Background and aims Blood cultures are taken to detect bacteraemia and direct antimicrobial therapy. Uncertainty regarding contamination versus bacteraemia leads to financial and human cost through increased investigations and prolonged antimicrobial therapy¹. Contamination may be due to inadequate aseptic technique, with rates up to 10%².

This audit aims to establish bacteraemia rates, contamination rates and review if positive blood cultures change clinical management.

Methods A retrospective list of all paediatric blood cultures collected between 7/8/13–7/12/13 was compiled and case-notes of positive results reviewed using a designated proforma.

Contamination was suspected with multiple organisms, particularly if skin flora, exclusively aerobic/anaerobic isolates and reassuring inflammatory markers or clinical condition.

Results 339 blood cultures were taken, 19 were positive.

47% of positive results occurred in patients <1 year old.

The main indication was pyrexia (63%)

42% of cultures were collected on the ward

Documented asceptic non-touch technique in 1 case (5%)

Antibiotics were administered before collection in 10%

68% of positive results were felt to be contaminants

Our bacteraemia rate is calculated as 1.76%.

37% of all positive cultures were repeated including three of six confirmed bacteraeimia cases.

A positive culture result altered clinical management in 32%.

Conclusions Bacteraemia rates are low at 1.76%. However, there is still a significant contamination rate of 68%, especially in infants where asceptic procedures are difficult. Our results confirm that a blood culture result in isolation is of limited value and clinical correlation is paramount.

References

1. Bates DW, Goldman L, Lee TH. Contaminant blood cultures and resource utilisation. The true consequences of false positive results. JAMA 1991 265:365–369

2. Taking Blood Cultures – a summary of best practice. Saving Lives: reducing infection, delivering clean and safe care. Department of Health, London 2007. Accessed (14th January 2012) via Department of Health Website at: hcai.dh.gov.uk/files/2011/03/Document_Blood_culture_FINAL_100826.pdf