Direct-on-Target Microdroplet Growth Assay for Detection of Bacterial Resistance in Positive Blood Cultures

Hao Tang; Rongrong Li; Huaming Xu; Guoping Lu; Zhen Liu; Wensu Yang; Zhaoxin Xia; Yi Zhu; Jilu Shen

doi:10.2147/IDR.S336987

Direct-on-Target Microdroplet Growth Assay for Detection of Bacterial Resistance in Positive Blood Cultures

Infect Drug Resist. 2021 Nov 6:14:4611-4617. doi: 10.2147/IDR.S336987. eCollection 2021.

Authors

Hao Tang¹, Rongrong Li², Huaming Xu¹, Guoping Lu³, Zhen Liu¹, Wensu Yang¹, Zhaoxin Xia¹, Yi Zhu¹, Jilu Shen¹

Affiliations

¹ The Fourth Affiliated Hospital of Anhui Medical University Laboratory Department, Hefei, People's Republic of China.
² The First Affiliated Hospital of Anhui Medical University Laboratory Department, Hefei, People's Republic of China.
³ Laboratory Department of Fuyang Hospital Affiliated to Anhui Medical University, Fuyang, Anhui, 236000, People's Republic of China.

Abstract

Introduction: The recently developed DOT-MGA (direct-on-target microdroplet growth assay) has shown the desirability of direct application of this approach in positive blood cultures and its good performance in detection. This study selected 44 Enterobacteriaceae strains and implemented a DOT-MGA assay on blood cultures to detect their resistance to seven antibiotics. The results of DOT-MGA were compared with the other two antimicrobial susceptibility testing (AST) methods to analyze the detection performance of DOT-MGA.

Methods: We adopted the differential centrifugation to process positive blood-culture (BC). Processed BC broth was directly used for rapid AST using DOT-MGA. Droplets of 6 µL with and without antibiotics at the EUCAST breakpoint concentration were spotted in triplicates onto the surface of a MALDI target. The plates were incubated in a wet box for 4 h before the broth was removed with filter paper. Bruker Biotyper software was used to analyze the test results compared with standard database, and the scores were used to quantify and determine the results.

Results: DOT-MGA results were compared with the direct-from-BC disk-diffusion method and results were reported by broth microdilution method, respectively. The comparison demonstrated a 100% growth efficiency in DOT-MGA, a 100% classification consistency for ampicillin, ceftriaxone, and gentamicin, and >93% classification consistency for tobramycin, aztreonam, trimethoprim-sulfamethoxazole (TMP-SMX), and ceftazidime.

Discussion: These study results have shown that DOT-MGA is suitable for directly identifying bacterial resistance to positive blood cultures in clinical microbiology laboratories. Furthermore, it is conducive for early diagnosis and treatment of patients with bloodstream infection due to its convenience, time efficiency, and good performance in identifying multiple antibiotic-insensitive bacteria.

Keywords: DOT-MGA; MALDI-TOF; antibiotic resistance; blood culture; direct-from-BC disk-diffusion method; rapid antimicrobial susceptibility testing.

Grants and funding

This work was funded through a grant from Anhui Provincial Department of Education for university cooperative research and public health collaborative innovation project in Anhui Province in 2020 (Grant No. GXXT-2020-016) and a grant from Anhui Provincial Health Commission for key scientific research projects in 2021 (Grant No. AHWJ2021a011).