Validation of a New Rapid Detection Test for Detection of Neisseria meningitidis A/C/W/X/Y Antigens in Cerebrospinal Fluid.

Meningococcal meningitis remains a life-threatening disease worldwide, with high prevalence in the sub-Saharan meningitis belt. A rapid diagnosis is crucial for implementing adapted antimicrobial treatment. We describe the performances of a new immunochromatographic test (MeningoSpeed, BioSpeedia, France) for detecting and grouping Neisseria meningitidis Cerebrospinal fluids (CSFs) were collected from 5 African countries and France. For the rapid diagnostic test (RDT), the CSF sample was deposited on each of the 3 cassettes for a total volume of 90 µl. The results of the RDT were compared to those of a reference multiplex PCR assay detecting the major serogroups of N. meningitidis on 560 CSF specimens. Five specimens were found uninterpretable by RDT (0.9%). The results of interpretable specimens were as follows: 305 positive and 212 negative samples by both techniques, 14 positive by PCR only, and 24 positive by RDT only (sensitivity, specificity, and positive and negative predictive values of 92.7%, 93.8%, 95.6%, and 89.8%, respectively, with an accuracy of 93.2% and a kappa test of 0.89; P < 0.05). From 319 samples positive by PCR for serogroups A, C, W, X, or Y, the grouping results were concordant for 299 specimens (sensitivity of 93.0%, 74.4%, 98.1%, 100%, and 83.3% for serogroups A, C, W, X, and Y, respectively). The MeningoSpeed RDT exhibited excellent performances for the rapid detection of N. meningitidis antigens. It can be stored at room temperature, requires a minimal amount of CSF, is performed in 15 minutes or less, and is easy to use at bedside.

Strategy using a new antigenic test for rapid diagnosis of Streptococcus pneumoniae infection in respiratory samples from children consulting at hospital.

BACKGROUND: Despite vaccination programs, Streptococcus pneumoniae remains among the main microorganisms involved in bacterial pneumonia, notably in terms of severity. The prognosis of pneumococcal infections is conditioned in part by the precocity of the diagnosis. The aim of this study was to evaluate the impact of a Rapid Diagnostic Test (RDT) targeting cell wall polysaccharide of Streptococcus pneumoniae and performed directly in respiratory samples, on the strategy of diagnosis of respiratory pneumococcal infections in children. RESULTS: Upper-respiratory tract samples from 196 children consulting at hospital for respiratory infection were tested for detecting S. pneumoniae using a newly-designed RDT (PneumoResp, Biospeedia), a semi-quantitative culture and two PCR assays. If positive on fluidized undiluted specimen, the RDT was repeated on 1:100-diluted sample. The RDT was found highly specific when tested on non-S. pneumoniae strains. By comparison to culture and PCR assays, the RDT on undiluted secretions exhibited a sensitivity (Se) and negative predictive value (NPV) of more than 98%. By comparison to criteria of S. pneumoniae pneumonia combining typical symptoms, X-ray image, and culture ≥107 CFU/ml, the Se and NPV of RDT on diluted specimens were 100% in both cases. CONCLUSIONS: In case of negative result, the excellent NPV of RDT on undiluted secretions allows excluding S. pneumoniae pneumonia. In case of positive result, the excellent sensitivity of RDT on diluted secretions for the diagnosis of S. pneumoniae pneumonia allows proposing a suitable antimicrobial treatment at day 0.

Improving survival and storage stability of bacteria recalcitrant to freeze-drying: a coordinated study by European culture collections.

The objective of this study is to improve the viability after freeze-drying and during storage of delicate or recalcitrant strains safeguarded at biological resource centers. To achieve this objective, a joint experimental strategy was established among the different involved partner collections of the EMbaRC project ( www.embarc.eu ). Five bacterial strains considered as recalcitrant to freeze-drying were subjected to a standardized freeze-drying protocol and to seven agreed protocol variants. Viability of these strains was determined before and after freeze-drying (within 1 week, after 6 and 12 months, and after accelerated storage) for each of the protocols. Furthermore, strains were exchanged between partners to perform experiments with different freeze-dryer-dependent parameters. Of all tested variables, choice of the lyoprotectant had the biggest impact on viability after freeze-drying and during storage. For nearly all tested strains, skim milk as lyoprotectant resulted in lowest viability after freeze-drying and storage. On the other hand, best freeze-drying and storage conditions were strain and device dependent. For Aeromonas salmonicida CECT 894(T), best survival was obtained when horse serum supplemented with trehalose was used as lyoprotectant, while Aliivibrio fischeri LMG 4414(T) should be freeze-dried in skim milk supplemented with marine broth in a 1:1 ratio. Freeze-drying Campylobacter fetus CIP 53.96(T) using skim milk supplemented with trehalose as lyoprotectant resulted in best recovery. Xanthomonas fragariae DSM 3587(T) expressed high viability after freeze-drying and storage for all tested lyoprotectants and could not be considered as recalcitrant. In contrary, Flavobacterium columnare LMG 10406(T) did not survive the freeze-drying process under all tested conditions.

