Hierarchal clustering yields insight into multidrug-resistant bacteria isolated from a cattle feedlot wastewater treatment system

• Published in: Environmental monitoring and assessment 2015-01, Vol.187 (1), p.4168-15, Article 4168
• Main Authors: Jahne, Michael A., Rogers, Shane W., Ramler, Ivan P., Holder, Edith, Hayes, Gina
• Format: Article
• Language: English
• Subjects: Agricultural runoff; Amikacin; Animal Husbandry; Animal wastes; Animals; Antibiotic resistance; Antibiotics; Artificial wetlands; Assessments; Atmospheric Protection/Air Quality Control/Air Pollution; Bacteria; Bacteria - drug effects; Cattle; Cefoxitin; Ceftriaxone; Cephalosporins; Cross-resistance; Dalfopristin; Daptomycin; Disease prevention; Drug dosages; Drug resistance; Drug Resistance, Bacterial - physiology; E coli; Earth and Environmental Science; Ecology; Ecotoxicology; Enterococcus; Enterococcus - classification; Enterococcus - growth & development; Enterococcus - isolation & purification; Environment; Environmental Management; Environmental Monitoring; Environmental protection; Erythromycin; Escherichia coli - classification; Escherichia coli - growth & development; Escherichia coli - isolation & purification; Feces; Feedlots; Flushing; Gentamicin; Hydraulic loading; Hydraulics; Infiltration; Intensive farming; Kanamycin; Lincomycin; Linezolid; Lipopeptides; Livestock; Low flow; Manures; Microbial Sensitivity Tests; Monitoring/Environmental Analysis; Multidrug resistance; Multidrug resistant organisms; Nalidixic acid; Oxazolidinones; Pathogens; Public health; Quinolones; Runoff; Staphylococcus infections; Vancomycin; Waste Disposal, Fluid; Waste Water - microbiology; Wastewater treatment; Water treatment; Wetlands
• ISSN: 0167-6369; 1573-2959
• DOI: 10.1007/s10661-014-4168-9

Forty-two percent of Escherichia coli and 58 % of Enterococcus spp. isolated from cattle feedlot runoff and associated infiltration basin and constructed wetland treatment system were resistant to at least one antibiotic of clinical importance; a high level of multidrug resistance (22 % of E. coli and 37 % of Enterococcus spp.) was observed. Hierarchical clustering revealed a closely associated resistance cluster among drug-resistant E. coli isolates that included cephalosporins (ceftiofur, cefoxitin, and ceftriaxone), aminoglycosides (gentamycin, kanamycin, and amikacin), and quinolone nalidixic acid; antibiotics from these classes were used at the study site, and cross-resistance may be associated with transferrable multiple-resistance elements. For Enterococcus spp., co-resistance among vancomycin, linezolid, and daptomycin was common; these antibiotics are reserved for complicated clinical infections and have not been approved for animal use. Vancomycin resistance ( n  = 49) only occurred when isolates were resistant to linezolid, daptomycin, and all four of the MLS B (macrolide-lincosamide-streptogramin B) antibiotics tested (tylosin, erythromycin, lincomycin, and quinipristin/dalfopristin). This suggests that developing co-resistance to MLS B antibiotics along with cyclic lipopeptides and oxazolidinones may result in resistance to vancomycin as well. Effects of the treatment system on antibiotic resistance were pronounced during periods of no rainfall and low flow (long residence time). Increased hydraulic loading (short residence time) under the influence of rain caused antibiotic-resistant bacteria to be flushed through the treatment system. This presents concern for environmental discharge of multidrug-resistant organisms relevant to public health.