# Effect of the incubation time on blood culture results and bacterial pathogens causing bloodstream infections among children attending Sekou Toure Regional Referral Hospital in Mwanza, Tanzania

## TL;DR

This study shows that performing blind subculture after 8 hours of incubation can quickly detect over half of bloodstream infections in children, improving timely treatment.

## Contribution

The study introduces an optimized blood culture method using early blind subculture to reduce diagnostic delays in children with bloodstream infections.

## Key findings

- Blind subculture after 8 hours detected 51.1% of bloodstream infections in children.
- Klebsiella pneumoniae and Staphylococcus aureus were the most common pathogens.
- Over 60% of Gram-negative bacteria showed resistance to third-generation cephalosporin.

## Abstract

Background. A one hour delay in initiating appropriate antimicrobial treatment increases the mortality rate of patients with bloodstream infections by 2%. This highlights the risk associated with manual blood culture methods, as they tend to have long turnaround time, with an initial incubation period of 18–24 h, leading to delays in obtaining diagnostic results. This study examined the impact of incubation time on blood culture results and analysed the patterns of the pathogens causing bloodstream infections (BSIs) among children attending Sekou Toure Regional Referral Hospital (SRRH), Mwanza, Tanzania

Methodology. A hospital-based, descriptive cross-sectional study was conducted at SRRH from May to July 2024. The conventional blood culture method, using in-house prepared brain heart infusion broth with slight modifications on the initial time of the blind subculture (at 8, 24 and 120 h) was done to isolate the pathogens causing BSIs. Descriptive data analysis was performed using STATA software version 15.

Results. The study enrolled 302 children with clinical diagnosis of BSIs. Of these, 160 (53%) were male, with a median age of 6 years interquartile range [IQR] 1–7 years. Fever was the predominant clinical sign reported in 259 (85.8%) children. Microbiologically confirmed BSIs were detected in 90 (29.8%) children. Among them, 51.1% (46/90) were detected through blind subculture after 8 h of initial incubation. An additional 31 (34.4%) and 13 (14.4%) were detected after 24 h and 120 h of incubation, respectively. The most frequently isolated pathogens were Klebsiella pneumoniae (25.6%, 23/90) and Staphylococcus aureus (24.4%, 22/90). Gram-negative bacteria (GNB) formed the majority (71.1%, 64/90) of the isolated pathogens, with 62.5% (40/64) showing resistance to third-generation cephalosporin (3GC). Additionally, 45.5% (10/22) of the S. aureus strains were methicillin-resistant S. aureus.

Conclusion. Blind subculture after 8 h of initial incubation correctly detected more than half of the children with microbiologically confirmed BSIs. Incorporating blind subculture on MacConkey agar supplemented with 2 µg ml−1 cefotaxime (MCA-C) after 8 h of incubation resulted in the correct treatment of half of the children with BSIs caused by GNB within 24 h. In areas with high prevalence of 3GC resistance, blind subculture within 8 h should include MCA-C for appropriate treatment within 24 h.