Characterisation of community acquired non-typhoidal Salmonella from bacteraemia and diarrhoeal infections in children admitted to hospital in Nairobi, Kenya

Abstract

Background: In sub-Saharan Africa community-acquired non-typhoidal Salmonella (NTS) is a major cause of high morbidity and death among children under 5 years of age especially from resource poor settings. The emergence of multidrug resistance is a major challenge in treatment of life threatening invasive NTS infections in these settings.

Results: Overall 170 (51.2%) of children presented with bacteraemia alone, 28 (8.4%) with gastroenteritis and bacteraemia and 134 (40.4%) with gastroenteritis alone. NTS serotypes obtained from all the cases included S. Typhimurium (196; 59%), S. Enteritidis (94; 28.3%) and other serotypes in smaller numbers (42; 12.7%); distribution of these serotypes among cases with bacteremia or gastroenteritis was not significantly different. A significantly higher proportion of younger children (< 3 years of age) and those from the slums presented with invasive NTS compared to older children and those from upper socio-economic groups (p < 0.001). One hundred and forty-seven (44.3%) NTS were resistant to 3 or more antibiotics, and out of these 59% were resistant to ampicillin, chloramphenicol and tetracycline. There was no significant difference in antibiotic resistance between the two serotypes, S. Typhimurium and S. Enteritidis. Ceftriaxone and ciprofloxacin were the only antibiotics tested to which all the NTS were fully susceptible. Using Pulsed Field Gel Electrophoresis (PFGE) there were 3 main patterns of S. Typhimurium and 2 main patterns of S. Enteritidis among cases of bacteraemia and gastroenteritis.

Conclusion: Serotype distribution, antibiotic susceptibility and PFGE patterns of NTS causing bacteraemia and gastroenteritis did not differ significantly. The high prevalence of NTS strains resistant to most of the commonly used antimicrobials is of major public health concern.

Figure 1

Number of NTS isolates from children by month. A higher number of isolations occurred during the rainy season in May and June compared to the rest of the year (p < 0.001).

Figure 2

Clinical presentation of NTS infection according to age group. More children under the age of 3 years tended to get invasive disease compared to older children (over 3 years) who had a higher proportion with gastroenteritis.

Figure 3

Representative PFGE patterns of XbaI-digested S. Typhimurium from cases from children with bacteraemia. Lane M, 50 kb molecular size standard; Lanes 1 to 9, S. Typhimurium from PFGE pattern 1; Lanes 10 and 11, S. Typhimurium from PFGE pattern 2; Lane 12 S. Typhimurium from PFGE pattern 3. Using either of the two enzymes, XbaI or SpeI, PFGE patterns of the isolates were within 1–3 band differences.

Figure 4

Representative PFGE patterns of XbaI-digested S. Enteritidis from cases from children with bacteraemia. Lane M, 50 kb molecular size standard. Lanes 1 and 2, S. Enteritidis from PFGE pattern 1; Lanes 3 and 4, S. Enteritidis from PFGE pattern 2.