Host Immune Responses to Aeromonas Virulence Factors

Galindo, Cristi L.; Sha, Jian; Fadl, Amin A.; Pillai, Lakshmi; Chopra, Ashok K.

doi:10.2174/157339506775471910

Cited by 65 publications

(67 citation statements)

References 162 publications

(180 reference statements)

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“…The motility of A. hydrophila is an important factor for bacteria to reach the host target tissue, to colonize, and then to cause disease (22). We noted that the vacB A. hydrophila mutant strain had 57% less motility (Fig.…”

Section: Resultsmentioning

confidence: 86%

Cold Shock Exoribonuclease R (VacB) Is Involved in Aeromonas hydrophila Pathogenesis

Erova¹,

Kosykh

Fadl³

et al. 2008

J Bacteriol

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In this study, we cloned and sequenced a virulence-associated gene (vacB) from a clinical isolate SSU of Aeromonas hydrophila. We identified this gene based on our recently annotated genome sequence of the environmental isolate ATCC 7966 T of A. hydrophila and the vacB gene of Shigella flexneri. The A. hydrophila VacB protein contained 798 amino acid residues, had a molecular mass of 90.5 kDa, and exhibited an exoribonuclease (RNase R) activity. The RNase R of A. hydrophila was a cold-shock protein and was required for bacterial growth at low temperature. The vacB isogenic mutant, which we developed by homologous recombination using marker exchange mutagenesis, was unable to grow at 4°C. In contrast, the wild-type (WT) A. hydrophila exhibited significant growth at this low temperature. Importantly, the vacB mutant was not defective in growth at 37°C. The vacB mutant also exhibited reduced motility, and these growth and motility phenotype defects were restored after complementation of the vacB mutant. The A. hydrophila RNase R-lacking strain was found to be less virulent in a mouse lethality model (70% survival) when given by the intraperitoneal route at as two 50% lethal doses (LD 50 ). On the other hand, the WT and complemented strains of A. hydrophila caused 80 to 90% of the mice to succumb to infection at the same LD 50 dose. Overall, this is the first report demonstrating the role of RNase R in modulating the expression of A. hydrophila virulence.A human diarrheal isolate SSU of Aeromonas hydrophila possesses various pathogenic mechanisms that contribute to the overall virulence of this bacterium in the host. Most importantly, our laboratory has described type II, type III, and type VI secretion system effector proteins that are involved in the disease state (gastroenteritis or septicemia) in animal models (11,15,17,21,32,(44)(45)(46)48). However, to better understand the full virulence potential of any pathogen, it is important to identify new pathogenic factors and/or mechanisms that could be involved in their virulence. This is crucial since the expression of different virulence genes could be contributing factors leading to disease depending upon the anatomical niche where the organisms colonize and the environment in those regions which dictates the differential expression of genes (18).Studies by Tobe et al. (50) identified a novel chromosomal gene, vacB, which was required for the production of S. flexneri virulence factors (e.g., IpaB, IpaC, IpaD, and VirG) from the large plasmid (230 kb) of this microorganism. More recently, it was shown that the vacB gene in S. flexneri and Escherichia coli strains encoded the 3Ј-5Ј exoribonuclease RNase R (10). The deduced size of VacB (virulence-associated) protein is approximately 92 kDa, and it is located at 95 min on the E. coli chromosome, a position consistent with the earlier mapping studies of the gene encoding RNase R (10). These investigators provided evidence that RNase R has an essential cell function, in addition to its role in bacterial virulence, an...

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Section: Resultsmentioning

confidence: 86%

Cold Shock Exoribonuclease R (VacB) Is Involved in Aeromonas hydrophila Pathogenesis

Erova¹,

Kosykh

Fadl³

et al. 2008

J Bacteriol

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“…In fact, formation o biofilm allows this pathogen to resist chlorination of treated waters as well as numerous antimicrobial agents (Palú et al, 2006). The majority of Aeromonas infections manifest themselves as self-limiting gastroenteritis; however, in some instances (particularly in the young, elderly and other immunocompromised individuals), disease can range from superficial skin sequelae to more systemic infections including: cellulitis, bacteraemia, peritonitis and haemolytic-uraemic syndrome (Brouqui & Raoult, 2001;Chopra et al, 1993;Chopra et al, 1996;Chopra & Houston, 1999;Galindo et al, 2006;Janda et al, 1994;Kühn et al, 1997;Merino et al, 1995). However, not all infections occur in immunocompromised individuals.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the roles played by Hcp and VgrG type 6 secretion system effectors in Aeromonas hydrophila SSU pathogenesis

