Molecular diagnosis of nontuberculous mycobacteria

Of tuberculosis and non-tuberculous mycobacterial infections - a comparative analysis of epidemiology, diagnosis and treatment

Pulmonary diseases due to mycobacteria cause significant morbidity and mortality to human health. In addition to tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), recent epidemiological studies have shown the emergence of non-tuberculous mycobacteria (NTM) species in causing lung diseases in humans. Although more than 170 NTM species are present in various environmental niches, only a handful, primarily Mycobacterium avium complex and M. abscessus, have been implicated in pulmonary disease. While TB is transmitted through inhalation of aerosol droplets containing Mtb, generated by patients with symptomatic disease, NTM disease is mostly disseminated through aerosols originated from the environment. However, following inhalation, both Mtb and NTM are phagocytosed by alveolar macrophages in the lungs. Subsequently, various immune cells are recruited from the circulation to the site of infection, which leads to granuloma formation. Although the pathophysiology of TB and NTM diseases share several fundamental cellular and molecular events, the host-susceptibility to Mtb and NTM infections are different. Striking differences also exist in the disease presentation between TB and NTM cases. While NTM disease is primarily associated with bronchiectasis, this condition is rarely a predisposing factor for TB. Similarly, in Human Immunodeficiency Virus (HIV)-infected individuals, NTM disease presents as disseminated, extrapulmonary form rather than as a miliary, pulmonary disease, which is seen in Mtb infection. The diagnostic modalities for TB, including molecular diagnosis and drug-susceptibility testing (DST), are more advanced and possess a higher rate of sensitivity and specificity, compared to the tools available for NTM infections. In general, drug-sensitive TB is effectively treated with a standard multi-drug regimen containing well-defined first- and second-line antibiotics. However, the treatment of drug-resistant TB requires the additional, newer class of antibiotics in combination with or without the first and second-line drugs. In contrast, the NTM species display significant heterogeneity in their susceptibility to standard anti-TB drugs. Thus, the treatment for NTM diseases usually involves the use of macrolides and injectable aminoglycosides. Although well-established international guidelines are available, treatment of NTM disease is mostly empirical and not entirely successful. In general, the treatment duration is much longer for NTM diseases, compared to TB, and resection surgery of affected organ(s) is part of treatment for patients with NTM diseases that do not respond to the antibiotics treatment. Here, we discuss the epidemiology, diagnosis, and treatment modalities available for TB and NTM diseases of humans.

Mycobacterium marinum infection in fish and man: epidemiology, pathophysiology and management; a review

Mycobacterium marinum is an opportunistic pathogen inducing infection in fresh and marine water fish. This pathogen causes necrotizing granuloma like tuberculosis, morbidity and mortality in fish. The cell wall-associated lipid phthiocerol dimycocerosates, phenolic glycolipids and ESAT-6 secretion system 1 (ESX-1) are the conserved virulence determinant of the organism. Human infections with Mycobacterium marinum hypothetically are classified into four clinical categories (type I-type IV) and have been associated with the exposure of damaged skin to polluted water from fish pools or contacting objects contaminated with infected fish. Fish mycobacteriosis is clinically manifested and characterized in man by purple painless nodules, liable to develop into superficial crusting ulceration with scar formation. Early laboratory diagnosis of M. marinum including histopathology, culture and PCR is essential and critical as the clinical response to antibiotics requires months to be attained. The pathogenicity and virulence determinants of M. marinum need to be thoroughly and comprehensively investigated and understood. In spite of accumulating information on this pathogen, the different relevant data should be compared, connected and globally compiled. This article is reviewing the epidemiology, virulence factors, diagnosis and disease management in fish while casting light on the potential associated public health hazards.

