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Open Access Research article

Production of latex agglutination reagents for pneumococcal serotyping

Belinda D Ortika1, Maha Habib1, Eileen M Dunne1, Barbara D Porter1 and Catherine Satzke123*

Author Affiliations

1 Pneumococcal Research, Murdoch Childrens Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia

2 Infectious Diseases and Microbiology, Murdoch Childrens Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia

3 Department of Microbiology and Immunology, The University of Melbourne, Parkville, Victoria, Australia

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BMC Research Notes 2013, 6:49  doi:10.1186/1756-0500-6-49

Published: 5 February 2013

Abstract

Background

The current ‘gold standard’ for serotyping pneumococci is the Quellung test. This technique is laborious and requires a certain level of training to correctly perform. Commercial pneumococcal latex agglutination serotyping reagents are available, but these are expensive. In-house production of latex agglutination reagents can be a cost-effective alternative to using commercially available reagents. This paper describes a method for the production and quality control (QC) of latex reagents, including problem solving recommendations, for pneumococcal serotyping.

Results

Here we describe a method for the production of latex agglutination reagents based on the passive adsorption of antibodies to latex particles. Sixty-five latex agglutination reagents were made using the PneuCarriage Project (PCP) method, of which 35 passed QC. The other 30 reagents failed QC due to auto-agglutination (n=2), no reactivity with target serotypes (n=8) or cross-reactivity with non-target serotypes (n=20). Dilution of antisera resulted in a further 27 reagents passing QC. The remaining three reagents passed QC when prepared without centrifugation and wash steps. Protein estimates indicated that latex reagents that failed QC when prepared using the PCP method passed when made with antiserum containing ≤ 500 μg/ml of protein. Sixty-one nasopharyngeal isolates were serotyped with our in-house latex agglutination reagents, with the results showing complete concordance with the Quellung reaction.

Conclusions

The method described here to produce latex agglutination reagents allows simple and efficient serotyping of pneumococci and may be applicable to latex agglutination reagents for typing or identification of other microorganisms. We recommend diluting antisera or removing centrifugation and wash steps for any latex reagents that fail QC. Our latex reagents are cost-effective, technically undemanding to prepare and remain stable for long periods of time, making them ideal for use in low-income countries.

Keywords:
Latex agglutination; Serotyping; Streptococcus pneumoniae