Safety evaluation of Sjenica cheese with regard to coagulase-positive staphylococci and antibiotic resistance of lactic acid bacteria and staphylococci

Abstract

Sjenica cheese is an artisanal cheese stored in brine, traditionally produced from raw sheeps milk in the southern part of Serbia - Sjenica Pester plateau. The aim of this study was to perform the safety evaluation of Sjenica cheese. As one of the safety criteria we considered the number of coagulase positive staphylococci and their enterotoxigenic potential. Antibiotic susceptibility/resistance patterns of autochthonous lactic acid bacteria and coagulase-positive staphylococci isolated from Sjenica cheese was also investigated. During the monitoring period of the cheese-making process, coagulase positive staphylococci did not reach the value of 10(5) cfu/g. Among coagulase positive staphylococci, 12 (46,15%) isolates showed enterotoxigenic potential and were identified as Staphylococcus intermedius (11 isolates) and Staphylococcus aureus (1 isolate). Vancomycin resistance was the most prevalent phenotypic resistance profile in coagulase positive staphylococci. Lactococci present the most dominant population among lactic acid bacteria. The most prevalent resistance phenotype in lactococci was resistance to streptomycin (83.33%), ampicillin and penicillin (70.83%); lactobacilli were characterized by resistance to vancomycin (62.5%) and tetracycline (54.17%), while resistance to streptomycin (82.46%) was the most prevalent phenotypic profile in enterococci. All coagulase positive staphylococci and lactic acid bacteria isolates that showed resistance to tetracycline on disc diffusion and E-test, were tested for the presence of ribosomal protection proteins, tet(M) and tet(K) genes. All isolates were positive for ribosomal protection proteins genes; 14 (60.87%) isolates showed tet(M) gene presence, while 2 lactobacilli isolates revealed the presence of tet(K) gene.