The rhizosphere of the halophytic grass Sporobolus robustus Kunth hosts rhizobium genospecies that are efficient on Prosopis juliflora (Sw.) DC and Vachellia seyal (Del.) P.J.H. Hurter seedlings.

The aim of this study was to survey the abundance and genetic diversity of legume-nodulating rhizobia (LNR) in the rhizosphere of a salt-tolerant grass, Sporobolus robustus Kunth, in the dry and rainy seasons along a salinity gradient, and to test their effectiveness on Prosopis juliflora (SW.) DC and Vachellia seyal (Del.) P.J.H. Hurter seedlings. The results showed a significant decrease in LNR population density and diversity in response to salinity, particularly during the dry season. A phylogenetic analysis of the 16S-23S rRNA ITS region clustered the 232 rhizobium isolates into three genera and 12 distinct representative genotypes: Mesorhizobium (8 genotypes), Ensifer (2 genotypes) and Rhizobium (2 genotypes). Of these genotypes, 2 were only found in the dry season, 4 exclusively in the rainy season and 6 were found in both seasons. Isolates of the Mesorhizobium and Ensifer genera were more abundant than those of Rhizobium, with 55%, 44% and 1% of the total strains, respectively. The abundance of the Mesorhizobium isolates appeared to increase in the dry season, suggesting that they were more adapted to environmental aridity than Ensifer genospecies. Conversely, Ensifer genospecies were more tolerant of high salinity levels than the other genospecies. However, Ensifer genospeciesproved to be the most efficient strains on P. juliflora and V. seyal seedlings. We concluded that S. robustus hosts efficient rhizobium strains in its rhizosphere, suggesting its ability to act as a nurse plant to facilitate seedling recruitment of P. juliflora and V. seyal in saline soils.

HIV and the dual burden of malnutrition in Senegal, 1994-2012.

The aims of this study were to determine the nutritional status of HIV-positive versus HIV-negative adults in Senegal and to identify predictors of nutritional status among people living with HIV (PLHIV). We conducted a retrospective study using data from individuals enrolled in previous studies in Senegal. Undernutrition was defined as body mass index (BMI) <18.5 and overnutrition was defined as BMI ≥25.0. Subcategories of overnutrition were overweight (defined as BMI 25.0-29.9) and obesity (BMI ≥30.0). Predictors of nutritional status were identified using multinomial logistic regression. Data from 2448 adults were included; 1471 (60%) were HIV positive. Among HIV-negative individuals, the prevalence of undernutrition decreased from 23% in 1994-1999 to 5% in 2006-2012, while the prevalence of overnutrition increased from 19 to 55%. Among PLHIV, undernutrition decreased from 52 to 37% and overnutrition increased from 10 to 15%. Women had greater odds of obesity (odds ratio [OR] 11.4; p < 0.01). Among HIV-positive women, undernutrition was associated with WHO stage 3 or 4 and CD4 cell count <200; antiretroviral therapy (ART) and education were protective. Obesity was associated with age > 35 years, commercial sex work, and alcohol use. Among HIV-positive men, WHO stage 3 or 4 and CD4 cell count <200 were predictive of undernutrition; ART was protective. Our study highlights the need for the integration of nutrition interventions into HIV programs in Senegal and suggests that for nutrition programs to be most effective, strategies may need to differ when targeting men versus women. Furthermore, improving access to education and focusing on women for nutrition interventions could be of particularly high impact at the household level.

Pearl Millet Genetic Traits Shape Rhizobacterial Diversity and Modulate Rhizosphere Aggregation.

Root exudation contributes to soil carbon allocation and also to microbial C and energy supply, which subsequently impacts soil aggregation around roots. Biologically-driven soil structural formation is an important driver of soil fertility. Plant genetic determinants of exudation and more generally of factors promoting rhizosphere soil aggregation are largely unknown. Here, we characterized rhizosphere aggregation in a panel of 86 pearl millet inbred lines using a ratio of root-adhering soil dry mass per root tissue dry mass (RAS/RT). This ratio showed significant variations between lines, with a roughly 2-fold amplitude between lowest and highest average values. For 9 lines with contrasting aggregation properties, we then compared the bacterial diversity and composition in root-adhering soil. Bacterial α-diversity metrics increased with the "RAS/RT ratio." Regarding taxonomic composition, the Rhizobiales were stimulated in lines showing high aggregation level whereas Bacillales were more abundant in lines with low ratio. 184 strains of cultivable exopolysaccharides-producing bacteria have been isolated from the rhizosphere of some lines, including members from Rhizobiales and Bacillales. However, at this stage, we could not find a correlation between abundance of EPS-producing species in bacterial communities and the ratio RAS/RT. These results illustrated the impact of cereals genetic trait variation on soil physical properties and microbial diversity. This opens the possibility of considering plant breeding to help management of soil carbon content and physical characteristics through carbon rhizodeposition in soil.

