This study demonstrates the first use of matrix assisted laser desorption/ionization mass
spectrometry (MALDI-MS) to trace the Invivo infection kinetics of the well known deadly
pathogen Staphylococcus aureus in Swiss albino mice. The growth curve of the bacteria from
the point of injection (200 μL of bacterial suspension (108 cfu/mL)) into the mouse blood till
mortality (death) was periodically analyzed using the plate counting method and MALDI-MS.
Bacterial counts of 103 cfu/mL were observed in the log phase of the growth curve in the
blood and 102 cfu/mL were observed in the urine samples. Death occurred in the log phase of
the growth curve, where the bacterial counts showed steady increase. In other cases, the bacteria
counts started decreasing after 48 h and by 96 h the bacteria got totally eliminated from
the mouse and these mice survived. Direct MALDI-MS was not feasible for tracking the bacteria
in the infected blood. However, ionic liquid 1-Butyl-3-methylimidazolium tetrafluoroborate
was successful in enabling bacterial detection amidst the strong blood peaks. But, in the
case of the urine analysis, it was observed that direct MALDI-MS was adequate to enable detection.
The results obtained prove the efficacy of MALDI-MS for analyzing pathogenic bacteria in
clinical samples. This article is part of a Special Issue entitled: Proteomics: The clinical link.