scholarly journals Novel cholera toxin variant and ToxT regulon in environmentalVibrio mimicusstrains: potential resources for the evolution ofVibrio choleraehybrid strains

2018 ◽  
Author(s):  
Sucharit Basu Neogi ◽  
Nityananda Chowdhury ◽  
Sharda Prasad Awasthi ◽  
Masahiro Asakura ◽  
Zahid Hayat Mahmud ◽  
...  
Keyword(s):  
Cholera Toxin ◽  
Virulence Factors ◽  
Virulence Genes ◽  
Raw Materials ◽  
New Variant ◽  
Novel Variant ◽  
Ctx Prophage ◽  
El Tor

ABSTRACTAtypical El Tor strains ofVibrio choleraeO1 harboring variantctxBgenes of cholera toxin (CT) are gradually becoming a major cause of recent cholera epidemics.Vibrio mimicusoccasionally contains virulence factors associated with cholera, e.g., CT, encoded byctxABon CTXФ genome; and TCP, the CTXФ-specific receptor. This study carried out extensive molecular characterization of CTXФ and ToxT regulon inctx+vestrains ofV. mimicusisolated from the Bengal coast. Southern hybridization, PCR, and DNA sequencing of virulence related-genes revealed the presence of an El Tor type CTX prophage (CTXET) carrying a novelctxAB, tandem copies of environmental type pre-CTX prophage (pre-CTXEnv), and RS1 elements, which were organized in an array of RS1-CTXET-RS1-pre-CTXEnv-pre-CTXEnv. Additionally, a novel variant oftcpAandtoxTrespectively, showing clonal lineage to a phylogenetic clade ofV. choleraenon-O1/O139, was identified. TheV. mimicusstrains lacked the RTX and TLC elements, andVibrioseventh pandemic islands of the El Tor strains, but contained five heptamer (TTTTGAT) repeats inctxABpromoter region like some classical strains ofV. choleraeO1. PFGE analysis showed all thectx+veV. mimicusstrains were clonally related. However, theirin vitroCT production andin vivotoxigenecity were variable, which could be explained by differential transcription of virulence genes along with ToxR regulon. Taken together, our findings strongly suggest that environmentalV. mimicusstrains act as potential reservoir of atypical virulence factors, including variant CT and ToxT regulon, and may contribute to the evolution ofV. choleraehybrid strains.IMPORTANCENatural diversification of CTXФ andctxABgenes certainly influences disease severity and shifting patterns in major etiological agents of cholera, e.g., the overwhelming emergence of hybrid El Tor variants, replacing the prototype El Tor strains ofV. cholerae. This study showing the occurrence of CTXETcomprising a novel variant ofctxABinV. mimicuspoints out a previously unnoticed evolutionary event, independent to that of the El Tor strains ofV. cholerae. Identification and cluster analysis of the newly-discovered alleles oftcpAandtoxTindicates their horizontal transfer from an uncommon clone ofV. cholerae. The genomic content of ToxT regulon, and tandemly arranged multiple pre-CTXФEnvand a CTXФETinV. mimicusprobably act as salient raw materials inducing natural recombination among the hallmark virulence genes of hybridV. choleraestrains. This study will facilitate deeper understanding of the evolution of new variant CT and ToxT regulon, influencing cholera epidemiology.

scholarly journals Novel Cholera Toxin Variant and ToxT Regulon in EnvironmentalVibrio mimicusIsolates: Potential Resources for the Evolution ofVibrio choleraeHybrid Strains

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Sucharit Basu Neogi ◽  
Nityananda Chowdhury ◽  
Sharda Prasad Awasthi ◽  
Masahiro Asakura ◽  
Kentaro Okuno ◽  
...  
Keyword(s):  
Cholera Toxin ◽  
Virulence Genes ◽  
Raw Materials ◽  
Content Type ◽  
New Variant ◽  
Evolutionary Event ◽  
Ctx Prophage ◽  
El Tor