A new zebrafish model of oro-intestinal pathogen colonization reveals a key role for adhesion in protection by probiotic bacteria.

The beneficial contribution of commensal bacteria to host health and homeostasis led to the concept that exogenous non-pathogenic bacteria called probiotics could be used to limit disease caused by pathogens. However, despite recent progress using gnotobiotic mammal and invertebrate models, mechanisms underlying protection afforded by commensal and probiotic bacteria against pathogens remain poorly understood. Here we developed a zebrafish model of controlled co-infection in which germ-free zebrafish raised on axenic living protozoa enabled the study of interactions between host and commensal and pathogenic bacteria. We screened enteric fish pathogens and identified Edwardsiella ictaluri as a virulent strain inducing a strong inflammatory response and rapid mortality in zebrafish larvae infected by the natural oro-intestinal route. Using mortality induced by infection as a phenotypic read-out, we pre-colonized zebrafish larvae with 37 potential probiotic bacterial strains and screened for survival upon E. ictaluri infection. We identified 3 robustly protective strains, including Vibrio parahaemolyticus and 2 Escherichia coli strains. We showed that the observed protective effect of E. coli was not correlated with a reduced host inflammatory response, nor with the release of biocidal molecules by protective bacteria, but rather with the presence of specific adhesion factors such as F pili that promote the emergence of probiotic bacteria in zebrafish larvae. Our study therefore provides new insights into the molecular events underlying the probiotic effect and constitutes a potentially high-throughput in vivo approach to the study of the molecular basis of pathogen exclusion in a relevant model of vertebrate oro-intestinal infection.

Lactobacillus pasteurii sp. nov. and Lactobacillus hominis sp. nov.

Strains 1517(T) and 61D(T) were characterized by phenotypic and molecular taxonomic methods. These Gram-positive lactic acid bacteria were homo-fermentative, facultatively anaerobic short rods. They were phylogenetically related to the genus Lactobacillus according to 16S rRNA gene sequence analysis, with 99 % similarity between strain 1517(T) and the type strain of Lactobacillus gigeriorum, and 98.6, 98.5 and 98.4 % between strain 61D(T) and Lactobacillus gasseri, Lactobacillus taiwanensis and Lactobacillus johnsonii, respectively. Multilocus sequence analysis and metabolic analysis of both strains showed variation between the two strains and their close relatives, with variation in the position of the pheS and rpoA genes. The DNA-DNA relatedness of 43.5 % between strain 1517(T) and L. gigeriorum, and 38.6, 29.9 and 39.7 % between strain 61D(T) and L. johnsonii, L. taiwanensis and L. gasseri, respectively, confirmed their status as novel species. Based on phenotypic and genotypic characteristics, two novel species of Lactobacillus are proposed: Lactobacillus pasteurii sp. nov., with 1517(T) ( = CRBIP 24.76(T) = DSM 23907(T)) as the type strain, and Lactobacillus hominis sp. nov., with 61D(T) (=CRBIP 24.179(T) = DSM 23910(T)) as the type strain.

Implementation of the Nagoya Protocol within the Collection of Institut Pasteur.

The focus of the EU regulations on the Nagoya Protocol on Access and Benefit-Sharing leaves the control of access to genetic resources up to each member state. France has chosen to control access and is going to put in place regulations for it. All the materials received should have specific documentation regarding the accession of genetic resources, where there is a National Authority to issue them. The European commission will maintain a list of biological collections with registered status proposed by each country. The member states are responsible for considering inclusion and verification of these collections. In recent years, the Collection of Institut Pasteur (CIP) staff has expressed concern over how to interact with the implementation of the Nagoya Protocol in the collection but also at the national level with the aim that the CIP will be a registered collection. The advantage of accessing resources from a registered collection is that users of genetic resources will be considered as having exercised 'due diligence' if they source their genetic resources from these collections. This could facilitate the process for scientists when applying for research funding. The CIP organized the accession of new deposits and the distribution of micro-organisms in connection with it.

Reduced CD4 T cell activation and in vitro susceptibility to HIV-1 infection in exposed uninfected Central Africans.

