To further confirm identification, multilocus sequence typing (MLST) was performed on all U.S. carriage study and ctrA-negative NG isolates.
Interestingly, sodC identified one isolate, M16160, as Nm when other standard carriage study tests could not correctly resolve its species.
Four sodC-negative carriage study isolates that were identified as Nm by conventional methods were re-investigated and shown to actually be non-Nm.
1/33 (3%) NP swab eluate extractions from the UK carriage study was ctrA-positive, 0/33 were sodC-positive, and 0/33 were Nm culture-positive.
None of 35 non-Nm from various sources and none of 209 non-meningococcal carriage study [20], [24] isolates were detected by sodC (100% specificity) (Table 2).
All (291/291, 100%) NP swab eluate extractions from the Georgia CHOA carriage study were ctrA-negative and sodC-negative, as expected, since no Nm was cultured.
However, given that ctrA is not present in 16% or more of carriage isolates [11], [12], it is not a suitable target gene for PCR on carriage study specimens.
DNA extractions were performed on the CHOA carriage study NP swab eluates using the MagNA Pure LC instrument and the DNA Isolation Kit III (Bacteria, Fungi) per the manufacturer's instructions (Roche Diagnostics GmbH, Mannheim, Germany).
Twenty-six strains (90%) were isolated in Germany either in the course of the Bavarian carriage study [1] or were taken from the strain collection of the German Reference Laboratory for Meningococci (NRZM, Würzburg, Germany) spanning the same time period.
S. aureus (n = 17), alpha-hemolytic streptococci (n = 18), M. catarrhalis (n = 5), diptheroids (n = 10), N. polysaccharea (n = 1), N. cinerea (n = 2), and N. meningitidis (n = 1) were cultured from the 68 UK carriage study specimens; the Nm culture-positive NW was ctrA-positive and sodC-positive.
Our carriage study did not detect this development.
