Plasmid profile analysis and evaluation of antibiotic susceptibility of Staphylococcus aureus strains isolated from table chicken eggs.

The aim of this study was to isolate and characterize Staphylococcus aureus bacteria present on the shell surfaces and in the contents of chicken eggs, taking into account their phenotypic properties, antibiotic susceptibility patterns, and the presence of plasmid DNA. The study included 90 table chicken eggs from laying farms situated in the vicinity of Lublin. A total of 105 bacterial strains identified as Staphylococcus were isolated from the material, of which 18 (17.14%) were of the species Staphylococcus aureus. All 18 S. aureus strains were found to be resistant to at least one of the antibiotics tested, while some (55.55%) showed resistance to five or more of the 17 therapeutic agents. The greatest number of strains showed resistance to erythromycin (66.66%), tetracycline (66.66%), oxytetracycline (61.11%), penicillin G (50%), and amoxicillin (44.44%). The plasmid profile analysis of the S. aureus strains made it possible to evaluate the dependence between antibiotic susceptibility and the presence of plasmids in particular isolates. The results showed that plasmids in various quantities and of varying molecular weights were isolated from 17 of the strains. Most often isolated were small plasmids, of 5.6 kb--from 11 of the S. aureus strains (61.11%), 2.5 kb--from 9 strains (50%), 4.1 kb--from 8 (44.44%), and 4.6 kb--from 7 (38.88%) of the strains.