Genetic research about Mycobacterium avium complex

We conducted four genetic studies on the Mycobacterium avium complex (MAC). (1) M. avium genotyping: A total of 70 clinical isolates from patients with pulmonary MAC infections were typed by MATR-VNTR, IS1245-RFLP, and MIRU-VNTR analyses to compare discriminatory powers of these typing methods. To allow a comparison of discriminatory powers, the Hunter-Gaston discriminatory index (HGDI) was calculated, giving a HGDI of 0.960 for IS1245-RFLP, 0.949 for MIRU-VNTR, and 0.990 for MATR-VNTR, demonstrating that MATR-VNTR analysis is the best of the three genotyping methods. (2) Genetic characteristics of M. avium: Japanese clinical isolates of M. avium were subjected to insertion sequence (IS) analyses. First, an analysis of 81 isolates by heat shock protein 65 identified all isolates as belonging to the subspecies of M. avium subsp. hominissuis. Another analysis by IS901 identified about 70% of the isolates as IS901-carriers. IS901 had been thought to be carried by the subspecies that infect birds: M. avium subsp. avium and M. avium subsp. silvaticum. Studies have reported that most human isolates in the U.S. and Europe carry no IS901. The prevalence of IS901-carriers among Japanese clinical isolates of M. avium is thus a significant characteristic. A further analysis of the IS901 showed that compared with M. avium subsp. avium, the clinical isolates shared 60 point mutations of nucleotide sequence. This novel insertion sequence was designated "ISMav6". (3) The CAM-resistance gene in MAC: This study assessed the correlation between CAM-susceptibility and mutation of the gene involved in drug resistance (A DNA sequence analysis identified mutations at positions 2058 and 2059 in domain V of 23S-rRNA). Furthermore, a system was developed to rapidly detect the presence/absence of CAM resistance by ARMS-PCR, a procedure used to detect gene mutations. The utility of this new system was also evaluated. A total of 253 clinical isolates were tested for drug susceptibility, with 227 isolates identified as sensitive and 26 as resistant. Sequence analyses showed that all 28 strains randomly selected for testing from the sensitive strains were wild type, whereas 24 of the 26 resistant strains were mutant type. The rest of the 2 strains were subsequently confirmed to be mutant type after they were isolated from contaminations with sensitive strains. These results showed an association between drug susceptibility and drug-resistant gene mutation. In addition, ARMS-PCR provided a sensitivity of 84.6% (22/26) and a specificity of 100% (28/28) for the detection of gene mutations. The lower sensitive was probably attributable to the fact that every one of the 4 strains was a combination of wild type and mutant type. These results indicated that compared with drug-susceptibility tests, ARMS-PCR provides earlier results on the presence/absence of drug resistance and has the capability of rapid detection even when the specimen contains a mixture of sensitive and resistant strains. (4) Development of a VNTR analysis for M. intracellulare: Bioinformatics analyses were used to develop a VNTR analysis for M. intracellulare and to evaluate the utility of the VNTR analysis. First, the Tandem Repeat Finder (TRF) software was used to conduct a search of TR loci on the genomic data of M. intracellulare ATCC 13950 published in December 2007, resulting in the identification of 16 TR loci, which were used in VNTR analyses of 74 isolates from pulmonary MAC infections. The HGDI was 0.988, suggesting an excellent discriminatory power. Furthermore, a stability evaluation of the VNTR loci was conducted in isolates from patients with long-term bacilli discharge. The VNTR loci were stable without changes for up to 4 years in 14 such patients. These results indicated that this method is useful in M. intracellulare genotyping and in determining whether the cause of recurrence in recurred patients is endogenous from the remnant bacilli or exogenous from another infection of different bacilli, given that the VNTR loci have been confirmed to be stable.

Clinical analysis of patients with pulmonary nontuberculous mycobacterial disease complicated by pneumothorax

OBJECTIVE

We clarified the clinical characteristics of patients with pulmonary nontuberculous mycobacterial (NTM) disease complicated by pneumothorax.

