Eficacia de la espectrometría de masas MALDI-TOF en la identificación de bacterias anaerobias / No disponible

Objetivo. La espectrometría de masas (EM) MALDI-TOF se ha convertido en un recurso de referencia para la identificación de microorganismos en los servicios de microbiología clínica. No obstante, los datos relativos a algunos grupos de microorganismos son todavía controvertidos. En el presente estudio se ha determinado la fiabilidad de la EM MALDI-TOF para la identificación de aislamientos clínicos de bacterias anaerobias, en comparación con técnicas bioquímicas convencionales, y usando como referencia en caso de discrepancias las secuenciación de ARNr 16S.Material y métodos Se analizaron 126 aislamientos clínicos de bacterias anaerobias mediante el sistema API 20A (bioMérieux, Marcy l’Étoile, Francia) y mediante EM MALDI-TOF (Autoflex II, Bruker Daltonics, Alemania), utilizando la base de datos BioTyper 2.0 (Bruker Daltonics, Alemania). Cuando se produjeron discrepancias, o la EM MALDI-TOF no fue capaz de identificar microorganismo alguno, se usó como método de identificación de referencia la secuenciación del ARNr 16S.ResultadosEl método bioquímico y la EM MALDI-TOF coincidieron, a nivel de especie, en el 60,9% de los casos, y solo a nivel de género en el 20,3%. De las 48 identificaciones discrepantes, la secuenciación respaldó la identificación por EM MALDI-TOF a nivel de especie en 32 casos (66,7%), y a nivel de género en 8 (16,7%). Dicha secuenciación apoyó la identificación bioquímica a nivel de especie solamente en 2 casos (..) (AU)

Aim of the study: MALDI-TOF mass spectrometry (MS) is becoming a major resource in the Clinical Microbiology laboratory. Results on some groups of microorganisms are still controversial. We have studied the reliability of MALDI-TOF MS for the identification of anaerobic clinical isolates was studied compared to conventional biochemical methods, with rRNA 16S sequencing being used as a reference when discrepancies arose. Material and methods: A total of 126 anaerobic bacteria clinical isolates were studied by using API20Akits (bioMérieux, Marcy l’Étoile, France) and MALDI-TOF MS (Autoflex II, Bruker Daltonics, Germany), and using the data library BioTyper 2.0 (Bruker Daltonics, Germany). When discrepancies arose, or MALDI-TOFMS was not able to identify any microorganism, rRNA 16S sequencing was used as the reference standard. Results: The biochemical method and MALDI-TOF MS agreed in identifying 60.9% of isolates at species level, and 20.3% of isolates at genus level. Among the 48 discrepancies observed, rRNA 16S sequencing (..) (AU)

[Reliability of MALDI-TOF mass spectrometry in the identification of anaerobic bacteria]. / Eficacia de la espectrometría de masas MALDI-TOF en la identificación de bacterias anaerobias.

AIM OF THE STUDY: MALDI-TOF mass spectrometry (MS) is becoming a major resource in the Clinical Microbiology laboratory. Results on some groups of microorganisms are still controversial. We have studied the reliability of MALDI-TOF MS for the identification of anaerobic clinical isolates was studied compared to conventional biochemical methods, with rRNA 16S sequencing being used as a reference when discrepancies arose. MATERIAL AND METHODS: A total of 126 anaerobic bacteria clinical isolates were studied by using API20A kits (bioMérieux, Marcy l'Étoile, France) and MALDI-TOF MS (Autoflex II, Bruker Daltonics, Germany), and using the data library BioTyper 2.0 (Bruker Daltonics, Germany). When discrepancies arose, or MALDI-TOF MS was not able to identify any microorganism, rRNA 16S sequencing was used as the reference standard. RESULTS: The biochemical method and MALDI-TOF MS agreed in identifying 60.9% of isolates at species level, and 20.3% of isolates at genus level. Among the 48 discrepancies observed, rRNA 16S sequencing supported MALDI-TOF MS identification, at species level, in 32 isolates (66.7%), and in 8 isolates (16.7%) at genus level. rRNA 16S sequencing supported biochemical identification in only two isolates (4.2%) at species level, and in 26 isolates (54.2%) at genus level. The eight isolates for which MALDI-TOF MS did not manage to identify, or the identification obtained was rejected by sequencing, belonged to species that are still not added to the BioTyper II data library. CONCLUSIONS: Results obtained in this study show that, overall, MALDI-TOF MS identification of anaerobic bacteria is more reliable than identification obtained by conventional biochemical methods (24% more correct identifications at species level). The number of major errors (incorrect identification at the genus level) is also 2.5-times lower. Moreover, all the major errors obtained by MALDI-TOF MS were due to the absence of some species in the data library. Thus, when data libraries are more complete, reliability differences between both methods will probably be even higher.

Direct identification of urinary tract pathogens from urine samples by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been suggested as a reliable method for bacterial identification from cultures. Direct analysis of clinical samples might increase the usefulness of this method, shortening the time for microorganism identification. We compared conventional methods for the diagnosis of urinary tract infections (UTIs) and identification of the urinary tract pathogens (automated screening, plate cultures, and identification based on biochemical characteristics) and a fast method based on conventional screening and MALDI-TOF MS. For this latter method, 4 ml of urine was centrifuged at a low-revolution setting (2,000 x g) to remove leukocytes and then at high revolutions (15,500 x g) to collect bacteria. The pellet was washed and then applied directly to the MALDI-TOF MS plate. Two hundred sixty urine samples, detected as positive by the screening device (UF-1000i), were processed by culture and MALDI-TOF MS. Twenty samples were positive in the screening device but negative in culture, and all of them were also negative by MALDI-TOF MS. Two-hundred thirty-five samples displayed significant growth of a single morphological type in culture. Two-hundred twenty of them showed bacterial growth of >10(5) CFU/ml. Microorganism identifications in this group were coincident at the species level in 202 cases (91.8%) and at the genus level in 204 cases (92.7%). The most frequent microorganism was Escherichia coli (173 isolates). MALDI-TOF MS identified this microorganism directly from the urine sample in 163 cases (94.2%). Our results show that MALDI-TOF MS allows bacterial identification directly from infected urine in a short time, with high accuracy, and especially when Gram-negative bacteria with high bacterial counts are involved.