Quantifying and characterizing hourly human exposure to malaria vectors bites to address residual malaria transmission during dry and rainy seasons in rural Southwest Burkina Faso.

BACKGROUND: To sustain the efficacy of malaria vector control, the World Health Organization (WHO) recommends the combination of effective tools. Before designing and implementing additional strategies in any setting, it is critical to monitor or predict when and where transmission occurs. However, to date, very few studies have quantified the behavioural interactions between humans and Anopheles vectors in Africa. Here, we characterized residual transmission in a rural area of Burkina Faso where long lasting insecticidal nets (LLIN) are widely used. METHODS: We analysed data on both human and malaria vectors behaviours from 27 villages to measure hourly human exposure to vector bites in dry and rainy seasons using a mathematical model. We estimated the protective efficacy of LLINs and characterised where (indoors vs. outdoors) and when both LLIN users and non-users were exposed to vector bites. RESULTS: The percentage of the population who declared sleeping under a LLIN the previous night was very high regardless of the season, with an average LLIN use ranging from 92.43 to 99.89%. The use of LLIN provided > 80% protection against exposure to vector bites. The proportion of exposure for LLIN users was 29-57% after 05:00 and 0.05-12% before 20:00. More than 80% of exposure occurred indoors for LLIN users and the estimate reached 90% for children under 5 years old in the dry cold season. CONCLUSIONS: LLINs are predicted to provide considerable protection against exposure to malaria vector bites in the rural area of Diébougou. Nevertheless, LLIN users are still exposed to vector bites which occurred mostly indoors in late morning. Therefore, complementary strategies targeting indoor biting vectors in combination with LLIN are expected to be the most efficient to control residual malaria transmission in this area.

A Behavioral and Serological Survey on HIV Prevalence Among Prisoners in Benin.

Cases of HIV are common in Benin, with infection rates varying according to socioeconomic and cultural factors, and by region. Certain segments of the population, such as prison inmates, sex worker clients and truck drivers are at high risk for HIV/AIDS. The aim of this study is to identify which behavioral and serological indicators contribute to the spread of HIV among prisoners. A total of 496 inmates from prisons located in all major cities in Benin were surveyed. Data was collected through interview sessions carried out using a questionnaire and through blood samples. The results show that most inmates are Beninese (83.5%), and the average age is 33 years (range: 14-80 years). No prisoner reported using a condom the last time they engaged in sexual intercourse. Blood exposure was found in 14.6% of inmates and HIV was detected in 1.4% of cases. Our analysis indicates that the length of detention and gender are factors that influence HIV status. However, age, education, nationality and HIV awareness had no significant effect on HIV prevalence among inmates. The results highlight the need to raise awareness in prisons about HIV. This can be achieved by strengthening communication strategies and by organizing HIV and sexually transmitted diseases information sessions for both prison officers and inmates.

Traditional treatment of human and animal salmonelloses in Southern Benin: Knowledge of farmers and traditherapists.

AIM: This study aimed to report medicinal plants that are likely to be used in the control of salmonellosis. MATERIALS AND METHODS: A cross-sectional study was conducted in Southern Benin. Semi-structured questionnaires were administered to 150 farmers and 100 traditional therapists in seven high municipalities. This step helped to collect plants that are used in the treatment of animal salmonellosis and typhoid fever in human. RESULTS: The results revealed a low level of use of medicinal plants among breeders who prefer antibiotics such as oxytetracycline (53.55%), tylosine + sulfadimerazine (15.30%), and alphaceryl (19.13%). However, plants such as Moringa oleifera (leaves), Carica papaya (leaves and seeds), and Vernonia amygdalina (leaves) were mostly used by some farmers. From traditional therapists, 57 plant species of 32 families were identified as typhoid fever cures; among which Leguminosae, Asteraceae, and Euphorbiaceae were predominant. Persea americana (22.72%), V. amygdalina (7.57%), and Corchorus olitorius (7.57%) were the most cited by traditherapists for the treatment of typhoid fever in human. CONCLUSION: This study provides a database for further studies on the in vitro and in vivo efficacy of Benin plant species on Salmonellaspp. These evaluations will guarantee the availability of new therapeutic solutions for populations.

