Tuberculosis in respiratory system--tracheo-bronchial tuberculosis, pulmonary tuberculosis, tuberculous pleurisy and thoracic empyema

Tuberculosis in respiratory system is most common in mycobacterial infections. Eighty percent of the patients with pulmonary tuberculosis visit hospital because of the respiratory symptoms, and only 10% of them were discovered by chest X-ray mass screening. In order to confirm respiratory tuberculosis, various methods to obtain specimens for mycobacterial examination have been carried out; hypertonic saline nebulizing for sputum expectoration, trans-bronchoscopic biopsy, percutaneous needle aspiration, and so on. The recent development of imaging modalities including CT, MRI, and ultrasonogram have been much contributed to the improvement of diagnosis of pleural tuberculosis. Basically, the main treatment for respiratory tuberculosis is chemotherapy except chronic tuberculous thoracic empyema. The initial chemotherapy regimen should be chosen among the three arms; [INH + RFP + PZA + EB (or SM)] x 2-->[INH + RFP] x 6, [INH + RFP + EB (or SM)] x 6-->[INH + RFP] x 3-6, and [INH + RFP] x 6-9. The sputum positive patient is recommended to have the chemotherapy regimen including PZA. In the patients with tracheo-bronchial tuberculosis an attention should be paid for the airway narrowing or obstruction during and after the scheduled chemotherapy. For a part of patients with tuberculous pleurisy and thoracic empyema, a surgical treatment must be indicated.     

NADH dehydrogenase defects confer isoniazid resistance and conditional lethality in Mycobacterium smegmatis

Isoniazid (INH) is a highly effective drug used in the treatment and prophylaxis of Mycobacterium tuberculosis infections. Resistance to INH in clinical isolates has been correlated with mutations in the inhA, katG, and ahpC genes. In this report, we describe a new mechanism for INH resistance in Mycobacterium smegmatis. Mutations that reduce NADH dehydrogenase activity (Ndh; type II) cause multiple phenotypes, including (i) coresistance to INH and a related drug, ethionamide; (ii) thermosensitive lethality; and (iii) auxotrophy. These phenotypes are corrected by expression of one of two enzymes: NADH dehydrogenase and the NADH-dependent malate dehydrogenase of the M. tuberculosis complex. The genetic data presented here indicate that defects in NADH oxidation cause all of the mutant traits and that an increase in the NADH/NAD+ ratio confers INH resistance.     

Inhibition of a Mycobacterium tuberculosis beta-ketoacyl ACP synthase by isoniazid

Although isoniazid (isonicotinic acid hydrazide, INH) is widely used for the treatment of tuberculosis, its molecular target has remained elusive. In response to INH treatment, saturated hexacosanoic acid (C26:0) accumulated on a 12-kilodalton acyl carrier protein (AcpM) that normally carried mycolic acid precursors as long as C50. A protein species purified from INH-treated Mycobacterium tuberculosis was shown to consist of a covalent complex of INH, AcpM, and a beta-ketoacyl acyl carrier protein synthase, KasA. Amino acid-altering mutations in the KasA protein were identified in INH-resistant patient isolates that lacked other mutations associated with resistance to this drug.     

Mechanisms involved in the intrinsic isoniazid resistance of Mycobacterium avium

Isoniazid (INH), which acts by inhibiting mycolic acid biosynthesis, is very potent against the tuberculous mycobacteria. It is about 100-fold less effective against Mycobacterium avium. This difference has often been attributed to a decreased permeability of the cell wall. We measured the rate of conversion of radiolabelled INH to 4-pyridylmethanol by whole cells and cell-free extracts and estimated the permeability barrier imposed by the cell wall to INH influx in Mycobacterium tuberculosis and M. avium. There was no significant difference in the relative permeability to INH between these two species. However, the total conversion rate in M. tuberculosis was found to be four times greater. Examination of in vitro-generated mutants revealed that the major resistance mechanism for both species is loss of the catalase-peroxidase KatG. Analysis of lipid and protein biosynthetic profiles demonstrated that the molecular target of activated INH was identical for both species. M. avium, however, formed colonies at INH concentrations inhibitory for mycolic acid biosynthesis. These mycolate-deficient M. avium exhibited altered colony morphologies, modified cell wall ultrastructure and were 10-fold more sensitive to treatment with hydrophobic antibiotics, such as rifampin. These findings may significantly impact the design of new therapeutic regimens for the treatment of infections with atypical mycobacteria.     