Mycobacterium stephanolepidis sp. nov., a rapidly growing species related to Mycobacterium chelonae, isolated from marine teleost fish, Stephanolepis cirrhifer

A previously undescribed rapidly growing, non-pigmented mycobacterium was identified based on biochemical and nucleic acid analyses, as well as growth characteristics. Seven isolates were cultured from samples collected from five thread-sail filefish (Stephanolepis cirrhifer) and two farmed black scraper (Thamnaconus modestus). Bacterial growth occurred at 15-35 °C on Middlebrook 7H11 agar. The bacteria were positive for catalase activity at 68 °C and urease activity, intermediate for iron uptake, and negative for Tween 80 hydrolysis, nitrate reduction, semi-quantitative catalase activity and arylsulfatase activity at day 3. No growth was observed on Middlebrook 7H11 agar supplemented with picric acid, and very little growth was observed in the presence of 5 % NaCl. α- and α'-mycolates were identified in the cell walls, and a unique profile of the fatty acid methyl esters and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) profiles of the protein and cell-wall lipids were acquired. Sequence analysis revealed that the seven isolates shared identical sequences for the 16S rRNA, rpoB, hsp65, recA and sodA genes. Phylogenetic analysis of the five gene sequences confirmed that the isolates were unique, but closely related to Mycobacterium chelonae. Antibiotic susceptibility testing revealed the minimum inhibitory concentration (MIC) of clarithromycin against this novel species was <0.25 µg ml^-1, which was lower than that for Mycobacterium salmoniphilum. The hsp65 PCR restriction enzyme analysis pattern differed from those of M. chelonae and M. salmoniphilum. Based on these findings, the name Mycobacterium stephanolepidis sp. nov. is proposed for this novel species, with the type strain being NJB0901^T (=JCM 31611^T=KCTC 39843^T).

Vertebral osteomyelitis caused by non-tuberculous mycobacteria: Predisposing conditions and clinical characteristics of six cases and a review of 63 cases in the literature

Background Several case series have reported on clinical and radiographic characteristics of patients with vertebral osteomyelitis (VO) caused by non-tuberculous mycobacteria (NTM). However, only a few patients were included, and systematic reviews are still lacking. The aim of this study was to update and summarise the pre-disposing conditions, clinical and radiographic characteristics of such cases due to NTM. Methods In this study, a systematic review was conducted of the English-language literature from 1961-2014 to investigate the pre-disposing conditions and characteristics of cases of VO due to NTM. Also, six additional cases diagnosed in the study hospitals were described; these cases are included in an analysis of a total of 69 cases of NTM VO. Results The most common species, regardless of the presence of HIV co-infection, was M. avium Complex followed by M. xenopi. Ten cases with HIV infection had a median CD4 lymphocyte count of 320/mm(3) (range = 41-465/mm(3)) at the time of diagnosis of NTM VO. The VO in the cases with HIV infections occurred at an earlier age and more often involved the thoracic spine than in the cases without HIV infection. Pre-disposing trauma or surgery was reported in 14.5% (10/69) of the cases. A variety of immunosuppressive diseases were observed in 49.3% of the patients, including the 10 with HIV infections and corticosteroids were used in 27.5% of the cases. Surgery was performed in 67.6% and improvement was reported in 80.6%. Conclusion NTM should be considered in immunocompromised patients with indolent VO without confirmation of tuberculosis.

Diseases caused by nontuberculous mycobacteria in Asia

 The isolation rate of nontuberculous mycobacteria (NTM) species and the prevalence of NTM-associated diseases are on the rise in Asian, as well as in Western countries; however, the species distribution of NTM isolates and the types of diseases caused by NTM species vary from region to region. In this review, we present an update on the epidemiology of NTM in Asia. We demonstrate that the distribution of NTM species varies within Asia and differs from that in North America and Europe. In addition, the clinical manifestations of NTM diseases include respiratory tract infections, disseminated infections, skin and soft tissue infections, lymphadenitis, empyema, ocular infections, CNS infections and genitourinary infections. Finally, the rate of adaptive resistance of anti-NTM antimicrobial agents remains high and may be associated with a poor outcome for patients with NTM diseases.

Rapid detection and differentiation of mycobacterial species using a multiplex PCR system

INTRODUCTION

The early diagnosis of mycobacterial infections is a critical step for initiating treatment and curing the patient. Molecular analytical methods have led to considerable improvements in the speed and accuracy of mycobacteria detection.

METHODS

The purpose of this study was to evaluate a multiplex polymerase chain reaction system using mycobacterial strains as an auxiliary tool in the differential diagnosis of tuberculosis and diseases caused by nontuberculous mycobacteria (NTM) RESULTS: Forty mycobacterial strains isolated from pulmonary and extrapulmonary origin specimens from 37 patients diagnosed with tuberculosis were processed. Using phenotypic and biochemical characteristics of the 40 mycobacteria isolated in LJ medium, 57.5% (n=23) were characterized as the Mycobacterium tuberculosis complex (MTBC) and 20% (n=8) as nontuberculous mycobacteria (NTM), with 22.5% (n=9) of the results being inconclusive. When the results of the phenotypic and biochemical tests in 30 strains of mycobacteria were compared with the results of the multiplex PCR, there was 100% concordance in the identification of the MTBC and NTM species, respectively. A total of 32.5% (n=13) of the samples in multiplex PCR exhibited a molecular pattern consistent with NTM, thus disagreeing with the final diagnosis from the attending physician.

CONCLUSIONS

Multiplex PCR can be used as a differential method for determining TB infections caused by NTM a valuable tool in reducing the time necessary to make clinical diagnoses and begin treatment. It is also useful for identifying species that were previously not identifiable using conventional biochemical and phenotypic techniques.

First Canadian Reports of Cervical Adenitis Due to Mycobacterium Malmoense and a 10-year Review of Nontuberculous Mycobacterial Adenitis

The present report reviews a decade of experience with nontuberculous mycobacterial adenitis at a pediatric referral centre, noting that patients are often subjected to multiple ineffective antibiotic courses, and that delays in diagnosis and referral for appropriate therapy are common. Notable clinical features include a mean age of presentation of 3.4 years, a male-to-female ratio of 1:1.5 and a gradual onset of painless, unilateral cervical adenopathy. Fever was absent in most patients (77%), and the disease failed to respond to antistaphylococcal antibiotics. The mean time to correct diagnosis was longer than three months (15 weeks). The clinical features of the disease are highlighted and presented with a practical diagnostic approach to the child with subacute/chronic adenitis. New molecular diagnostic tools and emerging mycobacteria are discussed, including the first reports of Mycobacterium malmoense adenitis in Canada.

Upper extremity Mycobacterium marinum infection

Mycobacterium marinum is the cause of opportunistic infections in man. Although its clinical presentation is usually cutaneous, osteoarticular infections are not rare and should be rapidly diagnosed. Orthopaedic surgeons may have to manage a patient with this mycobacterial infection and should be able to make this diagnosis based on information about the patient's history and clinical criteria. Lesions develop from a skin wound, with a single nodule or a bright purplish-red patch with papules; they also may be inflamed or may abscess. Secondary lesions may develop as the disease progresses. Aquatic exposure is the most important factor to look for. We report three cases of this infection with a delayed diagnosis. Response to treatment and an absence of complications are correlated with an early diagnosis.

Non-tuberculous mycobacterial infections

Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms in contrast to those belonging to the M. tuberculosi complex (MTB). NTM infects and causes disease only in hosts with local or general predisposing factors. Lung infection following inhalation of NTM is the most common NTM disease but soft tissue infections may occur in connection with contaminated trauma or surgery. Microbiological diagnosis is obtained by microscopy for acid-fast bacteria (AFB) on secretions or biopsies, and by culture on special media. With the high specificity of MTB- polymerase chain reaction (PCR), a positive AFB smear combined with negative MTB-PCR denotes infection with NTM. Sophisticated species diagnosis of cultured NTM is attained by various molecular methods, where 16S rDNA-sequencing remains the gold standard. The panorama of infection with different rapidly growing (RGM) or slowly growing mycobacteria (SGM) in Sweden is described. Sensitivity testing in vitro to antimycobacterial drugs against NTM does not always preclude the in vivo efficacy. Standard antimycobacterial treatment regimens have been defined for infection with several NTM species. Sensitivity testing should be performed in selected cases only, as in case of relapse or suspected development of resistance of the NTM strain. The spectrum of disease caused by NTM species that display a very low pathogenic potential is likely to widen over time as severe immunosuppression will continue to be prevalent in several patient categories.

