Does the BCG vaccine have different effects on strains of tuberculosis?

Several explanations have been suggested concerning the variety in bacille Calmette-Guerin (BCG) vaccine efficacy on strains of Mycobacterium tuberculosis (Mtb). This study aimed to compare the effect of BCG vaccination history in the prevention of the occurrence of Mtb-Beijing and non-Beijing strains. In this cross-sectional study, 64 patients with pulmonary tuberculosis (TB) were recruited from the Iranian border provinces (North West and West). Isolates were subjected to restriction fragment length polymorphism (RFLP) analysis, using the insertion sequence IS6110 as a probe (IS6110 RFLP) and drug susceptibility testing using the proportion method. Samples were analyzed with Gel Compare II 6.6 and spss version 18. The mean age [standard deviation (SD)] of the patients was 54·4 (SD = 17·0). Overall, 49 cases (76·56%) had no BCG vaccination scar. The prevalence of Beijing strains was 9·38% and drug resistance proportion among the isolates was 14·1% (nine cases). There was a significant relationship between Beijing strains and tuberculosis (TB)-drug resistance in isolates (χ2  = 26·29, P < 0·001). There was also a strong association between vaccination history and Beijing strains (χ2  = 13·23, P = 0·002). Also, a statistical relationship was observed between Beijing strains and drug-resistant TB among patients with a history of vaccination (χ2  = 7·47, P = 0·002). This association was not maintained in the unvaccinated group (P = 0·102). These findings confirm the claim that the vaccine has different effects on different subspecies of tuberculosis. The cause of the high probability of drug resistance in patients with Beijing-TB and vaccination history requires further investigation with a higher sample size.

Comparing IS6110-RFLP, PGRS-RFLP and IS6110-Mtb1/Mtb2 PCR methods for genotyping of Mycobacterium tuberculosis isolates.

AIMS: Tuberculosis (TB) is still an important disease in the world, especially in developing countries. Applying efficient and suitable methods for genotyping Mycobacterium tuberculosis (MTB) isolates is a crucial step for identifying the MTB transmission mode and controlling its subsequent outcomes. Considering the complexity of IS6110-RFLP and PGRS-RFLP methods for MTB classification, suggesting other simple but reliable techniques could be helpful in the MTB studies, especially in low-income countries. METHODS AND RESULTS: This study aimed to evaluate the capabilities of three methods for genotyping MTB isolates collected from Iran through comparing our previously published results for IS6110-RFLP and PGRS-RFLP methods and current results obtained from IS6110-Mtb1/Mtb2 PCR technique. A strong concordance was observed between the results of clustering by three techniques. Calculated Kendall's Tau concordance value for correlation of IS6110-RFLP and IS6110-Mtb1/Mtb2 PCR, for IS6110-RFLP and PGRS-RFLP, and for IS6110-Mtb1/Mtb2 PCR and PGRS-RFLP techniques was equal to 0·943, 0·898 and 0·85 respectively. CONCLUSIONS: A strong correlation between IS6110-Mtb1/Mtb2 PCR, and IS6110-RFLP and PGRS-RFLP methods was observed and therefore IS6110-Mtb1/Mtb2 PCR discriminates MTBs capably. SIGNIFICANCE AND IMPACT OF THE STUDY: The study showed that IS6110-Mtb1/Mtb2 PCR, which is a simple and economical MTB genotyping approach, could be a more appropriate method to be applied in the low-budget research programmes.

Epidemiology and patterns of drug resistance among tuberculosis patients in Northwestern Iran.

BACKGROUND: Multidrug-resistant tuberculosis (MDR-TB) has emerged as an important global health concern and is on the rise throughout the world. OBJECTIVE: The aim of this study was to examine the epidemiology and pattern of TB drug resistance. METHODS: In this cross-sectional study, 180 pulmonary TB patients from two Northwestern provinces of Iran were selected. The first and second line drug susceptibility testing was carried out using the 1% proportion method on the Lφwenstein-Jensen medium. Full demographic, environmental and clinical history was evaluated. RESULTS: Prevalence of resistance to any TB drug was 13.8%. Eight (4.4%) patients had MDR-TB (2.4% in the province of East Azerbaijan and 9.3% in the province of Ardabil) and one patient had extensively drug-resistant TB. Patient resistance to both isoniazid and streptomycin was the most prevalent at a rate of 8.3%. Patients showed the least resistance to ethambutol (2.8%). There was a significant relationship between the previous history of TB drug treatment and TB drug resistance. Migrants from rural to urban areas were in high-risk groups for the occurrence of TB drug resistance. CONCLUSION: In our study, prevalence of MDR was less than the global average. It is essential to monitor the patients with previous history of TB treatment and migrants by rapid and accurate techniques in terms of drug-resistance odds.

Molecular Epidemiology of Mycobacterium Tuberculosis Strains in the North-West and West of Iran.

BACKGROUND: Identifying Mycobacterium tuberculosis (MTB) transmission type is a key step in the control of this disease. AIM: This study aimed to determine the path and transmission type of MTB and the insertion sequence IS6110 band number and verify their relationship to demographic and clinical risk factors. SUBJECTS AND METHODS: In this cross-sectional study, 64 MTB patients from three border provinces of Iran were selected after full clinical history and physical evaluation design. The drug susceptibility testing was carried out using the standard proportion technique on sputum samples. Isolates tested with restriction fragment length polymorphism technique used IS6110. RESULTS: Recent transmission of disease was 33/50 (66%) based on clustering rate. The IS6110 band number had a significant relationship with drug resistance detected in proportion method tested by univariate linear regression (P < 0.01). Furthermore, the IS6110 band number had association with Bacillus Calmette-Guérin vaccination history (P = 0.02), sex (P < 0.01), and purified protein derivative (PPD) reaction size (P < 0.01) tested by multiple analysis. The risk of recent transmission inferred from the clustering rate was significantly higher in patients from Western provinces compared to those from the North-West province (P = 0.048). However, age (P = 0.39), gender (P = 0.16), vaccination history (P = 0.57), drug susceptibility, and PPD (P < 0.6) were independent of clustering. The largest cluster of up to six subjects was found in the Western provinces. CONCLUSION: Recent MTB transmission was much more common in the West compared to the North-West of Iran. Large MTB clusters with strong epidemiological links may be reflective of a disease outbreak. Correlation noted between the IS6110 band number and vaccination history; PPD size and female gender necessitates further studies.