolate showed resistance for cefotaxim. Among the multi-resistant isolates (n = 37), ampicillin and cephalothin showed the highest resistance rate, respectively 76 \% and 52 \%. The E. coli  isolated from the lettuce showed higher resistance rates compared to E. coli isolates obtained from the soil or irrigation water samples. 
Discussion: Because fresh produce (such as lettuce) is directly consumed without further microbial inactivation treatment, it may directly contribute to the human exposure of antimicrobial resistant bacteria. The study emphasizes the need for {\textquoteleft}good agricultural practices{\textquoteright} to keep the fecal contamination and E. coli levels low and thus not only reducing the probability of exposure to human zoonotic pathogens but also to the exposure of antimicrobial resistant commensal E. coli.  
The percentage of multi-resistance to antibiotics occurring among the E. coli isolates in the present study was lower compared to other publications involving E. coli isolates from a variety of animal species (Casteleyn et al., 2006; Persoons et al., 2010). The antimicrobial resistance patterns suggested cattle as the main source for commensal resistant E. coli contamination as the presence of resistance and resistance patterns with animal profiles were the most comparable with what is found in cattle.},
  author       = {Holvoet, Kevin and Sampers, Imca and Callens, Benedicte and Dewulf, Jeroen and Uyttendaele, Mieke},
  booktitle    = {Food Microbiology, 18th Conference, Abstracts},
  keyword      = {antimicrobial resistance,E. coli,lettuce},
  language     = {eng},
  location     = {Brussels, Belgium},
  publisher    = {Belgian Society for Food Microbiology (BSFM)},
  title        = {Antimicrobial resistance in E. coli isolated from lettuce, irrigation water and soil},
  year         = {2013},
}