Abstract
BackgroundBlood cultures are one of the most important tests performed by microbiology laboratories. Many hospitals, particularly in low and middle-income countries, lack either microbiology services or staff to provide 24 h services resulting in delays to blood culture incubation. There is insufficient guidance on how to transport/store blood cultures if delays before incubation are unavoidable, particularly if ambient temperatures are high. This study set out to address this knowledge gap.MethodsIn three South East Asian countries, four different blood culture systems (two manual and two automated) were used to test blood cultures spiked with five common bacterial pathogens. Prior to incubation the spiked blood culture bottles were stored at different temperatures (25 °C, in a cool-box at ambient temperature, or at 40 °C) for different lengths of time (0 h, 6 h, 12 h or 24 h). The impacts of these different storage conditions on positive blood culture yield and on time to positivity were examined.ResultsThere was no significant loss in yield when blood cultures were stored < 24 h at 25 °C, however, storage for 24 h at 40 °C decreased yields and longer storage times increased times to detection.ConclusionBlood cultures should be incubated with minimal delay to maximize pathogen recovery and timely result reporting, however, this study provides some reassurance that unavoidable delays can be managed to minimize negative impacts. If delays to incubation ≥ 12 h are unavoidable, transportation at a temperature not exceeding 25 °C, and blind sub-cultures prior to incubation should be considered.
Highlights
Blood cultures are one of the most important tests performed by microbiology laboratories
Several initiatives have been evaluated to reduce the time to identify and test antimicrobial susceptibility of pathogens causing bacteremia with the joint goals of improving patient management and antimicrobial stewardship, for example around-the-clock processing and direct antimicrobial susceptibility testing from positive Blood cultures (BCs) bottles [2, 3]. All these attempts can be undermined by transportation delays or other factors leading to delays in incubating BCs. Such delays occur when laboratories do not operate a 24 h service, which is common in low and middle-income countries (LMICs) or when BCs are referred from other hospitals to a centralized laboratory, common in LMICs and increasingly in other settings due to consolidation of pathology services [4, 5]
The expected organism was obtained from all positive bottles when they were sub-cultured except for one bottle inoculated with S. pneumoniae but grew a Staphylococcus species; this bottle was regarded as contaminated and excluded from further analsysis
Summary
Blood cultures are one of the most important tests performed by microbiology laboratories. Several initiatives have been evaluated to reduce the time to identify and test antimicrobial susceptibility of pathogens causing bacteremia with the joint goals of improving patient management and antimicrobial stewardship, for example around-the-clock processing and direct antimicrobial susceptibility testing from positive BC bottles [2, 3] All these attempts can be undermined by transportation delays or other factors leading to delays in incubating BCs. all these attempts can be undermined by transportation delays or other factors leading to delays in incubating BCs Such delays occur when laboratories do not operate a 24 h service, which is common in LMICs or when BCs are referred from other hospitals to a centralized laboratory, common in LMICs and increasingly in other settings due to consolidation of pathology services [4, 5]. In some LMICs BCs are likely to be stored at tropical ambient temperatures that can exceed recommended incubation temperatures
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