Abstract
Enterococcus spp. from two poultry farms and proximate surface and ground water sites in an area of intensive poultry production were tested for resistance to 16 clinical antibiotics. Resistance patterns were compared to assess trends and possible correlations for specific antimicrobials and levels of resistance. Enterococci were detected at all 12 surface water sites and three of 28 ground water sites. Resistance to lincomycin, tetracycline, penicillin and ciprofloxacin in poultry litter isolates was high (80.3%, 65.3%, 61.1% and 49.6%, respectively). Resistance in the surface water to the same antibiotics was 87.1%, 24.1%, 7.6% and 12.9%, respectively. Overall, 86% of litter isolates, 58% of surface water isolates and 100% of ground water isolates were resistant to more than one antibiotic. Fifty-four different resistance patterns were recognised in isolates obtained from litter and environmental samples and several E. faecium and E. faecalis isolates from litter and environment samples shared the same resistance pattern. Multiple antibiotic resistant (MAR) indices calculated to assess health risks due to the presence of resistant enterococci suggested an increased presence of antibiotics in surface water, likely from poultry sources as no other wastewater contributions in the area were documented.
Highlights
Microbial contamination of water bodies due to municipal wastewater plants and animal operations is recognized as a growing issue
E. casseliflavus, E. gallinarum, E. hirae and E. durans were isolated from the poultry litter samples in this study, which is consistent with the literature, in that they are generally regarded as animal-derived strains, found in the gastrointestinal tract of poultry [31,32]
This study confirmed the presence of resistant enterococci species in the environment, surface and ground water
Summary
Microbial contamination of water bodies due to municipal wastewater plants and animal operations is recognized as a growing issue. Wastewater and animal waste are reservoirs of antibiotic-resistance genes and multiple antibiotic-resistant (MAR, defined as resistance to at least two antimicrobials) pathogenic bacteria that pose a threat to human health [1,2,3]. A few of these studies have investigated resistance of enterococcal species and their dissemination into surface water [20,21], to our knowledge environmental studies on occurrence of MAR bacteria in surface and ground water near poultry farms or farms using poultry litter as fertilizer have not been conducted. We investigated enterococci from different environments (poultry litter, surface and ground water) in areas of intensive poultry production to evaluate trends and correlations in specificity and levels of antibiotic resistance. MAR indices, the incidence of multiple-antibiotic resistant isolates among isolates from a sample, were calculated and applied to enterococci isolates to differentiate between low and high risk resistance bacterial contaminated sites
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