INTRODUCTION
Nocardiosis is caused by a group of gram-positive aerobic actinomycetes with microscopic appearance as filamentous bacterium with hyphae-like branching filaments. Inhalation of airborne spores or mycelial fragments from environmental sources is the main route of transmission in humans.[1] Hence, the most common manifestation of the nocardial disease is pulmonary nocardiosis, usually occurring in immunocompromised patients. Here, we intend to report a case of pulmonary nocardiosis in an immunocompetent patient.
CASE REPORT
A 13-year-old male, with no comorbidities, presented with a history of fever, breathlessness, cough with streaky blood-tinged expectoration for the last 2 months. He had no chest pain, wheeze, loss of appetite, or loss of weight. His scholastic and social performance was above average and his mother denied any significant perinatal events. On examination, he was febrile, tachypneic, normotensive, and mildly hypoxic. General physical examination revealed right supraclavicular swelling measuring 3–4 cm, which was soft, mobile, and non-tender. A respiratory system examination revealed signs suggestive of consolidation in the right upper lobe. The rest of the systemic examination was normal.
His routine blood investigations revealed leukocytosis with neutrophilic predominance and non-reactivity for HIV. His chest radiograph revealed right upper zone consolidation [Figure 1]. Contrast-enhanced computed tomography (CECT) of the thorax showed [Figure 2a] necrotizing right upper lobe consolidation measuring 8.2(cc) × 5.4(t) × 7.5(ap), with heterogeneous peripheral post-contrast enhancement. Sputum for Gram staining revealed gram-positive cocci. Sputum examination for Ziehl–Neelson, KOH mount, Xpert MTB/RIF, liquid culture (BactAlert), and solid culture were negative. USG neck showed right cervical lymphadenopathy, the largest of which measured 3 × 4 cm. Fine needle aspiration cytology of the right cervical lymph node was suggestive of reactive lymphadenitis. Subsequently, CT-guided transthoracic lung biopsy was done, histopathological examination of which revealed neutrophilic inflammation with no evidence of malignancy or tuberculosis. Fiberoptic bronchoscopy was done which showed purulent discharge from the right upper lobe bronchus. Bronchoalveolar lavage (BAL) for Gram stain revealed typical gram-positive, dotted and striped, fine, right-angled, thin branching filaments fragmenting into bacillary or coccoid elements suggestive of Nocardia spp [Figure 3]. Culture on sheep blood agar showed a chalky texture and minute aerial hyphae. To enhance the acid-fast properties, colonies were inoculated in Middlebrook media where no opacification was seen. An antibiotic susceptibility test was performed for more precise identification. The organism was sensitive to cefotaxime but resistant to tobramycin and erythromycin which was suggestive of Nocardia asteroides complex. A contrast-enhanced scan of the brain was done to rule out evidence of intracranial nocardiosis which was normal. Serum immunoglobulins levels were done to rule out combined variable immunodeficiency which were normal [IgG (1204 mg/dL), IgA (298 mg/dL), and IgM (189 mg/dL)].
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Figure 1: Chest radiograph showed an inhomogeneous opacity with air bronchogram in the right UZ
Figure 2: CT scan on diagnosis showed a necrotizing right upper lobe consolidation measuring 8.2(cc) × 5.4(t) × 7.5(ap), with heterogeneous peripheral post-contrast enhancement
Figure 3: Gram-positive Nocardia spp on staining
The patient was started on tablet trimethoprim (160 mg) with sulfamethoxazole (800 mg) once a day and he showed gradual clinical improvement over 4 weeks of treatment followed by significant radiological improvement at 6 months [Figure 4]. The treatment was continued for 1 year with the advice to follow-up monthly. Currently, he is asymptomatic since the time of completion of treatment.
Figure 4: Chest radiograph at 6 months of completion of treatment
DISCUSSION
Nocardial infections can involve the lung, central nervous system (CNS), skin, and pericardium, with lung involvement being the most common (39%).[2,3] In immunocompetent individuals, Nocardia usually manifests with only cutaneous lesions which were absent in our case. It requires a high index of clinical suspicion to diagnose pulmonary nocardiosis because of its variable clinical and radiological presentation, especially if other systems are not involved. Pulmonary nocardiosis clinically presents itself with fever followed by a cough and breathlessness, unresponsive to broad-spectrum antibiotics and anti-tubercular drugs. CT findings in nocardiosis usually reveal pleiomorphic findings, with multifocal consolidation being the most common followed by nodular, cavitary and interstitial lesions.[4] Sputum specimen staining is usually diagnostic of nocardiosis in most reported cases closely followed by BAL examination. In one case series, 44% of pulmonary infections required an invasive procedure to establish the diagnosis of nocardiosis.[5] When an invasive procedure is performed, cultures are positive in 85–90% of the specimens.[6]
The initial presentation of our patient appeared highly suggestive of pulmonary and cervical lymph node tuberculosis. Since tuberculosis and nocardiosis have overlapping clinical and radiological findings and since tuberculosis is much more prevalent than nocardiosis, tuberculosis was the initial diagnosis. In the present case, tuberculosis was ruled out by negative microbiological and molecular testing of sputum and BAL. Our case had dense right upper lobe consolidation with no other abnormalities on imaging, transthoracic aspiration cytology of which was inconclusive. Molecular testing via 16s rRNA and hsp65 gene-specific primers is considered the investigation of choice for the identification of Nocardia species. However, the same could not be done in our case due to financial constraints. Instead, conventional culture on sheep blood agar was done which provided indirect identification of the species, i.e., Nocardia asteroides. Disseminated disease, defined by the involvement of more than one non-contiguous site, was also ruled out in the present case.
In most case series on pulmonary nocardiosis, the included patients either had an immunocompromised status or chronic lung conditions like Chronic Obstructive Pulmonary Disease (COPD) and bronchiectasis.[7] A literature search revealed two case reports of infections with Nocardia in adult immunocompetent patients.[8,9] Since Nocardia is not as common as other opportunistic infections and is a rarity in non-HIV CD4-deficient individuals, CD4 count was not evaluated in our patient.[10] However, our case is the first of its kind, who, apart from his apparent immunocompetent status with no pre-existing chronic lung disease, was from the adolescent age group.
The duration of treatment is a minimum of 6 months and should extend for at least 1 month after symptoms of infection have resolved. Close monitoring is essential for up to 1 year following cessation of antibiotics to detect relapse. First-line therapy includes sulfonamides, followed by amikacin, imipenem, cephalosporins, fluoroquinolones, and linezolid as second-line agents. Our patient was given trimethoprim and sulphamethoxazole for 12 months to prevent relapse. His response was favorable with no serious adverse effects.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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