Vibrio cholerae OmpR Contributes to Virulence Repression and Fitness at Alkaline pH.

Vibrio cholerae is a Gram-negative human pathogen and the causative agent of the life-threatening disease cholera. V. cholerae is a natural inhabitant of marine environments and enters humans through the consumption of contaminated food or water. The ability to transition between aquatic ecosystems and the human host is paramount to the pathogenic success of V. cholerae The transition between these two disparate environments requires the expression of adaptive responses, and such responses are most often regulated by two-component regulatory systems such as the EnvZ/OmpR system, which responds to osmolarity and acidic pH in many Gram-negative bacteria. Previous work in our laboratory indicated that V. cholerae OmpR functioned as a virulence regulator through repression of the LysR-family transcriptional regulator aphB; however, the role of OmpR in V. cholerae biology outside virulence regulation remained unknown. In this work, we sought to further investigate the function of OmpR in V. cholerae biology by defining the OmpR regulon through RNA sequencing. This led to the discovery that V. choleraeompR was induced at alkaline pH to repress genes involved in acid tolerance and virulence factor production. In addition, OmpR was required for V. cholerae fitness during growth under alkaline conditions. These findings indicate that V. cholerae OmpR has evolved the ability to respond to novel signals during pathogenesis, which may play a role in the regulation of adaptive responses to aid in the transition between the human gastrointestinal tract and the marine ecosystem.

Vibrio cholerae OmpR Represses the ToxR Regulon in Response to Membrane Intercalating Agents That Are Prevalent in the Human Gastrointestinal Tract.

Multidrug efflux systems belonging to the resistance-nodulation-division (RND) superfamily are ubiquitous in Gram-negative bacteria. RND efflux systems are often associated with multiple antimicrobial resistance and also contribute to the expression of diverse bacterial phenotypes including virulence, as documented in the intestinal pathogen Vibrio cholerae, the causative agent of the severe diarrheal disease cholera. Transcriptomic studies with RND efflux-negative V. cholerae suggested that RND-mediated efflux was required for homeostasis, as loss of RND efflux resulted in the activation of transcriptional regulators, including multiple environmental sensing systems. In this report, we investigated six RND efflux-responsive regulatory genes for contributions to V. cholerae virulence factor production. Our data showed that the V. cholerae gene VC2714, encoding a homolog of Escherichia coli OmpR, was a virulence repressor. The expression of ompR was elevated in an RND-null mutant, and ompR deletion partially restored virulence factor production in the RND-negative background. Virulence inhibitory activity in the RND-negative background resulted from OmpR repression of the key ToxR regulon virulence activator aphB, and ompR overexpression in wild-type cells also repressed virulence through aphB We further show that ompR expression was not altered by changes in osmolarity but instead was induced by membrane-intercalating agents that are prevalent in the host gastrointestinal tract and which are substrates of the V. cholerae RND efflux systems. Our collective results indicate that V. choleraeompR is an aphB repressor and regulates the expression of the ToxR virulence regulon in response to novel environmental cues.

The effect of sampling more cores on the predictive accuracy of pathological grade and tumour distribution in the prostate biopsy.

OBJECTIVE: To determine if increasing the number of cores at biopsy improves the predictive accuracy of the Gleason score or aids in anticipating the location and volume of prostate tumour. PATIENTS AND METHODS: The charts of 75 consecutive patients who underwent radical retropubic prostatectomy for clinical T1-2 adenocarcinoma of the prostate were reviewed retrospectively; 31 patients had a sextant biopsy (group 1) and 44 had > or = 8 cores taken (group 2). The concordance between biopsy data and final prostatectomy Gleason score, tumour location and volume was determined for each group. RESULTS: There were no differences in mean age, prostate-specific antigen level before biopsy or biopsy Gleason score for the two groups; 58% of group 1 had their final pathological grade changed after prostatectomy, vs 29% of group 2 (P < 0.05). In neither group was there a significant correlation between the percentage of cores positive for tumour and the percentage volume of prostate involved with cancer, or the ability of the biopsy to predict tumour location. CONCLUSION: Taking > or = 8 biopsy cores improved the pathological grading accuracy, which may be valuable in choosing a treatment for the patient with newly diagnosed prostate cancer.