Intestinal carriage of invasive non-typhoidal Salmonella among household members of children with Salmonella bloodstream infection, Kisangani, DR Congo.

Introduction: Invasive non-typhoidal Salmonella (iNTS), mainly Salmonella Typhimurium and Salmonella Enteritidis, causes a severe burden in sub-Saharan Africa; however, its reservoir (animal or environmental) is unclear. The present study assessed healthy household members of index patients for intestinal carriage of Salmonella. Methods: Index patients were admitted to the University Hospital of Kisangani (DR Congo), and Salmonella was grown from blood cultures. Household members were asked to provide three stool samples for culture for Salmonella. Salmonella Typhimurium and S. Enteritidis isolates from index patients, and household members were assessed for genetic relatedness using the multiple-locus variable number of tandem repeat analysis (MLVA), and the multilocus sequence type (ST) was determined by whole genome sequencing. Results: Between May 2016 and January 2020, 22 households were visited. The index patient serotypes were Typhimurium, Enteritidis, Typhi, and Paratyphi C; II:42:r:-; and I:7:y:- (n = 8, 7, 5, and each 1, respectively). The median (range) delay between the index patient and household sampling was 25 days (2 days to 7.3 months); 203 household members provided at least one stool sample. In all, 15 (7.3%) Salmonella carriers were found in nine of 22 households. For one index patient, the household comprised S. Typhimurium in four household members, including the index patient, sampled 27 days after bloodstream infection; the MLVA types of these five isolates were similar. They belonged to ST313 lineage 2 and were closely related [0-1 allelic distance (AD) among the stool isolates and eight AD with the blood culture isolate]. In another household, the stool culture of the index patient (obtained 67 days after bloodstream infection) grew S. Enteritidis of the same MLVA type; both isolates belonged to the ST11 Central/Eastern African clade and were closely related (three AD). Discussion: The present study provides evidence of household clustering of S. Typhimurium ST313 and intestinal carriage of iNTS several weeks after bloodstream infection.

Urban rats as carriers of invasive Salmonella Typhimurium sequence type 313, Kisangani, Democratic Republic of Congo.

BACKGROUND: Invasive non-typhoidal Salmonella (iNTS-mainly serotypes Enteritidis and Typhimurium) are major causes of bloodstream infections in children in sub-Saharan Africa, but their reservoir remains unknown. We assessed iNTS carriage in rats in an urban setting endemic for iNTS carriage and compared genetic profiles of iNTS from rats with those isolated from humans. METHODOLOGY/PRINCIPAL FINDINGS: From April 2016 to December 2018, rats were trapped in five marketplaces and a slaughterhouse in Kisangani, Democratic Republic of the Congo. After euthanasia, blood, liver, spleen, and rectal content were cultured for Salmonella. Genetic relatedness between iNTS from rats and humans-obtained from blood cultures at Kisangani University Hospital-was assessed with multilocus variable-number tandem repeat (VNTR) analysis (MLVA), multilocus sequence typing (MLST) and core-genome MLST (cgMLST). 1650 live-capture traps yielded 566 (34.3%) rats (95.6% Rattus norvegicus, 4.4% Rattus rattus); 46 (8.1%) of them carried Salmonella, of which 13 had more than one serotype. The most common serotypes were II.42:r:- (n = 18 rats), Kapemba (n = 12), Weltevreden and Typhimurium (n = 10, each), and Dublin (n = 8). Salmonella Typhimurium belonged to MLST ST19 (n = 7 rats) and the invasive ST313 (n = 3, isolated from deep organs but not from rectal content). Sixteen human S. Typhimurium isolates (all ST313) were available for comparison: MLVA and cgMLST revealed two distinct rat-human clusters involving both six human isolates, respectively, i.e. in total 12/16 human ST313 isolates. All ST313 Typhimurium isolates from rats and humans clustered with the ST313 Lineage 2 isolates and most were multidrug resistant; the remaining isolates from rats including S. Typhimurium ST19 were pan-susceptible. CONCLUSION: The present study provides evidence of urban rats as potential reservoirs of S. Typhimurium ST313 in an iNTS endemic area in sub-Saharan Africa.

The diagnosis of typhoid fever in the Democratic Republic of the Congo.

The diagnosis of typhoid fever (TF) in Kinshasa (DR Congo) was assessed by on-site surveys, external quality assessment (EQA) of the Widal test and a microbiological blood culture surveillance study. In 331/536 (61.8%) health facilities, clinicians diagnosed TF by clinical picture and the Widal test. An EQA on the Widal test consisting of three samples revealed correct scores by respectively 27.1%, 65.6% and 3.1% of 125 participating laboratories. Most (80.9% of 152 laboratories) performed <100 Widal tests per month, with a median sample positivity rate of 32.6% (range 0-90.7%). The Widal test was mostly performed on a single sample and by slide agglutination (89.5% and 97.0% respectively); errors in cold chain and procedures were recorded (not making serial dilutions, estimating titres by the intensity of agglutination). Among 293 prescribers, 52.2% and 40.8% requested the Widal test for treatment follow-up and detection of chronic carriers respectively. Salmonella Typhi was recovered from the blood in 2.4% of 3820 patients suspected as having TF, with non-typhoid Salmonellae and other Enterobacteriaceae accounting for the majority of organisms. In conclusion, clinicians rely highly on the Widal test for the diagnosis of TF and the Widal test is poorly performed and interpreted.