Abstract
The prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli) is increasing rapidly in both hospital environments and animal farms. A lot of animal manure has been directly applied into arable fields in developing countries. But the impact of ESBL-positive bacteria from animal manure on the agricultural fields is sparse, especially in the rural regions of Tai'an, China. Here, we collected 29, 3, and 10 ESBL-producing E. coli from pig manure, compost, and soil samples, respectively. To track ESBL-harboring E. coli from agricultural soil, these isolates of different sources were analyzed with regard to antibiotic resistance profiles, ESBL genes, plasmid replicons, and enterobacterial repetitive intergenic consensus (ERIC)-polymerase chain reaction (PCR) typing. The results showed that all the isolates exhibited multi-drug resistant (MDR). CTX-M gene was the predominant ESBL gene in the isolates from pig farm samples (30/32, 93.8%) and soil samples (7/10, 70.0%), but no SHV gene was detected. Twenty-five isolates contained the IncF-type replicon of plasmid, including 18 strains (18/32, 56.3%) from the pig farm and 7 (7/10, 70.0%) from the soil samples. ERIC-PCR demonstrated that 3 isolates from soil had above 90% genetic similarity with strains from pig farm samples. In conclusion, application of animal manure carrying drug-resistant bacteria on agricultural fields is a likely contributor to antibiotic resistance gene spread.
Highlights
The rapid increase of extended-spectrum beta-lactamases (ESBLs)-producing Enterobacteriaceae has attracted worldwide concern
From the soil samples treated with compost or manure, 10 ESBL-producing E. coli were isolated
Antimicrobial Susceptibility All the 42 ESBL-producing E. coli from manure, compost, and treated soil showed multiple drug resistance to antibiotics tested and the isolates from different origins had similar drug-resistant spectrum against the 14 antibiotics
Summary
The rapid increase of extended-spectrum beta-lactamases (ESBLs)-producing Enterobacteriaceae has attracted worldwide concern. ESBL-producing E. coli were widely found in hospital environments and farms (Edelstein et al, 2003; Smet et al, 2008) and they are able to survive in various natural environments such as feces, soils, and water bodies (Koczura et al, 2012; Blaak et al, 2014; Haque et al, 2014), so ESBL-producing E. coli is usually regarded as an indicator bacterium to trace the spread of antibiotic resistance gene (Gao et al, 2014). Animal manure fertilization has been found to increase the abundance of drug-resistant bacteria and the frequency of antibiotic resistance genes in soils (Venglovsky et al, 2009; Marti et al, 2013). Investigations on the influence of animal manure application on agriculture are of great significance
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