Quinolone-resistant Salmonella Infantis (n = 64) isolated from human stool samples, food and poultry during the years 2006-2011 were analysed for their resistance phenotypes, macrorestriction patterns and molecular mechanisms of decreased susceptibility to fluoroquinolones. Minimum inhibitory concentrations (MICs) of nalidixic acid (NAL) and ciprofloxacin (CIP) were determined by the agar dilution procedure, and the susceptibility to additional antimicrobial agents was determined by the disc diffusion method. To assess the influence of enhanced efflux activity, MICs were determined in the presence and absence of the inhibitor PAβN. The results of pulsed-field gel electrophoresis (PFGE) typing revealed that quinolone-resistant S. Infantis in Serbia had similar or indistinguishable PFGE profiles, suggesting a clonal spread. All S. Infantis showed combined resistance to NAL and tetracycline, whereas multiple drug resistance to three or more antibiotic classes was rare (2 isolates of human origin). The MICs ranged between 512 and 1024 μg/mL for NAL and 0.125-2 μg/mL for CIP. A single-point mutation in the gene gyrA leading to a Ser83→Tyr exchange was detected in all isolates, and a second exchange (Ser80→Arg) in the gene parC was only present in eight S. Infantis isolates exhibiting slightly higher MICs of CIP (2 μg/mL). The inhibitor PAβN decreased the MIC values of CIP by two dilution steps and of NAL by at minimum 3-6 dilution steps, indicating that enhanced efflux plays an important role in quinolone resistance in these isolates. The plasmid-mediated genes qnr, aac(6')-lb-cr and qepA were not detected by PCR assays.

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[Projekat Ministarstva nauke Republike Srbije, br. 31087]

Salmonella is one of the most important zoonotic pathogens and the consumption of pork meat is one of the major sources of human infection. The aim of this study was to investigate the presence of salmonella on pig carcasses. Samples were taken from slaughterhouse A in two instances (sampling I and II, a total of 300 samples) and in slaughterhouse B once (sampling III, a total of 120 samples), from pork carcasses after the stunning and after the processing. Of the total number of examined samples, the percentage of positive samples for salmonella from pork carcasses after stunning was 46.7% (90/42), and samples from the carcasses after processing 3.3% (90/3). Operations taking place on the slaughter line could have an effect on the salmonella contamination of carcasses

No abstract