Abstract
MRSA is able to generate a modified variety of penicillin binding protein named as PBP2a instead of PBP which makes it resistant against penicillin and methicillin. Production of PBP2a is due to the presence of a gene on Staphylococcal cassette chromosome or SCC termed as “mec-A gene”. SCC is a mobile genetic element carrying many resistance genes. It is because of current antibiotic selection pressure that by now there are eight types (I - VIII) of SCCmec. This research has been designed to determine frequency of SCCmec type IV and V in clinical isolates of MRSA. A total of 70 presumptive MRSA isolates collected from a tertiary care hospital of Lahore were cultured on blood agar, incubated overnight at 37°C aerobically. Next day, they were examined for cultural characteristics, colonial morphology, gram stain, and biochemical profile. Confirmation of MRSA was done by phenotypic disk diffusion method according to (CLSI) 2013 guidelines. mecA gene was also detected at molecular level. Molecular identification of SCCmec type IV and V was done by Nested PCR strategy. A total of 50 isolates were confirmed to be MRSA Molecular detection of SCCmec type IV and V revealed that 11 isolates (22%) possess SCCmec type IV and only 2 isolate (4%) carries SCCmec type V. It is obvious from results that SCCmec type IV and V are present in our population too. Larger study (with larger sample size) might be undertaken to find out actual emergence of SCCmec type IV and V in our population.
Highlights
Distribution of methicillin resistant staphylococcus aureus (MRSA) is worldwide and its incidence varies depending upon geographical location of various regions
After 24 hours they were examined for cultural characteristics, colonial morphology, Gram stain, and biochemical profile. 50 isolates were identified as MRSA using Gram stain catalase, coagulase and Dnase test
The mecA gene is located on the Staphylococcal cassette chromosome mec (SCCmec), which carries methicillin-resistance gene and other antibiotic resistance genes integrated in the S.aureus chromosome
Summary
Distribution of methicillin resistant staphylococcus aureus (MRSA) is worldwide and its incidence varies depending upon geographical location of various regions. A survey report documented the prevalence of MRSA from 42% to 51% in Pakistan [1] [2]. MecA gene encodes an extra penicillin-binding protein (PBP2a). Main causative agent responsible for this resistance is carriage by the MRSA strains mecA gene. It has low affinity for all β-lactam antibiotics [3] [4]. Many techniques have been used for epidemiological typing of MRSA which helps to study evolutionary relationship of different MRSA strains. There is very little epidemiological data about frequency of SCCmec type IV and V in Pakistan
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