[Study of the prevalence of neonatal thyroid disturbances in Benin]. / Etude de la prevalence des perturbations thyroïdiennes neonatales au Benin.

OBJECTIVE: Observing the concentrations of free thyroxine (FT4) and thyrotropin (TSH), in infants born in Cotonou, Benin to establish the profile of neonatal thyroid disturbance. DESIGN AND SUBJECTS: The detection of thyroid immune status was done by measuring the antibodies to thyroglobulin (Tg Ab Anti) and Antibody and Anti Thyroperoxidase (Anti TPO Ab) ratio. Blood was collected from 177 neonates aged 0 to 7 days. RESULTS: We measured free thyroxine, thyrotropin , and antibodies to thyroglobulin, Anti Thyroperoxidase and detected a prevalence of dysfunction of the thyroid gland in neonates is from 28% for hypothyroidism, 2.25% of hyperthyroidism. Among hypothyroid, there was a frank hypothyroidism of 53%, hypothyroidism in 25% Primary, secondary hypothyroidism of 20% and hypothyroidism unspecified 2%. Also 73.33% of hypothyroid shows an antibody against thyroglobulin above the threshold of normality and 41.18% of euthyroid have a high Anti thyroglobulin Antibody This allows us to suggest lymphocytic thyroiditis. CONCLUSION: The results of our studies show the onset of thyroid disease after neonatal hypothyroidism very pronounced. This is probably due to a transfer of the Anti- thyroglobulin Antibody of maternal origin to the fetus during pregnancy.

BUT: La détermination des concentrations de thyroxine libre (T4 libre) et de thyrotropine (TSH), chez 177 nouveaux nés âgés de 0 à 7 jours à Cotonou au Bénin a permis d'établir le profil de perturbations thyroïdiennes néonatales. MATÉRIELS ET MÉTHODE: L'état thyroïdien immunitaire a été mis en évidence par le dosage des anticorps anti thyroglobuline (Ac Anti Tg) et Anticorps anti Thyroperoxydase (Ac Anti TPO). RÉSULTATS: La prévalence du dysfonctionnement de la glande thyroïde chez les nouveaux nés a été de 28% d'hypothyroïdie et 2,25 % d'hyperthyroïdie. Parmi les hypothyroïdiens, on note une hypothyroïdie franche de 53%, une hypothyroïdie primaire de 25%, une hypothyroïdie secondaire de 20% et une hypothyroïdie indéterminée de 2%. Aussi 73,33% des hypothyroïdiens présentent-ils un taux d'anticorps anti thyroglobulines supérieur au seuil de la normalité et 41,18% des euthyroïdiens, un taux élevé d'anticorps anti thyroglobulines. Ceci a permis de suggérer une thyroïdite lymphocytaire. CONCLUSION: Les résultats des travaux ont montré l'apparition des affections thyroïdiennes néonatales par une l'hypothyroïdie très prononcée. Celle-ci est probablement due à un transfert de l'anticorps anti thyroglobuline d'origine maternelle vers le fœtus pendant la gestation.

Epidemiology and prevention of nosocomial pneumonia associated with Panton-Valentine Leukocidin (PVL) producing Staphylococcus aureus in Departmental Hospital Centre of Zou Collines in Benin.

BACKGROUND: An eight (8) months prospective study was carried out to control an outbreak of nosocomial pneumonia due to a Panton-Valentine Leukocidin (PVL) producing Staphylococcus aureus, in the paediatrics' unit at the Zou/Collines Departmental Hospital (CHDZ/C), (Benin). METHODS: Between 1(st) September 2004 and 30(th) May 2005 an investigation was conducted that involved the screening of all patients suspected to have nosocomial pneumonia, hospital environment sampling and the follow-up of cases until the end of hospital admission period. Isolates were identified, tested for antimicrobial susceptibility and analysed for PVL production. The study period was divided into Period I, corresponding to the outbreak period and Period II, after the complete renovation of the Unit along with hand washing promotion. RESULTS: A total of 453 patients were admitted during the period of the study; (235 during Period I and 218 during Period II) in the malnourished children sector. Twenty eight (28) cases of pneumonia due to S. aureus were discovered and PVL-producing S. aureus constituted 61% (17/28) of identified cases. The mortality rate among the PVL- producing strains was 15/17 (88%) while it was 1/11 (9%) among non PVL-producing strains. Enhanced hygiene measures helped to terminate the outbreak. CONCLUSIONS: This study showed that PVL was strongly linked to nosocomial pneumonia. PVL-producing S aureus can be controlled in the hospital by a combination of the promotion of preventive measures, decontamination of the environment and the early use of the correct antibiotic at the appropriate dose and for an adequate duration.

