In Vitro Susceptibility of Chloramphenicol Against Methicillin-Resistant Staphylococcus aureus

Abstract

Objective: To determine the in vitro susceptibility of chloramphenicol against methicillin-resistant Staphylococcus aureus. Study Design: Cross-sectional study. Place and Duration of Study: Department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi, from January to June 2012. Methodology: One hundred and seventy four isolates of methicillin-resistant Staphylococcus aureus were included in this study using cefoxitin (30 ìg) disc for detection. Minimum inhibitory concentration (MIC) of chloramphenicol against MRSA was determined by using E-strip (AB BIO DISK). The susceptibility was determined by swabbing the Mueller-Hinton agar (MHA) plates with the resultant saline suspension of MRSA and applying E-strip of chloramphenicol from AB Biodisk Sweden and determining the MIC of chloramphenicol (in ìg/ml). Clinical and Laboratory Standards Institute (CLSI) recommendations of ² 8 ìg/ml being sensitive, 16 ìg/ml as intermediate and ³ 32 ìg/ml as resistant were followed in interpreting the results. Results: Out of the 174 MRSA isolates, 132 (75.86%) isolates were susceptible to chloramphenicol with MICs of ² 8 ìg/ml, 38 (21.84%) were resistant ³ 32 ìg/ml while 4 (2.30%) were in intermediate range with MIC of 16 ìg/ml. Conclusion: Chloramphenicol has shown good in vitro activity against MRSA and is likely to have a key role in the treatment of MRSA infections providing us a good alternative to newer expensive antimicrobials in resource limited countries.