Isothermal microcalorimetry provides new insights into biofilm variability and dynamics

Abstract

The purpose of this study was to investigate a three-species in vitro biofilm with peri-implantitis-related bacteria for its variability and metabolic activity. Streptococcus sanguinis, Fusobacterium nucleatum, and Porphyromonas gingivalis were suspended in simulated body fluid containing 0.2% glucose to form biofilms on polished, protein-coated implant-grade titanium disks over 72 h using a flow chamber system. Thereafter, biofilm-coated disks were characterized by scanning electron microscopy and fluorescence in situ hybridization/confocal laser scanning microscopy. To assess metabolic activity within the biofilms, their heat flow was recorded for 480 h at 37 °C by IMC. The microscopic methods revealed that the total number of bacteria in the biofilms varied slightly among specimens (2.59 × 10(4) ± 0.67 × 10(4) cells mm(-2) ), whereas all three species were found constantly with unchanged proportions (S. sanguinis 41.3 ± 4.8%, F. nucleatum 17.7 ± 2.1%, and P. gingivalis 41.0 ± 4.9%). IMC revealed minor differences in time-to-peak heat flow (20.6 ± 4.5 h), a trend consistent with the small variation in bacterial species proportions as shown by microscopy. Peak heat flow (35.8 ± 42.6 μW), mean heat flow (13.1 ± 22.0 μW), and total heat over 480 h (23.5 ± 37.2 J) showed very high variation. These IMC results may be attributed to differences in the initial cell counts and relative proportions of the three species, their distribution and embedment in exopolysaccharide matrix on the test specimens. The present results provide new insights into variability and dynamics of biofilms on titanium disks, aspects that should be explored in future studies of dental surfaces.

Activities of Fosfomycin, Tigecycline, Colistin, and Gentamicin against Extended-Spectrum-β-Lactamase-Producing Escherichia coli in a Foreign-Body Infection Model

“…Measurements were performed in an isothermal 48-channel batch calorimeter (thermal activity monitor, model 3102 TAM III; TA Instruments, New Castle, DE), calibrated at 37°C Ϯ 0.00001°C with a lower limit of heat-flow detection of 0.25 W. All experiments were performed in triplicate. The minimal heat inhibition concentration (MHIC) was defined as the lowest antimicrobial concentration inhibiting heat production with a delay of Ն24 h, as previously described (25,32).…”

Novel microcalorimetric assay for antibacterial activity of implant coatings: The cases of silver‐doped hydroxyapatite and calcium hydroxide

“…This is even truer considering the variability of metabolic activities in biofilms. 3 Nowadays a commonly used surface coating for implant is hydroxyapatite (HA). This biomaterial offers good biocompatibility and HA coated implants have been shown to have good functional results over more than 20 years.…”

“…Bacterial growth at the surface of the coating or in the pores of an open-porous scaffold can then be monitored and analyzed using the heat dissipated through the bacterial metabolism. 3,[16][17][18][19] As only heat production is measured by a peltier element placed between the sample container and the heat sink, solid sample can be analyzed easily. Indeed, previous studies have shown that growth and antimicrobial activity could be determined accurately in solid medium using IMC 20,21 or gels.…”

Development of a flow system for studying biofilm formation on medical devices with microcalorimetry

“…Staphylococcus aureus growing on human and bovine bone grafts, while AstasovFrauenhoffer et al [31] investigated variability and dynamics of a triple-species biofilm and determined efficacy of amoxicillin and metronidazole combinations against biofilms of various species [32]. Said et al [33] determined the efficacy and mechanism of action of an anti-biofilm wound dressing.…”