Mycobacterial disease, immunosuppression, and acquired immunodeficiency syndrome

Mycobacterium abscessus: insights from a bioinformatic perspective

Mycobacterium abscessus is a nontuberculous mycobacterium, associated with broncho-pulmonary infections in individuals suffering from cystic fibrosis, bronchiectasis, and pulmonary diseases. The risk factors for transmission include biofilms, contaminated water resources, fomites, and infected individuals. M. abscessus is extensively resistant to antibiotics. To date, there is no vaccine and combination antibiotic therapy is followed. However, drug toxicities, low cure rates, and high cost of treatment make it imperfect. Over the last 20 years, bioinformatic studies on M. abscessus have advanced our understanding of the pathogen. This review integrates knowledge from the analysis of genomes, microbiomes, genomic variations, phylogeny, proteome, transcriptome, secretome, antibiotic resistance, and vaccine design to further our understanding. The utility of genome-based studies in comprehending disease progression, surveillance, tracing transmission routes, and epidemiological outbreaks on a global scale has been highlighted. Furthermore, this review underlined the importance of using computational methodologies for pinpointing factors responsible for pathogen survival and resistance. We reiterate the significance of interdisciplinary research to fight M. abscessus. In a nutshell, the outcome of computational studies can go a long way in creating novel therapeutic avenues to control M. abscessus mediated pulmonary infections.

Molecular Epidemiological Characteristics of Mycobacterium abscessus Complex Derived from Non-Cystic Fibrosis Patients in Japan and Taiwan

Mycobacterium abscessus complex (MABC) is a group of emerging, highly antimicrobial-resistant non-tuberculous mycobacteria. Specific MABC clones are spreading globally in patients with cystic fibrosis (CF); however, associated genomic epidemiology is lacking in East Asia, with very few patients with CF. Here, we investigated MABC populations derived from non-CF patients in Japan and Taiwan. Analysis of whole-genome sequencing data of 220 MABC isolates revealed that 112, 105, and 3 were M. abscessus subsp. abscessus (ABS), M. abscessus subsp. massiliense (MAS), and M. abscessus subsp. bolletii (BOL), respectively. Moreover, >50% of ABS and >70% of MAS were related to four predominant clones in the region. Known mutations conferring macrolide resistance were rare (1.4%) and were not enriched in the predominant clones. Conversely, the macrolide-susceptible erm(41) T28C mutation was significantly enriched in one predominant ABS clone. The most predominant ABS clone was genetically related to the previously described dominant circulating clone (DCC)1 in patients with CF, whereas no isolates were related to DCC2; isolates related to DCC3 were not necessarily predominant in our sample set. We found that the erm(41) T28C mutants spread globally, and some of them reacquired the functional erm(41) gene through both point mutation and recombination. This study revealed predominant MABC clones in Japan and Taiwan and their relationship with the globally superadding clones in the patient community with CF. Our study provides insights into the genetic characteristics of globally dominant and area-specific strains isolated from patients with or without CF and differences between globally spread and regionally specific strains.

IMPORTANCE Members of Mycobacterium abscessus complex (MABC) are frequently isolated from patients. Studies have reported that predominant clones of MABC (known as dominant circulating clones; DCCs) are distributed worldwide and transmitted from humans to humans in patients with cystic fibrosis (CF). However, associated genomic epidemiology has not yet been conducted in East Asia, including Japan and Taiwan, where there are only a few patients with CF. Using whole-genome sequencing data derived from non-CF patients in Japan and Taiwan, we revealed prevalent clones and the incidence of macrolide resistance-associated mutations in the MABC population in this region. We also clarified the associations between these predominant clones and DCCs in the global CF patient community. Our results would assist further studies in elucidating the genetic characteristics of strains isolated from patients with or without CF, the differences between globally spread and regionally specific strains, and the adaptive evolution of MABC within the host.

Rough and smooth variants of Mycobacterium abscessus are differentially controlled by host immunity during chronic infection of adult zebrafish

Prevalence of Mycobacterium abscessus infections is increasing in patients with respiratory comorbidities. After initial colonisation, M. abscessus smooth colony (S) variants can undergo an irreversible genetic switch into highly inflammatory, rough colony (R) variants, often associated with a decline in pulmonary function. Here, we use an adult zebrafish model of chronic infection with R and S variants to study M. abscessus pathogenesis in the context of fully functioning host immunity. We show that infection with an R variant causes an inflammatory immune response that drives necrotic granuloma formation through host TNF signalling, mediated by the tnfa, tnfr1 and tnfr2 gene products. T cell-dependent immunity is stronger against the R variant early in infection, and regulatory T cells associate with R variant granulomas and limit bacterial growth. In comparison, an S variant proliferates to high burdens but appears to be controlled by TNF-dependent innate immunity early during infection, resulting in delayed granuloma formation. Thus, our work demonstrates the applicability of adult zebrafish to model persistent M. abscessus infection, and illustrates differences in the immunopathogenesis induced by R and S variants during granulomatous infection.

The pathogen Mycobacterium abscessus can switch from a smooth colony form (S) into a highly inflammatory, rough colony form (R) during infection. Here, Kam et al. use an adult zebrafish model of M. abscessus chronic infection to illustrate differences in the immunopathogenesis induced by R and S variants.

Initiation of Post-Primary Tuberculosis of the Lungs: Exploring the Secret Role of Bone Marrow Derived Stem Cells

Mycobacterium tuberculosis (Mtb), the causative organism of pulmonary tuberculosis (PTB) now infects more than half of the world population. The efficient transmission strategy of the pathogen includes first remaining dormant inside the infected host, next undergoing reactivation to cause post-primary tuberculosis of the lungs (PPTBL) and then transmit via aerosol to the community. In this review, we are exploring recent findings on the role of bone marrow (BM) stem cell niche in Mtb dormancy and reactivation that may underlie the mechanisms of PPTBL development. We suggest that pathogen's interaction with the stem cell niche may be relevant in potential inflammation induced PPTBL reactivation, which need significant research attention for the future development of novel preventive and therapeutic strategies for PPTBL, especially in a post COVID-19 pandemic world. Finally, we put forward potential animal models to study the stem cell basis of Mtb dormancy and reactivation.