Field Trials Reveal Ecotype-Specific Responses to Mycorrhizal Inoculation in Rice.

The overuse of agricultural chemicals such as fertilizer and pesticides aimed at increasing crop yield results in environmental damage, particularly in the Sahelian zone where soils are fragile. Crop inoculation with beneficial soil microbes appears as a good alternative for reducing agricultural chemical needs, especially for small farmers. This, however, requires selecting optimal combinations of crop varieties and beneficial microbes tested in field conditions. In this study, we investigated the response of rice plants to inoculation with arbuscular mycorrhizal fungi (AMF) and plant growth promoting bacteria (PGPB) under screenhouse and field conditions in two consecutive seasons in Senegal. Evaluation of single and mixed inoculations with AMF and PGPB was conducted on rice (Oryza sativa) variety Sahel 202, on sterile soil under screenhouse conditions. We observed that inoculated plants, especially plants treated with AMF, grew taller, matured earlier and had higher grain yield than the non-inoculated plants. Mixed inoculation trials with two AMF strains were then conducted under irrigated field conditions with four O. sativa varieties, two O. glaberrima varieties and two interspecific NERICA varieties, belonging to 3 ecotypes (upland, irrigated, and rainfed lowland). We observed that the upland varieties had the best responses to inoculation, especially with regards to grain yield, harvest index and spikelet fertility. These results show the potential of using AMF to improve rice production with less chemical fertilizers and present new opportunities for the genetic improvement in rice to transfer the ability of forming beneficial rice-microbe associations into high yielding varieties in order to increase further rice yield potentials.

HIV infection and sexually transmitted infections among men who have sex with men in Senegal.

BACKGROUND: No epidemiological study has been conducted on HIV and vulnerability to sexually transmitted diseases (STI) among men who have sex with men (MSM) in sub-Saharan Africa. METHOD: A survey including questionnaire, physical examination and detection of HIV and STI was carried out among 463 MSM, aged 18-52 years, recruited through the snowball technique in five urban sites throughout Senegal. RESULTS: A total of 21.5% of men were found to be infected with HIV [95% confidence interval (CI), 17.8-25.6]. Active syphilis, positive serology for herpes simplex virus (HSV)-2, and polymerase chain reaction detection in urine of Chlamydia and gonorrhea infections were recorded in 4.8, 22.3, 4.1 and 5.4% of participants, respectively. Most respondents reported sex with women (94.1%). In the month preceding the interview, 24% reported at least one unprotected insertive anal intercourse with a male partner, 20% at least one unprotected receptive anal intercourse, and 18% at least one unprotected intercourse with a female partner. Genital examination showed that 5% of participants had at least one clinical sign of STI. Factors associated with HIV infection were age group, the reporting of more than nine lifetime male partners [odds ratio (OR), 3.76; 95% CI, 1.61-8.79], being a waiter or bartender (OR, 3.33; 95% CI, 1.41-7.84), and living in Dakar (OR, 3.33; 95% CI, 1.07-3.43). CONCLUSION: Men who have sex with men in Senegal are highly infected with HIV and other STI. Intervention programs targeting this population are urgently needed, given their particular vulnerability and because infections are likely to disseminate into the general population given the high proportion of bisexual activity in this community.

Impact of the energy crop Jatropha curcas L. on the composition of rhizobial populations nodulating cowpea (Vigna unguiculata L.) and acacia (Acacia seyal L.).

