Fluorescent amplified-fragment length polymorphism genotyping of Neisseria meningitidis identifies clones associated with invasive disease

Abstract

Fluorescent amplified-fragment length polymorphism (FAFLP), a genotyping technique with phylogenetic significance, was applied to 123 isolates of Neisseria meningitidis. Nine of these were from an outbreak in a British university; 9 were from a recent outbreak in Pontypridd, Glamorgan; 15 were from sporadic cases of meningococcal disease; 26 were from the National Collection of Type Cultures; 58 were carrier isolates from Ironville, Derbyshire; 1 was a disease isolate from Ironville; and five were representatives of invasive clones of N. meningitidis. FAFLP analysis results were compared with previously published multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) results. FAFLP was able to identify hypervirulent, hyperendemic lineages (invasive clones) of N. meningitidis as well as did MLST. PFGE did not discriminate between two strains from the outbreak that were classified as similar but distinct by FAFLP. The results suggest that high resolution of N. meningitidis for outbreak and other epidemiological analyses is more cost efficient by FAFLP than by sequencing procedures.

FIG. 1

Genotyper output of FAFLP analysis of replicates of NCTC type strain 8554 in the range of 210- to 310-bp fragments. The five traces represent separate FAFLP reactions on the same DNA extract, run on different gels. The boxed numbers under the peaks of the traces are the fragment sizes in base pairs assigned by comparison with the standard curve generated with the internal size standard.

FIG. 2

Tree representing FAFLP data for 119 N. meningitidis isolates with the serogroup, where known, indicated for each isolate (see key). One serogroup, W-135, clustered closely by FAFLP (circled), an exception being Ironville isolate 560.

FIG. 3

Tree identical to that in Fig. 2 except that the invasive disease-causing isolates and the carriage isolates are indicated. FAFLP separated the disease-causing strains into five clusters (circled). The largest of these, cluster 1, consisted of the majority of Southampton and Pontypridd, United Kingdom (UK), outbreak strains.