Can BCG-vaccinated children be included in tuberculin surveys to estimate the annual risk of tuberculous infection in India?

SETTING

Selected villages in three defined zones of India.

OBJECTIVES

To compare the estimated prevalence of tuberculous infection among children with and without bacille Calmette-Guérin (BCG) scar.

STUDY DESIGN

During a nationwide tuberculin survey, 1-9-year-old children were tuberculin tested using 1TU-PPD RT23 with Tween 80.

RESULTS

In the 5-9 year age group, subgroups of tuberculous infected children could be seen as distinct humps among those with or without BCG scar, but not in those aged 1-4 years. In children aged 1-4 years, the estimated prevalence of infection was respectively 3.5%, 3.8% and 3.6% among children without BCG scar, and 4.8%, 4.7% and 4.5% among children with BCG scar in the western, northern and eastern zones. In those aged 5-9 years, the estimated prevalence was respectively 10.4%, 11.0% and 9.1% among children without BCG scar and 11%, 11.9% and 8.7% among children with BCG scar in the three zones. Thus, in children aged 1-4 years, the estimated prevalence among those with BCG scar was considerably higher than in those without BCG scar. This difference was small in those aged 5-9 years.

CONCLUSION

Tuberculin surveys may be conducted irrespective of BCG scar status among children aged 5-9 years, when BCG vaccination is given using Danish 1331 strain during infancy under the Expanded Program of Immunization.

Protective effect of BCG among children vaccinated under universal immunization programme

A case-control study was conducted to estimate the protective effect of BCG vaccination against tuberculosis among children. The children with suspicion of tuberculosis (TB) attending two hospitals in Bangalore city were registered into the study and subjected to detailed clinical examination and investigations. The presence of BCG scar was taken as evidence of vaccination. Modified Stegen-Jones scoring method was adopted for diagnosing TB. The hospital children with score of 7 were considered as TB cases. Children residing in the neighbourhood of cases were similarly investigated and those scoring 4 were labeled as controls. A total of 118 age-sex matched case-control pairs were identified and final analysis was confined to 113 cases and 109 controls after excluding children with doubtful BCG scar. A low protective effect of BCG vaccination at 31% (not significant, statistically) was observed against TB - all forms combined, among children vaccinated as under Universal Immunization Programme. Though the protective efficacy against extra-pulmonary TB was observed to be higher than for pulmonary TB, it was also not significant, statistically. It will be appropriate to conduct further studies on protection rendered by BCG vaccination against tuberculous meningitis and other severe forms of TB. Besides, the quality of vaccination programme including cold chain maintenance also needs to be evaluated.

The annual risk of tuberculous infection in the eastern zone of India

SETTING

Rural and urban areas of eight selected districts in the eastern zone of India.

OBJECTIVES

To estimate the annual risk of tuberculous infection (ARTI).

STUDY DESIGN

A community-based, cross-sectional tuberculin survey was conducted among children aged 1-9 years residing in a sample of rural and urban areas. Stratified two-stage cluster sampling was adopted for selection of rural and urban clusters. A total of 40964 children in 515 clusters underwent tuberculin testing and reading with 1TU PPD RT23 with Tween 80; the maximum transverse diameter of induration was measured about 72 h after the test.

RESULTS

A bacille Calmette-Gúerin (BCG) scar was observed in 51.5% of the test-read children. The frequency distribution of tuberculin reaction size among 19332 children without BCG scar was found to be bimodal, with the mode of reactions attributable to infection with tubercle bacilli at 20 mm. The prevalence of infection was estimated as 6.9%. The ARTI computed from the estimated prevalence was 1.3%. Children residing in the urban areas were found to be at a significantly higher risk of infection than those residing in rural areas.

CONCLUSION

The high rate of ARTI in the eastern zone of India suggests a need for committed, sustained action in provision of quality tuberculosis control services.

The annual risk of tuberculous infection in Orissa State, India

SETTING

Rural and urban areas of eight selected districts of Orissa State, India.

