Impact of Streptococcus pneumoniae in Acute Otitis Media (AOM) with Spontaneous Tympanic Membrane Perforation (sTMP): Serotype Distribution 4 Years After 13-Valent Pneumococcal Conjugate Vaccine (PCV13) Introduction

Background: S. pneumoniae frequently causes AOM, including cases complicated by sTMP. PCV13 serotypes are considered the most common responsible of pneumococcal AOM. Surveillance of microbiology of AOM is important to evaluate efficacy of PCV13 and potential serotype replacement. In Italy, no data after introduction of PCV13 were collected. In this study, the role of S. pneumoniae serotypes as cause of AOM with sTMP in Italian children was evaluated.

Methods: Patients <12 years old with AOM and sTMP were enrolled. Middle ear fluid (MEF) was obtained by means of swab of spontaneous ear pus discharge from ear canal. A nasopharyngeal swab was obtained to evaluate respiratory secretions. Nucleic acid extracts from swabs were tested for the autolysin-A (LytA) and wzg (cpsA) genes of S. pneumoniae by means of real-time PCR. Positive samples were serotyped using primers and probes designed on the basis of the GenBank database sequences of serotypes 1, 2, 3, 4, 5, 6A, 6B, 6C/D, 7 F, 8, 9 V, 10A/B, 11A/D, 12A/B/F, 14, 16F, 17F, 18C, 19A, 19 F, 20, 21, 22A/F, 23A, 23B, 23F, 24A/B/F, 29, 33A/F, 35B, 35F, and 38. The children pneumococcal vaccination status was established by consulting the official vaccination chart issued by the Italian Vaccination Service.

Results: A total of 177 children were enrolled: 65 were aged < 2 years, 68 aged 2-4 years, and 44 aged ≥ 5 years. Children <2 years and those 2-4 years old had received PCV13 in 90.8% and 95.6% of the cases. Patients ≥5 years old were vaccinated with PCV7 in 63.6% of the cases. S. pneumoniae was identified in 48 (27.1%) cases (24, 36.9%, 12, 17.6%, and 12, 27.3%, in the three age groups, respectively). Serotypes not included in PCV13 were identified in 16 (66.7%), 8 (66.7%), and 11 (91.7%) of the children aged < 2, 2-4, and ≥ 5 years old. Serotypes 11A/D/F, 15AF, 21, 24ABF, 33A/F, and 38 were the most common in all the age groups and independently of the vaccination status. Among PCV13 serotypes, serotype 3 was the most common.

Conclusion: This study shows that in Italy pneumococcal AOM with sTMP is associated mainly with serotypes not included in PCV13. This suggests that a significant replacement phenomenon is presently active and prevention of pneumococcal AOM requires vaccines with larger serotype coverage.