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.     

Pathophysiology of pulmonary nontuberculous mycobacterial (NTM) disease

In recent years, the incidence and prevalence of pulmonary nontuberculous mycobacterial (NTM) disease have increased worldwide. Although the reasons for this increase are unclear, dealing with this disease is essential. Pulmonary NTM disease is a chronic pulmonary infection caused by NTM bacteria, which are ubiquitous in various environments. In Japan, Mycobacterium avium-intracellulare complex (MAC) accounts for approximately 90% of the causative organisms of pulmonary NTM disease, which is also called pulmonary MAC disease or pulmonary MAI disease.It is important to elucidate the pathophysiology of this disease, which occurs frequently in postmenopausal women despite the absence of obvious immunodeficiency. The pathophysiology of this disease has not been fully elucidated; however, it can largely be divided into bacterial (environmental) and host-side problems. The host factors can be further divided into immune and airway problems. The authors suggest that the triangular relationship between bacteria, immunity, and the airway is important in the pathophysiology of this disease. The latest findings on the pathophysiology of pulmonary NTM disease are reviewed.     

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.     

Pulmonary infection with nontuberculous mycobacteria

Nontuberculous mycobacterial infections (NTM) are being increasingly recognized as a cause of chronic pulmonary disease. We recently reviewed the clinical, radiologic, and bacteriologic presentation of 89 adult patients ill enough to have been hospitalized between 1981 and 1985 with the diagnosis of NTM. Preexisting lung disease was present in 82% and alcohol abuse in 40%. Although M. avium complex was identified in 51% of the patients, M. xenopi, which is usually reported to occur infrequently, accounted for 38% of our cases and M. kansasii for only 9%. Treatment was limited by a high incidence of associated disease, in vitro drug resistance, drug toxicity, and a mortality rate of 32% within 18 months of admission. Nevertheless, bacteriologic conversion occurred in 29% of those treated. M. xenopi appears to be an important pathogen in southern Ontario. It differs from the other NTM by having a different pattern of in vitro drug resistance but not by its clinical or radiologic presentation.     

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.     

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.     

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.     

In vitro susceptibility testing of nontuberculous mycobacteria to streptomycin, kanamycin and enviomycin

In vitro susceptibility testing to streptomycin, kanamycin and enviomycin was carried out in nontuberculous mycobacteria and the results were compared with those of M. tuberculosis strains. Among nontuberculous mycobacteria tested, only M. xenopi strains exhibited similar minimal inhibitory concentration (MIC) values to streptomycin with M. tuberculosis strains. On the other hand, M. xenopi, M. malmoense and M. marinum strains showed the same MIC values to kanamycin with the MIC values for M. tuberculosis strains. The MICs of enviomycin for M. kansasii, M. malmoense, M. szulgai, M. xenopi and M. marinum strains were similar to those for M. tuberculosis strains. Out of 64 strains of M. avium complex, the MIC value similar to that for M. tuberculosis strains was shown in 16% of strains to streptomycin, in 42% of strains to kanamycin, and in 50% of strains to enviomycin.     

Pulmonary disease due to nontuberculous mycobacteria

Nontuberculous mycobacteria (NTM) are increasingly associated with pulmonary disease. This is a worldwide phenomenon and one that is not related just to better diagnostic techniques or HIV infection. The mode of transmission of NTM is not well defined, but environmental exposure may be the major factor. While most exposed and infected individuals never acquire NTM disease, some ostensibly immunocompetent persons will. Although our understanding of the pathogenesis of NTM disease is incomplete, we believe that both host and mycobacterial factors are involved. Among the former, interferon-gamma"trafficking" may well play a central role. When disease occurs, it is likely to present in one of three prototypical forms: a tuberculosis-like pattern often affecting older male smokers with COPD; nodular bronchiectasis classically occurring in middle-aged or older women who never smoked and present with cough; and hypersensitivity pneumonitis following environmental exposure. While Mycobacterium avium complex has been described with all three forms, many other NTM can produce one or another of them; variants of these prototypes also exist. Diagnosis of NTM disease relies on microbiology and chest CT scanning, and criteria to aid diagnosis are available. Treatment of disease depends on the species involved, extent and form of disease, and overall condition of the patient. Surgery for localized disease may be useful for those species expected to be refractory to medical therapy. Observation without treatment may be appropriate for some patients with slowly progressive disease that is expected to be particularly difficult to treat.     