OBJECTIVES

To estimate the average annual risk of tuberculous infection (ARTI) in the state.

DESIGN

A community-based, cross-sectional tuberculin survey was conducted among children aged 1-9 years residing in a sample of rural and urban areas of eight districts of Orissa State. A stratified sampling was adopted for selection of clusters. Highly trained designated tuberculin testers administered 0.1 ml (1 TU) of PPD RT 23 with Tween 80 by the Mantoux method to 10 626 children. Transverse tuberculin reaction sizes were measured about 72 h later by trained designated tuberculin readers. The number of children satisfactorily test-read was 10 191.

RESULTS

Based on the frequency distribution of tuberculin reaction sizes, the average ARTI in the state was estimated at 1.7-1.8%. The children residing in urban areas were observed to be at a significantly higher risk of infection than those in rural areas.

CONCLUSION

The study in Orissa State suggests high rates of transmission of tuberculous infection and calls to attention the need for intensification of concerted and sustained tuberculosis control efforts.

Estimation of annual risk of tuberculosis infection (ARTI) among children aged 1-9 years in the south zone of India

OBJECTIVE

To estimate the annual risk of tuberculosis infection (ARTI) among children aged 1-9 years in the south zone of India.

SETTING

The survey was carried out in a representative sample of villages and census enumeration blocks of towns in four south Indian states, as a part of a nationwide tuberculin survey.

DESIGN

Six districts were selected through systematic random sampling. Four hundred and twenty rural clusters and 180 urban clusters were selected from these districts on the basis of the rural-urban ratio in the entire zone. To obtain the required sample of 12,000 children without bacille Calmette-Guérin (BCG) vaccination, 51,000 had to be covered. Eighty-five children from each cluster were tuberculin tested and read for reaction sizes. The ARTI was computed from the estimated prevalence of TB infection among children without a BCG scar.

RESULT

Among 52,951 children registered for the study, 50,846 (96%) had a tuberculin test result. The BCG coverage for the study population was about 65%. Among 17,811 children without a BCG scar, the prevalence of infection was 5.9% (95%CI 4.0-7.7%); the corresponding ARTI was 1.0% (95%CI 0.7-1.4%) [correction].

CONCLUSION

The estimated ARTI for the south zone is 1.0%, as compared to the national average of 1.7% used for programme evaluation. This baseline information should be useful for the assessment of future trends.

Annual risk of tuberculous infection in Khammam a tribal district of Andhra Pradesh

A tuberculin survey to estimate annual risk of tuberculosis was conducted in Khammam tribal district during 2001-2002. A total of 8637 children were test-read--2991 without BCG scar and 5442 with BCG scar. The tests were performed using ITU PPD RT23 and the maximum size of induration was recorded at about 72 hours after the test. Based on the frequency distribution of reaction size, cut-off point for infection with tubercle bacilli was considered at 12 mm. Using this criterion, the prevalence of infection was estimated at 11.8% among children without BCG scar and 10.6% among children with BCG scar. This difference was found to be statistically insignificant. ARTI rates computed from the prevalence estimates among children without and with BCG scar were 1.6% and 1.5% respectively. It was computed as 1.5% from the prevalence in the combined group i.e. irrespective of BCG scar status.

Annual risk of tuberculous infection in the western zone of India

SETTING

Rural and urban areas of six selected districts in the western zone of India.

OBJECTIVES

To estimate the annual risk of tuberculous infection (ARI).

DESIGN

A community-based, cross-sectional tuberculin survey was conducted among children aged 1-9 years residing in a sample of rural and urban areas of six districts in the western zone of India. Stratified two-stage cluster sampling was adopted for selection of rural and urban clusters. A total of 48473 children in 600 clusters underwent tuberculin testing with 1TU PPD RT23 with Tween 80; the induration was measured about 72 h after the test.

RESULTS

The BCG scar was observed in 52% of the test-read children. Estimation of the prevalence of infection was based on the frequency distribution of tuberculin reaction size among 22259 children without BCG scar. Reactions > or = 15 mm were considered attributable to infection with tubercle bacilli. The prevalence of infection was estimated to be 9.3%, and the ARI computed from the estimated prevalence was 1.8%. The proportion of infected children was found to be significantly higher in urban than in rural areas.

