Bacterial identification by MALDI-TOF MS

The S. anginosus sputum isolate from sample 009–1 was identified by MALDI-TOF MS as described previously [³²]. In brief, the isolate was cultured on blood agar at 37°C and 5% CO₂. Individual colonies were transferred in duplicate onto a stainless-steel MALDI target using a toothpick. Upon drying at room temperature, 1 μl of a matrix solution, composed of α-cyano-4-hydroxycinnamic acid in 50% acetonitrile/2.5% trifluoro-acetic acid (HCCA), was added to the first spot. For so-called on-target extraction, the second spot was overlaid with 1 μl of 70% formic acid prior to the addition of 1 μl HCCA matrix. The samples were then analyzed with a Bruker microflex MALDI-TOF MS system using the Biotyper 3.0 software (Bruker Daltonik, Bremen, Germany).