METHODS

We retrospectively selected 220 patients who satisfied the diagnostic criteria for NTM disease proposed by the American Thoracic Society (ATS). Nine patients with pulmonary NTM disease were complicated with pneumothorax. We investigated the patients' background, laboratory findings, radiological findings, treatment and prognoses.

RESULTS

There were nine patients, including six men and three women, with a mean age of 73.2 years. Seven patients had underlying respiratory diseases such as chronic obstructive pulmonary disease (COPD) excluding pulmonary NTM disease. The causative microorganisms was Mycobacterium avium in four patients, M. intracellulare in four patients, and M. kansasii in one patient. Regarding the radiological findings, pneumothorax was recognized in the right lung in five patients, in the left lung in three patients, and in both lungs heterogeneously in one patient. Although most patients exhibited multiple cavities and extensive lesions over the unilateral lung fields, three patients were simultaneously diagnosed with pulmonary NTM disease at the onset of pneumothorax. As for treatment, thoracic drainage was performed in seven patients, while one patient was advised only to rest and one patient required both thoracic drainage and surgery. The responses to the treatment was poor in each case, and five patients died due to pneumonia or heart failure.

CONCLUSION

In this study, the rate of pneumothorax complications in the patients with pulmonary NTM disease (4.1%) was higher than that of other reports. The responses to treatment, and prognoses were poor due to the presence of other complications.

Mixed pulmonary infection with three types of nontuberculous mycobacteria

A 71-year-old man with a history of chronic obstructive pulmonary disease (COPD) and silicosis was referred to our hospital for an evaluation of dyspnea. A progressively enlarging cavity found in the patient's left lower lung was associated with a worsening respiratory status. One year after the initial referral, the patient was diagnosed with nontuberculous mycobacterial (NTM) infection. We herein report the case of a patient with a mixed infection of M. kansasii, M. avium complex and M. abscessus, the various organisms having been isolated in succession. Recognizing a diagnosis of mixed pulmonary NTM infection is therefore crucial in patients with underlying diseases.

Mycobacterium avium lung disease combined with a bronchogenic cyst in an immunocompetent young adult

We report a very rare case of a bronchogenic cyst combined with nontuberculous mycobacterial pulmonary disease in an immunocompetent patient. A 21-year-old male was referred to our institution because of a cough, fever, and worsening of abnormalities on his chest radiograph, despite anti-tuberculosis treatment. Computed tomography of the chest showed a large multi-cystic mass over the right-upper lobe. Pathological examination of the excised lobe showed a bronchogenic cyst combined with a destructive cavitary lesion with granulomatous inflammation. Microbiological culture of sputum and lung tissue yielded Mycobacterium avium. The patient was administered anti-mycobacterial treatment that included clarithromycin.

[A case of environmental infection with pulmonary Mycobacterium avium complex disease from a residential bathroom of a patient suggested by variable-number tandem-repeat typing of Mycobacterium avium tandem repeat loci]

A 63-year-old woman was referred to our hospital because of bilateral infiltrations and nodular opacities in her chest radiograph taken in the mass radiography screening in September 2010. The chest computed tomography showed patchy infiltrations with bronchiectasis in the lower lung fields on both sides. She was diagnosed with pulmonary Mycobacterium avium complex (MAC) disease based on the bacteria recovered from the sputum and the bronchoalveolar lavage fluid. To elucidate an environmental MAC source, we investigated her home, and isolated M. avium and M. gordonae from the bathtub and shower tap, respectively, in her residential bathroom. Analysis of the hsp65-PRA variants digested with BamHI and some insertion sequences showed that the clinical strains recovered from sputum and strains from the bathtub were M. avium subsp. hominissuis. A dendrogram of the Mycobacterium avium tandem repeat loci variable-number tandem-repeat (MATR-VNTR) analysis of the MAC strains showed that the bathtub strains formed a polyclonal colonization, and that 1 of the 5 MATR-VNTR patterns was identical to the corresponding pattern of the sputum strain from the patient. In conclusion, we believe that the residential bathroom of the patient was the environmental source of her pulmonary MAC disease, as has been previously reported.

