Role of fluorescence in situ hybridization in detecting mycobacterium avium complex presenting as fever in treatment failure HIV

Abstract

A 49-year-old male HIV positive patient on treatment failure presented with complaints of fever and dysphagia of three weeks duration and later on developed cervical lymphadenopathy along with severe vomiting and abdominal pain. Liver function tests were found to be worsening with severe drop in CD4 counts. An extensive workup for pyrexia was done. FNAC and biopsy of lymph node showed features suggestive of granulomatous lymphadenitis. CBNAAT of the lymph node aspirate was negative for MTB. Blood culture and lymph node cultures were negative for Mycobacterium Avium Complex (MAC). MAC was however, finally detected and reported positive on Fluorescence in Situ Hybridization (FISH) of the cervical lymph node aspirate. Prompt treatment for MAC was initiated with Ethambutol 800 mg OD and Azithromycin 500 mg OD following which fever spikes subsided and lymph node resolved. The Patient’s condition gradually improved and was discharged shortly with a good recovery on subsequent follow ups. Fever is one of the common symptoms in patients with MAC infection. Some other clinical manifestations include weight loss, hepatosplenomegaly and intra-abdominal lymphadenopathy. Diagnostic evaluation should be aggressive. As there is a high risk for MAC infection in advanced HIV cases with poor HAART compliance, FISH can be a valuable and effective diagnostic tool in early detection and treatment of MAC.

Fluorescence In Situ Hybridization (FISH) Tests for Identifying Protozoan and Bacterial Pathogens in Infectious Diseases

“…They can complement AFS microscopy and NAA methods to detect and differentiate MTBC from MAC and other NTM in sputum and cultures. FISH is also useful in detecting MTB and MAC in biopsied tissues [30]. Table in Section 5 below compares NAA and FISH tests for tuberculosis.…”

“…A simple and rapid test for directly identifying MTB and NTM in sputum and tissues that can be used by resource-limited laboratories in endemic countries is therefore expected to greatly aid tuberculosis control worldwide [92,93]. Two dual color FISH tests, with simple protocols (Figure S2), and requiring only a LED fluorescence microscope (Figure S1), meet this need [28][29][30]. The MN Genus-MTBC FISH test used an orange fluorescent DNA probe that specifically hybridizes to the 23S rRNA of the Mycobacterium tuberculosis complex (MTBC) and a green fluorescent probe specific for the Mycobacterium and Nocardia genera (MN Genus) 16S rRNA to detect and distinguish MTBC from other mycobacteria and Nocardia species.…”

“…The MN Genus-MTBC FISH test used an orange fluorescent DNA probe that specifically hybridizes to the 23S rRNA of the Mycobacterium tuberculosis complex (MTBC) and a green fluorescent probe specific for the Mycobacterium and Nocardia genera (MN Genus) 16S rRNA to detect and distinguish MTBC from other mycobacteria and Nocardia species. A complementary MTBC-MAC FISH test used green and orange fluorescent probes for 23S rRNA that respectively differentiate MTBC and MAC [28][29][30].…”

“…The MN Genus-MTBC and MTBC-MAC FISH tests on the other hand, cost < US$5 per test, provide results in <2 h after sputum collection, do not require enzyme treatment and centrifugation, can use LED fluorescence microscopy (Figure S1), and utilize reagents that are stable at ambient temperature [29]. They are used in India [30]. All FISH assays have the advantage that they are unaffected by inhibitors in respiratory samples which reduce sensitivity and require elaborate controls for NAA tests [96,97].…”

“…Infections with MAC are common in late-stage human immunodeficiency virus infections, where the mycobacteria are often restricted to lymphoid tissue. FISH provides a sensitive and specific method for detecting MAC by in biopsied tissues, which is important because the management and treatment of patients with MTBC and NTM infections are different [30]. Norcardiosis, caused by related Norcadia species widely distributed in the environment, also needs to be differentiated from MTB during lung infections [88].…”