Molecular detection and characterization of resistant genes in Mycobacterium tuberculosis complex from DNA isolated from tuberculosis patients in the Eastern Cape province South Africa

Background: Tuberculosis (TB) in both animals and humans is caused by Mycobacterium tuberculosis complex (MTBC) primarily transmitted by inhalation of aerosolized droplets containing the organism. Multi-drug resistance (MDR) and extensive drug resistance (XDR) are evolutionary features of Mycobacterium tuberculosis to subvert the antibiotic regimes in place. The heavy burden of TB worsened by HIV endemic in South Africa motivated for the investigation of MTBC prevalence among TB patients in Port Elizabeth and the amplification and sequencing of the DNA amplicons known to confer resistance to TB drugs. Methods: Three thousand eight hundred and ten (3810) sputum specimens were processed and DNA was isolated from sputum specimens collected from different hospitals and health care places in the Eastern Cape Province, South Africa. DNA was amplified using the Seeplex^® MTB Nested ACE detection assay. The agar-dilution proportion method was used to perform drug-sensitivity testing using 7H10 Middlebrook medium. Target genes known to confer resistance to first and second-line drugs were amplified and the amplicons sequenced. Results: One hundred and ninety (5%) DNA samples tested positive for MTBC and from the resistant profiles of the 190 positive samples, we noted that multidrug-resistant TB was identified in 189 (99.5%) with 190 (100%) patients infected with MTB resistant to isoniazid and 189 (99.5%) having MTB resistant to rifampicin. Other percentages of drug resistance observed including 40% pre-XDR and 60% of XDR. Conclusion: This study provides valuable data on the different kinds of mutations occurring at various target loci in resistant MTBC strains isolated from samples obtained from the Eastern Cape Province. The results obtained reveal a high incidence of MDR amongst the positive samples from Eastern Cape Province, South Africa.