Reduction of isoniazid bioavailability in normal men by concomitant intake of food

The influence of food intake on the bioavailability of isoniazid (INH) has been examined in nine healthy male volunteers. INH was administered as a single oral dose, both in fasting state and together with a standardized breakfast. Numerous venous blood samples were obtained 5 min-6 hours after the INH ingestion, and the concentrations of unmetabolized INH in serum were assessed by spectrophotometry. The observations indicate that both the peak concentration and the total amount of INH absorbed are greatly reduced when the drug is ingested together with food. Hence it is recommended that, in the treatment of tuberculosis with INH, the drug should be given on an empty stomach. The data may also have some bearing on the use of INH for assessing acetylation rates and estimating dosages of hydralazine and related drugs.     

Discrimination of productive and non-productive cough by sound analysis

SETTING: Sixteen districts of Budapest, Hungary. OBJECTIVE: To determine the frequency of primary and secondary drug resistance, and to recommend treatment regimens. DESIGN: A retrospective survey. METHODS: Mycobacterium tuberculosis isolates were collected from 264 newly diagnosed and 147 previously treated patients. All strains were tested against isoniazid (INH), rifampicin (RIF), streptomycin (SM) and ethambutol (EMB) using the proportion method. Bacteriologic examinations were performed in the Diagnostic Laboratory of the Koranyi National Institute for Tuberculosis and Pulmonology in Budapest. RESULTS: Primary resistance to INH alone was 4%, to SM alone 2%, to RIF alone 0.4%, to INH and SM 1%, and to INH, RIF, SM and EMB 0.4%. Of the isolates of 78 relapse cases, six (8%) were resistant to INH alone, one (1%) to INH and RIF, two (3%) to INH, RIF, SM and EMB. Of the isolates of 69 patients notified with active tuberculosis for over a year, 51 (74%) were susceptible to the drugs tested. CONCLUSION: Based on the level of primary drug resistance as well as on the resistance pattern of relapse cases, it is recommended to start the treatment of newly detected and relapse cases with four drugs. The high rate of chronic cases with susceptible strains can be explained by poor compliance. To prevent development of resistant cases and to achieve good compliance, it is necessary to apply direct observation of treatment in all types of patients.     

Effects of overexpression of the alkyl hydroperoxide reductase AhpC on the virulence and isoniazid resistance of Mycobacterium tuberculosis

Mutations to the regulatory region of the ahpC gene, resulting in overproduction of alkyl hydroperoxide reductase, were encountered frequently in a large collection of isoniazid (INH)-resistant clinical isolates of Mycobacterium tuberculosis but not in INH-susceptible strains. Overexpression of ahpC did not seem to be important for INH resistance, however, as most of these strains were already defective for catalase-peroxidase, KatG, the enzyme required for activation of INH. Transformation of the INH-susceptible reference strain, M. tuberculosis H37Rv, with plasmids bearing the ahpC genes of M. tuberculosis or M. leprae did not result in a significant increase in the MIC. Two highly INH-resistant mutants of H37Rv, BH3 and BH8, were isolated in vitro and shown to produce no or little KatG activity and, in the case of BH3, to overproduce alkyl hydroperoxide reductase as the result of an ahpC regulatory mutation that was also found in some clinical isolates. The virulence of H37Rv, BH3, and BH8 was studied intensively in three mouse models: fully immunocompetent BALB/c and Black 6 mice, BALB/c major histocompatibility complex class II-knockout mice with abnormally low levels of CD4 T cells and athymic mice producing no cellular immune response. The results indicated that M. tuberculosis strains producing catalase-peroxidase were considerably more virulent in immunocompetent mice than the isogenic KatG-deficient mutants but that loss of catalase-peroxidase was less important when immunodeficient mice, unable to produce activated macrophages, were infected. Restoration of virulence was not seen in an INH-resistant M. tuberculosis strain that overexpressed ahpC, and this finding was confirmed by experiments performed with appropriate M. bovis strains in guinea pigs. Thus, in contrast to catalase-peroxidase, alkyl hydroperoxide reductase does not appear to act as a virulence factor in rodent infections or to play a direct role in INH resistance, although it may be important in maintaining peroxide homeostasis of the organism when KatG activity is low or absent.     

