Occurrence of extended-spectrum β-lactamases among isolates of Salmonella enterica subsp enterica from food-producing animals and food products, in Portugal

A total of 1120 Salmonella spp. isolates, recovered from poultry, swine and food products of animal origin (bovine, swine and poultry) over the period of 2009-2011, were investigated in order to determine their serotype, susceptibility to a panel of eleven antimicrobials (A, ampicillin; Ct, cefotaxime; Cp, ciprofloxacin; Tm, trimethoprim; Su, sulfamethoxazole; C, chloramphenicol; S, streptomycin; G, gentamicin; T, tetracycline; NA, nalidixic acid; FI, florfenicol), and the presence of resistance determinants of extended-spectrum cephalosporins. Overall, Salmonella Enteritidis was the most common serotype in all three animal species. In 618 isolates of poultry, 32.8% comprised S. Enteritidis, 183% Salmonella Havana and 16.5% Salmonella Mbandaka; in 101 isolates of pigs, 21.8% comprised Salmonella Rissen and Salmonella Typhimurium, 10.9% Salmonella Derby and Salmonella London. Salmonella I 4,15],12:i:- was the most common serotype recovered from pork and beef food products comprising 32.6% and 30% of isolates respectively, followed by S. Rissen (26% and 24%) and S. Typhimurium (18.2% and 19%), respectively. In poultry products, S. Enteritidis was the most frequent serotype (62.7%), followed by S. Mbandaka (10.2%) and S. Derby (8.5%). Susceptibility profiles differed according to the origin of the isolates. Five multidrug resistant isolates (0.45%) were further characterized as extended-spectrum p-lactamase (ESBL) producers. Polymerase chain reaction and sequencing of the amplicons confirmed the presence of bla(CTX-M-1) (n = 2), (CTX-M-14) (n = 1), bla(CTX-M-15) (n = 1) and bla(CTX-M-32) (n = 1); bla(SHV-12) and bla(TEM-1) genes were also detected in two isolates of S. I 4,[5],12:i:-. Four isolates, two S. Havana and two 5.14,[5],12 -, carried class 1 integrons and in three, two S. I 4,[51,12:i:- and one S. Havana, ISEcp1 was identified associated to bla(CTX-M-1), bla(CTX-M-32) and bla(CTX-M-14) genes. Additionally, in one S. I 4,[5],12:i:- isolate, oif477 was identified linked to bla(CTX-M-32). No plasmid mediated quinolone resistance-encoding genes were detected. Here, we report for the first time the presence of bla(CTX-M) genes in Salmonella enterica subsp enterica isolates recovered from poultry and food products of swine origin, in Portugal. (C) 2013 Elsevier B.V. All rights reserved.