Pathogenesis of nontuberculous mycobacteria infections

M avium is a microorganism well adapted to living in the environment and in different hosts. During the past 15 years, a substantial amount of information has been accumulated about the mechanisms used by M avium to cross the host's mucosal barrier, replicate inside cells, circumvent the host's immune response, and persist inside the host. It turns out that M avium is a fascinating pathogen after all. The increasing knowledge about M avium pathogenesis may one day provide means for a more effective prophylaxis as well as for treatment of the infection.     

非结核分枝杆菌相关研究新进展

非结核分枝杆菌在自然界中广泛存在,部分可引起人类疾病.因非结核分枝杆菌对多种抗结核药物耐药,且诊断困难、患者预后较差,使非结核分枝杆菌感染性疾病逐渐成为医学界十分关注的研究课题.作者从非结核分枝杆菌种类及感染率、非结核分枝杆菌耐药情况及耐药机制研究、非结核分枝杆菌感染特点及治疗方案、非结核分枝杆菌检测方法及环境水非结核分枝杆菌污染研究等方面综述了非结核分枝杆菌相关的研究进展.其耐药机制及传播机制尚未阐明,需要进行深入研究.     

Laboratory diagnosis of nontuberculous mycobacteria

In conclusion, it is important to realize that there is no "stand alone" assay for the identification of NTM. Many new species may not be recognized in all assays. Newer molecular tests are more accurate for identification than phenotypic tests and have significantly improved turnaround time. Clinical significance of an isolate should be determined, however, before committing resources for the identification of a mycobacterial isolate to the species level. In addition, there are significant differences in the range and quality of services provided by different laboratories. Today, techniques and equipment are increasingly complex and costly, making it more difficult to upgrade every local laboratory to perform these assays. But because specimen delivery and communication of results can be rapidly and easily achieved, utilization of reference laboratories for rarely performed sophisticated tests is a more practical approach.     

Molecular diagnosis of nontuberculous mycobacteria

PURPOSE OF REVIEW: Diagnosis of infection due to nontuberculous mycobacteria is not easy, as it must be distinguished from colonization or contamination by other nontuberculous mycobacteria. Molecular methods offer many advantages over conventional methods of identification. The results are obtained rapidly, are reliable and reproducible, and even mixed or contaminated cultures can be examined. This review highlights the recent advances in molecular techniques for identification of nontuberculous mycobacteria. RECENT FINDINGS: Nontuberculous mycobacteria are ubiquitous towards the environment and have the potential to colonize and cause serious infection. An increasing number of species and clinical presentations are being described, and progress has been made towards the understanding of the underlying predisposing factors. Disease caused by nontuberculous mycobacteria is often associated with various forms of immunosuppression, particularly HIV infection, whereas mild forms of immune defects have been observed in some patients who, apart from their nontuberculous mycobacterial disease, seem to be healthy on initial examination. Molecular techniques have shown their usefulness for the identification of most mycobacteria. Probes are widely used in clinical laboratories for the identification of the most common mycobacterial species. Because automated DNA sequencing and the programs for analysing sequence data have become technically simpler, polymerase chain reaction-based sequencing is now used in many mycobacterial reference laboratories as a routine method for species identification. SUMMARY: Significant advances have been made with molecular tools for diagnosis of mycobacteria. The DNA microarray technique holds great promise for the future because it is easy to perform, it can be readily automated, and it allows the identification of a large number of mycobacterial species in one reaction.     