CONCLUSION

The high rate of ARI in the western zone of India calls for further intensification of tuberculosis control efforts.

Annual risk of tuberculous infection in rural areas of Uttar Pradesh, India

SETTING

Rural areas in Uttar Pradesh, the most populous state in India.

OBJECTIVES

1) To estimate the average annual risk of tuberculous infection (ARI), 2) to study ARI trends with age, and 3) to compare tuberculin reactions among children with and without BCG scar.

STUDY DESIGN

A cross-sectional tuberculin survey was conducted among children aged 1-9 years residing in Rae Bareli, Hardoi and Jaunpur districts, Uttar Pradesh. Tuberculin testing was performed using 1TU of PPD RT23 with Tween 80, and indurations were measured 72 hours later. Prevalence of infection was estimated in children without BCG scar based on the cut-off point identified on the frequency distribution of reaction sizes. The ARI was computed from the estimated prevalence.

RESULTS

The proportion of children with BCG scar varied from 25% to 31% in the study districts. Using a cut-off of 14 mm among children without BCG scar, the ARI was estimated at 2.3% in Rae Bareli, 1.9% in Hardoi and 1.5% in Jaunpur, and was observed to increase with age. Tuberculin test results among children with BCG scar suggest that they may be included in tuberculin surveys to estimate ARI.

CONCLUSION

High rates of transmission of tuberculous infection suggest that tuberculosis control measures need to be intensified.

Epidemiological situation of tuberculosis in India

Epidemiological information on tuberculosis (TB) is vital for planning the control strategies in addition assessing the impact of intervention programmes. The survey findings by ICMR revealed the prevalence of sputum positive pulmonary TB is about 4 per 1000 population and an estimated 1.5 million infectious cases spreading infection in the community. Studies conducted by the National Tuberculosis Institute, Bangalore revealed similar diseases prevalence of sputum positive pulmonary TB. The annual risk of tuberculous infections defined as the probability of acquiring new infection with tubercle bacilli over a period of one year is the key parameter for the epidemiological study in developing countries. It is estimated that there are about 4.6 lakhs death in the country every year with one person dying every minute. The average annual risk of tuberculous infection is about 1.7%. The prospects of decreasing TB case now look good provided that all TB cases have access to the DOTS strategy by bringing the remaining uncovered half of the population under RNTCP.

PPD RT23 for tuberculin surveys in India

SETTING

Tuberculosis sanatoria and villages in Bangalore district.

OBJECTIVES

To study the appropriateness of continuing to use 1TU dilutions prepared by the BCG Laboratory, Guindy, in Chennai, India, from a freeze-dried form of PPD RT23 with Tween 80 received from Statens Serum Institut (SSI), Copenhagen, for tuberculin surveys in India.

DESIGN

The responses to dual tuberculin tests were compared among: 1) 63 smear-positive cases using 2TU PPD prepared by the Guindy laboratory (Dilution-G), and 2TU PPD prepared by the SSI (Dilution-S); 2) 124 smear-positive cases using 1TU and 2TU Dilution-G; and 3) 1,338 apparently healthy children using 1TU and 2TU Dilution-G. Test sites were allocated randomly using the double-blind technique. Tuberculin responses obtained during studies conducted in India and in other countries were compared.

RESULTS

The differences in sensitivity of tuberculin testing using the different preparations were found to be small and statistically non-significant. Among children, a higher proportion of reaction sizes in 10-14 mm and 15 + mm categories was observed to 2TU compared to 1TU of Dilution-G. This could reflect lower specificity of 2TU in the study area where non-specific sensitivity is highly prevalent. Studies in India and other countries do not suggest any loss in potency of 1TU PPD RT23 with Tween 80.

CONCLUSION

1TU dilutions of PPD RT23 with Tween 80 provided by the BCG Laboratory, Guindy, may continue to be used for tuberculin surveys in India.

