A 23-year-old polymyositis patient with suggestive clinical symptoms, muscle biopsy, enzyme assay, needle EMG and NCV test was on immunosuppressive drugs such as corticosteroids at 1 mg/kg/day for 3 to 4 weeks, tapered gradually over a period of 10 weeks to 1 mg/kg every alternate days and methotrexate at 7.5 mg weekly with gradual increase to 25 mg weekly for a period of 1 year when he experienced slightly improved muscle power.
He had single cutaneous abscess 6 months later on the right side of the neck with no sinus formation and cervical and axillary lymphadenopathy. He was HIV-negative with normal CXR and there was no AFB in three consecutive (spot-early morning-spot) sputum samples (induced in two occasions). However, the aspirated pus from cutaneous abscess and biopsy of the axillary lymph node showed plenty of M. tuberculosis as culture was confirmed by niacin and nitrate reduction tests, rapid bacteriophage assay (FAST Plaque Tuberculosis kit, BIOTEC Laboratories Ltd, UK) and RFLP analysis (figure 1) using species-specific probes for devR (Differentially expressed virulent gene).
In RFLP analysis, the devR gene (Gene bank nucleotide sequence accession no. U22037) encodes a response regulator that is part of a two-component signal transduction system of M. tuberculosis. The authenticity of the amplified product was established by hybridization of immobilized PCR products to an internal oligonucleotide, devR1, mapping within the devR gene. The chromosomal DNA was prepared by chloroform-isoamyl alcohol DNA extraction and 4.5 mug of DNA from the isolate was restricted with PvuII. Separation of PvuII-restricted DNA by electrophoresis, Southern blot hybridization with a 513-bp PCR probes for devR (devRf, 5' GGTGAGGCGGGTTCGGTCGC 3'; devRr, 5' CGCGGCTTGCGTCCGACGTTC 3') and chemiluminescence detection were done according to the standard method recommended for the DNA fingerprinting of M. tuberculosis . Histopathologically there were nonspecific necrosis with disintegrating polymorphs, very few granulomatous cells and no epithelioid cells in the biopsy specimen. USG of kidney, liver or spleen revealed no abscess. The strain was susceptible to the 4 first line drugs [isoniazide (H), rifampicin (R), ethambutol (E) and pyrazinamide (Z)] by BACTEC 460TB system. Treatment with 4-drug regimen (H = 300 mg/d, R = 450 mg/d, E = 800 mg/d and Z = 1.5 g/d) for 8 months (2EHRZ/6HR) with first 2 months supervised showed clinical improvement.
However, the patient returned 6 months later with multiple cutaneous abscesses, mainly on his back, left thigh and left arm and miliary mottling in CXR. He denied any irregularity in antituberculosis therapy. All immunosuppressive drugs (corticosteroids and methotrexate) were discontinued as he was readmitted. Isolates from 2 of 3 consecutive sputum samples and aspirated pus samples from all 5 completely drained abscesses were reconfirmed as the identical M. tuberculosis strain by phage assay and RFLP analysis (figure 1). The isolate was resistant to 4 first-line drugs by BACTEC 460TB system and to 9 drugs, tested into Loewenstein Jensen media (Hi-media, Mumbai, India): H (1 mug/ml), H (10 mug/ml), R (20 mug/ml), R (50 mug/ml), E (2 mug/ml), E (10 mug/ml), Z (50 mug/ml, at pH 5.5), streptomycin (5 mug/ml), streptomycin (50 mug/ml), paraaminosalicylate (2.5 mug/ml), cycloserine (30 mug/ml), amikacin (700 mug/ml) and ciprofloxacin (12.5 mug/ml). Treatment was continued with H (5 mg/kg/d), R (10 mg/kg/d), Z (30 mg/kg/d), E (15 mg/kg/d), kanamycin (15 mg/kg IM 5 times weekly) and sparfloxacin (500 mg/d) for 18 months with first 2 months under supervision. A slow but complete clinical, microbiological and radiological cure after 1.5 year was followed up for another 16 months.