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As a cause of lung disease (LD), Mycobacterium kansasii is regarded as a highly virulent species among nontuberculous mycobacteria (NTM). Both the frequency of M. kansasii isolates and global prevalence of M. kansasii-LD have increased gradually over recent decades. Treatment of M. kansasii-LD is recommended because of the disease's poor prognosis and fatal outcome. The decision on the optimal time point for treatment initiation should be based on both the benefits and risks posed by multiple antimicrobial agents. For treatment-naïve patients with M. kansasii-LD, rifampin-containing multiple antimicrobial regimens for ≥12 months after culture negative conversion are effective. However, some challenges remain, such as determining the precise length of treatment duration as well as addressing intolerable adverse effects, the uncertain effectiveness of isoniazid and ethambutol in treatment, the uncertain correlation between in vitro drug susceptibility testing and clinical outcomes, and the increasing prevalence of clarithromycin-resistant M. kansasii isolates. Short-course and effective therapies must be developed. New candidate drugs, such as tedizoid and clofazimine, exhibit excellent antimycobacterial activity against M. kansasii in vitro, but in vivo studies of their clinical applications are lacking. This paper reviews the treatment, outcomes and future directions in patients with M. kansasii-LD., Competing Interests: Declaration of Competing Interest The authors have no conflicts of interest relevant to this article., (Copyright © 2020 Formosan Medical Association. Published by Elsevier B.V. All rights reserved.)

Background: Aggressive therapy for Mycobacterium kansasii-pulmonary disease (MK-PD) is recommended because of the virulence of MK. However, some clinicians may be concerned regarding the lengthy course and numerous adverse effects. This study evaluated the natural course of MK-PD and investigated its prognostic factors., Methods: Radiographic outcome, prognostic factors, and mortality within 1 year for MK-PD were obtained from patients in 6 hospitals in Taiwan from 2010 to 2014 (derivation cohort) and validated using patients in 2015 and 2016 (validation cohort)., Results: Of the 109 patients with MK-PD in the derivation cohort, radiographic progression occurred in 70 (64%), with a 1-year mortality rate of 43% and median survival of 71 days, whereas none of the 39 cases without radiographic progression died. All patients with acid-fast smear (AFS) grade ≥ 3 experienced radiographic progression. For the others, the independent risk factors of radiographic progression were fibroCavitary pattern, Leucocyte count >9000/μL, Old age (age >65 years), pUre MK in sputum (no other mycobacteria), and no Diabetes mellitus (the CLOUD factors). By applying these criteria to the validation cohort (n = 112), 3 (9%) of the 33 patients with MK-PD who initially had AFS grade < 3 and < 3 CLOUD risk factors experienced radiographic progression, and none of the 3 died of MK-PD., Conclusions: Because of the high risk of radiographic progression and subsequent fatal outcome, immediate anti-MK treatment is recommended. For patients with MK-PD who have sputum AFS grade <3 and < 3 CLOUD risk factors, regular follow-up may be an alternative., (Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The clinical significance of a single Mycobacterium kansasii (MK) isolation in multiple sputum samples remains unknown. We conducted this study to evaluate the outcome and predictors of developing MK-pulmonary disease (PD) within 1 year among these patients. Patients with a single MK isolation from ≥3 sputum samples collected within 3 months and ≥2 follow-up sputum samples and chest radiography in the subsequent 9 months between 2008 and 2016 were included. The primary outcome was development of MK-PD within 1 year, with its predictors explored using multivariate logistic regression analysis. A total of 83 cases of a single MK isolation were identified. The mean age was 68.9 ± 17.9, with a male/female ratio of 1.96. Within 1 year, 16 (19%) cases progressed to MK-PD; risk factors included high acid-fast smear (AFS) grade (≥3), elementary occupation workers, and initial radiographic score >6, whereas coexistence with other nontuberculous mycobacterium species was protective. Among patients who developed MK-PD, all experienced radiographic progression, and 44% died within 1 year. Although a single MK isolation does not fulfil the diagnostic criteria of MK-PD, this disease may develop if having above-mentioned risk factors. Early anti-MK treatment should be considered for high-risk patients.

A total of 207 cases were selected to evaluate the diagnostic value of C-reactive protein (CRP) in pulmonary infections. The mean +/- SD of CRP values in various pulmonary infections were as follows: 18.62 +/- 11.34 micrograms/ml for 32 cases of exudative-fibrotic tuberculosis; 15.98 +/- 16.66 micrograms/ml for 15 cases of tuberculous pneumonia; 25.61 +/- 18.96 micrograms/ml for 29 cases of tuberculous effusion; 16.66 +/- 10.18 micrograms/ml for 11 cases of tuberculous cavity; 81.1 +/- 24.9 micrograms/ml for 10 cases of miliary tuberculosis; 36.4 +/- 22.1 micrograms/ml for 19 cases of mycoplasmal pneumonia; 241 +/- 72 micrograms/ml for 38 cases of bacterial pneumonia; 225 +/- 65 micrograms/ml for 30 cases of bacterial pneumonia with effusion; 169 +/- 50 micrograms/ml for 16 cases of lung abscess. The CRP values of other pulmonary infections were as follows: 20.6, 20.8 micrograms/ml for two cases of Strongyloides stercoralis pneumonia; 7.4, 1.6 micrograms/ml for two cases of aspergilloma; 11.2, 12.4, 7.6 micrograms/ml for three cases of Pneumocystis carinii pneumonia. Serial changes in CRP values in 13 cases of well-treated bacterial pneumonia showed that values of CRP decreased to below half of the initial value on the 3rd to 4th day, and returned to about normal value on the 10th to 13th day. The study suggested that: a) various types of infections had different levels of CRP values, b) level of CRP values was determined both by the pathogen and the severity of inflammation, c) serial CRP values in bacterial infection could be used as a guide in treatment.