What is the diagnosis and treatment of Nocardiosis (Nocardia infection) of the lung?

From the Guidelines

Nocardiosis of the lung should be treated with long-term antibiotic therapy, typically for 6-12 months, with trimethoprim-sulfamethoxazole (TMP-SMX) as the recommended first-line treatment, given orally or intravenously depending on severity, as supported by the most recent and highest quality study 1. The diagnosis of Nocardia infection is based on clinical, radiographic, and bacteriologic criteria, including positive culture results from at least two separate expectorated sputum samples or one bronchial wash or lavage, and transbronchial or other lung biopsy with mycobacterial histopathologic features, as outlined in the guidelines 1. For adults, the typical dosage of TMP-SMX is:

• TMP-SMX 15-20 mg/kg/day (based on trimethoprim component), divided into 2-4 doses daily For severe infections or immunocompromised patients, combination therapy may be used:
• TMP-SMX plus amikacin (7.5 mg/kg every 12 hours) or imipenem (500 mg every 6 hours) Treatment duration:
• Immunocompetent patients: at least 6 months
• Immunocompromised patients: at least 12 months Close monitoring is essential, with follow-up chest imaging to assess treatment response, and surgical intervention may be necessary for large abscesses or empyema, as recommended by the guidelines 1. The sulfonamide component of TMP-SMX is particularly effective against Nocardia due to its ability to interfere with the organism's folate synthesis pathway, and the extended treatment duration helps prevent relapse and ensures complete eradication of the infection, as supported by the study 1. Key points to consider in the treatment of Nocardia infection include:
• The importance of long-term antibiotic therapy to prevent relapse and ensure complete eradication of the infection
• The need for close monitoring and follow-up chest imaging to assess treatment response
• The potential need for surgical intervention in cases of large abscesses or empyema
• The importance of considering the patient's immune status and underlying health conditions when determining treatment duration and intensity, as recommended by the guidelines 1.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Diagnosis of Nocardiosis

• Nocardiosis is a rare infection that is often difficult to treat and may be life-threatening 2
• The reference standard for Nocardia species identification is molecular biology, and the preferred method for antibiotic susceptibility testing (AST) is broth microdilution 2
• Diagnosis can be difficult, as the organism takes time to grow in culture, but molecular techniques and histology can aid in diagnosis 3
• Pulmonary nocardiosis can mimic tuberculosis, fungal infections, or malignancies, making diagnosis challenging 3

Treatment of Nocardiosis

• Trimethoprim-sulfamethoxazole is the preferred agent for initial therapy, because Nocardia is very often susceptible to this agent 2
• Linezolid, to which Nocardia is almost always susceptible, may be an alternative 2
• When combination therapy is required, the repertoire of companion drugs includes third-generation cephalosporins, amikacin and imipenem 2
• Tedizolid, a bacteriostatic oxazolidine antibiotic, may be a promising alternative to linezolid in cases of nocardiosis that usually require long-term treatment 4
• The median duration of treatment was 24.2 weeks, and the overall one-year case fatality was 33.3% 5
• Selected antimicrobial agents were generally effective, with linezolid and cotrimoxazole (100% Susceptibility) and amikacin (94% Susceptibility) having the most activity against Nocardia species 5
• Treatment of actinomycosis is usually simple, requiring long-term, high-dose intravenous penicillin, while pulmonary nocardiosis requires sulfonamides as first-line agents, with carbapenems as an alternative for severely ill patients 6

Treatment Duration and Outcome

• Treatment duration of 6 months is appropriate for most situations, but longer durations are preferred for disseminated nocardiosis and shorter durations are reasonable in low-risk situations 2
• The overall one-year case fatality was 33.3%, and was higher in disseminated nocardiosis (66.7%) 5
• No recurrence was observed in patients treated with antibiotics 5