A new gene, sigG, encoding a putative alternative sigma factor of Streptomyces coelicolor A3(2)

An oligonucleotide probe encoding a peptide motif conserved in all sigma factors was used to isolate a new gene, sigG, from a Streptomyces coelicolor A3(2) genomic library. The deduced protein of 263 amino acids with an M(r) of 29,422 showed the greatest similarity to the previously identified sporulation sigma factor (sigma F) of Streptomyces coelicolor, and general stress response sigma factor (sigma B) of Bacillus subtilis, mostly in domains suggested to be involved in recognition of -10 and -35 promoter regions. Southern-blot hybridization with DNA from several Streptomyces spp. revealed the presence of a similar gene in all strains tested. Disruption of the S. coelicolor sigG gene appeared to have no obvious effect on growth, morphology, differentiation, and production of pigmented antibiotic actinorhodin and undecylprodigiosin.     

Inactivation of σE and σG in Clostridium acetobutylicum illuminates their roles in clostridial-cell-form biogenesis, granulose synthesis, solventogenesis, and spore morphogenesis

Central to all clostridia is the orchestration of endospore formation (i.e., sporulation) and, specifically, the roles of differentiation-associated sigma factors. Moreover, there is considerable applied interest in understanding the roles of these sigma factors in other stationary-phase phenomena, such as solvent production (i.e., solventogenesis). Here we separately inactivated by gene disruption the major sporulation-specific sigma factors, σ(E) and σ(G), and performed an initial analysis to elucidate their roles in sporulation-related morphogenesis and solventogenesis in Clostridium acetobutylicum. The terminal differentiation phenotype for the sigE inactivation mutant stalled in sporulation prior to asymmetric septum formation, appeared vegetative-like often with an accumulation of DNA at both poles, frequently exhibited two longitudinal internal membranes, and did not synthesize granulose. The sigE inactivation mutant did produce the characteristic solvents (i.e., butanol and acetone), but the extent of solventogenesis was dependent on the physiological state of the inoculum. The sigG inactivation mutant stalled in sporulation during endospore maturation, exhibiting engulfment and partial cortex and spore coat formation. Lastly, the sigG inactivation mutant did produce granulose and exhibited wild-type-like solventogenesis.     

结核分枝杆菌潜伏感染诊断方法的新进展

每年有超过8百万人感染结核,其中绝大部分没有发展为活动性结核病,而是表现为潜伏性结核感染。大多数活动性结核病是潜伏感染的结核杆菌重新被激活所致,因此结核潜伏感染者成为结核患者的重要来源。及早诊断和治疗结核潜伏感染者是控制结核传播的最有效手段之一。我们较要综述了目前国内外结核潜伏感染的诊断方法及其新进展。     

Tuberculosis; recent trends in infection,disease and deaths in California

Although fewer patients with tuberculosis are reported in a far advanced stage of the disease than ever before, the proportion of persons dying of tuberculosis whose disease had not previously been diagnosed appears to be increasing. The average length of sanatorium treatment, and the intramural case fatality rates have not shown much decrease. Tuberculosis mortality rates fall during economic depressions and rise with business booms. Epidemics of influenza do not always increase tuberculosis death rates. Common claims to the contrary are not sustained by recent California data.     

TUBERCULOSIS—Recent Trends in Infection,Disease and Deaths in California

Although fewer patients with tuberculosis are reported in a far advanced stage of the disease than ever before, the proportion of persons dying of tuberculosis whose disease had not previously been diagnosed appears to be increasing. The average length of sanatorium treatment, and the intramural case fatality rates have not shown much decrease. Tuberculosis mortality rates fall during economic depressions and rise with business booms. Epidemics of influenza do not always increase tuberculosis death rates. Common claims to the contrary are not sustained by recent California data.     

Risk factors for reactivation of tuberculosis in Manitoba

Although rates of reported cases of active tuberculosis have been declining in Manitoba and throughout Canada over the past two decades, the percentage of active cases due to reactivated tuberculosis has remained relatively constant. From 1976 to 1981, 113 cases of reactivated tuberculosis were listed in the Manitoba tuberculosis registry. We found that 36 cases did not meet our criteria for reactivation, primarily because there was no 6-month period of inactivity; another 5 cases could not be verified. In more than half of the remaining 72 the initial episode had occurred before 1960. We also randomly selected from the registry as controls 118 age- and sex-matched cases of nonreactivated tuberculosis. We found that registered Indian status was significantly associated with risk of reactivation, especially when the initial disease had been extensive. Awareness of high-risk groups, earlier diagnosis and adequate treatment are needed to prevent reactivated tuberculosis.     

Incidence of active tuberculosis in the native population of Canada.

We analysed the incidence rates of active tuberculosis reported between 1970 and 1981 in three groups of people born in Canada: Inuit, registered Indians and others (mainly of European origin). While the rates of tuberculosis were quite low in the last group, which constitutes about 82% of the population of Canada, they were 16 times higher among Indians and 24 times higher among Inuit. Some 20 to 30 years ago the Inuit had the highest recorded rate of tuberculosis in the world; with an intensive program the rate decreased sharply. Such a program has not been implemented among the Indian population, and the incidence rate has not decreased as rapidly. A major effort is required to satisfactorily control tuberculosis among Indians. In addition, we must not allow our efforts to slacken in the control of tuberculosis among the Inuit.     