Jatropha curcas, a Euphorbiaceae species that produces many toxicants, is increasingly planted as an agrofuel plant in Senegal. The purpose of this study was to determine whether soil priming induced by J. curcas monoculture could alter the rhizobial populations that nodulate cowpea and acacia, two locally widespread legumes. Soil samples were transferred into a greenhouse from three fields previously cultivated with Jatropha for 1, 2, and 15 years, and the two trap legumes were grown in them. Control soil samples were also taken from adjacent Jatropha-fallow plots. Both legumes tended to develop fewer but larger nodules when grown in Jatropha soils. Nearly all the nifH sequences amplified from nodule DNA were affiliated to the Bradyrhizobium genus. Only sequences from Acacia seyal nodules grown in the most recent Jatropha plantation were related to the Mesorhizobium genus, which was much a more conventional finding on A. seyal than the unexpected Bradyrhizobium genus. Apart from this particular case, only minor differences were found in the respective compositions of Jatropha soil versus control soil rhizobial populations. Lastly, the structure of these rhizobial populations was systematically imbalanced owing to the overwhelming dominance of a very small number of nifH genotypes, some of which were identical across soil types or even sites. Despite these weak and sparse effects on rhizobial diversity, future investigations should focus on the characterization of the nitrogen-fixing abilities of the predominant rhizobial strains.

Genetic and genomic diversity studies of Acacia symbionts in Senegal reveal new species of Mesorhizobium with a putative geographical pattern.

Acacia senegal (L) Willd. and Acacia seyal Del. are highly nitrogen-fixing and moderately salt tolerant species. In this study we focused on the genetic and genomic diversity of Acacia mesorhizobia symbionts from diverse origins in Senegal and investigated possible correlations between the genetic diversity of the strains, their soil of origin, and their tolerance to salinity. We first performed a multi-locus sequence analysis on five markers gene fragments on a collection of 47 mesorhizobia strains of A. senegal and A. seyal from 8 localities. Most of the strains (60%) clustered with the M. plurifarium type strain ORS 1032T, while the others form four new clades (MSP1 to MSP4). We sequenced and assembled seven draft genomes: four in the M. plurifarium clade (ORS3356, ORS3365, STM8773 and ORS1032T), one in MSP1 (STM8789), MSP2 (ORS3359) and MSP3 (ORS3324). The average nucleotide identities between these genomes together with the MLSA analysis reveal three new species of Mesorhizobium. A great variability of salt tolerance was found among the strains with a lack of correlation between the genetic diversity of mesorhizobia, their salt tolerance and the soils samples characteristics. A putative geographical pattern of A. senegal symbionts between the dryland north part and the center of Senegal was found, reflecting adaptations to specific local conditions such as the water regime. However, the presence of salt does not seem to be an important structuring factor of Mesorhizobium species.

Access to antiretroviral drugs and AIDS management in Senegal.

OBJECTIVES: Description and analysis of the Senegalese Antiretroviral Drug Access Initiative (ISAARV), the first governmental highly active antiretroviral therapy (HAART) treatment programme in Africa, launched in 1998. METHODS AND RESULTS: ISAARV was initially an experimental project designed to evaluate the feasibility, efficacy and acceptability of HAART in an African context. It was based on four principles: collective definition of the strategy, with involvement of the health professionals who would be called on to execute the programme; matching the objectives to available means (gradual enrollment according to drug availability); monitoring by several research programmes; and ongoing adaptation of treatment and follow-up according to the latest international recommendations. Persons qualifying for antiretroviral (ARV) therapy are selected on the basis of immunological and clinical criteria, regardless of economic and social considerations. A system of subsidies was created to favor access to ARV. Following the ARV price reductions that occurred in November 2000, 100% subsidies were created for the poorest participants. Optimal adherence was ensured by monthly follow-up by pharmacists and support groups held by social workers and patient associations. The chosen supply and distribution system allowed drug dispensing to be strictly controlled. CONCLUSION: The ISAARV programme demonstrates that HAART can be successfully prescribed in Africa. This experience has served as the basis for the creation of a national treatment programme in Senegal planned to treat 7000 patients by 2006.

Adherence to HAART and its principal determinants in a cohort of Senegalese adults.