Epidemiology of human pulmonary infection with nontuberculous mycobacteria

A great deal of study has gone into the assessment of the epidemiology of NTM infection and disease in many different parts of the world. Review of the available studies provides insight into the frequency of this clinical problem as well as important limitations in current data. Study methods have varied greatly, undoubtedly leading to differing biases. In general, reported rates of infection and disease are likely underestimates, with the former probably less accurate than the latter, given that people without significant symptoms are not likely to have intensive investigations to detect infection. Pulmonary NTM is a problem with differing rates in various parts of the world. North American rates of infection and disease have been reported to range from approximately 1-15 per 100,000 and 0.1-2 per 100,000, respectively (see Table 1). Rates have been observed to increase with coincident decreases in TB. MAC has been reported most commonly, followed by rapid growers and M kansasii. Generally similar rates have been reported in European studies, with the exception of extremely high rates in an area of the Czech Republic where mining is the dominant industry (see Table 2). These studies have also shown marked geographic variability in prevalence. The only available population-based studies have been in South Africa and report extremely high rates of infection, three orders of magnitude greater than studies from other parts of the world (see Table 3). This undoubtedly reflects the select population with an extremely high rate of TB and resultant bronchiectasis leading to NTM infection. Rates in Japan and Australia were similar to those reported in Europe and North America and also show significant increases over time (see Table 3). Specific risk factors have been identified in several studies. CF and HIV, mentioned above, are two important high-risk groups. Other important factors include underlying chronic lung disease, work in the mining industry, warm climate, advancing age, and male sex. Aside from HIV and CF, mining with associated high rates of pneumoconiosis and previous TB may be the most important historically, reported in studies worldwide [63]. A recurring observation is the increase in rates of infection and disease. The reason for this is unclear but may be caused by any of several contributing factors. The possibility exists that the apparent increase is either spurious or less significant than studies would suggest. Changes in clinician awareness leading to increased investigations, or laboratory methods leading to isolation and identification of previously unnoticed organisms, could play a role in this trend, and studies have been published that support [67] and refute [31] this argument. We believe such factors may contribute to but do not explain the significant increases that have been observed. A true increase could be related to the host, the pathogen, or some interaction between the two. Host changes leading to increased susceptibility could play an important role, with increased numbers of patients with inadequate defenses from diseases such as HIV infection, malignancy, or simply advanced age [31]. An increase in susceptibility could also relate to the decrease in infection with two other mycobacteria. It has been speculated that infection with TB [29,38] and Bacillus Calmette-Guerin (BCG) [19,68] may provide cross-immunity protecting against NTM infection. Many investigations have observed decreasing rates of TB concomitant with the increases in NTM. In addition, studies from Sweden [68] and the Czech Republic [19] have found that children who were not vaccinated with BCG had a far higher rate of extrapulmonary NTM infection. Potential changes in the pathogens include increases in NTM virulence, and it has been argued that this should be considered as a possible contributing factor [69]. Finally, an interaction between the host and pathogen could involve a major increase in pathogen exposure or potential inoculum size. This may be occurring secondary to the increase in popularity of showering as a form of bathing [66], a habit that greatly increases respiratory exposure to water contaminants. Several limitations of our review should be noted. We reviewed English-language reports and abstracts, probably leading to fewer data from non-English speaking regions, which may explain the paucity of studies from Africa, Eastern Europe, and most Asian nations. The heterogeneity of study methods in identifying cases and the lack of a uniformly applied definition of disease makes it difficult to compare rates between studies. Finally, the lack of systematic reporting of NTM infection in most nations limits the ability to derive accurate estimates of infection and disease. Regardless, there are more than adequate data to conclude that NTM disease rates vary widely depending on population and geographic location. NTM disease is clearly a major problem in certain groups, including patients with underlying lung disease and also in individuals with impaired immunity. The rates of NTM infection and disease are increasing, so the problem will likely continue to grow and become a far more important issue than current rates suggest.     

Overview of respiratory infection caused by nontuberculous mycobacteria

Recently, the clinical importance of nontuberculous mycobacteria (especially, Mycobacterium avium complex [MAC] respiratory infection) has been increasing. In addition, an official ATS/IDSA statement about diagnosis, treatment, and prevention of nontuberculous mycobacterial diseases has been published in February, 2007. In this review article, essence of this official statement will be introduced. In MAC respiratory infection, (i) primarily fibrocavitary disease, (ii) nodular/bronchiectatic disease, and (iii) hypersensitivity-like disease are identified, and (i) and (ii) are clinically important. Primarily fibrocavitary disease is characterized by cavitary lesions in upper lung fields in elderly subjects, smoking patients, or patients with pneumoconiosis. Nodular/bronchiectatic disease is characterized by centrilobular nodules and diffuse bronchiectases in the right middle lobe and the left lingula in middle-aged women. In addition, disseminated MAC disease in patients with acquired immunodeficiency syndrome should be considered. Further studies concerning transmission route as well as mechanism of MAC disease should be performed.     

