Evidence for the direct involvement ofβ-hemolysin inAeromonas hydrophila enteropathogenicity

Stelma, Gerard N.; Johnson, Clifford H.; Spaulding, P L

doi:10.1007/bf01568406

Cited by 42 publications

(23 citation statements)

References 28 publications

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“…Singh and Sanyal [6] reported that several non-haemolytic A. caviae strains switched to produce haemolysin after consecutive passages through rabbit ileal loops. Similar to /3-haemolytic A. hydrophila strains [21], several A. caviae strains also caused significantly more fluid accumulation than the a-and non-haemolytic isolates [6]. These studies, in addition, emphasized that the fl-haemolysin caused significant changes in intestinal permeability and it is more prevalent among Aeromonas sp.…”

Section: Discussionmentioning

confidence: 80%

“…Aerolysin of A. hydrophila [21,23], salmolysin of A. salmonicida [24] and fihaemolysin of A. sorbia [22] are also produced extracellularly during the growth of the bacteria. The fl-haemolysin of A. caviae resembles that of Porphyromonas gingivalis [25] as they are stimulated by both Mg2" and Ca2+ ions and inhibited by EDTA whereas an exotoxin of Proteus vulgaris, P. mirabilis and P. morganii [26] and lysolipoid endotoxin of Pseudomonas pseudomallei [27] required only Ca2+ for their enhanced activity.…”

Section: Discussionmentioning

confidence: 99%

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Characterisation of haemolytic activity fromAeromonas caviae

Karunakaran

Devi

1994

Epidemiol. Infect.

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SUMMARYAeromonas caviae, an enteropathogen associated with gastroenteritis, displays several virulence characteristics. Studies on the kinetics of growth of A. caviae and expression of fl-haemolytic toxin revealed that A. caviae produced maximum haemolytic activity extracellularly during the stationary phase. Preliminary studies on the properties of A. caviae haemolysin suggested that divalent cations (Mg2+ and Ca2+ ) and thiol compounds, dithiothreitol and mercaptoethanol enhanced the haemolytic activity. Addition of L-cysteine, glutathione and EDTA reduced the haemolytic activity. The iron chelator, 2-2' bipyridyl, significantly inhibited the growth of A. caviae possibly by iron limitation, with parallel enhancement of haemolysin production compared to A. caviae grown in excess of iron. These results suggest that A. caviae produces only ,1-haemolysin, which resembles the haemolysins reported for several other bacteria and the activity might be regulated by environmental factors especially iron. INTRODUCTIONThere is increasing evidence that the enteropathogen Aeromonas caviae is a causative agent of gastroenteritis [1][2][3][4][5][6] and is a predominant isolate among the microbiota of diarrhoeal stool specimens of infants, from intestinal and extraintestinal infections, and from aquatic ecosystems [4,[7][8][9][10]. The regulation and expression of putative microbial virulence factors by the environment and cytoadherence to host cells are essential events in the establishment of pathogenicity. A. caviae has various such potential pathogenic attributes. It produces either or both thermostable metalloprotease and a thermolabile serine protease [11, 12]. A. caviae has been shown to adhere to host cells [4,13,14] and cause structural damage; and even cell death in some cases by displaying cytotoxic factors [4,6,15]. A. caviae produces an extracellular heat-stable cytotoxin that is lethal to HEp-2 cells [4,16] and a cytotoxic enterotoxin that exhibits cross-reaction with the cholera toxin [4,6,13,15]. It also encodes either

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Section: Discussionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Characterisation of haemolytic activity fromAeromonas caviae

Karunakaran

Devi

1994

Epidemiol. Infect.

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“…Since Aeromonas strains produce a variety of biologically active extracellular substances, including haemolysins [12,13] and enterotoxins [20][21][22], a number of studies have concentrated on the roles of exotoxins in enteropathogenicity, and ,8-haemolysin is considered to be a likely pathogenic factor [13]. However, epidemiological investigations suggest that production of haemolysin can serve as a marker for discrimination between species but does not distinguish between pathogenic and nonpathogenic strains, because most strains of A. hydrophila and A. sobria are haemolytic regardless of their source [8].…”

Section: Discussionmentioning

confidence: 99%

“…Methods for the discrimination between isolates that are pathogenic in man and those from the environment is clearly needed. Although /1-haemolysin might seem to be a likely pathogenic factor [12,13], failure of haemolytic strains to cause diarrhoea in human volunteers suggests that haemolysin per se is not the sole determinant of virulence [14].…”

Section: Introductionmentioning

confidence: 99%

Mannose-resistant adhesion of motileAeromonasto INT407 cells and the differences among isolates from humans, food and water

1991

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SUMMARYAeromonas has been recognized as an important enteropathogen, but factors related to its virulence have not been clarified. For most enteric pathogens, attachment is a prerequisite for infection and for the effective delivery of toxins to the intestinal epithelial cells. We examined a total of 273 strains isolated from stool, food and environmental specimens by an assay for mannose-resistant adhesion to INT407 cells in vitro. Seventeen of the 102 faecal isolates were adhesive strains with more than 10 bacteria adhering per cell, while only 2 of the 118 isolates from foods and river water adhered to the cells (P < 0001). It is possible that the adhesion might serve as a marker for discrimination between the pathogenic and nonpathogenic isolates. The 8 highly adhesive strains with more than 20 adhering organisms per cell were scrutinized for the mechanism of adhesion. No correlation was apparent between the adhesion to INT407 cells and hydrophobicity. It was noted that fucose inhibited the adhesion of four strains as well as haemagglutination by them. Electronmicroscopic studies showed the presence of flexible and curvilinear fimbriae in only 2 of the 8 highly adhesive strains.

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“…In pioneering studies by Burke and colleagues (25,26), a close association between the expression of a cell-free hemolysin by aeromonads and enterotoxigenic activity in suckling mice was noted, although evidence directly linking these two biological activities was lacking. Subsequent studies by Asao et al (7,8) and Bloch and Monteil (20) with purified hemolysin preparations unequivocably demonstrated this protein to be enterotoxigenic in rabbit ileal loops and in suckling mice; antibodies raised against this purified hemolysin completely neutralized both the cytotoxic and the enterotoxic properties (81,128). Besides this potential role in gastrointestinal disease, the beta-hemolysin has also been implicated in systemic disease, as isogenic mutants from which the aerolysin gene has been specifically deleted show reduced lethal capabilities in mice, as assessed by LD50s (32).…”

Section: Structural Featuresmentioning

confidence: 97%

Recent advances in the study of the taxonomy, pathogenicity, and infectious syndromes associated with the genus Aeromonas

1991

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Over the past decade, the emergence of Aeromonas species as bona fide human pathogens and their probable role as etiologic agents of bacterial gastroenteritis have resulted in an explosion of scientific interest in the genus. Major accomplishments occurring in this field during that interval include a more refined taxonomy, identification of new cell-associated factors (surface layers, pili), and the molecular analysis of selected extracellular gene products that may play a critical role in pathogenesis (hemolysins, enterotoxins). This review provides an updated overview of recent systematic, clinical, and pathophysiologic advances and defines key areas of medical and scientific interest in which major questions remain unanswered.

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Evidence for the direct involvement ofβ-hemolysin inAeromonas hydrophila enteropathogenicity

Cited by 42 publications

References 28 publications

Characterisation of haemolytic activity fromAeromonas caviae

Characterisation of haemolytic activity fromAeromonas caviae

Mannose-resistant adhesion of motileAeromonasto INT407 cells and the differences among isolates from humans, food and water

Recent advances in the study of the taxonomy, pathogenicity, and infectious syndromes associated with the genus Aeromonas

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