Abstract
Dissemination of enterobacteria that produce extended spectrum β-lactamases (ESBL) throughout the food chain has become an important health concern. This work aimed to evaluate the occurrence of ESBL-producing bacteria in foods of animal origin and to investigate the similarities between food and human isolates. The presence of beta-lactam-resistant Enterobacteriaceae was analyzed in 108 food samples, isolating 10 strains of Escherichia coli, one strain of Citrobacter freundi, and one of Hafnia alvei. E. coli isolates were compared to a group of 15 strains isolated from human patients by antibiotic susceptibility testing, characterization of ESBL genes (blaTEM, blaCTX,), multilocus sequence typing (MLST) and pulse-field gel electrophoresis (PFGE). Nineteen (14 clinical and five food) isolates carried blaCTX, 14 (six clinical and eight food) carried blaTEM, and three (one clinical and two food) carried blaSHV gen. MLST analysis revealed the prevalence of ST131 among the clinical strains, which grouped together in a PFGE cluster. Food isolates showed higher diversity and two of them (ST57) grouped with clinical strains, whereas another two belonged to clonal groups with virulence potential (ST59). In conclusion, the results showed that foods of animal origin must be regarded as a reservoir of ESBL-producing bacteria of clinical relevance, which might spread through the food chain.
Highlights
The production of extended spectrum β-lactamases (ESBL) by members of the familyEnterobacteriaceae has become an important public health concern
MALDI-TOF analysis identified 10 isolates (76.9%) as E. coli, obtained from ewe and goat’s milk and chicken meat; and identified two (15.4%) as Citrobacter freundi and one (7.7%) as Hafnia alvei, which were obtained from fresh cheese
All the E. coli colonies were resistant to cefotaxime or ceftazidime and showed larger inhibition zones if clavulanic acid was present; three food isolates obtained from ewe’s milk turned out to not be ESBL-producers, as the inhibition zones in the presence of clavulanic acid showed less than five mm increase
Summary
The production of extended spectrum β-lactamases (ESBL) by members of the familyEnterobacteriaceae has become an important public health concern. Person-to-person transmission of ESBL-producing Enterobacteriaceae has been demonstrated in hospital and community settings, indicating that human colonization is a reservoir for spreading [3]. There are numerous reports on the isolation of ESBL-producing bacteria from foods and food animals, suggesting the possible role of the food production chain as a reservoir for this group of bacteria [1,3,4,5,6,7,8]. The occurrence of ESBL producers is generally high in livestock (up to 60 % of positive chicken fecal samples), whereas low prevalence is found among food samples [9]. Some studies found high rates of colonization by ESBL-producers in chicken meat [10,11] and contamination of raw cow’s milk has been reported [6,12]. There are reports of a strong correlation between the presence of ESBL-producing bacteria in foods and the incidence of infections in humans, and it may be
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