Non-tuberculous mycobacteria in China

Infection with non-tuberculous mycobacteria (NTM) is relatively rare in areas that are high-endemic for tuberculosis. We identified 126 strains of NTM in respiratory specimens collected by the Chinese Nationwide Survey in 2000, the Beijing Tuberculosis and Thoracic Tumour Institution, and the Guangzhou Thoracic Hospital. Species diagnosis was attained by sequencing of 16S-rDNA complemented by phenotypic characterization when necessary. Mycobacterium avium-intracellulare-complex - well known as a potential pulmonary pathogen - was diagnosed in all 3 surveys. Potentially pathogenic rapid growing strains of M. abscessus, M. chelonae and M. fortuitum were also detected. Moreover, species non-pathogenic in the airways such as M. nonchromogenicum, M. terrae and M. gordonae were encountered. Also, single strains of rare NTM species were isolated. Thus, several potentially pathogenic species of NTM were isolated from pulmonary specimens in China, and molecular techniques made possible exact species diagnosis.

Bilateral sporotrichoid lymphocutaneous dermatosis in a drug abuser: case report and review of the literature

Bilateral sporotrichoid mycobacterial cutaneous infection is unusual and has been reported in only three cases involving different species and with an unknown route of infection in the literature.We report a case of bilateral sporotrichoid dermatosis in an immunocompetent patient with a history of intravenous heroin injection before development of the skin lesions. Both special stain and culture of biopsy specimen were negative. Finally, Mycobacterium fortuitum was identified by a polymerase chain reaction-based method. The patient responded well to clarithromycin and ciprofloxacin therapy. This case represents an unusual primary cutaneous M. fortuitum infection manifested as bilateral sporotrichoid lesions of the limbs. Review of previous reported cases of bilateral sporotrichoid mycobacterial infection shows different isolated organisms and routes of infection to that found in our case.

A review of mycobacteriosis in marine fish

Mycobacteriosis is a serious and often lethal disease of fish, affecting a wide range of species globally both in culture and wild settings. Caused by several species of the genus Mycobacterium, the disease has received considerable attention in recent years because of the discovery of new species in piscine hosts, epizootics in wild fisheries, and the ability of a few species to infect humans. The impact of this disease in aquaculture and the aquaria trade has been well reported and there is currently no widely accepted cure other than depopulation and facility disinfection. However, the impact on wild fisheries is poorly understood and may relate to species-specific interactions (host-pathogen) and possibly environmental stressors. In this review, much of what is known about mycobacteriosis in marine fish is summarized with particular attention to an epizootic in striped bass, Morone saxatilis, (Walbaum), in Chesapeake Bay, USA.

Nontuberculous mycobacterial infections

CONTEXT

Nontuberculous mycobacteria include numerous acid-fast bacilli species, many of which have only recently been recognized as pathogenic. The diagnosis of mycobacterial disease is based on a combination of clinical features, microbiologic data, radiographic findings, and histopathologic studies.

OBJECTIVE

To provide an overview of the clinical and pathologic aspects of nontuberculous mycobacteria infection, including diagnostic laboratory methods, classification, epidemiology, clinical presentation, and treatment.

DATA SOURCES

Review of the pertinent literature and published methodologies.

CONCLUSIONS

Nontuberculous mycobacteria include numerous acid-fast bacilli species, many of which are potentially pathogenic, and are classified according to the Runyon system based on growth rates and pigment production. Their slow growth hinders cultures, which require special medium and prolonged incubation. Although such methods are still used, newer nucleic acid-based technologies (polymerase chain reaction and hybridization assays) can rapidly detect and speciate some mycobacteria--most notably, distinguishing Mycobacterium tuberculosis from other species. Infections caused by these organisms can present as a variety of clinical syndromes, not only in immunocompromised patients but also in immunocompetent hosts. Most common among these are chronic pulmonary infections, superficial lymphadenitis, soft tissue and osteoarticular infections, and disseminated disease. Treatment of nontuberculous mycobacterial infections is difficult, requiring extended courses of multidrug therapy with or without adjunctive surgical intervention.

