[Sensitivity to antibiotics and genetic support to resistance of Shigella flexneri strains isolated in Dakar from 2001 to 2010]. / Sensibilité aux antibiotiques et supports génétiques de la résistance des souches de Shigella flexneri isolées à Dakar de 2001 à 2010.

Diarrheal diseases remain a leading cause of death with 14.7 million deaths in 2001 and 26% of global mortality worldwide according to WHO. Shigella species are prevalent in tropical areas; they are present all the year, with epidemic outbreaks in rainy season. Between 2001 and 2010 one hundred ninety (190) strains of Shigella flexneri isolated from National Senegalese Enterobacteriaceae Center located at the Pasteur Institute in Dakar were studied. Susceptibility was performed by antibiogram following the CASFM recommendations. Detection and characterization of integrons and resistance genes was done by PCR using specific primers and sequencing. Antibiotic susceptibility showed high percentage resistance to tetracycline: 95%, cotrimoxazole 60%, ampicillin 55%. Nineteen strains were cephalosporin resistant (10%). Two isolates were resistant to quinolones and one was imipenem resistant. Genes tet, dfr, cat, bla tem1 , bla oxa30 , bla shv , bla CTX-M , blakpc,bla IMP , gyrA, gyrB, parC and parE were detected on isolates. Integrons harbored genes resistance. The class 1 integron predominated followed by class 2 integron. Genes bla oxa30 , aadA1/aadA2 dfrA1, dfrA7 were found on class 1 integron. Class 2 integron showed three different types cassettes. No class 3 integron was detected. Genes dfrA1, dfrA7, sat, and aadA1 were harbouring by integrons. Antibiotic susceptibility showed that Shigella flexneri strains are resistant to the first line drugs used to treat shigellosis in Senegal. Resistance to 3rd generation of cephalosporins and fluoroquinolones emerged and is of great concern. These molecules must be used with caution in the treatment of shigellosis.

Genotypic Characterization of Antibiotic-Resistant Salmonella Enteritidis Isolates in Dakar; Senegal

Background: It is well established that Salmonella enterica is a major cause of food-borne disease worldwide. In Africa; according to the Who Global Salm-Surv country data bank from 2000 to 2002 Salmonella enterica serovar Enteritidis was the most common serotype involved in human salmonellosis. In Dakar this serotype of Salmonella has been reported as a frequent and an increasing cause of human infection. Methodology: The genetic determinants of the antimicrobial resistance of 25 selected multiresistant strains of Salmonella enterica serovar Enteritidis referred to the National Reference Center for Enterobacteria (NRCE) in Dakar were investigated using molecular techniques. Results: All strains carried blaTEM 1 genes. Five harboured three types of class 1 integrons with gene cassettes dfrA15; dfrA1- aadA1 and dfrA7. Multiresistance was due to a 23 Kb conjugative plasmid. DNA fingerprinting by macrorestriction of genomic DNA revealed a single related group suggesting that strains might be clonal. Conclusions: The spread of resistance genes through plasmid transfer plays an important role in the dissemination of antibiotic resistance in enteric pathogens such as Salmonella Enteritidis; the risk of transmissibility of antibiotic resistance between different bacterial strains highlights the urgent need to develop strategies to limit the spread of antimicrobial resistance among bacterial enteropathogens

Class 2 integron-associated antibiotic resistance in Shigella sonnei isolates in Dakar, Senegal.

Forty-three Shigella sonnei isolates from adult patients with diarrhoea in Dakar were analysed for the presence of integrons. Isolates were resistant to sulphamethoxazole, trimethoprim, tetracycline, streptomycin and spectinomycin. A high prevalence of class 2 integrons (93%) was found. These integrons showed three distinct structures: a class 2 integron, part of the Tn7 family and its derivatives, carrying four cassettes in the order dfrA1-sat-aadA1-orfX; a truncated class 2 integron, without orfX; and a third type ca. 4 kb in size. These class 2 integrons probably play a role in the spread of multiresistance in S. sonnei isolates. To our knowledge, this is the first description of class 2 integrons in S. sonnei isolated in sub-Saharan Africa.

Characterization of virulence factors in the newly described Salmonella enterica serotype Keurmassar emerging in Senegal (sub-Saharan Africa).

From 2000 to 2001, nine strains of Salmonella enterica belonging to the new serotype Keurmassar have been isolated from human and poultry samples at the Senegalese National Salmonella and Shigella Reference Laboratory at the Pasteur Institute, in Dakar. All strains carried virulence factors including Salmonella Pathogenicity Islands (SPI)-1, -2, -3 and -5 encoded genes. Strains did not harbour virulence plasmid. Ribotyping analysis revealed a single clone identical to Salmonella Decatur isolated in Zimbabwe. These data suggest that strains are closely related, and may have been spread clonally. In this new serotype, insertion sequence IS200 is not present.