Prevalence of Mycobacterium avium subspecies paratuberculosis (MAP) infection in suspected diarrhoeic buffaloes and cattle reporting at Veterinary University in India

Murrah buffaloes, best breed for milk production are native of Haryana state. They contributes significantly to the farmer's income, livelihood and food (milk and meat) security, in the semi-tropical regions of North India. Johne's disease though endemic in the domestic livestock of the country, but reports are not available in the buffaloes suffering from morbidity due to progressive weakness and diarrhoea. We estimated the status of JD in diarrhoeic buffaloes and cattle reporting at Veterinary Clinical Complex of Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, Haryana, India, using conventional, serological and PCR assays.141 buffaloes suffering from chronic diarrhoea were screened to estimate sero-prevalence of MAP and 50.0 % young and 53.52 % adult animals were positive. Of 14 cattle screened, none of the young and 66.6 % adult cows were positive. In buffaloes, 66.1 and 6.77 %, fecal samples were positive in microscopy and IS900 PCR, respectively. Sero-prevalence of JD was very high in diarrhoeic buffaloes and cattle from Haryana state of India.Buffaloes positive for Mycobacterium avium subspecies paratuberculosis (MAP) infection had reduced total leukocyte count and lymphocytes.

Non-tuberculous mycobacteria and the rise of Mycobacterium abscessus

Infections caused by non-tuberculous mycobacteria (NTM) are increasing globally and are notoriously difficult to treat due to intrinsic resistance of these bacteria to many common antibiotics. NTM are diverse and ubiquitous in the environment, with only a few species causing serious and often opportunistic infections in humans, including Mycobacterium abscessus. This rapidly growing mycobacterium is one of the most commonly identified NTM species responsible for severe respiratory, skin and mucosal infections in humans. It is often regarded as one of the most antibiotic-resistant mycobacteria, leaving us with few therapeutic options. In this Review, we cover the proposed infection process of M. abscessus, its virulence factors and host interactions and highlight the commonalities and differences of M. abscessus with other NTM species. Finally, we discuss drug resistance mechanisms and future therapeutic options. Taken together, this knowledge is essential to further our understanding of this overlooked and neglected global threat.

Early onset of nontuberculous mycobacterial pulmonary disease contributes to the lethal outcome in lung transplant recipients: report of two cases and review of the literature

Lung transplant (LuTx) recipients represent a population at risk of nontuberculous mycobacterial pulmonary disease (NTM-PD). Yet the risk factors, the timing of NTM-PD after transplantation, and the association with allograft dysfunction all remain poorly defined. We report 2 cases of early-onset NTM-PD and review the literature, focusing on NTM-PD in LuTx recipients not colonized with NTM prior to transplantation. In addition, we summarize the main characteristics and differences between early- and late-onset disease.

Epidemiology and Ecology of Opportunistic Premise Plumbing Pathogens: Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa

BACKGROUND

Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa are opportunistic premise plumbing pathogens (OPPPs) that persist and grow in household plumbing, habitats they share with humans. Infections caused by these OPPPs involve individuals with preexisting risk factors and frequently require hospitalization.

OBJECTIVES

The objectives of this report are to alert professionals of the impact of OPPPs, the fact that 30% of the population may be exposed to OPPPs, and the need to develop means to reduce OPPP exposure. We herein present a review of the epidemiology and ecology of these three bacterial OPPPs, specifically to identify common and unique features.

METHODS

A Water Research Foundation-sponsored workshop gathered experts from across the United States to review the characteristics of OPPPs, identify problems, and develop a list of research priorities to address critical knowledge gaps with respect to increasing OPPP-associated disease.

DISCUSSION

OPPPs share the common characteristics of disinfectant resistance and growth in biofilms in water distribution systems or premise plumbing. Thus, they share a number of habitats with humans (e.g., showers) that can lead to exposure and infection. The frequency of OPPP-infected individuals is rising and will likely continue to rise as the number of at-risk individuals is increasing. Improved reporting of OPPP disease and increased understanding of the genetic, physiologic, and structural characteristics governing the persistence and growth of OPPPs in drinking water distribution systems and premise plumbing is needed.

CONCLUSIONS

Because broadly effective community-level engineering interventions for the control of OPPPs have yet to be identified, and because the number of at-risk individuals will continue to rise, it is likely that OPPP-related infections will continue to increase. However, it is possible that individuals can take measures (e.g., raise hot water heater temperatures and filter water) to reduce home exposures.

Diffusible signal factor (DSF) quorum sensing signal and structurally related molecules enhance the antimicrobial efficacy of antibiotics against some bacterial pathogens

Background

Extensive use of antibiotics has fostered the emergence of superbugs that are resistant to multidrugs, which becomes a great healthcare and public concern. Previous studies showed that quorum sensing signal DSF (diffusible signal factor) not only modulates bacterial antibiotic resistance through intraspecies signaling, but also affects bacterial antibiotic tolerance through interspecies communication. These findings motivate us to exploit the possibility of using DSF and its structurally related molecules as adjuvants to influence antibiotic susceptibility of bacterial pathogens.

Results

In this study, we have demonstrated that DSF signal and its structurally related molecules could be used to induce bacterial antibiotic susceptibility. Exogenous addition of DSF signal (cis-11-methyl-2-dodecenoic acid) and its structural analogues could significantly increase the antibiotic susceptibility of Bacillus cereus, possibly through reducing drug-resistant activity, biofilm formation and bacterial fitness. The synergistic effect of DSF and its structurally related molecules with antibiotics on B. cereus is dosage-dependent. Combination of DSF with gentamicin showed an obviously synergistic effect on B. cereus pathogenicity in an in vitro model. We also found that DSF could increase the antibiotic susceptibility of other bacterial species, including Bacillus thuringiensis, Staphylococcus aureus, Mycobacterium smegmatis, Neisseria subflava and Pseudomonas aeruginosa.

Conclusion

The results indicate a promising potential of using DSF and its structurally related molecules as novel adjuvants to conventional antibiotics for treatment of infectious diseases caused by bacterial pathogens.

Identification of nontuberculous mycobacteria isolated from clinical sterile sites in patients at a university hospital in the city of Rio de Janeiro, Brazil

OBJECTIVE

To identify nontuberculous mycobacteria (NTM) isolated from sterile sites in patients hospitalized between 2001 and 2006 at the Clementino Fraga Filho University Hospital, located in the city of Rio de Janeiro, Brazil.

