Spatial Heterogeneity of Nontuberculous Mycobacterial Pulmonary Disease in Shanghai: Insights from a Ten-Year Population-Based Study.

OBJECTIVE: To investigate the spatial heterogeneity of nontuberculous mycobacterial pulmonary disease (NTM-PD) in Shanghai. METHODS: A population-based retrospective study was conducted using presumptive pulmonary tuberculosis surveillance data of Shanghai between 2010 and 2019. The study described the spatial distribution of NTM-PD notification rates, employing hierarchical Bayesian mapping for high-risk areas and the Getis-Ord Gi* statistic to identify hot spots and explore associated factors. RESULTS: Of 1652 NTM-PD cases, the most common species was Mycobacterium kansasii complex (MKC) (41.9%), followed by Mycobacterium avium complex (MAC) (27.1%) and Mycobacterium abscessus complex (MABC) (16.2%). MKC-PD patients were generally younger males with a higher incidence of pulmonary cavities, while MAC-PD patients were more often farmers or had a history of tuberculosis treatment. MKC-PD hot spots were primarily located in the areas alongside the Huangpu River, while MAC-PD hot spots were mainly in the western agricultural areas. Patients with MKC-PD and MAC-PD exhibited a higher risk of spatial clustering compared to those with MABC-PD. CONCLUSIONS: Different types of NTM-PD exhibit distinct patterns of spatial clustering and are associated with various factors. These findings underscore the importance of environmental and host factors in the epidemic of NTM-PD.

Clinical and Microbiological Characteristics of Mycobacterium kansasii Pulmonary Infections in China.

Mycobacterium kansasii, an important opportunistic pathogen of humans, causes serious pulmonary disease. Sixty M. kansasii isolates were collected for investigating the clinical characteristics of patients with M. kansasii infections as well as drug susceptibility and genotypes of M. kansasii. More than 90% of the patients infected with M. kansasii were from eastern China. According to the internal transcribed spacers (ITS), rpoB, hsp65, and tuf, all M. kansasii isolates were classified as molecular type I, irrespective of the disease manifestation. Sixty M. kansasii isolates from China were diverse and separated into four branches. Pairwise average nucleotide identity (ANI) values for M. kansasii isolates affiliated with different genotypes were more than 85%. The earliest isolate was isolated from Jiangsu in 1983. Of the isolates, 78.3% (47/60) were isolated since 1999. All isolates were sensitive to rifabutin. All but one isolate was sensitive to clarithromycin. Sensitivity rates to rifampin, amikacin, moxifloxacin, and linezolid were 80.0%, 90.0%, 88.3%, and 91.7%, respectively. A high rate of resistance was noted for ciprofloxacin (44 isolates, 73.3%) and ethambutol (46 isolates, 76.7%). Compared with M. tuberculosis H37Rv, 12 mutations of embCA were observed in all M. kansasii isolates. All these 60 M. kansasii isolates shared identical sequences of rpoB, inhA, katG, rrl, rrs, rpsL, gyrA, and gyrB. In conclusion, M. kansasii isolates are exhibiting greater genetic diversity globally. The resistance mechanism of M. kansasii is not necessarily related to gene mutation. IMPORTANCE M. kansasii type I is the main genotype spreading worldwide. The molecular history of the global spread of type I isolates remains largely unclear. We conducted a detailed analysis of genomic evolution of global M. kansasii isolates. Our results suggest that M. kansasii isolates exhibit greater genetic diversity globally.

Population genomics provides insights into the evolution and adaptation to humans of the waterborne pathogen Mycobacterium kansasii.

Mycobacterium kansasii can cause serious pulmonary disease. It belongs to a group of closely-related species of non-tuberculous mycobacteria known as the M. kansasii complex (MKC). Here, we report a population genomics analysis of 358 MKC isolates from worldwide water and clinical sources. We find that recombination, likely mediated by distributive conjugative transfer, has contributed to speciation and on-going diversification of the MKC. Our analyses support municipal water as a main source of MKC infections. Furthermore, nearly 80% of the MKC infections are due to closely-related M. kansasii strains, forming a main cluster that apparently originated in the 1900s and subsequently expanded globally. Bioinformatic analyses indicate that several genes involved in metabolism (e.g., maintenance of the methylcitrate cycle), ESX-I secretion, metal ion homeostasis and cell surface remodelling may have contributed to M. kansasii's success and its ongoing adaptation to the human host.

