Rapid identification of pneumococci and enterococci in blood culture bottles using Latex Agglutination

Abstract number: P1392

Cebollero A., Lloret M., Pons I., Sanfeliu I., Espasa M., Fontanals D.

Objective: To evaluate two commercial latex agglutination tests, for rapid identification of pneumococci and enterococci directly from positive blood culture bottles that showed the presence of Gram-positive diplococci by the Gram stain.

Methods: Period of study: From November 2005 to November 2007. Samples: All positive blood culture bottles where we visualised only Gram-positive diplococci by direct Gram stain. Agglutination test: 1 ml from the positive blood culture bottle was centrifuged at 2500 rpm for 10 min. To test Slidex pneumo-kit ® (bioMérieux), one drop of supernatant was mixed with one drop of latex reagent and to test the Streptococcal Grouping kit ® (Oxoid Diagnostic Reagents), 1 drop of supernatant was mixed with 1 drop of each latex group reagent (A, B, C, D, F, G). Boths reagents were mixed and rotated for 2 min. The results were evaluated comparing to the standardised identification methods from solid media.

Results: A total of 120 positive blood culture bottles were analysed with the following isolates: 87 Streptococcus pneumoniae, 16 Enterococcus faecalis, 14 Enterococcus faecium and 3 Enterococcus spp. – Firstly, the Slidex pneumo-kit ® to identify pneumococci showed a sensitivity of 91.5% and a 100% specificity, and the positive and negative predictive values were 100% and 80%, respectively. Secondly, the Streptococcal Grouping kit ® evaluation for group D agglutination reagent to identify enterococci had a sensitivity of 75.8% and a specificity of 100%, and the positive and negative predictive values were 100% and 84.6%, respectively. In addition, we observed that 35 (79.5%) pneumococci showed positive agglutination with group C latex reagent. Summarising, both latex agglutination tests showed specificity values close to 100% and sensitivity values higher than 75% to identify pneumococci and enterococci.

Conclusion: The results of this study suggest that both reagents could be used to provide an earlier identification than standard methods of Gram-positive diplococci, and the combination of the two of them is useful to distinguish between pneumococci and enterococci. In adition both test are inexpensive and easy to perform in any laboratory.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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