Cloning of the gene encoding a protective Mycobacterium tuberculosis secreted protein detected in vivo during the initial phases of the infectious process

The existence of therapeutic agents and the bacille Calmette-Guérin (BCG) vaccine have not significantly affected the current tuberculosis pandemic. BCG vaccine protects against serious pediatric forms of tuberculosis but not against adult pulmonary tuberculosis, the most common and contagious form of the disease. Several vaccine candidates, including Mycobacterium tuberculosis recombinant proteins formulated in newer adjuvants or delivered in bacterial plasmid DNA have recently been described. An attractive source of vaccine candidates has been M. tuberculosis Ags present in culture supernatants of the initial phases of the bacterial growth in vitro. In this study we describe an Ag discovery approach to select for such Ags produced in vivo during the initial phases of the infection. We combined RP-HPLC and mass spectrometry to identify secreted or shed M. tuberculosis proteins eliminated in animal urine within 14 days after the infection. A peptide containing sequence homology with a hypothetical M. tuberculosis protein was identified and the recombinant protein produced in Escherichia coli. The protein was recognized by Ab (IgG2a and IgG1) and T cells (Th1) of mice infected with M. tuberculosis and by lymphoid cells from healthy donors who had a positive purified protein derivative skin test but not from tuberculosis patients. Moreover, this Ag induced protection in mice against M. tuberculosis at levels comparable to protection induced by BCG vaccine. These results validate the Ag discovery approach of M. tuberculosis proteins secreted or shed in vivo during the early phases of the infection and open new possibilities for the development of potential vaccine candidates or of markers of active mycobacterial multiplication and therefore active disease.     

Diagnosing tuberculosis in pregnancy: a case report

A case of miliary tuberculosis complicated by deciduitis and sub-chorionitis in a pregnant woman manifesting also influenza A/H1N1v infection and urinary tract infection is reported. Diagnosis of tuberculosis was obtained before delivery by examining amniotic fluid for Mycobacterium tuberculosis. Even though maternal symptoms did not suggest TB, diagnosis was early enough to start effective treatment in both the mother and the neonate and prevent in-hospital M.tuberculosis diffusion. A high index of suspicion by health professionals is required to detect and manage tuberculosis in pregnancy and newborns in both the developed and developing word.     

Circulating interleukin-18 and osteopontin are useful to evaluate disease activity in patients with tuberculosis

BACKGROUND: T helper type 1 (Th1) responses have been implicated in the protective immunity, pathophysiology and development of tuberculosis. However, it is still unclear which molecule(s) reflect disease activity in patients with tuberculosis. METHODS: By specific enzyme immunoassays, circulating interferon-gamma. (IFN-gamma), interleukin-12 (IL-12), IL-18 and osteopontin (OPN) were measured in 47 patients with pulmonary tuberculosis and 7 patients with miliary tuberculosis before anti-tuberculosis therapy, and also measured in 19 patients with tuberculosis before and after anti-tuberculosis therapy. RESULTS: Circulating IFN-gamma, IL-18 and OPN levels were significantly higher in patients with pulmonary tuberculosis than in healthy controls, while there was no significant difference in levels of circulating IL-12 between tuberculosis patients and controls. Circulating IFN-gamma, IL-12, IL-18 and OPN paralleled the extent of lung lesions, and circulating IFN-gamma, IL-18 and OPN paralleled the magnitude of fever in patients with pulmonary tuberculosis. Patients with miliary tuberculosis had extremely high levels of circulating OPN, IFN-gamma and IL-18. Circulating IL-18 and OPN were significantly decreased with anti-tuberculosis therapy, whereas circulating IL-12 and IFN-gamma were not. CONCLUSIONS: Among Th1 response associated molecules, circulating levels of IL-18 and OPN, but not IFN-gamma or IL-12, reflect disease activity in patients with tuberculosis.     

CD4+ T cells mediate IFN-gamma-independent control of Mycobacterium tuberculosis infection both in vitro and in vivo

Although IFN-gamma is necessary for survival of Mycobacterium tuberculosis infection in people and animal models, it may not be sufficient to clear the infection, and IFN-gamma is not a reliable correlate of protection. To determine whether IFN-gamma-independent mechanisms of immunity exist, we developed a murine ex vivo culture system that directly evaluates the ability of splenic or lung lymphocytes to control the growth of M. tuberculosis within infected macrophages, and that models in vivo immunity to tuberculosis. Surprisingly, CD4(+) T cells controlled >90% of intracellular M. tuberculosis growth in the complete absence of IFN-gamma stimulation of macrophages, via a NO-dependent mechanism. Furthermore, bacillus Calmette-Guerin-vaccinated IFN-gamma-deficient mice exhibited significant protection against M. tuberculosis challenge that was lost upon depletion of CD4(+) T cells. These findings demonstrate that CD4(+) T cells possess IFN-gamma-independent mechanisms that can limit the growth of an intracellular pathogen and are dominant in secondary responses to M. tuberculosis.     

Nude rat (F344/N-rnu) tuberculosis

As many mononuclear cells from Mycobacterium tuberculosis-infected lung tissues are not available for fluorescence-activated cell sorter (FACS) analysis and the tuberculin test is not feasible in a mouse tuberculosis model, we attempted to develop a rat tuberculosis model. We have previously reported that rat tuberculosis is associated with granulomas that lack central necrosis. In order to develop a better animal model of tuberculosis in immunocompromised humans (tuberculosis associated with HIV infection or tuberculosis of the elderly), we infected F344/N-rnu nude rats with M. tuberculosis via the airborne route. The animals developed pulmonary granulomas with central necrosis encapsulated by dense collagen fibres, closely resembling those of human tuberculosis. The nude rats died of disseminated tuberculosis by the 85th day after aerosol infection, while F344 wild-type rats did not. Interestingly, T-cells that were reactive with anti-CD4 antibody and anti-CD8 antibody, indicating the presence of remnant thymus, were observed in the infected lung tissues of the nude rats. Therefore, T-cell precursors may be present in nude rats. The nude rat tuberculosis model mimics tuberculosis in immunocompromised humans and may provide a suitable model for immunological studies in vivo.