Delayed health consequences of COVID-19 lockdown in an older adult.

We report a case of a retired school teacher who presented with rapid cognitive and functional decline following the COVID-19 lockdown period that was diagnosed as worsening depression by referring physician. This highlights the potentially life-threatening consequences of delayed diagnosis and management of delirium, an often reversible syndrome, due to lockdown restrictions. As the pandemic outlives its initial projections, its downstream impact on an already vulnerable population continues to emerge.

Human pathogenic Mycobacterium kansasii (former subtype I) with zoonotic potential isolated from a diseased indoor pet cat, Japan.

Nontuberculous mycobacterial (NTM) infections in humans have increased in prevalence in recent decades. Mycobacterium kansasii is one of the most prevalent human pathogenic NTM species worldwide. Herein, we report the first isolation of M. kansasii from an indoor domestic cat in Japan. Comparative genome sequence analysis of the feline isolate showed this pathogen is genetically identical to human pathogenic M. kansasii. This finding suggests that M. kansasii has a potential risk of zoonoses and requires the "One Health" approach to control NTM infection.

Detection of Mycobacterium kansasii using a combination of loop-mediated isothermal amplification (LAMP) and lateral flow biosensors.

Mycobacterium kansasii is an opportunistic pathogen that causes both intrapulmonary and extrapulmonary infections. The symptoms of the pulmonary diseases caused by M. kansasii closely resemble Mycobacterium tuberculosis. Rapid and accurate differentiation of M. kansasii from M. tuberculosis, as well as other mycobacteria, is crucial for developing effective therapeutics and disease treatment. In this study, we combined loop-mediated isothermal amplification (LAMP) with lateral flow biosensors (LFB) to detect M. kansasii, by targeting the species-specific sequence of rpoB, a gene which encodes the ß subunit of bacterial RNA polymerase. The assay was validated to ensure that it was highly selective by testing M. kansasii, M. tuberculosis, other species of respiratory bacteria, and other nontuberculous mycobacteria. The detection limit of the assay was 1 fg/µL of DNA and 50 CFU of bacilli in sputum. The M. kansasii-LAMP-LFB assay is a fast, cheap, and accurate method for detecting M. kansasii by constant temperature amplification and simple interpretation.

Clinical and epidemiological characteristics of M. kansasii pulmonary infections from Rio de Janeiro, Brazil, between 2006 and 2016. / Características clínicas e epidemiológicas de casos de infecção pulmonar por Mycobacterium kansasii no Rio de Janeiro, no período de 2006 a 2016.

Objective To evaluate clinical, tomographic, and microbiological characteristics of pulmonary disease caused by M. kansasii (MKPD) in patients treated at an outpatient unit from 2006-2016. Methods We studied thirty eight patients, and analyzed socio-demographic, clinical-radiological, laboratory, and therapeutic characteristics. Results The mean age was 64 years (SD = 10.6; IIQ = 57-72; median = 65.0), and 22 (57.9%) male patients. Pulmonary comorbidity was present in 89.5% of the patients. The most frequent comorbidity was bronchiectasis (78.9%). Previous treatment for pulmonary tuberculosis (PTB) was found in 65.9%. The most used therapeutic regimen was rifampicin, isoniazid and ethambutol (44.7%). Chest tomography (CT) showed bronchiectasis (94.1%), architectural distortion (76.5%), septum thickening (67.6%), and cavities (64.7%). Disease was bilateral in 85.2%. We observed 10.7% resistance to rifampicin, 67.9% resistance to ethambutol, and sensitivity to clarithromycin. Conclusion In patients with structural lung disease, it is important to search for NTM, the main differential diagnosis with PTB. Chest CT showed different patterns that overlapped with structural disease caused by PTB or other lung diseases. We observed resistance to ethambutol, a drug component of the recommended regimen.

Mycobacterium kansasii arthritis of the elbow in an immunocompetent patient with a suspected soft-tissue tumor.

