Ocular infections caused by non-tuberculous mycobacteria: update on epidemiology and management

Abstract

Background: To provide an update on the frequency, distribution, risk factors and in vitro susceptibility of ocular infections caused by non-tuberculous mycobacteria.

Design: Retrospective study of university clinic patients.

Participants: One hundred thirty-nine patients with culture confirmed non-tuberculous mycobacteria infections seen at Bascom Palmer Eye Institute from January 1980 to July 2007.

Methods: Chart review of data collected included patients' demographics, risk factors, microbiological profiles and clinical outcomes.

Main outcome measures: Frequency, distribution, risk factors and in vitro susceptibility of ocular infections caused by non-tuberculous mycobacteria.

Results: A total of 183 non-tuberculous mycobacteria isolates from 142 eyes were identified, with a fourfold increase in the number of eyes infected with non-tuberculous mycobacteria from 1980-1989 (13.4%) to 2000-2007 (56.3%). Eighty-three percent of non-tuberculous mycobacteria isolates were identified as M. abscessus/chelonae. The majority (91%) of isolates were recovered within 10 days. Common diagnoses included keratitis (36.6%), scleral buckle infections (14.8%) and socket/implant infections (14.8%). Identifiable risk factors were presence of biomaterials (63.1%), ocular surgery (24.1%) and steroid exposure (77%). The median time from diagnosis of culture positive non-tuberculous mycobacteria infection to resolution was 13 to 24 weeks. Combination therapy was used to treat 80% of infected eyes. In vitro susceptibility of non-tuberculous mycobacteria isolates were: amikacin, 81%; clarithromycin, 93%; and moxifloxacin, 21%.

Conclusions: The incidence of ocular infections caused by non-tuberculous mycobacteria has increased within the last 8 years, with a high number of biomaterial associated infections among this group. Clinical diagnosis and microbiological confirmation of non-tuberculous mycobacteria infections remains challenging. Patient outcomes may be improved by early diagnosis, appropriate therapy and removal of biomaterials.