Genotypic Characterization of Macrolides Resistance in Clinical Isolates of Staphylococcus Aureus from Rawalpindi, Pakistan

Objective: To determine the patterns of resistance among different macrolides and to detect macrolide resistance genes in Staphylococcus aureus collected from different clinical samples. Study Design: Cross-sectional observational study. Place and Duration of Study: The clinical samples sourced from the Pathology Labs of Railway Hospital, Tehsil Head Quarter (THQ) Hospital Taxila and Wah General Hospital Wah Cantt, Pakistan was collected from 01August 2017 to 01 February 2018. Materials and Methods: One hundred non-repetitive clinical isolates were obtained from different clinical samples (pus, urine, sputum and blood). Each Staphylococcus aureus isolate was obtained from only one sample, to avoid repetition of strain. They were selected on the criteria of their growth with bright yellow color colony formation on mannitol salt agar (MSA) media along with the color change of media from red to yellow and coagulase positive results. Kirbey-Baur disk diffusion test was followed for the detection of antimicrobial sensitivity, whereas genotypic resistance drift was determined using PCR. Results: Highest frequency of Staphylococcus aureus was observed in pus samples i.e. 45 (40.2%). Out of 100, 34 isolates of Staphylococcus aureus were resistant to macrolides group. Among 34 resistant isolates the frequency of ermC gene was 25 and msrAwas 14 respectively, whereas all isolates were negative for ermAgene. Maximum resistance was observed against erythromycin, n=33 (29.5%) and minimum against clarithromycin, n=26 (23.3%). The highest susceptibility trend was seen against Azithromycin, n=62 (55%). Conclusion: Resistance of Staphylococcus aureus may vary with different antibiotics within the same group. A high frequency of erythromycin resistance was seen in this study. The most predominant resistance was for ermC, among the resistance genes in isolates.