Mycobacterium kansasii is one of the major non-tuberculous mycobacteria species that typically cause pulmonary diseases. M. kansasii is known to cause septic arthritis as an extrapulmonary disease in immunosuppressed patients or chronic skin disease. Herein, we present a case of M. kansasii arthritis involving the elbow of an immunocompetent patient, which was initially suspected to be a soft-tissue tumor. A 70-year-old man presented with a swollen left elbow that had progressed for 18 months with deteriorating arthralgia and limited range of motion. Magnetic resonance imaging revealed filling of the intra-articular space of the elbow and surrounding of the radial head with a soft tissue mass with mixed signal intensity. Initial incisional biopsy was performed via the lateral approach to the elbow joint, and pathological examination of the mass did not reveal any evidence of malignancy. One year after the first operation, arthroscopic surgery was performed to excise the mass following the recurrence of swelling and limited function of the elbow. Pathological examination of the resected synovium revealed epithelioid granulomas containing a multinucleated giant cell and inflammatory cell infiltration, characteristic of mycobacterial infection. M. kansasii was cultured after 2 weeks of incubation of the synovial sample. He experienced full resolution of the swelling and limited function following a combination of synovectomy and multidrug antimycobacterial treatment (rifampin 600 mg/day, clarithromycin 800 mg/day, and ethambutol 750 mg/day). This case highlights the need to consider this rare infection in the differential diagnosis of intra-articular soft tissue tumor-like lesions even in immunocompetent patients.

Características clínicas e epidemiológicas de casos de infecção pulmonar por Mycobacterium kansasii no Rio de Janeiro, no período de 2006 a 2016 / Clinical and epidemiological characteristics of M. kansasii pulmonary infections from Rio de Janeiro, Brazil, between 2006 and 2016

RESUMO Objetivo Avaliar características clínicas, tomográficas e microbiológicas dos pacientes com doença pulmonar causada pela M. kansasii (DPMK) atendidos em unidade ambulatorial no período 2006-2016. Métodos Estudo descritivo, em que foram analisados 38 pacientes. Foram analisadas as características demográficas, clínico-radiológicas, laboratoriais e terapêuticas. Resultados A média de idade foi 64 anos (DP=10,6; IIQ=57-72; mediana=65,0) e 22 (57,9%) eram pacientes do sexo masculino. Comorbidade pulmonar estava presente em 89,5%. A comorbidade mais frequente foi a bronquiectasia (78,9%). Tratamento anterior para tuberculose pulmonar (TBP) foi relatado em 65,9%. O esquema terapêutico mais utilizado foi rifampicina, isoniazida e etambutol (44,7%). A tomografia de tórax (TCT) mostrou bronquiectasia (94,1%), distorção arquitetural (76,5%), espessamento de septo (67,6%) e cavidades (64,7%). A doença foi bilateral em 85,2%. Houve 10,7% de resistência à rifampicina, 67,9% resistentes ao etambutol e sensibilidade à claritromicina. Conclusão Em pacientes com doença pulmonar estrutural, é importante a busca de DPMNT, principal diagnóstico diferencial com TBP. TC de tórax demonstra diferentes padrões que se sobrepõem ao de doença estrutural causada por TBP ou outras enfermidades pulmonares. Destaca-se a resistência ao etambutol, fármaco componente do esquema preconizado.

ABSTRACT Objective To evaluate clinical, tomographic, and microbiological characteristics of pulmonary disease caused by M. kansasii (MKPD) in patients treated at an outpatient unit from 2006-2016. Methods We studied thirty eight patients, and analyzed socio-demographic, clinical-radiological, laboratory, and therapeutic characteristics. Results The mean age was 64 years (SD = 10.6; IIQ = 57-72; median = 65.0), and 22 (57.9%) male patients. Pulmonary comorbidity was present in 89.5% of the patients. The most frequent comorbidity was bronchiectasis (78.9%). Previous treatment for pulmonary tuberculosis (PTB) was found in 65.9%. The most used therapeutic regimen was rifampicin, isoniazid and ethambutol (44.7%). Chest tomography (CT) showed bronchiectasis (94.1%), architectural distortion (76.5%), septum thickening (67.6%), and cavities (64.7%). Disease was bilateral in 85.2%. We observed 10.7% resistance to rifampicin, 67.9% resistance to ethambutol, and sensitivity to clarithromycin. Conclusion In patients with structural lung disease, it is important to search for NTM, the main differential diagnosis with PTB. Chest CT showed different patterns that overlapped with structural disease caused by PTB or other lung diseases. We observed resistance to ethambutol, a drug component of the recommended regimen.

