ORIGINAL ARTICLE

Ultrasound enhanced detection of individual meningococcal serogroups by latex immunoassay

M A Sobanski¹, R Vince¹, G A Biagini¹, C Cousins¹, M Guiver², S J Gray², E B Kaczmarski², W T Coakley¹

¹ School of Biosciences, Cardiff University, Cardiff CF10 3TL, UK
² Public Health Laboratory Service Meningococcal Reference Unit, Manchester Public Health Laboratory, M20 2LR, UK

Correspondence to:
Correspondence to:
Professor W T Coakley, School of Biosciences, Cardiff University, Cardiff CF10 3TL UK;
Coakley{at}cardiff.ac.uk

Aims: To examine A, C, Y, and W135 Neisseria meningitidis serogroup characterisation by ultrasonic standing wave enhanced latex agglutination tests (USELATs) of clinical samples. In addition, to determine USELAT enhancement of detection sensitivity for the individual antigens compared with conventional card latex agglutination tests (LATs).

Methods: Wellcogen (Abbott Murex), Slidex meningite kit 5 (bioMerieux), and Pastorex (Sanofi) kits and beads coated in house with antibodies to Y and to W135 alone were tested. Positive control antigens consisted of A and C polysaccharide preparations and the Pastorex Y/W135 kit sample. The limiting concentrations of antigen detection were determined by USELAT and by LAT. Thirty five clinical samples (plasma), previously characterised by the polymerase chain reaction (PCR) and culture, were tested by USELAT and, when sample volume allowed, by LAT.

Results: USELAT enhancement of control antigen detection ranged from 16 to 128 fold for the different latex systems. Enhancements for the different control antigens were comparable between kits. USELAT tests of clinical (A/C/Y/W135) samples (n = 15) with the Wellcogen (A/C/Y/W135) and Slidex meningite (A/C/Y/W135) kits showed comparable specificities. A set (n = 22) of Y and W135 samples gave 18, 19, and 17 positive results for Wellcogen (A/C/Y/W135), Pastorex (A/C/Y/W135), and in house beads (Y/W135), respectively. Positive USELAT PCR and culture results were concordant. A typical sensitivity for the commercial kits was 80% (Wellcogen).

Conclusions: USELAT identified serogroups for 80% of samples, whereas LATs identified only 40%. The USELAT detection of the A, C, Y, and W135 antigen serogroups showed comparable enhancement for the kits tested. The commercial availability of latex beads coated with antibody to the Y and W135 serogroups would expedite their identification.

Keywords: meningococcal disease; Neisseria meningitidis serogroups A, C, Y, W135; ultrasound; latex immunoagglutination

Abbreviations: CAMR, Centre for Applied Microbiological Research; LAT, latex agglutination test; MRU, Meningococcal Reference Unit; PCR, polymerase chain reaction; PHLS, Public Health Laboratory Service; siaD, sialyltransferase; USELAT, ultrasonic standing wave enhanced latex agglutination test

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