BACKGROUND: Environmentally driven immune activation was suggested to contribute to high rates of HIV-1 infection in Africa. We report here a study of immune activation markers and susceptibility to HIV-1 infection in vitro of forty-five highly exposed uninfected partners (EUs) of HIV-1 infected individuals in Central African Republic, in comparison with forty-four low-risk blood donors (UCs). RESULTS: Analysis of T lymphocyte subsets and activation markers in whole blood showed that the absolute values and the percentage of HLA-DR+CD4 T cells and of CCR5+CD4 T cells were lower in the EUs than in the UCs (p = 0.0001). Mutations in the CCR5 coding region were not found in either group. Susceptibility to in vitro infection of unstimulated peripheral blood mononuclear cells, prior of PHA activation, was decreased in EUs compared to UCs, either using a CXCR4-tropic or a CCR5-tropic HIV-1 strain (p = 0.02 and p = 0.05, respectively). Levels of MIP-1beta, but not of MIP-1alpha or RANTES, in the supernatants of PHA-activated PBMC, were higher in the EUs than in the UCs (p = 0.007). CONCLUSION: We found low levels of CD4 T cell activation and reduced PBMC susceptibility to HIV-1 infection in Central African EUs, indicating that both may contribute to the resistance to HIV-1 infection.

Isotype profiles of anti-gp160 antibodies from HIV-infected patients in plasma and culture supernatants.

We studied isotype profiles of anti-HIV antibodies (Ab) in HIV-1-infected African patients with high viral loads and major B cell dysfunction. We focussed on IgG1, IgG3, and IgA as these classes and subclasses tend to support neutralizing functions against HIV. Total IgG1, IgG3 and IgA were detected in the plasma of both HIV-1-infected and HIV-negative African individuals, but there was significantly more IgG3, a rare subclass, in HIV-1-infected patients (P < 0.05). Anti-HIV-gp160 specific antibodies were detected in sera from nearly all HIV-1-infected individuals tested, but not in HIV- individuals: 10/10, 9/10 and 8/10 individuals displayed specific IgG1, IgG3 and IgA, respectively. In the corresponding PBMC cultures carried out in the presence of IL-10 and IL-2, there was specific IgG1 and IgA in 5/10, and 3/10, respectively, but no IgG3 was detected. When HAART-treated European HIV-infected PBMC cultures were tested using the same protocol, specific IgG3 was detected in 4/10 cultures, and was unaffected by the addition of soluble CD40L molecules. The present study thus shows that, despite lymph node disorganization in HIV-infected drug-naïve Africans, these individuals retain the ability to produce HIV-specific IgG1, IgG3 and IgA. However, the specific mechanisms controlling the selective production of IgG3, probably the most potent subclass and a potential target of immuno-intervention, warrants further investigation.

Broad spectrum of coreceptor usage and rapid disease progression in HIV-1-infected individuals from Central African Republic.

To study the progression of HIV-1 infection and coreceptor usages in Central African Republic, clinical data, plasma viral load, and coreceptor usage of sequential HIV-1 isolates were analyzed in a seroincident prospective cohort (PRIMOCA). Twenty-three HIV-1 infected individuals from the Central African Armed Forces were followed from 1995 to 2000. Viruses were isolated from 17 patients at various time points after seroconversion and their coreceptor usage was examined using GHOST cells expressing CD4 and one of the HIV-1 chemokine coreceptors CCR5, CXCR4, BOB/GPR15, and Bonzo/STRL33/CXCR6. Eleven patients died from AIDS. Eight of them died between 2 and 5 years after seroconversion, after a brief symptomatic stage. Patients who rapidly progressed to AIDS and death displayed the highest viral loads after seroconversion. All isolates obtained soon after seroconversion used CCR5, albeit, in some cases, CXCR4, BOB, or Bonzo were also used. Most isolates remained R5 (59 out of 61 isolates), although viruses using CXCR4 appeared in some cases of progression to AIDS. In several cases, a broad tropism was observed during the course of infection, with a frequent usage of BOB and Bonzo in addition to CCR5. Rapid progression to disease and short survival time among Central African HIV-1 patients appear more frequent than those reported in industrialized countries. Viral coreceptor used was mainly CCR5, but, interestingly, a large part of isolates also used BOB and Bonzo. However, there was no strict correlation between the clinical outcome and extended viral tropism.

Rapid diagnosis of diarrhea caused by Shigella sonnei using dipsticks; comparison of rectal swabs, direct stool and stool culture.

