A comparative study of two different methods of sample preparation for positive blood cultures for the rapid identification of bacteria using MALDI-TOF MS.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has lately been implemented as a solid technology for rapid microorganism identification in microbiology laboratories. This study compares two methods for bacterial separation from 85 positive blood culture before MALDI-TOF MS: (1) a conventional method that we used in our laboratory to prepare bacteria for susceptibility testing and (2) a new commercialized technique (Sepsityper). There were no significant differences in the identification of Gram-negative bacilli regardless of the bacterial separation method used.

Two chromosomally located qnrB variants, qnrB6 and the new qnrB16, in Citrobacter spp. isolates causing bacteraemia.

The objective of this study was to determine the prevalence of the plasmid-borne quinolone resistance genes qnrA, qnrB and qnrS in a collection of Enterobacteriaceae causing bacteraemia. The presence of the three genes was tested for using multiplex PCR in 306 clinical isolates. Plasmid analysis was performed using I-CeuI and S1 nuclease digestion and hybridization with specific probes for the qnr and 23S rRNA genes.

Recommendations for the performance of bacterial mutation assays.

At the International Workshop on the Standardisation of Genotoxicity Test Procedures, in Melbourne (27-28 February 1993), the current international guidelines for the correct conduct of bacterial mutation assays were considered, and the major differences between them were examined. An attempt was made to construct a scientifically based, internationally harmonized protocol. The main points of agreement were as follows.

Validation of the in vivo CD1 mouse splenocyte micronucleus test.

In order to validate the in vivo micronucleus test in mouse splenocytes using the cytokinesis block method, 14 compounds with various mechanisms of action were tested: three direct alkylating agents (mitomycin C, ethylnitrosourea, beta-propiolactone), seven indirect alkylating agents (cyclophosphamide, benzo[a]pyrene, diethylnitrosamine, dimethylnitrosamine, 4-aminophenol, 4-aminobiphenyl, 1,1-dimethylhydrazine), two intercalating agents (acridine orange, ethidium bromide) and two spindle poisons (vincristine, colchicine). Male mice were dosed once with the compound, and spleen samples were taken 2 or 14 days after treatment. A significant increase in the binucleated micronucleated splenocyte rate was observed with all the alkylating and intercalating agents at at least one sampling time.

Lack of predictivity of bone marrow micronucleus test versus testis micronucleus test: comparison with four carcinogens.

In vivo somatic chromosome mutation tests are usually carried out using the bone marrow micronucleus test in the mouse. This test is also considered predictive for the study of clastogenic effects in germ cells. However, it has been reported that the sensitivity of the bone marrow micronucleus test is insufficient to detect unstable compounds or short-lived metabolites and the use of target cells with metabolic activity (hepatocytes) has been questioned.