Aims Neonatal sepsis is an important cause of mortality and morbidity among neonates1. A number of laboratory tools are available to aid diagnosis of sepsis, but detection of bacteraemia remains the ‘gold standard’ and allows targeted treatment against specific organisms2. However, contamination of blood cultures can occur leading to false-positive results. This causes challenges in determining whether the organism represents a true infection requiring treatment, and often results in unnecessary treatment and increasing healthcare costs from prolonged hospital stays, additional tests and prolonged antibiotic treatment3. The suggested acceptable rate for blood culture contaminants is 2%– 3%4,5. We performed a retrospective audit evaluating the rate of blood culture contaminants in our unit to compare local practice to international recommendations.
Methods We identified all blood cultures taken within the neonatal unit from 1st September 2015 to 31st August 2016. Electronic notes were then reviewed for any baby who had a ‘positive’ blood culture to determine if this was a contaminant, if further tests were required and the subsequent length of antibiotic treatment.
Results We identified 587 blood cultures. 23 grew an organism, of which 17 (2.9%) were felt to be contaminated samples. Coagulase negative staphylococcus accounted for 82% (14/17) of all blood culture contaminants. Of the 17 contaminated samples, 10 babies had a repeat sent, none of which had a positive growth. All 10 also received a longer course of antibiotics- from the standard 36 hours to up to 5 days while waiting for results of the repeat sample.
Conclusion Our audit has shown the rate of contaminated blood cultures in our neonatal unit falls just within the recommended rate of 2%–3%. However, 58% of babies who had a contaminated sample required a prolonged course of antibiotics while waiting for repeat tests. Contaminated blood cultures often grow normal skin flora suggesting poor hand hygiene, ineffective skin cleaning and poor venipuncture techniques as the main causes6. By improving education and adherence to a sterile venipuncture technique, the contamination rate could further be reduced thereby resulting in fewer babies receiving unnecessary tests and improved antibiotic stewardship.
Simonsen KA, Anderson-Berry AL, Delair SF, Davies HD. Early-onset neonatal sepsis. Clin Microbiol Rev 2014 Jan;27(1): 21–47.
Hall KK, Lyman JA. Updated review of blood culture contamination. Clin Microbiol Rev. 2006 Oct; 19(4): 788–802.
Contaminant blood cultures and resource utilisation. The true consequences of false-positive results. Bates DW, Goldman L, Lee TH JAMA. 1991 Jan 16; 265 (3):365–9.
Chandrasekar, P. H., and W. J. Brown. 1994. Clinical issues of blood cultures. Arch. Intern. Med. 154:841–849.
Strand, C. L., R. R. Wajsbort, and K. Sturmann. 1993. Effect of iodophor vs iodine tincture skin preparation on blood culture contamination rate. JAMA 269:1004–1006.
Roth A, Wiklund AE, Palsson AS, et al. Reducing blood culture contamination by a simple informational intervention. J Clin Microbiol 2010;48(12):4552–4558.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.