非结核分支杆菌耐药基因的研究进展

非结核分支杆菌(ＮＴＭ)病的治疗是一个相当棘手的问题,因其对大多数抗结核药物均不敏感。近年来,随着ＮＴＭ感染情况日益严重,对于非结核分支杆菌耐药性问题的研究,便成为目前迫切需要解决的问题。最近,国外学者在ＮＴＭ耐药性基因研究方面作了大量的工作,现将其研究进展作一综述。一、ＮＴＭ与耐异烟肼(ＩＮＨ)ＩＮＨ是结核病治疗最重要的一线药物,它主要是通过抑制细菌分支菌酸的合成而起作用。但对于ＮＴＭ来说,ＩＮＨ并不是一个敏感药物。早年认为:耻垢和金色分支杆菌的ＩＮＨ耐药性可能与ＫａｔＧ基因编码产物———过氧化物-过氧化氢…     

Antibacterial activities of dendritic amphiphiles against nontuberculous mycobacteria

The anti-mycobacterial activities of nine series of dicarboxyl and tricarboxyl dendritic amphiphiles with one alkyl, two alkyl, and cholestanyl tails against Mycobacterium abscessus, Mycobacterium avium, Mycobacterium chelonae, Mycobacterium marinum and Mycobacterium smegmatis have been measured. The dendritic amphiphiles overcame the limited aqueous solubility of natural long-chain fatty acids, alcohols, and amines to enable profiling the susceptibilities of the different mycobacterial species to the physicochemical properties of these amphiphiles. Several dendritic amphiphiles showed strong anti-mycobacterial activity with high critical micelle concentrations and low hemolytic activities thereby offering platforms for the development of antibiotics of higher activity against nontuberculous mycobacteria.     

Isolation prevalence of pulmonary nontuberculous mycobacteria in Ontario in 2007

BACKGROUND:

The reported prevalence of pulmonary nontuberculous mycobacteria (NTM) infections is increasing.

OBJECTIVE:

To determine the ‘isolation prevalence’ of NTM in 2007 and compare it with previously published research that examined the increasing rates of isolation of NTM from clinical pulmonary specimens between 1997 and 2003.

METHODS:

Isolation prevalence was investigated retrospectively by reviewing a cohort of all positive pulmonary NTM culture results from the Tuberculosis and Mycobacteriology Laboratory, Public Health Laboratory (Toronto, Ontario) in 2007, which identifies at least 95% of NTM isolates in Ontario. Isolation prevalence was calculated as the number of persons with a pulmonary isolate in a calendar year divided by the contemporary population and expressed per 100,000 population. Changes in isolation prevalence from previous years were assessed for statistical significance using generalized linear models with a negative binomial distribution.

RESULTS:

In 2007, 4160 pulmonary isolates of NTM were collected from 2463 patients. The isolation prevalence of all species (excluding Mycobacterium gordonae) was 19 per 100,000 population in 2007 – an increase from previous observations reported for Ontario – corresponding to an average annual increase of 8.5% from 1997 to 2007 (P<0.0001). Average annual increases in isolation prevalence of Mycobacterium avium complex (8.8%, P<0.0001) and Mycobacterium xenopi (7.3%, P=0.0005) were largely responsible for the overall increase, while prevalence rates of rapidly growing mycobacteria remained relatively stable.

CONCLUSION:

The isolation prevalence of pulmonary NTM continues to increase significantly in Ontario, supporting the belief that pulmonary NTM disease is increasingly common.     

Epidemiology of infection by nontuberculous mycobacteria. VII. Absence of mycobacteria in southeastern groundwaters

Using the fluorochrome auramine-O, direct microscopic counts of log phase cells of Mycobacterium avium, M. intracellulare, and M. scrofulaceum (MAIS) group showed excellent correlations with viable spread-plate counts. Accordingly, an enumeration of total acid-fast and MAIS cells by stain and culture (respectively) in groundwaters from three United States regions that differ in their incidence of human infection by MAIS was undertaken. Of 30 state-monitored, undisinfected wells, 11 were in Georgia coastal plain (high incidence), 10 were in the Virginia coastal plain (intermediate incidence), and 9 were in Montgomery County, Virginia (low incidence). Total acid-fast cells ranged widely between 280 to 5,367 per ml among the groundwaters, and with one exception showed no correlations or trends between regions of different incidence of human infection, or to total bacterial cell counts or colony-forming units. The exception was that the proportions of acid-fast cells relative to total cells were higher in the Georgia groundwaters. However, despite the relatively high auramine-O counts, few mycobacteria were recovered by culture. Of 12 wells yielding mycobacteria, 9 yielded rapidly growing and 4 slowly growing mycobacteria. Only one well in Montgomery County, Virginia (region of low incidence) yielded a MAIS isolate, albeit at low density. This research supports the conclusion that clean groundwaters are unlikely sources of MAIS infection in humans in the southeastern United States.     