Imported tropical infectious ulcers in travelers

Skin ulcers are a commonly encountered problem at departments of tropical dermatology in the Western world. Furthermore, the general dermatologist is likely to be consulted more often for imported chronic skin ulcers because of the ever-increasing travel to and from tropical countries. The most common cause of chronic ulceration throughout the world is probably pyoderma. However, in some parts of the world, cutaneous leishmaniasis is one of the most prevalent causes. Mycobacterium ulcerans is an important cause of chronic ulcers in West Africa. Bacterial infections include pyoderma, mycobacterial infections, diphtheria, and anthrax. Pyoderma is caused by Staphylococcus aureus and/or beta-hemolytic streptococci group A. This condition is a common cause of ulcerative skin lesions in tropical countries and is often encountered as a secondary infection in travelers. The diagnosis is often made on clinical grounds. Antibacterial treatment for pyoderma should preferably be based on culture outcome. Floxacillin is generally active against S. aureus and beta-hemolytic streptococci. Infection with Mycobacterium ulcerans, M. marinum, and M. tuberculosis may cause ulcers. Buruli ulcers, which are caused by M. ulcerans, are endemic in foci in West Africa and have been reported as an imported disease in the Western world. Treatment is generally surgical, although a combination of rifampin (rifampicin) and streptomycin may be effective in the early stage. M. marinum causes occasional ulcerating lesions in humans. Treatment regimens consist of combinations containing clarithromycin, rifampin, or ethambutol. Cutaneous tuberculosis is rare in travelers but may be encountered in immigrants from developing countries. Treatment is with multiple drug regimens consisting of isoniazid, ethambutol, pyrazinamide, and rifampin. Cutaneous diphtheria is still endemic in many tropical countries. Cutaneous diphtheria ulcers are nonspecific and erythromycin and penicillin are both effective antibacterials. Antitoxin should be administered intramuscularly in suspected cases. Anthrax is caused by spore-forming Bacillus anthracis. This infection is still endemic in many tropical countries. Eschar formation, which sloughs and leaves behind a shallow ulcer at the site of inoculation, characterizes cutaneous anthrax. Penicillin and doxycycline are effective antibacterials. Cutaneous leishmaniasis is caused by different species belonging to the genus Leishmania. The disorder is one of the ten most frequent causes of skin diseases in travelers returning from (sub)tropical countries. The clinical picture is diverse, ranging from a painless papule or nodule to an ulcer with or without a scab. Treatment depends on the clinical manifestations and the species involved.Sporotrichosis, chromo(blasto)mycosis, and mycetoma are the most common mycoses that may be accompanied by ulceration. Infections are restricted to certain regions and often result from direct penetration of the fungus into the skin. Anti-mycotic treatment depends on the microorganism involved. The most common causes of infectious skin ulceration encountered in patients from tropical countries who present at a department of tropical dermatology are reviewed in this article.

Use of the real-time PCR assay in conjunction with MagNA Pure for the detection of mycobacterial DNA from fixed specimens

Tuberculosis in immunocompromised patients is often caused by Mycobacterial species other than Mycobacterium tuberculosis. Thus, detection of and differentiation between M. tuberculosis and nontuberculosis species is necessary for diagnosis of disease in these patients. Furthermore, when tissue changes show granulomatous inflammation, quick confirmation testing for mycobacterial infection is needed for conclusive diagnosis. The aim of this study was to validate the utility of a real-time polymerase chain reaction (PCR) assay in conjunction with the MagNA Pure LC automated extraction system for the detection of mycobacterial DNA from formalin-fixed, paraffin-embedded specimens. A total of 46 archived, paraffin-embedded, fixed specimens showing granulomatous inflammation were studied for mycobacterial infection by real-time PCR. Bacterial DNA was extracted and isolated using the MagNA Pure extraction system. Real-time PCR was performed on the LightCycler using the Artus Real Art Mycob Diff ASR kit from Qiagen. Thirteen of the 46 patient specimens were positive for mycobacterial infection by acid-fast bacilli (AFB) stain. Of the13 reported positive by AFB stain, 12 where positive by real-time PCR. All 13 specimens reported positive by AFB were sent for culture confirmation. Eleven of 13 were returned positive by culture. Specimens reported as negative by culture and positive by real-time PCR were confirmed positive by a second PCR method from another reference laboratory. We believe that these studies are beneficial in the differential diagnosis of mycobacterial infection from fixed tissue specimens where tuberculosis might not have been clinically initially suspected and when specimens are not suitable for microbiologic examination.