BACKGROUND: Access to programmes providing highly active antiretroviral therapy (HAART) is recent in Africa. In Senegal, a national initiative was launched in 1998. The capacity of African patients to adhere to complex antiretroviral treatments (ARV) is largely unknown. METHODS: We assessed adherence and identified the main reasons for treatment interruption in a prospective observational cohort of patients participating in an ARV access programme in Dakar, Senegal. Adherence was estimated each month on the basis of the patients' stated consumption and on the proportion of the prescribed dose returned unused to the dispensing pharmacy. A total of 158 patients were studied between November 1999 and October 2001. RESULTS: A cross-section analysis showed that the stated level of adherence was high: on average, over the study period, the patients said they had taken 91% of each monthly dose and that they had taken the full monthly dose during two-thirds of the months studied. Adherence tended to be better among patients who were required to make little or no contribution to the cost of their treatment, through an appropriate pricing structure. Adherence was also better with efavirenz-containing regimens than with indinavir-containing regimens. CONCLUSION: These results show that adherence to HAART can be as high in Africa as that generally observed in industrialized countries, and that the cost and type of drug regimen must be taken into account when designing ARV access programmes for poor communities.

Prevalence of HIV and other sexually transmitted infections, and risk behaviours in unregistered sex workers in Dakar, Senegal.

OBJECTIVES: To estimate the prevalence rates of HIV and other sexually transmitted infections (STI) among unregistered sex workers, and to describe their sociodemographic characteristics and sexual behaviours, and the reasons why they were not officially registered as sex workers, in order to design specific public health interventions. METHODS: A one-stage cluster-sample survey was conducted in Dakar in 2000. Unregistered sex workers were interviewed in randomly selected establishments (official and clandestine bars, brothels and nightclubs), and blood, endocervical and vaginal samples were collected for laboratory diagnosis. RESULTS: A total of 390 women with a median age of 29 years were recruited. One-seventh of them were under the legal age for prostitution in Senegal (21 years). The median length of prostitution was 24 months and 73.5% of the women stated regular prostitution. Three-quarters of the women were found to have markers for at least one infection. The prevalence rates were as follows: HIV-1, 6.0%; HIV-2, 3.6%; HIV-1+2, 0.4%; syphilis, 23.8%; gonorrhea, 22.0%; chlamydial infection, 20.0%; trichomoniasis, 22.4%; candidiasis, 19.0%; and bacterial vaginosis, 28.8%. The main reported reason for non-registration was ignorance of the legal system and its procedures (19.4%); 18.9% of the women refused to register. One-third of the women reported that their clients used condoms inconsistently or never. CONCLUSION: This survey suggests that a multidimensional public health response is needed in Senegal, comprising legal information, downwards revision of the legal age for prostitution, and specific medical follow-up based on education, condom promotion and management of STI for non-registered sex workers.

Once-a-day highly active antiretroviral therapy in treatment-naive HIV-1-infected adults in Senegal.

OBJECTIVES: To study the effectiveness, adherence and tolerance of a once-a-day highly active antiretroviral therapy regimen in adults in Senegal. DESIGN AND METHODS: In a prospective, open-label one-arm study, 40 treatment-naive HIV-1-infected patients took the following three drugs once a day at bedtime: didanosine, lamivudine and efavirenz. The primary endpoint was the percentage of patients with plasma HIV-1 RNA below 500 copies/ml at 6 months. The analysis was done on an intent-to treat basis. RESULTS: Eighty-five per cent of patients were at Centers for Disease Control and Prevention stage B or C and the plasma HIV RNA level was 5.4 +/- 0.4 log(10) copies/ml at baseline. The percentage of patients with plasma HIV-1 RNA below 500 copies/ml at 6 months was 95% [95% confidence interval (CI), 83-99]. The proportions of patients with plasma HIV-1 RNA below 50 copies/ml at months 3, 6, 9, 12 and 15 were 26% (n = 39; 95% CI, 12-39), 78% (n = 40; 95% CI, 65-90), 70% (n = 40; 95% CI, 56-84), 77% (n = 39; 95% CI, 64-90) and 69% (n = 39; 95% CI, 55-84), respectively. The CD4 cell count was 164 +/- 75 x 106/l at baseline and increased by a mean of 199 +/- 101 x 106/l at month 15. Permanent treatment discontinuation was never necessary for serious adverse effects. Adherence was excellent, as shown by plasma drug concentrations and according to the results of the questionnaire. CONCLUSIONS: The once-daily regimen of didanosine, lamivudine and efavirenz was safe, easy-to-take and demonstrated strong antiretroviral and immunologic effects in African patients with advanced HIV infection.

Low rate of genotypic HIV-1 drug-resistant strains in the Senegalese government initiative of access to antiretroviral therapy.

