Analysis of phenotypic and genotypic antibiotic resistance of food isolates of Staphylococcus spp.

Abstract

Background. Staphylococcus bacteria are potentially pathogenic species that are more and more often isolated from the natural environment. They are often responsible for the spoilage of food products and for food poisoning in consumers. The aim of this study was to analyse the phenotypic and genotypic antibiotic resistance of food isolates of the genus Staphylococcus. Materials and methods. The biological material consisted of 5 coagulase-negative strains of the genus Staphylococcus isolated from food (radish sprouts, fresh milk and a dietary supplement) and a reference strain, Staphylococcus epidermidis DSMZ 3270. Phenotypic antibiotic resistance was examined using the disc method, while genotypic antibiotic resistance assessment was examined using Real-Time PCR. Results. All of the tested isolates turned out to be resistant to 6 antibiotics: erythromycin, gentamycin, rifampicin, linezolid, tigecycline and methicillin. On this basis, the isolates were classified as multi-drug-resistant strains. For all 5 isolates and Staphylococcus epidermidis DSMZ 3270, only 2 common genes present in the DNA (plasmid and/or genomic) were identified: tet(L) and int(Tn916/Tn1545). However, none of them had the mec(A) gene. Conclusion. On this basis, the isolates were classified as multi-drug-resistant strains. The study confirms the increasing prevalence of multi-drug-resistant bacteria of the genus Staphylococcus in the environment.