Bacterial vaginosis (BV) candidate bacteria: associations with BV and behavioural practices in sexually-experienced and inexperienced women

Background

In recent years several new fastidious bacteria have been identified that display a high specificity for BV; however no previous studies have comprehensively assessed the behavioural risk associations of these bacterial vaginosis-candidate organisms (BV-COs).

Methods

We examined the associations between 8 key previously described BV-COs and BV status established by Nugent''s score (NS). We also examined the sexual practices associated with each BV-CO. We incorporated 2 study populations: 193 from a sexually-inexperienced university population and 146 from a highly sexually-active clinic population. Detailed behavioural data was collected by questionnaire and vaginal smears were scored by the Nugent method. Stored samples were tested by quantitative PCR assays for the 8 BV-COs: Atopobium vaginae, Gardnerella vaginalis, Leptotrichia spp., Megasphaera type I, Sneathia spp., and the Clostridia-like bacteria BVAB1, BVAB2 and BVAB3. Associations between BV-COs and BV and behaviours were examined by univariate and multivariable analyses.

Results

On univariate analysis, all BV-COs were more common in BV compared to normal flora. However, only Megasphaera type I, BVAB2, A. vaginae and G. vaginalis were significantly independently associated with BV by multivariable analysis. Six of the eight BV-COs (Megasphaera type I, BVAB2, BVAB3, Sneathia, Leptotrichia and G. vaginalis) were rare or absent in sexually-unexposed women, and demonstrated increasing odds of detection with increasing levels of sexual activity and/or numbers of lifetime sexual partners. Only G. vaginalis and A. vaginae were commonly detected in sexually-unexposed women. Megasphaera type I was independently associated with women-who-have-sex-with women (WSW) and lifetime sexual partner numbers, while unprotected penile-vaginal-sex was associated with BVAB2 detection by multivariate analysis.

Conclusions

Four of eight key BV-COs were significantly associated with BV after adjusting for the presence of other BV-COs. The majority of BV-COs were absent or rare in sexually-unexposed women, and associated with increasing sexual exposure, suggesting potential sexual transmission of BV-COs.     

Identification and characterization of protein phosphatase 2C activation by ceramide

Ceramide is a bioactive sphingolipid with many associated biological outcomes, yet there is a significant gap in our current understanding of how ceramide mediates these processes. Previously, ceramide has been shown to activate protein phosphatase (PP) 1 and 2A. While continuing this line of work, a late fraction from a Mono-Q column was consistently observed to be activated by ceramide, yet PP1 and PP2A were undetectable in this fraction. Proteomic analysis of this fraction revealed the identity of the phosphatase to be PP2Cγ/PPM1G. This was consistent with our findings that PP2Cγ 1-eluted in a high salt fraction due to its strongly acidic domain, and 2-was insensitive to okadaic acid. Further characterization was performed with PP2Cα, which showed robust activation by C(6)-ceramide. Activation was specific for the erythro conformation of ceramide and the presence of the acyl chain and hydroxyl group at the first carbon. In order to demonstrate more physiological activation of PP2Cα by ceramide, phospho-p38δ was utilized as substrate. Indeed, PP2Cα induced the dephosphorylation of p38δ only in the presence of C(16)-ceramide. Taken together, these results show that the PP2C family of phosphatases is activated by ceramide, which may have important consequences in mediating the biological effects of ceramide.     

Evaluation of Clinical and Immunological Markers for Predicting Virological Failure in a HIV/AIDS Treatment Cohort in Busia,Kenya

Background

In resource-limited settings where viral load (VL) monitoring is scarce or unavailable, clinicians must use immunological and clinical criteria to define HIV virological treatment failure. This study examined the performance of World Health Organization (WHO) clinical and immunological failure criteria in predicting virological failure in HIV patients receiving antiretroviral therapy (ART).

Methods

In a HIV/AIDS program in Busia District Hospital, Kenya, a retrospective, cross-sectional cohort analysis was performed in April 2008 for all adult patients (>18 years old) on ART for ≥12 months, treatment-naive at ART start, attending the clinic at least once in last 6 months, and who had given informed consent. Treatment failure was assessed per WHO clinical (disease stage 3 or 4) and immunological (CD4 cell count) criteria, and compared with virological failure (VL >5,000 copies/mL).

Results

Of 926 patients, 123 (13.3%) had clinically defined treatment failure, 53 (5.7%) immunologically defined failure, and 55 (6.0%) virological failure. Sensitivity, specificity, positive predictive value, and negative predictive value of both clinical and immunological criteria (combined) in predicting virological failure were 36.4%, 83.5%, 12.3%, and 95.4%, respectively.

Conclusions

In this analysis, clinical and immunological criteria were found to perform relatively poorly in predicting virological failure of ART. VL monitoring and new algorithms for assessing clinical or immunological treatment failure, as well as improved adherence strategies, are required in ART programs in resource-limited settings.     

Specific limited cleavage of bihelical deoxyribonucleic acid by wheat seedling nuclease.

Wheat seedling nuclease catalyzes the hydrolysis of intact, bihelical viral DNA or high molecular weight, native Escherichia coli DNA to produce limit polymers which are resistant to further hydrolysis by additional enzyme. These limit products are double-stranded polymers free of single strand interruptions and are terminated at their 5' ends with equal amounts of either deoxycytidylate or deoxyguanylate residues. The average size of the duplex limit products, as determined by (a) alkaline and neutral sucrose gradient sedimentation, (b) viscometric determination of molecular weight, and (c) 5'-end labeling, varies from 2 to 4 times 10-6 depending on the source of the DNA. The involvement of regions rich in adenine-thymine base pairs at the sites of cleavage of the DNA molecule is suggested by the following experimental results: (a) the copolymeric duplex, poly(dA-dt) is hydrolyzed at a rate comparable to that found for denatured calf thymus DNA, a rate which is several orders of magnitude faster than that at which native calf thymus DNA is hydrolyzed; (b) lambda DNA, which contains an adenine-thymine-rich region near its center, is rapidly cleaved to yield two fragments of similar size; (c) the rate of hydrolysis of native DNA is increased approximately 14-fold by increasing the reaction temperature from 20 degrees to 30 degrees.     

Sleeping with the ‘enemy’: hybridization of an endangered tree weta

While hybridization is an important part of the evolutionary process, for rare species mating with more common species hybridization can increase the risks of extinction. By mating with heterospecifics rare species waste valuable reproductive resources and as a result population sizes may decline. If introgression occurs, the rare species can become genetically swamped by alleles from the more common species, rendering it effectively extinct. As a consequence of these risks, hybridization with the more common species Hemideina femorata (Canterbury tree weta) may lead to the extinction of the range restricted species H. ricta (Banks Peninsula tree weta) on Banks Peninsula. The current study uses spatial interpolation to model the distribution of each species and the potential sympatric zone to guide sampling efforts. Polymorphic microsatellite markers and mitochondrial sequence data were used to determine the extent of hybridization between H. ricta and H. femorata. The results confirm that hybridization is possible between these species. However, hybrids and introgression appear to be very rare, suggesting that reproductive isolating barriers are present but incomplete. The threat of extinction to H. ricta via hybridization with H. femorata is low but extreme loss of habitat may cause changes to population densities that could increase the risks of hybridization. Therefore, landowners should be encouraged to conserve native bush.