Bacteroides Fragilis induces conformational alterations in Trichomonas Vaginalis ultrastructure in an in vitro interaction

Bacteroides genus are commonly found on mucous membranes, including the female genital tract, acting as agents for several site infections. Anaerobic infections are usually polymicrobial and endogenous. Trichomonas vaginalis, the trichomoniasis etiologic agent, is a facultative anaerobic flagellated parasite spread worldwide. The purpose of this study was to explore the association between vaginal bacteria and T. vaginalis, as well as to understand factors that may favour the infection of T. vaginalis. We have, therefore, used T. vaginalis trophozoites and the species Bacteroides fragilis, which is considered the most important in its genus, once it is the most commonly isolated bacteria from endogenous infections. The parasite-bacteria interaction was performed in different proportions in periods varying from 1 to 12 hours applying viability tests. The data were analyzed to compare the parasite viability in vitro in the presence and absence of B. fragilis. The results indicate that in the 1:100 proportion postinteraction analysis, ultrastructural alterations were noticeable after 6 hours. After 8 hours, T. vaginalis viability decreased, and after 12 hours of interaction no viable trophozoites were found. These data suggest that the parasite can deal with B. fragilis in short interaction periods. However, in longer interaction periods the trophozoites collapse, indicating that B. fragilis may produce toxic metabolites against T. vaginalis activity.

Pathogen killing pathogen: antimicrobial substance from Acinetobacter active against foodborne pathogens.

INTRODUCTION: Antimicrobial substances (AMS) produced by bacteria may reduce or prevent the growth of pathogenic and spoilage microorganisms in food. In this study, 16 isolates of Acinetobacter baumannii/calcoaceticus (ABC) complex, previously obtained from reconstituted infant milk formula (IMF) samples and the preparation and distribution utensils from the nursery of a public hospital, were used to screen for AMS production. METHODOLOGY: Antimicrobial substance production and spectrum of activity assays were performed by agar-spot assay. Optimization of growth conditions for AMS production was also evaluated. RESULTS: Three (17.6%) isolates, namely JE3, JE4, and JE6, produced AMS against the principal indicator strain Salmonella enterica subsp. enterica serotype Typhi ATCC 19214. JE6 was also able to inhibit strains of Klebsiella pneumoniae, Proteus vulgaris, and Bacillus cereus, a Gram-positive bacteria. Remarkably, JE6 was able to inhibit all the tested resistant and multidrug-resistant (MDR) strains of the ABC complex and Shigella dysenteriae associated with IMF and utensils, indicating a potentially valuable application. AMS produced by JE6 does not appear to be affected by proteolytic enzymes and the producer strain showed specific immunity to its own AMS. CONCLUSION: This study highlights AMS produced by Acinetobacter with applications against MDR spoilage and foodborne pathogens - some of them, infectious disease causing agents - which, to our knowledge, has not been previously described.

Presence of the cfxA gene in Bacteroides distasonis.

In this study we investigated the presence of the cfxA gene (encoding a class A beta-lactamase) in 73 strains of the Bacteroides fragilis group belonging to the species B. distasonis (34), B. vulgatus (14), B. thetaiotaomicron (8), B. merdae (6), B. caccae (9) and B. ovatus (2) isolated from human intestinal microflora of healthy children and adults. Employing specific primers to the cfxA gene, a 312-bp amplified fragment was obtained in 2 strains of B. vulgatus and 9 strains, the majority from children, of B. distasonis. The expression of this enzyme was analysed by determining the MICs to cefoxitin and cefotaxime and values varied from 2 to >256 microg/ml of both cefoxitin and cefotaxime. Sequence analysis of the amplicons corresponding to the cfxA gene from B. distasonis and B. vulgatus revealed identical sequences between these isolates and high similarity with other beta-lactamase genes of anaerobes such as cfxA of B. vulgatus (99%) and cfxA2 of Prevotella intermedia (99%), both sequences of which deposited in Genbank under accession numbers U38243 and AF118110, respectively. However, a fragment obtained from a B. distasonis strain (EC17-4) showed a unique RFLP profile and 87% nucleotide similarity with cfxA and cfxA2 genes. These results seem to suggest a dissemination of these resistance determinants among Bacteroides species.