ظهور سویه های استافیلوکوکوس اورئوس مقاوم به پریستینا مایسین و کاهش حساسیت یافته به تئیکوپلانین در میان پرسنل پرستاری در اردبیل، ایران

Title

Emergence of pristinamycin resistant and teicoplanin reduced susceptibility staphyloccous aureus isolates among nursing staff in Ardabil, Iran

English Abstract

Background and objective: Staphylococcus aureus is one of the most important cause of nosocomial infections. Emergence of Methicillin resistant Staphylococcus aureus strains (MRSA) pushed staphylococcal infections into new era of antimicrobial therapy. Microbiologically they are usually multidrug resistant strains and do not response to many conventional antibiotics that this limits proper therapeutical options against staphylococcal infections. This study was aimed to evaluate the antimicrobial resistance pattern of Staphylococcus aureus strains isolated from nursing staff in a teaching university hospital against Pristinamycin, Linozolid and Teicoplanin. Methods: This study was carried out on total 41 S.aureus strains isolated from nursing staff. Minimum inhibitory concentration (MIC) of Oxacillin to the isolates was determined by agar dilution method. At first the antibiotic sensitivity of isolates against pristinamycin, linozolid and teicoplanin were tested by the Kirby Bauer disk diffusion method and the MIC of pristinamycin and teicoplanin to resistant or susceptibility reduced strains were further determined by using E-test strips. All procedures were carried out and interpreted according to CLSI. Results: Among 41 isolates 6 (15%) were resistant to methicillin. The oxacillin MICs were >512 μg/mL for 5/6 and 4 μg/mL for 1/6 MRSA isolates. Both MSSA and MRSA isolates were sensitive against linezolid. All MSSA isolates were sensitive to teicoplanin but one (16.6%) MRSA isolate had intermediate resistance pattern for teicoplanin. The mean inhibition zone diameter of teicoplanin sensitive isolates for MRSA and MSSA were 1.48 and 1.62 mm respectively. The teicoplanin MICs against MRSA were 0.25 μg/ml for 2/6, 0.1 μg/ml for 3/6 and 0.05 μg/ml for 1/6 isolates and for selected MSSA isolates the MICs were between 0.1 to <0.001 μg/ml. 4 (11.4 %) of 35 MSSA and 5 (83.3 %) of 6 MRSA isolates were resistant against pristinomycin. The prisyinamycin MICs against MRSA were >240 μg/ml for 5/6 and 0.01 μg/ml for1/6 isolates and for MSSA (pristinamycin resistant according to disk diffusion method) were >240 μg/ml for 2/4 and 30 μg/ml for 2/4 isolates. Conclusion: These antibiotics are not used in the study setting and at all in Iran for patient management. Emergence of pristinamycin resistant and teicoplanin reduced susceptibility Staphylococcus aureus strains in the absence of antibiotic selective pressure indicate that these antibiotics can not be advocated for empirical therapy for treatment of Staphylococcal infections.

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