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Ito A, Nanjo Y, Kajiwara C, Shiozawa A, Urabe N, Homma S, Kishi K, Yamada K, Ishii Y, Tateda K. Intrinsic clarithromycin heteroresistance in Mycobacterium avium. J Infect Chemother 2024; 30:752-756. [PMID: 38369123 DOI: 10.1016/j.jiac.2024.02.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/05/2024] [Accepted: 02/14/2024] [Indexed: 02/20/2024]
Abstract
BACKGROUND Mycobacterium avium is associated with pulmonary disease in otherwise healthy adults. Several clarithromycin-refractory cases have been reported, including some cases caused by clarithromycin-susceptible strains. OBJECTIVES To characterize the reason for the discrepancy between clinical response and antibiotic susceptibility results. METHODS We conducted population analysis of clarithromycin-tolerant and heteroresistant subpopulations of M. avium cultured in vitro and in homogenates of infected lungs of mice. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined for 28 M. avium and two M. kansasii strains. Mice were intranasally infected with M. avium and treated with or without clarithromycin (100 mg/kg) thrice weekly. They were sacrificed on day 35 and the bacteria in lung homogenates were tested for clarithromycin resistance. Population analysis assays were performed based on colony growth on plates containing two-fold dilutions of clarithromycin. RESULTS The MBC/MIC ratios were ≥8 in all 28 strains of M. avium tested. In the population analysis assay, several colonies were observed on the plates containing clarithromycin concentrations above the MIC (2-64 mg/L). No growth of M. kansasii colonies was observed on the plates containing clarithromycin concentrations ≥2 mg/L. M. avium in the homogenates of infected lungs showed clearer clarithromycin-resistant subpopulations than in vitro, regardless of clarithromycin exposure. CONCLUSION M. avium shows intrinsic heterogeneous resistance (heteroresistance) to clarithromycin. This may explain the observed discrepancies between clarithromycin susceptibility testing results and clinical response to clarithromycin treatment. Further studies are needed to confirm a link between heteroresistance and clinical outcomes.
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Affiliation(s)
- Ai Ito
- Department of Respiratory Medicine, Toho University Omori Medical Center, 6-11-1 Omori-nishi, Ota-ku, Tokyo, 143-8541, Japan; Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Yuta Nanjo
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan; Department of Respiratory Medicine, Juntendo University School of Medicine, 3-1-3 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
| | - Chiaki Kajiwara
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Ayako Shiozawa
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Naohisa Urabe
- Department of Respiratory Medicine, Toho University Omori Medical Center, 6-11-1 Omori-nishi, Ota-ku, Tokyo, 143-8541, Japan
| | - Sakae Homma
- Department of Respiratory Medicine, Toho University Omori Medical Center, 6-11-1 Omori-nishi, Ota-ku, Tokyo, 143-8541, Japan
| | - Kazuma Kishi
- Department of Respiratory Medicine, Toho University Omori Medical Center, 6-11-1 Omori-nishi, Ota-ku, Tokyo, 143-8541, Japan
| | - Kageto Yamada
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Yoshikazu Ishii
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Kazuhiro Tateda
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
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