Pulmonary Mycobacterium kansasii infection: comparison of radiological appearances with pulmonary tuberculosis

Comprehensive essentiality analysis of the Mycobacterium kansasii genome by saturation transposon mutagenesis and deep sequencing

Mycobacterium kansasii (Mk) is an opportunistic pathogen that is frequently isolated from urban water systems, posing a health risk to susceptible individuals. Despite its ability to cause tuberculosis-like pulmonary disease, very few studies have probed the genetics of this opportunistic pathogen. Here, we report a comprehensive essentiality analysis of the Mk genome. Deep sequencing of a high-density library of Mk Himar1 transposon mutants revealed that 86.8% of the chromosomal thymine-adenine (TA) dinucleotide target sites were permissive to insertion, leaving 13.2% TA sites unoccupied. Our analysis identified 394 of the 5,350 annotated open reading frames (ORFs) as essential. The majority of these essential ORFs (84.8%) share essential mutual orthologs with Mycobacterium tuberculosis (Mtb). A comparative genomics analysis identified 139 Mk essential ORFs that share essential orthologs in four other species of mycobacteria. Thirteen Mk essential ORFs share orthologs in all four species that were identified as being not essential, while only two Mk essential ORFs are absent in all species compared. We used the essentiality data and a comparative genomics analysis reported here to highlight differences in essentiality between candidate Mtb drug targets and the corresponding Mk orthologs. Our findings suggest that the Mk genome encodes redundant or additional pathways that may confound validation of potential Mtb drugs and drug target candidates against the opportunistic pathogen. Additionally, we identified 57 intergenic regions containing four or more consecutive unoccupied TA sites. A disproportionally large number of these regions were located upstream of pe/ppe genes. Finally, we present an essentiality and orthology analysis of the Mk pRAW-like plasmid, pMK1248. IMPORTANCE Mk is one of the most common nontuberculous mycobacterial pathogens associated with tuberculosis-like pulmonary disease. Drug resistance emergence is a threat to the control of Mk infections, which already requires long-term, multidrug courses. A comprehensive understanding of Mk biology is critical to facilitate the development of new and more efficacious therapeutics against Mk. We combined transposon-based mutagenesis with analysis of insertion site identification data to uncover genes and other genomic regions required for Mk growth. We also compared the gene essentiality data set of Mk to those available for several other mycobacteria. This analysis highlighted key similarities and differences in the biology of Mk compared to these other species. Altogether, the genome-wide essentiality information generated and the results of the cross-species comparative genomics analysis represent valuable resources to assist the process of identifying and prioritizing potential Mk drug target candidates and to guide future studies on Mk biology.

A Comparison of Clinical and Radiographic Signs of Nontuberculous Mycobacterial Pulmonary Disease, Destructive Drug-Resistant Pulmonary Tuberculosis and a Combination of Nontuberculous Mycobacterium Pulmonary Disease and Pulmonary Tuberculosis

A misdiagnosis of isolated pulmonary tuberculosis (pTB) is highly likely when a patient has nontuberculous mycobacterial pulmonary disease (NTMPD) or a combination of nontuberculous mycobacterium pulmonary disease and pulmonary tuberculosis. Frequently, bacterial excretion is absent or only Mycobacteria tuberculosis (MBT) is found. This often results in an incorrect diagnosis and subsequent misinformed treatment regimes. In order to determine possible clinical and radiographic differences between patients with NTMPD (Group 1), destructive drug-resistant pulmonary tuberculosis (Group 3) and a combination of NTMPD and pTB (Group 2) we compare clinical and radiographic signs for these three patient groups. When comparing with Group 3 (2.5%), Groups 1 (25%) and 2 (17.4%) have a substantially higher incidence of pulmonary haemorrhages. Thus, upon clinically observing the combination of pTB and NTMPD, there are no pathognomonic clinical and radiographic detected symptoms. However, the presence of an indolent course, hemoptysis and bronchiectasis in the presence of acid-fast bacteria (or identified MBT) in the sputum makes it possible to suspect not simple pTB, but a combination of pTB and NTMPD. To clarify this necessitated in-depth bacteriological examination.

Genetic Underpinnings of Carotenogenesis and Light-Induced Transcriptome Remodeling in the Opportunistic Pathogen Mycobacterium kansasii

Mycobacterium kansasii (Mk) causes opportunistic pulmonary infections with tuberculosis-like features. The bacterium is well known for its photochromogenicity, i.e., the production of carotenoid pigments in response to light. The genetics defining the photochromogenic phenotype of Mk has not been investigated and defined pigmentation mutants to facilitate studies on the role of carotenes in the bacterium's biology are not available thus far. In this study, we set out to identify genetic determinants involved in Mk photochromogenicity. We screened a library of ~150,000 transposon mutants for colonies with pigmentation abnormalities. The screen rendered a collection of ~200 mutants. Each of these mutants could be assigned to one of four distinct phenotypic groups. The insertion sites in the mutant collection clustered in three chromosomal regions. A combination of phenotypic analysis, sequence bioinformatics, and gene expression studies linked these regions to carotene biosynthesis, carotene degradation, and monounsaturated fatty acid biosynthesis. Furthermore, introduction of the identified carotenoid biosynthetic gene cluster into non-pigmented Mycobacterium smegmatis endowed the bacterium with photochromogenicity. The studies also led to identification of MarR-type and TetR/AcrR-type regulators controlling photochromogenicity and carotenoid breakdown, respectively. Lastly, the work presented also provides a first insight into the Mk transcriptome changes in response to light.

