BACKGROUND Prevalence of Methicillin-Resistant Staphylococcus aureus (MRSA) in India ranges from 30 to 70% which leads to high mortality, increased economic burden and high treatment failure when compared to MSSA. Rapid and accurate detection of MRSA is essential to take measures for infection control and also to prevent unnecessary use of antibiotics.
MATERIALS AND METHODSProspective observational study was carried out in our tertiary care hospital over a period of 6 months (May-October 2017). All Staphylococcus grown among 240 various clinical samples received were tested for MRSA by four phenotypic methods -cefoxitin and oxacillin disc diffusion test and MIC oxacillin E test and oxacillin resistant screen agar test (ORSA) with mecA-PCR as gold standard.
RESULTSA total of 103 out of 200 (51.5%) bacterial isolates were Staphylococcus aureus. Pus from diabetic wound yielded high number of growth (42%) followed by blood (36%) which is alarming note. 55.4% were identified as MRSAs by PCR; most common presenting group was >50 years (36.8%) followed by infants (28%). Cefoxitin disc method has the highest sensitivity and specificity of 98.2% & 100% followed by E test (94.2% & 95.8%) and ORSA (87.5% & 94.2%). Oxacillin disc diffusion method had the least 79.5% & 92.9%. Most MRSA isolates were multi drug resistant.
CONCLUSIONCefoxitin disc diffusion when combined with Oxacillin agar or E test will be helpful to detect all MRSA strains including hyper production of betalactamases. As these phenotypic assays are simple and relatively cheap, this can be used as an alternative to PCR in resource constraint settings. (2) In India the prevalence of MRSA ranges from 30 to 70% which leads to high mortality, increase economic burden. (3,4) ' Financial or Other Competing Interest': None. Submission 04-01-2018, Peer Review 01-02-2018, Acceptance 07-02-2018, Published 12-02-2018, Anuppanadi, Madurai-625009, Tamilnadu. E-mail: Jhansi_charles@yahoo.co.in DOI: 10.14260/jemds/2018/197 MRSA treatment will be more problematic as these strains often show resistance to wide range of antibiotics compared to methicillin susceptible isolates. (3) Therefore, rapid and accurate detection of MRSA is very essential in order to choose appropriate therapy, to take necessary measures for infection control and also to prevent unnecessary use of glycol-peptides antibiotics.
KEYWORDSMRSA strains harbour the mecA gene, which encodes a penicillin binding protein (PBP2a) with low affinity for all ß-lactam antibiotics including methicillin which has limited therapeutic option. (5) Hence methods used to identify MRSA from clinical samples should have high sensitivity and specificity and most importantly the result should be available within a short time. Different phenotypic methods such as oxacillin and cefoxitin disc diffusion test, oxacillin agar screening test, and determination of minimum inhibitory concentration (MIC) for oxacillin and cefoxitin are available in clinical laboratories. (6)(7)(8)(9) Phenotypic expression is affected b...