Genetic profile mutation rpoB in clinical isolate of rifampicin-resistant Staphylococcus aureus.

OBJECTIVES: Staphylococcus aureus is one of the bacteria which causes nosocomial infection. Methicillin-Resistant Staphylococcus Aureus eradication using antibiotics combined with rifampicin has shown good results, whereas, adjuvant rifampicin has long been hypothesized to improve the outcome of S. aureus infection treatment. Resistant-rifampicin S. aureus mutates in rpoB gene at some codons. This study was conducted to identify the mutation of rpoB gene in S. aureus which was resistant toward rifampicin. METHODS: In this study, isolates collected in the Microbiology Laboratory of Dr. Seotomo Surabaya Hospital during May-September 2019. Then, the dilution method was carried out to determine the minimum inhibition concentration for resistant-rifampicin and dilution to determine the inhibition zone diameter. After that, DNA extraction was carried out from rifampicin-susceptible isolates as a control and resistant-rifampicin isolates followed by identification of rpoB gene mutations by Polymerase Chain Reaction (PCR) and sequencing. RESULTS: There were nine isolates studied. They were four resistant-rifampicin isolates and four susceptible-rifampicin isolates. In four rifampicin-resistant isolates, the most frequent mutations that occurred was His-481 codon (75%) followed by the Ile-527 codon (25%). Rifampicin-susceptible isolates mutated in Pro-475 and Asn-474 codons. One rifampicin-resistant isolate had two mutations in codons Ile-527 and Asn-474. CONCLUSIONS: The type of mutation that causes the most rifampicin resistance was a missense mutation. The susceptible-rifampicin isolate experienced silent mutations. There was a relation between the type of missense mutation of rpoB gene and rifampin resistance.