Nocardia cyriacigeorgica infection in a patient with pulmonary sequestration: A case report

Abstract

BACKGROUND

Nocardia cyriacigeorgica (N. cyriacigeorgica) infection is uncommon in clinical practice. Pulmonary sequestration complicated with N. cyriacigeorgica has not been reported in the literature. Here, we present a case of pulmonary se-questration complicated with N. cyriacigeorgica infection in an immunocom-petent woman.

CASE SUMMARY

A 37-year-old woman complaining of a recurrent cough was admitted to our hospital. Pulmonary sequestration in the lower lobe of the left lung was diagnosed by enhanced computed tomography. Bronchoalveolar lavage fluid was then collected, which showed gram positive bacilli with weakly positive modified acid-fast staining. The pathogen was identified as N. cyriacigeorgica after bacterial culture and mass spectrometry analysis. The patient was diagnosed with pulmonary sequestration complicated with N. cyriacigeorgica infection, and her symptoms quickly improved following anti-infective therapy.

CONCLUSION

Nocardiosis is considered to be an opportunistic infection. This is the first report of pulmonary sequestration complicated with N. cyriacigeorgica infection in a patient with normal immunity.

Key Words: Nocardia, Infection, Pulmonary sequestration, Nocardia cyriacigeorgica, Lung, Case report

Core Tip: Nocardia cyriacigeorgica (N. cyriacigeorgica) infection is uncommon in clinical practice. There are few reports of Nocardia infection in patients with pulmonary sequestration. We report an immunocompetent young woman who was diagnosed with pulmonary sequestration by enhanced computed tomography. Bronchoalveolar lavage was performed for further pathogenic examination, which revealed N. cyriacigeorgica infection in the lesion. This is the first case of pulmonary sequestration complicated with N. cyriacigeorgica infection reported in the literature.

INTRODUCTION

Nocardia is an opportunistic pathogen, which is frequently seen in immunosuppressed individuals[1-3]. More than 50 Nocardia species have been identified[1,4], including Nocardia asteroides, Nocardia brasiliensis, Nocardia farcinica, and Nocardia otitidiscaviarum, which are the main species causing disease in humans, and Nocardia cyriacigeorgica (N. cyriacigeorgica) is a relatively rare pathogen[5]. N. cyriacigeorgica infection has been reported in organ transplant recipients, long-term glucocorticoid users, and patients with several chronic pulmonary diseases[2,5-8]. There are few reports of Nocardia infection in patients with pulmonary sequestration. Here, we report a case of pul-monary sequestration complicated with N. cyriacigeorgica infection diagnosed in our hospital.

CASE PRESENTATION

Chief complaints

A 37-year-old woman was admitted to our hospital on September 15, 2020 due to recurrent cough for more than 10 mo.

History of present illness

The patient developed a paroxysmal cough accompanied by a small amount of white sputum 10 mo ago. She had no chills, fever, chest pain, hemoptysis, or shortness of breath. She received symptomatic treatment such as anti-infection at a local hospital but her symptoms persisted during this period. The above symptoms recurred 1 mo ago with a little yellow sputum. Fever and hemoptysis were absent. The patient was admitted to our hospital for further treatment.

Physical examination

The patient was thin and weighed only 40 kg (Body mass index: 15.6). Her temperature was 37.4 °C, pulse rate was 99 bpm, respiratory rate was 19 breaths/min, and blood pressure was 100/63 mmHg. No clubbing of fingers, icterus, or generalized lymphadenopathy were observed. Clinical examinations of the cardiovascular, gastrointestinal, and nervous systems were normal, but crackles were found in the lower lobe of the left lung during lung auscultation.

Laboratory examinations

Laboratory studies showed normal white blood cells (8.6 × 10⁹/L), and the neutrophil ratio was 83.0%. Erythrocyte sedimentation rate was 26 mm/h (normal value < 15 mm/h), and high-sensitivity C-reactive protein was 8.2 mg/L (normal value < 8.0 mg/L). Arterial partial pressure of oxygen was 91 mmHg (partial pressure of oxygen/fraction of inspiration O₂ 433.3 mmHg), and arterial partial pressure of carbon dioxide was 41 mmHg. The 1,3-β-D-glucan test and galactomannan test were both negative.

Imaging examinations

Enhanced computed tomography images revealed a honeycomb lesion in the lower lobe of the left lung, and an enhanced vascular shadow was seen in the descending aorta, which was consistent with pulmonary sequestration (Figure 1).

Figure 1 Computed tomography images. A: High-resolution computed tomography revealed bronchiectasis with honeycomb changes in the lower lobe of the left lung; B: Enhanced scan displayed a vessel from the descending aorta entering the lesion (orange arrow); C: Maximum intensity projection image showed an independent blood vessel originate from the descending aorta (orange arrow); D: Volume rendering image confirmed that the lesions were supplied by an independent vessel (orange arrow).

