TUBERCULOSIS IN CHILDHOOD

Those physicians who deal with children have much to contribute toward case finding in tuberculosis among these patients as well as adults. The tuberculin test is the most accurate weapon at hand. Contacts other than the parents should be looked for. Symptoms, beside fever, to be noted are eye and skin complaints. In the physical examination the chest is relatively unimportant as compared to the eye, the skin, the lymphatic and skeletal systems. In the roentgenographic examination, epituberculosis and atelectasis should be differentiated. When stomach washings are necessary for the diagnosis, the tuberculin test on the guinea-pig should not be forgotten. Careful laboratory studies will clear up roentgenographic confusion.In the treatment, removal of contact is essential, and often all that is necessary, but other factors should be considered. Of the more common complications, atelectasis, bronchiectasis, and cavitation or reinfection, may be treated surgically with all the accepted methods except thoracoplasty. Heliotherapy should not be forgotten in bone and joint tuberculosis. It is to be hoped that BCG will prove efficacious in vaccination, but published reports are not scientifically convincing. It destroys the value of the tuberculin test where used, and it should never be substituted for removal of contact as a prophylactic measure.     

Preventive treatment of tuberculin-negative contacts

Five children who had been in close contact with highly infectious tuberculous individuals presented recently to the tuberculosis service of The Montreal Children''s Hospital. Four had developed serious pulmonary tuberculosis and one tuberculous meningitis, all within the three months which followed a post-contact negative tuberculin test.The management of tuberculin-negative children recently exposed to active infectious tuberculosis by repeated skin tests and chest radiography alone is inadequate for their protection. These children are at high risk of developing disease by the time their tuberculin sensitivity has become evident. It is inadvisable to vaccinate them with BCG until three months after their last exposure to the disease. A plea is made for preventive chemotherapy in these cases.     

Ocular Histoplasmosis

Case reports of three residents of Ontario with clinical histoplasmic chorioretinitis are presented. The diagnosis was made on the basis of the clinical appearance, the presence of calcified lesions in the chest, a negative skin test to tuberculin, and a positive skin test to toxoplasmin. All patients were treated with intravenous amphotericin B. Except for transitory elevation of blood urea nitrogen, there were no serious complications from the drug and in all cases the lesions in the eyes were improved. Histologic or cultural proof of the presence of fungus in the eye is not available, but clinical and laboratory findings can combine to point to the diagnosis of histoplasmosis. In such cases, since vision is at stake, treatment with amphotericin B should be considered.     

Value of combining the erythrocyte sedimentation rate test with tuberculin testing in the control of tuberculosis in baboons.

2 batches of baboon infected with tuberculosis were subjected to serial tests with human and bovine tuberculin, while erythrocyte sedimentation rates were estimated concurrently. In the very early stages most but not all reacted to human tuberculin while fewer responded to bovine material. After further development of the disease, tuberculin tests remained positive while sedimentation rates were raised by 10-30 mm per hour. By the time early spread had occurred response to tuberculin was absent but sedimentation rates tended to increase. Advanced cases always tuberculin negative but sedimentation rates were in excess of 50 mm per hour. Such animals were always in good physical condition and represented an insidious danger to other animals and staff in contact with them. Clinical examination failed to reveal cases of tuberculosis except in the terminal stages and no cases were diagnosed by radiography. 2 animals died from apparent anaphylaxis following inoculation of both types of tuberculin. Results showed that use of one or other of these tests alone would not have made possible the elimination of infection.     

New approaches to tuberculosis surveillance in nonhuman primates

Despite significant progress in reducing the incidence of tuberculosis in nonhuman primates (NHPs) maintained in captivity, outbreaks continue to occur in established colonies, with potential serious consequences in human exposures, animal losses, disruption of research, and costs related to disease control efforts. The intradermal tuberculin skin test (TST) using mammalian old tuberculin (MOT) has been the mainstay of NHP tuberculosis surveillance and antemortem diagnosis for more than 60 years. But limitations of the TST, particularly its inability to reliably identify animals with latent TB infections, make it unsuitable for use as a single, standalone test for TB surveillance in nonhuman primates in the 21st century. Advances in technology and the availability of Mycobacterium spp. genomic sequence data have facilitated the development and evaluation of new immune-based screening assays as possible adjuncts and alternatives to the TST, including in vitro whole blood assays that measure the release of interferon gamma in response to stimulation with tuberculin or specific mycobacterial antigens, and assays that detect antibodies to highly immunogenic secreted proteins unique to M. tuberculosis, M. bovis, and other species belonging to the M. tuberculosis complex. It is becoming apparent that no single screening test will meet all the requirements for surveillance and diagnosis of tuberculosis in nonhuman primates. Instead, the use of several tests in combination can increase the overall sensitivity and specificity of screening and surveillance programs and likely represents the future of TB testing in nonhuman primates. In this article we describe the characteristics of these newer screening tests and discuss their potential contributions to NHP tuberculosis surveillance programs.     