145株非结核分枝杆菌对10种药物的耐药性分析

目的了解我院非结核病患者分离的非结核分枝杆菌对10种药物的耐药状况。方法用MB/Bact 240分枝杆菌培养仪和改良罗氏管对患者的多种标本进行分枝杆菌分离培养鉴定,对分离到的分枝杆菌采用绝对浓度法对10种抗结核药物,利福平、异烟肼、乙胺丁醇、链霉素,利福喷丁、丙硫异烟肼、氧氟沙星、卷曲霉素、卡那霉素和对氨基水扬酸进行药物敏感性试验。结果 1722例患者的标本非结核分枝杆菌培养阳性145株,对10种药总耐药率97.2%（141/145）,单耐药率最高为异烟肼、链霉素和对氨基水扬酸,最低为氧氟沙星。结论非结核分枝杆菌耐药情况十分严重,应加强抗结核药物的耐药性监测;根据药敏试验选择科学有效的化疗方案。     

Epidemiology of infection by nontuberculous mycobacteria. VIII. Absence of mycobacteria in chicken litter

Overlap in the geographic distributions of (1) higher frequencies of persons reacting to antigens prepared from the Mycobacterium avium, M. intracellulare, and M. scrofulaceum (MAIS) group; (2) higher frequencies of isolation from natural waters and soils; (3) higher densities of farms producing broilers (chicken) in the southeastern United States raises the question of whether MAIS organisms occur abundantly in chicken litter (pine bark shavings containing avian fecal material) and whether litter may be a potential source of animal or human infection through its subsequent use as a fertilizer or feed supplement. We show here that potentially pathogenic mycobacteria were seldom recovered from chicken litter containing avian fecal material. Further, litter appears bactericidal to these organisms in that less than 1% of cells inoculated survived more than 6 wk, probably because of the high pH of litters.     

Regional differences of nontuberculous mycobacteria species in Ulsan,Korea

Background

In Korea recently, nontuberculous mycobacteria (NTM) have been more frequently isolated in respiratory specimens, while Mycobacterium tuberculosis (MTB) isolations have decreased. The major NTM lung disease species in Korea are M. intracellulare, M. avium, and M. abscessus, whereas M. kansasii is a rare species. This retrospective study was performed to determine if there are region-specific characteristics of lung disease-causing NTM species in Ulsan, a highly industrialized city in Korea.

Methods

Between January 2010 and July 2013, the results of all acid-fast bacilli (AFB) cultures of respiratory specimens performed at Ulsan University Hospital (Ulsan, Korea) were collected. NTM were identified and regional differences of NTM species were compared.

Results

AFB cultures were performed on 33,567 respiratory specimens, obtained from 10,208 patients, during the study period. Further, 10% of the specimens (3,287/33,567) were AFB culture-positive [MTB, 2,288/3,287 (70%); NTM 999/3,287 (30%)]. The proportion of NTM isolations gradually increased between 2010 and 2013, at 25% and 38%, respectively. The most common NTM species was M. intracellulare (356/999, 36%), followed by M. kansasii (295/999, 30%), M. avium (161/999, 16%), M. abscessus (117/999, 12%) and M. fortuitum (39/999, 4%). This trend was maintained throughout the study period.

Conclusions

In Ulsan, NTM isolation from respiratory specimens is increasing, consistent with previous studies performed in Korea. The distribution of respiratory NTM species, however, differed from previous studies that were performed in other regions of Korea: M. kansasii was the second most common NTM species in Ulsan. In Ulsan, there is a regional difference in the NTM species isolated.     

Analysis of distribution characteristics of clinical isolates of nontuberculous mycobacteria in a general hospital

正Objective To investigate the current prevalence of nontuberculous mycobacteria(NTM)in Shanghai,and to study the distribution characteristics of NTM clinical isolates,which may help to improve the diagnostic level of NTM and provide guidance for effective prevention and treatment of NTM infection.Methods Culture-positive isolates of clinical mycobacteria were collected from 2008     

Newly described or emerging human species of nontuberculous mycobacteria

The advent of molecular testing in the laboratory has brought about the recognition of multiple newly characterized mycobacterial species not previously recognizable with most standard techniques. Some of the species are nonpathogenic, but the majority may cause clinical disease. Each is likely to have its own biology, drug susceptibility pattern, and response to drug/surgical therapy. Thus, it is important to try to recognize these new species in the laboratory. A study of the phenotypic and genotypic characteristics of these new species also may help to elucidate the epidemiology and pathogenesis of these organisms. In addition, there are multiple emerging species of nontuberculous mycobacteria including M. ulcerans, M. haemophilum, M. xenopi, and M. malmoense. [table: see text] These species are being recognized increasingly as a cause of human disease and recovered within the laboratory. The clinician must learn about these new pathogens to recognize them clinically and assist the laboratory in their recovery.     