OBJECTIVE: To monitor the prevalence of antiretroviral (ARV)-resistant HIV-1 viruses, and the genotypic mutations in patients enrolled in the Senegalese initiative for access to antiretroviral treatment (ART). METHODS: A total of 80 patients with a virological follow-up of at least 6 months were selected, 68 were ART-naive and 12 ART-experienced. Genotypic resistance to ARV was studied at baseline for a random subset of patients and at each rebound in plasma viral load during ART, by sequencing the protease and reverse transcriptase genes. RESULTS: At baseline, 66 patients received highly active antiretroviral therapy (HAART) [2 nucleoside reverse transcriptase inhibitors (NRTIs) +1 protease inhibitor (PI) (n = 64) or 2 NRTIs + 1 non-nucleoside reverse transcriptase inhibitor (NNRTI) (n = 2)] and 14 patients (17.5%) started with a dual therapy because of ongoing antitubercular therapy or efficient previous bitherapy for the ART-experienced patients. The emergence of drug-resistant viruses (n = 13) during follow-up was more frequent in ART-experienced patients than in ART-naive patients, 41.7 versus 11.8%, resistant viruses emerged at comparable follow-up periods, a median of 17.8 and 18.3 months, respectively. In patients receiving zidovudine and lamivudine in their drug regimen, resistance to lamivudine was more frequent than to zidovudine. Two of the three patients, with viruses resistant to PIs, acquired mutations associated with cross-resistance. Strikingly, five (39%) of the 13 patients developed resistances to drugs that they had never received (n = 3) or that they received 18 or 36 months ago (n = 2). Didanosine/stavudine pressure had selected zidovudine-resistant viruses in four patients, and indinavir had selected a nelfinavir-resistant virus in one patient. CONCLUSION: In contrast to other reports from developing countries where patients had received ARVs in an uncontrolled manner, our study showed that implementation of HAART together with good clinical, biological and logistical monitoring can reduce the emergence of resistant strains in Africa.

The Senegalese government's highly active antiretroviral therapy initiative: an 18-month follow-up study.

OBJECTIVE: To study the feasibility, effectiveness, adherence, toxicity and viral resistance in an African government HAART initiative. METHODS: A prospective observational cohort study started in Dakar in August 1998. Initial treatment consisted of two nucleoside reverse transcriptase inhibitors and one protease inhibitor. The patients attended monthly medical examinations. Plasma HIV-1 RNA and CD4 cell counts were determined at baseline and every 6 months. Intention-to-treat analyses were performed. RESULTS: Fifty-eight treatment-naive patients, mostly infected by HIV-1 strain CRF02-AG, were enrolled. Most were at an advanced stage of HIV disease (86.2% had AIDS). Adherence was good in 87.9% of patients and treatment was effective in most of them. Thus, HIV-1 RNA was undetectable in 79.6, 71.2, 51.4 and 59.3% of patients at months 1, 6, 12 and 18, respectively and the median viral load reduction was approximately 2.5 log10 copies/ml. The CD4 cell count rose by a median of 82, 147 and 180 x 106 cells/l at months 6, 12 and 18, respectively. At the same time points, the cumulative probability of remaining alive or free of new AIDS-defining events was 94.8, 85.0 and 82.3%. Most adverse effects (80.8%) were mild or moderate and only two cases of drug resistance occurred. CONCLUSION: This study shows that HAART is feasible and well tolerated in African patients. Clinical and biological results were comparable to those seen in western cohorts, despite differences in the HIV-1 subtype distribution and an advanced disease stage when the treatment was initiated. Contrary to other recent studies in Africa, viral resistance rarely emerged.

Differences in nitrogen metabolism of Faidherbia albida and other N2 -fixing tropical woody acacias reflect habitat water availability.

