Antimicrobial Resistance and Pathotypes of Escherichia coli Isolates from Yellow-Legged Seagulls (Larus michahellis) in Central Italy

Seagulls are synanthropic wild birds that can contaminate, through their droppings, beaches, urban and peri-urban environments. This concern is more serious when seagulls eliminate antimicrobial-resistant pathogenic bacteria. This study analyzed the fecal samples from 137 yellow-legged seagulls (<i>Larus michahellis</i>) from Central Italy. A total of 218 <i>Escherichia coli</i> strains were isolated and analyzed for phenotypic and genotypic antimicrobial resistance and to identify the virulence genes characterizing different pathotypes. The disk diffusion method on all isolates found relevant resistance rates to ampicillin (38.99%), tetracycline (23.85%), and enrofloxacin (21.10%). On the basis of all results obtained with this test, 62 (28.44%) isolates were classified as multidrug-resistant (MDR) and 6 (2.75%) as extensive drug-resistant (XDR). Molecular analyses conducted on the strains phenotypically resistant to carbapenems, cephalosporins, and penicillins found 9/37 (24.32%) strains positive for <i>bla</i>_OXA-48, 52/103 (50.49%) for <i>bla</i>_TEM, 12/103 (11.65%) for <i>bla</i>_CMY2, 3/103 (2.91%) for <i>bla</i>_CTX, and 1/103 (0.97%,) for <i>bla</i>_SHV. PCR to detect virulence genes characterizing different pathotypes found that 40 (18.35%) isolates had the <i>ast</i>A gene, indicative of the enteroaggregative (EAEC) pathotype, 2 (0.92%) had <i>cnf</i>1, 2 (0.92%) had <i>cnf</i>2, and 1 (0.46%) had <i>cdt</i>-IV. All five (2.29%) strains were reportable as necrotoxigenic (NTEC), while 4 (1.83%) had both <i>eae</i>A and <i>esc</i>V, reportable as enteropathogenic (EPEC). Measures to limit seagulls' access where humans and other animals reside are pivotal to reduce the risk of infection with antimicrobial-resistant and pathogenetic <i>E. coli</i> strains.