Journal of Pure and Applied MicrobiologyVol. 4 No. 2

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

O. Hari Prasad, V. Nagarjuna, Ch. Lakshmi Prasanna, D. Vasu, V.G. Yugandhar, U. Venkatesh Prasad, P.V.L.N. Srinivas Rao² Abhijit Chaudhary3, O.V.S. Reddy4 and P.V.G.K. Sarma¹*

Department of Biotechnology, ²Department of Biochemistry, ³Department of Microbiology, Sri Venkateswara Institute of Medical Sciences, Tirupati - 517 507, India. 4Department of Biochemistry, Sri Venkateswara University, Tirupati - 517 502, India.

Received on 06 April 2010 and accepted on 27 May 2010

 

ABSTRACT

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 b–lactamase in the extracellular secretions of UV exposed S. aureus showed the presence of b–lactamase enzyme indicating successful expression of the gene. Southern hybridization with PVGKS -1 probe and amplification of b-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 b-lactam antibiotics, such transposition of trnasposons on exposure to slight pressure and its cross infections among patients can be life threatening in hospitals.

Keywords : Staphylococcus aureus, b-lactamase, Tn552, PVGKS-1, nitrocefin.