Detection of Extended-Spectrum Beta-Lactamase (ESBL)-Producing Escherichia coli on Flies at Poultry Farms

<jats:title>ABSTRACT</jats:title> <jats:p> In the Netherlands, extended-spectrum beta-lactamase (ESBL)-producing <jats:named-content content-type="genus-species">Escherichia coli</jats:named-content> bacteria are highly prevalent in poultry, and chicken meat has been implicated as a source of ESBL-producing <jats:named-content content-type="genus-species">E. coli</jats:named-content> present in the human population. The current study describes the isolation of ESBL-producing <jats:named-content content-type="genus-species">E. coli</jats:named-content> from house flies and blow flies caught at two poultry farms, offering a potential alternative route of transmission of ESBL-producing <jats:named-content content-type="genus-species">E. coli</jats:named-content> from poultry to humans. Overall, 87 flies were analyzed in 19 pools. ESBL-producing <jats:named-content content-type="genus-species">E. coli</jats:named-content> 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 ( <jats:italic>n</jats:italic> = 53) sampled at both farms and rinse water ( <jats:italic>n</jats:italic> = 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: A <jats:sub>0</jats:sub> /ST3519/SHV-12, A <jats:sub>1</jats:sub> /ST10/SHV-12, A <jats:sub>1</jats:sub> /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 <jats:italic>bla</jats:italic> <jats:sub>TEM-52</jats:sub> in an A <jats:sub>1</jats:sub> /ST48 genetic background. The data imply that flies acquire ESBL-producing <jats:named-content content-type="genus-species">E. coli</jats:named-content> at poultry farms, warranting further evaluation of the contribution of flies to dissemination of ESBL-producing <jats:named-content content-type="genus-species">E. coli</jats:named-content> in the community. </jats:p>