Isolation and identification of Pseudoxanthomonas winnipegensis from blood culture by MALDI-MS

<i>Pseudoxanthomonas</i> is a genus primarily isolated from environmental samples and causes opportunistic infections. In this study, we conducted a detailed investigation of <i>P. winnipegensis</i>, which was isolated for the first time from a blood sample in Japan in 2022, and evaluated five <i>Pseudoxanthomonas</i> species, including <i>P. kaohsiungensis</i>, <i>P. japonensis</i>, <i>P. mexicana</i>, <i>P.</i> sp<i>adix</i> and <i>P. winnipegensis</i>, that cause human infections. However, it is difficult to identify accurately by routine microbiological testing. Our analysis revealed that matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) classification is feasible when using the mass peaks corresponding to ribosomal proteins L29 and L33, as well as the cold-shock protein CspA, as marker peaks. These findings indicate the potential of MALDI-MS for the rapid and reliable detection of <i>Pseudoxanthomonas</i> species in routine microbiological diagnostics.