Drug susceptibility profiling of pulmonary Mycobacterium kansasii and its correlation with treatment outcome

OBJECTIVES:

With the introduction of newer molecular diagnostic tools to identify Mycobacterium tuberculosis, an increasing number of nontuberculous mycobacterium (NTM) is being identified. However, the drug resistance pattern of the NTM species identified is less explored. The objective of this study is to study the drug resistance patterns of Mycobacterium kansasii species isolated in a tuberculosis-endemic setting at South India.

METHODS:

A wide profile of NTM species were reported earlier from a prospective cohort of adults during 2017–2020. Out of this profile, a total of 22 M. kansasii species were subjected to drug susceptibility testing by two different methods: proportion sensitivity testing method and Sensititre testing method.

RESULTS:

Out of the 18 strains of M. kansasii subjected to Sensititre method of testing, the resistance pattern was demonstrated to be high for doxycycline (13) followed by rifampicin and trimethoprim/sulfamethoxazole (7). Out of the 22 strains subjected to proportion sensitivity testing method, 20 and 10 were resistant to isoniazid and ethambutol, respectively.

CONCLUSION:

There was a poor correlation between the treatment outcome and the resistance pattern of the antibiotics tested. With increasing numbers of NTM being reported, early and correct identification of NTM species is essential for the prompt initiation of appropriate treatment to achieve better outcome.

Safety and Efficacy of Nontuberculous Mycobacteria Treatment among Elderly Patients

Background and objectives: Incidence rates of pulmonary nontuberculous mycobacterial (NTM) disease have been increasing, especially in the elderly population. Given the limited evidence regarding the safety and efficacy of NTM treatment, this study aimed to evaluate the same among elderly patients. Material and methods: Patients diagnosed with NTM disease at a tertiary hospital from January 2007 to December 2017 were enrolled and data were then retrospectively collected. Data of elderly patients who received antimycobacterial treatment were then analyzed. Results: A total of 161 patients satisfied the diagnostic criteria for NTM disease. There were 40 elderly patients who received treatments. Of the patients, 60% received the guideline oriented standard regimens. Single drug regimens were administered to 22.5% of patients. Only 55.0% of the patients were able to continue any treatment. Treatment-related discontinuation was observed in 44.4% of discontinued or changed patients. There were no significant differences in the characteristics of patients with or without adverse events. Patients who were able to continue the treatment for >12 months had a lower proportion of activities of daily living (ADL) disability (nine in 18, 50.0% vs. three in 22, 13.6%, p = 0.018) and heart disease (six in 18, 33.3% vs. 1/22, 4.6%, p = 0.033). Sputum culture conversion was achieved in 28 out of 40 (70.0%) elderly patients treated, and those who achieved sputum culture conversion had more standard regimens prescribed than those who failed sputum culture conversion (21 in 28, 75% vs. 3 in 12, 25%; p = 0.005). Conclusion: Age may not be an obstacle for receiving the benefits of the treatment of NTM disease with a precise evaluation of patient's comorbidities. Furthermore, elderly patients without heart disease and ADL disability may have better rate of continuing the NTM treatment. The current study suggested that selecting standard regimens to treat pulmonary NTM is important for elderly patients.

General Overview of Nontuberculous Mycobacteria Opportunistic Pathogens: Mycobacterium avium and Mycobacterium abscessus

Nontuberculous mycobacteria (NTM) are emerging human pathogens, causing a wide range of clinical diseases affecting individuals who are immunocompromised and who have underlying health conditions. NTM are ubiquitous in the environment, with certain species causing opportunistic infection in humans, including Mycobacterium avium and Mycobacterium abscessus. The incidence and prevalence of NTM infections are rising globally, especially in developed countries with declining incidence rates of M. tuberculosis infection. Mycobacterium avium, a slow-growing mycobacterium, is associated with Mycobacterium avium complex (MAC) infections that can cause chronic pulmonary disease, disseminated disease, as well as lymphadenitis. M. abscessus infections are considered one of the most antibiotic-resistant mycobacteria and are associated with pulmonary disease, especially cystic fibrosis, as well as contaminated traumatic skin wounds, postsurgical soft tissue infections, and healthcare-associated infections (HAI). Clinical manifestations of diseases depend on the interaction of the host’s immune response and the specific mycobacterial species. This review will give a general overview of the general characteristics, vulnerable populations most at risk, pathogenesis, treatment, and prevention for infections caused by Mycobacterium avium, in the context of MAC, and M. abscessus.

Transposon mutagenesis in Mycobacterium kansasii links a small RNA gene to colony morphology and biofilm formation and identifies 9,885 intragenic insertions that do not compromise colony outgrowth

Mycobacterium kansasii (Mk) is a resilient opportunistic human pathogen that causes tuberculosis‐like chronic pulmonary disease and mortality stemming from comorbidities and treatment failure. The standard treatment of Mk infections requires costly, long‐term, multidrug courses with adverse side effects. The emergence of drug‐resistant isolates further complicates the already challenging drug therapy regimens and threatens to compromise the future control of Mk infections. Despite the increasingly recognized global burden of Mk infections, the biology of this opportunistic pathogen remains essentially unexplored. In particular, studies reporting gene function or generation of defined mutants are scarce. Moreover, no transposon (Tn) mutagenesis tool has been validated for use in Mk, a situation limiting the repertoire of genetic approaches available to accelerate the dissection of gene function and the generation of gene knockout mutants in this poorly characterized pathogen. In this study, we validated the functionality of a powerful Tn mutagenesis tool in Mk and used this tool in conjunction with a forward genetic screen to establish a previously unrecognized role of a conserved mycobacterial small RNA gene of unknown function in colony morphology features and biofilm formation. We also combined Tn mutagenesis with next‐generation sequencing to identify 12,071 Tn insertions that do not compromise viability in vitro. Finally, we demonstrated the susceptibility of the Galleria mellonella larva to Mk, setting the stage for further exploration of this simple and economical infection model system to the study of this pathogen.