Modern management of tuberculosis; the public health implications of recent advances

Modern treatment for tuberculosis has greatly increased the problem of preventing spread of infection. BCG vaccination, for instance, would cause all persons to react to tuberculin test so that the possibility of tuberculosis could never be ruled out by this means. Streptomycin and more recently developed drugs may sterilize sputum so that diagnosis cannot be confirmed for some time after use of such drugs; when by use of these drugs the disease had been confined to caseous encapsulations, later breakdown of the encapsulations may release strains of bacilli resistant to the drugs both in the patient and in others infected with them. The temporary sterilization of sputum, coupled with the euphoria resulting in part from abrupt remission of the toxic state, may lead to premature discharge of patients from sanatoria and further spread of tuberculosis. Both the public and the profession must be impressed with these facts.For more profitable than minifilm surveys of normal populations are routine x-ray examination of all patients admitted to hospitals (by which two to five times as many cases have been found) and follow-up of persons who have had contact with tuberculosis patients (thirteen times as many cases found).A study being conducted by the California Tuberculosis and Health Association indicates that in many counties neither the number of x-rays made in public surveys nor the number of cases found is known or even to be estimated from existing records. Because of reduction in deaths due to tuberculosis some public officials are reluctant to spend for further treatment facilities. As the actual number of cases is increasing in many areas, however, expenditures will have to be increased.     

MODERN MANAGEMENT OF TUBERCULOSIS—The Public Health Implications of Recent Advances

Modern treatment for tuberculosis has greatly increased the problem of preventing spread of infection. BCG vaccination, for instance, would cause all persons to react to tuberculin test so that the possibility of tuberculosis could never be ruled out by this means. Streptomycin and more recently developed drugs may sterilize sputum so that diagnosis cannot be confirmed for some time after use of such drugs; when by use of these drugs the disease had been confined to caseous encapsulations, later breakdown of the encapsulations may release strains of bacilli resistant to the drugs both in the patient and in others infected with them. The temporary sterilization of sputum, coupled with the euphoria resulting in part from abrupt remission of the toxic state, may lead to premature discharge of patients from sanatoria and further spread of tuberculosis. Both the public and the profession must be impressed with these facts.For more profitable than minifilm surveys of normal populations are routine x-ray examination of all patients admitted to hospitals (by which two to five times as many cases have been found) and follow-up of persons who have had contact with tuberculosis patients (thirteen times as many cases found).A study being conducted by the California Tuberculosis and Health Association indicates that in many counties neither the number of x-rays made in public surveys nor the number of cases found is known or even to be estimated from existing records.Because of reduction in deaths due to tuberculosis some public officials are reluctant to spend for further treatment facilities. As the actual number of cases is increasing in many areas, however, expenditures will have to be increased.     

Prevalence of Mycobacterium tuberculosis infection among injection drug users in Toronto

BACKGROUND: Injection drug users are at increased risk of Mycobacterium tuberculosis infection and active tuberculosis (TB). The primary objective of this study was to determine the prevalence of M. tuberculosis infection among injection drug users in Toronto, as indicated by a positive tuberculin skin test result. An additional objective was to identify predictors of a positive skin test result in this population. METHODS: A cross-sectional study was carried out involving self-selected injection drug users in the city of Toronto. A total of 171 participants were recruited through a downtown Toronto needle-exchange program from June 1 to Oct. 31, 1996. RESULTS: Of 167 subjects tested, 155 (92.8%) returned for interpretation of their skin test result within the designated timeframe (48 to 72 hours). Using a 5-mm cut-off, the prevalence rate of positive tuberculin skin test results was 31.0% (95% confidence interval 23.8% to 38.9%). Birth outside of Canada and increasing age were both predictive of a positive result. INTERPRETATION: There is a high burden of M. tuberculosis infection in this population of injection drug users. The compliance observed with returning for interpretation of skin test results indicates that successful TB screening is possible among injection drug users.     

