Detection of fusidic acid resistance determinants among Staphylococcus aureus isolates causing skin and soft tissue infections from a tertiary care centre in Chennai, South India

Background

Fusidic acid (FA)- an inhibitor of protein synthesis has been used for treating superficial and some systemic infections caused by Staphylococcus aureus. Fusidic acid resistance in S. aureus has been reported throughout the world with prevalence ranging from 0.5% to 50% and is due to i) point mutation in bacterial fusA or fusE gene and ii) by acquired FA resistance determinants fusB, C and D. Indian report of fusidic acid resistant S. aureus (FRSA) is based on phenotypic detection. Hence, this study was done to detect acquired FA resistance determinants.

Methods

The study included 54 isolates of S. aureus collected from skin infections between Jan to Mar 2011 from a tertiary hospital in Chennai. MRSA was screened by cefoxitin disc diffusion method and PVL-MRSA detection was done by multiplex-PCR. FA resistance was screened by disc diffusion method and acquired resistance determinants were detected by multiplex-PCR.

Results

Of the 54 S. aureus isolates, 32(59.2%) were found to be MRSA. A total of 13(24.1%) isolates were found to carry pvl gene of which 4 were MRSA. Two of the 54(3.7%) isolates were found to be FRSA and harbored fusC gene. Both FRSA isolates were from non-hospitalized patients and they were using FA for topical treatment.

Conclusion

We report for the first time in India the presence of acquired FA resistant determinant fusC gene in community isolate of methicillin susceptible S. aureus. Indiscriminate use of FA needs to be avoided to prevent the emergence of FRSA.