Antibacterial MccM as the Major Microcin in Escherichia coli Nissle 1917 against Pathogenic Enterobacteria.

Probiotic Escherichia coli Nissle 1917 (EcN) possesses excellent antibacterial effects on pathogenic enterobacteria. The microcins MccM and MccH47 produced in EcN played critical roles, but they are understudied and poorly characterized, and the individual antibacterial mechanisms are still unclear. In this study, three EcN mutants (ΔmcmA, ΔmchB, and ΔmcmAΔmchB) were constructed and compared with wild-type EcN (EcN wt) to test for inhibitory effects on the growth of Escherichia coli O157: H7, Salmonella enterica (SE), and Salmonella typhimurium (ST). The antibacterial effects on O157: H7 were not affected by the knockout of mcmA (MccM) and mchB (MccH47) in EcN. However, the antibacterial effect on Salmonella declined sharply in EcN mutants ΔmcmA. The overexpressed mcmA gene in EcN::mcmA showed more efficient antibacterial activity on Salmonella than that of EcN wt. Furthermore, the EcN::mcmA strain significantly reduced the abilities of adhesion and invasion of Salmonella to intestinal epithelial cells, decreasing the invasion ability of ST by 56.31% (62.57 times more than that of EcN wt) while reducing the adhesion ability of ST by 50.14% (2.41 times more than that of EcN wt). In addition, the supernatant of EcN::mcmA culture significantly decreased the mRNA expression and secretion of IL-1ß, TNF-α, and IL-6 on macrophages induced by LPS. The EcN::mcmA strain generated twice as much orange halo as EcN wt by CAS agar diffusion assay by producing more siderophores. MccM was more closely related to the activity of EcN against Salmonella, and MccM-overproducing EcN inhibited Salmonella growth by producing more siderophores-MccM to compete for iron, which was critical to pathogen growth. Based on the above, EcN::mcmA can be developed as engineered probiotics to fight against pathogenic enterobacteria colonization in the gut.

Prospecção de moluscos bivalves no estudo da poluição dos rios Cachoeira e Santana em Ilhéus, Bahia, Brasil / Bivalve molluscs prospection in pollution study from Cachoeira and Santana rivers in Ilheus, Bahia, Brazil

Um levantamento sobre o nível de poluição dos Rios Cachoeira e Santana (Ilhéus, Bahia, Brasil) foi realizado durante um trimestre, por meio da avaliação da qualidade microbiológica da água e de frutos do mar (Crassostrea rhizophorae – ostra-do-mangue e Tagelus plebeius - moapem) extraídos desses rios. Tradicionais indicadores de poluição como coliformes totais (Ct) e coliformes termotolerantes (CT), além de contagem padrão de microrganismos, com isolamento e identificação das enterobactérias, foram determinados nas amostras dos rios, os quais exibiram diferentes níveis de poluição fecal. Foram isolados 68 microrganismos, distribuídos em dez espécies, dentre elas, Salmonella typhi, Escherichia coli e Shigella sp., alertando para o risco do consumo in natura desses moluscos, mesmo quando em conformidade com a legislação estabelecida para CT. A prospecção de moluscos para o acompanhamento dos índices de poluição não se mostrou efetiva considerando a pesquisa de CT em ostras e moapens. Verificou-se também o maior grau de contaminação no Rio Cachoeira, o qual serve de base para distribuição de água na região e como fonte de subsistência, por meio da atividade extrativista, para a população ribeirinha.

A survey about the pollution level of the Cachoeira and Santana Rivers (Ilheus, Bahia, Brazil) was performed for a quarter, through the assessment of the microbiological quality of water and seafood (Crassostrea rhizophorae - oyster and Tagelus plebeius – razor clam) extracted from these rivers. Traditional indicators of pollution such as total coliforms (Ct) and thermtolerant coliforms (CT), and total count of micro-organisms, with isolation and identification of Enterobacteriaceae were determined in rivers samples, which exhibited different levels of faecal pollution. An amount of 68 micro-organisms was isolated, distributed in ten species, among them, Salmonella typhi, Escherichia coli and Shigella sp., warning about the risk of consuming these shellfish in nature, even when there is accordance with the laws established for CT. The bivalve prospection to monitor pollution levels was not effective considering CT detection in oysters and moapens. There was also the highest contamination degree in the Cachoeira River, which is used for water distribution in the region and as livelihood source through extractive activities for the riverside population.

Enteropatógenos em Santos: inquérito bacteriológico na população diarréica com mais de cinco anos de idade / Enteropathogenic bacteria in Santos: a survey in 2 diarrheal population over 5 years old

É relatado o isolamento de enteropatógenos durante o inquérito bacteriológico em Santos, SP. Em 242 coproculturas de pacientes com diarreia aquosa, 42 resultaram positivas. Foram isolados 62,7% de Shigella sp., 27,9% de Salmonella sp. e 9,4% de Escherichia coli LT+. Este inquérito teve duração de duas semanas e foi realizado em virtude do isolamento de 2 cepas de Vibrio cholerae em água de esgoto (AU).