Frédérique Randrianirina

Epidemiology of methicillin-susceptible Staphylococcus aureus lineages in five major African towns: high prevalence of Panton-Valentine leukocidin genes

The epidemiology of methicillin-susceptible Staphylococcus aureus (MSSA) in Africa is poorly documented. From January 2007 to March 2008, 555 S. aureus isolates were collected from five African towns in Cameroon, Madagascar, Morocco, Niger, and Senegal; among these, 456 unique isolates were susceptible to methicillin. Approximately 50% of the MSSA isolates from each different participating centre were randomly selected for further molecular analysis. Of the 228 isolates investigated, 132 (58%) belonged to five major multilocus sequence typing (MLST) clonal complexes (CCs) (CC1, CC15, CC30, CC121 and CC152) that were not related to any successful methicillin-resistant S. aureus (MRSA) clones previously identified in the same study population. The luk-PV genes encoding Panton-Valentine leukocidin (PVL), present in 130 isolates overall (57%), were highly prevalent in isolates from Cameroon, Niger, and Senegal (West and Central Africa). This finding is of major concern, with regard to both a source of severe infections and a potential reservoir for PVL genes. This overrepresentation of PVL in MSSA could lead to the emergence and spread of successful, highly virulent PVL-positive MRSA clones, a phenomenon that has already started in Africa.

Epidemiology of methicillin-resistant Staphylococcus aureus lineages in five major African towns: emergence and spread of atypical clones.

The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in Africa is poorly documented. From January 2007 to March 2008, we collected 86 MRSA isolates from five African towns, one each in Cameroon, Madagascar, Morocco, Niger and Senegal. Although one or two major clones, defined by the sequence type and staphylococcal cassette chromosome mec type, predominated at each site, genetic diversity (ten clones) was relatively limited in view of the large geographical area studied. Most of the isolates (n = 76, 88%) belonged to three major clones, namely ST239/241-III, a well-known pandemic clone (n = 34, 40%), ST88-IV (n = 24, 28%) and ST5-IV (n = 18, 21%). The latter two clones have only been sporadically described in other parts of the world. The spread of community-associated MRSA carrying the Panton-Valentine leukocidin genes is a cause for concern, especially in Dakar and possibly throughout Africa.

High prevalence of fecal carriage of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae in a pediatric unit in Madagascar.

BackgroundExtended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have spread worldwide but there are few reports on carriage in hospitals in low-income countries. ESBL-producing Enterobacteriaceae (ESBL-PE) have been increasingly isolated from nosocomial infections in Antananarivo, Madagascar.Methodswe conducted a prevalence survey in a pediatric unit from March to April 2008 Patient rectal swabs were sampled on the first and the last day of hospitalization. Medical staff and environment were also sampled. Rectal and environmental swabs were immediately plated onto Drigalski agar supplemented with 3 mg/liter of ceftriaxon.ResultsFecal carriage was detected in 21.2% of 244 infants on admission and 57.1% of 154 on discharge, after more than 48 hours of hospitalization (p < 0.001). The species most frequently detected on admission were Escherichia coli and Klebsiella pneumoniae (36.9%), whereas, on discharge, K. pneumoniae was the species most frequently detected (52.7%). ESBL-associated resistances were related to trimethoprim-sulfamethoxazole (91.3%), gentamicin (76.1%), ciprofloxacin (50.0%), but not to amikacin and imipenem. The increased prevalence of carriage during hospitalization was related to standard antimicrobial therapy.ConclusionThe significant emergence of multidrug-resistant enteric pathogens in Malagasy hospitals poses a serious health threat requiring the implementation of surveillance and control measures for nosocomial infections.

Rectal Carriage of Extended-Spectrum Beta-Lactamase-Producing Gram-Negative Bacilli in Community Settings in Madagascar