Respiratory infections associated with nontuberculous mycobacteria in non-HIV patients.

The incidence of nontuberculous mycobacteria (NTM) pulmonary diseases in HIV-negative patients was studied prospectively from January 1, 2001 to December 31, 2003 by 32 sentinel sites distributed throughout France. In total, 262 patients who yielded NTM isolates from respiratory clinical specimens, met the bacteriological, radiological and clinical criteria established by the American Thoracic Society for NTM respiratory disease. Among the 262 NTM isolates, 234 were slow-growing mycobacteria (125 Mycobacterium avium-intracellulare complex (MAC), 66 M. xenopi, 34 M. kansasii) and 28 were rapidly growing mycobacteria (25 M. abscessus complex). In the Paris area, M. xenopi was the most frequently isolated species, followed by MAC. Most patients (>50%), except those with M. kansasii, had underlying predisposing factors such as pre-existing pulmonary disease or immune deficiency. Asthenia, weight loss, chronic cough and dyspnoea were the most common clinical symptoms. The classical radiological appearance of NTM infections was indistinguishable from that observed in patients with pulmonary tuberculosis. In summary, the incidence of nontuberculous mycobacteria pulmonary infections in HIV-negative patients was estimated at 0.74, 0.73 and 0.72 cases per 100,000 inhabitants in 2001, 2002 and 2003, respectively.     

西安市非结核分枝杆菌感染现状调查分析

目的 了解西安市结核病患者中非结核分枝杆菌感染情况。方法 收集西安市胸科医院检验科分离培养的分枝杆菌临床菌株,利用两步PCR方法及PCR产物直接测序的方法进行菌种鉴定。结果 经鉴定发现,收集的202株分枝杆菌中有195株为结核分枝杆菌,3株为牛结核分枝杆菌,2份为鸟分枝杆菌,1份为堪萨斯分枝杆菌,1份为灰色链霉菌,非结核分枝杆菌感染率为1.5%(3/201)。结论 西安市尚存在一定比例非结核分枝杆菌感染,进一步菌种鉴定有利于临床正确诊断和合理用药治疗。     

非结核分枝杆菌性淋巴结炎病理学改变的初步研究

目的 探讨非结核分枝杆菌性淋巴结炎的特征性组织病理学改变.方法 建立非结核分枝杆菌性淋巴结炎的实验动物模型,光镜下观察组织病理学改变;对1例临床初步诊断为非结核分枝杆菌性淋巴结结核患者的病理组织标本经多重PCR方法检测筛选后,光镜下观察组织病理学改变.结果 非结核分枝杆菌感染所致的淋巴结炎的病理学改变与我们所熟知的淋巴结结核的病理学改变不完全相同.在动物模型中观察到的非结核分枝杆菌淋巴结炎的特征性病理学改变如下:(1)淋巴结内可见结节状肉芽肿形成,中央呈凝固性坏死,其中可见较多的中性粒细胞及其核碎屑.坏死区周围可见类上皮细胞、淋巴细胞、单核细胞,并可见纤维组织包裹.肉芽肿内外均可见朗汉斯巨细胞;(2)淋巴结内可见匐形性坏死,坏死旱长条状,中央部分为凝固性坏死,其中有大量中性粒细胞及其核碎屑,周围可见类上皮细胞、淋巴细胞及单核细胞,并可见纤维组织包绕;(3)淋巴结内可见星状和星芒状坏死.对初步诊断为非结核分枝杆菌性淋巴结炎的1例石蜡包埋组织标本,光镜下观察淋巴结内可见上皮样肉芽肿,匐行性坏死和星状坏死,坏死中可见大量中性粒细胞及其核碎屑,周围可见类上皮细胞、淋巴细胞、单核细胞、朗汉斯巨细胞;类上皮细胞的细胞核旱极性排列,周围并可见纤维组织或胶原组织包绕.结论 匐形性坏死、星状和星芒状坏夕匕、中央十酪样坏死中可见大量的中性粒细胞和粒细胞细胞核的碎屑、在中央坏死区的周围可见类上皮细胞胞核的极性排列,是非结核分枝杆菌性淋巴结炎的部分特征性组织病理学改变.