Evaluation of acute period bacterial infecton by XN-V software of automated hematology analyzer for animal in rats

<p>[Purpose/Background] In the treatment of bacterial infections, appropriate selection of antibiotics is crucial to prevent the emergence of drug-resistant bacteria. Gram staining and culture tests are performed to identify causative bacteria, but in clinical practice, rapid and convenient testing methods are needed. Therefore, we evaluated whether it is possible to discriminate causative bacteria from the results of XN-V (Sysmex Corporation) .[Methods] Staphylococcus aureus (Sa) and Escherichia coli (Ec) were selected. A bacterial solution was prepared at a concentration of 1.0 x 10^9 cfu/mL and administered to rats (Slc:SD, 9 weeks old) via i.p. The rats were evaluated at days 1, 3, and 6 after administration using hematological tests and histopathological tests.[Results] On day 1, lymphocyte counts decreased by more than 40% compared to day 0 in Sa, while Ec decreased by less than 10% on average. Furthermore, in the WDFch scattergram of XN-V, Sa had more high-fluorescence neutrophils than Ec, and the ratio was also higher than that of Ec. In the morphological evaluation of smear samples, immature neutrophils were observed more frequently in Sa, while segmented nuclear neutrophils were dominant in Ec. Histopathologically, inflammatory reaction was mainly due to mononuclear cell infiltration, especially in the spleen, and the severity was higher in Sa than in Ec. These reactions decreased over time in both Sa and Ec and were almost fully recovered by day 6.[Discussion] Differences between Sa and Ec were observed in the acute phase of bacterial infection and it was found also in XN-V results. In the future, the possibility of estimating causative bacteria based on XN-V measurement results may be suggested by systematizing reactions according to the infection stage and bacterial species.</p>