Abstract
Purpose :
Members of the Mycobacterium abscessus complex (MABC) have emerged as the leading cause of nontuberculous mycobacterial ocular infections in the last 5 years. Currently the complex is divided into three subspecies M. abscessus (Mabs), M. massiliense Mmas) and M. bolletti (Mbol). Our purpose was to determine the diversity, distribution and prevalence of macrolide and amikacin resistance among recently recovered MABC isolates. We hypothesize that subspecies frequency and emerging antibiotic resistance are niche specific.
Methods :
Twenty-two archived isolates recovered from patients with confirmed MABC infections- M. abscessus complex (n=15), M. abscessus (n=5), M. massiliense (n=1) and M. bollettii (n=1) were included in the study. A multiplex PCR assay was developed to identify, confirm, and compared previously reported MABC subspecies. We screened for the presence of mutations in the ERM41 gene to confirm intrinsic, nonfunctional and or inducible macrolide resistance for a subset of these isolates (n=9) using PCR and sequencing.
Results :
MABC isolates were most often recovered from the cornea 63.6% (n=14), biomaterials 22.7% (n=5, socket (2), 1 each IOL, stents, CTL), lacrimal system 9.1% (n=2) and lids 4.5% (n=1). MABC subspecies distribution included Mabs 50% (n=11), Mmas 45.5% (n=10) and Mbol 4.5% (n=1). Mmas constituted 50% (7/14) of the cornea isolates. Clarithromycin and amikacin resistance was 27.2% (6/22) and 18.2% (4/22). Macrolide resistance was highest among Mabs 36.4% (n=4/11) vs 10% (n=1/10) for Mmas. All Mabs isolates were susceptible to amikacin vs 40% (n=4/10) among Mmas isolates. Both amikacin and clarithromycin resistance were more likely to be associated with cornea isolates. Four of 9 ERM41 gene (44.4%) harbored the wild type T28 resistance mutation confirming intrinsic and inducible resistance for Mabs (3) and the Mbol (1); 2 (22%) Mabs strains had the C28 mutation confirming default macrolide susceptibility. A nonfunctional gene was present in 3 Mmas isolates.
Conclusions :
M abscessus and M. massiliense were commonly detected MABC subspecies but differed by niche and susceptibility profiles. Greater than 15% nonsusceptibility for the two main lines drugs are of concern. These results support our data and have implications for patient therapy.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.