Acquired immune-deficiency syndrome with focal onset of Mycobacterium avium infection displaying a histological/genetic pattern of disseminated mycobacteria

A 66-year-old man with human immunodeficiency virus (HIV) infection was admitted for treatment of Pneumocystis pneumonia. Upon admission, a tumor mass adjacent to the thoracic descending aorta was revealed on computed tomography. Histology revealed an exudative granuloma with histiocytes packed with numerous acid-fast bacilli. Mycobacterium avium was isolated from the tissue. A genetic examination of the isolates demonstrated this strain to be located in the cluster consisting of strains that cause systemic infection. The patient's baseline CD4+ cell count was 9/μL and the HIV-RNA viral load was 43,800 copies/mL. This case suggests the possibility of a localized onset of disseminated M. avium infection.

[Pulmonary MAC disease and the mycobacterial genotyping]

Although pulmonary MAC disease tends to have variable disease progression, predictors related to disease progression have not been fully established. With this background, we evaluated variable numbers of tandem repeats (VNTR) in 16 mycobacterial interspersed repetitive unit loci of M. avium clinical isolates from respiratory specimens. Cluster analysis of the VNTR data showed that M. avium isolates from progressive versus stable lung disease grouped together in distinct clusters. In further analysis of logistic regression modeling, the progression of pulmonary MAC disease could be predicted by using a best-fit model. The data demonstrate that disease progression of pulmonary MAC disease is significantly associated with the M. avium genotyping.

Value of bone marrow biopsy in children with suspected disseminated mycobacterial disease

BACKGROUND

Disseminated tuberculosis (TB) is a severe form of disease that can be difficult to diagnose or exclude. The diagnostic role of bone marrow biopsy and culture in children with suspected disseminated TB is not clearly defined.

METHODOLOGY

In a prospective hospital-based study conducted from November 2007 to October 2008, bone marrow biopsy and culture were performed in all children referred with possible disseminated TB; relevant clinical and laboratory data were reviewed.

RESULTS

Thirty-five children were included in the study. An alternative diagnosis was established in 10 (29%) and mycobacterial disease confirmed or probable in 25 (71%). Among those with mycobacterial disease, multiple respiratory specimens provided the best yield (17/25; 68%). Bone marrow histology and/or culture were positive in 5/25 (20%), but were frequently collected after initiation of TB treatment. Blood cultures were positive in only one patient. Mycobacterium tuberculosis accounted for 16/19 (84%) confirmed cases, M.bovis bacille Calmette-Guérin for one, M. avium complex for one, and one was culture-negative. Histology results were available within 24 hours; TB was confirmed exclusively by bone marrow in two cases.

CONCLUSION

Bone marrow biopsy is a valuable diagnostic procedure in children with suspected disseminated mycobacterial disease. Ideally, patients should be referred prior to treatment initiation.

Bronchoscopic microsampling for bacterial colony counting in relevant lesions in patients with pulmonary Mycobacterium avium complex infection

OBJECTIVE

The incidence of pulmonary Mycobacterium avium complex (MAC) infections with nodular/bronchiectasis lesions is increasing. However, factors determining deterioration are unknown. In the present study, we investigated quantitative MAC cultures obtained through bronchoscopic microsampling (BMS) from patients with pulmonary MAC infection and analyzed the relationship between MAC culture and the short-term natural history. We also assessed chest computed tomography (CT) findings for the deteriorating factors.

DESIGN

For this prospective study, MAC was collected from peripheral lung lesions by BMS through endobronchial ultrasonography. MAC colonies were counted on Middlebrook 7H11 agar. We compared the number of MAC colonies with laboratory data and chest CT findings.

PATIENTS

We studied 26 patients with pulmonary MAC infection.

RESULTS

The patients were divided into 2 groups: 11 patients in the non-deteriorated group and 15 patients in the deteriorated group. The number of MAC colonies was significantly correlated with deterioration of MAC infection (p < 0.001). In the non-deteriorated group, chest CT scans showed nodular/bronchiectasis lesions in 8 patients (73%) and consolidated lesions in 3 patients (27%). In the deteriorated group, chest CT scans showed nodular/bronchiectasis lesions in 1 patient (7%), consolidated lesions in 6 patients (40%), and cavitary lesions in 8 patients (53%).