ABSTRACTAtypical El Tor strains ofVibrio choleraeO1 harboring variantctxBgenes of cholera toxin (CT) have gradually become a major cause of recent cholera epidemics.Vibrio mimicusoccasionally produces CT, encoded byctxABon CTXФ genome; toxin-coregulated pilus (TCP), a major intestinal colonization factor; and also the CTXФ-specific receptor. This study carried out extensive molecular characterization of CTXФ and ToxT regulon inV. mimicusctx-positive (ctx+) strains (i.e.,V. mimicusstrains containingctx) isolated from the Bengal coast. Southern hybridization, PCR, and DNA sequencing of virulence-related genes revealed the presence of an El Tor type CTX prophage (CTXET) carrying a novelctxAB, tandem copies of environmental type pre-CTX prophage (pre-CTXEnv), and RS1 elements, which were organized as an RS1-CTXET-RS1-pre-CTXEnv-pre-CTXEnvarray. Additionally, novel variants oftcpAandtoxT, respectively, showing phylogenetic lineage to a clade ofV. choleraenon-O1 and to a clade ofV. choleraenon-O139, were identified. TheV. mimicusstrains lacked the RTX (repeat in toxin) and TLC (toxin-linked cryptic) elements and lackedVibrioseventh-pandemic islands of the El Tor strains but contained five heptamer (TTTTGAT) repeats inctxABpromoter region similar to those seen with some classical strains ofV. choleraeO1. Pulsed-field gel electrophoresis (PFGE) analysis showed that all thectx+V. mimicusstrains were clonally related. However, theirin vitroCT production andin vivotoxigenicity characteristics were variable, which could be explainable by differential transcription of virulence genes along with the ToxR regulon. Taken together, our findings strongly suggest that environmentalV. mimicusstrains act as a potential reservoir of atypical virulence factors, including variant CT and ToxT regulons, and may contribute to the evolution ofV. choleraehybrid strains.IMPORTANCENatural diversification of CTXФ andctxABgenes certainly influences disease severity and shifting patterns in major etiological agents of cholera, e.g., the overwhelming emergence of hybrid El Tor variants, replacing the prototype El Tor strains ofV. cholerae. This report, showing the occurrence of CTXETcomprising a novel variant ofctxABinV. mimicus, points out a previously unnoticed evolutionary event that is independent of the evolutionary event associated with the El Tor strains ofV. cholerae. Identification and cluster analysis of the newly discovered alleles oftcpAandtoxTsuggest their horizontal transfer from an uncommon clone ofV. cholerae. The genomic contents of ToxT regulon and of tandemly arranged multiple pre-CTXФEnvand of a CTXФETinV. mimicusprobably act as salient raw materials that induce natural recombination among the hallmark virulence genes of hybridV. choleraestrains. This report provides valuable information to enrich our knowledge on the evolution of new variant CT and ToxT regulons.

scholarly journals Expression of Cholera Toxin under Non-AKI Conditions in Vibrio cholerae El Tor Induced by Increasing the Exposed Surface of Cultures

2004 ◽  
Vol 186 (5) ◽  
pp. 1355-1361 ◽  
Author(s):  
Joaquín Sánchez ◽  
Gerardo Medina ◽  
Thomas Buhse ◽  
Jan Holmgren ◽  
Gloria Soberón-Chavez
Keyword(s):  
Cholera Toxin ◽  
Vibrio Cholerae ◽  
Expression Pattern ◽  
Phase 1 ◽  
Inert Atmosphere ◽  
Surface Area Ratio ◽  
Genes Encoding ◽  
El Tor

ABSTRACT The regulatory systems controlling expression of the ctxAB genes encoding cholera toxin (CT) in the classical and El Tor biotypes of pathogenic Vibrio cholerae have been characterized and found to be almost identical. Notwithstanding this, special in vitro conditions, called AKI conditions, are required for El Tor bacteria to produce CT. The AKI conditions involve biphasic cultures. In phase 1 the organism is grown in a still tube for 4 h. In phase 2 the medium is poured into a flask to continue growth with shaking. Virtually no expression of CT occurs if this protocol is not followed. Here we demonstrated that CT expression takes place in single-phase still cultures if the volume-to-surface-area ratio is decreased, both under air and under an inert atmosphere. The expression of key genes involved in the regulation of CT production was analyzed, and we found that the expression pattern closely resembles the in vivo expression pattern.

scholarly journals Virulence Testing of Listeria monocytogenes

2002 ◽  
Vol 85 (2) ◽  
pp. 516-523 ◽  
Author(s):  
Richard B Raybourne
Keyword(s):  
Listeria Monocytogenes ◽  
Virulence Factors ◽  
Animal Studies ◽  
Virulence Genes ◽  
Model Systems ◽  
Host Susceptibility ◽  
Cell Culture Systems ◽  
Small Subpopulation