METHODS

During the study period, 34 NTM isolates from sterile sites of 14 patients, most of whom were HIV-positive, were submitted to phenotypic identification and hsp65 PCR-restriction enzyme analysis (PRA).

RESULTS

Most isolates were identified as Mycobacterium avium, followed by M. monacense, M. kansasii, and M. abscessus.

CONCLUSIONS

The combination of PRA, a relatively simple and inexpensive method, with the evaluation of a few phenotypic characteristics can allow NTM to be accurately identified in the routine of clinical laboratories.

Mycobacteria in terrestrial small mammals on cattle farms in Tanzania

The control of bovine tuberculosis and atypical mycobacterioses in cattle in developing countries is important but difficult because of the existence of wildlife reservoirs. In cattle farms in Tanzania, mycobacteria were detected in 7.3% of 645 small mammals and in cow's milk. The cattle farms were divided into “reacting” and “nonreacting” farms, based on tuberculin tests, and more mycobacteria were present in insectivores collected in reacting farms as compared to nonreacting farms. More mycobacteria were also present in insectivores as compared to rodents. All mycobacteria detected by culture and PCR in the small mammals were atypical mycobacteria. Analysis of the presence of mycobacteria in relation to the reactor status of the cattle farms does not exclude transmission between small mammals and cattle but indicates that transmission to cattle from another source of infection is more likely. However, because of the high prevalence of mycobacteria in some small mammal species, these infected animals can pose a risk to humans, especially in areas with a high HIV-prevalence as is the case in Tanzania.

Genomic comparison of PE and PPE genes in the Mycobacterium avium complex

The Mycobacterium avium complex (MAC) comprises genomically similar but phenotypically divergent bacteria that inhabit diverse environments and that cause disease in different hosts. In this study, a whole-genome approach was used to examine the polymorphic PE (Pro-Glu) and PPE (Pro-Pro-Glu) gene families, implicated in immunostimulation and virulence. The four major groups of MAC organisms were examined, including the newly sequenced type strains of M. intracellulare and M. avium subsp. avium, plus M. avium subsp. paratuberculosis and M. avium subsp. hominissuis, for the purpose of finding genetic differences that could be exploited to design diagnostic tests specific to these groups and that could help explain their divergence in pathogenesis and host specificity. Unique and missing PPE genes were found in all MAC members except M. avium subsp. avium. Only M. intracellulare had a unique PE gene. Apart from this, most PE and PPE sequences were conserved, with average nucleotide sequence identities of 99.1 and 98.1%, respectively, among the M. avium subspecies, but only 82.9 and 79.7% identities with the PE and PPE sequences of M. intracellulare, respectively. A detailed analysis of the amino acid sequences was performed between M. avium subsp. paratuberculosis and M. avium subsp. hominissuis. Most differences were detected in the PPE proteins, with amino acid substitutions and frame shifts leading to unique amino acid sequences. In conclusion, several unique PPE proteins were identified in MAC organisms next to numerous polymorphisms in both the PE and PPE gene families. These substantial differences could help explain the divergence in phenotypes within the MAC and could lead to diagnostic tests with better discriminatory abilities.

In-vitro antimycobacterial drug susceptibility testing of non-tubercular mycobacteria by tetrazolium microplate assay

BACKGROUND

Non-tubercular mycobacteria (NTM) has not been given due attention till the recent epidemic of HIV. This has led to increasing interest of health care workers in their biology, epidemiology and drug resistance. However, timely detection and drug susceptibility profiling of NTM isolates are always difficult in resource poor settings like India. Furthermore, no standardized methodology or guidelines are available to reproduce the results with clinical concordance.

OBJECTIVE

To find an alternative and rapid method for performing the drug susceptibility assay in a resource limited settings like India, we intended to evaluate the utility of Tetrazolium microplate assay (TEMA) in comparison with proportion method for reporting the drug resistance in clinical isolates of NTM.

METHODS

A total of fifty-five NTM isolates were tested for susceptibility against Streptomycin, Rifampicin, Ethambutol, Ciprofloxacin, Ofloxacin, Azithromycin, and Clarithromycin by TEMA and the results were compared with agar proportion method (APM).

RESULTS

Of the 55 isolates, 23 (41.8%) were sensitive to all the drugs and the remaining 32 (58.2%) were resistant to at least one drug. TEMA had very good concordance with APM except with minor discrepancies. Susceptibility results were obtained in the median of 5 to 9 days by TEMA. The NTM isolates were highly sensitive against Ofloxacin (98.18% sensitive) and Ciprofloxacin (90.09% sensitive). M. mucogenicum was sensitive only to Clarithromycin and resistant to all the other drugs tested. The concordance between TEMA and APM ranged between 96.4 - 100%.

CONCLUSION

Tetrazolium Microplate Assay is a rapid and highly reproducible method. However, it must be performed only in tertiary level Mycobacteriology laboratories with proper bio-safety conditions.

In-vitro antimycobacterial drug susceptibility testing of non-tubercular mycobacteria by tetrazolium microplate assay

BACKGROUND

Non-tubercular mycobacteria (NTM) has not been given due attention till the recent epidemic of HIV. This has led to increasing interest of health care workers in their biology, epidemiology and drug resistance. However, timely detection and drug susceptibility profiling of NTM isolates are always difficult in resource poor settings like India. Furthermore, no standardized methodology or guidelines are available to reproduce the results with clinical concordance.

OBJECTIVE

To find an alternative and rapid method for performing the drug susceptibility assay in a resource limited settings like India, we intended to evaluate the utility of Tetrazolium microplate assay (TEMA) in comparison with proportion method for reporting the drug resistance in clinical isolates of NTM.

METHODS

A total of fifty-five NTM isolates were tested for susceptibility against Streptomycin, Rifampicin, Ethambutol, Ciprofloxacin, Ofloxacin, Azithromycin, and Clarithromycin by TEMA and the results were compared with agar proportion method (APM).

RESULTS

Of the 55 isolates, 23 (41.8%) were sensitive to all the drugs and the remaining 32 (58.2%) were resistant to at least one drug. TEMA had very good concordance with APM except with minor discrepancies. Susceptibility results were obtained in the median of 5 to 9 days by TEMA. The NTM isolates were highly sensitive against Ofloxacin (98.18% sensitive) and Ciprofloxacin (90.09% sensitive). M. mucogenicum was sensitive only to Clarithromycin and resistant to all the other drugs tested. The concordance between TEMA and APM ranged between 96.4 - 100%.

CONCLUSION

Tetrazolium Microplate Assay is a rapid and highly reproducible method. However, it must be performed only in tertiary level Mycobacteriology laboratories with proper bio-safety conditions.

First detection of mycobacteria in African rodents and insectivores, using stratified pool screening

With the rising number of patients with human immunodeficiency virus (HIV)/AIDS in developing countries, the control of mycobacteria is of growing importance. Previous studies have shown that rodents and insectivores are carriers of mycobacteria. However, it is not clear how widespread mycobacteria are in these animals and what their role is in spreading them. Therefore, the prevalence of mycobacteria in rodents and insectivores was studied in and around Morogoro, Tanzania. Live rodents were trapped, with three types of live traps, in three habitats. Pieces of organs were pooled per habitat, species, and organ type (stratified pooling); these sample pools were examined for the presence of mycobacteria by PCR, microscopy, and culture methods. The mycobacterial isolates were identified using phenotypic techniques and sequencing. In total, 708 small mammals were collected, 31 of which were shrews. By pool prevalence estimation, 2.65% of the animals were carriers of mycobacteria, with a higher prevalence in the urban areas and in Cricetomys gambianus and the insectivore Crocidura hirta. Nontuberculous mycobacteria (Mycobacterium chimaera, M. intracellulare, M. arupense, M. parascrofulaceum, and Mycobacterium spp.) were isolated from C. gambianus, Mastomys natalensis, and C. hirta. This study is the first to report findings of mycobacteria in African rodents and insectivores and the first in mycobacterial ecology to estimate the prevalence of mycobacteria after stratified pool screening. The fact that small mammals in urban areas carry more mycobacteria than those in the fields and that potentially pathogenic mycobacteria were isolated identifies a risk for other animals and humans, especially HIV/AIDS patients, that have a weakened immune system.

Synthesis of 1-[3-(4-benzotriazol-1/2-yl-3-fluoro-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-3-substituted-thiourea derivatives as antituberculosis agents

In continuation of our research program for new antituberculosis drugs, we have designed, synthesized and evaluated antimycobacterial activity of new series of 1-[3-(4-benzotriazol-1/2-yl-3-fluoro-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-3-substituted-thiourea derivatives against different Mycobacterium species i.e. M. tuberculosis, M. avium and M. intracellulare in an agar dilution method. Compound 17 exhibited excellent antimycobacterial activity (in vitro) against drug sensitive and resistant clinical isolates of M. tuberculosis. Its MIC value is equivalent to linezolid and superior to isoniazid against all these strains.

Pulmonary tuberculosis in lung and heart-lung transplantation: fifteen years of experience in a single center in Spain

The increase in the number of solid organ transplants has resulted in an increased incidence of opportunistic infections, including infection by typical and atypical mycobacteria, with risk of developing tuberculosis. Pretransplant chemoprophylaxis with isoniazid has become increasingly common in an attempt to prevent the disease. The source of infection in tuberculosis (TB) may be difficult to identify. Infection may be caused by reactivation of a primary infection in the recipient, reactivation of a lesion from the donor lung, or primary infection. There are few reports on TB in lung transplantation. Incidence in the reported series ranges from 6.5% to 10%. Our series of 7 patients out of a total 271 patients (2.58%) represents a rate higher than reported for the general Spanish population, 26.7/10(5) inhabitants and for lung transplant candidates (0.18%). Our aim was to evaluate the incidence, clinical signs, and outcome of TB in our series of patients undergoing lung transplantation in the 15 years since inception of the program (February 1990 to December 2004). Morbidity and mortality was high (42.8%), but limited to patients in whom treatment was not administered or could not be successfully completed. However, early detection and treatment are essential.

Synthesis of isonicotinic acid N'-arylidene-N-[2-oxo-2-(4-aryl-piperazin-1-yl)-ethyl]-hydrazides as antituberculosis agents

A new series of antituberculosis agents 6-9 was designed, synthesized and evaluated for antituberculosis activity against Mycobacterium tuberculosis H37Rv and clinical isolates in an agar dilution method. Compound 9h showed comparable in vitro activity (MIC) to isoniazid against M. tuberculosis H37Rv and clinical isolates (sensitive strains) and superior activity against resistant strains of M. tuberculosis.

Antimycobacterial activity of new 3-substituted 5-(pyridin-4-yl)-3H-1,3,4-oxadiazol-2-one and 2-thione derivatives. Preliminary molecular modeling investigations

3H-1,3,4-Oxadiazole-2-thione and 3H-1,3,4-oxadiazol-2-one derivatives were synthesized and tested for their in vitro antimycobacterial activity. Oxadiazolone derivatives showed an interesting antimycobacterial activity against the tested strain of Mycobacterium tuberculosis H(37)Rv, whereas the corresponding thione derivatives were devoid of activity. Molecular modeling investigations showed that the active compounds may interact at the active site of the mycobacterial cytochrome P450-dependent sterol 14alpha-demethylase in the sterol biosynthesis pathway and that their binding free energy values are in agreement with their MIC values.

In vitro advanced antimycobacterial screening of isoniazid-related hydrazones, hydrazides and cyanoboranes: Part 14

As a part of an ongoing search for new isoniazid-related isonicotinoylhydrazones (ISNEs), 2'-monosubstituted isonicotinohydrazides and cyanoboranes, some analogues belonging to these three series of compounds were further evaluated in an in vitro advanced antimycobacterial screening. The results here reported allowed us to extend their structure-activity relationships. A general correlation emerged between their lipophilicity and effectiveness against intracellular M. tuberculosis. On the whole, the most interesting result of this research was that some hydrazides and ISNEs proved to be more effective antimycobacterial agents than parental isoniazid in a TB-infected macrophage model.

In vitro advanced antimycobacterial screening of cobalt(II) and copper(II) complexes of fluorinated isonicotinoylhydrazones

The in vitro antimycobacterial activity of cobalt(II) and copper(II) complexes of some fluorinated isonicotinoylhydrazones was evaluated in a TB-infected macrophage model; all metalcomplexes exhibited excellent activity against Mycobacterium tuberculosis Erdman growing within macrophages, at concentrations much lower than in culture media. Moreover complexes 1b and 2a displayed EC(99) values lower than that of the parent-drug, isoniazid. In addition, all tested metalchelates significantly inhibited the growth of single-drug-resistant M. tuberculosis strains; complexes 1a and 2a also possessed moderate activity against Mycobacterium avium complex.