Risk factors for developing Mycobacterium kansasii lung disease: A case-control study in Korea

Previous studies have suggested that development of Mycobacterium kansasii lung disease (MKLD) was associated with COPD, pneumoconiosis, aging, male, immunosuppression, alcohol, malignancy, and certain occupations such as mining and sandblasting. However, previous studies were outdated and used non-comparative statistical methods. We aimed to determine the current risk factors for developing MKLD in Korea by using appropriate statistical techniques.Eighty-six MKLD patients were identified through a search of the Ulsan University Hospital database between January 2010 and December 2014. These cases were matched with 172 controls who had normal respiratory systems in a health examination during the same period (matching variables, age and sex; case: control ratio of 1:2). Clinical and demographic characteristics were gathered by reviewing the medical record and telephone survey. Multivariate logistic regression analyses were performed to evaluate risk factors for developing MKLD.Multivariate analysis showed that occupation in heavy industries (adjusted odds ratio (aOR) 6.41, 95% confidence interval (CI) 2.19-18.74, P = .001) and low body mass index (BMI) (aOR [per kg/m] 0.73, 95% CI 0.63-0.85, P < .001) were independent risk factors for development of MKLD. Educational attainment more than high school was associated with a lower risk of MKLD development (aOR 0.22, 95% CI 0.08-0.63, P = .005).Employees in heavy industry and low BMI are independent risk factors for development of MKLD in Korea.

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.

Laryngeal Inflammatory Pseudotumour Secondary to Mycobacterium kansasii

BACKGROUND

Inflammatory pseudotumours (IPT) are rare benign tumours characterised by spindle-shaped histiocyte proliferation often mimicking a soft tissue sarcoma. They can occur in different parts of the body and various aetiological factors have been proposed. To our knowledge this is the first case report of IPT of the larynx caused by mycobacterial disease.

CASE REPORT

We report a case of IPT of the larynx in an immunocompromised 81-year-old lady presenting with stridor and dysphagia with known disseminated Mycobacterium kansasii of the lungs.

CONCLUSION

This case demonstrates both the clinical and histological difficulties in making the diagnosis of IPT. A high index of suspicion is needed, and the importance of a multidisciplinary approach in the work-up, diagnosis, and management is highlighted.

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 ± 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.

Mycobacterium kansasii

The incidence of Mycobacterium kansasii varies widely over time and by region, but this organism remains one of the most clinically relevant isolated species of nontuberculous mycobacteria. In contrast to other common nontuberculous mycobacteria, M. kansasii is infrequently isolated from natural water sources or soil. The major reservoir appears to be tap water. Infection is likely acquired through the aerosol route, with low infectivity in regions of endemicity. Human-to-human transmission is thought not to occur. Clinical syndromes and radiological findings of M. kansasii infection are mostly indistinguishable from that of Mycobacterium tuberculosis, thus requiring microbiological confirmation. Disseminated disease is uncommon in HIV-negative patients and usually associated with severe immunosuppression. The majority of patients with M. kansasii pulmonary disease have underlying pulmonary comorbidities, such as smoking, chronic obstructive pulmonary disease, bronchiectasis, and prior or concurrent M. tuberculosis infection. Surveys in Great Britain, however, noted higher rates, with 8 to 9% of M. kansasii infections presenting with extrapulmonary disease. Common sites of extrapulmonary disease include the lymph nodes, skin, and musculoskeletal and genitourinary systems. The specificity of gamma interferon release assays (IGRAs) for M. tuberculosis may be reduced by M. kansasii infection, as M. kansasii encodes CFP-10 and ESAT-6, two antigens targeted by IGRAs. A study conducted to evaluate the therapy in rifampin-resistant disease found that patients with acquired rifampin resistance were treated with daily high-dose ethambutol, isoniazid, sulfamethoxazole, and pyridoxine combined with aminoglycoside therapy. Given the potential toxicities, particularly with aminoglycoside therapy, clarithromycin and/or moxifloxacin therapy could be considered as alternatives.

Insights on the emergence of Mycobacterium tuberculosis from the analysis of Mycobacterium kansasii

By phylogenetic analysis, Mycobacterium kansasii is closely related to Mycobacterium tuberculosis. Yet, although both organisms cause pulmonary disease, M. tuberculosis is a global health menace, whereas M. kansasii is an opportunistic pathogen. To illuminate the differences between these organisms, we have sequenced the genome of M. kansasii ATCC 12478 and its plasmid (pMK12478) and conducted side-by-side in vitro and in vivo investigations of these two organisms. The M. kansasii genome is 6,432,277 bp, more than 2 Mb longer than that of M. tuberculosis H37Rv, and the plasmid contains 144,951 bp. Pairwise comparisons reveal conserved and discordant genes and genomic regions. A notable example of genomic conservation is the virulence locus ESX-1, which is intact and functional in the low-virulence M. kansasii, potentially mediating phagosomal disruption. Differences between these organisms include a decreased predicted metabolic capacity, an increased proportion of toxin–antitoxin genes, and the acquisition of M. tuberculosis-specific genes in the pathogen since their common ancestor. Consistent with their distinct epidemiologic profiles, following infection of C57BL/6 mice, M. kansasii counts increased by less than 10-fold over 6 weeks, whereas M. tuberculosis counts increased by over 10,000-fold in just 3 weeks. Together, these data suggest that M. kansasii can serve as an image of the environmental ancestor of M. tuberculosis before its emergence as a professional pathogen, and can be used as a model organism to study the switch from an environmental opportunistic pathogen to a professional host-restricted pathogen.

