To guide the timely selection of antibiotic combinations against carbapenem-resistant Gram negative bacteria (CR-GNB), an in vitro test with a short turn-around time is essential. We developed an in vitro ATP bioluminescent assay to determine effective antibiotic combinations against CR-GNB within 6h. We tested 42 clinical CR-GNB strains (14 Acinetobacter baumannii, 14 Pseudomonas aeruginosa and 14 Klebsiella pneumoniae) against 74 single and two-antibiotic combinations. Approximately 5log10 CFU/ml bacteria were incubated with antibiotic(s) at 35°C, and ATP bioluminescence was measured at 6h and 24h, and compared to 24h viable counts. Receiver operating characteristic (ROC) curves were used to determine the optimal thresholds (TRLU) for differentiating between inhibitory and non-inhibitory combinations. The area under the 6h and 24h ROC curves were compared using the DeLong method. Prospective validation of the established thresholds was conducted using 18 additional CR-GNB. The predictive accuracy of TRLU for the 6h ATP bioluminescence assay was 77.5% for when all species were collectively analyzed. Predictive accuracies ranged from 73.7% – 82.7% when each species were individually analyzed. Upon comparison of the area under the 6h and 24h ROC curves, the 6h assay performed significantly better (p <0.01). Predictive accuracy remained high upon prospective validation of the 6h ATP assay (predictive accuracy, 79.8%; 95% CI, 77.6 – 81.9%), confirming the external validity of the assay. Our findings indicate that our 6h ATP bioluminescence assay can provide guidance for prospective combination selection against CR-GNB in a timely manner, and may be useful in the management of CR-GNB infections.
https://ift.tt/2KAL7nh
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου