Molecular epidemiology and emerging tet(X)-associated resistance of Elizabethkingia spp. in Taiwan, 2016-2022

Elizabethkingia species are opportunistic gram-negative pathogens associated with nosocomial infections and limited therapeutic options. Longitudinal data characterizing antimicrobial resistance and molecular determinants in Taiwan remain scarce. A total of 191 non-duplicate Elizabethkingia clinical isolates were collected at the National Taiwan University Hospital between 2016 and 2022. Species identification was confirmed by 16S rRNA sequencing. Elizabethkingia anophelis predominated (81.7%), followed by E. meningoseptica (9.9%) and E. miricola (7.9%). No major clone was identified. Genes involved in sialic acid metabolism were detected as follows: glmS in 93.2% (178/191), glmM in 97.4% (186/191), nagB in 98.4% (188/191), neuC2 in 24.5% (46/191), and neuC in 2.1% (4/191) of isolates. Antimicrobial susceptibility testing showed very high nonsusceptibility for most agents (≥99.5%). Lower rates of nonsusceptibility were observed for levofloxacin (MIC₅₀/MIC₉₀ = 1/>8 µg/mL; 68.6% susceptible), ciprofloxacin (2/>4 µg/mL; 49.2%), tigecycline (4/>8 µg/mL; 23.0%), and rifampin (>8/>16 µg/mL; 19.9%). Using the breakpoint for other non-Enterobacterales, minocycline was active against all isolates (100.0%, 191/191); however, applying the S. maltophilia criteria, 42 isolates (22.0%) were nonsusceptible to minocycline. Among tetracycline determinants, tet(X) was detected in 22 isolates (11.5%) and tet(K) in 2 isolates (1.0%). With the criteria of S. maltophilia, 10 tet(X)-positive isolates (10/22, 45.5%) showed non-susceptibility to minocycline, implying that tet(X) may contribute to the elevated MIC of minocycline. Our surveillance revealed a rapid increase in resistance to fluoroquinolones and rifampin and the emergence of tet(X)-mediated tetracycline resistance in Elizabethkingia spp. These findings underscore the need for continued molecular monitoring and region-specific antimicrobial stewardship.