Other HIV-associated pneumonias

The incidence, mortality, and epidemiology of human immunodeficiency virus (HIV)-associated pulmonary infections have changed as a result of effective antiretroviral and prophylaxis antimicrobial therapy. The clinical presentation, radiographic abnormalities, and treatment of pneumonia from various uncommon pathogens in patients with AIDS can be different from those in immunocompetent patients. Advances in invasive and noninvasive testing and molecular biological techniques have improved the diagnosis and prognosis of pulmonary infections in patients infected with HIV. This review focuses on pulmonary infections from nontuberculosis mycobacteria, cytomegalovirus, fungi (aspergillosis, cryptococcosis, endemic fungi), and parasites (toxoplasmosis), and uncommon bacterial pneumonia (nocardiosis, rhodococcosis) in these patients.

Activation of an NLRP3 inflammasome restricts Mycobacterium kansasii infection

Mycobacterium kansasii has emerged as an important nontuberculous mycobacterium pathogen, whose incidence and prevalence have been increasing in the last decade. M. kansasii can cause pulmonary tuberculosis clinically and radiographically indistinguishable from that caused by Mycobacterium tuberculosis infection. Unlike the widely-studied M. tuberculosis, little is known about the innate immune response against M. kansasii infection. Although inflammasome activation plays an important role in host defense against bacterial infection, its role against atypical mycobacteria remains poorly understood. In this report, the role of inflammasome activity in THP-1 macrophages against M. kansasii infection was studied. Results indicated that viable, but not heat-killed, M. kansasii induced caspase-1-dependent IL-1β secretion in macrophages. The underlying mechanism was found to be through activation of an inflammasome containing the NLR (Nod-like receptor) family member NLRP3 and the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD). Further, potassium efflux, lysosomal acidification, ROS production and cathepsin B release played a role in M. kansasii-induced inflammasome activation. Finally, the secreted IL-1β derived from caspase-1 activation was shown to restrict intracellular M. kansasii. These findings demonstrate a biological role for the NLRP3 inflammasome in host defense against M. kansasii.

Mycobacterium kansasii pulmonary infection: CT findings in 29 cases

PURPOSE

Our aim was to assess computed tomography (CT) features of Mycobacterium kansasii pulmonary infection (M. kansasii infection).

MATERIALS AND METHODS

A total of 29 cases confirmed to have M. kansasii infections were analyzed. The main locations of pulmonary changes, incidence, and various imaging features of the cavity (location, maximum diameter, wall thickness, satellite nodules, intracavitary fluid), and other imaging findings such as nodules, consolidation, and bronchiectasis, were visually assessed on CT images.

RESULTS

Locations of the main abnormalities were as follows: right S2 41%; right S1 31%; left S1+S2 2: 21%. A total of 49 cavities were observed in 24 (83%) cases. The mean maximum diameter, wall thickness, and ratio of wall thickness to the maximum diameter were 33.0 mm, 4.7 mm, and 0.19, respectively. Shapes of the cavities were round in nine (18.4%), oval in 17 (34.7%), and tubular/meandering in 23 (47%). Satellite nodules were found in only 30.6% of patients (n = 15). Small nodules were found in 26 (89.7%) patients, and most of them showed a centrilobular distribution.

CONCLUSION

The characteristic CT findings suggestive of M. kansasii infection include cavities located in the right posterior or apical segment with a tubular/meandering shape and a thin wall.

Mycobacterial infections in a large Virginia hospital, 2001-2009

Background

In areas where both tuberculosis (TB) and nontuberculous mycobacteria (NTM) are prevalent, descriptive studies of the clinical features of individual mycobacteria are needed to inform clinical triage.

Methods

We queried the University of Virginia Clinical Data Repository for all mycobacterial infections from 2001-2009.

Results

Of 494 mycobacterial infections in 467 patients there were 22 species. Patients with pulmonary Tb were more likely to be reported as immigrants (p < 0.001) and less likely to have a predisposing risk factor for NTM (pre-existing lung disease or host predisposition; p = 0.002). Review of chest CT scans revealed that TB infection was more likely to exhibit cavities and pleural effusion than NTM infection (p < 0.05). Among NTM infections M. kansasii, M. xenopi, and M. fortuitum were more likely than MAC to have cavities. There were at least 83 patients that met criteria for NTM lung disease and these were caused by 9 species. M. abscessus infection was associated with cystic fibrosis and M. xenopi infection was associated with male gender.

Conclusions

In our center mycobacterial infections were common and of diverse species. Immigrant status, cavities, and effusion were associated with TB vs. NTM.

Clinical characteristics and treatment outcomes of Mycobacterium kansasii lung disease in Korea

PURPOSE

While Mycobacterium kansasii is a common cause of nontuberculous mycobacterial (NTM) lung disease in many developed countries, M. kansasii is infrequently isolated in Korea. We investigated the clinical and radiological features and treatment outcomes of M. kansasii lung disease in Korea retrospectively.

