Prevalence of extended-spectrum beta-lactamase-producing bacteria in food

Johan Tham,¹ Mats Walder,² Eva Melander,^2,3 Inga Odenholt<sup>1

1</sup>Infectious Diseases Unit, Department of Clinical Sciences, ²Medical Microbiology, Department of Laboratory Medicine, Lund University, Malmö, Sweden; ³Department of Infection Control, Laboratory Medicine, Skåne County, Sweden

Abstract: Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae with Cefotaximase–München (CTX-M) enzymes are rapidly increasing worldwide and pose a threat to health care. ESBLs with CTX-M enzymes have been isolated from animals and different food products, but it is unknown if food imported from the Mediterranean area may be a possible reservoir of these bacteria. During 2007–2008, swab samples from food across different retail outlets (mostly food from the Mediterranean countries and Swedish chicken) were collected. Escherichia coli strains from Swedish meat and E. coli isolates from unspecified food from a Swedish food testing laboratory were also examined. In 349 of the 419 swab samples, growth of Enterobacteriaceae was found. In most of the samples, there was also growth of Gram-negative environmental bacteria. Air dry-cured products contained significantly less Enterobacteriaceae isolates compared to lettuces; however, none of the examined Enterobacteriaceae harbored ESBLs. This study did not support the theory that imported food from the Mediterranean area or Swedish domestic food might constitute an important vehicle for the dissemination of ESBL-producing Enterobacteriaceae; however, a spread from food to humans may have occurred after 2008.

Keywords: ESBL, antibiotic resistance, zoonosis, food, Enterobacteriaceae