Jean-François Carod

Evaluation of the performance of four rapid tests for detection of hepatitis B surface antigen in Antananarivo, Madagascar

Four rapid immunochromatographic assays--Determine HBsAg, Virucheck HBsAg, Cypress HBsAg Dipstick and Hexagon HBsAg--for human hepatitis B surface antigen (HBsAg) detection in human serum were evaluated. A collection of reference serum samples (91 HBsAg positive and 109 HBsAg negative) stored at -80 degrees C was used. Sensitivity and positive predictive value (PPV) exceeded 95%, and specificity and negative predictive value (NPV) exceeded 96% for all tests. The Determine HBsAg test performed best in this study, with a sensitivity of 97.8%, a specificity and PPV of 100%, a NPV of 98.2% and an accuracy rate of 99.0%. However, the differences between the tests were not significant. Other factors should therefore also be taken into account by the Ministry of Health in its decision to recommend a particular test: price, availability, delivery time and feasibility of whole-blood testing. The Determine test appears to be the most suitable for Madagascar, based on all these criteria. The use of this test, despite its lower sensitivity, could prevent blood-borne transmission of hepatitis B virus (HBV) in areas with limited resources.

Role of contaminated aspiration tubes in nosocomial outbreak of Klebsiella pneumoniae producing SHV-2 and CTX-M-15 extended-spectrum β-lactamases

Klebsiella pneumoniae resistant to ceftazidime was isolated from ten neonates hospitalised between February and March 2006 in two Antananarivo hospitals, Madagascar. The main environmental source, for one hospital in particular, was the liquid used to rinse aspiration tubes in the paediatric wards. The risk of contamination from aspiration tubes is very high in the hospitals of Antananarivo since tap water used to rinse the tubes is not regularly changed. Phenotypical (biotyping and antibiotyping) and genotypical (pulsed-field gel electrophoresis) analysis of all the clinical isolates indicated that nine cases were due to a single clone. This clone carried the genes encoding SHV-2 and CTX-M-15 beta-lactamases. This is the first description of an epidemic due to an ESBL-producing member of the family Enterobacteriaceae in Malagasy hospitals.

Dissemination of multidrug resistant Acinetobacter baumannii in various hospitals of Antananarivo Madagascar

This study reports the dissemination of multidrug-resistant (MDR) OXA-23-producing Acinetobacter baumannii clones in hospitals in Antananarivo, Madagascar. A total of 53 carbapenem-resistant A. baumannii isolates were obtained from September 2006 to March 2009 in five hospitals. These resistant strains represent 44% of all A. baumannii isolates. The double disk synergy test was performed to screen for production of metallo-beta-lactamases. Polymerase chain reaction (PCR) and DNA sequencing were performed for the detection of bla(AmpC), bla(OXA-51),bla(OXA-23), bla(OXA-24), bla(IMP), bla(VIM). The presence of the insertion sequence ISAba1 relative to bla OXA-23 and bla OXA-51 was assessed by PCR. Isolates were typed by Rep-PCR. All the isolates were MDR and produced the OXA-23 carbapenemase, which was confirmed by sequencing. PCR analysis for AmpC and OXA-51 gave positive results for all strains studied. No isolates produced metallo-beta-lactamases. In all isolates ISAba1 laid upstream of bla OXA-23. The A. baumannii isolates were separated into two genotypes; genotype A had a higher prevalence (41 strains) than genotype B (12 strains). Genotype A was present in four hospitals, whilst genotype B had spread in two hospitals. The high frequency of MDR OXA-23-producing A. baumannii in various hospitals in Antananarivo is curious since carbapenems are not available in Madagascar, but it emphasises the need for infection control procedures and strict adherence to them to prevent the spread of these resistant organisms in Antananarivo and also the need to control the use of carbapenems in the future.