Background Extended-spectrum ß-lactamase-producing Enterobacteria (ESBL-PE) emerged at the end of the 1980s, causing nosocomial outbreaks and/or hyperendemic situations in hospitals and long-term care facilities. In recent years, community-acquired infections due to ESBL-PE have spread worldwide, especially across developing countries including Madagascar. Objectives This study aimed to determine the prevalence and risk factors of intestinal carriage of ESBL-PE in the community of Antananarivo. Methods Non-hospitalized patients were recruited in three health centers in different socio economic settings. Fresh stool collected were immediately plated on Drigalski agar containing 3 mg/liter of ceftriaxone. Gram-negative bacilli species were identified and ESBL production was tested by a double disk diffusion (cefotaxime and ceftazidime +/− clavulanate) assay. Characterization of ESBLs were perfomed by PCR and direct sequencing . Molecular epidemiology was analysed by Rep-PCR and ERIC-PCR. Results 484 patients were screened (sex ratio  = 1.03, median age 28 years). 53 ESBL-PE were isolated from 49 patients (carrier rate 10.1%). The isolates included Escherichia coli (31), Klebsiella pneumoniae (14), Enterobacter cloacae (3), Citrobacter freundii (3), Kluyvera spp. (1) and Pantoae sp.(1). In multivariate analysis, only the socioeconomic status of the head of household was independently associated with ESBL-PE carriage, poverty being the predominant risk factor. Conclusions The prevalence of carriage of ESBL in the community of Antananarivo is one of the highest reported worldwide. This alarming spread of resistance genes should be stopped urgently by improving hygiene and streamlining the distribution and consumption of antibiotics.

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.

Case-control study of the etiology of infant diarrheal disease in 14 districts in Madagascar.

Background Acute diarrhea is a major cause of childhood morbidity and mortality worldwide. Its microbiological causes and clinico-epidemiological aspects were examined during the rainy seasons from 2008 to 2009 in 14 districts in Madagascar. Methods Stool specimens of 2196 children with acute diarrhea and 496 healthy children were collected in a community setting. Intestinal parasites were diagnosed by microscopy and bacteria by culturing methods. Rota-, astro and adenoviruses were identified using commercially available ELISA kits and rotaviruses were confirmed using reverse transcriptase polymerase chain reaction (RT-PCR). Results Intestinal microorganisms were isolated from 54.6% of diarrheal patients and 45.9% of healthy subjects (p = <0.01). The most common pathogens in diarrheic patients were intestinal parasites (36.5%). Campylobacter spp. and Rotavirus were detected in 9.7% and 6.7% of diarrheic patients. The detection rates of Entamoeba histolytica, Trichomonas intestinalis and Giardia lamblia were much greater in diarrheal patients than in non diarrheal subjects (odds ratios of 5.1, 3.2, 1.7 respectively). The abundance of other enteropathogens among the non diarrheal group may indicate prolonged excretion or limited pathogenicity. Conclusion In developing countries, where the lack of laboratory capacities is great, cross sectional studies of enteropathogens and their spatial distribution, including diarrheal and non diarrheal subjects, are interesting tools in order to advise regional policies on treatment and diarrheic patient management.

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.

Molecular characterization of multidrug-resistant extended-spectrum β-lactamase-producing Enterobacteriaceae isolated in Antananarivo, Madagascar

BackgroundWe investigated the molecular characteristics of multidrug-resistant, extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae isolated in community settings and in hospitals in Antananarivo, Madagascar.ResultsForty-nine E. coli, K. pneumoniae, K. oxytoca and E. cloacae ESBL-producing isolates were studied. In antimicrobial susceptibility analyses, many of the isolates exhibited resistance to aminoglycosides, fluoroquinolones and trimethoprim-sulfamethoxazole. Gene amplification analysis and sequencing revealed that 75.5% (n=37) of the isolates harbored blaCTX-M-15 and 38.7% (n=19) harbored blaSHV-12. The non-ESBLs resistance genes detected were blaTEM-1, blaOXA-1, aac(6′)-Ib,aac(6′)-Ib-cr, tetA, sul-1, sul-2, qnrA, qnrB and catB-3. We found dfrA and aadA gene cassettes in the class 1 integron variable regions of the isolates, and the combination of dfrA17-aadA5 to be the most prevalent. All blaCTX-M-15 positive isolates also contained the ISEcp1 insertion element. Conjugation and transformation experiments indicated that 70.3% of the antibiotic resistance genes resided on plasmids. Through a PCR based replicon typing method, plasmids carrying the blaSHV-12 or blaCTX-M-15 genes were assigned to either the IncFII replicon type or, rarely, to the HI2 replicon type. All isolates were subtyped by the rep-PCR and ERIC-PCR methods.Phylogenetic grouping and virulence genotyping of the E. coli isolates revealed that most of them belonged to group A1. One isolate assigned to group B2 harbored blaCTX-M-15 and five virulence genes (traT, fyuA, iutA, iha and sfa) and was related to the O25b-ST131 clone.ConclusionsOur results highlight the dissemination of multidrug resistant Enterobacteriaceae isolates in Antananarivo. These findings underline the need for a rational use of antibiotic and for appropriate methods of screening ESBL in routine laboratories in Antananarivo.

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.