Molecular diagnostics for the detection and characterization of microbial pathogens

New and advanced methods of molecular diagnostics are changing the way we practice clinical microbiology, which affects the practice of medicine. Signal amplification and real-time nucleic acid amplification technologies offer a sensitive and specific result with a more rapid turnaround time than has ever before been possible. Numerous methods of postamplification analysis afford the simultaneous detection and differentiation of numerous microbial pathogens, their mechanisms of resistance, and the construction of disease-specific assays. The technical feasibility of these assays has already been demonstrated. How these new, often more expensive tests will be incorporated into routine practice and the impact they will have on patient care remain to be determined. One of the most attractive uses for such techniques is to achieve a more rapid characterization of the infectious agent so that a narrower-spectrum antimicrobial agent may be used, which should have an impact on resistance patterns.

Use of a novel multiplex probe array for rapid identification of Mycobacterium species from clinical isolates

Conventional identification of mycobacteria is based on the analysis of their phenotypic and biochemical characteristics after culture; thus this method is time-consuming, laborious, and is not always conclusive. Developing a fast and accurate method for rapid identification of Mycobacterium species is in urgent need for early diagnosis of mycobacteriosis and effective patient management. In this study, an efficient and affordable novel multiplex probe array which allows simultaneous identification of 15 medically important mycobacterial species was developed. A pair of genus-specific primers and a set of genus- and species-specific probes were designed according to the conserved and polymorphic regions of the 16S rRNA gene, internal transcribed spacer (ITS) sequence, and 23S rRNA gene of mycobacteria. This probe array was applied for the identification of 78 clinical mycobacterial isolates recovered from Henan, China. The results showed that the specificity and sensitivity of the probe array were 100% for both genus-specific probe and Mycobacterium tuberculosis complex-specific probe. Among 52 isolates of nontuberculous mycobacteria, 43 isolates (82.7%) can be rapidly identified to the species level. Genetic variability of 16S-23S rRNA gene ITS region in M. avium, M. intracellulare, M. chelonae, M. abscessus and M. fortuitum were analyzed. With the accumulation of the sequences of ITS identified and further optimization of probes, the multiplex probe array has the potential to be developed into a practical tool for rapid and accurate identification of mycobacterial species in clinical laboratory.

Development and evaluation of triplex PCR for direct detection of mycobacteria in respiratory specimens

AIMS

To develop a method for the simultaneous detection of Mycobacterium tuberculosis, Mycobacterium avium-intracellularecomplex (MAC), and other mycobacteria in clinical specimens using triplex PCR.

METHODS AND RESULTS

The target of amplification was the internal transcribed spacer region between the l6S and 23S rDNA genes. Twenty-two mycobacterial type strains, 118 M. tuberculosis, 87 other mycobacteria, 75 nonmycobacterial pathogens, 115 respiratory specimens from confirmed cases of tuberculous or other mycobacterial diseases, and sputa from 50 patients with nonmycobacterial respiratory diseases were tested. In M. tuberculosis, 322 bp pan-mycobacterial and 133 bp species-specific bands were observed. In MAC, the respective bands were 322 and 84 bp. The other mycobacteria showed single pan-mycobacterial bands of approx. 300-350 bp. Nonspecific amplicons were not found in any of the nonmycobacterial pathogens. In the tuberculosis specimens, 96.4% of smear-positive specimens and 70.2% of smear-negative specimens showed positive reactions. Specimens from two patients with MAC infection were MAC positive. Only 1 of 50 specimens from nonmycobacterial diseases was positive (2.0%).

CONCLUSION, SIGNIFICANCE AND IMPACT OF THE STUDY

Triplex PCR enables accurate and rapid diagnosis of tuberculosis and probably is useful for the detection of MAC and other mycobacteria in respiratory specimens.

Mycobacterial synovitis caused by slow-growing nonchromogenic species: eighteen cases and a review of the literature

CONTEXT

Slow-growing nonchromogenic mycobacterial species are an infrequent cause of soft tissue infection. Because these organisms are rare, they are not often initially considered in the differential diagnosis of synovitis.

OBJECTIVE

To evaluate the clinical and pathologic characteristics of patients with synovitis resulting from slow-growing nonchromogenic mycobacterial species.

