A 42-year-old male with a history significant for chronic obstructive pulmonary disease (COPD), asthma, polyneuropathy, 1/2-pack-per-day smoker for 30 years was admitted to hospital for non-resolving cough and left-sided chest pain in November 2016. One month prior to this admission, he was in the Emergency Department and was treated with a 5-day course of azithromycin for a presumed, left upper lobe pneumonia. Seeing no significant relief of his symptoms, he went to his primary care provider and was prescribed a 10-day course of levofloxacin. The patient reported good adherence to and completion of both courses of antibiotic. Despite these two courses of treatment, respiratory symptoms persisted, which led to hospitalization and further diagnostic work-up.
At the time of hospital admission, the patient was afebrile, had a blood pressure of 113/77 mm Hg, heart rate of 96 beats per minute, respiratory rate of 16 breaths per minute, and a body mass index of 17.5 kg/m2. Physical exam revealed anterior cervical lymphadenopathy and coarse rhonchi in left upper zone anteriorly. Initial laboratory examination revealed the following: white blood cell count, 11.4 x 103 cells/microL; neutrophils, 78.4%; red blood cell count, 4.08 x 103 cells/microL; hemoglobin, 12.2 g/dL; hematocrit, 37.0%; platelets, 570 x 103 cells/microL; sodium, 140 mEq/L; potassium, 4.5 mEq/L; chloride, 104 mEq/L; CO2, 28 mmol/L; anion gap, 8 mEq/L; blood urea nitrogen (BUN), 20 mg/dL; creatinine, 0.87 mg/dL; glomerular filtration rate (GFR) > 60 mL/min; magnesium, 2.2 mEq/L; aspartate aminotransferase (AST), 14 units/L; alanine aminotransferase (ALT), 25 units/L; albumin, 3.4 g/dL; and troponin < 0.01 ng/mL. Chest X-ray showed left upper lobe consolidation, and a computed tomography (CT) of chest showed dense consolidation and cavitation in the left upper lobe along with advanced COPD changes in his lungs (Figure 1).
The patient was admitted to the medical service for non-resolving pneumonia. Given his symptoms, there was high suspicion of mycobacterial lung infection. He was placed in a negative pressure isolation room and work-up was started. Sputum for Gram stain and acid-fast bacilli (AFB) stain and culture were obtained, and purified protein derivative (PPD) test was placed. Three separate sputum samples were sent for AFB stain and culture based on our laboratory protocol, which includes a digestion-decontamination method using N-acetyl-l-cysteine-sodium hydroxide and cultivation with Lowenstein Jensen Medium and BACTEC MGIT 960 system (Becton Dickinson, MA, USA). Human immunodeficiency virus (HIV) screening was also ordered to assess for a possible source of immunosuppression which could pre-dispose the patient to NTM infection. The PPD, HIV test, and routine sputum cultures were negative; however, two out of three acid-fast smears came back positive with a semi-quantitative result of +1 AFB, reflective of 1-9 organisms per high powered field. Due to the long turnaround time for mycobacterial organism identification and susceptibility determination, the patient was started empirically on a four-drug treatment regimen of isoniazid, rifampin, ethambutol and pyrazinamide.
The patient's condition slowly improved, though he remained symptomatic throughout his hospitalization. Initially, he experienced some nausea and vomiting associated with the antimycobacterial drugs; however, this improved with modification of the timing of his doses relative to meals. Once the patient was tolerating his medications, plans were made to discharge the patient. Coordination with the local health department helped facilitate the discharge to home, with instructions for staying at home and avoiding close contact with others for at least the first month of therapy. The discharge medication regimen included ethambutol 1200 mg oral daily, isoniazid 300 mg oral daily at bedtime, pyrazinamide 1500 mg oral daily at bedtime, pyridoxine 50 mg oral daily at bedtime and rifampin 600 mg oral daily at bedtime.
The AFB isolate was later identified as M. szulgai, using MALDI-TOF mass spectrometry analysis. Real-time polymerase chain reaction (PCR) was negative for M. tuberculosis complex DNA and MAC DNA . The species were discriminated using MALDI-TOF mass spectrometry analysis as M. szulgai. Specimens were later submitted to reference lab at National Jewish Health, Denver, CO, USA for drug susceptibility testing. Reference lab performed agar proportion antimicrobial susceptibility testing methodology using Middlebrook 7H11 agar. As there are no standard treatment regimens for this organism, he was continued on the four-drug regimen for 2 months of treatment, during which he showed progressive clinical improvement. Based on the susceptibility test results, the regimen was streamlined accordingly to rifampin, isoniazid and azithromycin after 2 months of standard anti-tubercular therapy. His sputum culture was negative for AFB within 2 months of therapy initiation and remained negative for throughout his treatment course. A repeat CT was done, which showed complete resolution of left lung consolidation with remnant scarring (Figure 2). Treatment was stopped after 10 total months of therapy. He was closely followed up and had surveillance sputum cultures which remained negative. Given the persistent scar, he had a positron emission tomography (PET) scan which showed increased uptake in left upper lobe, which could be reflective of either malignancy or mycobacterial infection. Given the patient's history of cigarette smoking and concern for associated neoplasm, he was advised to undergo wedge resection, which was done 6 months after the completion of therapy. Pathology revealed old granulomas, and AFB culture of the resected tissue was negative. No evidence of malignancy was identified. The patient's clinical symptoms had resolved prior to the surgery and remained stable after the resection.