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In vitro effect of fusidic acid on staphylococcus strains with macrolide-lincosamid-streptogramin B resistance

Abstract number: P591

Sesli Cetin E., Gunes H., Aynali A., Kaya S., Cicioglu Aridogan B., Demirci M.

Objectives: Antimicrobial resistance of staphylococcal isolates continues to be a problem for clinicians worldwide. A major problem in the treatment of S. aureus infections is the ability of this pathogen to be resistant to a number of antibiotics. Relationship between meticillin resistance and resistance to other antibiotics has been reported in previous investigations. Fusidic acid displays its antibacterial activity via inhibiting protein synthesis without binding to bacterial ribosomes. This unique mechanism of action prevents cross-resistance between fusidic acid and other antibiotics. This study was carried out in order to determine the in-vitro effect of fusidic acid on stapyhlococcal isolates with macrolid-lincosamide-streptogramine B resistance.

Methods: The study included 532 staphylococcus isolates consisting of 59 MRSA, 101 MSSA, 200 MRCNS and 172 MSCNS. Testing for MLSB and was accomplished by the 'D-zone' test in accordance with the recommendations of the CLSI. Fusidic acid resistance was investigated by agar disk diffusion method according to the criteria of 'Comité de L'antibiogramme de la Société Française de Microbiologie'.

Results: Of 532 staphylococcal isolates, 62.4% were susceptible and 37.6% were resistant to MLSB antibiotics. 62.5% of the resistant isolates exhibited a constitutive resistance phenotype, whereas 37.5% were inducibly resistant. All of 101 MSSA isolates were susceptible to fusidic acid. Susceptibility rate to fusidic acid was higher among strains without MLSB resistance (82.8%) and strains with iMLSB (82.7%) resistance than that observed among isolates with cMLSB (58.4%) resistance. We have also determined that susceptibility to fusidic acid was significantly lower among MRCNS isolates with cMLSB resistance phenotype.

Conclusion: The relatively low susceptibility to fusidic acid detected in our study among strains with MLSB resistance accompanying to meticillin resistance, may be explained with the reports suggesting that multidrug-resistant phenotype can develop as a consequence of continuous exposure of an organism to an antibiotic to which the organism is chromosomally highly resistant. These results indicated that, although fusidic acid can stil be considered as an alternative agent for the treatment of infections caused by meticillin resistant staphylococcal strains, it should be kept in mind that susceptibility rates may be lower than expected if the isolate is also resistant to MLSB antibiotics.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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