Manure as a Source of Antibiotic-Resistant Escherichia coli and Enterococci: a Case Study of a Wisconsin, USA Family Dairy Farm

Abstract

The spread of antibiotic-resistant bacteria in the environment is raising serious public health concerns, and manure is being increasingly recognized as a major source of antibiotic-resistant bacteria. In this research, we isolated Escherichia coli and enterococci from manure produced in a Wisconsin, USA family dairy farm to determine their resistance to six representative antibiotics. The average densities for E. coli and enterococci were 6.37(±4.38)×10 7 colony formation units (CFU)g −1 and 1.60(±1.57)× 10 4 CFU g −1 , respectively. The E. coli isolates were found to be resistant to cephalothin, ampicillin, tetracycline, and erythromycin. In addition to these four antibiotics, the Enterococcus isolates were also resistant to gentamicin and ciprofloxacin. Additionally, we examined the survival and growth of E. coli and enterococci in dairy manure over a period of 3 days. While the densities of enterococci remained stable over the study period, the concentrations of E. coli on average increased by 1.5 log10 units. Further tests of the bacterial antibiotic resistance over time showed no significant changes in the prevalence of antibiotic resistance. This result indicated that slightly aged manure could represent a larger source of antibiotic-resistant E. coli than fresh manure and the accumulation of antibiotic-resistant E. coli and enterococci in the agricultural fields must be accounted for in the modeling of the spread of antibioticresistant bacteria in the environment.

Influence of tetracycline resistance on the transport of manure-derived Escherichia coli in saturated porous media

“…As a result of the widespread use of antibiotics in the animal farm environment, high frequencies of antibiotic resistant bacteria have been detected in animal waste (Halbert et al, 2006; Parveen et al, 2006; Ray et al, 2006; Sapkota et al, 2007; Sato et al, 2004; Varga et al, 2008a; Walczak and Xu, 2010). On the dairy farm from which the E. coli strains used in this research were isolated, 13.1%, 72.7%, 80.5% of the E. coli isolates were resistant to tetracycline, cephalothin and erythromycin, respectively (Walczak and Xu, 2010).…”

“…On the dairy farm from which the E. coli strains used in this research were isolated, 13.1%, 72.7%, 80.5% of the E. coli isolates were resistant to tetracycline, cephalothin and erythromycin, respectively (Walczak and Xu, 2010). Additionally, 100% of the tet R E. coli isolates were multi-drug resistant.…”

“…The isolated E. coli were tested for their susceptibility to 6 representative antibiotics using Mueller-Hinton agar plates amended with various antibiotics (Clinical and Laboratory Stardards Institute, 2006; Walczak and Xu, 2010). For each antibiotic reagent, two different concentrations were tested.…”

“…For each antibiotic reagent, two different concentrations were tested. No E. coli isolates were resistant to gentamicin and ciprofloxacin, while resistance to cephalothin, ampicillin, erythromycin and tetracycline was prevalent (Walczak and Xu, 2010). …”

Prevalence and persistence of potentially pathogenic and antibiotic resistant bacteria during anaerobic digestion treatment of cattle manure

“…To increase production related to prophylaxis, infectious diseases treatment and/or growth promoters, antimicrobial drugs are widely applied in animal husbandry (Heuer et al, 2011). As an ecological consequence, the presence of zoonotic pathogens in the environments and unintentional selection of bacteria that are resistant to antibiotics could have important human and animal health consequences, mainly when end up in agricultural lands (Walczak and Xu, 2011;Costa et al, 2013).…”