S Pneumoniae Remains Leading Cause of Acute Otitis Media Despite Reduced Prevalence

Despite a reduction in prevalence, Streptococcus pneumoniae infection remains a leading cause of acute otitis media (AOM) in children, according to data published in PLoS One.¹

“AOM is a common childhood infection and a leading cause of antibiotic prescriptions,” wrote the authors. “It is estimated that 80% of children experience at least one episode of AOM before the age of 3 and 50% before the age of 1, with a peak occurrence between 9 and 15 months of age.”

AOM is one of the most common childhood illnesses, according to Mayo Clinic. It is otherwise known as an ear infection and affects the space behind a patient’s eardrum, known as the middle ear.² Signs and symptoms include a child’s inability to sleep, acute ear pain, fever, or overall fussiness and irritability.³

Although the matter is still under debate, according to study researchers, bacterial colonization of specific pathogens is considered a requirement for the development of AOM. The 2 most common pathogens reported in patients with AOM are non-typeable Haemophilus influenzae and S pneumoniae. Moraxella catarrhalis is the third leading pathogen, reported in 3% to 20% of patients with AOM.^1,3

Researchers conducted a prospective cohort study of patients with AOM shortly after introduction of PCV-13 as a replacement for PCV-10. | image credit: andrey / stock.adobe.com

READ MORE: Pneumococcal Vaccine Rates Low Despite Updated Recommendations

In Colombia, where the current study was conducted, pediatric AOM cases are almost split between H influenzae (31%) and S pneumoniae (30%), with other pathogens making up the remaining 39% of cases. However, researchers decided to solely focus on the S pneumoniae pathogen due to the significant knowledge gaps that exist regarding the infection’s role in Latin America.

“It is essential to understand the current role of S pneumoniae in the bacterial etiology of AOM and how the introduction of PCV-10 in infancy impacts the current serotype distribution,” said the authors.¹ They evaluated the prevalence of bacterial AOM caused by S pneumoniae in children between the ages of 3 and 59 months in Cartagena, Colombia.

From 2011 to 2022, the 10-valent pneumococcal conjugate vaccine (PCV-10) was the first line of defense against S pneumoniae in Colombia’s national immunization schedule. Exploring data between August 2022 and August 2023, shortly after PCV-10 was replaced with PCV-13, researchers conducted a prospective cohort study of patients with AOM between the ages of 3 and 59 months.

In addition to the overall prevalence of pediatric AOM in Colombia, they also explored serotype distribution and antimicrobial resistance patterns from participants’ middle ear fluid (MEF) samples. Researchers collected data on sociodemographic characteristics, including age, household structure, and education level, and they also considered potential risk factors such as tobacco smoke exposure and daycare attendance.

The study included 61 participants (mean age, 1 year; 57.4% boys) with an AOM diagnosis by a certified ear, nose, and throat specialist. Regarding pneumococcal vaccine uptake, 62.3% of the cohort received PCV-10 because they were born before the introduction of PCV-13 in April 2022. Only 4.9% did not receive any pneumococcal vaccine, and 32.8% of patients received the newly accepted PCV-13.

Of the isolated microorganisms that can cause AOM, Pseudomonas aeruginosa (14.8%) and methicillin-resistant Staphylococcus aureus (13.1%) were the most prominent. S pneumoniae was identified as the microorganism in 9.8% of AOM cases, accounting for 6 S pneumoniae infections. Among the 6 cases, 5 received PCV and 1 was not vaccinated.

Finally, 19A was the most prominent S pneumoniae serotype, appearing in 67% of patients, whereas 10F and 35A were each present in 17% of cases. The 19A serotype was also identified as multidrug resistant.

“Among 61 children with otorhinolaryngologist-confirmed AOM, S pneumoniae was identified in 9.8% of MEF samples, with serotype 19A being the most frequent,” the researchers wrote.¹ “Notably, all pneumococcal isolates corresponded to non–PCV-10 serotypes, and most showed resistance to at least one antibiotic group. These findings highlight serotype replacement and antimicrobial resistance in the post–pneumococcal vaccination era, underscoring the need for enhanced surveillance and potentially broader vaccine formulations tailored to local epidemiology.”

Regarding a noninvasive disease such as AOM, the researchers hope the study's results will inform future immunization recommendations for the continuously evolving landscape of PCVs, their serotypes, and their valencies. Specifically, they provided the results as a means of contributing to future studies on S pneumoniae serotypes post PCV–10 introduction.

“The prevalence of AOM due to S pneumoniae has been reduced, although the most frequently found serotypes are not included in PCV-10. Notably, serotype 19A caused 67% of the isolates,” concluded the authors.¹ “As Colombia transitions from PCV-10 to PCV-13, [the data from] this study provide a valuable baseline for monitoring changes in serotype distribution and resistance patterns by S pneumoniae in the context of a noninvasive disease.”

READ MORE: Pneumococcal Resource Center

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References

1. Coronell-Rodriguez W, Camerano R, Alvarado-Gonzalez JC, et al. Evaluation of Streptococcus pneumoniae as a cause of acute otitis media in Colombia: a prospective study. PLoS One. 2025;20(7):e0326660. doi:10.1371/journal.pone.0326660

2. Ear infection (middle ear). Mayo Clinic. April 23, 2025. Accessed July 30, 2025. https://www.mayoclinic.org/diseases-conditions/ear-infections/symptoms-causes/syc-20351616

3. Ear infection basics. CDC. April 17, 2024. Accessed July 30, 2025. https://www.cdc.gov/ear-infection/about/index.html