Blood culture and control bacterial strains
Upon clinical suspicion of BSI, whole blood samples were simultaneously
obtained for blood culture and molecular diagnosis. Two sets of blood
cultures were collected for each patient according to routine clinical
practice, and each set consisted of an aerobic bottle and an anaerobic
bottle. The blood cultures were incubated at 37℃ in a BacT/ALERT® 3D
System (BioMérieux, France). When the system showed a positive signal,
Gram staining was performed, followed by subculture on a Columbia blood
agar plate at 37℃ with 5% CO2. Following overnight
incubation, the pathogens were further identified by matrix-assisted
laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF
MS) (VITEK® MS system, BioMérieux, France). The positive control
bacteria were A. baumannii ATCC 19606 with 5 clinical isolates
and K. pneumonia CMCC 46117 with 33 clinical isolates. A total of
131 other clinical isolates that are commonly found in BSI were used as
negative controls (Table 1 ).