Detection of Non-typeable <i>Haemophilus influenzae</i> as a Causative Pathogen of Community-Acquired Pneumonia in Vietnamese Children

Background: The prevalence of invasive Haemophilus influenzae type b (Hib) disease—especially community-acquired pneumonia (CAP)—has significantly decreased due to the widespread use of Hib conjugate vaccines. Non-typeable H. influenzae (NTHi) has since emerged as the predominant etiological agent of infections across various age groups in many countries, drawing increasing attention. Objectives: This study aimed to determine the prevalence of NTHi infection in children with CAP and to compare the clinical and laboratory characteristics of children with NTHi-associated versus other agent-associated CAP. Methods: This cross-sectional study included 336 children with CAP admitted to Can Tho Children's Hospital, Vietnam, between June 2020 and June 2022. Consecutive eligible patients were enrolled to minimize selection bias. Nasotracheal aspiration samples were collected and analyzed using real-time polymerase chain reaction (PCR) to detect the presence of 70 microbial agents. Results: No cases of Hib infection were identified. The NTHi was the second most common bacterial agent causing childhood CAP, with a prevalence of 22.9%. Most cases (96.1%) involved co-infections, primarily bacterial (44.2%). The most common co-infection with NTHi was Streptococcus pneumoniae (56/77; 72.7%); only 3 of 77 children (3.9%) had CAP due to NTHi alone. Compared to those with other agent-associated CAP, children with NTHi-associated CAP experienced less tachypnea (81.8% vs. 90.3%) and more diarrhea (20.8% vs. 12.4%), along with higher white blood cell (WBC) counts (median: 15.1 G/L vs. 13.4 G/L) and C-reactive protein (CRP) levels (median: 14.9 mg/L vs. 11.0 mg/L) (P < 0.05). In multivariate logistic regression analysis, only two factors were independently associated with NTHi-associated CAP: reduced tachypnea (OR = 2.21; 95% CI: 1.07 - 4.59) and elevated WBC count (OR = 1.05; 95% CI: 1.00 - 1.10). Conclusions: The NTHi has replaced Hib as a leading cause of CAP in children. Patients presenting with less tachypnea and elevated WBC counts are more likely to have NTHi-associated CAP.