Relationship between methicillin resistance and the presence of femA and mecA genes in coagulase positive and negative staphylococci isolated from milk and cheese

Abstract

Three hundred milk and cheese samples were collected from Baghdad markets. Two hundred staphylococcal isolates were isolated from milk and cheese samples. Staphylococcus aureus was predominant species (97 isolates (48%)) followed by S. chromogenes (82 isolates (41%)) and S. epidermidis (21 isolates (11%)). The antibiotic susceptibility of coagulase positive staphylococci (COPS) and coagulase-negative staphylococci (CONS) isolates to 3 antibiotics (Methicillin, Tetracycline and Vancomycin) was determined using disc diffusion method. The results revealed that 80 isolates of S. aureus (82.47%) were resistant to methicillin (MRSA), while 8 isolates (8.24%) were resistant to vancomycin (VRSA) and 18 isolates of S. aureus (19%) were resistant to tetracycline. Sixty four CONS isolates (62.13%) were resistant to methicillin, 28 CONS isolates (27.18%) resistant to tetracycline, and 5 CONS isolates (4.85%) resistant to vancomycin. Deoxyribo nucleic acid (DNA) was extracted from staphylococcal isolates. The genetic determinants of methicillin resistance genes (femA and mecA) were amplified using monoplex PCR technique to identify methicillin-resistant (mecA+) and susceptible (lacking mecA) staphylococci and to identify S. aureus (femA+) and coagulase negative staphylococci (lacking femA). Ninety-six S. aureus isolates (98.96%) were attributed as harbour femA gene. The mecA gene was detected in 91 (93.81%) MRSA isolates, while it was detected in 70 (67%) CONS isolates.