RESUMO
The present investigation was focused to study the antagonistic potential of actinobacterial strain TK2 isolated from Thirukurungudi Hills (Western Ghats, Tamil Nadu), against selected drug resistant bacterial pathogens. Of the 9 clinical bacterial strains, S. aureus was found to be resistant against methicillin and vancomycin while the remaining 8 gram negative pathogens were confirmed as extended spectrum beta lactamase (ESBL) producers. Strain TK2 showed good antagonistic activity against all the bacterial pathogens, except the three isolates of P. aeruginosa. Strain TK2 produced the antimicrobial activity on 4th day of incubation when growing on ISP2 agar medium whereas the same strain showed activity only on 8th day of incubation when it was grown on ISP2 broth. Of the various solvents tested for extraction, bioactive compound was extracted only in ethyl acetate. The crude extract showed 14-18 mm inhibition zone in disc diffusion method. The crude extract produced two spots in thin layer chromatography (TLC) in chloroform: methanol (30:60) solvent system. In bioautography, the second spot (Rf value 0.685) showed activity. The active compound was purified by preparative TLC, which showed maximum activity (15-20 mm inhibition) against test pathogens. Based on the results of chemical screening, the active compound was identified as sugar containing substance. Strain TK2 showed good growth on various growth media and culture conditions. Based on the studied phenotypic characteristics strain TK2 was identified as the species of the genus Streptomyces. Of the various growth parameters tested, ISP2 medium, glucose, pH 7, 1% NaCl and temperature 300C was influenced the antagonistic activity of strain TK2. Strain TK2 will be a potential for the isolation of bioactive compound(s) which will be a candidate for the development of antibiotic against drug resistant bacterial pathogens.
RESUMO
Aim: To screen the spread of resistance in ESBLs producer’s particularly non lactose fermenting gram negative Acinetobacter spp. and Pseudomonas spp. and study antimicrobial activity with crude extract from novel marine actinomycetes in India. Methods: Fifty clinical isolates in a period of one year were processed and the antibiotic susceptibility was determined by double disk approximation test, the ESBLs production was screened with phenotypic confirmatory methods using disks of amikacin, meropenem, netilimicin, ciprofloxacin, gentamicin, tigecycline and piperacillin along with cephalosporin disks. Antimicrobial activity of the crude extract was determined by agar plug method. Results: The isolates collected from different samples were found resistant to third and fourth generation cephalosporins. ESBL production was detected in 56 % to 66 % of the isolates, amikacin and netilmicin showed 50% to 60% resistance they were also found resistant to carbapenems, 86% resistance was observed in Acinetobacter spp. Two strains PM21 and PM27 selected from 24 actinobacterial isolates had zone of inhibition >21mm. Conclusion: A high level of antibiotic resistance was found in Acinetobacter spp. in our study and may reflect the scenario in India. Earlier detection and reporting of ESBL producers will help in treating individual cases and also in controlling the spread of these resistant genes to other sensitive nosocomial isolates. The medical need for new agents is most acute and the future of this work aims to identify one such novel compound from marine actinobacteria.