Urogenital infections affect millions of people every year worldwide. The treatment of these diseases usually requires the use of antimicrobial agents, and more recently, the use of probiotic lactic acid bacteria (LAB) cultures for the management of vaginal infections has been extensively studied. In this work, 11 vaginal lactobacilli isolates, previously obtained from healthy patients, were studied to screen microorganisms with probiotic properties against Candida spp. The LAB were tested for their ability of auto-aggregation, coaggregation with C. albicans, C. glabrata, C. krusei, and C. tropicalis, adhesion to Caco-2 epithelial cells and production of lactic acid and hydrogen peroxide (H2O2). All lactobacilli isolates tested were able to auto-aggregate (ranging from 25.3% to 75.4% assessed at 4 hours of incubation) and to co-aggregate with the four Candida species into different degrees; among them L. crispatus showed the highest scores of coaggregation. The highest amount of lactic acid was produced by L. salivarius (13.9 g/l), followed by L. johnsonii (6.5 g/l), L. acidophilus (5.5 g/l), and L. jensenii (5.4 g/l). All isolates produced H2O2 , but the highest levels (3 -10 mg/l) were observed for L. acidophilus, L. crispatus, L. gasseri, L. johnsonii, and L. vaginalis. Only L. agilis, L. jensenii, L. johnsonii and L. ruminus were able to adhere to epithelial Caco-2 cells. Among the isolates evaluated, L agilis, L. jensenii, L. johnsonii, and L. ruminus exhibited simultaneously several desirable properties as potential probiotic strains justifying future studies to evaluate their technological properties in different pharmaceutical preparations for human use.

A atividade de uma preparação bruta de bacteriocina produzida por Leuconostoc mesenteroides 11, isolado de peito de frango, foi avaliada a 8ºC e 15ºC, contra Listeria monocytogenes. O patógeno foi inoculado em uma preparação bruta da bacteriocina e sua população foi enumerada depois de 0,5 e 10 dias de incubação. O título da preparação de bacteriocina foi determinado no tempo 0 e após 10 dias de incubação em ambas as temperaturas. Como controle negativo, foi utilizada uma cepa não produtora de bacteriocina, Leuconostoc mesenteroides A13. A bacteriocina de L. mesenteroides 11 inibiu parcialmente L. monocytogenes a 8ºC, mas a 15ºC a bacteriocina não foi capaz de impedir a multiplicação do patógeno. Nossos resultados sugerem que o uso da bacteriocina semi-purificada de L. mesenteroides 11 provavelmente não será adequada como único obstáculo para impedir a multiplicação de L. monocytogenes em alimentos.

The activity of a crude preparation of bacteriocin produced by the chicken meat isolate Leuconostoc mesenteroides 11, was evaluated at 8ºC and 15ºC against Listeria monocytogenes. The pathogen was inoculated in a crude preparation of the bacteriocin and its population was enumerated after 0.5 and 10 days. The title of the bacteriocin in the preparation was determined immediately before inoculation and after 10 days of incubation at both temperatures. As a negative control, a non-bacteriocin producing strain, Leuconostoc mesenteroides A13, was used. Bacteriocin of L. mesenteroides 11 partially inhibited L. monocytogenes at 8ºC, but at 15ºC it was unable to prevent growth of the pathogen. Our findings suggest that the use of the semi-purified bacteriocin of L. mesenteroides 11 probably will not be suitable as a single hurdle to prevent L. monocytogenes growth in foods.

No presente trabalho, foram estudadas as bacteriocinas produzidas por seis linhagens bacterianas: duas culturas Lactobacillus sake, duas de Lactobacillus curvatus, uma de Leuconostoc mesenteroides, uma de Leuconostoc sp 12. As atividades inibitórias foram quantificadas pelo método da diluição crítica, utilizando-se os indicadores Lactobacillus sake ATCC 15521 e Listeria monocytogenes. As bacteriocinas produzidas foram caracterizadas também quanto à sensibilidade a enzimas, faixa de temperatura na produção, termoestabilidade, estabilidade em diferentes pHs e modo de ação (bactericida ou bacteriostático) frente a Listeria monocytogenes. Nenhuma bacteriocina foi destruída pela pepsina, mas todas foram sensíveis à proteinase K, tripsina e alfa-amilase (exceto a bacteriocina produzida por Leuconostoc sp 12, que foi insensível a alfa-amilase). Lactobacillus sake 1, Leuconostoc mesenteroides 11 e Lactobacillus sake 16 apresentaram atividade antilisterial, sendo a maior inibição observada para Lactobacillus sake 1 e Leuconostoc mesenteroides 11 (12.800UA/mL). Lactobacillus sake 1 e Lactobacillus curvatus 5 produziram as bacteriocinas mais termoestáveis. Lactobacillus sake 1 produziu a bacteriocina com maior estabilidade a variações de pH. Todas as bactérias láticas produziram bacteriocina entre 4ºC e 30ºC, sendo esta propriedade muito interessante para futuras aplicações em produtos cárneos refrigerados.

In this work, the bacteriocins produced by six bacterial strains were studied (Lactobacillus sake 1, Lactobacillus curvatus 5, Leuconostoc mesenteroides 11, Leuconostoc sp 12, Lactobacillus curvatus 14 and Lactobacillus sake 16). Title of inhibitory activity was determined by critical dilution assay, using Lactobacillus sake ATCC 15521 and Listeria monocytogenes as indicator microorganisms. The inhibitory compounds were also characterized with respect to stability to the action of enzymes, thermostability, stability in several pHs and mode of action (bactericide or bacteriostatic) towards Listeria monocytogenes. No bacteriocin was destroyed by pepsin, but all of them were destroyed by proteinase K, trypsin and alpha-amylase (except that alpha-amylase did not inactivate the bacteriocin produced by Leuconostoc sp 12). Lactobacillus sake 1, Leuconostoc mesenteroides 11 and Lactobacillus sake 16 exerted antilisterial activity. The more active strains against Listeria monocytogenes were Lactobacillus sake 1 and Leuconostoc mesenteroides 11 (12.800 AU/ml). Bacteriocins produced by Lactobacillus sake 1 and Lactobacillus curvatus 5 presented the highest thermal stability. The bacteriocin of Lactobacillus sake 1 was the most stable to pH variations. All LAB produced bacteriocin in the range of temperature from 4ºC to 30ºC and this property is of great interest for future applications in refrigerated meat products.