MATERIALS AND METHODS

We identified 41 patients with M. kansasii lung disease who met the diagnostic criteria for NTM lung disease in two tertiary referral hospitals in Seoul, Korea, between January 1998 and December 2007.

RESULTS

Their median age was 63 years [interquartile range (IQR) 51-75 years] and 33 (81%) were men. Twenty-three patients (56%) were smokers and 13 patients (32%) had previous pulmonary tuberculosis. The most common radiographic findings were nodules (n = 22, 54%) and consolidation (n = 22, 54%). Cavitation was present in 13 patients (32%). Thirty-one patients (76%) were treated with isoniazid, rifampin, and ethambutol. The median treatment duration was 16 months (IQR 9-18 months). The negative conversion rate after 12 months of treatment was 95%.

CONCLUSION

Clinicians should be aware of the various radiographic manifestations of M. kansasii lung disease. With appropriate treatment, these patients have a good prognosis.

Amoebal pathogens as emerging causal agents of pneumonia

Despite using modern microbiological diagnostic approaches, the aetiological agents of pneumonia remain unidentified in about 50% of cases. Some bacteria that grow poorly or not at all in axenic media used in routine clinical bacteriology laboratory but which can develop inside amoebae may be the agents of these lower respiratory tract infections (RTIs) of unexplained aetiology. Such amoebae-resisting bacteria, which coevolved with amoebae to resist their microbicidal machinery, may have developed virulence traits that help them survive within human macrophages, i.e. the first line of innate immune defence in the lung. We review here the current evidence for the emerging pathogenic role of various amoebae-resisting microorganisms as agents of RTIs in humans. Specifically, we discuss the emerging pathogenic roles of Legionella-like amoebal pathogens, novel Chlamydiae (Parachlamydia acanthamoebae, Simkania negevensis), waterborne mycobacteria and Bradyrhizobiaceae (Bosea and Afipia spp.).

Detailed analysis of the radiographic presentation of Mycobacterium kansasii lung disease in patients with HIV infection

BACKGROUND

Published criteria for the diagnosis of Mycobacterium kansasii lung disease require the presence of clinical symptoms, positive microbiologic results, and radiographic abnormalities. In patients with HIV infection, the radiographic findings of M kansasii lung disease are not well described.

METHODS

Medical records and chest radiographs of all patients with HIV infection and at least one respiratory specimen culture positive for M kansasii at San Francisco General Hospital between December 1989 and July 2002 were reviewed.

RESULTS

Chest radiographic results were abnormal in 75 of 83 patients (90%) included in the study. Radiographic abnormalities were diverse, with consolidation (66%) and nodules (42%) as the most frequent findings. The mid or lower lung zones were involved in 89% of patients. The pattern of radiographic abnormalities did not differ based on acid-fast bacilli smear status, the presence or absence of coexisting pulmonary infections, or CD4+ T-lymphocyte count. In multivariate Cox regression analysis, cavitation was the only radiographic abnormality independently associated with mortality (hazard ratio, 4.8; 95% confidence interval, 1.2 to 19.6).

CONCLUSION

Patients with HIV infection and M kansasii lung disease present with diverse radiographic patterns, most commonly consolidation and nodules predominantly located in the mid and lower lung zones. This finding is in contrast to the upper-lobe cavitary presentation described in patients without HIV infection. Although rare, the presence of cavitary disease in patients with HIV infection and M kansasii independently predicts worse outcome. The diversity in the radiographic presentation of M kansasii lung disease implies that clinicians should obtain sputum mycobacterial culture samples from any patient with HIV infection and an abnormal chest radiograph finding.

Differentiation of Mycobacterium kansasii infection from Mycobacterium tuberculosis infection: comparison of clinical features, radiological appearance, and outcome

This retrospective study sought to systematically identify clinical and radiological features differentiating Mycobacterium kansasii from Mycobacterium tuberculosis infection. The sample included matched patients with a culture-positive diagnosis of M. tuberculosis infection (n = 121) or M. kansasii infection (n = 62) derived from the databases of two tuberculosis centers. Data on patient background and clinical features were collected, and chest radiographs were analyzed. Sixty percent of the M. kansasii group were native Israelis compared to 15% of the M. tuberculosis group (p = 0.0001). M. tuberculosis infection was associated with a higher rate of human immunodeficiency virus (HIV) infection (p = 0.03) and M. kansasii infection with a higher rate of lung disease (p = 0.0001). M. tuberculosis infection was characterized by a higher likelihood of bilateral disease (p = 0.005), pleural effusions, and lymphadenopathy (p = 0.006 and p = 0.001, respectively). There were ten deaths, all in the M. tuberculosis group. On multivariate logistic regression, the presence of chronic obstructive pulmonary disease and associated lung disease were significant predictors of M. kansasii infection. The findings show that there are group differences between the clinical features of the two infections. In the setting of pulmonary mycobacterial infection, the presence of coinfection with HIV, bilateral disease, pleural effusion, and lymphadenopathy make M. kansasii infection very unlikely.

