SCREENING AND IDENTIFICATION OF AQUATIC BACTERIOCINOGENIC BACILLUS STRAINS INHIBITING CLINICAL METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS AND VANCOMYCIN RESISTANT ENTEROCOCCUS FROM PAKISTAN

Objective: The purpose of the current study was to screen and identify novel bacteriocinogenic strains from marine, fresh and estuarine water bodies which can serve as alternatives to the antibiotics, as an antibiotic resistance is on the rise. Methods: Altogether seven fresh, brackish, and marine water samples from various regions of Sindh were collected. All the aquatic bacterial strains were isolated by standard plate count and overlay methods. The bacteriocinogenic strains were screened by spot agar, stab and overlay, cross streak and agar well-diffusion techniques. Results: Of the total 146 isolates, 41 (28%) were bacteriocinogenic, among which 28 (68%) were isolated from freshwater, 12 (29%) from marine and 1 (3%) from brackish water. The most significant bacteriocinogenic strains among the isolates were identified as Bacillus coagulans, Bacillus simplex, Bacillus macerans and Bacillus circulans. When tested against 17 significant pathogens, these strains could inhibit various clinical drug-resistant Gram-positive pathogens such as Staphylococcus aureus and methicillin-resistant S. aureus, Streptococcus pyogenes, Streptococcus agalactiae and vancomycin-resistant Enterococcus and Corynebacterium diptheriae. Furthermore, Escherichia coli and Klebsiella spp. were observed to be sensitive against two bacteriocinogenic strains of B. coagulans. Furthermore, 59% of the aquatic isolates were sensitive against one of the bacteriocinogenic strain indicating competitive antagonism phenomenon. Conclusion: This research study reveals the bacteriocinogenic potential of indigenous aquatic isolates against drug resistant clinical pathogens as well as against fish pathogens.