High-Polarity Mycobacterium avium-Derived Lipids Interact with Murine Macrophage Lipid Rafts

Cholesterol- and sphingolipid-rich membrane microdomains (lipid rafts) are widely recognized as portals for pathogenic micro-organisms. A growing body of evidence demonstrates mobilization of host plasma cell membrane lipid rafts towards the site of contact with several pathogens as well as a strict dependence on cholesterol for appropriate internalization. The fate of lipid rafts once the pathogen has been internalized and the nature of the pathogen components that interact with them is however less understood. To address both these issues, infection of the J774 murine cell line with Mycobacterium avium was used as a model. After demonstrating that M. avium induces lipid raft mobilization and that M. avium infects J774 by a cholesterol-dependent mechanism, it is shown here that mycobacterial phagosomes harbour lipid rafts, which are, at least in part, of plasma cell membrane origin. On the other hand, by using latex microbeads coated with any of the three fractions of M. avium-derived lipids of different polarity, we provide evidence that high-polarity, in contrast to low-polarity and intermediate-polarity, mycobacterial lipids or uncoated latex beads have a strong capacity to induce lipid raft mobilization. These results suggest that high-polarity mycobacterial lipid(s) interact with host cell cholesterol-enriched microdomains which may in turn influence the course of infection.

Correlation of virulence, lung pathology, bacterial load and delayed type hypersensitivity responses after infection with different Mycobacterium tuberculosis genotypes in a BALB/c mouse model

One of the most intriguing aspects of tuberculosis is that the outcome of an infection with M. tuberculosis (TB) is highly variable between individuals. The possibility of differences in virulence between M. tuberculosis strains or genotypes has only recently been studied. There is evidence of multifactorial genetic predisposition in humans that influences the susceptibility to tuberculosis. A better understanding of differences in virulence between M. tuberculosis genotypes could be important with regard to the efforts at TB control and the development of improved antituberculosis vaccines. Survival, lung pathology, bacterial load and delayed type hypersensitivity (DTH) responses of BALB/c mice after intratracheal infection with any of 19 different M. tuberculosis complex strains of 11 major genotype families were studied. The results indicate that among genetically different M. tuberculosis strains a very broad response was present with respect to virulence, pathology, bacterial load and DTH. 'Low'-responders were the H37Rv, Canetti, Beijing-1 strains, while Beijing-2,3, Africa-2 and Somalia-2 strains were 'high'-responders. A severe pathological response correlates with a high mortality and a high CFU counts in lungs, but poorly with the degree of the DTH response.

Synthesis of the Glycopeptidolipid of Mycobacterium avium Serovar 4: First Example of a Fully Synthetic C-Mycoside GPL

The preparation of the glycopeptidolipid (GPL) present in the cell wall of Mycobacterium aviumSerovar 4, namely 3,4-di-O-Me-alpha-L-Rhap-(1-->1)[R-C(21)H(43)CH(OH)CH(2)CO-D-Phe-[4-O-Me-alpha-L-Rhap-(1-->4)-2-O-Me-alpha-L-Fucp-(1-->3)-alpha-L-Rhap-(1-->2)-6-deoxy-alpha-L-Talp-(1-->3)]-D-allo-Thr-D-Ala-L-Alaol] (1), is described. The synthesis was based on the disconnection of the final structure into four building blocks, an L-rhamnosyl pseudodipeptide, a 6-deoxy-L-talosyl dipeptide, a trisaccharide donor, and a 3-hydroxyalkanoic acid. The key steps are the creation of the glycosidic linkage between the trisaccharide donor, used as a pentenyl glycoside, and the 6-deoxy-L-talose unit of an appropriate D-Phe-O-(6-deoxy-L-talosyl)-D-allo-Thr derivative and the final coupling of the two glycodipeptide fragments. Pentenyl glycosides were shown to provide useful donors in several glycosylation steps. This work constitutes the first synthesis of the full structure of a so-called "polar mycoside C" GPL.

The combination of plasmid interleukin-12 with a single DNA vaccine is more effective than Mycobacterium bovis (bacille Calmette-Guèrin) in protecting against systemic Mycobacterim avium infection

Sub-unit vaccines utilizing purified mycobacterial proteins or DNA vaccines induce partial protection against mycobacterial infections. For example, immunization with DNA vaccines expressing the gene for the immunodominant 35000 MW protein, common to Mycobacterium avium and Mycobacterium leprae but absent from the Mycobacterium tuberculosis complex, conferred significant protection against infection with either virulent M. avium or M. leprae in mice. However, the level of protection was equivalent to that obtained with the viable, attenuated vaccine, Mycobacterium bovis, bacille Calmette-Guèrin (BCG). The cytokine, interleukin (IL)-12, is essential for priming naïve CD4+ T lymphocytes to differentiate into interferon-gamma (IFN-gamma)-secreting T cells. We have used a novel self-splicing vector expressing both chains of murine IL-12 to determine if plasmid IL-12 would increase the efficacy of a vaccine expressing the M. avium 35000 MW protein (DNA-Av35). Co-immunization with p2AIL-12 and DNA-Av35 led to a significant increase in the number of antigen-specific IFN-gamma secreting cells and total amount of IFN-gamma released, but a concomitant fall in the antibody response to the 35000 MW protein. This pattern of response was associated with enhanced clearance of M. avium from the liver and spleen of coimmunized mice, and was significantly more effective than BCG or DNA-Av35. alone. Following M. avium challenge there was significant increase in the expansion of the 35000 MW antigen-reactive T cells in the coimmunized mice. Therefore, plasmid-delivered IL-12 acts as an effective adjuvant to increase the protective efficacy of a single DNA vaccine against M. avium infection above that achieved by BCG, and this strategy may improve the efficacy of subunit vaccines against M. leprae and M. tuberculosis.

