Antimicrobial resistance of coagulase-negative staphylococci and lactic acid bacteria from industrially produced dairy products

In this research, the susceptibility to clindamycin, tetracycline, amikacin, amoxicillin + clavulanic acid, enrofloxacine, vancomycin, trimethoprim + sulphametoxazol, tobramycin, chloramphenicol, ciprofloxacin, erythromycin, penicillin and trimethoprim was tested in coagulase-negative staphylococci (n=78) and lactic acid bacteria (n=30) by means of disk diffusion test and E-test. The isolates were collected from soft and hard cheeses, butter and brine. All isolates of coagulase-negative staphylococci were susceptible to clindamycin, amikacin, amoxicillin + clavulanic acid, enrofloxacine, vancomycin, chloramphenicol and ciprofloxacin according to CLSI breakpoints. A total of 30 staphylococci isolates (38.46 %) were resistant to erythromycin, 18 to penicillin (23.07 %), 4 to tetracycline (5.12 %), and one isolate to trimethoprim, tobramicin and trimethoprim + sulphametoxazol (1.28 %). Among 78 tested staphylococci, 35 of them were resistant to at least one antimicrobial substance (44.87 %). The rate of resistant isolates of different soft cheese types ranged from 22 to 70 %, while resistant staphylococci were absent in hard cheese and brine. The growth of lactic acid bacteria was not influenced by trimethoprim + sulphametoxazol (n=29), vancomycin (n=29), trimethoprim (n=28), amikacin (n=10) and tobramycin (n=10). The results show that significant part of apathogenic microbiota in different dairy products is phenotypically resistant to antimicrobial agents.