Abstract A major problem in understanding foodborne listeriosis from both the basic science and regulatory perspectives revolves around the role played by virulence factors of Listeria monocytogenes and how these interact with host susceptibility to result in the observed incidence of disease. From a mechanistic perspective, this problem has been well investigated, and many virulence components of L. monocytogenes have been discovered. Deletion of these genes results in large reductions in virulence functions in vitro and in vivo. The clonal bacteria and genetically identical hosts necessary to solve the riddles associated with virulence mechanisms are not likely to reflect the natural diversity found among wild populations of L. monocytogenes, including those associated with food. These factors contribute to a major dilemma in risk assessment and risk management of foodborne listeriosis: Although low-level L. monocytogenes contamination of certain foods is relatively common, suggesting widespread exposure, illness is overwhelmingly associated with only a relatively small subpopulation (3 of the 13 L. monocytogenes serotypes) and occurs in only a small proportion of susceptible individuals. Virulence testing based on DNA probes for virulence genes is confounded by the widespread distribution of these genes in food isolates. In terms of the distribution of virulence factors among food isolates of L. monocytogenes, only listeriolysin is well characterized, because β-hemolysis is often used to confirm the presence of L. monocytogenes in foods. The presence of other virulence genes such as those involved in host cell invasion and cell-to-cell spread (inIA and actA) among food isolates has not been extensively investigated. How the presence of these components translates into functional virulence as measured in vivo and in vitro is also unknown. Animal studies and cell culture systems show a range of virulence among food isolates of L. monocytogenes. However, clinical isolates included in such studies are not consistently more virulent than food isolates with no known human disease association. Where multiple serotypes or ribotypes are compared, it has been difficult to demonstrate a consistent pattern of increased virulence associated with any subtype(s) in animal or in vitro studies. Development of model systems that adequately reflect the complexity of the host–pathogen relationship remains a challenge.

scholarly journals Expression of virulence factors by classical and El Tor Vibrio cholerae in vivo and in vitro

1990 ◽  
Vol 7 (2-3) ◽  
pp. 221-228 ◽  
Author(s):  
Gunhild Jonson ◽  
Ann-Man Svennerholm ◽  
Jan Holmgren
Keyword(s):  
Vibrio Cholerae ◽  
Virulence Factors ◽  
El Tor

scholarly journals In vitro and in vivo cholera toxin production by classical and El Tor isolates of Vibrio cholerae.

1985 ◽  
Vol 21 (6) ◽  
pp. 884-890 ◽  
Author(s):  
P C Turnbull ◽  
J V Lee ◽  
M D Miliotis ◽  
C S Still ◽  
M Isaäcson ◽  
...  
Keyword(s):  
Cholera Toxin ◽  
Vibrio Cholerae ◽  
Toxin Production ◽  
El Tor

scholarly journals Classical and El Tor Biotypes of Vibrio cholerae Differ in Timing of Transcription of tcpPHduring Growth in Inducing Conditions

2000 ◽  
Vol 68 (5) ◽  
pp. 3010-3014 ◽  
Author(s):  
Yvette M. Murley ◽  
Jaideep Behari ◽  
Robert Griffin ◽  
Stephen B. Calderwood
Keyword(s):  
Cholera Toxin ◽  
Vibrio Cholerae ◽  
Virulence Factors ◽  
Virulence Genes ◽  
Phase Growth ◽  
Classical Strain ◽  
The Absolute ◽  
The Difference ◽  
El Tor ◽  
Transcriptional Fusions

ABSTRACT Two protein pairs in Vibrio cholerae, ToxRS and TcpPH, are necessary for transcription from the toxT promoter and subsequent expression of cholera virulence genes. We have previously shown that transcription of tcpPH in classical strains ofV. cholerae is activated at mid-log-phase growth in ToxR-inducing conditions, while transcription of tcpPH in El Tor strains is not. In this study, we showed that while transcription of tcpPH differs at mid-log-phase growth in ToxR-inducing conditions between the biotypes, transcription is equivalently high during growth in AKI conditions. We usedtcpPH::gusA transcriptional fusions to quantitate expression of tcpPH in each biotype throughout growth in ToxR-inducing conditions and showed that although transcription of tcpPH is reduced at mid-log-phase growth in an El Tor strain, transcription is turned on later in growth to levels in excess of those in the classical strain (although cholera toxin is not produced). This suggests that the difference in expression of cholera virulence factors in response to ToxR-inducing conditions between the El Tor and classical biotypes of V. choleraemay be related to the timing of transcription of tcpPHrather than the absolute levels of transcription.

