Abstract:

Background: Blood culture remains the gold standard for the detection of pathogens causing bloodstream infections in order to guide appropriate antimicrobial therapy, with an estimated turnaround time of 72 to 120 hours. One-hour delay in initiating correct antimicrobial treatment increases the mortality rate of patients with bloodstream infections by 2%, this emphasizes the risk of relying on manual blood culture methods, where the initial incubation time for blood culture samples is 18-24 hours, causing delays in obtaining results. This study has addressed the effect of incubation time on blood culture results and the patterns of the pathogens causing bloodstream infections (BSIs) among children attending Sekou Toure Regional Referral Hospital, Mwanza, Tanzania.

Methodology: A hospital-based, descriptive cross-sectional study was conducted at Sekou Toure Regional Referral Hospital from May to July 2024. The study enrolled 302 children with clinical diagnosis of bloodstream infection and blood culture investigations collected. Demographic data, and clinical information, were collected using a structured data collection tool. 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 hours, 24 hours and 120 hours) was done to isolate the pathogens causing BSIs. The KirbyBauer disk diffusion method was used for antimicrobial susceptibility testing. Descriptive data analysis was performed using STATA software version 15.

Results: Of the enrolled children, more than half were male, 160 (53%), with a median age of 6 years (IQR: 1-7 years). Fever was the predominant clinical sign reported by 259 (85.8%) children. Microbiologically confirmed bloodstream infections were detected in 90 (29.8%) children. Slightly more than half of the children with microbiologically confirmed BSIs were detected after blind subculture within 8 hours of initial incubation 51.1% (46, n=90), while an additional 31 (34.4%) and 13 (14.4%) children were detected after blind subculture within 24 hours and 120 hours of incubation, respectively. The most frequently isolated pathogens were Klebsiella pneumoniae 23 (25.6%) and Staphylococcus aureus 22 (24.4%). Overall, Gram-negative bacteria formed the majority, 64 (71.1%) of the isolated pathogens, with 62.5% (40, n=64) being resistant to third-generation cephalosporins. The proportion of methicillin-resistant Staphylococcus aureus strains was 45.5% (10, n=22).

Conclusion and recommendation: Blind subculture after 8 hours of initial incubation correctly detected slightly more than half of the children with microbiologically confirmed bloodstream infections. Incorporating blind subculture on MacConkey agar supplemented with cefotaxime 2µg/ml (MCA-C) after 8 hours of incubation resulted in the correct treatment of half of the children with bloodstream infections caused by Gram-negative bacteria within 24 hours. The study recommends blind subculture within 8 hours of initial incubation to reduce the turnaround time for blood culture results. Furthermore, in areas with high prevalence of third-generation cephalosporin resistance, blind subculture within 8 hours should include MacConkey agar supplemented with cefotaxime 2µg/ml for appropriate treatment within 24 hours.