Causes of para-allergy to tuberculin

Experiments on 56 rabbits infected with microorganisms of the genera Mycobacterium, Nocardia and Rhodococcus revealed that in response to the action of different antigens used T and B systems of immunity induced synthesis of antibodies reactive with nonspecific antigens (mycobacterial antigens, tuberculin). In some cases the statistically significant correlation between the dynamics of blast transformation and the specific lysis of lymphocytes in animals with Nocardia and Rhodococcus infections (in comparison with the controls) was determined when P.P.D. tuberculin was used as specific antigen. In the rabbits sera infected by Nocardia and Rhodococcus complement-fixation and hemagglutination antibodies to mycobacterial antigens were detected. These rabbits also exhibited skin reaction to P.P.D. tuberculin. The presence of common group-specific antigens in Nocardia and Rhodococcus, as well as in mycobacteria, determined the capacity of the former to sensitize experimental animals to tuberculin, with should be taken into consideration in making the allergic test to tuberculosis.     

Cost effectiveness of interferon-gamma release assay for tuberculosis contact screening in Japan

BACKGROUND: Nearly the entire population of Japan has been vaccinated with Bacillus Calmette-Guerin (BCG), which causes a false-positive result in the tuberculin skin test (TST). The interferon-gamma release assay QuantiFERON-TB Gold (QFT) is a new alternative to the TST that can be used to screen for latent tuberculosis infection and active tuberculosis, as it has no cross-reactivity with BCG. METHODS: We constructed a Markov model to evaluate the cost effectiveness of the QFT for tuberculosis contact screening. The target population is a hypothetical cohort of 1000 immunocompetent 20-year-old individuals who have had contact with sputum-smear-positive pulmonary tuberculosis patients. The analysis was conducted from a societal perspective over the lifetime of a contact. We compared the QFT-alone strategy with the TST followed by QFT (TST/QFT) strategy and the TST-alone strategy. RESULTS: In a base-case analysis, the QFT-alone strategy was dominant ($US 471.54; 28.1099 quality-adjusted life-years [QALYs]), compared with the TST/QFT strategy ($US 500.55; 28.1087 QALYs) and the TST-alone strategy ($US573.98; 28.1079 QALYs). The incremental cost-effectiveness ratio of the QFT-alone strategy was a cost saving of $US23 043.5/QALY gained compared with the TST/QFT strategy. On one-way sensitivity analysis, TST specificity and the prevalence of tuberculosis/latent tuberculosis infection affected the cost effectiveness. The probabilistic analysis showed that the QFT-alone strategy has a 95% chance of being cost effective at a threshold ratio of $US2.10/QALY gained, compared with the TST/QFT strategy. CONCLUSION: The QFT-alone strategy is the most cost effective for tuberculosis contact screening in Japan.     

The Spectrum of Extrapulmonary Tuberculosis

The incidence of new cases of extrapulmonary tuberculosis has remained constant, despite the decline in new cases of active pulmonary tuberculosis. This might be due to a delay in recognition, and particularly a lack of consideration of tuberculosis when the presenting symptoms are other than respiratory. Extrapulmonary tuberculosis should be considered in the differential diagnosis of bone, joint, genitourinary tract and central nervous system (CNS) diseases.To determine factors that might delay recognition and identification, 62 patients having extrapulmonary tuberculosis during 1969-1972 at the Los Angeles County-University of Southern California Medical Center were studied.Three quarters of these patients had had CNS, skeletal or genitourinary tuberculosis in equal distribution or 25 percent each. CNS involvement was seen frequently in the disseminated form. Presenting symptoms were protean and not specific, such as fever, anorexia, weight loss, cough, lymphadenopathy and neurologic abnormalities. Roentgenograms of the chest were abnormal in most. When a roentgenogram of the chest suggests pulmonary tuberculosis, signs and symptoms in other body systems should suggest extrapulmonary tuberculosis. If no abnormalities are seen on a roentgenogram of the chest, however, this does not preclude the diagnosis of extrapulmonary tuberculosis. Neither does a negative tuberculin skin test exclude the condition.Abnormal laboratory findings are common, especially in disseminated tuberculosis. These include various anemias, bone marrow disorders, hyponatremia due to inappropriate antidiuretic hormone syndrome. Analyses of pleural, peritoneal, pericardial and joint fluid usually show an exudate high in lymphocytes and occasionally low in glucose. Similar findings are seen in spinal fluid. The histological features of caseous or noncaseous granulomas are suggestive of but not specific for tuberculosis. Only culture of mycobacteria from sputum, urine, spinal fluid, pleural and other effusions and tissue biopsy specimens will yield a definitive diagnosis.Physicians must have a high index of suspicion to diagnose extrapulmonary tuberculosis, as it can resemble any disease in any organ system. Immediate therapy in the disseminated variety, sometimes even before a definite diagnosis can be made, may be lifesaving.     