Which aminoglycoside or fluoroquinolone is more active against Mycobacterium tuberculosis in mice?

To identify the most active aminoglycoside or fluoroquinolone for the treatment of tuberculosis, the in vivo activities of four different aminoglycosides and three different fluoroquinolones were compared with that of isoniazid (INH) in a murine tuberculosis model. Mice were each inoculated intravenously with 2.3 x 10(7) CFU of Mycobacterium tuberculosis H37Rv. Treatment began the next day (D1) after inoculation and continued for 4 weeks, at the frequency of six times weekly with one of the following regimens: INH, 25 mg/kg; ofloxacin, 200 mg/kg; levofloxacin, 100 or 200 mg/kg; sparfloxacin (SPFX), 50 mg/kg; and streptomycin, kanamycin, amikacin (AMIKA), and isepamicin, all at 200 mg/kg. The dosages of the treatments were presumably equivalent to their clinically tolerated dosages. The severity of infection and effectiveness of the treatment were assessed by the survival rate, spleen weights, gross lung lesions, and the numbers of CFU in the spleens. The results indicate that INH is more bactericidal than any of the aminoglycosides or fluoroquinolones tested, that AMIKA is the most active aminoglycoside, and that SPFX at 50 mg/kg is far more bactericidal than the treatment with other fluoroquinolones.     

In vitro and in vivo studies on the role of dimethylsulfoxide (DMSO) in resensibilization of bacterial strains resistant to antibiotics and chemotherapeutic agents

Resensibilization in vitro to seven antibiotics under the influence of DMSO was studied in 624 resistant strains of five species of bacteria (E. coli, S. typhi, S. pyogenes, S. viridans, S. aureus), 61 strains of tubercle bacilli resistant to isonicotinic acid hydrazide (INH) and 19 strains of tubercle bacilli resistant to rifampicin (RMP). DMSO in concentrations of 0.1-10.0% caused reversion of sensitivity in strains of E. coli, S. pyogenes and S. viridans. Reversion in vivo of sensitivity to INH of tubercle bacilli was studied in experimental tuberculosis of guinea pigs. Tubercle bacilli previously resistant to INH recovered complete sensitivity to the drug, enabling animals infected with the INH-resistant strain of bacilli to be treated with INH.     

Multidrug-resistant tuberculosis. 3. Epidemiology of drug-resistant tuberculosis in Japan

In Japan, the frequency of drug-resistant tuberculosis has been investigated every 5 years since 1950s and increase of initial and acquired drug resistance has not been observed. However, the mathematical model analyse of time trend of prevalence of drug-resistant tuberculosis and frequency of initial drug resistance in Korea shows that there is little difference of infectivity and/or proportion of clinical breakdown between susceptible bacilli and resistant ones. The prognosis of isoniazid (INH) and rifampicin (RFP) resistant tuberculosis cases in Fukujuji Hospital was investigated. 367 cases including 50 initial drug resistant cases were analyzed with life table analysis. 50% of all cases and 70% of initial drug resistant cases became negative, 13% of all cases and 4% of initial drug resistant cases remained as positive, 37% of all cases and 27% of new cases died. Among cases who did not convert negative within one year, 41% of all cases and 34% of initial drug resistant cases died. The prognosis of INH and RFP resistant tuberculosis cases were still not satisfactory.     