Mycobacterium avium genes expressed during growth in human macrophages detected by selective capture of transcribed sequences (SCOTS)

Selective capture of transcribed sequences (SCOTS) has been employed to identify 54 cDNA molecules that represent 46 genes that are expressed by Mycobacterium avium during growth in human macrophages. Some cDNA molecules correspond to genes that are apparently expressed 48 h after infection of macrophages, while others correspond to genes expressed 110 h after infection, and still others correspond to genes expressed throughout the course of infection in our model system. Genes expressed by M. avium during growth in macrophages include genes encoding enzymes of several biosynthetic pathways (pyrimidines, mycobactin, and polyketides); genes that encode enzymes involved in intermediary metabolism, energy metabolism (tricarboxylic acid cycle, glyoxalate shunt), and nitrogen metabolism; and genes that encode regulatory proteins. A number of genes of unknown function were also identified, including genes that code for proteins similar to members of the PPE family of proteins of Mycobacterium tuberculosis and proteins similar to those encoded by the M. tuberculosis mce genes, which have been previously associated with mycobacterial virulence. The SCOTS technique, followed by enrichment for cDNA molecules that are up-regulated or are uniquely expressed by M. avium during growth in human macrophages (compared to growth in laboratory broth culture), allows recovery and identification of a greater diversity of cDNA molecules than does subtractive hybridization between cDNA mixtures from macrophage-grown and broth-grown M. avium. Data are presented demonstrating the reproducibility of recovery of a subset of cDNA molecules from cDNA mixtures purified by SCOTS on several different occasions. These results further demonstrate the beneficial utility of the SCOTS technique for identifying genes whose products are needed for successful survival and growth by an organism in a specific environment.

In vitro antimycobacterial activities of 2'-monosubstituted isonicotinohydrazides and their cyanoborane adducts

As a result of our search for new isoniazid derivatives with extended spectra of activity, we evaluated the in vitro antimycobacterial activities of isonicotinohydrazides (compounds 2) and their cyanoborane adducts (compounds 3), both obtained by the reaction of isonicotinoylhydrazones (compounds 1) with sodium cyanoborohydride. Most of the tested compounds displayed moderate to high activity against Mycobacterium tuberculosis H37Rv, with MICs ranging from 0.2 to 12.5 microg/ml. In particular, some hydrazides showed activity similar to that of rifampin (MIC = 0.2 microg/ml) and rather low cytotoxicity, so that they were generally shown to possess high safety indices. In contrast, the coordination to a cyanoborane (BH(2)CN) group (compounds 3) in general brought about a decrease in antimycobacterial activity, while cytotoxicity increased. Interestingly, selected compounds 1 to 3, mostly hydrazides (compounds 2), were effective in killing M. tuberculosis growing within macrophages at concentrations in culture medium which were much lower than the corresponding MICs. These compounds also displayed good activity against drug-resistant M. tuberculosis strains.

A macrophage invasion mechanism for mycobacteria implicating the extracellular domain of CD43

We studied the role of CD43 (leukosialin/sialophorin), the negatively charged sialoglycoprotein of leukocytes, in the binding of mycobacteria to host cells. CD43-transfected HeLa cells bound Mycobacterium avium, but not Salmonella typhimurium or Shigella flexneri. Quantitative bacteriology showed that macrophages (M(phi)) from wild-type mice (CD43(+/+)) bound M. avium, Mycobacterium bovis (bacillus Calmette-Guérin), and Mycobacterium tuberculosis (strain H37Rv), whereas M(phi) from CD43 knockout mice (CD43(-/)-) did not. Fluorescence microscopy demonstrated that the associated M. avium had been ingested by the CD43(+/+) M(phi). The inability of CD43(-/)- M(phi) to bind M. avium could be restored by addition of galactoglycoprotein (Galgp), the extracellular mucin portion of CD43. The effect of Galgp is not due to opsonization of the bacteria, but required its interaction with the M(phi) other mucins had no effect. CD43 expression by the M(phi) was also required for optimal induction by M. avium of tumor necrosis factor (TNF)-alpha production, which likewise could be reconstituted by Galgp. In contrast, interleukin (IL)-10 production by M. avium-infected M(phi) was CD43 independent, demonstrating discordant regulation of TNF-alpha and IL-10. These findings describe a novel role of CD43 in promoting stable interaction of mycobacteria with receptors on the M(phi) enabling the cells to respond specifically with TNF-alpha production.

Lepromatous leprosy in an HIV-positive patient in Spain

We report a 35-year-old HIV-positive male affected by lepromatous leprosy which, to our knowledge, is the first case of its kind in Spain. The relationship between the two conditions is discussed.

Protection against virulent Mycobacterium avium infection following DNA vaccination with the 35-kilodalton antigen is accompanied by induction of gamma interferon-secreting CD4(+) T cells

Mycobacterium avium is an opportunistic pathogen that primarily infects immunocompromised individuals, although the frequency of M. avium infection is also increasing in the immunocompetent population. The antigen repertoire of M. avium varies from that of Mycobacterium tuberculosis, with the immunodominant 35-kDa protein being present in M. avium and Mycobacterium leprae but not in members of the M. tuberculosis complex. Here we show that a DNA vector encoding this M. avium 35-kDa antigen (DNA-35) induces protective immunity against virulent M. avium infection, and this protective effect persists over 14 weeks of infection. In C57BL/6 mice, DNA vaccines expressing the 35-kDa protein as a cytoplasmic or secreted protein, both induced strong T-cell gamma interferon (IFN-gamma) and humoral immune responses. Furthermore, the antibody response was to conformational determinants, confirming that the vector-encoded protein had adopted the native conformation. DNA-35 immunization resulted in an increased activated/memory CD4(+) T-cell response, with an accumulation of CD4(+) CD44(hi) CD45RB(lo) T cells and an increase in antigen-specific IFN-gamma production. The protective effect of the DNA-35 vectors against M. avium infection was comparable to that of vaccination with Mycobacterium bovis BCG and significantly greater than that for previous treated infection with M. avium. These results illustrate the importance of the 35-kDa protein in the protective response to M. avium infection and indicate that DNA vaccination successfully promotes a sustained level of protection during chronic M. avium infection.

