Pathogenicity Island Virulence Research Articles

Vibrio pathogenicity island and phage CTX genes in Vibrio alginolyticus isolated from different aquatic environments.

In the present study, we investigated the presence of four Vibrio cholerae virulence genes (ctxA, VPI, Zot and ace) in 36 Vibrio alginolyticus isolates obtained from different seawater, sediments and aquatic organisms. We tested the virulence of 13 V. alginolyticus strains against juveniles of Sparus aurata and this virulence was correlated with the presence of V. cholerae virulence genes. A positive amplification for the virulence pathogenicity island was produced by five V. alginolyticus strains and four for cholerae toxin. Some of the V. alginolyticus strains are pathogenic to aquatic animals and might have derived their virulence genes from V. cholerae. V. alginolyticus strains can be considered as a possible reservoir of V. cholerae virulence genes.

Effect of Ultraviolet-C (UV-C) irradiation on the virulence genes expression in Vibrio parahaemolyticus and Vibrio alginolyticus

-2 ) to evaluate alterations in their virulence genes expression levels. Firstly, we searched for the presence of eight Vibrio cholerae virulence genes, toxR, toxS, toxRS, ctxA, zot, ace, toxT, and virulence pathogenicity island (VPI), in the genome of investigated strains. The expression of toxR and toxS genes in UVC-irradiated bacteria, studied by reverse transcriptase polymerase chain reaction, was found to be altered. These variations were manifested by an increase or a decrease in the expression level of tested virulence genes. Further, the mRNA quantities of VPI and ace genes remained stable after treatment.

Expression of hilA in Response to Mild Acid Stress in Salmonella enterica is Serovar and Strain Dependent

Salmonella enterica is the leading cause of foodborne illness with poultry and poultry products being primary sources of infection. The 2 most common S. enterica serovars associated with human infection are Typhimurium and Enteritidis. However, Kentucky and Heidelburg and the 2 most prevalent serovars isolated from poultry environments. Given the prevalence of other serovars in poultry products and environments, research is needed to understand virulence modulation in response to stress in serovars other than Typhimurium and Enteritidis. Thus, the objective of this research was to compare hilA gene expression (a master regulator of the virulence pathogenicity island) in response to acid stress among different strains and serovars of Salmonella. A total of 11 serovars consisting of 15 strains of S. enterica were utilized for these experiments. Cultures were suspended in tryptic soy broth (TSB) adjusted to pH 7.2, 6.2, or 5.5 with HCl or acetic acid. Total RNA was extracted from cultures at specific time points (0, 2, 4, and 24 h). Gene expression of hilA was measured with quantitative reverse transcriptase real time PCR (qRT-PCR). Growth and pH were measured throughout the 24 h time frame. Regulation of hilA in response to acid stress varied by serovar and strain and type of acid. The results of these experiments indicate that hilA regulation may have some impact on virulence and colonization of S. enterica. However, these results warrant further research to more fully understand the significance of hilA regulation in response to mild acid stress in S. enterica.

English

  In this study, we incubated Vibrio parahaemolyticus and Vibrio alginolyticus (marine food-borne pathogens bacteria) in seawater for 8 months to study their morphologic, proteomic and genetic responses to starvation. The atomic force micrographs of stressed strains showed a reduction of the cells size and an evolution to two coccoid-shape forms whose length is less than 0.4 μm and between 0.5 and 1 μm. Extracellular protein patterns and gelatinase profiles of stressed bacteria were also altered. Indeed, these modifications were manifested by the appearance and/or disappearance of bands as well as in the level of expression of certain proteins. In addition, we also searched for the presence of eight Vibrio cholerae virulence genes: toxR, toxS, toxRS, ctxA, zot,ace, toxT, and Virulence Pathogenicity Island (VPI) in the genome of investigated strains. The expression level of VPI gene studied by reverse transcriptase polymerase chain reaction was decreased, whereas the mRNA quantities of toxR, toxS, and ace in starved Vibrio remained stable.   Key words: Vibrio, seawater, alterations, morphology, proteins secreted, virulence gene expression, RT-PCR

Alterations of Outer Membrane Proteins and Virulence Genes Expression in Gamma-IrradiatedVibrio parahaemolyticusandVibrio alginolyticus

Gamma-irradiation technology sterilizes microorganisms and thereby prevents decay and improves the safety and shelf stability of food products. In this study we treated the foodborne pathogens Vibrio parahaemolyticus and Vibrio alginolyticus with gamma-irradiation (0.5 kGy) to evaluate their adaptative response. Outer membrane protein patterns of irradiated bacteria were found altered when analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. These modifications were manifested by the appearance and/or disappearance of bands as well as in the expression level of certain proteins. In addition, we searched for the presence of eight Vibrio cholerae virulence genes, toxR, toxS, toxRS, ctxA, zot, ace, toxT, and virulence pathogenicity island (VPI), in the genome of investigated strains. The expression of toxR, toxS, VPI, and ace genes in gamma-irradiated bacteria, studied by reverse transcriptase polymerase chain reaction, was altered. These variations were manifested by an increase and/or a decrease in the expression level of tested virulence genes.

Investigation of several virulence properties among Vibrio alginolyticus strains isolated from diseased cultured fish in Tunisia

We analysed 34 Vibrio alginolyticus strains isolated from gilthead sea bream Sparus aurata L. and sea bass Dicentrarchus labrax L. cultured in fish farms on the Tunisian Mediterranean coast for the presence of several virulence properties such as extracellular products (ECP) production, growth in iron-limiting conditions and survival in fish serum. The results obtained with different substrates showed that ECP of V. alginolyticus were hydrolytic. The virulence was correlated with the ability of strains to grow in the presence of non-immune fish serum or under conditions of iron limitation. We further examined the presence of virulence genes homologous to those in V. cholerae (toxR, toxS, VPI and ace); toxR was found in 16 V. alginolyticus strains and toxS in 17 strains out of 34 analysed. A positive amplification for the virulence pathogenicity island (VPI) was produced by 12 V alginolyticus strains. Finally, the ace expected amplification fragment was found in 7 V. alginolyticus isolates. Thus, the pathogenicity of V. alginolyticus may be the result of a combination of all these factors.

RT-PCR assays for in vivo expression ofVibrio alginolyticus virulence genes in cultured giltheadDicentrarchus labrax andSparus aurata

In this study, we investigated the pathogenic potency of twoVibrio alginolyticus strains isolated from cultured giltheadDicentrarchus labrax andSparus aurata, in Tunisia. The enzymatic activities of the extracellular products of the studied strains characterized with the API-ZYM system, revealed the existence of several activities. The 50% lethal doses levels were then determined, virulence levels ranged from 1.03×105 to 1.0×106 CFU/fish. In addition, we also searched for the presence of eightVibrio cholerae virulence genes:ctxA, zot, ace, toxR, toxS, toxRS, toxT, and Virulence Pathogenicity Island (VPI), in the genome of two isolated strains ofV. alginolitycus. Thein vivo expression oftoxR, toxS, VPI andace genes in both fish species, was tested by reverse transcriptase polymerase chain reaction. Indeed, we have noted that for each strain all the virulence genes selected were expressed in sea bream as well as in sea bass.