COMPARATIVE EFFICACY OF AZADIRACHTA INDICA ORGANIC EXTRACTS AGAINST METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS CLINICAL ISOLATES

Abstract

The current study targeted the isolation and molecular identification of methicillin-resistant Staphylococcus aureus (MRSA) from various clinical samples (n=100). The samples were processed for bacterial isolation based on cultural, morphological and biochemical profiles followed by amplification of nuc gene encoding for thermostable nuclease of S. aureus. The isolates were screened phenotypically for methicillin resistance using cefoxitin or oxacillin discs and the genomic DNA of each isolate was screened for mec-A gene. Minimum inhibitory concentration (MIC) of vancomycin was also determined for each MRSA isolate. Organic extracts of Azadirachta indica leaves were prepared using ethanol, methanol and chloroform solvents followed by determination of in vitro activity of each extract against the MRSA isolates. A total of 47 isolates were identified as Staphylococci based on cultural, morphological and biochemical profiles, whereas 41 isolates were confirmed as S. aureus based on nuc gene. Phenotypically 13/41 isolates showed resistance to cefoxitin or oxacillin discs and 13/13 isolates were found positive for mec-A gene, hence termed as MRSA. All the isolates were sensitive to vancomycin and showed MIC (0.5-2µg/ml). The mean zone of inhibition was measured as 15.38±1.39 mm and 15.92±1.71 mm for ethanolic and methanolic extracts at 40% concentration, respectively. Whereas the highest zone was measured as 18.38±1.71 mm for chloroform extract at 60% concentration. Altogether, the results indicated that MRSA isolates pose a significant public health threat. However, organic extracts showed significant activity against MRSA isolates along with vancomycin as potential antimicrobial drug.