After introduction of PCV-13 in the USA in 2010, emergence of replacement serotypes occurred. From our ongoing 14-year prospective study we report Streptococcus pneumoniae (Spn) strains colonizing the nasopharynx (NP) of children based on serotype, sequence type (ST) and antibiotic susceptibility along with otopathogens, Haemophilus influenzae (Hi) and Moraxella catarrhalis (Mcat) for years 2015-2019.
2059 visits (1528 healthy, 393 AOM and 138 AOM-follow-up visits) from 589 children, ages 6-36 months were included. 495 middle-ear fluid (MEF) were obtained during AOM by tympanocentesis.
In the NP we isolated Mcat (39%) >Spn (32%) >Hi (12%) at healthy visits and Mcat=Spn (53%) >Hi (36%) at onset of AOM. MEF culture results were Hi (35%) >Spn (24%) >Mcat (15%) Correlation of NP and MEF isolates at onset of AOM was poor. In the NP, serotype 35B (18.3%/20.6%) >23B (17.9%/9.1%)>15B/C (10.6%/12%) predominated at healthy/at onset of AOM. 35B (22.4%) was the most common serotype isolated from MEF. ST558 and ST199 were the most common sequence types in healthy and AOM visits. Penicillin and erythromycin antibiotic-nonsusceptibility were most frequent among Spn isolates
Dynamic changes in pneumococcal prevalence and serotypes colonizing the NP and causing AOM occurred in 2015-2019.