Comparative in vitro activity of minocycline, tigecycline, eravacycline, and omadacycline against Acinetobacter baumannii, Stenotrophomonas maltophilia, and the Burkholderia cepacia complex.

OBJECTIVES

Infections caused by multidrug-resistant non-glucose-fermenting Gram-negative bacilli (NFGNB) are therapeutic challenges. This study was aimed to evaluate the in vitro activity of tetracyclines against clinically important NFGNB.

METHODS

The MICs of minocycline, tigecycline, eravacycline, and omadacycline were determined using broth microdilution for 100 nonduplicate clinical isolates each of Acinetobacter baumannii, Stenotrophomonas maltophilia, and the Burkholderia cepacia complex (2021-2023). Minocycline susceptibility was interpreted by the Clinical and Laboratory Standards Institute clinical breakpoint of 1 mg/L. Tigecycline and eravacycline susceptibility was interpreted by nonclinical pharmacokinetic/pharmacodynamic cutoff values of 1 mg/L, given the absence of NFGNB-specific clinical breakpoints.

RESULTS

The MIC₅₀/MIC₉₀ (mg/L) for minocycline, tigecycline, eravacycline, and omadacycline were 4/16, 1/4, 0.5/1, and 4/8 for A. baumannii; 0.5/2, 1/4, 1/4, and 8/32 for S. maltophilia; and 2/16, 2/8, 1/4, and 8/32 for B. cepacia complex, respectively. For A. baumannii, eravacycline was the most active agent exhibiting 94% susceptibility, significantly higher than minocycline (42%) and tigecycline (55%) (both P < 0.001). For S. maltophilia, minocycline ranked first in activity with higher susceptibility (86%) than eravacycline (59%) and tigecycline (54%) (both P < 0.001). In B. cepacia complex, eravacycline exhibited modest activity with significantly higher susceptibility (67%) than tigecycline (13%) and minocycline (11%) (both P < 0.001). MIC correlations between tetracyclines were moderate to strong, but weaker in B. cepacia complex than in A. baumannii (P < 0.05).

CONCLUSIONS

Among tested tetracyclines, minocycline was most active against S. maltophilia, whereas eravacycline was most active against A. baumannii and B. cepacia complex. These findings highlight the necessity of species-specific susceptibility testing to guide therapy.