Molecular epidemiology of Mycobacterium tuberculosis in adult Filipino TB-HIV co-infected patients.

BACKGROUND: TB is the leading cause of death from a single infectious disease, particularly among people living with HIV (PLHIV). Molecular epidemiology provides information on prevalent genotypes of Mycobacterium tuberculosis and disease transmission dynamics, which aid in TB control. Identification of mutations that confer drug resistance is essential for the rapid diagnosis of drug-resistant TB, especially in high TB burden settings, like the Philippines.METHODS: This study aimed to determine mutations in M. tuberculosis drug resistance-conferring genes and circulating genotypes in PLHIV. MIRU-VNTR (mycobacterial interspersed repetitive unit-variable number of tandem repeats) typing using a set of 24-loci and sequencing of drug resistance-conferring genes were performed in 22 M. tuberculosis isolates from TB-HIV co-infected patients.RESULTS: The prevalence of resistance to any drug was 31.8%, 18.2% for isoniazid monoresistance, 4.5% for streptomycin monoresistance and 9.1% for multidrug resistance. The identified mutations in the katG, rpoB, pncA, rpsL and gyrA genes have been reported in the literature; none was found in the inhA and embB genes. All isolates belonged to the EAI2-Manila family and were grouped into four clusters based on their phenotypic drug resistance and mutation profiles.CONCLUSION: The use of 24-loci set may be used as a more discriminatory MIRU-VNTR typing in settings where the East African-Indian lineage is predominant, like the Philippines.

MPB64 mycobacterial antigen: a new skin-test reagent through patch method for rapid diagnosis of active tuberculosis.

SETTING: A collaborative study between the Japan BCG Laboratory, Tokyo, Japan, and the Infectious Disease Section, Philippine General Hospital, Manila, the Philippines. Tuberculosis patients from four clinics in the vicinity of Manila, Our Lady of Grace Parish, Sto. Niño de Tondo Parish, the Canossa Health and Social Center, and the Health Care Development Center, were examined. OBJECTIVE: To develop a new, simple and rapid diagnostic method for active tuberculosis. Subjects were tested for skin reaction to a special antigen, MPB64, by the patch test method instead of intradermal injection of purified protein derivative (PPD). DESIGN: Fifty-three active tuberculosis patients and 43 healthy PPD-positive controls were tested to determine whether or not the reaction to MPB64 was positive only in active tuberculosis patients. RESULTS: Fifty-two of the 53 active tuberculosis patients showed a positive reaction to MPB64, while none of the 43 PPD-positive controls did. The specificity of MPB64 to active tuberculosis was 100%, and the sensitivity was 98.1%. The efficacy of the test was 98.9%. CONCLUSION: The patch test with MPB64 is a promising method for the diagnosis of active tuberculosis, distinguishing tuberculous patients from those who are infected but have not developed the disease, and also from BCG-vaccinated individuals. This new skin test is a subject for further evaluation and it is important to compare the results with PPD Mantoux.

Nature of drug resistance and predictors of multidrug-resistant tuberculosis among patients seen at the Philippine General Hospital, Manila, Philippines.

SETTING: This study was conducted at the University of the Philippines--Philippine General Hospital (UP-PGH), Manila, Philippines. OBJECTIVES: To determine the nature of drug resistance among patients with pulmonary tuberculosis (PTB), and to establish clinical predictors of drug-resistant tuberculosis. DESIGN: Descriptive, prospective study. METHODS: Patients with positive culture for Mycobacterium tuberculosis were interviewed regarding past history of anti-tuberculosis treatment, BCG vaccination, chest X-ray and family contact. M. tuberculosis isolates from 299 patients were tested for susceptibility to rifampicin, isoniazid (INH), ethambutol and streptomycin using the submerged disc proportion method. Pyrazinamide (PZA) susceptibility test was done with standard laboratory powder in 7H10 media. RESULTS: Of the 299 M. tuberculosis isolates, 17% were fully susceptible to the 5 primary drugs and 54% were resistant to 2 or more drugs (multidrug resistant TB [MDR-TB]). Initial drug resistance rate was high with ethambutol (39%) and INH (17%). Previous history of anti-tuberculosis treatment was significantly associated with MDR-TB (Odds Ratio [OR] 2.44, 95% confidence interval). Incomplete anti-TB treatment taken for longer than 3 months increased the likelihood of MDR-TB (OR 4.6, P < 0.0001). CONCLUSION: The high rate of MDR-TB was associated with previous anti-tuberculosis treatment. The chance of developing MDR-TB was significantly increased when inadequate prior treatment was given for more than 3 months.

Evaluation of a rapid assay for identification of Mycobacterium tuberculosis grown in solid and liquid media.

An MPT64 antigen detection assay, the SD Bioline TB Ag MPT64 Rapid kit, was evaluated for the identification of Mycobacterium tuberculosis grown in both solid and liquid media. The rapid test showed positive results in 132 of 133 (99.2%) M. tuberculosis cultures grown on Ogawa medium and 136/143 (95.1%) cultures grown in liquid culture medium, resulting in an overall sensitivity of 97.1%. All 18 non-tuberculous mycobacteria were found to be negative by the rapid test, indicating a specificity of 100%. The rapid test seems useful for the initial confirmation of M. tuberculosis in acidfast bacilli positive cultures.

Detection of active tuberculosis by an MPB-64 transdermal patch: a field study.

The mycobacterial antigen MPB-64 was formulated for delivery in a transdermal patch and used as a diagnostic skin test reagent to detect active tuberculosis (TB) in patients attending a clinic in Manila, The Philippines. The MPB-64 Transdermal Patch was applied to 62 patients, 49 with sputum-positive active disease and 13 who had completed TB chemotherapy, and to 28 non-TB but tuberculin-positive controls. The results were read at 72 h. The sensitivity of the Transdermal Patch was 87.8%, with an efficacy of 92.9% and a specificity of 100%. The 13 TB patients who had completed 6 months of TB chemotherapy showed different reactions to the MPB64 patch test: those who had completed chemotherapy < 4 months before testing were positive; 50% of patients who completed chemotherapy 5 months previously were positive; and those who had completed chemotherapy 7 and 8 months before were negative. All the non-TB controls with positive tuberculin tests were negative to the MPB-64 Transdermal Patch, even at the highest protein dose tested. This test may be a useful method to distinguish active TB patients from TB-infected but asymptomatic individuals. Moreover, the MPB64 Transdermal Patch may be useful to monitor successful chemotherapy.