ESBL-producing Enterobacteriaceae: occurrence, risk factors for fecal carriage and strain traits in the Swiss slaughter cattle population younger than 2 years sampled at abattoir level

Abstract

During the past decade extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae have become a matter of great concern in human and veterinary medicine. In this cross-sectional study fecal swabs of a geographically representative number of Swiss cattle at slaughterhouse level were sampled i) to determine the occurrence of ESBL producing Enterobacteriaceae in the Swiss slaughter cattle population younger than 2 years, and ii) to assess risk factors for shedding ESBL producing Enterobacteriaceae. In total, 48 (8.4%; 95% C.I. 6.3-11.1%) independent ESBL producing Enterobacteriaceae were detected among the 571 tested animals. Species identification revealed 46 E. coli strains, one Enterobacter cloacae and one Citrobacter youngae. In view of beta-lactam antibiotics, all 48 isolates were resistant to ampicillin, cephalothin and cefpodoxime. Forty-five (93.8%) isolates were resistant cefuroxime; one (2.1%) isolate to cefoxitin, 28 (58.3%) isolates to cefotaxime, 2 (4.2%) isolates to ceftazidime, and 2 (4.2%) isolates to cefepime. Risk factors for shedding ESBL producing Enterobacteriaceae were (i) age (OR 0.19 and 0.12 in age category 181 d to 1 y and 1 y to 2 y compared to ≤180 d), (ii) primary production type, meaning dairy compared to beef on farm of origin (OR 5.95), and (iii) more than 1 compared to less than 1 animal movement per d per 100 animals on farm of origin (OR 2.37).

Figure 1. Characteristics and antimicrobial susceptibility profiles of ESBL-producing Enterobacteriaceae isolated from cattle younger than 2

years. Symbols: black square, positive result or resistant to a specific antimicrobial agent; white square, negative result or susceptible to a specific antimicrobial. Abbreviations: AM, ampicillin (resistant ≤13 mm); AMC, amoxicillin-clavulanic acid (resistant ≤13 mm); CF, cephalothin (resistant ≤14 mm); CXM, cefuroxime (resistant ≤14 mm); FOX, cefoxitin (resistant ≤14 mm); CPD, cefpodoxime (resistant ≤17 mm); CTX, cefotaxime (resistant ≤14 mm); CAZ, ceftazidime (resistant ≤14 mm); FEP, cefepime (resistant ≤14 mm); GM, gentamicin (resistant ≤10 mm); S, streptomycin (resistant ≤11 mm); SXT, trimethoprim-sulfamethoxazole (resistant ≤10 mm); TE, tetracycline (resistant ≤11 mm); NA, nalidixic acid (resistant ≤13 mm); CIP, ciprofloxacin (resistant ≤15 mm); C, chloramphenicol (resistant ≤12 mm). Discrimination between “susceptible” and “resistant” was strictly according to CLSI interpretive criteria. It should be noted, however, that for clinical and therapeutic purposes, ESBL producers should generally be reported resistant to cephalosporins of all 4 generations and monobactams.