Familial cluster of cutaneous Mycobacterium avium infection resulting from use of a circulating, constantly heated bath water system

We describe familial cases of cutaneous infection caused by Mycobacterium avium. A 45-year-old father, his 14-year-old son and 11-year-old daughter, among five persons in a family, presented with a 2-month history of inflammatory subcutaneous nodules and ulcerations. Histology of skin biopsy specimens showed granulomatous inflammation, and mycobacterial colonies isolated from the skin of each patient were identified as M. avium by DNA hybridization analysis. The patients were all treated successfully with combined drug therapy consisting of rifampicin, isoniazid and clarithromycin. Their lesions were purely cutaneous M. avium infection, without any visceral involvement. Neither systemic disease nor immunological impairment was detected in the family. However, they all used a circulating, constantly heated bath water system. The bath water was continuously heated to about 40 degrees C without changing the water for a few months, and M. avium was isolated from the filter of the bath tub heating unit. It is considered that this unusual familial cluster of cutaneous M. avium infection in healthy persons may have resulted from the use of contaminated bath water.

Molecular epidemiologic evaluation of transmissibility and virulence of Mycobacterium tuberculosis

Discovery of genotypic markers associated with increased transmissibility in Mycobacterium tuberculosis would represent an important step in advancing mycobacterial virulence studies. M. tuberculosis strains may be classified into one of three genotypes on the basis of the presence of specific nucleotide substitutions in codon 463 of the katG gene (katG-463) and codon 95 of the gyrA gene (gyrA-95). It has previously been reported that two of these three genotypes are associated with increased IS6110-based clustering, a potential proxy of virulence. We designed a case-control analysis of U.S.-born patients with tuberculosis in San Francisco, Calif., between 1991 and 1997 to investigate associations between katG-463 and gyrA-95 genotypes and epidemiologically determined measures of strain-specific infectivity and pathogenicity and IS6110-based clustering status. We used a new class of molecular probes called molecular beacons to genotype the isolates rapidly. Infectivity was defined as the propensity of isolates to cause tuberculin skin test conversions among named contacts, and pathogenicity was defined as their propensity to cause active disease among named contacts. The molecular beacon assay was a simple and reproducible method for the detection of known single nucleotide polymorphisms in large numbers of clinical M. tuberculosis isolates. The results showed that no genotype of the katG-463- and gyrA-95-based classification system was associated with increased infectivity and pathogenicity or with increased IS6110-based clustering in San Francisco during the study period. We speculate that molecular epidemiologic studies investigating clinically relevant outcomes may contribute to the knowledge of the significance of laboratory-derived virulence factors in the propagation of tuberculosis in human communities.

Reactivation of tuberculosis is associated with a shift from type 1 to type 2 cytokines

The pattern of cytokines produced by T cells from mice with latent tuberculosis and during reactivation of tuberculosis was determined. A type 1 cytokine pattern was observed in T cells isolated from the lung of mice with latent disease. Reactivation of mycobacterial growth, by activation of the hypothalamic-pituitary-adrenal (HPA) axis, resulted in a shift from a type 1 to a type 2 cytokine pattern in both CD4 and CD8 T cells. Classification of the T cells based on their differential expression of CD45 and CD44 showed that the phenotypically different populations of CD4 and CD8 cells exhibited a type 1 cytokine pattern at latency and that reactivation of latent tuberculosis was associated with a shift in cytokines produced by these populations to a type 2 cytokine response. Control of mycobacterial growth resulted in a return to the type 1 cytokine pattern found during latent disease.

Mycobacterial infections in lung transplant recipients

BACKGROUND

Immunosuppression and chronic lung disease are known risk factors for mycobacterial infection and might be expected to develop with an increased frequency in lung transplant recipients. We therefore sought to document the incidence and type of mycobacterial infections in a large lung transplant program.

METHODS

A retrospective review of 219 transplant procedures (60 single lung transplants and 159 double lung transplants) in 210 patients was conducted. All patients had scheduled surveillance bronchoscopies at 3, 6, 9, 12, 18, and 24 months, and yearly thereafter. BAL samples were processed routinely for mycobacterium.

RESULTS

Eight patients (3.8%) had evidence of infection (5 men, 3 women; age range, 26 to 63 years). The reasons for transplant were obstructive lung disease (six), cystic fibrosis (one), and pulmonary fibrosis (one). Five recipients had infection in their native lungs; two of five cultured mycobacterium from BAL following transplantation. At least four of five patients had nontuberculous mycobacterium (one showed acid fast bacilli and granuloma on a biopsy specimen that was not sent for culture). None of the five developed disease (mean follow-up = 22 months; range, 3 to 30 months). The organisms were Mycobacterium avium complex (three), Mycobacterium xenopi (one), and unidentified (one). Of the three remaining patients who developed infection after transplantation, one grew Mycobacterium chelonae and the others grew Mycobacterium tuberculosis (both received double lung transplants and had no evidence of mycobacterium in their native lungs). The only definite symptomatic disease occurred in the patients with M tuberculosis, one of whom had evidence of dissemination. The patients with M tuberculosis responded to standard treatment. There have been no deaths due to mycobacterium.

CONCLUSION

Mycobacterial disease rarely occurs following lung transplantation. Cultures for mycobacterium in surveillance BALs in the absence of symptoms are likely unnecessary.

Bactericidal activities of the pyrrole derivative BM212 against multidrug-resistant and intramacrophagic Mycobacterium tuberculosis strains

The pyrrole derivative BM212 [1, 5-diaryl-2-methyl-3-(4-methylpiperazin-1-yl)methyl-pyrrole] was shown to possess strong inhibitory activity against both Mycobacterium tuberculosis and some nontuberculosis mycobacteria. BM212 was inhibitory to drug-resistant mycobacteria and also exerted bactericidal activity against intracellular bacilli residing in the U937 human histiocytic lymphoma cell line.

Pyrrolnitrin and related pyrroles endowed with antibacterial activities against Mycobacterium tuberculosis

During development of nitroheterocycles with potential antimycobacterial activities we have tested against Mycobacterium tuberculosis a number of pyrroles strictly related to pyrrolnitrin, an antifungal antibiotic isolated from Streptomyces pyrrocinia. Some of the tested arylpyrrole derivatives and pyrrolnitrin have shown appreciable inhibiting activity against M. tuberculosis and M. avium. SAR studies well correlate antimycobacterial potency with the presence of halogens in the phenyl ring and a nitro group at position 3 of pyrrole.

