Inducible clindamycin resistance in methicillin-susceptible and methicillin-resistant Staphylococcus aureus of inpatient, outpatient and healthy carriers in Bosnia and Herzegovina.

AIM To investigate the iMLSB prevalence in 142 methicillin-sensitive (MSSA) and 48 methicillin-resistant (MRSA) in-patient (65), outpatient (75), and healthy carrier (150) Staphylococcus aureus isolates in Zenica-Doboj Canton, Bosnia and Herzegovina. METHODS Disk diffusion testing by placing clindamycin (CLI) and erythromycin (ERY) disks 15 mm apart (edge to edge) on a Mueller-Hinton agar, as per CLSI guideline was performed. Two distinct induction phenotypes labelled as D and D+, and three noninduction phenotypes designated as Neg, R (constitutive, cMLSB), and S (susceptible). Methicillin-resistance was confirmed by the presence of mecA gene by PCR. The genetic characterization was performed using spa-typing and the algorithm based upon repeat patterns (BURP). RESULTS iMLSB was detected in six (2.1%) isolates, of which five (3.5%) (two outpatients and three carriers) were MSSA, and one (2.1%) (outpatient) MRSA. One of them, D+ phenotype (iMLSB) was obtained from a carrier (MSSA). None of the inpatients had iMLSB. HD phenotype was not detected. One (MRSA) isolate has shown negative phenotype. Two strains with iMLSB originated from skin and soft tissue (MRSA) and eye infection (MSSA) belonged to the same MLST CC8, with different spa-types (t451 and t008, respectively). R phenotype (cMLSB) was detected in two (inpatient) isolates (0.7%). CONCLUSION D test identified 2% of wrongly reported isolates as clindamycin sensitive. Despite low prevalence of S. aureus with iMLSB , it is a significant finding that they were mostly MSSA, and all were isolated from outpatients or carriers. D-test becomes an imperative part of routine antimicrobial susceptibility test for all S. aureus isolates.