Nocardia and actinomyces

Nocardia and Actinomyces species are gram-positive filamentous bacteria associated with a wide range of clinical infections in the immunocompromised host. Although relatively rare among pediatric solid organ transplant recipients, hematopoietic stem cell transplant recipients, and hematology/oncology patients overall, they present unique diagnostic and treatment challenges and can lead to significant morbidity and mortality. Nocardia are ubiquitous environmental pathogens most frequently associated with pulmonary disease with high rates of dissemination in the immunocompromised host. The central nervous system is particularly prone to secondary infection, with high mortality despite treatment. Although molecular testing is increasingly available, diagnosis is often delayed and is typically dependent on histopathology and culture. Trimethoprim-sulfamethoxazole remains the backbone of treatment for nocardiosis despite a wide range of antimicrobial resistance patterns. Combination therapy is recommended in severe infections and antimicrobial susceptibility testing is vital. Treatment is typically prolonged with limited data on the risk of recurrence or the role for secondary prophylaxis. Actinomyces are rare opportunistic gram-positive rods known for their tendency to cross tissue planes and cause soft tissue infections in both compromised and immunocompetent hosts. Infections typically present as cervicofacial, thoracic, or abdominal in nature and can manifest in various forms ranging from oropharyngeal ulcerations and abscesses to pulmonary consolidations and destructive soft tissue masses. Diagnosis is made by culture and histopathology, but may be delayed as Actinomyces can take up to 14 to 21 days to grow. Actinomyces are uniformly susceptible to penicillin as well as a number of other antimicrobial agents, and treatment is typically prolonged.