Assessment of cross-reactivity between Mycobacterium bovis and M. kansasii ESAT-6 and CFP-10 at the T-cell epitope level

Cross-reactivity between Mycobacterium kansasii ESAT-6 and CFP-10 homologues and their M. bovis counterparts can confound the interpretation of immunodiagnostic tests for tuberculosis. M. kansasii is a nontuberculous mycobacterial species cultured from skin test-positive cattle in Great Britain. Using peptides derived from M. bovis and M. kansasii ESAT-6 and CFP-10 regions that differ between these species, we investigated the species specificity and cross-reactivity at the level of individual bovine T-cell epitopes. Our results demonstrated that all peptides tested are fully cross-reactive, with the exception of one ESAT-6-derived peptide that harbored an M. bovis-specific epitope(s) when it was recognized in the context of bovine leukocyte antigen (BoLA)-DQ but that was cross-reactive with its M. kansasii homologues when it was restricted by BoLA-DR. This observation further highlights that prediction of species specificity by comparing sequence identity/homology alone is not sufficient and that individuals with diverse major histocompatibility complex constellations need to be tested to characterize the cross-reactivity or species specificity of peptide-based reagents.

Immune responses to defined antigens of Mycobacterium bovis in cattle experimentally infected with Mycobacterium kansasii

Cross-reactive responses elicited by exposure to nontuberculous mycobacteria often confound the interpretation of antemortem tests for Mycobacterium bovis infection of cattle. The use of specific proteins (e.g., ESAT-6, CFP-10, and MPB83), however, generally enhances the specificity of bovine tuberculosis tests. While genes for these proteins are absent from many nontuberculous mycobacteria, they are present in M. kansasii. Instillation of M. kansasii into the tonsillar crypts of calves elicited delayed-type hypersensitivity and in vitro gamma interferon and nitrite concentration responses of leukocytes to M. avium and M. bovis purified protein derivatives (PPDs). While the responses of M. kansasii-inoculated calves to M. avium and M. bovis PPDs were approximately equivalent, the responses of M. bovis-inoculated calves to M. bovis PPD exceeded their respective responses to M. avium PPD. The gamma interferon and nitrite responses of M. kansasii-inoculated calves to recombinant ESAT-6-CFP-10 (rESAT-6-CFP-10) exceeded corresponding responses of noninoculated calves as early as 15 and 30 days after inoculation, respectively, and persisted throughout the study. The gamma interferon and nitrite responses of M. bovis-inoculated calves to rESAT-6-CFP-10 exceeded the corresponding responses of M. kansasii-inoculated calves beginning 30 days after inoculation. By using a lipoarabinomannan-based enzyme-linked immunosorbent assay, specific serum antibodies were detected as early as 50 days after challenge with M. kansasii. By a multiantigen print immunoassay and immunoblotting, serum antibodies to MPB83, but not ESAT-6 or CFP-10, were detected in M. kansasii-inoculated calves; however, responses to MPB83 were notably weaker than those elicited by M. bovis infection. These findings indicate that M. kansasii infection of calves elicits specific responses that may confound the interpretation of bovine tuberculosis tests.

Pulmonary Mycobacterium kansasii Infection in Israel, 1999–2004

BACKGROUND

Mycobacterium kansasii infection is one of the most common causes of nontuberculous mycobacterial lung disease in world. However, little is known about its background characteristics or drug sensitivity in nonendemic areas.

DESIGN

We assessed the clinical features, radiologic findings, and drug sensitivity associated with M kansasii infection in Israel.

METHODS

Patients with a culture-positive diagnosis of M kansasii infection between April 1999 and April 2004 were identified from a clinic database of tuberculosis centers. Mycobacterial cultures were performed with standard methods. Data on patient background and clinical features were collected from the medical files.

RESULTS

Mean age (+/- SD) of the 56 patients was 58 +/- 18 years, and 64% were men; 59% had associated lung disease. Fifteen percent were receiving immunosuppressive medications. None had HIV infection. Systemic comorbid diseases were noted in 27%. The most common clinical presentations were chest pain, cough, hemoptysis, fever, and night sweats. Cavitation was noted only in 54%. Older patients had more noncavitary disease than younger patients (p = 0.01, r = 0.35). Lower-lobe predominance was very rare (4%). None of the patients presented with pleural effusion or lymphadenopathy. Only seven patients (11%) underwent bronchoscopy for diagnosis. M kansasii isolates showed the highest sensitivity to rifampin, ethambutol, clarithromycin, and ofloxacin, and the highest resistance to ciprofloxacin and capreomycin. The mean duration of treatment was 21 +/- 7.2 months. There were no disease-related deaths.

CONCLUSIONS

M kansasii disease in Israel has no association with HIV, more systemic comorbid diseases and associated lung disease, and fewer cavitations. Following appropriate treatment, patients with M kansasii disease have an excellent prognosis.

Clinical and Epidemiological Study of Disease Caused by Mycobacterium kansasii in the Metropolitan Area of Bilbao, Spain

OBJECTIVE

Epidemiological description of individuals from whom Mycobacterium kansasii isolates were obtained in respiratory samples, and analysis of the isolates using molecular biological techniques.

MATERIAL AND METHODS

A descriptive retrospective/ prospective study was carried out from January 1994 to April 2002 in Basurto Hospital and Santa Marina Hospital and from January 2000 to April 2002 in Cruces Hospital, Galdakao Hospital, and San Eloy Hospital. Diagnosis of the disease was performed according to American Thoracic Society criteria; other definitions were also applied to allow inclusion of all cases. Disease caused by M. kansasii in patients who were not infected with the human immunodeficiency virus (HIV) was compared with disease caused by Mycobacterium tuberculosis in a control group. Polymerase chain reaction was applied with analysis of restriction fragment length polymorphisms to differentiate between species of mycobacteria and classify them into genotypes. Amplified fragment length polymorphisms were used to recognize clones within each genotype.