et al. 2013

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Aeromonas hydrophila, a Gram-negative bacterium, is an emerging human pathogen equipped with both a type 3 and a type 6 secretion system (T6SS). In this study, we evaluated the roles played by paralogous T6SS effector proteins, hemolysin co-regulated proteins (Hcp-1 and -2) and valine glycine repeat G (VgrG-1, -2 and -3) protein family members in A. hydrophila SSU pathogenesis by generating various combinations of deletion mutants of the their genes. In addition to their predicted roles as structural components and effector proteins of the T6SS, our data clearly demonstrated that paralogues of Hcp and VgrG also influenced bacterial motility, protease production and biofilm formation. Surprisingly, there was limited to no observed functional redundancy among and/or between the aforementioned T6SS effector paralogues in multiple assays. Our data indicated that Hcp and VgrG paralogues located within the T6SS cluster were more involved in forming T6SS structures, while the primary roles of Hcp-1 and VgrG-1, located outside of the T6SS cluster, were as T6SS effectors. In terms of influence on bacterial physiology, Hcp-1, but not Hcp-2, influenced bacterial motility and protease production, and in its absence, increases in both of the aforementioned activities were observed. Likewise, VgrG-1 played a major role in regulating bacterial protease production, while VgrG-2 and VgrG-3 were critical in regulating bacterial motility and biofilm formation. In an intraperitoneal murine model of infection, all Hcp and VgrG paralogues were required for optimal bacterial virulence and dissemination to mouse peripheral organs. Importantly, the observed phenotypic alterations of the T6SS mutants could be fully complemented. Taking these results together, we have further established the roles played by the two known T6SS effectors of A. hydrophila by defining their contributions to T6SS function and virulence in both in vitro and in vivo models of infection.

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“…This toxin is closely related to aerolysin (AerA), a channel-forming toxin identified 34 years ago (Bernheimer and Avigad, 1974) and encoded by a gene named aerA. The Act and AerA toxins have haemolytic, cytotoxic and enterotoxic activities, as well as lethality in mice (Galindo et al, 2006). Thus, to overcome this problem, a complex primer of act/hlyA/aer was chosen that amplifies these three virulence factors as a complex gene (Balsalobre et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

Prevalence of Hemolytic and Enterotoxigenic Aeromonas Spp. in Healthy and Diseased Freshwater Food Fishes as Assessed by Multiplex PCR

Hussain¹,

Jeyasekaran²,

Shakila³

et al. 2013

AJAFST

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A total of 103 representative colonies from 53 healthy and diseased food fish samples were tested for the incidence of Aeromonas spp. Of which 57% of colonies were positive for Aeromonas spp. by the multiplex PCR (MPCR). On an average, the prevalence was found to be 66% with highest incidence in diseased fishes (76%). About 48% of healthy fish samples were observed to contain Aeromonas. The biomoleculoar identification revealed that the selected virulent hemolytic and enterotoxigenic genes appeared in four different patterns viz. alt; act//hlyA/aer; alt and act//hlyA/aer; ast, alt and act//hlyA/aer, among the MPCR positive isolates of Aeromonas spp. The overall prevalence of the toxin genes alt, act/hlyA/aer and ast among the MPCR positive Aeromonas isolates was found to be 89.8%, 72.9% and 20%, respectively. The biochemical confirmation of the MPCR positive Aeromonas isolates revealed different species in the tested samples belonging to A. hydrophila, A. sobria, A. caviae, A. jandaei, A. veronii, A. schubertii and A. trota and the dominant species was found to be A. hydrophila (48%).

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Host Immune Responses to Aeromonas Virulence Factors

Cited by 65 publications

References 162 publications

Cold Shock Exoribonuclease R (VacB) Is Involved in Aeromonas hydrophila Pathogenesis

Cold Shock Exoribonuclease R (VacB) Is Involved in Aeromonas hydrophila Pathogenesis

Evaluation of the roles played by Hcp and VgrG type 6 secretion system effectors in Aeromonas hydrophila SSU pathogenesis

Prevalence of Hemolytic and Enterotoxigenic Aeromonas Spp. in Healthy and Diseased Freshwater Food Fishes as Assessed by Multiplex PCR

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