Annual risk of tuberculous infection in the northern zone of India

OBJECTIVE

To estimate the annual risk of infection with tubercle bacilli in the northern zone of India.

METHODS

A community-based cross-sectional tuberculin survey was conducted among children aged 1-9 years who lived in a sample of villages and urban blocks of six selected districts in a defined north zone of India. A two-stage cluster sampling method was used to select rural and urban clusters. A total of 48 624 children in 598 clusters were subjected to tuberculin testing with one tuberculin unit (1 TU) of PPD RT23 stabilized with Tween 80. The maximum transverse diameter of induration was measured about 72 hours after the test.

FINDINGS

Among the 48 624 test-read children, 22 064 (45.4%) had a bacille Calmette-Gu rin (BCG) scar. On the basis of the frequency distribution of tuberculin reaction size among 25 816 children without a BCG scar, the prevalence of infection with tubercle bacilli was estimated as 10.3%. The annual risk of infection was computed as 1.9%. The proportion of infected children was significantly higher in urban than rural areas.

CONCLUSION

The high rate of tuberculous infection in the north zone of India suggests the need for further intensification of tuberculosis control efforts on a sustained and long-term basis.

Annual risk of tuberculous infection in rural areas of Junagadh district

Paucity of epidemiological data on tuberculosis in India prompted the National Tuberculosis Institute, Bangalore to embark upon a nation-wide survey to estimate the Annual Risk of Tuberculosis Infection in different parts of the country. The survey in Junagadh district, one of the 26 districts drafted under the nation-wide survey is reported here. The prevalence of infection from the analysis of 3164 children not displaying scars of the BCG vaccination was 4.16% (CI: 3.17-5.14) and from this data the ARI was computed as 0.73% (CI: 0.55-0.91). The inclusion of vaccinated children into the study group yielded similar results. The estimate of the ARI in Junagadh district is lesser than that in several other parts of India which is probably in consonance with its better socio-economic development.

Tuberculin test

Although tuberculin test is widely used for detection of tuberculous infection among children, there is no clear understanding about its performance and interpretation. This article has been written with the purpose of elucidating the performance and interpretation of standard tuberculin test, based on the experiences gained at the National Tuberculosis Institute, Bangalore and other centres. The standard tuberculin test involves intradermal injection of '1TU PPD RT23 with Tween 80' on the mid-volar aspect of forearm and measurement of the maximum transverse diameter of induration after 3 days. Larger the size of induration, higher is the probability of it being due to tuberculous infection. The majority of reactions with induration size of 15 mm and above are attributable to infection with tubercle bacilli, irrespective of BCG-vaccination status. While indurations of less than 5 mm indicate absence of any kind of tuberculin sensitivity, the majority of indurations in 5-9 mm range are usually of non-tuberculous nature. An induration of 10-14 mm requires more careful interpretation. It is more likely to be attributable to infection with tubercle bacilli in case of history of contact with smear positive case or among children with clinical findings of tuberculosis. However, the size of induration in an infected child may be diminished in the presence of immuno-suppressive conditions. One should also consider the purpose of the test while interpreting the test results.

Effect of gossypol on domestic fowl, Gallus domesticus

Domestic fowls (Gallus domesticus) were administered gossypol (10 mg/kg body weight/day) by oral intubation for 15 weeks. Drug treatment did not have any effect on body growth rate. The drug treatment, however, caused a marked decrease in the weights of testis and epididymis. Predominant changes in the histoarchitecture of testis (desquamation of germinal epithelium and inhibition of spermatogenesis) were observed following gossypol treatment. Epididymal tubules in gossypol treated animals were devoid of spermatozoa. Gossypol treatment had no effect on hematological parameters (total erythrocyte count, total leucocyte count, hematocrit and hemoglobin) studied in the present investigations.

