Abstract
BackgroundDifficult-to-treat infections caused by rapidly growing mycobacteria (RGM) are increasingly observed in clinical settings. However, studies on antimicrobial susceptibilities and effective treatments against RGM in Japan are limited.MethodsWe conducted susceptibility testing of potential antimicrobial agents, including tigecycline and tebipenem, against RGM. Clinical RGM isolates were collected from a university hospital in Japan between December 2010 and August 2013. They were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and the sequencing of 16S rRNA, rpoB, and hsp65 genes. The samples were utilized for susceptibility testing using 16 antimicrobials, with frozen broth microdilution panels.ResultsForty-two isolates were obtained: 13, Mycobacterium abscessus complex; 12, Mycobacterium chelonae; 9, Mycobacterium fortuitum; and 8, M. fortuitum group species other than M. fortuitum. Different antimicrobial susceptibility patterns were observed between RGM species. Clarithromycin-susceptible strain rates were determined to be 0, 62, and 100% for M. fortuitum, M. abscessus complex, and M. chelonae, respectively. M. abscessus complex (100%) and >80% M. chelonae isolates were non-susceptible, while 100% M. fortuitum group isolates were susceptible to moxifloxacin. Linezolid showed good activity against 77% M. abscessus complex, 89% M. fortuitum, and 100% M. chelonae isolates. Regardless of species, all tested isolates were inhibited by tigecycline at very low minimal inhibitory concentrations (MICs) of ≤0.5 μg/mL. MICs of tebipenem, an oral carbapenem, were ≤4 μg/mL against all M. fortuitum group isolates.ConclusionsOur study demonstrates the importance of correct identification and antimicrobial susceptibility testing, including the testing of potential new agents, in the management of RGM infections.
Highlights
Difficult-to-treat infections caused by rapidly growing mycobacteria (RGM) are increasingly observed in clinical settings
Inducible macrolide resistance, a recently recognized phenomenon, may restrict the therapeutic role of macrolides. This resistance may be related to the insufficient efficacy of clarithromycin-based treatment of M. abscessus subsp. abscessus infection, even when a particular isolate is initially shown to be sensitive to the drug [6, 7]
The minimal inhibitory concentrations (MICs) values of tigecycline against a total of 122 rapidly growing mycobacterial isolates collected in USA [9], 40 isolates obtained in Taiwan [10], 25 isolates collected in Turkey [11], 160 isolates in Taiwan [12], and 57 isolates obtained in Korea [13] were ≤4 μg/mL
Summary
Difficult-to-treat infections caused by rapidly growing mycobacteria (RGM) are increasingly observed in clinical settings. Hatakeyama et al BMC Infectious Diseases (2017) 17:197 macrolide resistant gene, unlike M. abscessus subsp. Difficult-to-treat infections caused by RGM are increasingly observed in clinical settings, especially by M. abscessus complex, which is considered one of the most resistant strains [3]. Inducible macrolide resistance, a recently recognized phenomenon, may restrict the therapeutic role of macrolides. This resistance may be related to the insufficient efficacy of clarithromycin-based treatment of M. abscessus subsp. Only a small amount of data is available on antimicrobial susceptibilities of RGM isolated in Japan. Susceptibility of RGM to some antimicrobials can be tested in a limited number of reference laboratories, while an accurate identification of RGM at the species level is difficult for most of the clinical laboratories, resulting in limited susceptibility data as well
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