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BACTERIOCIN-LIKE INHIBITORY SUBSTANCES (BLIS) FROM INDIGENOUS CLINICAL STREPTOCOCCI: SCREENING, ACTIVITY SPECTRUM AND BIOCHEMICAL CHARACTERIZATION

SAMIA AHMAD, ALFRED IQBAL AND SHEIKH AJAZ RASOOL

Abstract: Two hundred streptococcal isolates from varied human indigenous clinical sources were screened for bacteriocinogenic activity by both direct and deferred methods (70% were showing bacteriocin-like activity). All the isolates were found highly bioactive against most Gram positive bacteria but less active against the Gram positive and totally inactive against themselves. Proteolytic enzymes rapidly inactivated the antagonistic activity whereas, glycolytic and lipolytic enzymes had no effect. Bioactivity remained stable in the presence of several organic solvents and detergents. Bacteriocin preparations could be stored at 4ºC for 2 months without loss of activity and remained stable at 60ºC for 60min and 80ºC for 40min and at 100ºC for 30min. Bioactivity was manifested within a wide range of 2-8 pH with the exception of enterocin ESF63 that was stable at low pH range of 5-8.5. All preparations were resistant to chloroform vapours. Different bacteriocin titre in terms of activity unit (AU/mL) was found against different sensitive/indicator strains.

Department of Microbiology, University of Karachi, Karachi-75270, Pakistan.