Tuberculosis chemoprophylaxis.

The incidence of tuberculosis in the United States, after decreasing for many years, has recently begun to climb at an alarming rate. This rise is due mainly to excess cases in high-risk groups including human immunodeficiency virus-infected patients, the elderly, the foreign born, and the homeless. In the United States tuberculosis has been associated with a 10% mortality despite adequate treatment. The tuberculin skin test is a safe and inexpensive test for detecting tuberculous infection. To improve its predictive value the diagnostic criteria for classifying a positive reaction have recently been revised. High-risk populations should be screened to identify those persons who would most benefit from preventive treatment. Isoniazid therapy taken for 6 to 12 months is a safe and highly effective means of preventing tuberculous infection from developing into active disease. The most worrisome toxicity of isoniazid, fatal hepatitis, is extremely rare; when patients are monitored closely the incidence of death from hepatotoxicity is less than 0.01%.     

Tuberculosis in patients treated with tumor necrosis factor-alpha antagonists living in an endemic area. Is the risk worthwhile?

Tumor necrosis factor alpha antagonists (TNFA) are biological agents to treat chronic inflammatory and autoimmune diseases. However, their use is associated with an increased rate of tuberculosis, endemic mycoses, and intracellular bacterial infections. Since tuberculosis is moderately to highly endemic in Colombia, the risk of these infections in patients treated with TNFAs may be higher than previously reported in Colombia. Recently, four patients have developed tuberculosis during TNFA therapy. Tuberculosis appeared between 3 to 24 months after initiation of TFNA therapy and was independent of previous tuberculin skin test status. A review of the relevant literature and recommendations are presented as guides for surveillance and prophylaxis on a country-wide basis.     

Genetic Predisposition to Pass the Standard SICCT Test for Bovine Tuberculosis in British Cattle

Bovine tuberculosis (bTB) imposes an important financial burden on the British cattle industry, yet despite intense efforts to control its spread, incidence is currently rising. Surveillance for bTB is based on a skin test that measures an immunological response to tuberculin. Cattle that fail the test are classified as “reactors” and slaughtered. Recent studies have identified genetic markers associated with the reaction of cattle to the tuberculin test. At marker INRA111 a relatively common ‘22’ genotype occurs significantly more frequently in non-reactor cattle. Here we test the possibility that the putative protective ‘22’ genotype does not confer resistance but instead causes cattle that carry it to react less strongly to the prescribed test, and hence avoid slaughter, potentially even though they are infected. We show that, after controlling for age and breed, ‘22’ cattle react less strongly to the immunological challenge and may therefore be less likely to be classified as a reactor. These results highlight the potential discrepancy between infection and test status and imply that the effectiveness of the test-and-slaughter policy may be being compromised by selection for cattle that are genetically predisposed to react less strongly to tuberculin.     

Detection of early secretory antigenic target-6 antibody for diagnosis of tuberculosis in non-human primates

Tuberculosis is one of the most economically devastating, zoonotic infections of captive non-human primates. The limitations of the tuberculin skin test, which is currently used to diagnose tuberculosis in living non-human primates, make it necessary to find new, simple, and economical diagnostic methods. We describe use of an enzyme-linked immunoassay to detect IgG antibodies against early secretory antigenic target (ESAT)-6, a small protein secreted by virulent tubercle bacilli, in paired (pre- and post-outbreak) sera from 57 non-human primates involved in an outbreak of Mycobacterium bovis infection in a research colony. Of 25 animals with tuberculosis lesions at necropsy, 22 (88%) had high serum levels of the ESAT-6 antibody. The ESAT-6 antibody was found in 16% (5/32) of post-outbreak sera from animals in which tuberculosis could not be confirmed at necropsy. The strong association between the ESAT-6 antibody and tuberculosis in non-human primates documented in this study, together with the robustness of the serologic assay, make the ESAT-6 ELISA a valuable tool for diagnosis of tuberculosis in captive non-human primates.     