BACKGROUND: We evaluated a dipstick test for rapid detection of Shigella sonnei on bacterial colonies, directly on stools and from rectal swabs because in actual field situations, most pathologic specimens for diagnosis correspond to stool samples or rectal swabs. METHODOLOGY/PRINCIPAL FINDINGS: The test is based on the detection of S. sonnei lipopolysaccharide (LPS) O-side chains using phase I-specific monoclonal antibodies coupled to gold particles, and displayed on a one-step immunochromatographic dipstick. A concentration as low as 5 ng/ml of LPS was detected in distilled water and in reconstituted stools in 6 minutes. This is the optimal time for lecture to avoid errors of interpretation. In distilled water and in reconstituted stools, an unequivocal positive reaction was obtained with 4 x 10(6) CFU/ml of S. sonnei. The specificity was 100% when tested with a battery of Shigella and different unrelated strains. When tested on 342 rectal swabs in Chile, specificity (281/295) was 95.3% (95% CI: 92.9% - 97.7%) and sensitivity (47/47) was 100%. Stool cultures and the immunochromatographic test showed concordant results in 95.5 % of cases (328/342) in comparative studies. Positive and negative predictive values were 77% (95% CI: 65% - 86.5%) and 100% respectively. When tested on 219 stools in Chile, Vietnam, India and France, specificity (190/198) was 96% (95% CI 92%-98%) and sensitivity (21/21) was 100%. Stool cultures and the immunochromatographic test showed concordant results in 96.3 % of cases (211/219) in comparative studies. Positive and negative predictive values were 72.4% (95% CI 56.1%-88.6%) and 100 %, respectively. CONCLUSION: This one-step dipstick test performed well for diagnosis of S. sonnei both on stools and on rectal swabs. These data confirm a preliminary study done in Chile.

No evidence of prolonged enterovirus excretion in HIV-seropositive patients.

Mutations frequently occur in oral poliovirus vaccine (OPV) strains upon replication in the human intestine. These strains occasionally revert to being neurovirulent. The more prolonged the excretion of OPV, the higher the risk of reversion. OPV strains can be secreted for several months in humans presenting humoral immune system deficiencies. The duration of excretion of OPV strains or other enteroviruses in individuals infected with the human immunodeficiency virus (HIV) is unknown. We investigated whether HIV infection, which is very prevalent in the Central African Republic, causes prolonged excretion of enteroviruses and, in particular, of OPV strains in adults. We studied 28 HIV-infected adults living with children who were immunized with OPV during national immunization days (NIDs). Blood samples were collected to confirm HIV status and to evaluate immunodeficiency before the NIDs. Stool samples for enterovirus isolation were also collected before the NIDs, between the two rounds of immunization and 2, 4 and 6 months after the second round of immunization. No poliovirus was isolated from any stool sample. Eight enteroviruses were isolated from eight adults (maximum one strain per patient). Enteroviruses were not more frequently isolated from severely immunodeficient patients. Thus, HIV-infected adults do not appear to be at high risk of infection with OPV strains and the excretion of enteroviruses (and thus of polioviruses) does not seem to be prolonged in HIV-infected adults.

Specific antibody production by blood B cells is retained in late stage drug-naïve HIV-infected Africans.

Unseparated peripheral blood mononuclear cells (PBMCs) obtained from drug-naïve African individuals living in a context of multi-infections and presenting with high viral load (VL), were cultured in vitro and tested for their ability to produce antibodies (Abs) reacting with HIV-1 antigens. Within these PBMCs, circulating B cells were differentiated in vitro and produced IgG Abs against not only ENV, but also GAG and POL proteins. Under similar experimental conditions, HAART treated patients produced Abs to ENV proteins only. The in vitro antibody production by drug-naïve individuals' PBMCs depended on exogenous cytokines (IL-2 and IL-10) but neither on the re-stimulation of reactive cells in cultures by purified HIV-1-gp160 antigen nor on the re-engagement of CD40 surface molecules. Further, it was not abrogated by the addition of various monoclonal Abs (mAbs) to co-stimulatory molecules. This suggests that the in vitro antibody production by drug-naïve individuals' PBMCs resulted from the maturation of already envelope and core antigen-primed, differentiated B cells, presumably pre-plasma cells, which are not known to circulate at homeostasy. As in vitro produced Abs retained the capacity of binding antigen and forming complexes, this study provides pre-clinical support for functional humoral responses despite major HIV- and other tropical pathogen-induced B cell perturbations.

Identification of germinal center B cells in blood from HIV-infected drug-naive individuals in Central Africa.

To better understand the pathophysiology of B cell populations-the precursors of antibody secreting cells-during chronic human immunodeficiency virus (HIV) infection, we examined the phenotype of circulating B cells in newly diagnosed Africans. We found that all African individuals displayed low levels of naive B cells and of memory-type CD27+ B cells, and high levels of differentiated B cells. On the other hand, HIV-infected African patients had a population of germinal center B cells (i.e. CD20+, sIgM-, sIgD+, CD77+, CD138(+/-)), which are generally restricted to lymph nodes and do not circulate unless the lymph node architecture is altered. The first observations could be linked to the tropical environment whereas the presence of germinal center B cells may be attributable to chronic exposure to HIV as it is not observed in HIV-negative African controls and HAART treated HIV-infected Europeans. It may impact the management of HIV infection in countries with limited access to HIV drugs and urges consideration for implementation of therapeutic vaccines.