Isoniazid acetylator status of Black South African tuberculosis patients

Black male tuberculosis patients (106) were phenotyped into 59% fast and 41% slow acetylators with isoniazid (NH) plasma half-lives. The antimode time dividing the two acetylator groups was longer than that previously reported for Whites. The therapeutic significance of INH acetylator phenotyping per se is questioned since it provides neither a measurement of the amount of INH absorption nor of its distribution within the body.     

Chemotherapy for tuberculosis; yesterday, today, and tomorrow--basic and clinical studies

The discovery of streptomycin in 1944 had given rise to great flowering of chemotherapy for tuberculosis. The times which triple treatment of SM.PAS.INH after the temporal time of SM.PAS had been standard regimens on initial treatment had continued for more than twenty years. The shortening of duration for chemotherapy had become possible by the introduction of RFP, and the duration had reduced to one fourth compared with that of the regimens till then by the addition of PZA for two months at the beginning of treatment on the initial treatment cases. In this paper, historical aspects of early and present-day chemotherapy of tuberculosis and the reports of main studies have been summarized, and pharmacokinetics of INH, action of antituberculous drugs in short-course chemotherapy, MDR-TB and biological response modifiers for treatment of tuberculosis, etc. has been reviewed. It is urgently awaited that more new drugs without cross resistance to previous drugs will be developed for the more shortening of the duration and the improvement of the treatment for MDR-TB.     

Ocular tuberculosis

The frequency of tuberculous uveitis has extremely decreased in Japan. Anterior granulomatous or non-granulomatous uveitis, chorioretinitis and retinal vasculitis are common ocular manifestations, while tuberculoma, scleritis, keratitis and orbital tuberculosis are rare. The diagnosis of ocular tuberculosis is extremely difficult because ocular tuberculosis tends to be negative in chest x-ray or tuberclin skin test. To diagnose ocular tuberculosis clinically some ophthalmologists recommend subconjunctival tuberculin test or therapeutic isoniazide (INH) test. Recently, for confirmed diagnosis, polymerase chain reaction (PCR) technique has been used to detect mycobacterium in intraocular samples such as aqueous or vitreous humor. The mainstay of treatment is antituberculosis agents. Active retinal vasculitis or tuberculoma are generally responsive to corticosteroid therapy. Although ocular tuberculosis is rare, it must be considered as one of the possible causes of uveitis.     

E-test for susceptibility testing of Mycobacterium tuberculosis

SETTING: Initial isolates should be tested for drug susceptibility to confirm the anticipated effectiveness of chemotherapy. OBJECTIVE: To evaluate E-test strips for susceptibility testing of Mycobacterium tuberculosis. DESIGN: A proportion method using Lowenstein-Jensen medium and the Bactec radiometric system were compared with the E-test (isoniazid [INH], rifampicin [RMP], ethambutol [EMB] and streptomycin [SM]). RESULTS: For 73 of the 81 M. tuberculosis isolates (90.1%) the proportion and E-test methods yielded concordant susceptibility results against all four antimicrobial agents tested. Of these 73 strains, 69 were fully susceptible; the four isolates showing resistance to antimicrobial drugs by both methods were also resistant when tested by Bactec 460TB. While the proportion method indicated susceptibility for the eight remaining strains, E-test results showed mono EMB resistance in five strains, INH resistance for two isolates (including one isolate resistant to EMB plus INH), and for one strain E-test yielded resistance to EMB and SM. Using Bactec as the reference method, the E-test resulted in false resistance in eight strains and no false susceptibility. CONCLUSION: Due to a substantial rate of false resistance, this method cannot be recommended at present for practical use in clinical laboratories.     

