Development of an improved rapid BACpro® protocol and a method for direct identification from blood-culture-positive bottles using 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 incorporated into pathogenic bacterial identification methods and has improved their rapidity. Various methods have been reported to directly identify bacteria with MALDI-TOF MS by pretreating culture medium in blood culture bottles. Rapid BACpro® (Nittobo Medical Co., Ltd.) is a pretreatment kit for effective collection of bacteria with cationic copolymers. However, the Rapid BACpro® pretreatment kit is adapted only for MALDI Biotyper (Bruker Daltonics K.K.), and there has been a desire to expand its use to VITEK MS (VMS; bioMerieux SA). We improved the protocol and made it possible to analyze with VMS. The culture medium bacteria collection method was changed to a method with centrifugation after hemolysis using saponin; the cationic copolymer concentration was changed to 30% of the original concentration; the sequence with which reagents were added was changed; and a change was made to an ethanol/formic acid extraction method. The improved protocol enhanced the identification performance. When VMS was used, the identification rate was 100% with control samples. With clinical samples, the identification agreement rate with the cell smear method was 96.3%. The improved protocol is effective in blood culture rapid identification, being both simpler and having an improved identification performance compared with the original.

[Evaluation of the Fundamental Performance of 4 Latex Agglutination Reagents to Measure Anti-TP Antibody Concentration and Detailed Investigation of Decision-Mismatched Samples].

Serological diagnosis of syphilis can be made by using the serological test for syphilis (STS) method for detecting a lipid antibody and Treponema pallidum (TP) method for detecting the anti-TP-specific antibody. In STS and TP methods, the basis using latex agglutination reaction has been used in many facilities. However, in latex agglutination, false-positive results due to non-specific reaction have sometimes been obtained in reactions of a routine laboratory test reagent detecting the anti-TP antibody used in our medical laboratory. We evaluated the fundamental performance of 4 reagents to measure anti-TP antibody concentration using latex agglutination: Reagents A, B, C and D produced by SEKISUI MEDICAL, FUJI REBIO, DENKA SEIKEN and SHINO TEST, respectively. We examined the correlations between Reagent A (routine laboratory test reagent) and Reagents B, C, and D in sera from 68 patients, and we performed additional investigation by using a neutralization test, immunochromatography, Western blotting, FTA-ABS (IgG), and STS method by an automatic analyzer for 13 decision-mismatched samples. The fundamental performance of each reagent was as good as that previously reported. Eight of the 13 decision-mismatched samples were false positives due to non-specific reaction of Reagent A. In latex agglutination non-specific reaction is inevitable. However, this study strongly suggests that using a neutralization test and immunochromatography that can be performed quickly is sufficient to verify whether positive reactions are true or false.