Case Report: Disseminated Mycobacterium kansasii Disease in a Patient with Anti-Interferon-Gamma Antibody.

Disseminated nontuberculous mycobacterial (NTM) infections usually occur in severely immunosuppressed patients. These infections may also occur in previously immunocompetent patients with acquired anti-interferon-gamma antibodies (anti-IFN-γ Abs). A previously healthy 33-year-old man presented with a 3-week history of cough and fever. Chest computed tomography showed air-space consolidation in the middle lobe of the right lung and enlargement of the supraclavicular, mediastinal, and hilar lymph nodes. Tissue samples obtained via mediastinoscopy showed granuloma formation with acid-fast bacteria; cultures from the tissue revealed Mycobacterium kansasii. Accordingly, a diagnosis of disseminated M. kansasii disease was made. The positive control tested negative in the QuantiFERON-TB Gold In-tube test, suggesting the presence of anti-IFN-γ Abs. The ELISA test for anti-IFN-γ Abs demonstrated an increased titer. Antimycobacterial drug treatments were initiated after diagnosis. His symptoms improved over 2 months, and he remains well on outpatient management. Disseminated M. kansasii disease is a very rare condition suggestive of immunosuppression. Testing for anti-IFN-γ antibodies might be important in all cases of disseminated M. kansasii disease.

Interrelational changes in the epidemiology and clinical features of nontuberculous mycobacterial pulmonary disease and tuberculosis in a referral hospital in Japan.

BACKGROUND AND OBJECTIVES: The incidence of nontuberculous mycobacterial pulmonary disease (NTM-PD) is increasing, while that of tuberculosis (TB) is decreasing in many industrialized countries, including Japan. However, the long-term evaluation of clinico-epidemiological features of NTM-PD in relation to TB are limited. We aimed to clarify the long-term changes in the epidemiology and clinical features of NTM-PD in relation to those of TB at a nationally-designated TB center in Japan. METHODS: We reviewed all mycobacterial examination records at Fukujuji Hospital between 2006 and 2016. Cases of NTM-PD were defined according to the 2007 American Thoracic Society/Infectious Disease Society of America microbiologic criteria. The current characteristics of Mycobacterium avium complex pulmonary disease (MAC-PD) were compared with those in the 1980s and circa 2000. RESULTS: We identified a total of 3,546 pulmonary TB cases and 2,155 NTM-PD cases. While the annual number of incident pulmonary TB cases remained stable over the study period (P = 0.59), that of NTM-PD cases increased significantly from 165 to 278 (P < 0.01). The mean age of pulmonary TB cases increased from 59.7 ±â€¯16.3 to 66.2 ±â€¯21.7 years, whereas that of NTM-PD cases remained unchanged. Regarding the age distribution, the greatest increases were observed in patients over 75 years for TB and in patients 50-74 years for NTM. The most common causative organism for NTM was Mycobacterium avium complex (87.3%), M. abscessus complex (5.5%) and M. kansasii (3.9%). Among patients with MAC-PD, the proportion of the nodular bronchiectatic (NB) form increased significantly from 60.0% to 84.4% between circa 2000 and 2016 (P < 0.01). Significant increases in the NB form were observed in both males (33.3%-70.7%, P < 0.01) and females (71.3%-89.2%, P < 0.01). CONCLUSIONS: The annual number of incident NTM-PD cases increased markedly. In contrast to patients with TB, the mean age of new NTM-PD patients did not increase in the last 10 years. Among MAC-PD patients, the proportions accounted for by the NB form increased significantly in both sexes.

GATA2 mutation in long stand Mycobacterium kansasii infection, myelodysplasia and MonoMAC syndrome: a case-report.