RESULTS

The patient charts of 334 patients in which an isolate of M. kansasii had been recorded were reviewed. We considered 220 patients to be suffering from disease caused by M. kansasii (American Thoracic Society criteria along with probable disease according to established definitions). The disease was more frequent in male patients (n=185; 84.1%) and in individuals who were not HIV positive (n=184; 83.6%). The highest incidence of disease in the Bizkaia region was found in Margen Izquierda-Encartaciones, where the rate was 8.05 per 100 000 inhabitants. In the Bilbao area, the highest rate was found in the districts lying on the outskirts. The underlying diseases were tuberculosis (20.5%), chronic obstructive pulmonary disease (25.9%), pulmonary neoplasia (7.7%), silicosis (0.9%), chronic liver disease (11.4%), and duodenal ulcer (8.6%). The most frequent constitutional symptoms were fever (39.1%), loss of appetite (23.2%), and weight loss (33.3%). Among the respiratory symptoms, the most outstanding were cough (70.9%) and expectoration (62.3%). The most frequent radiographic patterns were cavitation and pulmonary infiltration. The most common treatment regimen was rifampicin, isoniazid, and ethambutol (43.4%), and the average duration was 12 months in patients who were HIV negative. Analysis of antibiotic sensitivity, performed on 56 strains, revealed that 100% were resistant to isoniazid, while none displayed rifampicin resistance. Thirty-four cases of disease caused by M. kansasii were compared with 68 cases of tuberculosis, all of them without HIV infection. The comparison revealed a predominance of smokers, respiratory symptoms, and cavitation in patients with disease caused by M. kansasii. The majority of the isolates (98.5%) corresponded to genotype I. A total of 8 clones were obtained; the clones designated 1 and 3 were more common in HIV-positive and HIV-negative individuals respectively.

CONCLUSIONS

In recent years, there has been an increase in the number of patients with disease caused by M. kansasii in the province of Bizkaia. The disease is more frequent in male patients, individuals who are HIV negative, and in urban areas. In addition, more respiratory symptoms and a higher incidence of cavitation were found in patients with disease caused by M. kansasii than in those with tuberculosis. Genotype I is the most common isolate, and clones 1 and 3 affect 80% of patients suffering from the disease.

Pneumonia caused by Mycobacterium kansasii in a series of patients without recognised immune defect

The clinical and epidemiological characteristics of 17 patients diagnosed with Mycobacterium kansasii pneumonia within a limited geographical region over a period of 10 years are described. An in-depth evaluation of the innate and adaptive immune systems was performed for five available patients. A comparison was made of the genetic fingerprint patterns of the isolates obtained by restriction fragment length polymorphism (RFLP) analysis, with the major polymorphic tandem repeat (MPTR) as a probe. Predisposing factors consisted of smoking, airway abnormalities, substance abuse, diabetes or poor general condition, but in two patients no risk factor was identified. In the five patients tested, no abnormalities or deficiencies were detected in the innate or adaptive type-1 immunity. All M. kansasii isolates had identical MPTR RFLP patterns, although no epidemiological connection could be established, and these were identical to those of clinical isolates from Australian patients. These data do not support the theory that defects in the innate or adaptive type-1 immunity have a role in the pathogenesis of invasive M. kansasii infections. The identical fingerprint patterns of the isolates suggested the existence of a virulent strain of M. kansasii.

Epidemiological, clinical, and prognostic differences between the diseases caused by Mycobacterium kansasii and Mycobacterium tuberculosis in patients infected with human immunodeficiency virus: a multicenter study

A multicenter, comparative study was performed to determine the epidemiological, clinical, and prognostic differences between the diseases caused by Mycobacterium tuberculosis and Mycobacterium kansasii in human immunodeficiency virus (HIV)-infected patients. From 1 January 1995 through 31 December 1999, 25 HIV-infected patients received diagnoses of M. kansasii infection, and another 75 were selected as control subjects from among patients who had M. tuberculosis infection. Variables associated with M. tuberculosis disease in the multivariate analysis were previous intravenous drug use (odds ratio [OR], 8; 95% confidence interval [CI], 1.5-41.4) and interstitial radiologic pattern (OR, 12.7; 95% CI, 1.7-94.3). Variables associated with M. kansasii were previous diagnosis of acquired immunodeficiency syndrome (OR, 15.8; 95% CI, 4.2-59.6) and concomitant opportunistic infections (OR, 14.2; 95% CI, 2-105.7). Clinical and radiologic features were similar for both groups, but epidemiological characteristics and prognosis were different. M. kansasii disease was associated more closely with level of immunosuppression and progression of HIV infection than was disease caused by M. tuberculosis.

Pulmonary disease caused by Mycobacterium xenopi in HIV-negative patients: five year follow-up of patients receiving standardised treatment

The literature concerning the management of pulmonary disease caused by Mycobacterium xenopi is scanty and consists of retrospective reports, mostly of small series of patients. Our aim was to document the clinical features and response to treatment of this rare but challenging disease. Patients were treated in a randomised, multi-centre trial with either rifampicin plus ethambutol or rifampicin, ethambutol and isoniazid. Clinical, bacteriological and radiological progress was monitored at set intervals for 5 years. As no differences emerged between the two groups, the results have been combined to provide this prospective survey. Forty-two patients were studied. Mean age was 65 years, three-quarters were male and two-thirds had other lung disease(s). Sputum was positive on direct smear in 62%. Cavitation was present in 81%, mostly large cavities, and disease was extensive in 38%. Despite good clinical response and little toxicity the death rate was high (69%), but less than 10% died primarily because of the M. xenopi disease. The failure of treatment/relapse rate was 12%. Only 11 (26%) were known to be alive at 5 years of whom seven (17%) were known to be cured. There was no correlation between failure of treatment/relapse and in vitro resistance. Better methods of susceptibility testing and more effective regimens are needed, but it is also evident that improved management of concomitant diseases and better general health will play a major part in increasing survival.

