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Abstract
Background
Diagnosis of nontuberculous mycobacterium (NTM) is challenging, and clinical, radiological and microbiological criteria should be met. Traditionally, culture results on solid media have been reported semi-quantitatively, but no study exists regarding the clinical significance of low-colony count culture reports. The authors of the present study analyzed the clinical significance of low-colony count specimens of NTM with a greater than three-year follow-up period.
Methods
A total of 341 clinical isolates were evaluated among the isolates at Seoul National University Hospital and Seoul National University Borame Hospital from October 2005 to September 2006. Colony count less than 50 was considered a low-colony count specimen. Identifications of NTM from all the isolates were performed using a DNA chip (PCR reverse hybridization, LG Life Science, Korea). Clinical significance was analyzed by reviewing the medical records of patients with greater than three years of follow-up data after NTM isolation from respiratory samples.
Results
NTM lung disease was observed in 27.0% of the patients with low-colony count specimens among 167 patients with respiratory samples, and 70.4% of the patients were treated. The low-colony count patients had less NTM lung disease, longer incubation period, and less acid fast bacilli-positivity than patients with a colony count greater than 50.
Figures and Tables
Table 2
Distribution of species of nontuberculous mycobacterium
*M. fortuitum, M. senegalense 3; M. avium, M. abscessus 2; M. avium, M. intracellulare 2; M. intracellulare, M. abscessus 2; M. avium, M. terrae complex 1; M. intracellulare, M. fortuitum 1; M. intracellulare, M. gordonae 1; M. intracellulare, M. terrae complex 1; M. gordonae, M. terrae complex 1, †Mycobacterium Genus but cannot identify the species because the lack of specific probe in DNA chip, ‡DNA chip gave the negative results.
Table 3
Comparison of characteristics of the patients with the <50 and ≥50 colony-counts in respiratory specimens
*They met both clinical and microbiological criteria, †They met microbiological criteria but did not meet clinical criteria, ‡NTM was isolated, but they did not meet microbiological criteria, §NTM infection was suspicious, but follow-up study was insufficient, ∥Median (minimum-maximum).
Abbreviation: AFB, Acid-fast bacilli.
References
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