Value of matrix-assisted laser desorption ionization-time of flight for routine identification of viridans group streptococci causing bloodstream infections
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2012
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Elsevier
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López Roa, P., et al. «Value of Matrix-Assisted Laser Desorption Ionization-Time of Flight for Routine Identification of Viridans Group Streptococci Causing Bloodstream Infections». Clinical Microbiology and Infection, vol. 19, n.o 5, mayo de 2013, pp. 438-44. DOI.org (Crossref), https://doi.org/10.1111/j.1469-0691.2012.03837.x.
Abstract
La identificación fenotípica de los estreptococos del grupo viridans (VGS) presenta limitaciones y no siempre permite una correcta discriminación a nivel de especie. El análisis de la secuencia del gen sodA es el método más preciso, aunque su aplicación rutinaria en los laboratorios de microbiología clínica es limitada. La espectrometría de masas MALDI-TOF se ha propuesto como una alternativa rápida para la identificación bacteriana.
En este estudio se evaluó la capacidad de MALDI-TOF y del sistema API 20 Strep para identificar aislamientos clínicos de VGS procedentes de hemocultivos, utilizando el análisis de la secuencia sodA como método de referencia. Se analizaron 124 aislamientos clínicamente significativos recogidos entre enero de 2007 y enero de 2010.
La sensibilidad para la identificación a nivel de especie fue del 60,5 % para API 20 Strep y del 73,4 % para MALDI-TOF, mientras que para la identificación a nivel de grupo fue del 70 % y del 94,3 %, respectivamente. Los tiempos de respuesta fueron de 12–24 horas para sodA, 24–48 horas para API 20 Strep y aproximadamente 15 minutos para MALDI-TOF.
En conclusión, API 20 Strep no identifica de forma fiable todos los aislamientos de VGS. MALDI-TOF constituye una alternativa rápida y fiable para la identificación a nivel de grupo, aunque presenta limitaciones para discriminar especies estrechamente relacionadas dentro de determinados grupos.
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Phenotypic tests do not always unequivocally identify some species of viridans group streptococci (VGS). sodA sequence analysis is the most accurate method for identification, although it requires specialized personnel and has not been applied systematically in clinical microbiology laboratory routines. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) is emerging as a rapid alternative for bacterial identification. This study assesses the ability of MALDI-TOF and the API 20 Strep system to identify VGS isolates recovered from blood cultures using sodA sequence analysis as the reference method. All clinically significant VGS isolates recovered from blood cultures between January 2007 and January 2010 were identified by sodA sequence analysis and API 20 Strep. The strains were then tested by MALDI-TOF. Agreement between API 20 Strep/MALDI-TOF and sodA sequence analysis was determined. We examined 124 clinical isolates. Sensitivities of API 20 strep and MALDI-TOF for the species level identification of VGS isolates were, respectively, as follows: 60.5% and 73.4%. Sensitivities of API 20 strep and MALDI-TOF for the group level identification were, respectively, as follows: 70% and 94.3%. The turnaround times to identify VGS isolates by sodA sequence analysis, API 20 Strep and MALDI-TOF were 12–24, 24–48 h and 15 min, respectively. API 20 Strep cannot accurately identify all isolates of VGS. MALDI-TOF appeared to be a rapid and reliable alternative for identification of VGS strains to group level, but was not able to discriminate closely related species of certain groups.
Phenotypic tests do not always unequivocally identify some species of viridans group streptococci (VGS). sodA sequence analysis is the most accurate method for identification, although it requires specialized personnel and has not been applied systematically in clinical microbiology laboratory routines. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) is emerging as a rapid alternative for bacterial identification. This study assesses the ability of MALDI-TOF and the API 20 Strep system to identify VGS isolates recovered from blood cultures using sodA sequence analysis as the reference method. All clinically significant VGS isolates recovered from blood cultures between January 2007 and January 2010 were identified by sodA sequence analysis and API 20 Strep. The strains were then tested by MALDI-TOF. Agreement between API 20 Strep/MALDI-TOF and sodA sequence analysis was determined. We examined 124 clinical isolates. Sensitivities of API 20 strep and MALDI-TOF for the species level identification of VGS isolates were, respectively, as follows: 60.5% and 73.4%. Sensitivities of API 20 strep and MALDI-TOF for the group level identification were, respectively, as follows: 70% and 94.3%. The turnaround times to identify VGS isolates by sodA sequence analysis, API 20 Strep and MALDI-TOF were 12–24, 24–48 h and 15 min, respectively. API 20 Strep cannot accurately identify all isolates of VGS. MALDI-TOF appeared to be a rapid and reliable alternative for identification of VGS strains to group level, but was not able to discriminate closely related species of certain groups.