BACKGROUND: GATA2 is a transcription factor that is a critical regulator of gene expression in hematopoietic cells. GATA2 deficiency presents with multi-lineage cytopenia, mycobacterial, fungal and viral infections. Patients with GATA2 mutation have a high risk of developing myelodysplastic syndrome or acute myeloid leukemia. CASE PRESENTATION: We described a 43 years-old white male with 20-year follow-up of autoimmune and thrombotic phenomena, hypothyroidism, disseminated refractory Mycobacterium kansasii infection and MonoMAC syndrome. GATA2 c.1061 C > T; p.T354 M mutation was identified after he progressed from myelodysplastic pancytopenia to refractory anemia with excess blasts type II. His relatives were also investigated and he underwent unsuccessful haematopoietic stem cell transplantation. We discuss the clinical features, genetic diagnosis and treatment of this immunodeficiency disorder. CONCLUSIONS: This case illustrates the challenge how a multidisciplinary disease should be handle. Once usual causes of immunodeficiency were excluded, clinicians should considerGATA2 deficiency in patients with myelodysplasia and long-standing Mycobacterium kansasii infection.

Treatment with a macrolide-containing regimen for Mycobacterium kansasii pulmonary disease.

BACKGROUND: Mycobacterium kansasii is a major pathogen associated with nontuberculous mycobacterial pulmonary disease. For treatment of M. kansasii pulmonary disease, daily therapy with isoniazid, rifampin, and ethambutol is traditionally recommended. Although a regimen containing a macrolide, instead of isoniazid, has been recently recommended, supporting data are limited. We compared the treatment outcomes of a macrolide-containing regimen (macrolide group) and an isoniazid-containing regimen (isoniazid group) on patients with M. kansasii pulmonary disease. METHODS: A total of 49 patients were identified between January 2002 and December 2016. Treatment outcomes for the isoniazid group (n = 24) and the macrolide group (n = 25) were compared. RESULTS: Baseline characteristics of the isoniazid and macrolide groups were similar. Favorable outcomes did not differ between the isoniazid group (79%, n = 19) and macrolide group (88%, n = 22, P = 0.463). Total treatment duration (median 17.9 months vs. 15.4 months; P = 0.712) and time to culture conversion (median 2.0 months vs. 1.2 months; P = 0.838) were also similar between the isoniazid and macrolide groups. Five patients who completed three-times-weekly intermittent treatment containing a macrolide for non-cavitary M. kansasii pulmonary disease achieved negative sputum culture conversion within 12 months of treatment. Only one patient experienced recurrence of M. kansasii pulmonary disease in the isoniazid group. CONCLUSIONS: A macrolide-containing regimen appears to be as effective as an isoniazid-containing regimen for treatment of M. kansasii pulmonary disease. Additionally, intermittent therapy containing a macrolide could be an alternative treatment option for non-cavitary M. kansasii pulmonary disease.

Multicenter evaluation of the biochip assay for rapid detection of mycobacterial isolates in smear-positive specimens.

OBJECTIVES: The objective of this study was to conduct a multicentre evaluation of the performance of the biochip assay in the rapid identification of mycobacteria in smear-positive sputum specimens. METHODS: A total of 1751 sputum specimens were obtained from 7 cities in Zhejiang, China. All of the specimens were used for the discrimination of Mycobacterium species using the biochip assay, and the results were compared to the golden standard method of culture, hsp65, 16S rRNA and rpoB sequence analysis. RESULTS: In the 1751 sputum specimens, 1685 samples were cultured successfully; among these samples, 1361 were Mycobacterium tuberculosis, 323 were NTM and 1 was Nocadia farcinica. Of the 323 NTM, most of them were Mycobacterium intracellulare(52.5%) followed by Mycobacterium abscessus (20.7%), Mycobacterium avium (11.7%), Mycobacterium kansasii (9.6%) and Mycobacterium fortuitum (1.9%). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the biochip assay to differentiate TB and NTM from AFB positive specimens were 99.8%, 99.7%, 99.9%, 99.1%, 98.8%, 1, 1, and 99.7%, respectively. The concordance between the biochip assay and mycobacterial culture for the identification of NTM species was 95.4%. CONCLUSIONS: The biochip assay is a reliable tool for the rapid identification of most mycobacteria in clinical sputum specimens. This assay can be helpful for physicians in the early diagnosis and treatment of mycobacterium infections.

