How calorimetry helps combat antibiotic-resistant bacteria

Researchers and scientists in laboratories are faced today with a critical R&D challenge in the field of antibiotic-resistant bacteria. A new approach, method and technology is at hand to solve this.

The R&D community has until recently lacked a sensitive, label-free cell-based assay possessing the capability to measure bacterial activity in real time with the minimal effort.

Calorimetry-based cell monitoring is uniquely suited to the development of novel antibiotics, as a consequence of the speed, sensitivity and novel insights it generates.

In essence, calorimetry measures the power produced in a cell culture at any given time as Joules/second (W). The heat that is generated is a measurement of the metabolic processes in the cells and, consequently, gives a true phenotype fingerprint of the organism measured.

Calorimetry provides a label-free, non-destructive measurement - making post experimental analysis possible, whilst being independent of sample morphology. This means that tests can be performed both on bacteria in solution, as well as on solid media, including three-dimensional matrices – for example surgical and dental implant materials and bone biopsies

Minor changes in growth behaviour, such as metabolic pathway mutations, are detected, as are biofilm formation and, most significantly, antimicrobial sensitivity.

Calorimetry is a ground-breaking approach for the development of novel antibiotic compounds [and] effective monitoring of the spread of resistant bacterial strains

A growth curve is established equivalent to a traditional growth curve, this forms the basis for determining the effect of antibiotic treatment. Prolonged lag phase is indicative of a bactericidal action, since the starting number of live bacteria will be less, and a decrease in growth rate will suggest a bacteriostatic effect. Dose-response curves, plotting dose against lag time and dose against maximal growth rate, are easily derived from the data.

The formation of biofilms can also be a concern in the potency measurements of antibiotics, since the efficacy of antibiotics differs between planktonic and biofilm growth. Biofilm formation is monitorable by calorimetry as a consequence of the fact that the metabolic status and the treatment efficacy are clearly different.

The heat produced by bacterial metabolism in 3-D matrices can be measured irrespective of the sample properties, thereby enabling new areas of investigation. With the calorimetry technique, bacterial growth assays are performable in both liquid and solid media.

Calorimeter-based assays account only for the actual number of metabolic active, live cells. This in contrast to molecular-based assays, where there can be difficulties distinguishing between the number of live active cells and DNA/protein remaining in inactive/dead cells protected by biofilm.

It is also easy to monitor the metabolic activity for prolonged times using calorimetry - a typical assay will run from just a few hours up to days or weeks if required. This allows for the monitoring of persister cells or cells derived with antibiotic resistance from biofilm formation.

Calorimeter-based assays account only for the actual number of metabolic active, live cells. This in contrast to molecular-based assays, where there can be difficulties distinguishing between the number of live active cells and DNA/protein remaining

Potentiating treatments are being used more regularly so that antibiotic efficacy can be increased. A calorimetric assay can be used to monitor the use of potentiating compounds that have no inherent antibiotic properties and multiple modes of action of combined therapies. Unbiased phenotype screening is achieved since there isn’t any need to know the mechanism of action prior to the experiment,

Summary

Technological advancement has made possible the efficient screening of lead compounds and dose response measurements, with calorimetric tests carried out in a microtiter plate-based format. The 32-channel calScreener technology is a prime example of this. With this innovative technology, throughput is increased by multiple parallel channels, with presterilized single-use consumables that are perfectly suited for bacterial growth in research environments.

Calorimetry is a ground-breaking approach which is ideal for the development of novel antibiotic compounds, as well as effective monitoring of the spread of resistant bacterial strains in life science research. The method is highly-sensitive, fast and cost-effective asset. Combining an indication-based panel of antibiotics with detection, enables scientists to identify the presence of infecting agents and to make a determination on the right antibiotic treatment to apply in hours as opposed to days.

Magnus Jansson is chief scientific officer of SymCel Sverige AB