Multidrug-resistant tuberculosis. 2. Mechanisms of drug-resistance in Mycobacterium tuberculosis--genetic mechanisms of drug-resistance

Multidrug-resistant Mycobacterium tuberculosis infection is now world wide health problem. However, according to the recent advances of molecular biological technics, some of the genetic mechanisms of drug-resistance of M. tuberculosis has been uncovered. Generally, drug-resistance of M. tuberculosis was caused by point mutations in chromosomal gene. In isoniazid (INH) resistant M. tuberculosis, mutations and genetic deletions in catalase-peroxidase gene (katG), inhA gene, or alkyl hydroperoxide reductase gene were reported. We also found that about 15% of INH-resistant M. tuberculosis isolates lacked katG gene, and these isolates showed highly resistance to INH with MIC > or = 64 micrograms/ml. On the other hand, mutations and other genetic alterations in RNA polymerase beta subunit gene (rpoB) were the major mechanisms of resistance to rifampicin (RFP) with high frequencies of 90% or more. Our evaluation of the relationship between RFP susceptibility and genetic alteration in rpoB gene also showed that 95% of RFP-resistant M. tuberculosis isolates involved genetic alterations in 69 bp core region of rpoB gene. Moreover, these genetic alterations in rpoB gene were suspected as the resistant mechanism to other rifamycin antituberculosis drugs, such as rifabutin and KRM-1648. In addition, it was reported that point mutations in 16S rRNA gene (rrs) and ribosomal protein S12 gene (rpsL) induced M. tuberculosis as streptomycin (SM) resistant phenotype. We analyzed genetic alternations in rpsL gene of clinically isolates of M. tuberculosis, about 60% of SM resistant isolates were shown point mutation in this gene ant they were all high SM-resistant with MIC > or = 256 micrograms/ml. Furthermore, nicotinamidase (pncA) gene, DNA gyrase A subunit (gyrA) gene, and embB gene were reported as the responsible gene to pyrazinamide-, quinolone- and ethambutol-resistance, respectively. Although all mechanisms of drug-resistance were still unclear, these informations are very useful and helpful for development of rapid diagnosis system of drug-resistant M. tuberculosis.     

Attendance versus compliance with tuberculosis treatment in an occupational setting--a pilot study

AIM: To determine the prevalence of non-compliance with tuberculosis treatment at Freegold Mines. OBJECTIVES: 1. To establish the rates of attendance and collection of anti-tuberculosis drugs. 2. To determine prevalence of non-compliance by means of urine tests. DESIGN: A cross-sectional study conducted over 2 weeks at mine medical stations. METHOD: Urine samples were collected from tuberculosis patients 3 hours after drug ingestion. Non-compliance was established by testing these samples for rifampicin and/or isoniazid (INH) metabolites. Non-compliance was defined as a negative urine test result for these drugs in participants whose treatment regimens included one or both. Daily attendance and collection of drugs statistics are recorded in the medical station tuberculosis register. The patient rate of adherence was calculated as the observed number of days on which medication had been collected over the expected treatment days in a given period. RESULTS: Urine test results showed an overall prevalence of non-compliance of 14.6 +/- 3.3%. The study showed that non-compliance with tuberculosis treatment was underestimated by the surveillance data. The rate of non-adherence with treatment established from the formal surveillance procedure was 0.2%. The poor response rate of patients was found to be a major problem and fewer than 40% per day returned to bring urine specimens. The mean prevalences of non-compliance established by rifampicin and INH tests were 19.5 +/- 5.3% and 9.8 +/- 3.9%, respectively, and these were significantly different (Chi 2 = 7.44; P < 0.05). The proportion of false-positive results for INH and rifampicin urine tests were 21% (11/53) and 35% (17/48), respectively, showing that some patients were taking the wrong treatment. CONCLUSIONS: It is clear that attendance at the clinics does not accurately reflect compliance. Both programme compliance (dispensing of the correct treatment) and patient compliance need to be improved. This has important implications for the new national tuberculosis control policy adopted by the South African government that stresses the importance of directly observed therapy, short-course (DOTS) and a patient-centred approach.     

