[Prevalence of constitutive and inducible resistance to clindamycin in staphylococci isolates from Hajar and Kashani hospitals in Shahrekord, 2008]

ABSTRACT

Resistance to clindamycin [CL] in Staphylococcus aureus is both constitutive and inducible. In the present study, the prevalence of the constitutive and inducible resistance to CL was investigated by disk diffusion and double-disk diffusion [D-test] methods. This descriptive-analytical study was performed on 230 Staphylococcus isolates. D-test was carried out for all the isolates with resistant phenotype for erythromycin and susceptible phenotype for CL. 15 micro g erythromycin and 2 micro g CL disks were placed on plate at a distance of 15 mm. The appearance of D-shaped zones around the strains was checked after proper incubation. Of the 230 staphylococcus isolates, 55.6% were susceptible to CL, 37.5% had constitutive and 5.2% had inducible resistance to CL. The frequencies of constitutive and inducible resistance for CL in methicillin-resistant Staphylococcus aureus [MRSA] isolates were 66% and 9%, respectively and the frequencies of constitutive and inducible resistance for CL in methicillin-susceptible isolates [MSSA] were 15.4% and 2.3%, respectively. Statistical tests revealed the inducible resistance in MRS isolates to be 4.2 times more frequent than that in MSS isolates. The inducible resistance frequency was 10.8- fold in MRSA compared to MSSA isolates. The study results showed that the inducible resistance should be determined by D-test in all methicillin-resistant staphylococcus isolates and also staphylococcus strains resistant to erythromycin and susceptible to CL