Carbapenem resistance among Gram-negative isolates collected from patients in ICU and non-ICU hospital wards in Hong Kong: SMART 2017-2020

Objectives: The aim of this study was to estimate carbapenem resistance in Pseudomonas aeruginosa and Enterobacterales isolated from infected patients in intensive care unit (ICU) and non-ICU hospital wards in Hong Kong.

Methods: Isolates of Pseudomonas aeruginosa (ICU, n = 35; non-ICU, n = 264) and Enterobacterales (ICU, n = 129; non-ICU, n = 1390) were collected in four Hong Kong hospitals in 2017-2020. Clinical and Laboratory Standards Institute broth microdilution minimum inhibitory concentrations (MICs) were interpreted according to Clinical and Laboratory Standards Institute 2021 M100 breakpoints. β-lactamase genes were identified in imipenem-, imipenem/relebactam-, and ceftolozane/tazobactam-nonsusceptible isolates.

Results: Ceftolozane/tazobactam demonstrated potent in vitro activity against both P. aeruginosa (ICU, 88.6%; non-ICU, 98.5%) and Enterobacterales (96.1%; 97.1%). Percent susceptible values for P. aeruginosa isolates from ICU and non-ICU patients, respectively, were as follows: meropenem (ICU, 74.3%; non-ICU, 84.1%) and imipenem (68.6%; 73.1%). Only 1 of 77 isolates tested for β-lactamase genes carried a carbapenemase (VIM-2). Percent susceptible values for Enterobacterales isolates from ICU and non-ICU patients were as follows: meropenem (100%; 99.4%), ertapenem (100%; 98.0%), and imipenem (88.4%; 88.6%). A total of 62 Enterobacterales isolates were tested for β-lactamase genes. Only three isolates carried a carbapenemase gene; two (both Escherichia coli) were metallo-β-lactamase-positive (both NDM-5), and one (Klebsiella pneumoniae) was OXA-48-like-positive.

Conclusions: Carbapenem-nonsusceptible isolates of P. aeruginosa were common (>15% of isolates). P. aeruginosa percent susceptible values for ceftolozane/tazobactam (97.3% susceptible overall) were ≥14% higher than those for carbapenems in both ICU and non-ICU isolates. Carbapenemases were rare among both P. aeruginosa (one isolate) and Enterobacterales (three isolates). Most Enterobacterales isolates tested from ICU and non-ICU patients in Hong Kong hospitals in 2017-2020 were susceptible to meropenem and ertapenem (≥98%); imipenem was less active (89% susceptible).