Factors Associated with Non-typhoidal Salmonella Bacteremia versus Typhoidal Salmonella Bacteremia in Patients Presenting for Care in an Urban Diarrheal Disease Hospital in Bangladesh

Abstract

Background

Non-typhoidal Salmonella (NTS) and Salmonella enterica serovar Typhi bacteremia are the causes of significant morbidity and mortality worldwide. There is a paucity of data regarding NTS bacteremia in South Asia, a region with a high incidence of typhoidal bacteremia. We sought to determine clinical predictors and outcomes associated with NTS bacteremia compared with typhoidal bacteremia.

Methodology

We performed a retrospective age-matched case-control study of patients admitted to the Dhaka Hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh, between February 2009 and March 2013. We compared demographic, clinical, microbiological, and outcome variables of NTS bacteremic patients with age-matched S. Typhi bacteremic patients, and a separate comparison of patients with NTS bacteremia and patients with NTS gastroenteritis.

Principal Findings

Of 20 patients with NTS bacteremia, 5 died (25% case fatality), compared to none of 60 age-matched cases of S. Typhi bacteremia. In univariate analysis, we found that compared with S. Typhi bacteremia, cases of NTS bacteremia had more severe acute malnutrition (SAM) in children under five years of age, less often presented with a duration of fever ≥ 5 days, and were more likely to have co-morbidities on admission such as pneumonia and clinical signs of sepsis (p<0.05 in all cases). In multivariable logistic regression, SAM, clinical sepsis, and pneumonia were independent risk factors for NTS bacteremia compared with S. Typhi bacteremia (p<0.05 in all cases). Notably, we found marked differences in antibiotic susceptibilities, including NTS strains resistant to antibiotics commonly used for empiric therapy of patients suspected to have typhoid fever.

Conclusions/Significance

Diarrheal patients with NTS bacteremia more often presented with co-morbidities and had a higher case fatality rate compared to those with typhoidal bacteremia. Clinicians in regions where both typhoid and NTS bacteremia are prevalent need to be vigilant about the possibility of both entities, especially given notable differences in antibiotic susceptibility patterns.

Author Summary

Salmonella are a group of bacteria that cause illnesses and death worldwide. There are two types of Salmonella–Typhi and non-typhoidal (NTS). In humans, the majority of illnesses caused by NTS are related to gastro-intestinal problems, though uncommonly, it also invades the bloodstream. On the other hand, typhoid fever caused by Salmonella typhi commonly invades the bloodstream. Since the treatment of the two types may differ, we wanted to compare the risk factors for each. We studied patients who had NTS or Typhi isolated from blood in a diarrheal hospital in Bangladesh. We observed that patients with NTS bloodstream infection frequently presented with severe malnutrition, clinically diagnosed sepsis and pneumonia compared to those with typhoid fever. We also found that NTS and Typhi differed in what antibiotics they were sensitive to. These observations may help our clinicians to initiate aggressive treatment from the very beginning of the illness in children with NTS bacteremia in order to attain better outcomes.