Interferon Gamma Release Assay (IGRA) friend or foe - Clinical application of IGRA in a tuberculosis endemic country

Abstract

Background: Rapidly growing mycobacteria (RGM) are environmental organisms that can cause post-operative wound infections. Infections typically occur after laparoscopic surgery due to inadequate sterilization of heat-sensitive instruments. We describe the clinical presentation and management of postoperative RGM infections at Christian Medical College (CMC), a large tertiary referral hospital in South India.Methods & Materials: Laboratory records from 1 st January 2012 to 31 st August 2015 were examined to identify patients with culture positive post-operative RGM infections. The electronic medical records of these patients were reviewed together with their haematological, histological and radiographic data.Results: Over this period, 32 patients were diagnosed with culture proven RGM infection as a consequence of surgery. Mycobacterium fortuitum was the commonest isolate (46.9%), followed by M. abscessus (31.2%) and M. chelonae (18.8%). Most patients had wound infections (96.9%); 78.1% extended into underlying muscle and 28.1% into structures deep to muscle. 37.5% patients had infection associated with prosthetic material including surgical mesh, pacemakers, cardiac valve and a neurosurgical shunt. Surprisingly, most patients (65.6%) had undergone open surgical rather than laparoscopic procedure (25%).Only 4 patients (12.5%) acquired RGM infection following surgery at CMC. Over this period, 96,713 operations were performed resulting in an infection rate of 0.004%. 87.5% patients underwent operation at a different hospital, presenting to CMC a median 4 months after operation. 43.8% received inappropriate treatment for wound infection before presenting to CMC. 37.5% received antibiotics and 9.4% empirical antitubercular therapy, highlighting poor knowledge about RGM infections.All patients were treated with surgical debridement; 75% received subsequent antibiotics consisting of a two or three drug combination of amikacin, levofloxacin/moxifloxacin, clarithromycin or linezolid. Patients jointly managed by surgeons and infectious disease physicians had a higher rate of clinical response (75%) with less loss to follow up (25%) than those managed exclusively by surgeons (43.8% and 57.25% respectively).Conclusion: RGM infections continue to complicate routine operations in India, although they are a rare complication of surgery in our hospital. They are under-recognised and frequently misdiagnosed resulting in delays in appropriate treatment. Higher clinical response rates are seen where management involves surgeons and infectious disease clinicians with laboratory support from microbiologists.