CHALON Miriam Carolina
congresos y reuniones científicas
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.C.; MERLETTI, G; BARRIONUEVO, E; ASSA,J; MINAHK, C.J; BELLOMIO, A
Congreso; Congreso Argentino de Microbiologia General; 2015
Objective: To study the in vitro antibiotic effect of different bacteriocins on clinical isolates and to select those that present greater antibiotic potency for the construction of chimeric peptides. Materials and Methods: The microcins were obtained from the bacteria producing supernatants. The producers strains were grown to DO600= 0.6 at 37°C in M9 medium supplemented with 2,2-dipyridyl. To produce bacteriocins, LAPTg culture medium was used and the strains were incubated overnight at 30°C. To evaluate the antimicrobial activity, a modification of the Kirby-Bauer method (agar diffusion method) was performed. A standardized amount of bacteria (0.5 McFarland) was seed on the surface of an agar plate Müller-Hinton uniformly to obtain a bacterial lawn after inoculation. Then 10 μl of the bacteriocins or microcins were spread on plates. The plates were incubated for 18-24 hours at 37°C. After the incubation different sensitivity degrees were determined according to the diameter and turbidity of the halos. Antimicrobial activity units (AU/ml) were calculated as the reciprocal of the highest dilution showing growth inhibition zone against E. coli MC4100 or Listeria innocua 7 (used as indicator strains). Results: Antibiotic effect of microcins E492 (MccE492), H47 (MccH47) and V (MccV) were studied. From the results we observed that Shigella sonneii was sensitive to the three microcins. Moreover, different serotypes of Shigella flexneri were analyzed. Serotypes 1 and 3 were resistant to the studied microcins. Nevertheless serotypes 2 and AA479 were sensitive to MccE492 with clear zone inhibition ≥ 10 mm. Salmonella Typhimurium and Enteritidis showed clear halos, indicating a high degree of sensitivity to and MccV microcin E492. We studied the effect of EDTA on the strains that were resistant. Thereby serotypes 1 and 3 of S. flexnery showed turbid halos of inhibition against MccE492 and MccV, and clear halos against MccH47. In the case of Salmonella Typhimurium, which was resistant to MccH47, the presence of a small turbid halo was found. Furthermore, the addition of EDTA increased the lethal effect of MccE492. The activity of bacteriocins of Gram (+) bacteria, Enterocin CRL35, Pediocin PA-1 and Enterocin A were assayed against different strains of Listeria. Listeria welshimeri and Listeria seeligeri were completely resistant to the action of the bacteriocins. Two strains of L. monocytogenes belonging to the Spanish Type Culture Collection isolated from sick animals were sensitive to all bacteriocins showing clear halos in all cases. In addition, two strains of L. innocua were also sensitive, presenting clear halos of inhibition ≥ 10 mm against enterocin CRL35 and halos ≤ 10 mm in the presence of enterocin A and pediocin PA-1. Conclusions: The most cases of bacterial gastroenteritis are associated with the Gram (-) bacteria Shigella flexneri (70%), Shigella sonneii (16 % ), Shigella boydii (1%), Salmonella spp. (5%), Aeromonas spp. (6%), Vibrio cholerae O1 and non O139 (2%). Furthermore, 92% of the S. flexneri isolates were resistant to ampicillin and 92% of isolates of S. sonneii proved resistant to trimethoprim-sulfamethoxazole. Listeriosis is a disease caused by L. monocytogenes, this bacteria is a very common food contaminant. The infection causes a spectrum of diseases, ranging from febrile gastroenteritis to invasive disease, including bacteremia, sepsis, and meningoencephalitis.