Centre for New Antibacterial Strategies (CANS) seminar

Dr. Karin Hjort,
Department of Medical Biochemistry and Microbiology,
Uppsala University

Bacterial heteroresistance. What`s behind it and its clinical relevance? 

Monday December 2nd
14:15 – 14:45, MH Aud 2

"Heteroresistance" is a phenomenon where subpopulations of seemingly isogenic bacteria exhibit different susceptibilities to a particular antibiotic. Prevalence of heteroresistance is highly dependent on the exact definition of heteroresistance, and on the methods used for its detection. Furthermore, the connection between heteroresistance and clinical treatment failure is an under-explored research field. In our work, we are taking a broad approach looking at prevalence, mechanisms, and clinical relevance of heteroresistance. For example, we are trying to determine the heteroresistance parameters (i.e. the frequency and/or the resistance level of the resistant subpopulation) that differentiate clinically relevant (i.e. heteroresistance leading to antimicrobial treatment failure) and clinically irrelevant heteroresistance. With such knowledge, an updated definition for heteroresistance based on clinical relevance could be implemented. In addition, we also explore potential new heteroresistance detection methods better adapted to the clinical laboratories. So far, we have observed that heteroresistance is prevalent in clinical strains and often dependent on antibiotic resistance genes present in the resistant isolate. For example, spontaneous amplifications of antibiotic resistance genes were the most common mechanism in a study of Gram-negative bacteria.

Associate Prof. Johan Kreuger,
Department of Medical Cell Biology,
Uppsala University

Development of a new microfluidic method for rapid antibiotic susceptibility testing and a new high-resolution biofilm model using 3D printing 

Monday December 2nd
14:55 – 15:25, MH Aud 2

Prompt and effective antimicrobial therapy is crucial for the management of patients with severe bacterial infections, but is becoming increasingly difficult to provide due to emerging antibiotic resistance. We have to this end developed a multiplex fluidic chip for rapid phenotypic antibiotic susceptibility testing of bacteria. In an initial pilot study, 21 clinical isolates of E. coli, K. pneumoniae, and S. aureus were acquired from the EUCAST development laboratory and tested against panels of antibiotics. The bacterial samples were mixed with agarose and loaded in an array of growth chambers in the chip whereafter bacterial microcolony growth was monitored over time using automated image analysis. Minimum inhibitory concentration (MIC) values were automatically obtained by tracking the growth rates of individual microcolonies in different regions of antibiotic gradients, and stable MIC values obtained within 2-4 hours.

We are also developing a new microfluidic model for high-resolution studies of bacterial biofilms. The new model system provisionally called SLIME (slicer of microbial ecosystems) allows for live imaging of biofilm formation and growth, as well as for precise harvesting of distinct biofilm layers at different depths for further molecular analyses. Data will be presented to suggest that the new model can be used to study population dynamics over time in response to antibiotics using mixed cultures where different strains express distinct fluorescent proteins