In vitro activities of 18 antimicrobial agents against Staphylococcus aureus isolates from the Institut Pasteur of Madagascar

BackgroundStaphylococcus aureus, one of the most frequently isolated pathogens in both hospitals and the community, has been particularly efficient at developing resistance to antimicrobial agents. In developed countries, as methicillin-resistant S. aureus (MRSA) has prevailed and, furthermore, as S. aureus with reduced susceptibility to vancomycin has emerged, the therapeutic options for the treatment of S. aureus infections have become limited. In developing countries and especially African countries very little is known concerning the resistance of S. aureus to antibiotics. In Madagascar no data exist concerning this resistance.ObjectiveTo update the current status of antibiotic resistance of S. aureus in Antananarivo, Madagascar.MethodsClinical S. aureus isolates were collected from patients at the Institut Pasteur of Madagascar from January 2001 to December 2005. Susceptibility tests with 18 antibiotics were performed by the disk diffusion method.ResultsAmong a total of 574 isolates, 506 were from community-acquired infections and 68 from nosocomial infections. There was no significant difference in the methicillin resistance rate between community-acquired strains (33 of 506; 6.5%) and nosocomial strains (3 of 68, 4.4%). Many MRSA isolates were resistant to multiple classes of antibiotics. Resistance to tetracyclin, trimethoprim-sulfamethoxazole and erythromycin was more common. Among MRSA isolates resistance rates to rifampicin, fusidic acid, gentamicin and ciprofloxacin were lower than that observed with other drugs easily available in Madagascar. No isolates were resistant to glycopeptides.ConclusionThe rate of methicillin-resistant S. aureus is not different between community-acquired and nosocomial infections and is still rather low in Madagascar.

The pig tapeworm Taenia solium, the cause of cysticercosis: biogeographic (temporal and spacial) origins in Madagascar.

Cysticercosis is a serious public health problem in Madagascar. The prevalence rate of active cysticercosis reached 21% in regions with a high level of livestock farming. Taenia solium of African-American and Asian genotypes are both present on the island. The times of divergence of the 13 specimens studied suggests a very ancient diversification of T. solium. These events are widely thought to be prior to the domestication of pigs, and seem to follow the expansion of Homo in Asia. Multiple human migrations and the diversity of potential intermediate hosts may have led to a complex epidemiological situation on the island.

Comparison of ELISA and PCR assays for the diagnosis of porcine cysticercosis.

Cysticercosis is a zoonotic disease due to Taenia solium, which involves porcines as intermediate host. It is endemic in Madagascar, however minimal data has been reported concerning porcine cysticercosis prevalence. Lack of ante-mortem diagnostic tools renders the evaluation of its prevalence difficult. Tongue palpation is specific but has poor sensitivity. Serological tests detecting antigens or antibodies are sensitive to human cysticercosis and apt for diagnosis but are not yet considered as a gold standard in porcine ante-mortem examination. PCR are widely used to detect pathogens but also poorly evaluated in regards to the diagnosis of cysticercosis. We compare the performance of PCR and ELISA assays on 67 pig serums: 22 from cysticercosis positive pigs (meat inspection) and 45 from cysticercosis negative animals (originating from a non-endemic country or grown in industrial and well isolated pigsties). Among the negative samples 19 were collected from pigs with trichinellosis and 4 from pigs with toxoplasmosis. Results indicate that ELISA assay showed high sensitivity and good specificity while the PCR assays showed high specificity but a low sensitivity.

Evaluation of the performance of 5 commercialized enzyme immunoassays for the detection of Taenia solium antibodies and for the diagnosis of neurocysticercosis

This study aimed to evaluate 5 enzyme immunoassays for detecting human antibodies against Taenia solium in human serum and for the diagnosis of neurocysticercosis (NCC): DRG™, RIDASCREEN™, NOVATECH™, CYPRESS™, and IVD™. A collection of 114 reference serum samples were used. All sera were tested both by ELISA and by an immunoblot method (enzyme-linked immunoelectrotransfer blot [EITB]). When compared with EITB, the Ridascreen™ test had the best positive concordance rate (85.1-91.2%) and the NovaLisa test™ showed the optimal negative concordance rate (93.7-95.6%). All tests had a sensitivity under 72% and a specificity above 60%. The best sensitivity was obtained using Ridascreen™ test (71.4%). An optimal specificity was achieved by the NovaLisa test™. T. solium-positive sera all cross-reacted with E. granulosus positive samples. In the commercial assays evaluated here, the most appropriate ELISA test for screening may be the Ridascreen™ assay. Antibody detection seems to be not appropriate for NCC diagnosis because of its overall lack of sensitivity.

Genetics of the pig tapeworm in madagascar reveal a history of human dispersal and colonization.

