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Etude de la contribution des salmonelles aviaires aux salmonelloses humaines au Tchad : Cas de la ville capitale, N'Djamena

Abstract : Salmonella are linked to many food-borne diseases worldwide. They are also considered to be one of the main pathogens causing human gastroenteritis. The main objective of this study was to update the prevalence and antimicrobial resistance characteristics of Salmonella isolated from poultry and from humans experiencing gastroenteritis in N'Djamena, Chad. The results collected during this study provide the first baseline data on the prevalence of contamination by Salmonella in humans suffering from diarrhoea, as well as in laying hens and broiler chicken farms in N'Djamena. Samples were collected on one hand from five hospitals another and on another hand from sixteen poultry farms, both over two periods of six months each: from August 2010 to January 2011 and from September 2011 to February 2012. Diagnostic methods carried out during this study led to the isolation of one hundred and thirty nine Salmonella strains, belonging to forty two different serotypes. Salmonella Colindale was the most prevalent serovar (13.6 % of the isolates belonged to this serovar), followed by Salmonella Minnesota (10.8 %), Salmonella Stanleyville (5.8 %), Salmonella Havana and Kottbus (5 % each), Salmonella Idikan (4.3 %), Salmonella Riggil and Anatum (3.6 % each). Other serotypes were under-represented. The majority of these isolates were susceptible to all antibiotics tested (CLSI Standards), except some Salmonella Colindale avian isolates that exhibited a decreased susceptibility to nalidixic acid, ofloxacin and enrofloxacin, two S. Enteritidis human isolates resistant to nalidixic acid, ofloxacin and ciprofloxacin, a S. Limete avian isolate resistant to three antibiotics and 15 S. Minnesota avian isolates resistant to five different antimicrobial classes. In order to evaluate the phylogenetic relationships and to find epidemiological links between human and avian strains isolated in the same period of time and in the same region, a total of 139 Salmonella isolates found in humans and poultry in this study were characterised by ERIC-PCR and IS200-PCR. The PCR analysis was followed by macrorestriction analysis (PFGE) of genomic DNA from 22 common isolates of Salmonella serotypes encountered in both humans and poultry with XbaI enzyme. PCR results demonstrated that, in the context of this epidemiological study, ERIC- and IS200-PCR methods can be used effectively to limit the number of isolates that have to be serotyped. The comparison of ERIC-PCR, IS200-PCR, PFGE and antimicrobial susceptibility profiles among isolates from human and avian origins has highlighted, on one hand, the indirect evidence of human contamination sources by Salmonella serovars from poultry farms, and on the other hand the diversity of sources and potential reservoirs of Salmonella strains in the N'Djamena city.
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Djim-Adjim Tabo. Etude de la contribution des salmonelles aviaires aux salmonelloses humaines au Tchad : Cas de la ville capitale, N'Djamena. Médecine humaine et pathologie. AgroParisTech, 2013. Français. ⟨NNT : 2013AGPT0059⟩. ⟨tel-03500894⟩

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