CONCLUSION

The number of MAC colonies in relevant lesions investigated by BMS was significantly larger in the deteriorated group than in the non-deteriorated group. Cavitary and consolidated lesions observed from chest CT scans are thought to indicate a high risk of progression of pulmonary MAC infection.

Non-tuberculous mycobacterial diseases presenting as solitary pulmonary nodules

SETTING

South Korea, 2005-2007.

BACKGROUND

Non-tuberculous mycobacterial diseases presenting as solitary pulmonary nodules (NTM-SPN) are rare and may be misdiagnosed as tuberculoma.

DESIGN

Eleven NTM-SPN patients were enrolled retrospectively and compared with two groups each of 33 patients with upper lobe cavitary (UC) and nodular bronchiectatic (NB) type NTM diseases, respectively.

RESULTS

The patients' median age was 52 years. Compared with UC-type disease, NTM-SPN patients showed female (n = 9) and never smoker (n = 8) predominance and fewer comorbidities (n = 0; P < 0.05 for each). Mycobacterium avium (n = 9) was predominant in NTM-SPN patients, followed by M. intracellulare (n = 2), whereas M. intracellulare was most frequently isolated from patients with both UC- and NB-type NTM (P < 0.05). The nodules were a median of 2.3 cm in diameter (range 1.6-6.3 cm) and were distributed evenly in all lobes. In all patients, percutaneous needle aspiration/biopsy was performed with a median 71 days of diagnostic delay. Ten patients successfully completed treatment, and one showed spontaneous reduction of nodule size without treatment. Reverse blot hybridisation assays of six DNA samples identified four subjects with M.avium-intracellulare complex (MAC), in line with conventional test data.

CONCLUSION

NTM-SPN was caused exclusively by MAC. Although clinical outcome was favourable, confirmatory diagnosis was delayed. Molecular methods are needed for early diagnosis of NTM-SPN.

[Susceptibility to rifabutin and novel fluoroquinolones in Mycobacterium avium complex isolates from patients with sputum culture-positive pulmonary disease who are undergoing standard chemotherapy]

We investigated the susceptibility to conventional and newer antimycobacterial agents including rifabutin (RBT) and novel fluoroquinolones (NFQs) among 48 clinical Mycobacterium avium complex (MAC) isolates from patients with sputum culture-positive MAC disease who were undergoing standard chemotherapy. RBT and NFQs were superior to conventional agents because of higher rates of susceptibility and lower minimum inhibitory concentration. NFQs showed cross-resistance among quinolones. In contrast, RBT did not show cross-resistance to RFP. Most clarithromycin-resistant or rifampicin-resistant cases were susceptible to RBT and NFQs. In conclusion, RBT and NFQs possess good in vitro antimicrobial activity among clinical isolates of culture-positive pulmonary MAC disease, which suggests that a combination of such microbiologically active agents may improve clinical effectiveness more than standard chemotherapy regimens.

Autologous fat transplantation and delayed silicone implant insertion in a case of Mycobacterium avium breast infection

BACKGROUND

Infection after breast augmentation is uncommon, occurring in 1-3% of cases. They are typically caused by bacterial skin flora, specifically Staphylococcus aureus and the coagulase-negative staphylococci. There have been infrequent reports of breast implant infection caused by the atypical mycobacteria.

METHODS

This report summarizes the case of a female patient who was infected by Mycobacterium avium after undergoing augmentation mammoplasty. This is the second case reported in the literature. Conservative recommendations include antibiotic therapy and removal of the implant until resolution of the infection or until healing of the wound. Salvage methods include one or more of the following: antibiotic therapy, debridement, curettage, pulse lavage, capsulectomy, device exchange, primary closure, and/or flap coverage.

RESULTS

After removal of the implant and antibiotic therapy, autologous fat transplantation for correction of breast tissue depressions caused by the mycobacterium infection was done. Delayed bilateral breast augmentation by inserting polyurethane-covered silicone implants in subpectoral position and round block mastopexy to resect the periareolar scars were performed.

CONCLUSION

Although this kind of complication has significantly compromised the aimed result and has caused frustration to both the patient and the physicians involved, we believe that the combination of autologous fat transplantation and delayed silicone implant insertion can be a safe strategy and can produce an acceptable aesthetic result.

A case of familial pulmonary mycobacterium avium complex disease

We report one Japanese familial line in which there were three pulmonary MAC patients and one suspected patient over two generations, most of whom were diagnosed with the nodular/bronchiectatic type. In all patients, life circumstances and bacterial strains differed at the time of diagnosis. This suggests that the genes thought to affect patient susceptibility to pulmonary MAC disease may be involved in this family line. Comprehensive genotypic analysis of the CFTR gene, HLA typing, and analysis of the NRAMP1 polymorphisms were performed in seven members of this family. The results suggest that female sex and menopause might be associated with onset of pulmonary MAC of the nodular/bronchiectatic type, and HLA-A26 antigen and diabetes mellitus might be involved in disease exacerbations.

Atypical presentation of IL-12 receptor beta1 deficiency with pneumococcal sepsis and disseminated nontuberculous mycobacterial infection in a 19-month-old girl born to nonconsanguineous US residents

Atypical presentation of IL-12 receptor β1 deficiency with pneumococcal sepsis and disseminated nontuberculous mycobacterial infection in a 19-month-old girl born to nonconsanguineous US residents

Properties of immunosuppressive macrophages generated by Mycobacterium intracellulare infection in M. intracellulare-susceptible and resistant mice

Splenic macrophages (M(phi)s) generated in Mycobacterium intracellulare (Min)-infected mice exhibit suppressor activity against T cell mitogenesis. We examined profiles of the Min-induced generation of immunosuppressive M(phi)s (Min-M(phi)s) in Min-susceptible BALB/c (bcg(s)) and resistant CBA/JN (bcg(r)) mice. Min infection in BALB/c mice caused a more rapid generation of the immunosuppressive M(phi)s, which expressed M(phi) markers such as CD11b and F4/80, exhibited an increased ability to generate reactive oxygen intermediates, and inhibited IL-2 receptor expression by mitogenic T cells, than did Min infection in CBA/JN mice. Thus, the bcg gene may be related to the generation of Min-M(phi)s in host mice.

Demographic risk factors of pulmonary colonization by non-tuberculous mycobacteria

SETTING

British Columbia (BC), Canada.

OBJECTIVE

To determine the risk factors for pulmonary colonization by non-tuberculous mycobacteria (NTM).

DESIGN

Retrospective study of subjects colonized by NTM from 1990 to 2006. Subjects without mycobacterial disease and with at least three negative cultures served as controls.

RESULTS

Mycobacterium avium complex (MAC) species were the most common NTM. Risk factors of colonization included age > or = 60 years (aOR 2.3), female sex (aOR 1.2), residency in Canada for at least 10 years (aOR 3.8), Canadian-born aboriginal (aOR 1.8), and Canadian-born non-aboriginal (aOR 1.4). Predictors of MAC colonization included White race (aOR 1.6) and residency in Canada for at least 10 years, which was the strongest predictor (aOR 6.7). Aboriginal origin was associated with non-MAC colonization (aOR 1.8), and Canadian-born people from the East/South-East Asian ethnic groups were protected from MAC colonization (aOR 0.2), all aOR P < 0.05.

CONCLUSION

Older age, female sex, having been born in Canada, long residency in BC and White race predict pulmonary NTM colonization, while Aboriginal origin predicts non-MAC colonization. Further research is needed to identify environmental NTM sources in BC and to determine their relation to colonization and disease.

Clinical evaluation of the QuantiFERON-TB Gold test in patients with non-tuberculous mycobacterial disease

OBJECTIVE

To evaluate the clinical usefulness of the QuantiFERON TB-2G (QFT-2G) test in patients with non-tuberculous mycobacterial (NTM) disease without a previous history of tuberculosis (TB).

