Joshua Mell,
Author Of 2 Presentations
EMERGENCE OF SEROTYPE 35B PNEUMOCOCCI AS A DOMINANT STRAIN CAUSING ACUTE OTITIS MEDIA IN ROCHESTER NY. (ID 948)
Abstract
Background
Our ongoing 14-year surveillance (2006-2020) in Rochester NY has tracked pneumococcal serotypes causing acute otitis media (AOM) in children age 6-36 months.
Methods
Pneumococci were identified by culture of middle ear fluid using tympanocentesis and nasopharyngeal swabs. Serotypes were determined by Quellung and whole genome sequencing (WGS) (using Illumina NextSeq500 or Pacific Biosciences RSII). Assemblies of 35B strains were aligned using LR216049 as reference. A dot plot was used to map overall sequence similarity between “old 35B” isolated prior to 2015 and “new 35B” isolated after 2015.
Results
Serotype 35B case/carriage ratio of old 35B was 0.13 and 1.17 for new 35B, p=0.0001, suggesting increased virulence. New 35B accounts for almost 25% of all pneumococcal isolates from children with AOM, MLST was the same for old and new 35B strains (type 558). 2149 genes were consistently identified among 39 strains of 35B with WGS. Specifically WGS alignments revealed a 20 kb region encoding 30 proteins that was inverted in the old 35B (2 strains) strains compared to the new 35B (3 strains). Further analysis is ongoing.
Conclusions
35B has emerged as a dominant otopathogen in recent years among children in Rochester NY. Increased virulence appears associated with genomic change.
SEROGROUP 35 RESPONSES IN QUELLUNG REACTION AND ANALYSIS USING WHOLE GENOME SEQUENCING OF NASOPHARYNGEAL AND MIDDLE EAR FLUID ISOLATES FROM CHILDREN IN ROCHESTER NY (ID 954)
Abstract
Background
For serogroup 35, definition of serotype 35A occurs if reactions are interpreted as negative using sera specific for 35B, 35C and 35F.
Methods
From 2015-2019, a random subset of pneumococci serogroup 35 nasopharyngeal and middle ear fluid isolates from Rochester NY children were analyzed using Quellung and whole-genome sequencing (WGS).
Results
23 isolates positive for serogroup 35 by Quellung analyzed by WGS showed that 18 strains had been identified as serotype 35A by Quelling that were 35B by WGS. The 18 strains were retested by Quellung and 14 were reconsidered as positive with serotype 35B typing sera. 4 isolates were repeatedly negative for 35B by Quellung. We analyzed the genetic features of these 4 atypical 35B isolates. One isolate had a mutation on wciB (Y to C). Analysis of noncapsular region identified one region showing low similarity to the typical 35B (35B in Quelling reaction and WGS). That region was about 35K bp, coding 31 proteins that showed less than 75% similarity with typical 35B strains in DNA.
Conclusions
Caution is essential during interpretation of Quellung reactions for serogroup 35. We identified 4 atypical strains of serotype 35B that may have differential capsule expression. Further analysis is ongoing.