1. Antimicrobial susceptibility of Bacteroides fragilis group organisms in Hong Kong, 2020–2021.
- Author
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Fang, Hanshu, Li, Xin, Yan, Mei-Kum, Tong, Man-Ki, Chow, Kin-Hung, Cheng, Vincent Chi-Chung, and Ho, Pak-Leung
- Subjects
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MATRIX-assisted laser desorption-ionization , *BACTEROIDES fragilis , *DESORPTION ionization mass spectrometry , *MOXIFLOXACIN - Abstract
This retrospective study analyzed the susceptibility levels of Bacteroides fragilis group (BFG) in a hospital-based laboratory where disk diffusion test (DDT) was routinely performed. Isolates non-susceptible to imipenem and metronidazole by DDT were further investigated using a gradient method. The DDT and MIC susceptibility data of clindamycin, metronidazole, moxifloxacin and imipenem obtained on Brucella blood agar for 1264 non-duplicated isolates during 2020–2021 were analyzed. Species identification was obtained by matrix-assisted laser desorption ionization time-of-flight mass spectrometry and 16S rRNA sequencing. Interpretative agreement of DDT results using the 2015 EUCAST tentative and 2021 CA-SFM breakpoints was compared against MIC as the reference. The dataset included 604 B. fragilis (483 division I, 121 division II isolates), 415 non- fragilis Bacteroides , 177 Phocaeicola and 68 Parabacteroides. Susceptibility rates for clindamycin (22.1–62.1%) and moxifloxacin (59.9–80.9%) were low and many had no inhibition zones. At the EUCAST and CA-SFM breakpoints, 83.0 and 89.4% were imipenem-susceptible, and 89.6% and 97.4 were metronidazole-susceptible. MIC testing confirmed 11.4% and 2.8% isolates as imipenem-non-susceptible and metronidazole-resistant, respectively. Significant numbers of false-susceptibility and/or false-resistance results were observed at the CA-SFM breakpoint but not the EUCAST breakpoint. Higher rates of imipenem and/or metronidazole resistance were detected in B. fragilis division II, B. caccae, B. ovatus, B. salyersiae, B. stercoris and Parabacteroides. Co-resistance to imipenem and metronidazole was detected in 3 B. fragilis division II isolates. The data demonstrated emerging BFG resistance to several important anti-anaerobic antibiotics and highlights the importance of anaerobic susceptibility testing in clinical laboratories to guide therapy. • Antimicrobial resistance in Bacteroides fragilis group is emerging. • Antimicrobial susceptibilities of 1264 B. fragilis group were analyzed. • Clindamycin and moxifloxacin resistance rates were high. • Imipenem resistance rate was 11.4%. • Metronidazole resistance rate was 2.8%. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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