Blood Culture Contaminants in a Paediatric Population : Retrospective study from a tertiary hospital in Oman

Abstract

Objectives: Most children presenting with febrile illness require a blood culture to determine the causative organism as well as its sensitivity to antibiotics. However, false-positive results lead to unnecessary hospitalisations, prescriptions and tests. This study aimed to evaluate the impact of false-positive blood cultures among a paediatric population at a tertiary hospital in Oman. Methods: This retrospective study included all 225 children <13 years old with positive blood cultures who presented to the Sultan Qaboos University Hospital, Muscat, Oman, between July 2011 and December 2013. Blood cultures were reviewed to determine whether they were true-positive or contaminated. Results: A total of 344 positive blood cultures were recorded during the study period, of which 185 (53.8%) were true-positive and 159 (46.2%) were contaminated. Most true-positive isolates (26.5%) were coagulase-negative Staphylococcus spp. (CONS) followed by Escherichia coli (9.7%), while the majority of contaminated isolates were CONS (67.9%) followed by Streptococcus spp. (6.9%). Children with contaminated cultures were significantly younger (P <0.001) while those with true-positive cultures required significantly more frequent hospital admissions, longer hospital stays and more frequent antibiotic prescriptions (P <0.001 each). Chronic illness and mortality was significantly more frequent among those with true-positive cultures (P <0.001 and 0.04, respectively). While white blood cell and absolute neutrophil counts were significantly higher in truepositive cultures (P <0.001 each), there was no significant difference in C-reactive protein (CRP) level (P = 0.791). Conclusion: In this population, CRP level was not an adequate marker to differentiate between true- and falsepositive cultures. A dedicated well-trained phlebotomy team for paediatric patients is essential.