Molecular Detection of Linezolid Mutations among Methicillin Resistant Staphylococcus Aureus Isolated from Bovine Mastitis and Human Sources in Jordan

Methicillin-resistant Staphylococcus aureus (MRSA) is rapidly overcoming the current array of antibiotics.Resistance to linezolid usually develops in gram-positive bacteria because of mutations in domain V of 23S rRNA, 50S ribosomal proteins L3, L4, and L22, and acquisition of the cfr gene.The study aimed to detect the pattern of sensitivity and resistance of MRSA isolates to linezolid, as well as to detect and characterize various mutations associated with linezolid resistance.A total of 113 MRSA isolates (26 from mastitis, 38 from university students, 49 from farm workers) were studied for resistance against 13 antimicrobials by the disc diffusion method, and were investigated for their resistance against linezolid antibiotic using E-test strips.Briefly, to detect the G2576T point mutation, the 23S rRNA gene (domain V region) was amplified by PCR, digested with NheI, and subjected to high-resolution melting (HRM).PCR and sequencing of rplC, rplD, rplV, and cfr genes were carried out to identify the presence of linezolid's various mutations.All isolates showed resistance toward penicillin, oxacillin, and cefoxitin, and a significant difference in resistance percentages between isolates was detected only in erythromycin, gentamycin, and linezolid.Further, (76.9%) of isolates exhibited sensitivity toward linezolid.Among the linezolid-resistant MRSA isolates, only one isolate contained the cfr gene, while other isolates contained various mutations in the 23S rRNA gene and in 50S ribosomal proteins L3, L4, and L22.