Diagnostic Challenges in Aspiration Pneumonia With Repeated Isolation of Rothia aeria: A Case Report

Rothia aeria (R. aeria) is a rare, facultatively aerobic Gram-positive bacillus in Actinomycetales. Although it is known as part of the normal oral flora, it has increasingly been reported as an opportunistic pathogen, particularly in immunocompromised patients. However, reports of respiratory infections due to R. aeria remain extremely rare. We report a case of an elderly woman with aspiration pneumonia in whom R. aeria was repeatedly isolated from sputum cultures. Branching Gram-positive bacilli were observed on Gram stain; however, these organisms were not found within neutrophils, suggesting a lack of active phagocytosis. The patient showed rapid clinical and radiological improvement following short-term treatment with meropenem. Post-treatment culture of bronchoalveolar lavage fluid was negative. Due to the minimal inflammatory response and lack of overt tissue destruction, the findings were interpreted as either transient colonization or mild infection. This case highlights the importance of comprehensive clinical judgment in evaluating the clinical significance of rare organisms isolated from non-sterile specimens rather than relying solely on culture results. Our case suggests that, even in relatively immunocompetent hosts, repeated detection of R. aeria in respiratory specimens warrants careful consideration of its pathogenic potential, particularly in the context of radiological changes and clinical response to treatment.