Verification of an Alternative Method of Detection and Quantification of Legionella spp. in a Public Health Laboratory: Immunomagnetic Separation (IMS) and Identification by Colorimetric Reaction

• Main Authors: Eva Álvarez Merchán, Juan Manuel Fernández Gallego, Juan Carlos Montero Rubio
• Format: Article
• Language: English
• Published: Sociedad Española de Sanidad Ambiental 2021-06-01
• Series: Revista de Salud Ambiental
• Subjects: legionella spp.; verificación; separación inmunomagnética; cuantificación; precisión; recuperación; linealidad
• Online Access: https://ojs.diffundit.com/index.php/rsa/article/view/1055
• ISSN: 1577-9572; 1697-2791

Spanish Royal Decree 865/2003 on the prevention and control of legionellosis mentions the culture method of standard ISO 11731 for testing <em>Legionella spp.</em>, a standard which sets different parametric levels. The weaknesses that have been detected in the method of said standard (false negatives and high waiting times) have made it necessary to look for alternatives. The aim of this study is to determine whether the method of immunomagnetic separation (IMS) and quantification of <em>Legionella spp.</em> Legipid® Legionella Fast Detection is suitable and effective for analyzing environmental water samples in an official public health laboratory. In the absence of a standardized methodology for verifying alternative methods, we devised a method for carrying out this verification taking into account specific criteria for microbiological analysis and the ENAC’s guide for test kits. Thus, we calculated the parameters of precision and recovery of the inoculated samples, as well as the linearity from the slope and the ordinate at the origin of the absorbance-colony forming unit (CFU) relationship, and compared the experimental data we obtained with the results of the validation of the method. The results were satisfactory in all cases: a dispersion below 20 %, a recovery in the 4-71 % range, and a linearity compliant with the validation with a significance level exceeding 95 %. Based on these results, we consider the ISM method to be a valid method for detecting and quantifying <em>Legionella spp.</em> in an official public health laboratory.