Molecular Epidemiologic Analysis of Mycobacterium tuberculosis among Prison Inmates in Selected Prisons in the Philippines

Abstract

Tuberculosis (TB) remains an important public health problem in developing countries like the Philippines. The success of the National TB Control Program depends on a clear understanding of the dynamics of transmission and spread of TB in high-risk populations in the community. We conducted a molecular epidemiologic analysis of M tuberculosis isolates collected from inmates with pulmonary TB in selected prisons in the Philippines. A total of 25 isolates were characterized and genotyped using Spoligotyping and 15-loci MIRU-VNTR (mycobacterial interspersed repetitive units–variable number of tandem repeats) typing. The majority of the patients were male (84%) and aged 30–49 yr old (68%). Eighteen (72%) of the culture-positive patients had severe pulmonary TB, 13 (52%) were smear-positive, and seven (28%) were classified as having a high bacillary load. Twenty isolates (80%) were susceptible to all the first-line drugs. Two (8%) were multidrug- resistant (MDR) and isolated from patients in the same prison, one of which was resistant to all first-line drugs. Three isolates (12%) were streptomycin-monoresistant. There were nine identified Spoligo-International Types (SITs), with SIT19 as the predominant (40%). One isolate (4%) did not match any SIT in the SpoIDB4 database, while three were not assessed due to inadequate DNA for analysis. The distribution of strains according to major M tuberculosis clades were as follows: EAI2_Manilla (48%) > LAM2 (20%) > LAM6 (8%) = LAM9 (8%). Spoligotyping identified two clusters and 13 genotypes (four unique strains) with a Hunter-Gaston discriminatory index (HGDI) of 0.83. MIRU-VNTR typing identified two clusters and 23 genotypes (HGDI = 0.993). Combined Spoligotyping and MIRU-VNTR typing also identified two clusters and 23 genotypes (HGDI = 0.993). There were no significant associations shown among host demographic factors, severity of the disease, drug resistance, and M tuberculosis strain. We conclude that our patient population was infected predominantly by M tuberculosis belonging to the EAI2_Manila clade