Serologic comparison of 35B/ST156 lineage strains with CDC Quellung
reagents for resolution of serogroup 35B invasive serotype pneumococci including an expanding serotype switch lineage, United States, 2015-2016 * Quellung
factor Strain 35b 29b 35c 42a 35a cps35B ([dagger]) - + + - + cps35B (wciG deletion) - + + - - ([double dagger]) * CDC, Centers for Disease Control and Prevention; ST, sequence type; -, negative; +, positive.
Serotyping based on the Quellung
reaction requires expensive reagents and substantial training and experience to perform reliably.
Identification of capsular type by the quellung
reaction and resistance genotyping by real-time PCR was performed within 1 day of sample collection for each strain.
Serotyping was performed by use of the Neufeld Quellung
reaction, a technique previously described (22) by using polyclonal antisera.
Thirty strains were sent to CDC for serotyping but could not be typed using the Quellung
Isolates received at the Spanish Reference Laboratory for Pneumococci were serotyped by using the quellung
reaction and antisera provided by the Staten Serum Institute (Copenhagen, Denmark) (8).
All pneumococci isolated in 1998 and 1999 were serotyped using the quellung
Serotypes of all isolates were determined by the capsular quellung
reaction using antiserum purchased from the Statens Serum Institute (Copenhagen, Denmark).
Serogrouping and serotyping were performed by the quellung
reaction using antiserum provided by Statens Serum Institute (Copenhagen, Denmark) (8).
The capsular serotype of all isolates was determined by using the Quellung
reaction with antisera from the Statens Serum Institut (Copenhagen, Denmark).
All pneumococcal isolates that exhibited a positive quellung
reaction when commercial type-specific antiserum (Statens Serum Institute, Copenhagen, Denmark) was used were assigned a serotype (10).