Virulence associated factors in bacteria from water bodies in Belém, Pará, Brazil: bacteriological composition and threat to public health

A lack of sewage treatment contaminates water bodies threatens human health by spreading waterborne gastroenteritis. This is a particular problem for developing countries, where the risks associated with surface water contamination remain largely unknown. To understand the risk associated with sewage contaminations of water bodies, we evaluated the microbiological indicators of water quality and isolated bacterial strains from water bodies from the city of Belém, Pará, Brazil. The strains were identified by biochemical and serological tests and polymerase chain reactions (PCRs). The thermotolerant coliforms and Escherichia coli presented values above 1,000 (NMP/100 mL) biweekly from August 2012 to November 2015, without a significant statistical difference between sampling periods (Kruskal–Wallis p > 0.05). The Tucunduba river's water presented contamination levels similar to those in a sewage pumping station (Dunn test p > 0.05). From 240 bacterial isolates, we identified 163 Vibrio cholerae, 8 Vibrio mimicus, 24 E. coli, and 5 Salmonella spp. The isolates of V. cholerae demonstrated N-acetylglucosamine (NAG) profile (Non-O1 and Non-O139) and 18 expressed the stn/sto gene. No E. coli was shown to be potentially pathogenic. The results revealed that water bodies in Belém were constantly contaminated by sewage and fecal microorganisms, including the potential circulation of pathogens in viable and cultivable form.

Characterization of Potential Virulence Factors of Vibrio mimicus Isolated from Fishery Products and Water

Vibrio mimicus is a Gram-negative bacterium that is closely related to V. cholerae and causes gastroenteritis in humans due to contaminated fish consumption and seafood. This bacterium was isolated and identified from 238 analyzed samples of sea water, oysters, and fish. Twenty strains were identified as V. mimicus according to amplification of the vmhA gene, which is useful as a marker of identification of the species. The production of lipases, proteases, and nucleases was detected; 45% of the strains were able to produce thermonucleases and 40% were capable of producing hydroxamate-type siderophores, and the fragment of the iuT gene was amplified in all of the V. mimicus strains. Seventy-five percent of V. mimicus strains showed cytopathic effect on Chinese hamster ovary (CHO) cells and destruction of the monolayer, and 100% of the strains were adherent on the HEp-2 cell line with an aggregative adherence pattern. The presence of virulence factors in V. mimicus strains obtained from fishery products suggests that another member of the Vibrio genus could represent a risk to the consumer due to production of different metabolites that allows it to subsist in the host.

Core and Accessory Genome Analysis of Vibrio mimicus

Vibrio mimicus is an emerging pathogen, mainly associated with contaminated seafood consumption. However, little is known about its evolution, biodiversity, and pathogenic potential. This study analyzes the pan-, core, and accessory genomes of nine V. mimicus strains. The core genome yielded 2424 genes in chromosome I (ChI) and 822 genes in chromosome II (ChII), with an accessory genome comprising an average of 10.9% of the whole genome for ChI and 29% for ChII. Core genome phylogenetic trees were obtained, and V. mimicus ATCC-33654 strain was the closest to the outgroup in both chromosomes. Additionally, a phylogenetic study of eight conserved genes (ftsZ, gapA, gyrB, topA, rpoA, recA, mreB, and pyrH), including Vibrio cholerae, Vibrio parilis, Vibrio metoecus, and Vibrio caribbenthicus, clearly showed clade differentiation. The main virulence genes found in ChI corresponded with type I secretion proteins, extracellular components, flagellar proteins, and potential regulators, while, in ChII, the main categories were type-I secretion proteins, chemotaxis proteins, and antibiotic resistance proteins. The accessory genome was characterized by the presence of mobile elements and toxin encoding genes in both chromosomes. Based on the genome atlas, it was possible to characterize differential regions between strains. The pan-genome of V. mimicus encompassed 3539 genes for ChI and 2355 genes for ChII. These results give us an insight into the virulence and gene content of V. mimicus, as well as constitute the first approach to its diversity.