Polymerase Chain Reaction (PCR) provides a superior tool for the diagnosis of Pneumococcal Infection in Burkina Faso

Purpose of study: The aim of this study was to determine the value of real-time Polymerase Chain Reaction (rt-PCR) in the routine surveillance of pneumococcal meningitis in Burkina Faso, compared to standard methods of culture, Gram stain and latex agglutination assay.Materiel and methods: A total of 385 specimens of cerebrospinal fluid were analyzed by the three standard bacteriological methods (Gram stain, latex agglutination assay, and culture) and real-time Polymerase Chain Reaction.Results: Of 385 specimens analyzed by these methods, 204 S. pneumoniae were detected by one or more  methods. Gram stain detected 36.4% (140/385) Gram positive encapsulated diplococci; 37.7% (145/385) and 20.8% (80/385) of the specimens were positive for pneumococci by latex agglutination assay and culture. These specimens were tested with rt-PCR, which confirmed 51.2% (197/385) S. pneumoniae positive. The sensitivity and specificity of culture were 54.4% and 31.5%, respectively, and the sensitivity and specificity of rt-PCR were 96.6% and 100%, respectively. These results showed that rt-PCR was more sensitive than Gram stain (p=0.0235), latex agglutination assay (p=0.0442)and culture (p=0.0006).The culture is the gold standard method; however, the result showed that rt-PCR had specificity and was as specific as Gram stain (p=0.3405) and latex agglutination assay (p=0.7745).Conclusion: rt-PCR was highly sensitive and specific. It could be used as a complementary diagnostic tool to  mprove case confirmation of bacterial meningitis. However,its high cost, the qualification of the technical staff and infrastructures required for its implementation, constitute obstacles to its widened use in countries with limited resources.Keywords: Streptococcus pneumoniae, meningitis, rt-PCR, standard bacteriological methods Objectif: Le but de cette étude était de déterminer la place de la rt-PCR dans la surveillance de routine deméningitespneumococciquesau Burkina Faso et la comparée avec les méthodes de la bactériologie classique: Culture, coloration de Gram et l’agglutination au latex.Matériel etméthodes: Au total, 385 échantillons deliquides céphalorachidiens (LCR)étaient analysés par les trois méthodes de la bactériologie classique (coloration de Gram, agglutination au latex, culture) et la PCR en temps réel.RESULTATS: Parmi 385 échantillons analysés, 204 cas de Streptococcuspneumoniae étaient détectés par une ou plusieurs méthodes. La coloration de Gram adétecté 36,4% (140/385) diplocoques encapsulés à Gram positif (DGP); 37,7% (145/385) et 20,8% (80/385) d’échantillons étaient positifs aux pneumocoques par l’agglutination au latex et la culture. Ces échantillons étaient aussi testés par rt-PCR qui a confirmé 51,2% (197/385) cas positifs de S. pneumoniae. La sensibilité et la spécificité de la culture étaient respectivement de 54,4% et 31,5%, et la sensibilité et la spécificité de rt-PCR étaient respectivement de 96,6% et 100%. Ces résultats ont montré que la rt-PCR était plus sensible que la coloration de Gram (p=0,0235), l’agglutination au latex (p=0,0442) et la  culture(p=0,0006).La culture est une méthode de référence; cependant, le résultat a montré que rt-PCR était plus sensibleet aussi spécifique que la coloration de Gram ((p=0,3405)et l’agglutination au latex (p=0,7745).Conclusion : :rt-PCR était plus sensible et plus spécifique. Elle pourrait être utilisée comme un outil de diagnosticcomplémentaire pour améliorer les cas de confirmation de méningites bactériennes. Cependant, ces coûts de réalisation, la qualification de techniciens et les matériels pour son application constituent des obstacles pour sa vulgarisation dans les pays à ressources limités.Keywords: Streptococcus pneumoniae, méningites, rt-PCR, méthodes de la bactériologie classique Article in English

Early infant HIV-1 diagnosis programs in resource-limited settings: opportunities for improved outcomes and more cost-effective interventions

Early infant diagnosis (EID) of HIV-1 infection confers substantial benefits to HIV-infected and HIV-uninfected infants, to their families, and to programs providing prevention of mother-to-child transmission (PMTCT) services, but has been challenging to implement in resource-limited settings. In order to correctly inform parents/caregivers of infant infection status and link HIV-infected infants to care and treatment, a 'cascade' of events must successfully occur. A frequently cited barrier to expansion of EID programs is the cost of the required laboratory assays. However, substantial implementation barriers, as well as personnel and infrastructure requirements, exist at each step in the cascade. In this update, we review challenges to uptake at each step in the EID cascade, highlighting that even with the highest reported levels of uptake, nearly half of HIV-infected infants may not complete the cascade successfully. We next synthesize the available literature about the costs and cost effectiveness of EID programs; identify areas for future research; and place these findings within the context of the benefits and challenges to EID implementation in resource-limited settings

Visual mismatch negativity to vanishing parts of objects in younger and older adults.

We investigated visual mismatch negativity (vMMN) to vanishing parts of continuously present objects by comparing the event-related potentials (ERPs) to infrequently (deviant) and frequently (standard) disappearing parts of the objects. This paradigm both excludes low-level stimulus-specific adaptation differences between the responses to deviants and standards, and increases the ecological validity of the stimuli. In comparison to frequently disappearing parts of the stimulus objects, infrequently vanishing parts elicited posterior negative event-related brain activity (vMMN). However, no vMMN emerged to the reappearance of the same parts of the objects. We compared the ERPs of an older and a younger sample of participants. In the 120-180 ms time period vMMN was similar in the two age groups, but in the 180-220 ms time period vMMN emerged only in the younger participants. We consider this difference as an index of more elaborate automatic processing of infrequent stimulus changes in younger adults