Vibrio harveyi virulence gene expression in vitro and in vivo during infection in black tiger shrimp Penaeus monodon

2020 ◽  
Vol 139 ◽  
pp. 153-160
Author(s):  
S Peeralil ◽  
TC Joseph ◽  
V Murugadas ◽  
PG Akhilnath ◽  
VN Sreejith ◽  
...  
Keyword(s):  
Gene Expression ◽  
Virulence Genes ◽  
Vibrio Harveyi ◽  
Penaeus Monodon ◽  
Challenge Test ◽  
Virulence Gene ◽  
Economic Losses ◽  
Virulence Gene Expression

Luminescent Vibrio harveyi is common in sea and estuarine waters. It produces several virulence factors and negatively affects larval penaeid shrimp in hatcheries, resulting in severe economic losses to shrimp aquaculture. Although V. harveyi is an important pathogen of shrimp, its pathogenicity mechanisms have yet to be completely elucidated. In the present study, isolates of V. harveyi were isolated and characterized from diseased Penaeus monodon postlarvae from hatcheries in Kerala, India, from September to December 2016. All 23 tested isolates were positive for lipase, phospholipase, caseinase, gelatinase and chitinase activity, and 3 of the isolates (MFB32, MFB71 and MFB68) showed potential for significant biofilm formation. Based on the presence of virulence genes, the isolates of V. harveyi were grouped into 6 genotypes, predominated by vhpA+ flaB+ ser+ vhh1- luxR+ vopD- vcrD+ vscN-. One isolate from each genotype was randomly selected for in vivo virulence experiments, and the LD50 ranged from 1.7 ± 0.5 × 103 to 4.1 ± 0.1 × 105 CFU ml-1. The expression of genes during the infection in postlarvae was high in 2 of the isolates (MFB12 and MFB32), consistent with the result of the challenge test. However, in MFB19, even though all genes tested were present, their expression level was very low and likely contributed to its lack of virulence. Because of the significant variation in gene expression, the presence of virulence genes alone cannot be used as a marker for pathogenicity of V. harveyi.

scholarly journals Attenuation of Aeromonas hydrophila Infection in Carassius auratus by YtnP, a N-acyl Homoserine Lactonase from Bacillus licheniformis T-1

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 631
Author(s):  
Mengfan Peng ◽  
Wentao Tong ◽  
Zhen Zhao ◽  
Ling Xiao ◽  
Zhaoyue Wang ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Bacillus Licheniformis ◽  
Aeromonas Hydrophila ◽  
Biofilm Formation ◽  
Carassius Auratus ◽  
Quorum Quenching ◽  
Inhibition Rate ◽  
Sequence Identity

In this experiment, the quorum quenching gene ytnP of Bacillus licheniformis T-1 was cloned and expressed, and the effect against infection of Aeromonas hydrophila ATCC 7966 was evaluated in vitro and vivo. The BLAST results revealed a 99% sequence identity between the ytnP gene of T-1 and its homolog in B.subtilis sub sp. BSP1, and the dendroGram showed that the similarity in the YtnP protein in T-1 was 100% in comparison with B.subtilis 3610, which was categorized as the Aidc cluster of the MBL family. The AHL lactonase activity of the purified YtnP was detected as 1.097 ± 0.7 U/mL with C6-HSL as the substrate. Otherwise, purified YtnP protein could significantly inhibit the biofilm formation of A.hydrophila ATCC 7966 with an inhibition rate of 68%. The MIC of thiamphenicol and doxycycline hydrochloride against A. hydrophila reduced from 4 μg/mL and 0.5 μg/mL to 1 μg/mL and 0.125 μg/mL, respectively, in the presence of YtnP. In addition, YtnP significantly inhibited the expression of five virulence factors hem, ahyB, ast, ep, aerA of A. hydrophila ATCC 7966 as well (p < 0.05). The results of inhibition on virulence showed a time-dependence tendency, while the strongest anti-virulence effects were within 4–24 h. In vivo, when the YtnP protein was co-injected intraperitoneally with A. hydrophila ATCC 7966, it attenuated the pathogenicity of A. hydrophila and the accumulated mortality was 27 ± 4.14% at 96 h, which was significantly lower than the average mortality of 78 ± 2.57% of the Carassius auratus injected with 108 CFU/mL of A. hydrophila ATCC 7966 only (p < 0.001). In conclusion, the AHL lactonase in B. licheniformis T-1 was proven to be YtnP protein and could be developed into an agent against infection of A. hydrophila in aquaculture.

