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Competition between bacterial species is a major factor shaping microbial communities. It is possible but remains largely unexplored that competition between bacterial pathogens can be mediated through antagonistic effects of bacterial effector proteins on host systems, particularly the actin cytoskeleton. Using Salmonella Typhimurium invasion into cells as a model, we demonstrate that invasion is inhibited if the host actin cytoskeleton is disturbed by actin-specific toxins, namely, Vibrio cholerae MARTX actin crosslinking (ACD) and Rho GTPase inactivation (RID) domains, Photorhabdus luminescens TccC3, and Salmonella's own SpvB. We noticed that ACD, being an effective inhibitor of tandem G-actin-binding assembly factors, is likely to inhibit the activity of another Vibrio effector, VopF. In reconstituted actin polymerization assays and by live-cell microscopy, we confirmed that ACD potently halted the actin nucleation and pointed-end elongation activities of VopF, revealing competition between these two V. cholerae effectors. These results suggest that bacterial effectors from different species that target the same host machinery or proteins may represent an effective but largely overlooked mechanism of indirect bacterial competition in host-associated microbial communities. Whether the proposed inhibition mechanism involves the actin cytoskeleton or other host cell compartments, such inhibition deserves investigation and may contribute to a documented scarcity of human enteric co-infections by different pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Non-01, non-0139 Vibrio cholerae can cause gastroenteritis and extraintestinal infections, but, unlike 01 and 0139 strains of V. cholerae, little is known about the virulence gene content of non-01, non-0139 strains and their phylogenetic relationship to other pathogenic V. cholerae. Comparative genomic microarray analysis of four pathogenic non-01, non-0139 strains indicates that these strains are quite divergent from 01 and 0139 strains. Genomic sequence analysis of a non-01, non-0139 strain (AM19226) that appeared particularly pathogenic in experimental animals suggests that this strain carries a type III secretion system (TTSS) that is related to the TTSS2 gene cluster found in a pandemic clone of Vibrio parahaemolyticus. The genes for this V. cholerae TTSS system appear to be present in many clinical and environmental non-01, non-0139 strains, including at least one clone that is globally distributed. We hypothesize that the TTSS present in some pathogenic strains of non-01, non-0139 V. cholerae may be involved in the virulence and environmental fitness of these strains. genome | virulence | cholera pathogenesis

Background: The distribution of Clostridioides difficile strains and transmission dynamics in the United States are not well defined. Whole-genome sequencing across 2 Centers for Disease Control and Prevention Emerging Infections Program C. difficile infection (CDI) surveillance regions (Minnesota and New York) was performed to identify predominant multilocus sequence types (MLSTs) in community-associated (CA) and healthcare-associated (HCA) disease and assess transmission.Methods: Whole-genome sequencing was performed on C. difficile isolates from patients with CDI over 3 months between 2016 and 2017. Patients were residents of the catchment area without a positive C. difficile test in the preceding 8 weeks. CDI cases were epidemiologically classified as HCA or CA.Results: Of 422 isolates, 212 (50.2%) were HCA and 203 (48.1%) were CA. Predominant MLSTs were sequence type (ST) 42 (9.3%), ST8 (7.8%), and ST2 (8.1%). MLSTs associated with HCA-CDI included ST1 (76%), ST53 (83.3%), and ST43 (80.0%), while those associated with CA-CDI included ST3 (76.9%) and ST41 (77.8%). ST1 was more frequent in New York than in Minnesota (10.8% vs 3.1%). Thirty-three pairs were closely related genomically, 14 of which had potential patient-to-patient transmission supported by record review.Conclusions: The genomic epidemiology of C. difficile across 2 regions of the United States indicates the presence of a diverse strain profile and limited direct transmission. [ABSTRACT FROM AUTHOR]

Cholera is a diarrheal disease that has changed the history of mankind, devastating the world with seven pandemics from 1817 to the present day. Although there is little doubt in the causative agent of these pandemics being Vibrio cholerae of the O1 serogroup, where, when, and how this pathogen emerged is not well understood. V. cholerae is a ubiquitous coastal species that likely existed for tens of thousands of years. However, the evolution of a strain capable of causing a large-scale epidemic is likely more recent historically. Here, we propose that the unique human and physical geography of low-lying river deltas made it possible for an environmental bacterium to evolve into a deadly human pathogen. Such areas are often densely populated and salt intrusion in drinking water frequent. As V. cholerae is most abundant in brackish water, its favored environment, it is likely that coastal inhabitants would regularly ingest the bacterium and release it back in the environment. This creates a continuous selection pressure for V. cholerae to adapt to life in the human gut. [ABSTRACT FROM AUTHOR]

