Molecular Epidemiology of HIV-1 Transmission in a Cohort of HIV-1 Concordant Heterosexual Couples from Dakar, Senegal

BACKGROUND: A large number of HIV-1 infections in Africa occur in married couples. The predominant direction of intracouple transmission and the principal external origins of infection remain important issues of debate. METHODS: We investigated HIV-1 transmission in 46 HIV-1 concordant positive couples from Dakar, Senegal. Intracouple transmission was confirmed by maximum-likelihood phylogenetic analysis and pairwise distance comparisons of HIV-1 env gp41 sequences from both partners. Standardized interview data were used to deduce the direction as well as the external sources of the intracouple transmissions. RESULTS: Conservative molecular analyses showed linked viruses in 34 (74%) couples, unlinked viruses in 6 (13%) couples, and indeterminate results for 6 (13%) couples. The interview data corresponded completely with the molecular analyses: all linked couples reported internal transmission and all unlinked couples reported external sources of infection. The majority of linked couples (93%) reported the husband as internal source of infection. These husbands most frequently (82%) reported an occasional sexual relationship as external source of infection. Pairwise comparisons of the CD4 count, antiretroviral therapy status, and the proportion of gp41 ambiguous base pairs within transmission pairs correlated with the reported order of infection events. CONCLUSIONS: In this suburban Senegalese population, a majority of HIV-1 concordant couples showed linked HIV-1 transmission with the husband as likely index partner. Our data emphasize the risk of married women for acquiring HIV-1 as a result of the occasional sexual relationships of their husbands

Evaluation of Molecular Assays for Rapid Detection of Methicillin-Resistant Staphylococcus aureus ▿ †

The diagnostic sensitivities of the BD GeneOhm and Cepheid Xpert assays were compared using culture on log-serial dilutions of well-characterized methicillin-resistant Staphylococcus aureus (MRSA) and non-MRSA strains and on nasal and groin swabs from patients with histories of MRSA carriage. The sensitivities of GeneOhm and Xpert were high at 103-CFU/ml MRSA concentrations (92.3% and 96.3%, respectively) although decreased considerably (<35%) at a 1-log-lower concentration. Unexpectedly, both assays also detected select coagulase-negative staphylococci, which requires further evaluation

Comparison of Biofilm Formation between Major Clonal Lineages of Methicillin Resistant <i>Staphylococcus aureus</i>

<div><p>Objectives</p><p>Epidemic methicillin-resistant <i>S. aureus</i> (MRSA) clones cause infections in both hospital and community settings. As a biofilm phenotype further facilitates evasion of the host immune system and antibiotics, we compared the biofilm-forming capacities of various MRSA clones.</p><p>Methods</p><p>Seventy-six MRSA classified into 13 clones (USA300, EMRSA-15, Hungarian/Brazilian etc.), and isolated from infections or from carriers were studied for biofilm formation under static and dynamic conditions. Static biofilms in microtitre plates were quantified colorimetrically. Dynamic biofilms (Bioflux 200, Fluxion, USA) were studied by confocal laser-scanning and time-lapse microscopy, and the total volume occupied by live/dead bacteria quantified by Volocity 5.4.1 (Improvision, UK).</p><p>Results</p><p>MRSA harbouring SCC<i>mec</i> IV produced significantly more biomass under static conditions than SCC<i>mec</i> I–III (P = 0.003), and those harbouring SCC<i>mec</i> II significantly less than those harbouring SCC<i>mec</i> I or III (P<0.001). In the dynamic model, SCC<i>mec</i> I–III harbouring MRSA were significantly better biofilm formers than SCC<i>mec</i> IV (P = 0.036). Only 16 strains successfully formed biofilms under both conditions, of which 13 harboured SCC<i>mec</i> IV and included all tested USA300 strains (n = 3). However, USA300 demonstrated remarkably lower percentages of cell-occupied space (6.6%) compared to the other clones (EMRSA-15 = 19.0%) under dynamic conditions. Time-lapse microscopy of dynamic biofilms demonstrated that USA300 formed long viscoelastic tethers that stretched far from the point of attachment, while EMRSA-15 consisted of micro-colonies attached densely to the surface.</p><p>Conclusions</p><p>MRSA harbouring SCC<i>mec</i> types IV and I–III demonstrate distinct biofilm forming capacities, possibly owing to their adaptation to the community and hospital settings, respectively. USA300 demonstrated abundant biofilm formation under both conditions, which probably confers a competitive advantage, contributing to its remarkable success as a pathogen.</p></div

Demographic, behavioural and clinical information of 49 HIV-1 concordant couples included in the study.

<p>Data are median (interquartile range) values or n (%) when indicated.</p>a<p>n = 49 for variables for which husbands in 4 polygamous partnerships were asked to report separately for each wife.</p>b<p>Other nationalities were Mali, Mauretania, Guinea or Guinea-Bissau.</p>c<p>Region<200 km from Dakar.</p>d<p>Other ethnicities were Bambara or Diola.</p>e<p>At least one year of education in the specified grade.</p>f<p>Mann-Whitney U test was used to compare independent continuous data.</p>g<p>Chi-square or Fisher's exact test was used to compare independent proportional data.</p>h<p>Wilcoxon signed rank test was used to compare paired continuous data.</p>i<p>McNemar test was used to compare paired proportional data.</p

Comparison of epidemiological and molecular analyses of HIV-1 transmission for 41 HIV-1 concordant couples.

<p>Data are cross-tabulated numbers of subjects.</p

Live/dead BacLight staining and CLSM on 72-hour old MRSA biofilms under shear flow (Bioflux system).

<p>A) 3-dimensional representations. B) 2-dimensional projections, thin white lines in the xy plane depict the location of the section plane on the z axis. White bars have a length of 10 µm.</p

Box-whisker plot of biofilm formation by MRSA clones in the static assay.

<p>Boxes depict the 95% CI, black horizontal lines the average OD492 value, and the whiskers the OD492 value range (lowest and highest values) for each clone.</p

Performance of MRSA clones in the static and shear flow assay.

<p>A) In the static assay: biomass production was subdivided into weak, moderate and strong. B) In the shear flow assay biofilm formation was assessed as positive or negative.</p

Space occupied by live (green) or dead (red) or total (grey) cells by different epidemic MRSA clones in a biofilm.

<p>Error bars denote standard deviations were calculated using 1 (USA300, EMRSA-15), 2 (USA600, Hungarian/Brazilian, Iberian) or 3 (USA500) independent z-stacks.</p

Overview of MRSA clone characteristics, site of isolation, and biofilm formation in static and shear flow assays.

<p>Overview of MRSA clone characteristics, site of isolation, and biofilm formation in static and shear flow assays.</p