Abstract / Summary
Haemophilus influenzae is an important cause of community-acquired pneumonia, particularly among older adults and individuals with underlying medical conditions.However, reports of H. influenzae pneumonia occurring within a short interval among elderly cohabiting couples with suspected household transmission are limited.Here we present two such cases.Case 1: A 95-year-old Japanese man presented with a three-day history of productive cough and hoarseness and developed a fever on the day of admission.He had hypoxemia and impaired consciousness.Chest computed tomography (CT) revealed infiltrative opacities, predominantly in the bilateral lower lobes.Haemophilus influenzae (H.influenzae) was isolated from sputum culture, and his condition improved after 11 days of treatment with ampicillin/sulbactam.Case 2: A 90-year-old Japanese woman, the wife of the patient in Case 1, developed a productive cough and exertional dyspnea around the time of her husband's admission.She received oral amoxicillin/clavulanic acid for five days as an outpatient without improvement, and was admitted 10 days after her husband.Chest CT showed multiple infiltrative opacities, predominantly in the right lung, along with diffuse bronchial wall thickening.Haemophilus influenzae was isolated from sputum culture, and her condition improved after 12 days of treatment with ceftriaxone.The H. influenzae isolates from the two patients exhibited identical minimum inhibitory concentration profiles for all antimicrobial agents tested.Although strain identity could not be confirmed because molecular epidemiological analyses were not performed, the close temporal relationship between the two illnesses, shared household exposure, and identical antimicrobial susceptibility profiles suggested the possibility of intrahousehold transmission but did not establish strain relatedness or confirm a transmission pathway.These cases provide clinically relevant insights into the possibility of household transmission of H. influenzae.