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Prevalence and antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus clones: A study at Taksin Hospital, Bangkok, Thailand

Chanwit Tribuddharat^a, Chalermsri Pummangura^b, Maytinee Srifuengfung^a, Piyawan Pipobwatthana^c, Huttaya Thuncharoon^c, Vipavee Rodjun^b, Piriyaporn Chongtrakool^a, Somporn Srifuengfung^b,*

 
ABSTRACT:     : Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen in human diseases. Thirtyseven clinical clones from different patients were tested for a molecular study of the mecA gene and multilocus sequence types (ST). Total genomic extraction, followed by a polymerase chain reaction (PCR) for DNA amplification with specific primers for mecA, and specific primers for various ST were used. Molecular typing for the study of genetic relationships among clones was performed by enterobacterial repetitive intergenic consensus (ERIC)-PCR. Antimicrobial susceptibility testing for all clones to 9 drugs was performed by the disk diffusion and vancomycin Etest. The presence of mecA was detected in all clones. The most common ST was MRSA-ST30, accounting for 81.1% of all MRSA tested, followed by MRSA-ST8/ST97/ST779 (8.1%), MRSA-ST239 (2.7%) and MRSA-nontypeable clones (8.1%). Molecular typing by ERIC-PCR demonstrated DNA fingerprints with corresponding results with sequence types. All clones were susceptible (70?100%) to fosfomycin, fusidic acid, gentamicin, tetracycline, trimethoprimsulfamethoxazole and vancomycin [minimal inhibitory concentration (MIC) range, MIC50 and MIC90 were 0.25? 1.0, 0.5 and 0.75 ?g/ml, respectively by using E-test] but resistant to ciprofloxacin, clindamycin and erythromycin. Inducible macrolide, lincosamide-type B streptogramin resistance (iMLSB) phenotype was 5.4% while constitutive MLSB phenotype was 91.9%. For MRSA-ST30 clones, 96.7% were multi-drug resistant (MDR) with the most common pattern being resistant to ciprofloxacin, clindamycin and erythromycin. These results suggest the importance of MRSA in the field of epidemiology at a hospital in Thailand.

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* Corresponding author, E-mail: somporn.sri@mahidol.ac.th

Received 16 Apr 2021, Accepted 13 Nov 2021