The pharmacokinetics of isoniazid in children (author's transl)

The purpose of this study, which involved 134 children aged between 0.5 and 17 years, was to investigate the metabolism of isoniazid (INH) in children and to provide guide-lines for dosage. The distribution of slow (55,5%) and fast (44,5%) acetylators was the same in children as in adults. However, the mean of INH inactivation index were lower (0.23 and 0.48) while distribution volumes, (1.30 +/- 0.06 and 1.57 +/- 0.17 1/kg) and total plasma clearances (5.39 +/- 0.43 and 14.7 +/- 1.5 ml/Kg/min) were higher than in adults. Plasma half-lives were similar in children and adults. These results indicate that INH is more rapidly metabolized in children owing, it is suggested to a higher liver weight : body weight ratio and to a more pronounced first pass effect. The doses of INH therefore must be higher in children and strictly adapted to each individual.     

Study of oxidative-stress in isoniazid-rifampicin induced hepatic injury in young rats

The role of oxidative-stress as a mechanism of hepatotoxicity caused by combination of isoniazid (INH) and Rifampicin (RMP) was investigated in young growing rats. A successful model of hepatotoxicity was produced by giving 50 mg/kg/day each of INH and RMP in two weeks. Liver showed type II hepatocellular changes (microvesicular fat deposition) with mild portal triaditis. The glutathione and related thiols were significantly decreased in both blood and liver tissues with combination of INH and RMP treatment. Superoxide dismutase, glutathione peroxidase, catalase and glutathione-S-transferases with CDNB and DCNB as substrates were decreased in the combination treated group. Glutathione reductase, glutathione-S-transferase with ethacrynic acid as substrate and lipid peroxidation exhibited a significant increase with treatment. The altered profile of antioxidant enzymes with increased lipid peroxidation indicated the enhanced oxidative-stress in combination of INH and RMP treatment. All the findings are faithfully reflected in the blood tissue except superoxide dismutase which showed significant enhancement in this tissue. INH and RMP hepatotoxicity is thus appeared to be mediated through oxidative-stress.     

Tuberculous meningitis in children before and since isoniazid

The use of isoniazid (INH) in persons exposed to active cases of tuberculosis has been challenged, Reports of toxic reactions to isoniazid warrant a review of the drug's potential benefits and hazards. This prompted a retrospective survey of cases admitted to a large county hospital to determine admission incidence before and since initiation of a program of case-finding and INH chemoprophylaxis for children in 1953. During the 24-year period surveyed (1950-1973), the population of the county increased twofold while the yearly admission rate for tuberculous meningitis in children fell from a high of eight cases to a low of two. This dramatic drop in cases admitted, coupled with an absence of any toxic reactions to the drug, provides support for continuation of the program of case-finding and isoniazid chemoprophylaxis.     

Results of the calcitonin stimulation test in normal volunteers compared with genetically unaffected members of MEN 2A and familial medullary thyroid carcinoma families

SETTING: Sample survey based on pulmonary tuberculosis (TB) patients registered in 264 health centres in Korea, compared with data obtained from nationwide TB prevalence surveys conducted since 1965. OBJECTIVE: To determine the level of antituberculosis drug resistance (DR) and to assess its impact on treatment outcome and its relationship with cure rates in the National TB Programme (NTP). DESIGN: Mycobacterium tuberculosis isolates from 2,486 new patients and 189 previously treated patients were subjected to susceptibility testing against 10 antituberculosis drugs. Treatment outcome was assessed. The DR levels were compared with those observed in the national TB prevalence surveys, and the trend was correlated with the cure rate of patients treated in the NTP. RESULTS: Resistance to any drug was 11.3% in new cases and 54.0% in previously treated cases. Initial resistance to isoniazid (INH) or rifampicin (RMP) was 7.7% or 2.2%, and to INH and RMP (+/- other drugs) 1.6%. Compared with previous data, initial drug resistance (IDR) has decreased significantly and is inversely related to improvement of cure rates in the NTP. The treatment outcome of patients with single drug resistance was satisfactory. CONCLUSION: Drug-resistant TB has decreased remarkably during the last decades in Korea as a result of improved efficiency in the treatment programme of the NTP.