DESIGN

A 20-year retrospective review of records from The Methodist Hospital Microbiology Laboratory identified 18 culture-positive cases of synovitis that resulted from slow-growing nonchromogenic mycobacteria, including 14 caused by Mycobacterium avium complex, 1 caused by Mycobacterium malmoense, 1 caused by Mycobacterium haemophilum, and 2 caused by Mycobacterium nonchromogenicum isolates. In addition, a comprehensive literature search revealed an additional 48 cases of synovitis caused by slow-growing nonchromogenic mycobacteria.

RESULTS

The historic literature described the majority of the 48 patients as previously healthy, elderly individuals with a several-month history of monoarticular pain and swelling in the small joints of the upper extremity. In contrast, the current series demonstrated the probable role of multiple chronic coexisting medical conditions in promoting disease susceptibility. These patients were also unique in their significantly younger age distribution and diversity of infection sites. Histologic examination and direct acid-fast bacteria stains generally did not aid the diagnosis. Amputation was performed in 2 patients because of delayed identification of disease.

CONCLUSIONS

The current series demonstrates that difficult identification and infrequent occurrence cause these organisms to be overlooked by physicians and laboratory personnel. A heightened clinical suspicion for slow-growing nonchromogenic mycobacterial species is necessary when routine culture and histopathologic findings do not readily isolate an organism, or when the patient does not respond to antibiotic and anti-inflammatory treatment.

Four cases of pulmonary Mycobacterium avium intracellulare complex presenting as a solitary pulmonary nodule and a review of other cases in Japan

OBJECTIVE

To evaluate clinical findings of patients with a solitary pulmonary nodule in Japan caused by pulmonary Mycobacterium avium complex (MAC) disease.

METHODS

The authors investigated the clinical features of 12 patients diagnosed as having pulmonary MAC disease who had presented with a solitary pulmonary nodule.

RESULTS

The causative microorganisms were M. avium in seven patients, Mycobacterium intracellulare in two and MAC in three. The diagnostic methods were bronchoscopic biopsy or percutaneous lung biopsy in three patients and surgical operations in the remaining nine. Eleven patients had a complete surgical resection of the nodule and antituberculous drugs were administered to eight. On X-ray, there was an absence of calcification, satellite lesions, cavities, or bronchoectasis that are often thought to be characteristic of pulmonary mycobacterial disease. Differentiation from lung cancer was thought necessary in five patients. There was no microbiological or radiological relapse in those who underwent complete surgical resection.

CONCLUSIONS

Because treatment is often poorly effective for patients with pulmonary non-tuberculous mycobacterial disease, it is important to identify the causative microorganisms by performing a culture examination of resected lung tissue especially if there is a solitary pulmonary nodule.

Detection and genotyping of Mycobacterium species from clinical isolates and specimens by oligonucleotide array

Identification of pathogenic Mycobacterium species is important for a successful diagnosis of mycobacteriosis. The purpose of this study was to develop an oligonucleotide array which could detect and differentiate mycobacteria to the species level by using the internal transcribed spacer (ITS) sequence. Using a genus-specific probe and 20 species-specific probes including two M. avium-intracellulare complex (MAC)-specific probes, we have developed an ITS-based oligonucleotide array for the rapid and reliable detection and discrimination of M. tuberculosis, MAC, M. fortuitum, M. chelonae, M. abscessus, M. kansasii, M. gordonae, M. scrofulaceum, M. szulgai, M. vaccae, M. xenopi, M. terrae, M. flavescens, M. smegmatis, M. malmoense, M. simiae, M. marinum, M. ulcerans, M. gastri, and M. leprae. All mycobacteria were hybridized with a genus-specific probe (PAN-03) for detection of the genus Mycobacterium. Mycobacterial species were expected to show a unique hybridization pattern with species-specific probes, except for M. marinum and M. ulcerans, which were not differentiated by ITS-based probe. Among the species-specific probes, two kinds of species-specific probes were designed for MAC in which there were many subspecies. The performance of the oligonucleotide array assay was demonstrated by using 46 reference strains, 149 clinical isolates, and 155 clinical specimens. The complete procedure (DNA extraction, PCR, DNA hybridization, and scanning) was carried out in 4.5 h. Our results indicated that the oligonucleotide array is useful for the identification and discrimination of mycobacteria from clinical isolates and specimens in an ordinary clinical laboratory.