Track: Clinical Studies

Topic: Infectious Diseases

Abstract:

Definitively diagnosing leprosy is hindered by the inability to culture the causative mycobacteria (Mycobacterium leprae and lepromatosis). Molecular methods can provide rapid, species-level identification of these organisms. This study aimed to evaluate a nontuberculous mycobacteria multi-locus (hsp65, 16S rRNA, and rpoB) PCR assay followed by sequencing for detection of leprosy-associated mycobacteria. We analyzed positive clinical tests from 2009 to 2023 at a single large reference laboratory in the United States. We identified 108 positive samples from 100 patients submitted from 21 states. The mean age was 59 (range 15-91), and 65% were male. Most samples were formalin fixed and paraffin embedded (64 of 87 samples with status recorded). The upper (31.5%) and lower (18.5%) extremities were the most common anatomic locations. M. lepromatosis was identified in 9/108 (8%) samples representing 7 patients from across the US (including Pennsylvania, Florida, California, and Washington). One hundred samples had DNA sequences available; surprisingly, 59% of these samples were identified by a single target, 34% by two targets, and only 7% by all three targets. A positive PCR for the rpoB locus occurred in 83% of samples, followed by 16S (48%) and the nested hsp65 amplification (17%). The M. leprae sequences showed minimal variation; the dominant allele represented 99% of rpoB sequences, 100% of 16s rRNA, and 85% of hsp65. Overall, multi-locus PCR identified leprosy-associated mycobacteria, including a high proportion of M. lepromatosis, which is considered rare. Molecular assays should be considered on biopsies showing histiocytic inflammation in the right clinical context.

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Joshua Lieberman, MD, PhD