Abstract
Background: This study was done to compare the growth of pathogens in paired aerobic/anaerobic blood culture bottles versus the use of only aerobic bottles, and to analyze the time to growth in both atmospheres. Methods: We retrospectively evaluated the results of all blood cultures collected over a 2-y period for the diagnosis of central venous catheter-related bloodstream infections or other severe infections in oncology patients. Results: Among the 487 isolates, 174 (35.7%), all aerobic, grew only in the aerobic bottle; 250 (51.3%), all aerobic, grew in both bottles; and 63 (12.9%) grew only in the anaerobic bottle, of which 24 were anaerobic and 39 were aerobic microorganisms (8% of positive blood cultures). Of these 39 aerobic microorganisms, 12 were Gram-negative, 17 staphylococci (4 were Staphylococcus aureus), 5 streptococci, 2 Gram-positive bacilli, and 3 mixed growth. Though the mean time to positivity of pathogens grown in both atmospheres was significantly lower in the aerobic bottle than in the anaerobic bottle, in 71 cases (28.4%) the pathogens developed earlier in the anaerobic bottle than in the aerobic bottle – in 36 of these cases at least 1 h earlier, which is significant for starting targeted therapy. Conclusions: The use of paired aerobic/anaerobic blood culture bottles allowed the diagnosis of a percentage of bacteraemia due to either anaerobic or aerobic pathogens that would have been missed, as they grew only in the anaerobic atmosphere. Moreover in 8% of bacteraemia we identified a significant decrease in the time to detection, resulting in the opportunity to better manage the infections without an increase in costs.
Acknowledgements
We are grateful to the technicians Lorena Moretti, Chiara Gulmini, and Adeline Ngounou-Ngassa for their valuable collaboration.
Declaration of interest: The authors declare that they have no conflict of interest.