Emerging threats: PreXDR and XDR-TB strains among MDR-TB cases in Romania.

Resistance to anti-tuberculosis drugs is an increasing challenge worldwide. Besides multi-drug-resistant tuberculosis (MDR TB) strains (resistant to at least Rifampicin and Isoniazid), additional resistances to new drugs have emerged worldwide: pre-extended-drug-resistant TB (preXDR TB - MDR TB plus resistance to a fluoroquinolone) and extended-drug-resistant TB (XDR TB - preXDR TB plus resistance to Bedaquiline or Linezolide). In this retrospective observational study, the MDR TB strains identified in our laboratory during 2023 were tested for resistance to Linezolid and Bedaquiline using liquid culture and drug susceptibility test (DST). We collected bacteriological assay data from the laboratory electronic registry, and demographic, clinical and treatment outcome data from the National TB Program database. A number of 164 patients were included: 126 had Rifampicin-resistant TB or MDR TB; 34 had pre-XDR TB, and 4 had XDR TB (3 with resistance to Linezolid and 1 to Linezolid and Bedaquiline) In the group, 81% of patients were male, median age was 48 years, and 60% had residence in rural area. As TB case category, 43% were new cases and 57% had at least one previous episode of TB treatment. There was a small percentage of HIV positive (8%) and intravenous drug users (4%). The mortality was high, 14% overall, and 23% in the cases with preXDR and XDR TB. Our data show that one in 10 patients with preXDR will also display resistance to Bedaquiline or Linezolide, enforcing the need for mandatory extended DST for every MDR TB patient. Our results could be used to add to the map of TB drug resistance in Eastern European region.