Expression and purification of recombinant antigens of Mycobacterium tuberculosis for application in serodiagnosis

Accurate diagnosis is essential for the treatment, prevention, and control of tuberculosis. Poor specificity of the tuberculin skin test in BCG-vaccinated populations and constraints to implementation of PCR and CMI-based diagnostic assays in developing countries warrant development of easy-to perform robust serological tests. Due to great heterogeneity in humoral response in TB patients, it will be necessary to include several antigens in any diagnostic assay to achieve useful levels of sensitivity and specificity. This needs production of recombinants, soluble versions of mycobacterial antigens in high yields. We have cloned, expressed, and purified a number of mycobacterial proteins in Escherichia coli. This paper describes the expression and purification of four promising sero-reactive proteins namely, ESAT6, CFP10, MTC28, and 14-kDa antigen of Mycobacterium tuberculosis. The protocol involves regulated and slow expression of proteins by using a T7 promoter-based expression vector for obtaining soluble protein followed by a three-step column chromatography procedure employing media with high binding capacity and flow characteristics. The yields of these proteins obtained were several folds higher than previously reported. The purified proteins were useful in detecting antibodies in sera of TB patients (smear positive, smear negative, and extra-pulmonary categories) and in combination with other immunodominant antigens will be useful in increasing the sensitivity to detect M. tuberculosis specific antibodies.     

Tuberculosis (Mycobacterium tuberculosis) in a pregnant baboon (Papio cynocephalus)

BACKGROUND: Old World monkeys are considered more susceptible to tuberculosis (TB) than New World monkeys. Several cases of TB in baboons are described in the literature. The data regarding baboon reaction to the tuberculin skin test (TST) are controversial. Some authors described anergy in this species, while the others documented a positive reaction. CASE REPORT: An 8-year-old clinically healthy pregnant female baboon (Papio cynocephalus anubis) developed positive TST after 3 years of negative tests in captivity while not pregnant. Thoracic radiographs demonstrated three nodular densities in the lung. RESULTS: Histological examination of tracheobronchial lymph nodes revealed multiple coalescing pyogranulomas filled with caseonecrotic debris and mineralized foci with numerous large foreign body-type and Langhans-type multinucleated giant cells. The bacterial culture contained a slow growing Mycobacterium tuberculosis complex. CONCLUSIONS: We describe, to the best of our knowledge, the first case of a positive TST in a wild caught, pregnant baboon with latent infection after 3 years in captivity.     

The epidemiologic significance of tuberculosis mycobacteria of the avian type]

Reaction to intradermal injection of tuberculin from Mycobacteria tuberculosis of the avian type proved to be negative in all the 505 students examined who never came in contact with fowl farms. Of 738 local residents it was found to be positive in 23.8% and of 320 workers of fowl farms--in 54.5% of cases. In response to the injection of Koch tuberculin and PPD-L the number of positive reactions in all the mentioned groups constituted 69-80%. A conclusion was drawn on the epidemiological danger of Mycobacteria of the avian type for the workers of fowl farms and, to a certain degree, for the surrounding population.     

Expression and purification of immunologically reactive DPPD, a recombinant Mycobacterium tuberculosis skin test antigen, using Mycobacterium smegmatis and Escherichia coli host cells

DPPD is a Mycobacterium tuberculosis recombinant antigen that elicits specific delayed type hypersensitivity reactions similar in size and morphological aspects to that elicited by purified protein derivative, in both guinea pigs and humans infected with M. tuberculosis. In addition, earlier clinical studies with DPPD suggested that this molecule could improve the specificity of the tuberculin skin test, which is used as an important aid for the diagnosis of tuberculosis. However, these studies could only be performed with DPPD engineered as a fusion molecule with another Mycobacterium spp. protein because no expression of DPPD could be achieved as a single molecule or as a conventional fusion protein in any commercial system. Although recombinant fusion proteins are in general suitable for several biological studies, they are by definition not ideal for studies involving highly purified and defined polypeptide sequences. Here, we report two alternative approaches for the expression of immunologically reactive recombinant genuine DPPD. The first approach used the rapidly growing, nonpathogenic Mycobacterium smegmatis as host cells transformed with the pSMT3 plasmid vector containing the full-length DPPD gene. The second approach used Escherichia coli transformed with the pET-17b plasmid vector containing the DPPD gene engineered in a three-copy fusion manner in tandem with itself. Though at low levels, expression and purification of immunologically reactive DPPD in M. smegmatis could be achieved. More abundant expression and purification of DPPD as a homo-trimer molecule was achieved in E. coli (> or =2 mg/L of bacterial broth cultures). Interestingly, expression could only be achieved in host cells transformed with the DPPD gene containing its leader peptide. However, the expressed proteins lacked the leader sequence, which indicates that processing of the M. tuberculosis DPPD gene was accurately achieved and necessary in both M. smegmatis and E. coli. More importantly, the delayed type hypersensitivity reactions elicited by purified molecules in guinea pigs infected with M. tuberculosis were indistinguishable from that elicited by purified protein derivative. Because the DPPD gene is present only in the tuberculosis-complex organisms of the Mycobacterium genus, these highly purified molecules should be helpful in identifying individuals sensitized with tubercle bacilli.