High Prevalence of tetM as Compared to tetK Amongst Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates from Hospitals in Perak, Malaysia

Background Methicillin-resistant Staphylococcus aureus (MRSA) has become a great concern to public health as it is one of the most successful and adaptable human pathogens. Antibiotic is still the main treatment for infected patients. Therefore, identifying the prevalence of antibiotic resistant genes is essential to reduce the mortality and morbility rate of MRSA-infected patients. Objectives This study aimed to identify the prevalence of tetracycline resistance of MRSA and its determinants (tetK and tetM) and their relationship with SCCmec types. Methods One hundred and seventeen MRSA isolates were collected from different body sites (eg, blood, pus, tissue, synovial fluid, eye, spinal fluid, wound, and nasal cavity) from patients with age of 1- to 90-years old. Antibiotic susceptibility tests were carried out in order to determine tetracycline resistant MRSA. Total DNA was extracted using modified spin column method and subjected to duplex PCR for the amplification of genes of interests (mecA, tetK and tetM) and multiplex PCR for the SCCmec types identification. Results Out of 117 MRSA isolates, 76.1% were found to be tetracycline resistant, 8.5% were intermediate resistant and 15.4% were susceptible to tetracycline. Among the tetracycline resistant isolates, 97.8% carried tetM, while 42.7% carried tetK. The two genetic determinants were found mostly associated with SCCmec type III MRSA, whereby 95.0% harbored tetM while 37.0% co-carried tetK. tetK was presented alone (9.1%) in SCCmec type IV MRSA, although tetM was found in SCCmec type V MRSA. Conclusions Tetracycline determinant tetM is more prevalent than tetK in this region of study and most of these determinants are found encoded in SCCmec type III. Since tetracycline antibiotic is losing its efficacy, this antibiotic should be prescribed more wisely.