Nontuberculous mycobacterial pulmonary diseases in immunocompetent patients

Nontuberculous mycobacterial (NTM) infections are an increasingly recognized cause of chronic lung disease in immunocompetent adults, and the M. avium complex, M. kansasii, and a rapidly growing mycobacteria such as M. abscessus, M. fortuitum, and M. chelonae account for most of the pathogens involved. Because the clinical features of NTM disease are not distinguishable from those of tuberculosis, and NTM are ubiquitous in the environment, diagnosis requires that the bacilli are isolated and identified. NTM diseases have been difficult to treat, though since the introduction of new macrolides, the outcome for patients with some NTM diseases has improved significantly. For correct diagnosis and the successful treatment of NTM pulmonary disease, a knowledge of the full spectrum of clinical and radiological findings is important.

Imaging of Non-tuberculous (Atypical) Mycobacterial Pulmonary Infection

Pulmonary infections due to mycobacterial organisms are increasing in incidence. Non-tuberculous (atypical) mycobacteria (NTM) represent a significant proportion of mycobacterial infections and may prove difficult to diagnose due to their non-specific clinical and radiographic presentations. An increasing volume of radiological data is now available for the more common non-tuberculous mycobacterial infections, and we have summarized the imaging features found in such cases, identifying radiographic features that would favour the diagnosis of a non-tuberculous mycobacterium and that, in some cases, suggest a specific organism.

[Pulmonary disease caused by Mycobacterium kansasii. Analysis of 39 cases]

OBJECTIVE

To study the epidemiological, clinical, radiological, and microbiological characteristics as well as clinical course and response to treatment of patients with lung disease due to Mycobacterium kansasii.

METHODS

All cases of lung disease caused by M. kansasii diagnosed between 1993 and 1998 in Santa Marina Hospital in Bilbao (Spain) were reviewed.

RESULTS

The nurse identified 39 cases of lung disease caused by M. kansasii. The incidence in our practice is growing. Most patients were men (97.4%). Mean patient age was 55.9 years. Relevant features of patients' case histories were lung tuberculosis (38.4%), chronic airflow limitation (28.2%) and smoking (87%). Most patients lived in urban settings (94.8%). The most frequent symptoms were cough (87%) and general malaise (72%). Hemoptysis occurred in 31%. Chest images showed mainly a localized alveolar pattern (69%). Cavitation was present in 76.9%. Bacilli were observed in 76.9%. Antibiograms (for 30 cases) showed resistance to the following drugs: rifampicin 3.3%, isoniazid (1 microgram/ml 10%, isoniazid (0.2 microgram/ml 100%, ethambutol 6.6%, streptomycin 90%, pyrazinamide 90%. Eight patients (22% of 36) died; all had severe associated disease. In 33% of the 21 patients with cavitation, closure was not achieved according to follow-up images. Follow-up microbiological tests revealed one case (2.7% of 36 patients) of treatment failure and four cases (15.3% of 26 patients) of relapse.

CONCLUSIONS

The number of patients with lung disease due to M. kansasii has increased significantly in recent years in our hospital. The mortality rate in these patients was high, but we believe it is explained by the severity of associated disease. The 15.3% rate of relapse calls for long-term follow-up of such patients.

Pulmonary Mycobacterium kansasii infection: comparison of the clinical features, treatment and outcome with pulmonary tuberculosis

BACKGROUND

In the United Kingdom Mycobacterium kansasii is the most common pulmonary non-tuberculous mycobacteria to cause disease in the non-HIV positive population.

METHODS

The clinical features, treatment, and outcome of 47 patients (13 women) of mean (SD) age 58 (17) years with culture positive pulmonary M kansasii infection were compared with those of 87 patients (23 women) of mean (SD) age 57 (16) years with culture positive pulmonary M tuberculosis infection by review of their clinical and laboratory records. Each patient with M kansasii infection was matched for age, sex, race and, where possible, year of diagnosis with two patients with M tuberculosis infection.

RESULTS

All those with M kansasii infection were of white race. Haemoptysis was more common in patients infected with M kansasii but they were less likely to present as a result of an incidental chest radiograph or symptoms other than those due to mycobacterial infection. Patients with M kansasii were also less likely to have a history of diabetes, but the frequency of previous chest disease and tuberculosis was similar. An alcohol intake of > 14 units/week was less frequent in those with M kansasii, but there were no significant differences in drug history, past and present smoking habit, occupational exposures, social class, or marital status. Patients with M kansasii received a longer total course of antimycobacterial therapy and, in particular, extended treatment with ethambutol and rifampicin was given. There was no significant difference in outcome between pulmonary M kansasii or M tuberculosis infection.

CONCLUSIONS

There are group differences between the clinical features of the two infections but, with the possible exception of diabetes and alcohol intake, these features are unlikely to be diagnostically helpful. Treatment of M kansasii infection with ethambutol, isoniazid, and rifampicin in these patients was as effective as standard regimens given to patients infected with M tuberculosis.