Double lung transplantation in an HIV-positive patient with Mycobacterium kansasii infection.

Good outcomes with kidney and liver transplantation in HIV-positive patients have led clinicians to recommend lung transplantation in HIV-positive patients based on extrapolated data. Pre-transplant mycobacterial infection is associated with an increased risk of developing new infection or aggravating existing infection, though it does not contraindicate transplantation in non-HIV-infected patients. However, no data exists regarding the outcome of HIV-positive patients with pre-transplant mycobacterial infection. We report a case of double lung transplantation in a 50-year-old HIV-positive patient with alpha-1 antitrypsin deficiency. Prior to transplantation, Mycobacterium kansasii was isolated in one sputum culture and the patient was considered merely colonized as no clinical evidence of pulmonary or disseminated disease was present. The patient successfully underwent a double lung transplantation. Nontuberculous mycobacterial infection was diagnosed histologically on examination of native lungs. Surveillance and watchful waiting were chosen over treatment of the infection. HIV remained under control post-transplantation with no AIDS-defining illnesses throughout the follow-up. A minimal acute rejection that responded to increased corticosteroids was reported. At 12 months post-transplant, a bronchiolitis obliterans syndrome was diagnosed after a drop in FEV1. No evidence of isolation nor recurrence of nontuberculous mycobacteria was reported post-transplantation. At 15 months post-transplant, the patient remained stable with an FEV1 of 30%. The presence of pre-transplant nontuberculous mycobacterial infection did not translate into recurrence of nontuberculous mycobacterial infection post-transplant. Whether it contributed to bronchiolitis obliterans syndrome remains unknown.

Predictors of developing Mycobacterium kansasii pulmonary disease within 1 year among patients with single isolation in multiple sputum samples: A retrospective, longitudinal, multicentre study.

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.

Whole genome sequence of Mycobacterium kansasii isolates of the genotype 1 from Brazilian patients with pulmonary disease demonstrates considerable heterogeneity.

Mycobacterium kansasii is an opportunistic pathogen and one of the most commonly encountered species in individuals with lung disease. We here report the complete genome sequence of 12 clinical isolates of M. kansasii from patients with pulmonary disease in Brazil.

Clinical, radiological and molecular features of Mycobacterium kansasii pulmonary disease.

BACKGROUND: Studies concerning sociodemographic, clinical, and laboratory features of Mycobacterium kansasii pulmonary disease are few and based on small patient cohorts. The objective of the study was to evaluate characteristics of patients from whom M. kansasii respiratory isolates were recovered and to provide a detailed description of M. kansasii disease. BASIC PROCEDURES: Retrospective review of electronic medical records of all patients for whom at least one positive M. kansasii culture was obtained at the Department of Internal Medicine, Pulmonology and Allergology of the Warsaw Medical University between the year 2000 and 2015. Patients were categorized as having mycobacterial disease or as isolation cases based on the American Thoracic Society and Infectious Diseases Society of America (ATS/IDSA) diagnostic criteria. MAIN FINDINGS: The study comprised of 105 patients (63 females, 42 males, mean age 64.6 ±â€¯17.8 years). Of these, 86 (81.9%) were diagnosed as having M. kansasii disease. The proportion of positive smear microscopy was significantly higher in patients with M. kansasii disease compared to M. kansasii isolation (P < 0.001). There were no statistically significant differences between M. kansasii disease and isolation cases in terms of clinical symptoms or comorbidities. Patients with M. kansasii disease presented most commonly (43/86, 50%) fibro-cavitary disease upon radiology. Lesion distribution usually showed bilateral upper lobe involvement. Among the 191 isolates genotyped, all were identified as M. kansasii type I. PRINCIPAL CONCLUSIONS: The findings from this study support the relaxation of the diagnostic criteria for the definition of M. kansasii disease, set forth by ATS/IDSA. Molecular typing did not differentiate isolates from patients with true disease from those with isolation only; the role of bacterial virulence factors thus remains elusive.