In vitro susceptibilities of Stenotrophomonas maltophilia isolates to antimicrobial agents commonly used for related infections: Results from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program, 2004-2020

Stenotrophomonas maltophilia is an emerging opportunistic pathogen for which there are limited therapeutic options because of intrinsic multidrug resistance. S. maltophilia isolates were collected as part of the Antimicrobial Testing Leadership and Surveillance (ATLAS) program and minimum inhibitory concentrations (MICs) were determined using broth microdilution methods. Susceptibility was interpreted according to Clinical and Laboratory Standards Institute (CLSI) breakpoints. Isolates with tigecycline MIC ≤2 mg/L were defined as susceptible, using the United States Food and Drug Administration criteria of Enterobacterales. A total of 2330 S. maltophilia isolates were collected from 47 countries worldwide in the ATLAS program from 2004 to 2020. Most patients were hospitalized (92.3%, 2151/2330) and respiratory tract infections (47.8%, 1114/2330) were the most common source of isolates. Minocycline had the highest susceptibility rate (98.8%), followed by levofloxacin (85.0%), trimethoprim-sulfamethoxazole (TMP-SMX) (84.4%), and ceftazidime (53.7%). A total of 98.3% (2290/2330) of S. maltophilia isolates had tigecycline MIC ≤2 mg/L. Among the S. maltophilia isolates exhibiting resistance to levofloxacin and ceftazidime, 89.3% (150/168) and 97.3% (692/711), respectively, were susceptible to tigecycline. Eight countries provided more than 30 isolates and were selected for comparison. Geographical difference in antimicrobial resistance was significant for levofloxacin, minocycline, and tigecycline (all P<0.05) but not for ceftazidime (P=0.467). These in vitro data demonstrated that minocycline had a higher susceptibility rate than levofloxacin and ceftazidime, and that tigecycline could be an alternative or salvage option for the treatment of S. maltophilia infections.