Late-onset afebrile neonatal bacteremia due to nontypeable Haemophilus influenzae: A case report

Haemophilus influenzae type b (Hib) vaccine has significantly reduced invasive Haemophilus influenzae disease (IHD) in Japan, but it has no effect on nontypeable Haemophilus influenzae (NTHi). IHD caused by NTHi remains a common issue among neonates. This report presents a case of neonatal late-onset bacteremia caused by NTHi without typical symptoms such as fever and elevated serum C-reactive protein (CRP) levels. A Japanese girl, born prematurely as the first twin, was hospitalized for lip cyanosis and a cough. Initial hematological and radiological investigations revealed no significant abnormalities except for hypocomplementemia. However, she experienced frequent apneic attacks with bradycardia and cyanosis on the first night. NTHi bacteremia, diagnosed by blood culture was identified in subsequent diagnostic procedures. Clinical improvement was observed with antibiotic treatment, despite afebrile and no elevated CRP levels during hospitalization. Previous reports indicate that late-onset IHD at >48 hours of age is rare with unclear clinical course. This case underscores the importance of considering NTHi as a potential pathogen in neonatal bacteremia, even without typical symptoms like fever and elevated CRP levels. blood samples for culture remain crucial for diagnosing bacteremia, particularly in atypical presentations. • Nontypeable H. influenzae is an important cause of late-onset neonatal bacteremia. • Late-onset neonatal bacteremia by nontypeable H. influenzae without fever or CRP elevation. • Blood cultures are vital for diagnosing neonatal bacteremia, especially in atypical cases.