Inhibition of liver alcohol dehydrogenase and ethanol metabolism by 3-substituted thiolane 1-oxides

3-Substituted thiolane 1-oxides (methyl, n-butyl, n-hexyl, and phenyl) were prepared and tested as inhibitors of horse, monkey, and rat liver alcohol dehydrogenases and of ethanol metabolism in rats. These compounds inhibit alcohol oxidation in an uncompetitive manner with respect to ethanol as a varied substrate. Lengthening the alkyl substituent increased the inhibitory potency because of tighter binding in the hydrophobic substrate binding pocket of the alcohol dehydrogenases. Thus, the 3-hexyl derivative was the most potent inhibitor of the purified rat liver alcohol dehydrogenase, with a Kii value of 0.13 microM. The 3-butyl derivative was the best inhibitor of ethanol metabolism in rats, with a Kii value of 11 mumol/kg. The acute toxicity in mice of the butyl derivative was 1.4 mmol/kg. Since high concentrations of alcohol do not prevent the inhibitory effects of these compounds, they may be particularly useful for preventing poisoning by methanol or ethylene glycol.

Inactivation of horse liver alcohol dehydrogenase by modification of cysteine residue 174 with 3-bromopropionic acid

Horse liver alcohol dehydrogenase is inactivated with Michaelis kinetics at pH 7 and 25 degrees C by 3-bromopropionic acid. In the absence of NAD+, the Ki is 2 mM, and the pseudo bimolecular rate constant (k3/Ki) is 0.03 M-1 s-1; in the presence of 1 mM NAD+, Ki is 2.3 mM, and k3/Ki is 0.006 M-1 s-1. 3-Bromopropionic acid is a competitive inhibitor, Ki of 0.4 mM, against ethanol as a substrate. Inactivation was prevented in the ternary complexes with NAD+ X pyrazole and NADH X isobutyramide, was retarded by NAD+, NADH, or bipyridine, and was almost unaffected by imidazole and AMP. Carboxyethylated enzyme did not detectably (as observed spectrophotometrically) bind bipyridine, NAD+, or NADH. Enzyme was inactivated with radioactive 3-bromopropionic acid, aminoethylated, and digested with trypsin and chymotrypsin. Analysis of the labeled peptides showed that Cys-174 was predominantly modified. In the presence of 1 mM NAD+, the reaction was much less specific. The interaction of the carboxyl group of 3-bromopropionic acid with the guanidino group of Arg-369 probably facilitates the selective reaction with Cys-174, which is ligated to the zinc at the active site. Carboxyethylation apparently inactivates by interfering with the proper binding of the pyrophosphate of the coenzyme to the enzyme.

Inhibition by carboxamides and sulfoxides of liver alcohol dehydrogenase and ethanol metabolism

Sulfoxides and amides were tested as inhibitors of liver alcohol dehydrogenase and ethanol metabolism in rats. With both series of compounds, increasing the hydrophobicity resulted in better inhibition, and introduction of polar groups reduced inhibition. Of the cyclic sulfoxides, tetramethylene sulfoxide was the best inhibitor as compared to the tri- and pentamethylene analogue and other compounds, and it may be a transition-state analogue. The most promising compounds, tetramethylene sulfoxide and isovaleramide, were essentially uncompetitive inhibitors of purified horse and rat liver alcohol dehydrogenases with respect to ethanol as substrate. These compounds also were uncompetitive inhibitors in vivo, which is advantageous since the inhibition is not overcome at higher concentrations of ethanol, as it is with competitive inhibitors, such as pyrazole. The uncompetitive inhibition constants for tetramethylene sulfoxide and isovaleramide for rat liver alcohol dehydrogenase were 200 and 20 microM, respectively, in vitro, whereas in vivo the values were 340 and 180 mumol/kg. The differences in the values may be due to metabolism or distribution of the compounds. Further studies will be required to determine if isovaleramide or tetramethylene sulfoxide is suitable for therapeutic purposes.

Use of N-bromosuccinimide in the synthesis of heterocyclic systems

N-Bromosuccinimide has been used in the synthesis of a series of imidazothiazoles. It is both quicker and more convenient to use than other reagents.