The activities of nitrate reductase and glutamine synthetase were evaluated in young plants of Faidherbia albida, a tropical woody legume, fed with different N sources under hydroponic conditions. Results showed that assimilation of both NO3 - and NH4 + preferentially took place in shoots. A basal amount of nitrate reductase activity was detected in shoots of plants grown with an NO3 - -free solution or placed under N2 -fixing conditions, and also in nodules of N2 -fixing plants. This strongly suggests that constitutive nitrate reductase activity is present in these organs. Analyses of the soluble nitrogenous content showed that the major form of N in the different organs was α-amino acids (particularly amides), irrespective of the N status of the culture conditions. The same result was obtained for nodulated plants grown in local sandy soil. In this case, amide-N generally accounted for more than 40% of the total soluble N. This was especially true in nodules. Ureide-N never exceeded 9% of the total soluble N and did not appear to increase with increasing nodule nitrogenase activity. Amides were also predominant in three N2 -fixing Sahelian acacias (Acacia seyal, A. nilotica and A. tortilis), showing that F. albida does not differ from Sahelian Acacia in terms of the metabolism of fixed N. However, like another Sahelian acacia growing preferentially near water (A. nilotica), F. albida can be distinguished from acacias growing strictly in arid zones (A. seyal and A. tortilis) in terms of initial growth, water and nitrate management.

Phenotypic and genotypic diversity of rhizobia nodulating Pterocarpus erinaceus and P. lucens in Senegal.

A total of fifty root nodules isolates of fast-growing and slow growing rhizobia from Pterocarpus ennaceus and Pterocarpus lucens respectively native of sudanean and sahelian regions of Senegal were characterized. These isolates were compared to representative strains of known rhizobial species. Twenty-two new isolates were slow growers and twenty-eight were fast growers. A polyphasic approach was performed including comparative total protein sodium dodecyl sulphate polyacrylamide gel (SDS-PAGE) profile analysis; 16S rDNA and 16S-23S rDNA intergenic spacer (IGS) sequence analysis. By SDS-PAGE the slow growing isolates grouped in one major cluster containing reference strains of Bradyrhizobium sp. including strains isolated in Africa, in Brazil and in New Zealand. Most of the fast-growing rhizobia grouped in four different clusters or were separate strains related to Rhizobium and Mesorhizobium strains. The 16S rDNA and 16S-23S rDNA IGS sequences analysis showed accurately the differentiation of fast growing rhizobia among the Rhizobium and Mesorbizobium genospecies. The representative strains of slow growing rhizobia were identified as closely related to Bradyrbizobium elkanii and Bradyrhizobium japonicum. Based on 16S rDNA sequence analysis, one slow growing strain (ORS199) was phylogenetically related to Bradyrbizobium sp. (Lupinus) and Blastobacter denitrificans. This position of ORS 199 was not confirmed by IGS sequence divergence. We found no clear relation between the diversity of strains, the host plants and the ecogeographical origins.

Treponemal infection rates, risk factors and pregnancy outcome in a rural area of Senegal.

A rural population of east Senegal has been under demographic surveillance for more than 30 years and a high rate of infertility has been reported. The aim of the study is to describe HIV and treponemal infection epidemiology and association with outcome of pregnancy in a population of rural Senegal. A population-based cross-sectional study was conducted among 952 randomly-selected adults of a rural community of Senegal. No participant was found to be infected with HIV, 11% had evidence of past syphilis and 5% of active syphilis. Active syphilis was associated among men with age, long-term mobility and having partners in an urban area in the last 12 months and among women with being divorced or widowed. No association was found between past or active syphilis and abortion or stillbirth but women aged 40 and more with past or active syphilis were significantly more likely to have had no history of gestation than women with no evidence of syphilis infection. In conclusion our results call for more research to understand the epidemiology of treponemal infection and to elucidate types of Treponema pallidum involved.

Eco-geographical diversity of cowpea bradyrhizobia in Senegal is marked by dominance of two genetic types.

The genetic diversity of native cowpea rhizobia originating from 60 sites across four eco-geographic zones in Senegal was studied. More than 300 cowpea nodules were analyzed by PCR-RFLP of the 16S-23S rDNA InterGenic Spacer region (IGS). Alignments of IGS sequences indicated that all genotypes were grouping within the Bradyrhizobium genus. The geographical distribution showed that apart from five IGS types, the others were specifically found in only one region. The diversity was significantly higher in the Senegal River valley zone, which presents lower mean annual rainfalls and slightly alkaline soils. Interestingly, two IGS types dominated the Senegalese rhizobial collection, one IGS type (VI) was found on more than half of the nodules collected in the northern Senegal River valley while another IGS type (I) was recovered from the great majority of nodules in the three other regions sampled. Two representative strains from each of these two dominant types were isolated and further analyzed. Multi Locus Sequence Analyses using 6 housekeeping genes indicate that they belong to a new Bradyrhizobium species closely related to B. yuanmingense. Phylogenetic analyses of 2 symbiotic genes nodC and nifH show that they are clustered with B. arachidis. Physiological tests on these strains have shown that under laboratory conditions, the growth of the IGS type VI strains was slightly less affected by a higher osmotic strength in the medium and to alkaline pH, which corroborates the soil physico-chemical parameters.

