UV light Induces Transposition of blaZ gene Resulting in High Expression of β-lactamase in a Clinical Isolate of Staphylococcus aureus Sensitive to Ampicillin

In the present study an ampicillin sensitive Staphylococcus aureus confirmed from the MIC results, was isolated from a patient and the nature of S aureus was confirmed by its ability to grow in modified Baird Parkar media. This strain when exposed to UV radiation of 280 nm for 10 seconds could grow even in the presence of ampicillin (100mg/ml) and nitrocefin (50mg/ml). The specific activity of beta-lactamase in the extracellular secretions of UV exposed S. aureus showed the presence of beta-lactamase enzyme indicating successful expression of the gene. Southern hybridization with PVGKS -1 probe and amplification of beta-lactamase gene with primers designed from blaZ gene sequence of S aureus from the chromosomal DNA of UV exposed S. aureus indicated that blaZ gene was located on the chromosomal DNA. Amplification of transposase gene using specific primers upstream of blaZ gene of Tn552 indicated that this gene might have been transposed on to the chromosomal DNA of the Staphylococcus aureus and where the gene successfully expressed in the organism making the organism resistant to beta-lactam antibiotics, such transposition of trnasposons on exposure to slight pressure and its cross infections among patients can be life threatening in hospitals.