Enteropathogenicity of Vibrio parahaemolyticus in the ligated rabbit ileum

Abstract

The enteropathogenicity of Vibrio parahaemolyticus was investigated by contrasting the effects of whole cells, cell fragments, cell-free preparations, and media constituents injected into rtabbit ileal loops. Three of 20 cultures utilized were Kanagawa-negative strains from seawater and sea fish. The remaining 17 cultures included both Kanagawa-positive and-negative strains from Japanese victims of gastroenteritis. Broth culture filtrates concentrated 10-fold by dialysis against 30% Carbowax were unreactive, whereas lyophilized filtrates, regardless of Kanagawa type, as well as all sterile broth preparations containing .5% NaCl gave positive reactions in the rabbit gut. In contrast, crude lysates derived from broth cultures of Kanagawa-positive strains caused loop dilatation; lysate supernatants were unreactive. Lysates of cells washed from brain heart infusion agar were more reactive than lysates from Trypticase soy agar-grown cells. When agar-grown cell lysates prepared by disruption in saline were dialyzed against distilled water, they were devoid of gut reactivity. Reactivity was restored in dialysands resuspended in saline and in dialysates concentrated 10fold. The agar-grown cell lysates exhibited Kanagawa-type hemolysis. Our data support the conclusion that the rabbit loop reactivity observed with lyophilized, cell-free culture filtrates may result from excessively elevated NaCl concentrations, and that a toxic factor associated with large-cell particles may be dialyzable, depends on saline for expression, and resembles the Kanagawa hemolysin.

Hemagglutination and adhesiveness of epidemiologically distinct strains of Vibrio parahaemolyticus

“…Rabbit ileal loop assay. Reactions of the 12 test strains in the ligated ileal loop were as expected from our previous work (5,(26)(27)(28). Five of the six K+ strains and none of the K-strains were positive when tested in the permanently ligated model ( Table 1).…”

“…A test culture was recorded as positive if the ratio of loop fluid volume to loop length was threefold greater than the volume-to-length ratio of negative controls. In our considerable experience with the model (5,(26)(27)(28)(29), a strain has been considered positive if loops tested positive at least two of three times in separate animals.…”

“…Vibrio parahaemolyticus is a widely distributed estuarine bacterium that can cause acute gastroenteritis in humans (1). Strains can generally be divided into two groups on the basis of their epidemiological distribution (2,20), their activity in the rabbit ileum (5,29), and their ability to hemolyze a high-salt blood agar medium (Kanagawa phenomenon) (30). Hemolytic strains, termed Kanagawa positive (K+), are recovered commonly from patient stool specimens but rarely from seafood or environmental sources and can dilate ligated rabbit ileal loops.…”

“…Etiological inconsistencies that indicate possible alternative virulence factors abound. For example, some K+ organisms fail to dilate the ligated rabbit ileum (5,29), whereas Korganisms are sometimes the only strains of V. parahaemolyticus isolated from patients (20,24). Despite many attempts, however, no satis-factory evidence for a true enterotoxin has been found (29).…”

Experimental pathogenicity and mortality in ligated ileal loop studies of the newly reported halophilic lactose-positive Vibrio sp

“…Although some L+ Vibrio test loops produced an accumulated fluid (milliliter) to loop length (centimeter) ratio of about 1, premature death of tested animals prohibit a conclusive statement concerning the ability of L+ Vibrio to elicit a positive fluid response in ligated leal loops. Although Kanagawa-positive strains of V. parahaemolyticus have previously been reported to yield positive ileal loop results (3,16,18), none of the test loops from four rabbits showed any accumulation. It is significant, however, that all 12 rats and 5 of 6 rabbits whose loops received L+ Vibrio injections died before the prescribed 18-h incubation period.…”