Antimicrobial Susceptibility of Elizabethkingia Species: Report from a Reference Laboratory

Elizabethkingia species are Gram-negative bacilli that were most recently linked to a cluster of infections in the Midwestern United States from 2016 to 2017. Inappropriate empirical and directed antibiotic selection for this organism is common among providers and is an independent risk factor for mortality. Trends in antimicrobial susceptibility profiles of Elizabethkingia species from a referral laboratory over a 10-year period were reviewed. Identification methods used over time varied and included biochemical panels, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and 16S rRNA gene sequencing. Agar dilution was used to conduct antimicrobial susceptibility testing. One hundred seventy-four clinical isolates were included. The lower respiratory tract (20/37; 54%) was the most common specimen source in pediatric patients, whereas blood isolates (62/137; 45%) constituted the most prevalent source in adults. Among the identified species, Elizabethkingia meningoseptica (72/121; 59%) constituted the majority. All Elizabethkingia species tested against minocycline were susceptible (18/18; 100%), and 90% of isolates tested against trimethoprim-sulfamethoxazole (TMP-SMX) (117/130) were susceptible. Of the 12 Elizabethkingia miricola isolates, most of the tested isolates were susceptible to piperacillin-tazobactam (11/12; 92%) and levofloxacin (11/12; 92%), whereas the Elizabethkingia anophelis isolates most often tested susceptible to piperacillin-tazobactam (13/14; 93%). In this study, Elizabethkingia species showed high rates of in vitro susceptibility to minocycline and TMP-SMX. Further studies are needed to investigate the clinical implications of species-level differences in antimicrobial susceptibilities in this genus.