Evaluation of species-specific score cut-off values for various Staphylococcus species using a MALDI Biotyper-based identification.

Although previous studies investigating the MALDI Biotyper database (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry-based identification) have proven its high accuracy for bacterial identification, the studies differed in sample preparation, number of replicates, quantity of shots and target types used. In particular, the score cut-off values of special importance for reliable species identification varied. The aim of the present study was to identify species-specific differences in the mean score values for staphylococci. Cut-off values recommended by the manufacturer were adapted using the 20th percentile to rule out unknown score-modifying factors, even though the specificity was high and the lowest cut-off values would also yield an accurate result. Whilst correct species diagnosis was obtained in 97.32 % of samples (1382/1420), only 220 of all duplicates (15.49 %) revealed a score of ≥2.3, whilst 968 (68.17 %) had a score between 2.0 and 2.299, and 194 (13.66 %) had a score of <2.0. Ten of 21 species had a calculated 20th percentile of <2.0 and one species of <1.7. In conclusion, the use of species-specific cut-off values improves the relative sensitivity of species identification in staphylococci.

Micromorphometrical analyses of five different ultrasonic osteotomy devices at the rabbit skull.

OBJECTIVES: The recently introduced ultrasonic osteotome procedure is an alternative to conventional methods of osteotomy. The aim of the present study was to establish the differences between five recently introduced ultrasonic osteotomes and to perform micromorphological and quantitative roughness analyses of osteotomized bone surfaces. MATERIALS AND METHODS: Fresh, standard-sized bony samples were taken from a rabbit skull using the following ultrasonic osteotomes: the Piezosurgery 3 with insert tip OT7, Piezosurgery Medical with insert tip MT1-10, Piezon Master Surgery with insert tip SL1, VarioSurg with inert tip SG1, and Piezotome 2 with insert tip BS1 II. The required duration of time for each osteotomy was recorded. The prepared surfaces were examined via light microscopy, environmental surface electron microscopy (ESEM), and confocal laser scanning microscopy (CLSM). RESULTS: All of the investigated piezoelectric osteotomes preserved the anatomical structure of bone. The mean roughness values of the osteotomized bone edge obtained using the investigated piezoelectric osteotomes were as follows: 2.47 µm (Piezosurgery 3), 9.79 µm (Piezosurgery Medical), 4.66 µm (Piezon Master Surgery), 6.38 µm (VarioSurg), and 6.06 µm (Piezotome 2). Significantly higher roughness values were observed when using the Piezosurgery Medical in comparison with those achieved by the Piezosurgery 3 (P<0.0001) and Piezon Master Surgery (P=0.002). Different osteotomy durations were achieved using the different piezoelectric osteotomes: 144 s (Piezosurgery 3), 126 s (Piezosurgery Medical), 142 s (Piezon Master Surgery), 149 s (VarioSurg), and 137 s (Piezotome 2). CONCLUSIONS: In the present study, micromorphological differences following the use of various ultrasonic devices were clearly identified. According to this study, it can be concluded that the power and the composition of the teeth of the insert tip might impact procedure duration and cutting qualities.