The acute diarrheal disease cholera is caused by the marine bacterium Vibrio cholerae. A type VI secretion system (T6SS), which is structurally similar to the bacteriophage cell-puncturing device, has been recently identified in V. cholerae and is used by this organism to confer virulence toward phagocytic eukaryotes, such as J774 murine macrophages and Dictyostelium discoideum. We tested the interbacterial virulence of V. cholerae strain V52, an O37 serogroup with a constitutively active T6SS. V52 was found to be highly virulent toward multiple Gram-negative bacteria, including Escherichia coli and Salmonella Typhimurium, and caused up to a 100,000-fold reduction in E. coli survival. Because the T6SS-deficient mutants V52ΔvasK and V52ΔvasH showed toxicity defects that could be complemented, virulence displayed by V. cholerae depends on a functional T6SS. V. cholerae V52 and strains of the O1 serogroup were resistant to V52, suggesting that V. cholerae has acquired immunity independently of its serogroup. We hypothesize that the T6SS, in addition to targeting eukaryotic host cells, confers toxicity toward other bacteria, providing a means of interspecies competition to enhance environmental survival. Thus, the V. cholerae T6SS may enhance the survival of V. cholerae in its aquatic ecosystem during the transmission of cholera and between epidemics.

https://www.pnas.org/content/pnas/107/45/19520.full.pdf

The Vibrio cholerae type VI secretion system displays antimicrobial properties.

Summary
We studied 148 strains of Pseudomonas aeruginosa isolated from nonbacteriaemic infections and healthy carriers (group I) and 50 strains isolated from patients with bacteriaemia (group II). More than 90 per cent. of the strains in both groups produced lipase, esterase, protease, and a haemolysin most active on ox and rabbit erythrocytes. Between 60 and 90 per cent. gave a positive egg-yolk reaction, produced nuclease (DNAase and RNAase), lecithinase, elastase, staphylolytic enzyme, and another haemolysin most active on sheep and horse erythrocytes. No significant difference between the two groups in the formation of any of these factors was found. The strains of the two groups showed more than 100 different phage-typing patterns when tested with a set of 22 phages; only a few strains were untypable and no phage-typing pattern predominated. About one-third of all the strains belonged to Habs' serotype 6 and the rest of the strains were rather evenly distributed between the other serotypes without any difference between the two groups.

Production of Enzymes and Toxins by Hospital Strains of Pseudomonas Aeruginosain Relation to Serotype and Phage-Typing Pattern

The related species V. parahaemolyticus and A. hydrophila produce several extracellular toxins and enzymes some of which are potential virulence factors. The thermostable direct hemolysin of V. parahaemolyticus (Kanagawa-hemolysin) is produced by the majority of strains isolated from human patients but its role in the pathogenesis of gastroenteritis is not clear. This hemolysin is cytotoxic to a wide variety of mammalian cells, it is lethal to mice and the cell membrane is a glycoconjugate. These properties are shared with the AEromonas beta-hemolysin (aerolysin) and the two hemolysins may be related. A. hydrophila produces an enterotoxin which increases the intracellular cAMP content of intestinal cells, induces steroidogenesis in adrenal Y1 cells, and fullfils the criteria for a cytotonic enterotoxin but appears not to be antigenically related to cholera toxin. There is so far no conclusive evidence for the production of a similar enterotoxin in strains of V. parahaemolyticus. Strains of both specie...

Toxins of Vibrio Parahæmolyticus and Æromonas Hydrophila

Significant antimicrobial action was detected in vitro and in vivo in phenothiazines that are applied to humans as neuroleptics or antihistamines. Both Gram-positive and Gram-negative bacteria were equally sensitive, with the MIC varying between 25 and 100 μg/ml with most agents. Some phenothiazines were bactericidal, while others were bacteriostatic in action. Similar activity could be observed in isoflavonones obtained from the plants Sophora spp. Trifluoperazine and methdilazine exhibited antimycobacterial properties as well, and in experimental animals the latter showed definite healing properties. Chlorpromazine and thioridazine were able to eliminate R-plasmids in drug-resistant bacteria. Artificially synthesized Benzo[α]phenothiazines could effectively suppress adenovirus oncogene expression. Phenothiazines have now been shown to inhibit efflux pumps in multidrug-resistant bacteria.

Antibacterial Activity of Artificial Phenothiazines and Isoflavones from Plants

Publisher Summary Cholera is a disease of bacterial origin. It is not only important to recognize the disease clinically, but also to attempt as complete an identification of the causative organism as possible using various epidemiological typing procedures. This chapter explains the practical procedures currently available for the characterization, as well as a working background of the relevant theoretical knowledge. V. cholera is asporogenous, single curved or rigid rod with a single polar flagellum. It is indophenols oxidase positive and produces acid without gas from glucose. The aim of all typing systems is to identify strains within a species with a degree of precision that makes it safe to assume that all the isolates from an epidemic are truly identical and have therefore originated from a single parent strain. Of the three methods of typing V. cholera—serotyping, phage-typing and bacteriocin biotyping—serological typing was the earliest to be developed.

Chapter V Principles and Practice of Typing Vibrio cholerae

Bacteriocins of Vibrio cholerae have been demonstrated against enterobacterial and vibrio indicator organisms by conventional techniques. Abundant bacteriocin production took place on casein hydrolysate-yeast extract, tryptic soy, digest broth, proteose-peptone, and neopeptone agars. Essential factors were a citrate-phosphate buffer concentration of 0.5 to 0.7%, at p H 7.5 to 7.6, and cold shock. Thermal treatment of indicator organisms at 45 C for 12 min increased the percentage of typable strains. The bacteriocins of V. cholerae appeared to be powerful diffusible bactericidal agents. By using 8 indicator strains, 11 bacteriocin types have been recognized among 425 strains, of which 87% are typable at present. Images

Bacteriocin Typing of Vibrio cholerae.

Summary. 
A total of 307 strains consisting of 89 Vibrio cholerae, 37 NAG vibrios, 4 Aeromonas sp., 20 Pseudomonas aeruginosa, 47 shigellae, 59 Escherichia coli, 27 Proteus mirabilis and 25 salmonellae were examined for their opacity reaction in Tween 80 agar medium. Strong reactions occurred with 87 V. cholerae, 26 NAG vibrios, 2 Aeromonas and 5 Pseudomonas strains; and weak and slow positive reactions were noted in only 6 strains of NAG vibrios and 3 of Pseudomonas; no reaction was observed among the remaining strains. The study showed that Tween 80 hydrolysis can be used as a test for characterization of the Vibrio and Aeromonas groups and for their differentiation from the Enterobacteriaceae.

Sati Adhya

Papers

Bacteriocin Typing of Vibrio cholerae.

The hydrolysis of Tween 80 by vibrios and aeromonads.