Heterogeneity of SOS response expression in clinical isolates of Escherichia coli influences adaptation to antimicrobial stress.

In recent years, new evidence has shown that the SOS response plays an important role in the response to antimicrobials, with involvement in the generation of clinical resistance. Here we evaluate the impact of heterogeneous expression of the SOS response in clinical isolates of Escherichia coli on response to the fluoroquinolone, ciprofloxacin. In silico analysis of whole genome sequencing data showed remarkable sequence conservation of the SOS response regulators, RecA and LexA. Despite the genetic homogeneity, our results revealed a marked differential heterogeneity in SOS response activation, both at population and single-cell level, among clinical isolates of E. coli in the presence of subinhibitory concentrations of ciprofloxacin. Four main stages of SOS response activation were identified and correlated with cell filamentation. Interestingly, there was a correlation between clinical isolates with higher expression of the SOS response and further progression to resistance. This heterogeneity in response to DNA damage repair (mediated by the SOS response) and induced by antimicrobial agents could be a new factor with implications for bacterial evolution and survival contributing to the generation of antimicrobial resistance.

Synergistic Effect of SOS Response and GATC Methylome Suppression on Antibiotic Stress Survival in Escherichia coli.

The suppression of the SOS response has been shown to enhance the in vitro activity of quinolones. Furthermore, Dam-dependent base methylation has an impact on susceptibility to other antimicrobials affecting DNA synthesis. Here, we investigated the interplay between these two processes, alone and in combination, in terms of antimicrobial activity. A genetic strategy was used employing single- and double-gene mutants for the SOS response (recA gene) and the Dam methylation system (dam gene) in isogenic models of Escherichia coli both susceptible and resistant to quinolones. Regarding the bacteriostatic activity of quinolones, a synergistic sensitization effect was observed when the Dam methylation system and the recA gene were suppressed. In terms of growth, after 24 h in the presence of quinolones, the Δdam ΔrecA double mutant showed no growth or delayed growth compared to the control strain. In bactericidal terms, spot tests showed that the Δdam ΔrecA double mutant was more sensitive than the ΔrecA single mutant (about 10- to 102-fold) and the wild type (about 103- to 104-fold) in both susceptible and resistant genetic backgrounds. Differences between the wild type and the Δdam ΔrecA double mutant were confirmed by time-kill assays. The suppression of both systems, in a strain with chromosomal mechanisms of quinolone resistance, prevents the evolution of resistance. This genetic and microbiological approach demonstrated the enhanced sensitization of E. coli to quinolones by dual targeting of the recA (SOS response) and Dam methylation system genes, even in a resistant strain model.

RecA inactivation as a strategy to reverse the heteroresistance phenomenon in clinical isolates of Escherichia coli.

RecA inhibition could be an important strategy to combat antimicrobial resistance because of its key role in the SOS response, DNA repair and homologous recombination contributing to bacterial survival. This study evaluated the impact of RecA inactivation on heteroresistance in clinical isolates of Escherichia coli and their corresponding recA-deficient isogenic strains to multiple classes of antimicrobial agents. A high frequency (>30%) of heteroresistance was observed in this collection of clinical isolates. Deletion of the recA gene led to a marked reduction in heteroresistant subpopulations, especially against quinolones or ß-lactams. The molecular basis of heteroresistance was associated with an increase in copy number of plasmid-borne resistance genes (blaTEM-1B) or tandem gene amplifications (qnrA1). Of note, in the absence of the recA gene, the increase in copy number of resistance genes was suppressed. This makes the recA gene a promising target for combating heteroresistance.

High prevalence of high-risk human papillomavirus infection among women with Trichomonas vaginalis infection on monolayer cytology.

OBJECTIVE: To evaluate the risk of high-risk human papillomavirus (HPV) infection in women with Trichomonas vaginalis infection, and the reason remains unclear. METHODS: A total of 40,000 liquid-based cytology specimens were tested from 2005 to 2008. Among these, high-risk HPV testing using the hybrid capture II assay was performed in positive cases of T. vaginalis according to the age of patients (<30 years old, between 30 and 50 years old, more than 50 years old). As controls, HPV detection was also performed in 450 normal smears. RESULTS: T. vaginalis was found in 80 cases (0.2%). From these 80 cases, 57 were available for HPV testing (8 patients <30 years old, 42 patients between 30 and 50 years old and 7 patients more than 50 years old). As controls, high-risk HPV was tested in 150 patients with normal cytology for each of these three age categories. High-risk HPV was significantly more frequently detected in women with T. vaginalis than in women with normal smear irrespective of the categories of age (P < 0.01). CONCLUSION: For the first time, we demonstrated a significant prevalence of high-risk HPV in women with cytological proved T. vaginalis infection independent of the age ranges. Our data suggest a potential association between these two infectious agents by the way of a sexual intercourse and probably by a biochemical or immunological reasons.

[Contribution of HPV sequences detection in cervical carcinoma screening]. / Intérêt de la recherche des séquences virales HPV dans le dépistage du cancer du col utérin.

At the present time, Human Papillomaviruses (HPV) is a leading cause of squamous intraepithelial lesions (SIL) and invasive carcinoma of the cervix. The aim of this article was to review the main taxonomic and epidemiologic data on HPV infection and to assess the potential clinical implications of the different HPV tests in staging women with borderline cytologies (ASC-US; ASC-H; LSIL); for follow-up after treatment of high-grade cervical intraepithelial neoplasia (CIN), for primary screening as the sole screening modality, or in association with cytology.