Further diagnostic work-up

We also performed bronchoscopic alveolar lavage in the posterior basal segment of the left lower lobe. Gram-positive bacilli were detected in the bronchoalveolar lavage fluid (BALF) (Figure 2). The modified acid-fast staining of BALF was weakly positive, and the possible presence of Nocardia species was considered. Following culture of BALF, N. cyriacigeorgica was identified (Figure 3), which was confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (matrix-assisted laser desorption/ ionization-time of flight; VITEK MS, bioMérieux, Craponne, France) (Supplementary Figure 1).

Figure 2 Bronchoalveolar lavage fluid examination. Gram-positive bacilli (black arrow) were found in bronchoalveolar lavage fluid (magnification × 1000).

Figure 3 Culture of Nocardiacyriacigeorgica. Colonies of Nocardia cyriacigeorgica grew on blood agar plates.

FINAL DIAGNOSIS

The patient was diagnosed with pulmonary sequestration in the lower lobe of the left lung complicated by N. cyriacigeorgica infection.

TREATMENT

She was started on treatment with trimethoprim-sulfamethoxazole (TMP-SMX) (4.32 g/d) and amikacin (0.4 g/d).

OUTCOME AND FOLLOW-UP

Her symptoms gradually improved, and she was discharged on September 25, 2020.

DISCUSSION

Nocardia is an aerobic, gram-positive, and modified acid-fast stain-positive bacillus that belongs in Actinomycetes. It is widely found in natural environments and frequently causes opportunistic infections in patients with impaired immunity, but one-third of infections can also be seen in patients with normal immunity[1]. N. cyriacigeorgica, an uncommon type of Nocardia, was first described in 2001, and was subsequently reported in Europe, Asia, and North America[9]. Microscopic examination revealed typical bacilli, and positive modified acid-fast staining was helpful for the diagnosis. The identification of Nocardia species by mass spectrometry after bacterial culture is the “gold standard” for determining different subtypes of Nocardia[8,10]. Sputum is the most commonly used respiratory tract specimen for Nocardia isolation[2,3,8,10], and BALF or fine needle aspiration biopsy is sometimes used as an invasive method to obtain specimens[3]. BALF has the advantages of simple operation and collection, the specimens are relatively less contaminated, and the results are relatively reliable. Percutaneous lung puncture biopsy is generally not the first choice for the risk of pneumothorax or bleeding. In our case, Nocardia was initially suspected when gram-positive bacilli were found in BALF smears. The pathogen was identified as N. cyriacigeorgica after bacterial culture and mass spectrometry analysis. Thus, the clinical evidence was conclusive.

Nocardia infection usually occurs due to exogenous inhalation or direct invasion through injured skin; therefore, the lungs and skin are the most common organs involved. Disseminated nocardiosis is frequently seen in immunocompromised patients[1,11], and mortality is high when the brain is involved[5]. In patients without cellular immune deficiency, the use of systemic glucocorticoids in chronic obstructive pulmonary disease is considered to cause pulmonary nocardiosis[1]. In addition to chronic obstructive pulmonary disease, there are reports in the literature that patients with structural lung diseases such as bronchiectasis, allergic bronchopulmonary aspergillosis, and nontuberculous mycobacterial pulmonary disease can also be complicated with N. cyriacigeorgica infection[2,8,12]. Pulmonary sequestration is a rare congenital pulmonary malformation where part of the lung tissue is directly supplied by the systemic circulation, which forms a cystic mass[13]. This part of the lung tissue is prone to recurrent localized infections[14]. Therefore, pulmonary sequestration is also a “special” structural lung disease. Kilpatrick et al[15] reported the first case of pulmonary sequestration complicated with Nocardia infection in 1976, but it was impossible to distinguish N. brasiliensis from N. asteroides due to technical limitations at that time. Shibli et al[16] and colleagues reported another case with N. asteroides infection and pulmonary sequestration in 2002. Foucrier et al[17] reported the imaging findings of another case of pulmonary sequestration with Nocardia infection (the article did not mention the type of Nocardia species). This is the first report of pulmonary sequestration complicated with N. cyriacigeorgica infection in a young immu-nocompetent woman.

Nocardiosis involves chronic suppurative inflammation, and TMP-SMX is the first choice for treatment. Critically ill patients often require combination therapy. The drugs that can be combined include aminoglycosides, carbapenems, quinolones, etc., and the course of treatment usually lasts more than 6 mo. Patients with central nervous system involvement may need a longer course of treatment[1]. The clinical symptoms in our patient were relatively mild and improved after treatment with TMP-SMX combined with amikacin. Pulmonary sequestration itself was considered to have surgical indications after thoracic surgery consultation. However, the patient was recommended to choose the timing of surgery after adequate anti-infective treatment due to the presence of N. cyriacigeorgica infection.

CONCLUSION

In summary, we report a case of pulmonary sequestration complicated by with N. cyriacigeorgica infection in an immunocompetent female patient. The pathogen was confirmed by BALF examination. In addition to common bacteria, rare pathogens such as Nocardia should be considered in patients with pulmonary sequestration.