Objectives and Methods Expedient diagnosis of bloodstream infection is vital for the treatment of immunocompromised patients. Automated blood culture systems have revolutionised laboratory procedures and blood culture bottles have been developed to maximise detection of positive samples. Traditionally, blood cultures from oncology patients in our hospital were collected into standard aerobic (SA) and anaerobic (SN) bottles (bioMerieux). Whereas the use of SN bottles continued, in October 2006 SA bottles were replaced with new “FA bottles”, which should improve the growth of micro-organisms by sequestering inhibitors onto activated charcoal present in the culture medium. However, culture fluid from the FA bottles proved difficult to examine microscopically, occasionally resulting in delayed interpretation of culture findings. To determine whether the increased complexity could be justified on the basis of clinical benefit, we collected retrospective data on blood cultures from paediatric oncology patients for 12-month periods preceding and following the transition to FA bottles.
Results Approximately 1000 blood cultures were collected in each of the time frames. A positivity rate of 16.2% using SA bottles fell to 11.3% following the introduction of FA bottles (p<0.005). Analysis of the spectrum of organisms cultured suggested that SA bottles may improve the detection of specific bacterial strains, especially the Gram-negative species causing bloodstream infection in our oncology patients over the study period.
Conclusion No evidence was found to support any clinical benefit from continued use of FA bottles in our unit. The value of tailoring culture methods to the needs of local patient groups has been highlighted.