Host resistance to mycobacteria is compromised by activation of the hypothalamic-pituitary-adrenal axis

Host resistance to the growth of Mycobacterium avium and Mycobacterium tuberculosis is controlled by a gene, termed Nramp1, that maps to chromosome 1 in mice. Activation of the HPA axis or treatment of macrophages from susceptible mice with corticosterone suppresses the expression of Nramp1 mRNA and results in an increased susceptibility to mycobacterial growth. In contrast, neither activation of the HPA axis nor treatment of macrophages from resistant mice with corticosterone results in an alteration in their resistance or suppression of Nramp1 expression. Investigation into the mechanism of the differential response of the macrophages to corticosterone indicated that differences were associated with the stability of the mRNA in macrophages from BCG-resistant mice. Thus, corticosterone induced the accelerated degradation of Nramp1 mRNA as well as mRNA of several other macrophage activation genes in macrophages from BCG-susceptible mice. Treatment of macrophages with corticosterone before the induction of Nramp1 resulted in the accelerated degradation of mRNA in macrophages from both resistant and susceptible mice. The Nramp1 gene product appears to protect the mRNA of macrophage activation genes from degradation induced by corticosterone by an iron-dependent mechanism.

Phenotypic changes in T cell populations during the reactivation of tuberculosis in mice

The phenotypic changes of T lymphocytes during the reactivation of latent Mycobacterium tuberculosis infection by activation of the hypothalamic-pituitary-adrenal (HPA) axis was monitored using flow cytometric analysis. Subsets of CD4+ and CD8+ lymphocyte populations from the lung, spleen and draining lymph nodes of infected mice were identified based on their differential expression of the cell surface antigens CD44 and CD45RB. Latent infection was characterized by an accumulation of both naive, activated and memory CD4 and CD8 T lymphocytes in the lung and mediastinal lymph nodes. No changes were observed in the spleen of mice with latent infection when compared with uninfected mice. Immediately following the activation of the HPA axis, a reduction in all CD4+ and CD8+ T cells in the lung and mediastinal lymph nodes was observed. This correlated with the reactivation of mycobacterial growth. The decrease was transient for memory and naive CD4 and CD8 T lymphocyte populations in the lung. However, the number of naive CD4 and CD8 T lymphocyte populations in the mediastinal lymph node following reactivation was less than that found in mice with latent infection. These data provide the first characterization of T lymphocyte populations which may be functionally involved in the immunological response to HPA axis-induced reactivation of M. tuberculosis infection.

Immunological relatedness of the protective mechanisms against tuberculosis and cancer

BACKGROUND

Bacille Calmette-Guérin (BCG), an attenuated strain of tuberculous bacillus, is the source of vaccines providing unclear and variable protection against tuberculosis (TB) and cancer. Thermostable macromolecular antigens (TMAs) are major mycobacterial complexes immunodominant in disease. A60 (TMA complex of BCG) protects mice against TB development, via T lymphocyte (TL)-mediated macrophage (Mphi) activation, halting intracellular mycobacterial replication. In most A60-primed mice, cytolytic TLs and Mphi infiltrate cancer tissue, resulting in 80-100% rejection. Adoptive TL transfer is indispensable for Mphi-dependent tumour cell inactivation via oxygen and nitrogen radicals. Neoplasm development induces immune anergy with depletion ofA60-specific TL and activated Mphi. A60 protects mice against TB and cancer by inducing the synthesis of three lymphokines: interleukin 2 (IL-2), interferon gamma (IFN-gamma) and tumour necrosis factor alpha (TNF-alpha). Tumour cells prevent A60-dependent synthesis of these lymphokines in vivo and in vitro.

CONCLUSION

These data provide some clues to immune surveillance and tumour escape mechanisms, as well as to the antituberculous and antineoplastic BCG action.

Conditionally replicating luciferase reporter phages: improved sensitivity for rapid detection and assessment of drug susceptibility of Mycobacterium tuberculosis

TM4 is a lytic mycobacteriophage which infects mycobacteria of clinical importance. A luciferase reporter phage, phAE40, has been constructed from TM4 and was previously shown to be useful for the rapid detection and drug susceptibility testing of Mycobacterium tuberculosis. However, the lytic nature of the phage results in a loss of detectable light output and limits the sensitivity of detection. We describe several strategies aimed at improving the luciferase activity generated by TM4 luciferase phages, including (i) varying the position of the luciferase gene in the phage genome, (ii) isolating host-range mutants of the phage, and (iii) introducing temperature-sensitive mutations in the phage such that it will not replicate at the infecting temperature. Several new phages generated by these methods show increased intensity of luciferase production compared to the first-generation reporter phage phAE40, and one phage, phAE88, also demonstrates an enhanced duration of luciferase activity. This has allowed the detection of as few as 120 BCG cells and the determination of drug susceptibilities of M. tuberculosis in as little as 1 day.

Recombinant Mycobacterium aurum expressing Escherichia coli beta-galactosidase in high throughput screening of antituberculosis drugs

Mycobacterium aurum is considered a surrogate of M. tuberculosis and recently has been proposed as test organism in high throughput screening of antituberculosis drugs (3). In this investigation, we suggest use of a recombinant M. aurum expressing E. coli lacZ gene, in which beta-galactosidase production is the reporter system as recently reported by us (6). The assay is based on production of beta-galactosidase in presence of drugs during growth. Enzyme production was inhibited within 4 h by frontline antimycobacterial drugs like streptomycin, rifampicin, isoniazid, ethambutol, ofloxacin, and sparfloxacin at their MICs. The assay could be performed conveniently in 96-well microtiter plate format.

Analysis of the genes encoding the antigen 85 complex and MPT51 from Mycobacterium avium

The components of the fibronectin-binding antigen 85 complex (85A, 85B, and 85C) and the related protein MPB/MPT51 are major secreted proteins in Mycobacterium tuberculosis and Mycobacterium bovis BCG. The fbpA, fbpC, and mpt51 genes encoding 85A, 85C, and MPT51, respectively, were isolated from Mycobacterium avium and sequenced in this study. The structures of these genes, and that of the fbpB gene encoding the 85B protein, were conserved in these three species. The secreted amounts of 85A, 85B, 85C, and MPB/MPT51 were compared for M. tuberculosis, BCG, and M. avium. These four proteins were found in large amounts in the culture filtrates from M. tuberculosis and BCG. In contrast, in the culture filtrate from M. avium, 85B and MPT51 were abundant whereas 85A and 85C were hardly found, in spite of the presence of the encoding genes. The difference in the secretion amounts might be regulated at the transcription level. These facts might reflect host immunopathogenesis, the protective immunities against infections, and the drug susceptibilities of these organisms.