Over 10% TB cases in AP show drug resistance: Study

Visakhapatnam: A recent study has found that 10.3% of nearly 5,700 confirmed tuberculosis (TB) cases in Andhra Pradesh showed resistance to at least one key anti-TB drug. This highlights the continuing threat posed by drug-resistant strains, even though the majority of infections remain treatable. The research revealed that 89.7% of cases were fully susceptible to first-line medications.In the study, researchers analysed 5,759 patient samples collected in 2024. Of these, 5,699 yielded valid results. Among the valid samples, 585 (10.26%) showed resistance to at least one anti-TB drug. The team used molecular diagnostic tests to assess resistance to isoniazid (INH) and rifampicin (RIF), the cornerstone drugs of first-line TB treatment. They also evaluated resistance to second-line medicines, including fluoroquinolones (FQs) and injectable agents such as kanamycin and amikacin, which are used when initial therapies fail. INH resistance was the most common and was detected in nearly 8% of patients. RIF resistance was less frequent and was observed in about 0.7% of cases.Of particular concern were 94 cases of multidrug-resistant TB (MDR-TB), defined as resistance to both INH and RIF. Within this group, 9 patients were identified as having pre-extensively drug-resistant TB (pre-XDR TB), showing additional resistance to fluoroquinolones, and two patients had drug-resistant TB (XDR TB), resistant to INH, RIF, fluoroquinolones, and at least one injectable drug. The remaining 83 MDR-TB cases retained susceptibility to second-line treatments, offering scope for effective clinical management.TB is an infectious disease that mainly affects the lungs and spreads through the air when someone with the illness coughs or sneezes. While TB can usually be treated with medicines, the rise of drug-resistant forms has become a serious challenge worldwide, including in India.The research was conducted by Gajjala Suvarna, Venkata Giri Prasad Polu, Kogila Sreeja Vamsi, Benson Wesly Buraga, Basireddy Sreekanth Reddy, Kota Neela Manikanta, Gundi Vijaya Ananda Kumar Babu, Gujjula Mary Sandeepa, Mugudalabetta Shiva Kumar, and Uday Sankar Allam. The researchers are affiliated with different institutions in Nellore and Mahabubnagar. The study was published in the IP International Journal of Medical Microbiology and Tropical Diseases.The study also examined the genetic mutations in TB bacteria responsible for drug resistance. INH resistance was mainly linked to the katG S315T1 mutation, while RIF resistance was commonly associated with the rpoB S531L mutation. Fluoroquinolone resistance was attributed to mutations in the gyrA gene, particularly at positions D94 and A90, and all pre-XDR and XDR cases exhibited these mutations. Resistance to injectable drugs was associated with mutations in the rrs gene and the eis promoter region, although these were less common.Patients with pre-XDR or XDR TB were predominantly men aged between 20 and 63 years and came from both rural and urban areas. Most had high bacterial loads, which can complicate treatment. The findings indicate that while most TB cases in Andhra Pradesh remain responsive to standard therapy, drug-resistant forms are an emerging concern. Widespread INH resistance may lead to treatment failure if not detected early. Although MDR-TB cases are relatively few, they are more complex and costly to treat. Pre-XDR and XDR TB, though rare, are the most severe forms, as treatment options are limited, more toxic, and often less effective.This retrospective study was conducted at a tertiary care centre in Nellore, a referral centre under the national TB elimination programme.