Case Report: Case 1 is a 33 y/o male who was incarcerated in Peru. During incarceration in 2008, 3 of his cellmates had MDR-TB and he was diagnosed with DS-TB and treated with directly observed therapy (DOT) for 7 months. In Texas in 2015 he was diagnosed with DS-TB and was initiated on rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE). Five months into DOT, his sputa became culture positive with molecular detection of drug resistance (MDDR) and drug susceptibility testing (DST) revealing resistance to all of RIPE. Repeat MDDR and DST of the 2015 isolate showed no resistance. Genotyping of the 2 isolates were identical by mycobacterial interspersed repetitive units (MIRU) and spoligotyping. However, whole genome sequencing showed 2 different isolates.
Case 2 is a 63 y/o female diagnosed with DS-TB in Saipan and started on RIPE in April 2017. She was on DOT until July when she moved to Texas and was lost to follow-up until September. She claims adherence with rifampin and isoniazid during this time. All sputa collected between diagnosis and September were smear and culture negative. Six months into therapy, she had sputa that was culture positive with MDDR and DST showing MDR-TB. Her isolates from Saipan and Texas were sent for genotyping. The MIRU and spoligotyping showed 2 different isolates.
Conclusion: These cases show the importance of following cultures throughout treatment. Traditionally, MDR-TB is thought to be due to poor adherence. However in high prevalence areas, heterogeneous infection with two different strains is an important consideration for the cause of MDR-TB. Concomitant infection of DS and MDR-TB can occur with MDR-TB not being detected until far into therapy. These cases represent heterogeneous exogenous infection of DS and MDR-TB - only discovered after meticulous culture monitoring.
Q. Kizilbash, None
A. Vasquez, None