Differences in the antibiotic susceptibility of human Escherichia coli with poultry-associated and non-poultry-associated extended-spectrum beta-lactamases

Abstract

The concurrent presence of bla CTX-M-1 and bla TEM-52 genes on similar plasmids of Escherichia coli isolated from poultry, chicken meat and humans supports the occurrence of food-borne transmission of extended-spectrum beta-lactamase (ESBL) genes. ESBL-producing E. coli (ESBL-E. coli) are most frequently detected in hospitalised patients and are known to spread in healthcare settings. We hypothesised that poultry-associated (PA) ESBL genes are predominant in the community, where acquisition is fuelled by food contamination, whereas non-PA ESBL genes are predominant in hospitals, with acquisition fuelled by cross-transmission. Then, differences in antimicrobial selective pressure in hospitals and poultry would create differences in co-resistance between PA and non-PA ESBL-E. coli. We, therefore, determined the prevalence and co-resistance of PA and non-PA ESBL-E. coli in community-acquired and nosocomial urinary tract infections in humans and bla CTX-M-1 and bla TEM-52 isolates from poultry. A total of 134 human ESBL-E. coli urine isolates were included in this study. Isolates containing bla CTX-M-1 or bla TEM-52 were considered to be PA, with the remainder being non-PA. Also, 72 poultry ESBL-E. coli were included. Minimum inhibitory concentration (MIC) values were determined by broth microdilution. The prevalence of PA ESBL genes in isolates obtained in general practice and hospitals was 28% versus 30% (n.s.). Human PA ESBL-E. coli were more frequently susceptible to ciprofloxacin (51% vs. 25%; p = 0.0056), gentamicin (86% vs. 63%; p = .0.0082), tobramycin (91% vs. 34%; p = 0.0001) and amikacin (98% vs. 67%; p = 0.0001) compared to human non-PA ESBL-E. coli. PA ESBL-E. coli are not more prevalent in community acquired than nosocomial urine samples, but are more often susceptible to ciprofloxacin and aminoglycosides than non-PA ESBL-E. coli. This does not support the existence of different reservoirs of ESBL genes.