Virulence factors produced by strains of Staphylococcus aureus isolated from urinary tract infections.

Staphylococcus aureus infections are widely prevalent in West Africa and are often associated with urinary tract infections (UTIs). Virulence factors from S. aureus have rarely been described for such infections. The purpose of the current study was to determine the prevalence of toxins and adhesion factors obtained from S. aureus isolated from presumed primary UTIs at the Cotonou University Hospital (CUH) in Benin as compared with the Strasbourg University Hospital (SUH) in France. Both ambulatory and hospitalised patients were included in the study. Sixty-five independent strains of S. aureus from CUH and 35 strains from SUH were obtained over a four-month period. Virulence factors were characterised by immunodetection or multiplex polymerase chain reaction, and meticillin susceptibility was recorded. Approximately 50% of all isolates produced at least one enterotoxin. No isolate from SUH produced Panton-Valentine leucocidin (PVL), whereas 21.5% of the S. aureus isolates from CUH produced PVL (P<0.01). Six of 14 (43%) PVL-positive isolates were meticillin-resistant. At SUH, the incidence of MRSA (57%) was significantly higher (P<0.01) than at CUH (14%). Genes encoding clumping factor B, and elastin and laminin binding proteins were detected in almost all isolates (80%), irrespective of the geographical origin. The results for elastin binding protein differed significantly from published data regarding isolates from other clinical origins. Staphylococcal toxins and adhesion factors may be important in the physiopathology of UTI.

[Production lead time of coagulase in 180 Staphylococcus aureus strains collected at Abidjan]. / Delai de production de la coagulase chez 180 souches de Staphylococcus aureus isolees a Abidjan.

INTRODUCTION: The pathogenic capacity of S. aureus is related.to the production of many virulence factors of which the coagulase. Several genotypes of coagulase were described and are associated to various populations of S. aureus. According the susceptibility to methicillin, methicillin-resistant strains of S. aureus, are described. The aim of this subject was to study the coagulase expression of Staphylococcus aureus according to the site of infection, patient origin and the resistance against methicillin. MATERIAL AND METHODS: The study is related about 180 strains of S. aureus collected in the three University Teaching Hospital of Abidjan. S. aureus are identified with laboratory classical methods. Coagulase delay was determined by the test of the coagulase on citrated rabbit plasma at 2, 4 and 18 hours. The resistance against methicillin was researched by disc diffusion agar technique. RESULTS: In 60% of cases, the bacterial strains gave a coagulum at the end of four hours, fast coagulase, against 40% of strains whose coagulating activity appeared at 18 h, slow coagulase. Fast coagulase strains are isolated from the majority of infections (55% to 71%), in hospital patients (66%) and in paediatrics (58%). Fast coagulase strains are methicillin-resistant in 65% of cases against 48.5% of methicillin-susceptible and low coagulase strains (p < 0.0001). CONCLUSION: According to the production lead time of the coagulase, fast coagulase and slow coagulase variants of S. aureus coexisted. The expression of the coagulase is not related to the site of infection and the origin of the patients. On the other hand, the type of coagulase is associated to resistance of methicillin. However, the time of formation of the coagulum typed by the test of the coagulase, didn't constitute a sufficient discriminating factor in the medical following and the treatment of infections caused by S. aureus.

[Incidence of infections dues to Escherichia coli strains producing extended spectrum betalactamase, in the Zou/Collines Hospital Centre (CHDZ/C) in Benin]. / Incidence d'infections liées à Escherichia coli producteur de bêta lactamase à spectre élargi au Centre hospitalier départemental du Zou et Collines au Bénin.

