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ANTIMICROBIAL RESISTANCE AMONG ENTERIC BACTERIA ISOLATED FROM HUMAN AND ANIMAL WASTES AND IMPACTED SURFACE WATERS: COMPARISON WITH NARMS FINDINGS
Citation:
Cole, D., M. D. Sobsey, J E. Bumgarner, AND D. Robinette. ANTIMICROBIAL RESISTANCE AMONG ENTERIC BACTERIA ISOLATED FROM HUMAN AND ANIMAL WASTES AND IMPACTED SURFACE WATERS: COMPARISON WITH NARMS FINDINGS. Presented at National Antimicrobial Resistance Monitoring System Meeting, Rockville, MD, March 15-16, 2001.
Impact/Purpose:
1) Develop methods of ecological exposure (e.g. rapid , sensitive analytical screening methods for a select list of antibiotics widely used in agriculture primarily in CAFOs (confined animal feeding operations).
2) Do Measurements & Provide data for multicompartment models of fate and transport.
3) Study biomagnification of specific chemicals and toxic metals.
4) Study specific pharmaceuticals:
*Determine the routes of entry and the impact of environmental factors such as rainfall on the movement and survivorability of selected antimicrobials in the environment.
*Determine if the entry of agriculture based antibiotics into the environment contributes to resistance in bacterial populations.
*Determine the contribution from municipal waste water treatment plants to antibiotic loading in the environment.
5) Develop methods for the analysis of alkylphenol ethoxylates and derivatives.
Description:
Human infection with bacteria exhibiting mono or multiple antimicrobial resistance (MAR) has been a growing problem in the US, and studies have implicated livestock as a source of MAR bacteria primarily through foodborne transmission routes. However, waterborne transmission of resistant microbes and transferable genetic elements via fecal contaminated waters is another postulated route of MAR transmission from livestock to humans. Human acquisition of MAR pathogens or transferable genetic elements from animal feeding operation (AFO)-contaminated water can occur either through direct intake of resistant microbes in drinking or recreational waters, or by ingestion of resistant microbes on produce irrigated with AFO-contaminated waters. An ongoing study of 2 cattle farms, 2 swine farms, and 2 human waste water treatment facilities in North Carolina is collecting isolates of E. coli, enterococci, and Salmonella from cattle, geese, and swine wastes; cattle and swine waste lagoons; partially treated human waste; and surface waters adjacent to study farms and in rural/background surface waters. The MIC of each isolate to a variety of human and animal antimicrobials is determined using a customized Sensititre (SensititreTM, TREKTM Diagnostics, Inc.) plate and compared to the breakpoints used in the National Antimicrobial Resistance Monitoring System (NARMS) surveillance study. The most common resistance patterns found among both human and animal waste-derived E. coli isolates include streptomycin, sulfamethoxazole, and ampicillin. Tetracycline resistance was found among >90% of swine E. coli isolates and 50% of bovine isolates but has not been observed among the human E. coli isolates so far. Conversely, 29% of human E. coli isolates exhibited resistance to trimethoprim compared to none of the swine or cattle isolates. Similar resistance patterns are found among the Salmonella isolates. Three human Salmonella isolates (21%) were susceptible to all tested antimicrobials; whereas only 1 swine Salmonella isolate (4%) was susceptible to all tested antimicrobials. MAR patterns were prevalent among both human (42% MAR) and swine (75% MAR) Salmonella isolates. Resistance to erythromycin and tetracycline was more commonly observed among the swine enterococcal isolates (100% for both) compared to human isolates (40% and 20%, respectively). The prevalence of resistance is slightly higher among isolates obtained from animal waste lagoons than from barn flush, and the patterns observed among resident geese reflect those observed in the swine wastes. In addition, bacterial isolates from surface water sites located downstream from swine farms have higher prevalences of resistance than those obtained from upstream sites and the observed resistance patterns are similar to those observed among farm isolates. Furthermore, the most prevalent resistance patterns observed among downstream E. coli isolates are those reported by NARMS as being most prevalent among clinical E. coli O157 isolates. Although the results are preliminary, these data suggest that waterborne transmission may be another route of human exposure to resistant microbes of livestock origin.
This work has been funded wholly or in part by the United States Environmental Protection Agency under OD-5555-NTEX to the University of North Carolina (UNC). It has been subjected to Agency review and approved for publication.