S. Pneumoniae Remains Leading Cause of Acute Otitis Media Despite Reduction in Prevalence

Despite a reduction in prevalence, Streptococcus pneumoniae (S 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, and it is otherwise known as an ear infection, impacting 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

While 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 (H 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,” continued 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 within 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.

Aside from 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 sociodemographic characteristics like age, household structure, and education level, while potential risk factors like tobacco smoke exposure and daycare attendance were also considered.

The study included a total of 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. While just 4.9% did not receive any pneumococcal vaccine, 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 a total of 6 S pneumoniae infections in total. Among the 6 cases, 5 received PCV and 1 was not vaccinated.

Finally, 19A was the most prominent serotype, appearing in 67% of patients, while 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,” they 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.”

In the context of a non-invasive disease like AOM, researchers aimed results of the study at informing future immunization recommendations for the continuously evolving landscape of PCVs, their serotypes, and their valencies. Specifically, results of the current study were provided to contribute 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, this study provides a valuable baseline for monitoring changes in serotype distribution and resistance patterns by S. pneumoniae in the context of a non-invasive 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