# Molecular detection of Haemophilus influenzae type b and non-typeable strains by PCR in infants under one year hospitalized with community-acquired pneumonia in Peru, 2010–2012

## TL;DR

This study used PCR to detect Haemophilus influenzae strains in infants with pneumonia in Peru, finding that unvaccinated infants were more likely to have Hib infections.

## Contribution

The study provides an early post-vaccination baseline for Hib and NTHi in Peruvian infants with pneumonia using molecular detection.

## Key findings

- H. influenzae was detected in 26.8% of infants, with Hib being the most common strain.
- Unvaccinated infants were significantly more likely to have Hib infections.
- Atelectasis was associated with non-b encapsulated serotypes of H. influenzae.

## Abstract

Community-acquired pneumonia (CAP) is one of the most common causes of morbidity and mortality among children under five worldwide. Haemophilus influenzae—particularly encapsulated serotype b (Hib) and non-typeable strains (NTHi)—remains an important pathogen. Peru introduced Hib vaccination nationally in 2004, but pediatric molecular data from the early post-introduction period are limited.

To estimate the molecular prevalence of Hib and NTHi and identify associated clinical/epidemiological factors among infants (<1 year) hospitalized with CAP in Peru during 2010–2012, providing an early post-introduction baseline to inform long-term trends. Method: We conducted a prospective multicenter study in five hospitals. Nasopharyngeal swabs underwent conventional PCR for H. influenzae detection (1000-bp) and serotyping (Hib 310-bp; NTHi 550-bp). Associations were evaluated using χ2/Fisher's tests and multivariable logistic/multinomial regression.

Among 339 infants, H. Influenzae was detected in 26.8 % (91/339): Hib 24.2 % (22/91), NTHi 3.3 % (3/91), and other encapsulated serotypes 72.5 % (66/91). In adjusted models, absence of documented Hib vaccination before admission was independently associated with Hib detection (p < 0.001). Atelectasis was associated with non-b encapsulated serotypes (RRR 2.41; 95 % CI 1.02–5.74; p = 0.046). Age and sex showed no independent associations.

These findings do not represent the current epidemiology; rather, they delineate an early post-introduction baseline for Hib/NTHi in Peruvian infants with CAP. Our findings contribute to the timeline of H. influenzae epidemiology in Peru, supports evaluations of vaccine impact over time, and underscores the need for sustained molecular surveillance and on-schedule Hib vaccination.