Microbiological, clinical and molecular findings of non-typhoidal Salmonella bloodstream infections associated with malaria, Oriental Province, Democratic Republic of the Congo

Abstract

Background: In sub-Saharan Africa, non-typhoidal Salmonella (NTS) can cause bloodstream infections, referred to as invasive non-typhoidal Salmonella disease (iNTS disease); it can occur in outbreaks and is often preceded by malaria. Data from Central Africa is limited.

Methods: Clinical, microbiological and molecular findings of NTS recovered in a blood culture surveillance project (2009-2014) were analyzed.

Results: In March-July 2012 there was an epidemic increase in malaria infections in the Oriental Province of the Democratic Republic of the Congo (DRC). In one referral hospital, overall hospital admissions in June 2012 were 2.6 times higher as compared to the same period in the years before and after (336 versus an average of 128 respectively); numbers of malaria cases and blood transfusions were nearly three- and five-fold higher respectively (317 versus 112 and 250 versus 55). Case fatality rates (in-hospital deaths versus all admissions) peaked at 14.6 %. Salmonella Typhimurium and Salmonella Enteritidis together accounted for 88.9 % of pathogens isolated from blood cultures collected during an outreach visit to the affected districts in June 2012. Children infected with Salmonella Enteritidis (33 patient files available) tended to be co-infected with Plasmodium falciparum more often than children infected with Salmonella Typhimurium (40 patients files available) (81.8 % versus 62.5 %). Through the microbiological surveillance project (May 2009-May 2014) 113 unique NTS isolates were collected (28.5 % (113/396) of pathogens); most (95.3 %) were recovered from children < 15 years. Salmonella Typhimurium (n = 54) and Salmonella Enteritidis (n = 56) accounted for 47.8 % and of 49.6 % NTS isolates respectively. Multilocus variable-number tandem-repeat analysis (MLVA) revealed more heterogeneity for Salmonella Typhimurium than for Salmonella Enteritidis. Most (82/96, 85.4 %) NTS isolates that were available for antibiotic susceptibility testing were multidrug resistant. All isolates were susceptible to ceftriaxone and azithromycin.

Conclusion: During the peak of an epidemic increase in malaria in the DRC in 2012, a high proportion of multidrug resistant Salmonella Typhimurium and Salmonella Enteritidis were isolated from blood cultures. Overall, the two serovars showed subtle differences in clinical presentation and genetic diversity.

Keywords: Antibiotic; Bloodstream infections; Children; Democratic Republic of the Congo; Malaria; Molecular typing; Salmonella; Symptoms.

Fig. 1

Map of DRC with the three places recently affected by a microbiologically documented (epidemic) increase in Salmonella infections (i) Kisantu [15]; (ii) Bwamanda [16]; (iii) districts of Bas-Uélé and Haut-Uélé (present report). © Institute of Tropical Medicine, Antwerp

Fig. 2

The four health zones affected by the iNTS disease outbreak in 2012: Wamba and Isiro (Haut-Uélé) and Pawa and Poko (Bas-Uélé). © Institute of Tropical Medicine, Antwerp

Fig. 3

Hospital admissions, malaria cases, blood transfusions and case-fatality rates (2011–2013) for a Pawa Health Zone Referral Hospital; b Wamba Health Zone Referral Hospital; c Poko Health Zone Referral Hospital; d Isiro Health Zone Referral Hospital. HGR = General Referal Hospital

Fig. 4

Rainfall in the Oriental Province, DRC (2011–2013). Peak months of the outbreak were April 2012 to June 2012