Identification and Characterization of Cefotaxime Resistant Bacteria in Beef Cattle.

Raies A Mir,Judith A Johnson,Thomas A Weppelmann,Douglas Archer,Kwangcheol Casey Jeong,J Glenn Morris,Yung-Fu Chang

doi:10.1371/journal.pone.0163279

Abstract

Third-generation cephalosporins are an important class of antibiotics that are widely used in treatment of serious Gram-negative bacterial infections. In this study, we report the isolation of bacteria resistant to the third-generation cephalosporin cefotaxime from cattle with no previous cefotaxime antibiotic exposure. The prevalence of cefotaxime-resistant bacteria was examined by a combination of culture based and molecular typing methods in beef cattle (n = 1341) from 8 herds located in North Central Florida. The overall prevalence of cefotaxime-resistant bacteria was 15.8% (95% CI: 13.9, 17.8), varied between farms, and ranged from 5.2% to 100%. A subset of isolates (n = 23) was further characterized for the cefotaxime minimum inhibitory concentration (MIC) and antibiotic susceptibility against 10 different antibiotics, sequencing of nine β- lactamase genes, and species identification by 16S rRNA sequencing. Most of the bacterial isolates were resistant to cefotaxime (concentrations, > 64 μg/mL) and showed high levels of multi-drug resistance. Full length 16S rRNA sequences (~1300 bp) revealed that most of the isolates were not primary human or animal pathogens; rather were more typical of commensal, soil, or other environmental origin. Six extended spectrum β-lactamase (ESBL) genes identical to those in clinical human isolates were identified. Our study highlights the potential for carriage of cefotaxime resistance (including “human” ESBL genes) by the bacterial flora of food animals with no history of cefotaxime antibiotic exposure. A better understanding of the origin and transmission of resistance genes in these pre-harvest settings will be critical to development of strategies to prevent the spread of antimicrobial resistant microorganisms to hospitals and communities.

Highlights

The emergence of bacterial pathogens resistant to treatment with antibiotics is one of the most critical challenges to modern medicine and represents a major threat to public health
To investigate the phenomenon of antibiotic resistance occurrence, we examined the prevalence of bacteria resistant to cefotaxime from cattle with no previous cefotaxime exposure at three farms in North Central Florida
Beef cattle with no previous cefotaxime antibiotic exposure were colonized by bacteria resistant to the third generation cephalosporin cefotaxime

Summary

Introduction

The emergence of bacterial pathogens resistant to treatment with antibiotics is one of the most critical challenges to modern medicine and represents a major threat to public health. It is becoming more evident that the natural bacterial resistome plays an important role in the evolution and spread of resistance [1,2] with extensive use of antibiotics in food animal production likely accelerating the acquisition of antimicrobial resistance by human pathogens [3]. Third generation cephalosporins are widely used for the treatment and prevention of bacterial infections in hospitals, but not in food animal production for the prevention purpose since 2012 [4,5]. Bacterial resistance to third generation cephalosporins is often conferred by production of extended spectrum β-lactamase (ESBL) enzymes [6]. The majority of the isolates were commensal bacteria commonly found in nature; they were frequently multi-drug resistant and possessed ESBL genes identical to isolates from hospital and community acquired infections

Methods

Results

Conclusion