METHODS

The study consisted of 214 patients with NTM disease who satisfied the diagnostic guidelines of the American Thoracic Society.

RESULTS

The causative microorganism was Mycobacterium avium in 83 patients, M. intracellulare in 80, M. kansasii in 33, M. marinum in 12, M. szulgai in 3, M. abscessus in 2 and M. chelonei in 1. The positive response rate of QFT-2G test result was 2% in 163 patients with M. avium-intracellulare complex (MAIC) disease, 52% in 33 with M. kansasii disease, 58% in 12 with M. marinum disease, 33% in 3 with M. szulgai disease, 0% in two with M. abscessus disease and 0% in one with M. chelonei disease. The positivity of the QFT-2G test was 52% in patients with NTM disease, thought to be because NTM possesses common M. tuberculosis-specific antigens.

CONCLUSIONS

Although QFT-2G may be a useful diagnostic method to differentiate TB from MAIC disease, there are several problems to be resolved before it can be used as a diagnostic method for NTM disease (M. kansasii disease), including the determination of the positive cut-off level for QFT-2G test.

Mycobacterium avium complex organisms predominantly colonize in the bathtub inlets of patients' bathrooms

Medical treatment of pulmonary Mycobacterium avium complex (MAC) disease does not always provide curative effects and is frequently hampered by recurrence. This suggests the presence of a reservoir for MAC in the environment surrounding patients. We previously reported the recovery of MAC isolates from the residential bathrooms of outpatients. In the present study, to ascertain the colonizing sites and the possibility of an MAC reservoir in the bathrooms of patients, we tested the recovery and the genetic diversity of MAC isolates from 6 sites of specimens, including 2 additional sampling sites, inside the showerhead and the bathtub inlet, in the residential bathrooms of patients with pulmonary MAC disease. MAC isolates were recovered from 15 out of the 29 bathrooms (52%), including specimens from 14 bathtub inlets and 3 showerheads. Nearly half of these bathrooms (7/15) contained MAC strains that were identical or similar to their respective clinical isolates Additionally, in 5 out of 15 bathrooms, polyclonal colonization was revealed by pulsed-field gel electrophoresis. The results imply that colonization of MAC organisms in the bathrooms of MAC patients occurs predominantly in the bathtub inlets, and there is thus a risk of infection and/or reinfection for patients via use of the bathtub and other sites in the bathroom.

[Long-term observation of pulmonary Mycobacterium avium complex disease treated with chemotherapy-- following the guidelines for treatment]

OBJECTIVE

We performed a long-term retrospective investigation of pulmonary Mycobacterium avium complex (MAC) disease treated with combined chemotherapy following the ATS guideline or the Japanese Society for Tuberculosis guideline. We also studied when to terminate the combined chemotherapy.

MATERIALS AND METHODS

The subjects of this study consisted of 90 patients who underwent combined chemotherapy according to these guidelines for minimum one-year period and followed up for at least one year since April, 1998.

RESULTS

The mean patients' age was 64.8 years old and the gender distribution consisted of 34 males and 56 females. While the sputum negative conversion was observed in 54 of 90 patients (60%), clinical improvement was recognized in 35 patients (39%) following combined chemotherapy administered according to the guidelines. Out of 54 patients with sputum conversion, 30 cases were followed up after the discontinuation of treatment, and sputum relapse later was seen in 18 patients. Out of 24 patients who continued the same treatment, sputum relapse was seen in 10 patients. Out of 35 patients with clinical improvement, 17 cases have been followed up after the discontinuation of treatment, clinical worsening was later recognized in 9 patients. Out of 18 patients who continued the same treatment, clinical worsening was recognized in 6 patients.

CONCLUSIONS

As the probability of sputum relapse after discontinuation of treatment was high even among patients whose sputum converted to negative by combined treatment according to the guidelines, we think that it is better to continue treatment according to the guidelines as long as possible.