OBJECTIVES: Over a 6-month period, extended-spectrum betalactamase (ESBL)-producing isolates of Escherichia coli (EC) were collected from in-patients and their environment at the Zou-Collines Hospital Centre (CHDZ/C) in Benin. The aim of this study was to determine the incidence of ESBL and to describe their phenotypic susceptibility to antibiotics in a secondary hospital (500 beds) in Benin. METHODS: From 15 May to 15 November 2005, clinical informations and samples were collected from patients suspected to have nosocomial infections. The isolates were identified, tested for antimicrobial susceptibility and analysed for the presence of ESBL genes blaTEM and blaSHV by PCR. RESULTS: One hundred ninety-seven enterobacteria were isolated from the clinical samples of 342 patients, these isolates included 143 EC and 32/143 (22%) of these isolates produced ESBL. Forty-six EC were isolated from the environment and 7 (15%) of them produced ESBL. Except for Imipenem for which the difference was not significant, the isolates producing ESBL were more resistant to the other antibiotics (especially to third generation cephalosporins: Ceftriaxone, Cefotaxime, Ceftazidime (P<0.00001)) than non-ESBL producing isolates. Both ESBL genes blaSHV and blaTEM were identified in the EC ESBL strains from patient and from the environment. CONCLUSION: This study shows the presence of ESBL genes among EC in various wards of the CHDZ/C hospital proving that there is a need to implement a strict hospital infection control program and a regular surveillance of resistance to antimicrobial agents.

[Incidence of meticillin-resistant Staphylococcus aureus in neonatal care unit of departmental hospital centre of Zou Collines in Benin]. / Incidence de Staphylococcus aureus résistant à la méticilline dans le service de néonatologie du centre hospitalier départemental du Zou et des Collines au Bénin.

UNLABELLED: Meticillin resistant Staphylococcus aureus (MRSA) is among the most important causes of nosocomial infections. It possesses a particular ability to spread in hospitals worldwide. OBJECTIVE: To analyze the proportion of MRSA among S. aureus isolated from specimen taken for diagnosis purposes. To make the medical staff aware of the problem of MRSA infections and to take a better care of patients. PATIENTS AND METHODS: During 3 months, a prospective study was carried out in the neonatal unit of centre hospitalier départemental du Zou et Collines in Benin. We identified newborn carriers of SA, particularly MRSA and factors associated with the carriage. Two hundred and ninety patients were admitted in the 3 divisions of the neonatal unit. From 195 specimens examined for diagnosis purposes 48 h after hospitalization, 112 patients were detected by nose swabbing. Concurrently, swabbing of environment was achieved. RESULTS: Among patients'specimens, 141 isolations of S. aureus were observed. The proportion of MRSA was 36% amongst diagnostic specimens. MRSA represented 39% of the environment specimens. None of the isolated MRSA produces Panton Valentine leukocidin. CONCLUSION: Our survey revealed a high level of MRSA among S. aureus isolated from diagnostic specimens. Consecutive to such findings and for decreasing nosocomial infection, an appropriate prevention program was installed, including intensive promotion of hands hygiene, correct sterilization and disinfection of materials and patients.

Discoupling the Ca(2+)-activation from the pore-forming function of the bi-component Panton-Valentine leucocidin in human PMNs.

The consecutive cell activation, including Ca(2+)-channel opening, and pore formation leading to human neutrophil lysis were the two functions of the staphylococcal Panton-Valentine leucocidin attempted to be discoupled by site-directed mutagenesis. In a first approach consisting in deletions of the cytoplasmic extremity of the transmembranous domain, we produced a LukF-PV DeltaSer125-Leu128 with a slightly reduced Ca(2+) induction but with a significantly lowered lytic activity when combined with its synergistic protein LukS-PV. The second approach consisted in the modification of charges and/or introduction of a steric hindrance inside the pore, which also led to interesting mutated proteins: LukF-PV G131D, G131W and G130D. The latter had an intact Ca(2+) induction ability while the lytic one was 20-fold diminished. Binding properties and intrinsic pore diameters of these discoupled toxins remained comparable to the wild-type protein. The mutated proteins promoted interleukin-8 secretion, but they were rather inactive in an experimental model. New insights are brought concerning the role of the two functions in the virulence of this bi-component leucotoxin.