Changes in soil diversity and global activities following invasions of the exotic invasive plant, Amaranthus viridis L., decrease the growth of native sahelian Acacia species.

The objectives of this study were to determine whether the invasive plant Amaranthus viridis influenced soil microbial and chemical properties and to assess the consequences of these modifications on native plant growth. The experiment was conducted in Senegal at two sites: one invaded by A. viridis and the other covered by other plant species. Soil nutrient contents as well as microbial community density, diversity and functions were measured. Additionally, five sahelian Acacia species were grown in (1) soil disinfected or not collected from both sites, (2) uninvaded soil exposed to an A. viridis plant aqueous extract and (3) soil collected from invaded and uninvaded sites and inoculated or not with the arbuscular mycorrhizal (AM) fungus Glomus intraradices. The results showed that the invasion of A. viridis increased soil nutrient availability, bacterial abundance and microbial activities. In contrast, AM fungi and rhizobial development and the growth of Acacia species were severely reduced in A. viridis-invaded soil. Amaranthus viridis aqueous extract also exhibited an inhibitory effect on rhizobial growth, indicating an antibacterial activity of this plant extract. However, the inoculation of G. intraradices was highly beneficial to the growth and nodulation of Acacia species. These results highlight the role of AM symbiosis in the processes involved in plant coexistence and in ecosystem management programs that target preservation of native plant diversity.

Long-term efficacy and tolerance of efavirenz- and nevirapine-containing regimens in adult HIV type 1 Senegalese patients.

Owing to their low toxicity, low price, and ease of use, efavirenz (EFV) and nevirapine (NVP) are frequently used as part of antiretroviral regimens for AIDS treatment. Several clinical trials have already studied their efficacy and tolerance. However, long-term observations of the effects of these drugs in patients are limited. We used data from a prospective Senegalese cohort to analyze long-term tolerance and efficacy of these two drugs in a low-resources setting. Patients were included if they started their therapy with EFV or NVP. They were censored after treatment discontinuation. The primary endpoint was the time to treatment discontinuation. Secondary endpoints included time to death, time to disease progression, occurrence of severe adverse effects, CD4 cell recovery, and virological response. Confounding factors were controlled using marginal structural models. The median follow-up time in both EFV and NVP arms was 48 months. The hazard ratio (HR) of drug discontinuation in the EFV arm vs. the NVP arm was 0.84 (0.34; 1.87). There was a borderline difference in virological response [HR 1.38 (0.999; 1.89)] but no differences in time to death [HR 1.15 (0.41; 3.24)], time to AIDS progression [HR 1.25 (0.61; 2.58)], or time to increase in CD4 cell count above 500 cells/mm3. Adverse effects were different between NVP and EFV, but long-term tolerance was good for both. This analysis provided further information on long-term tolerance and efficacy of EFV and NVP in a resource-limited setting.

Rhizobial populations in soils from natural Acacia senegal and Acacia nilotica forests in Mauritania and the Senegal river valley.

Eighty-two strains of rhizobia were isolated from soils taken from several sites in Mauritania and Senegal. These soil samples were collected from natural stands of Acacia nilotica and Acacia senegal. The soils from Mauritania were less rich in native rhizobia than the soils from Senegal. The strains were characterized using polymerase chain reaction-restriction fragment length polymorphism and by sequencing the rDNA 16S-23S intergenic spacer region (IGS). They were sorted into seven IGS groups. These groups were not associated with the geographical origin of the strains or with the host-plant species at the site where the soils were collected. Most of the strains were in three of the IGS groups (I, IV, and V). One representative strain from each IGS group was sequenced and showed that the strains were from the genus Mesorhizobium. IGS groups I, IV, and VI were close to the species M. plurifarium (AF34563), IGS groups IIand III were close to the species Mesorhizobium sp. (AF510360), IGS group V was close to the species Mesorhizobium sp. (AF510366), and IGS group VII was close to Mesorhizobium sp. (AF510346).