Background and Aim: Due to the role of spreading infections in hospitals, drug resistant Staphylococcus aureus nasal carriers have always been considered. Clindamycin is one of the effective drugs against the bacteria, but some isolates have acquired induced resistance. This study was preformed to investigate the prevalence and characteristics of resistant isolates in nasal carriers of hospital origin, in Imam Reza Hospital, as the largest hospital in Kermanshah province.

  Materials and Methods: This cross-sectional study was performed on the patients which their nasal samples were positive for Staphylococcus aureus after hospitalization, in the year 2009. Sensitivity of the isolates to erythromycin and clindamycin was determined. Induced, constitutive resistance and MS phenotype were evaluated by D-test. Data were analyzed by means of SPSS version 16 and chi-square test at the significant level of P<0.05.

  Results: Among 1269 admitted patients, 210 (16.5%) were hospital acquired-nasal carriers for the bacteria. The frequency of resistant isolates to erythromycin and clindamycin was 41.5% and 23.3%, respectively. The induced, constitutive and MS phenotype were 10%, 23.3% and 8.6% of isolates, respectively. A significant difference between MRSA (19.5%) and MSSA (3.9%) isolates with induced resistance was seen (P=0.001).

  Conclusion: Carrier patients of the resistant variants of Staphylococcus aureus are always a serious threat to their own health and others. Regarding the frequency of induced resistance to clindamycin, screening Staphylococcus aureus isolates in this regard, seems to be essential.