Evaluation of the bacteriocins activity against pathogens associated with gastroenteritis isolated in the children´s hospital of San Miguel de Tucuman

NAVARRO, S; CHALON, M; MERLETTI, G; BARRIONUEVO, E; ASSA, J; MINAHK, C; BELLOMIO, A

Cordoba

Congreso; XI Congreso Argentino de Microbiología General; 2015

Asociación Civil de Microbiologia General

Bacteriocins of Gram (-) bacteria are active on phylogenetically related to the producer strain and similarly, those bacteriocins ofGram (+) bacteria are active on Gram (+) bacteria. Objective: To study the in vitro antibiotic effect of different bacteriocins onclinical isolates in the Children?s Hospital of Tucumán to select those that present greater antibiotic potency for the constructionof chimeric peptides. The bacteriocins were obtained from the bacteria producing supernatants. To evaluate the antimicrobialactivity, a modification of the Kirby-Bauer method was performed. A standardized amount of bacteria (0.5 McFarland) wasspread uniformly on the surface of a Müller-Hinton agar plate to obtain a bacterial lawn. Then 10 µl of a solution of eachbacteriocin were spotted on plates. The plates were incubated for 18-24 hours at 37°C. After the incubation different sensitivitydegrees were determined according to the diameter and turbidity of the halos. Antimicrobial activity units (AU/ml) werecalculated as the reciprocal of the highest dilution showing growth inhibition zone against Escherichia coli MC4100. Theantibiotic effect of the microcins (Mcc) E492, H47 and V were assayed against Gram (-) bacterial pathogens. From the resultswe observed that strains of Shigella sonneii were sensitive to the three microcins. However, the different serotypes of Shigellaflexneri showed different degrees of sensitivity. Salmonella Typhimurium and Enteritidis showed clear inhibition halos to MccVand MccE492. Adding EDTA (5 mM) to the culture medium increased the inhibitory effect of antibiotics. Some resistant bacteriabecame sensitive. Most cases of bacterial gastroenteritis in Tucuman are associated with the Gram (-) bacteria Shigella flexneri(70%), Shigella sonneii (16 %), Shigella boydii (1%), and Salmonella spp. (5%). Furthermore, 92% of the S. flexneri isolateswere resistant to ampicillin and 92% of isolates of S. sonneii proved resistant to trimethoprim-sulfamethoxazole. The microcins,particularly MccE492, have an antibiotic effect on most of the bacteria causing gastroenteritis in children of Tucuman. Thereforeit would be appropriate for use in the development of antimicrobial hybrid peptides in tandem with bacteriocins of gram (+) toobtain hybrids antimicrobial peptides with broad antimicrobial spectrum.