Rapid and direct detection of Invivo kinetics of pathogenic bacterial infection from mouse blood and urine

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.

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► The Invivo growth pattern of the pathogenic bacteria was studied in mice.
► This growth pattern had three phases, a lag phase, log phase and decline phase.
► Detection of bacteria by direct MALDI-MS analysis was not feasible.
► Ionic liquid enabled the successful detection of bacteria in blood.
► Direct MALDI-MS of bacteria was easier in urine compared to blood samples.