Volume 16, Issue 1, Pages 57-62 (June 2009) Fast detection of bacterial growth by using Portable Microbe Enrichment Unit (PMEU) and ChemPro100i® gas sensor  Elias Hakalehto, Jouni Pesola, Anneli Heitto, Brajesh Bhanj Deo, Kari Rissanen, Ulla Sankilampi, Tarmo Humppi, Heikki Paakkanen  Pathophysiology  Volume 16, Issue 1, Pages 57-62 (June 2009) DOI: 10.1016/j.pathophys.2009.03.001 Copyright © 2009 Elsevier Ireland Ltd Terms and Conditions

Fig. 1 Portable Microbe Enrichment Unit (PMEU). Pathophysiology 2009 16, 57-62DOI: (10.1016/j.pathophys.2009.03.001) Copyright © 2009 Elsevier Ireland Ltd Terms and Conditions

Fig. 2 The schematic presentation of the connections of the ChemPro100i® Chemical Detector. Total flow rate through the detector was 1.3l/min and the flow rates were around 60ml/min, measured with a TSI 4140 C mass flowmeter. Total sampling flow to the detector was kept constant (300ml/min) and the rest of the air to the detector was taken through an NBC-filter to maintain the background air level as constant. Pathophysiology 2009 16, 57-62DOI: (10.1016/j.pathophys.2009.03.001) Copyright © 2009 Elsevier Ireland Ltd Terms and Conditions

Fig. 3 Hospital infection strains isolated from the NICU patients of Kuopio University Hospital (KUH) and bacterial model strains incubated in the PMEU in BHI medium. Strains KUH 57, KUH 81, KUH 262 and KUH 465 were incubated in CO2 enriched atmosphere (5% CO2, 19% O2, 76% N2) while other strains were incubated aerobically. The initial bacterial concentration was approximately 1×10E6cfu/ml. Bacterial growth led to evaporation of metabolic substances which were detected by the semiconductor sensor of the ChemPro100i®, and presented as curves indicating the emissions as a function of cultivation time. BHI broth was used as a negative control. The figures in the Y-axis indicate the amount of the evaporated substances in Chempro units. Emission curves of (a) Klebsiella mobilis strain ATCC 13048, (b) Staphylococcus aureus hospital strain KUH 262 and laboratory strain SA 3, (c) Staphylococcus epidermidis hospital strains KUH 434, KUH 464 and KUH 465, (d) coagulase negative Staphylococcus sp. hospital strain KUH 57 and (e) Streptococcus agalactiae hospital strain KUH 81. Pathophysiology 2009 16, 57-62DOI: (10.1016/j.pathophys.2009.03.001) Copyright © 2009 Elsevier Ireland Ltd Terms and Conditions

Fig. 4 ChemPro100i® graphs of cultures 1 (a: E. coli) and 3 (b: S. aureus) started from pure cultures with initial bacterial concentrations of 600 and 150cells per ml, respectively, cultivated in the PMEU unit with aerobic atmosphere at 37°C. The first signs of E. coli growth were detected at 4–5h from the onset of the cultivation. The enrichment of S. aureus produced a strong biphasic response with the first peak at 2h and the second at 7–8h. The figures in the Y-axis indicate the amount of the evaporated substances in Chempro units. Pathophysiology 2009 16, 57-62DOI: (10.1016/j.pathophys.2009.03.001) Copyright © 2009 Elsevier Ireland Ltd Terms and Conditions