An intricate history of human dispersal and geographic colonization has strongly affected the distribution of human pathogens. The pig tapeworm Taenia solium occurs throughout the world as the causative agent of cysticercosis, one of the most serious neglected tropical diseases. Discrete genetic lineages of T. solium in Asia and Africa/Latin America are geographically disjunct; only in Madagascar are they sympatric. Linguistic, archaeological and genetic evidence has indicated that the people in Madagascar have mixed ancestry from Island Southeast Asia and East Africa. Hence, anthropogenic introduction of the tapeworm from Southeast Asia and Africa had been postulated. This study shows that the major mitochondrial haplotype of T. solium in Madagascar is closely related to those from the Indian Subcontinent. Parasitological evidence presented here, and human genetics previously reported, support the hypothesis of an Indian influence on Malagasy culture coinciding with periods of early human migration onto the island. We also found evidence of nuclear-mitochondrial discordance in single tapeworms, indicating unexpected cross-fertilization between the two lineages of T. solium. Analyses of genetic and geographic populations of T. solium in Madagascar will shed light on apparently rapid evolution of this organism driven by recent (<2,000 yr) human migrations, following tens of thousands of years of geographic isolation.

Age-specific seroprevalence of hepatitis A in Antananarivo (Madagascar)

BackgroundHepatitis A virus (HAV) is an enteric, viral, infectious disease endemic in many developing countries such as Madagascar. Infection is often subclinical or asymptomatic in children; however, symptomatic acute infections become more common with increasing age. In some developing countries, improvements in living conditions have led to changes in the epidemiological pattern of HAV infection. There are very few reports on the prevalence of HAV in Madagascar.This study was to determine the seroprevalence of hepatitis A virus antibodies in relation to age in the city of Antananarivo, Madagascar.MethodsSerum samples collected in 2004 during a cross-sectional survey of individuals aged between two and 24 years from Antananarivo were tested for anti-HAV antibody using a commercial enzyme immunoassay kit. Subjects were investigated using a standardized social and medical history questionnaire.Results926 subjects were enrolled including 406 males and 520 females. There were 251 children under 10 years old and 675 subjects between 10 and 24 years old. Of the 926 serum samples tested, 854 (92.2%) were positive for anti-HAV antibodies. The number of seropositive samples was similar for males and females. The overall seroprevalence was 83.7% (210/251) for children under 10 years old and 95.5% (644/675) for subjects aged between 10 and 24 years (p < 0.001).ConclusionDespite improvements in sanitary conditions and hygiene over the last few years, the prevalence of HAV in Antananarivo is high. Only children under five years old remain susceptible to HAV infection. Immunization against HAV is not needed at the present time in the Madagascan population, but should be recommended for travellers.

Population Genetic Structure and Isolation by Distance of Helicobacter pylori in Senegal and Madagascar

Helicobacter pylori has probably infected the human stomach since our origins and subsequently diversified in parallel with their human hosts. The genetic population history of H. pylori can therefore be used as a marker for human migration. We analysed seven housekeeping gene sequences of H. pylori strains isolated from 78 Senegalese and 24 Malagasy patients and compared them with the sequences of strains from other geographical locations. H. pylori from Senegal and Madagascar can be placed in the previously described HpAfrica1 genetic population, subpopulations hspWAfrica and hspSAfrica, respectively. These 2 subpopulations correspond to the distribution of Niger-Congo speakers in West and most of subequatorial Africa (due to Bantu migrations), respectively. H. pylori appears as a single population in Senegal, indicating a long common history between ethnicities as well as frequent local admixtures. The lack of differentiation between these isolates and an increasing genetic differentiation with geographical distance between sampling locations in Africa was evidence for genetic isolation by distance. The Austronesian expansion that started from Taiwan 5000 years ago dispersed one of the 10 subgroups of the Austronesian language family via insular Southeast Asia into the Pacific and Madagascar, and hspMaori is a marker for the entire Austronesian expansion. Strain competition and replacement of hspMaori by hpAfrica1 strains from Bantu migrants are the probable reasons for the presence of hspSAfrica strains in Malagasy of Southeast Asian descent. hpAfrica1 strains appear to be generalist strains that have the necessary genetic diversity to efficiently colonise a wide host spectrum.