Detection of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli on flies at poultry farms

Abstract

In the Netherlands, extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli bacteria are highly prevalent in poultry, and chicken meat has been implicated as a source of ESBL-producing E. coli present in the human population. The current study describes the isolation of ESBL-producing E. coli from house flies and blow flies caught at two poultry farms, offering a potential alternative route of transmission of ESBL-producing E. coli from poultry to humans. Overall, 87 flies were analyzed in 19 pools. ESBL-producing E. coli bacteria were detected in two fly pools (10.5%): a pool of three blow flies from a broiler farm and a pool of eight house flies from a laying-hen farm. From each positive fly pool, six isolates were characterized and compared with isolates obtained from manure (n = 53) sampled at both farms and rinse water (n = 10) from the broiler farm. Among six fly isolates from the broiler farm, four different types were detected with respect to phylogenetic group, sequence type (ST), and ESBL genotype: A0/ST3519/SHV-12, A1/ST10/SHV-12, A1/ST58/SHV-12, and B1/ST448/CTX-M-1. These types, as well as six additional types, were also present in manure and/or rinse water at the same farm. At the laying-hen farm, all fly and manure isolates were identical, carrying blaTEM-52 in an A1/ST48 genetic background. The data imply that flies acquire ESBL-producing E. coli at poultry farms, warranting further evaluation of the contribution of flies to dissemination of ESBL-producing E. coli in the community.

FIG 1

ESBL type distribution in ESBL-producing E. coli isolates from a broiler farm and a laying-hen farm. The bars represent the numbers of isolates with genes encoding CTX-M-1, SHV-12, and TEM-52 in flies, manure, and rinse water. The manure isolates are grouped according to sampling location within the respective farms.

FIG 2

Phylogenetic group/ESBL type variants among ESBL-producing E. coli isolates from a broiler farm and a laying-hen farm. The bars represent the numbers of isolates with the indicated combinations of phylogenetic groups and ESBL types in flies, manure, and rinse water. The manure isolates are grouped according to sampling location within the respective farms.