scholarly journals Antimicrobial Photodynamic Inactivation Inhibits Candida albicans Virulence Factors and ReducesIn VivoPathogenicity

2012 ◽  
Vol 57 (1) ◽  
pp. 445-451 ◽  
Author(s):  
Ilka Tiemy Kato ◽  
Renato Araujo Prates ◽  
Caetano Padial Sabino ◽  
Beth Burgwyn Fuchs ◽  
George P. Tegos ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Virulence Factors ◽  
Sodium Dodecyl ◽  
Systemic Infection ◽  
Tube Formation ◽  
Photodynamic Inactivation ◽  
Content Type ◽  
Daughter Cells

ABSTRACTThe objective of this study was to evaluate whetherCandida albicansexhibits altered pathogenicity characteristics following sublethal antimicrobial photodynamic inactivation (APDI) and if such alterations are maintained in the daughter cells.C. albicanswas exposed to sublethal APDI by using methylene blue (MB) as a photosensitizer (0.05 mM) combined with a GaAlAs diode laser (λ 660 nm, 75 mW/cm2, 9 to 27 J/cm2).In vitro, we evaluated APDI effects onC. albicansgrowth, germ tube formation, sensitivity to oxidative and osmotic stress, cell wall integrity, and fluconazole susceptibility.In vivo, we evaluatedC. albicanspathogenicity with a mouse model of systemic infection. Animal survival was evaluated daily. Sublethal MB-mediated APDI reduced the growth rate and the ability ofC. albicansto form germ tubes compared to untreated cells (P< 0.05). Survival of mice systemically infected withC. albicanspretreated with APDI was significantly increased compared to mice infected with untreated yeast (P< 0.05). APDI increasedC. albicanssensitivity to sodium dodecyl sulfate, caffeine, and hydrogen peroxide. The MIC for fluconazole forC. albicanswas also reduced following sublethal MB-mediated APDI. However, none of those pathogenic parameters was altered in daughter cells ofC. albicanssubmitted to APDI. These data suggest that APDI may inhibit virulence factors and reducein vivopathogenicity ofC. albicans. The absence of alterations in daughter cells indicates that APDI effects are transitory. The MIC reduction for fluconazole following APDI suggests that this antifungal could be combined with APDI to treatC. albicansinfections.

scholarly journals Transcription of Candidate Virulence Genes ofHaemophilus ducreyi during Infection of Human Volunteers

2001 ◽  
Vol 69 (3) ◽  
pp. 1483-1487 ◽  
Author(s):  
Robert E. Throm ◽  
Stanley M. Spinola
Keyword(s):  
Experimental Infection ◽  
Virulence Genes ◽  
Human Model ◽  
Specific Gene ◽  
Gene Products ◽  
Virulence Determinants ◽  
Reverse Transcription Pcr ◽  
Human Volunteers

ABSTRACT Haemophilus ducreyi expresses several putative virulence factors in vitro. Isogenic mutant-to-parent comparisons have been performed in a human model of experimental infection to examine whether specific gene products are involved in pathogenesis. Several mutants (momp, ftpA, losB, lst, cdtC, and hhdB) were as virulent as the parent in the human model, suggesting that their gene products did not play a major role in pustule formation. However, we could not exclude the possibility that the gene of interest was not expressed during the initial stages of infection. Biopsies of pustules obtained from volunteers infected with H. ducreyiwere subjected to reverse transcription-PCR. Transcripts corresponding to momp, ftpA, losB, lst, cdtB, and hhdA were expressed in vivo. In addition, transcripts for other putative virulence determinants such as ompA2, tdhA, lspA1, andlspA2 were detected in the biopsies. These results indicate that although several candidate virulence determinants are expressed during experimental infection, they do not have a major role in the initial stages of pathogenesis.

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