A prospective study of bloodstream infections as cause of fever in Malawi: clinical predictors and implications for management

Abstract

Objective: To determine the contribution of a blood culture service to the diagnosis of fever in a resource-poor setting and to identify clinical predictors of specific bloodstream infections (BSI).

Methods: In a descriptive, prospective study at the Medical Wards at Queen Elizabeth Central Hospital, Blantyre, Malawi, we tried to identify a specific cause of fever in febrile patients, comparing the use of routinely available diagnostic methods with the same methods plus blood culture. Clinical predictors of specific BSIs were sought.

Results: A total of 352 patients admitted with fever (axillary temperature > or =37.4 degrees C) or a history of fever within the last 4 days were enrolled. Tuberculosis (TB) was the diagnosis most commonly suspected initially on clinical grounds (28%), followed by lower respiratory tract infection (16%), malaria (12%) and gastroenteritis (5%). Blood cultures were positive in 128 patients (36%); Mycobacterium tuberculosis was the most commonly isolated organism (57 patients). In most cases the diagnosis of TB had already been made using routinely available diagnostic methods, including chest radiography. In all 16 cases of Streptococcus pneumoniae bacteraemia, infection with this agent was clinically suspected, usually on the basis of pulmonary symptoms and signs. In contrast, in 30 of 65 patients (65%) with non-typhi salmonellae (NTS) bacteraemia, there were no symptoms or signs specifically suggestive of this diagnosis. Fever > or =39 degrees C and splenomegaly predicted NTS bacteraemia with an odds ratio of 8.4 (95% confidence interval 3.4-20.6, P < 0.001).

Conclusion: BSIs are common among patients admitted with fever. While BSI with mycobacteraemia and S. pneumoniae can usually be predicted on clinical grounds and with routinely available diagnostic methods, NTS bacteraemia often presents as a primary BSI without localizing symptoms and signs. Splenomegaly in this population indicates NTS bacteraemia rather than malaria.