A subset of non-Ol/non-O139 serogroup strains of Vibrio cholerae cause disease using type 3 secretion system (T3SS)-mediated mechanisms. An ~50-kb genomic island carries genes encoding the T3SS structural apparatus, effector proteins, and two trans-membrane transcriptional regulators, VttRA and VttRB, which are ToxR homologues. Previous experiments demonstrated that VttRA and VttRB are necessary for colonization in vivo and promote bile-dependent T3SS gene expression in vitro. To better understand the scope of genes that are potential targets of VttRA and VttRB regulation, we performed deep RNA sequencing using 039 serogroup strain AM-19226 and derivatives carrying deletions in vttRA and vttRB grown in bile. Comparison of the transcript profiles from AvttRA and \vttRB mutant strains to the isogenic parent strain confirmed that VttRA and VttRB regulate expression of some T3SS island genes and provided additional information about relative expression levels and operon organization. Interestingly, the data also suggested that additional genes, located outside the T3SS island and encoding functions involved in motility, chemotaxis, type 6 secretion, transcriptional regulation, and stress responses, may also by regulated by VttRA and VttRB. We verified transcript levels for selected genes by quantitative reverse transcription (RT)-PCR and then focused additional studies on motility and biofilm formation. The results suggest that VttRA and VttRB act as part of a complex transcriptional network that coordinates virulence gene expression with multiple cellular phenotypes. VttRA and VttRB therefore represent horizontally acquired transcriptional regulators with the ability to influence global gene expression in addition to modulating gene expression within the T3SS genomic island. [ABSTRACT FROM AUTHOR]

Cholera outbreaks in subSaharan African countries are caused by strains of the El Tor biotype of toxigenic Vibrio cholerae O1. The El Tor biotype is the causative agent of the current seventh cholera pandemic, whereas the classical biotype, which was associated with the sixth pandemic, is now extinct. Besides other genetic differences the CTX prophages encoding cholera toxin in the two biotypes of V. cholerae O1 have distinct repressor (rstR) genes. However, recent incidences of cholera in Mozambique were caused by an El Tor biotype V. cholerae O1 strain that, unusually, carries a classical type (CTXcalss) prophage. We conducted genomic analysis of the Mozambique strain and its CTX prophage together with chromosomal phage integration sites to understand the origin of this atypical strain and its evolutionary relationship with the true seventh pandemic strain. These analyses showed that the Mozambique strain carries two copies of CTXclass prophage located on the small chromosome in a tandem array that allows excision of the prophage, but the excised phage genome was deficient in replication and did not produce CTXclass virion. Comparative genomic microarray analysis revealed that the strain shares most of its genes with the typical El br strain N16961 but did not carry the TLC gene cluster, and RS1 sequence, adjacent to the CTX prophage. Our data are consistent with the Mozambique strain's having evolved from a progenitor similar to the seventh pandemic strain, involving multiple recombination events and suggest a model for origination of El Tor strains carrying the classical CTX prophage. [ABSTRACT FROM AUTHOR]

Vibrio cholerae is the etiologic bacterial agent of cholera, a severe diarrheal disease endemic in much of the developing world. The V, cholerae genome contains 3,890 genes distributed between a large and a small chromosome. Although the large chromosome encodes the majority of recognizable gene products and virulence determinants, the small chromosome carries a disproportionate number of hypothetical genes. Thus, little is known about the role of the small chromosome in the biology of this organism or other Vibrio species. We have used the rabbit ileal loop model of V. cholerae infection to obtain in vivo-grown cells under near midexponential conditions in the small-intestinal environment. We compared the global transcriptional pattern of these in vivo-grown cells to those grown to midexponential phase in rich medium under aerobic conditions. Under both conditions, the genes showing the highest levels of expression reside primarily on the large chromosome. However, a shift occurs in vivo that results in many more small chromosomal genes being expressed during growth in the intestine. Our analysis further suggests that nutrient limitation (particularly iron) and anaerobiosis are major stresses experienced by V. cholerae during growth in the rabbit upper intestine. Finally, relative to in vitro growth, the intestinal environment significantly enhanced expression of several virulence genes, including those involved in phenotypes such as motility, chemotaxis, intestinal colonization, and toxin production. [ABSTRACT FROM AUTHOR]

Studies quorum-sensing regulators in controlling virulence gene expression in Vibrio cholerae. Observation of defects luxO mutant in colonization of small intestine; Use of gene arrays to profile transcription of V. cholerae; Impact of LuxO in repressing hapR expression.