Ultrasound enhanced detection of individual meningococcal serogroups by latex immunoassay. (Original Article)

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From: Journal of Clinical Pathology(Vol. 55, Issue 1)
Publisher: BMJ Publishing Group Ltd.
Document Type: Article
Length: 2,753 words

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Aims: To examine A, C, Y, and W 35 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 W 35 alone were tested. Positive control antigens consisted of A and C polysaccharide preparations and the Pastorex Y/W1 35 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 Wi 35 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.

Neisseria meningitidis is classified into 13 serogroups based on the capsular polysaccharide produced. The ability to confirm meningococcal disease rapidly and to distinguish between the serogroups of N meningitidis commonly associated with meningococcal disease (groups A, B, and C) is of importance for optimal clinical management of cases and contacts. Serogroups B and C are predominant in Europe, whereas serogroup A infection is most common in sub-Saharan Africa and China, where large scale epidemics affecting up to 1000 cases/100 000 population occur. (1) In the spring of 2000, outbreaks of disease were caused by serogroup W135 brought into several countries by pilgrims returning from Mecca, (2) and increased rates of serogroup Y infections have occurred in the USA over recent years. (3)

Traditionally, laboratory confirmation involves the identification of meningococci by culture and microscopy techniques. Culture takes several days, and may be hindered by the antimicrobial treatment, which, for optimal effect, is recommended to be given to patients without waiting for microbiological specimen collection. The polymerase chain reaction (PCR) is an increasingly important and sensitive technique for the detection and serogroup characterisation of meningococci. (4 5) In England, Wales, and Northern Ireland, the Public Health Laboratory Service Meningococcal Reference Unit (PHLS MRU), uses a sialyltransferase (siaD) PCR assay to identify serogroup B and C infection for those samples where meningoccocal DNA has...

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Gale Document Number: GALE|A82320742