The structure of a Staphylococcus aureus leucocidin component (LukF-PV) reveals the fold of the water-soluble species of a family of transmembrane pore-forming toxins.

BACKGROUND: Leucocidins and gamma-hemolysins are bi-component toxins secreted by Staphylococcus aureus. These toxins activate responses of specific cells and form lethal transmembrane pores. Their leucotoxic and hemolytic activities involve the sequential binding and the synergistic association of a class S and a class F component, which form hetero-oligomeric complexes. The components of each protein class are produced as non-associated, water-soluble proteins that undergo conformational changes and oligomerization after recognition of their cell targets. RESULTS: The crystal structure of the monomeric water-soluble form of the F component of Panton-Valentine leucocidin (LukF-PV) has been solved by the multiwavelength anomalous dispersion (MAD) method and refined at 2.0 A resolution. The core of this three-domain protein is similar to that of alpha-hemolysin, but significant differences occur in regions that may be involved in the mechanism of pore formation. The glycine-rich stem, which undergoes a major rearrangement in this process, forms an additional domain in LukF-PV. The fold of this domain is similar to that of the neurotoxins and cardiotoxins from snake venom. CONCLUSIONS: The structure analysis and a multiple sequence alignment of all toxic components, suggest that LukF-PV represents the fold of any water-soluble secreted protein in this family of transmembrane pore-forming toxins. The comparison of the structures of LukF-PV and alpha-hemolysin provides some insights into the mechanism of transmembrane pore formation for the bi-component toxins, which may diverge from that of the alpha-hemolysin heptamer.

[Pore-forming leukotoxins from Staphylococcus aureus: variability of the target cells and 2 pharmacological processes]. / Les leucotoxines formant des pores de Staphylococcus aureus: variabilité des cellules-cible et deux processus pharmacologiques.

The staphylococcal bi-component leukotoxins constitute a family included in the super-family of the beta-sheet-structured pore-forming toxins. They may be produced by Staphylococcus aureus and by Staphylococcus intermedius and their target cells vary according to the molecules. The mode of action proceeds by the sequential binding of the class S proteins, then by that of the class F proteins at the surface of the membranes. Then, the activation of cellular calcium-channels precedes the pore formation which seems to be sensitive to several monovalent cations. The cell response is inflammatory and includes the neosynthesis as well as the secretion of leukotriene B4, interleukin -8, histamine. The injection of leukotoxins to rabbits generates cell chemotaxis , vasodilatation, and tissue necrosis. The association of the production of leukotoxins with clinical syndromes concerns several aspects of the pathology of S. aureus, and confers to these leukotoxins an important role of virulence factors.

A predicted beta-sheet from class S components of staphylococcal gamma-hemolysin is essential for the secondary interaction of the class F component.

Site-directed mutagenesis was performed on genes encoding HlgA and HlgC, two of the three proteins expressed from the staphylococcal y-hemolysin locus, which originate two pore-forming toxins (HlgA + HlgB, HlgC + HlgB). As related proteins, HlgA and HlgC were found to bind first to cell membranes. Amino acid substitutions concerned residues that would predictably disrupt a 13 amino acid conserved beta-sheet of the Chou and Fasman secondary structure prediction. The mutation of a threonin into an aspartic acid residue from HlgA (T28D) and from HlgC (T30D) that would break this predicted N-terminal structure lowered dramatically the biological activities on purely lipidic vesicles, erythrocytes and polymorphonuclear cells. The change in secondary structure was confirmed by Fourier Transformed Infrared spectroscopy. The binding of mutated and native proteins at the same kind of sites onto polymorphonuclear cells was evidenced with flow cytometry and fluorescein-labelled anti-class S antibodies or wild type HlgA or HlgC. However, the subsequent binding of fluorescein-labelled HlgB to membrane-bound mutated HlgA or HlgC complexes was inhibited. In conclusion, the first binding of class S components is essential for the subsequent binding of class F components, and a predicted beta-sheet seems to be at least one of the functional domains involved.