Comparison of separating gel and HB&L pretreatment methods for rapid identification of the pathogenic bacteria in positive blood culture samples by MALDI-TOF MS

Yiwei DING; Yanjun LI; Yanghui QIAN; Zhihai HAN

ABSTRACT

Objective:

To evaluate the identification rate of separating gel or HB&L pretreatment methods of MALDI-TOF-MS, thereby to provide a new idea for the rapid and accurate identification of pathogens of bloodstream infections in daily clinic practice.

Methods:

A total of 149 alarmed positive blood culture samples of single bacterial infection by routine laboratory methods were collected between January to December 2020 from the Sixth Medical Center, Chinese PLA General Hospital. Samples were pretreated with the separation gel accelerating tube method or the HB&L microbial culture system, followed by direct MALDI-TOF MS bacterial identification, the identification rates of the two pretreatment methods were compared and results from the traditional method were used as the standard control.

Results:

Among the 149 positive blood culture samples, 47.0% (70/149) were gram-negative (G -) bacteria and 53.0% (79/149) were gram-positive (G +) bacteria. Identification rate of G -strain level was 78.6% (55/70) by serum separation gel coagulation tube method and 91.4% (64/70) by HB&L microbial culture system, the difference was statistically significant ( P=0.033). Identification rate of G +strain levels was 73.4% (58/79) by serum separation gel coagulation tube method and 87.3% (69/79) by HB&L microbial culture system, the difference was statistically significant ( P=0.028). For G -bacteria in the range of 3.000-2.300, the identification rate was 22.9% (16/70) by serum separation gel accelerating tube method and 38.6% (27/70) by the HB&L microbial culture system, the difference was statistically significant ( P=0.044). For G +bacteria in the range of 3.000-2.300, the identification rate was 19.0% (15/79) by serum separation gel accelerating tube method and 34.2% (27/79) by the HB&L microbial culture system, the difference was statistically significant ( P=0.031).

Conclusion:

The identification rate of HB&L microbial culture system is higher than that of serum separation gel coagulation tube method. Direct MALDI-TOF MS identification of pathogenic bacteria in positive blood culture samples after pretreatment is feasible in daily clinical practice.