Mycobacterial infections caused by nontuberculous mycobacteria

The purpose of this review is to familiarize a broad range of medical professionals with a relatively new and growing problem of infections caused by mycobacteria other than M. tuberculosis and M. leprae. There are at least 60 mycobacterial species that have been identified as causative agents of diseases in humans. They are all environmental bacteria, and they are not transmitted from person to person. The usual source of infection is water, soil, and aerosols developed from these sources. The probability of contracting such a disease depends not only on the closeness of interaction with an environment containing an enhanced concentration of bacteria but also and foremost on the sensitivity of an individual to these infections, which may depend on the state of immunity and other so-called predisposing conditions. Therefore, these infections are often referred to as opportunistic, and the group of organisms causing them are usually referred to as nontuberculous mycobacteria (NTM). This review addresses in a condensed form various aspects of these infections, including bacteriology, clinical manifestations, diagnosis, and therapy. The reader will be able to find more details on each of these topics in several reviews and some original papers cited in this article.     

Pulmonary disease caused by nontuberculous mycobacteria

Nontuberculous mycobacterial pulmonary infections have become more common in recent years. The diagnosis is often overlooked because the findings may be subtle or because the radiographic appearance may change slowly or not at all for long periods of time. As a rule, the radiographic findings of nontuberculous mycobacterial pulmonary infections are identical to those of tuberculosis in any given patient. Cavitary disease in nontuberculous mycobacterial infections is less common than in tuberculosis. The most common radiographic finding is one or more areas of clustered fibroproductive nodules that change slowly. Mycobacterium kansasii infection responds well to therapy, whereas M avium-intracellulare infection is difficult to treat. Awareness of the radiographic appearance of the nontuberculous mycobacterial pulmonary infections will facilitate their diagnosis so that appropriate therapy may be initiated before the disease is far advanced.     

Nosocomial infections due to nontuberculous mycobacteria.

Nontuberculous mycobacteria (NTM) are ubiquitous in the environment and cause colonization, infection, and pseudo-outbreaks in health care settings. Data suggest that the frequency of nosocomial outbreaks due to NTM may be increasing, and reduced hot water temperatures may be partly responsible for this phenomenon. Attention to adequate high-level disinfection of medical devices and the use of sterile reagents and biologicals will prevent most outbreaks. Because NTM cannot be eliminated from the hospital environment, and because they present an ongoing potential for infection, NTM should be considered in all cases of nosocomial infection, and careful surveillance must be used to identify potential outbreaks. Analysis of the species of NTM and the specimen source may assist in determining the significance of a cluster of isolates. Once an outbreak or pseudo-outbreak is suspected, molecular techniques should be applied promptly to determine the source and identify appropriate control measures.     

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.     

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.     

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…     

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。     

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.     

Lung disease due to the more common nontuberculous mycobacteria

As the prevalence of tuberculosis (TB) declines in the developed world, the proportion of mycobacterial lung disease due to nontuberculous mycobacteria (NTM) is increasing. It is not clear whether there is a real increase in prevalence or whether NTM disease is being recognized more often because of the introduction of more sensitive laboratory techniques, and that more specimens are being submitted for mycobacterial staining and culture as the result of a greater understanding of the role of NTM in conditions such as cystic fibrosis, posttransplantation and other forms of iatrogenic immunosuppression, immune reconstitution inflammatory syndrome, fibronodular bronchiectasis, and hypersensitivity pneumonitis. The introduction of BACTEC liquid culture systems (BD; Franklin Lakes, NJ) and the development of nucleic acid amplification and DNA probes allow more rapid diagnosis of mycobacterial disease and the quicker differentiation of NTM from TB isolates. High-performance liquid chromatography, polymerase chain reaction, and restriction fragment length polymorphism analysis have helped to identify new NTM species. Although treatment regimens that include the newer macrolides are more effective than the earlier regimens, failure rates are still too high and relapse may occur after apparently successful therapy. Moreover, treatment regimens are difficult to adhere to because of their long duration, adverse effects, and interactions with the other medications that these patients require. The purpose of this article is to review the common presentations of NTM lung disease, the conditions associated with NTM lung disease, and the clinical features and treatment of the NTM that most commonly cause lung disease.