A Cohort study (prospective and observational) was performed to study the prevalence of Methicillin resistant Staphylococcus aureus from the healthy individuals of community, hospitalized patients and associated health-care workers and indigenous plants essential oils were screened as new, improved & potent antibacterial/s against resistant strains of MRSA.
The method involved isolation and identification of MRSA from surgical wounds of hospitalized patients & associated health care workers in a tertiary care hospital in Lahore and healthy volunteers from the community. Plant essentials oils & extracts were evaluated for their antibacterial activity against selected MRSA isolates. Oils were recovered by steam distillation using an all-glass distillation assembly. Then in vitro sensitivity and MICs of plant essential oils were determined using vancomycin and linezolid as commercial standards. The essential oils were screened further for the active constituents by column chromatography using various solvents and identification of compounds were performed by GC/MS analysis and the fractions which showed prompt results were evaluated for antimicrobial activity against the MRSA isolates in quest to find new therapeutic options. Finally effective essential oils and their active fractions were studied for their toxicity using in vitro Genotoxic assays such as Ames and Comet assays. To further ensure their beneficial effects antimutagenic effect of the essential oils were also studied.
Prevalence of S. aureus among patients was 52.9%, in HCWs 86.5% and in community 74% with an overall percentage of 72.6%. Among S. aureus those declared as MRSA were 91.8% from patients, 50.6% from HCWs and 59.5% from community with an overall percentage of 62.2% MRSA. Among the isolated MRSA overall 90.6% were Coagulase positive and 75.2% were biofilm positive.
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The pattern of MRSA resistance against current antibiotics have shown an overall increase in the resistance with maximum shown for lincomycin followed by tetracycline, ampicillin, fusidic acid, amoxicillin and piperacillin with tazobactam. The most effective options among current regime were tigecyclin, amikacin and meropenem showing an overall least resistance. Resistance against linezolid was observed with an overall percentage of 25.6 % and vancomycin 33.3% by disc diffusion method.
The MRSA isolates resistant to one or more groups of antibiotics were declared as MDRs. Among patients and health-care workers all were declared as MDRs where as in community 93.1% isolates were MDRs.
Upon Protein profiling using whole cell proteins 44 bands of the polypeptides were produced with molecular size 10-200kDa from the three sampling groups and were categorized into 5 clusters showing an overall significance correlation with each other explaining an interesting fact that all these strains were interlinked establishing the fact of flow of hospital acquired MRSA in the community and vice versa. This analysis also gave an insight in explaining the fact of horizontal transmission of infection within the hospital.
Keeping in view the raise in resistance among current available antibiotics indigenous medicinal plants essential oils were screened for active constituents exhibiting anti-bacterial effects against MRSA isolates.
Maximum yield was obtained from Carum copticum followed by Cuminum cyminum and minimum yield was obtained in case of Zingiber officinale. Upon qualitative analysis of all five essential oils Carum copticum essential oil showed zones of inhibition greater than the standards vancomycin and linezolid followed Cuminum cyminum and Zingiber officinale in all three
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sampling groups. Anethum sowa and Myristica fragrans essential oils showed no activity against MRSA.
Minimum inhibitory concentration of the three essential oils determined by micro broth dilution method indicated that Carum copticum showed least value in all three types of MRSA isolates followed by Zingiber officinale and Cuminum cyminum.
Effective essential oils were further fractioned using silica gel gravity columns. All the fractions obtained were screened for the anti-bacterial activity against all three types of MRSA isolates. Only fraction F1 of Carum copticum showed activity greater than pure essential oil and the two commercial standards of vancomycin and linezolid.
For the identification of active constituents GC/MS analysis was performed on all three essential oils and their respective fractions. In case of fraction F1 the most dominant constituents were Carvacrol, p-Cymene, Ʈ-Terpinene and Apiol. In other two plants none of the fractions were effective. Therefore it was concluded to use pure essential oils in case of Zingiber officinale and Cuminum cyminum rather than their individual fractions and incase of Carum copticum Fraction F1 has shown superior activity.
Finally these essential oils were tested for possible mutagenic effect using bacterial reversion mutation assay and Comet assay. No mutagenic effects were observed at MIC and above doses. These effective essential oils were also evaluated for possible antimutagenic effect. Both Carum copticum and Zingiber officinale essential oils showed strong antimutagenic effects and weak antimutagenic effect by Cuminum cyminum. Upon analysis of nuclear damage none of the plants essential oils and fraction F1 of Carum copticum showed genotoxic effects and indicated to be safe. Thus from the study it was concluded that Carum copticum essential oil and its fraction F1 were the most effective to be further investigated as an alternative treatment for MRSA infections.