Background: In recent years,Staph.aureus,both coagulase positive and negative,have shown resistance to commonly used antibiotics used to treat infections.Over the last two decades,methicillin resistant strains (MRSA) have also been on a rise specially in patients admitted to ICUs and immunocompromised patients. The drug resistance mechanism of MRSA has been studied extensively in the past decade.Our study aims to study the sensitivity pattern of Staph. aureus in different clinical specimens and to study thedifferent resistance mechanisms. Objective: The present retrospective study highlights the susceptibility pattern and resistance mechanism ofStaph.aureus in clinical specimens obtained in our Microbiology department from June 2015 to June 2016. Materials and Methods: This was a retrospective study of Staph.aureus isolates from different clinical specimens including urine, blood, pus, vaginal swab, semen, aural swab, BAL fluid, conjunctival swab etc obtained from out patients at our Diagnostic Clinic Microbiology department from June 2015 to June 2016 and reported in VItek II (Biomerieux) according to CLSI guidelines. A total of 278 samples were reviewed. Results: Out of278 Staph.aureus isolates grown in the lab from different clinical specimens the sensitivity pattern showed highest sensitivity for Tigecycline(91.7%),followed bypenicillin (91.3%), ,Gentamycin (80.9%),tetracycline (66%),levofloxacin(65.4%),Rifampicin(63.6%), Linezol id(63.3%), Daptomycin(50.3%), Vancomycin (46,7%), Teicoplanin (42%). 117 cases showed resistance to aminoglycosides by KAN (APH(3")III) mechanism,Cefoxitin screen was positive in 166 patients,APH(3")III in 117 patients,MecA gene in 113 cases,ANT(4’)(4"))In 106 patients,acquired penicillinase in 77 ,SGASGB in 49 cases,efflux mechanism in 30 cases and inducible clindamycin resistance in 24 cases. Conclusion: According to our study Tigecycline, followed by Penicillin, Gentamycin ,Tetracycline, Levofloxacin and Linezolid are the antibiotics of choice for treating Staph aureus infections in the present scenario. With the introduction of automated equipments like Vitek II our understanding of the resistance mechanism is increasing.A larger study population would be required for a better understanding of resistance mechanisms.
Keywords: Staph Aureus; Vitec II; Resistance Mechanism; MRSA; Meca Gene.Corresponding Author
: Hawaldar Ranjana**