Hollow-fibre infection model: adaptations for the culture and assessment of fastidious organisms

The Hollow-fibre Infection Model (HFIM) is a valuable in vitro platform for emulating antimicrobial drug (AMD) pharmacokinetic (PK) profiles. Despite its potential, standardized protocols for HFIM operation, especially concerning fastidious organisms, are lacking. This study addresses this gap by examining challenges in culturing Pasteurella multocida and Actinobacillus pleuropneumoniae, two fastidious organisms, in the HFIM. Our findings reveal effective strategies to prevent system clogging, involving multiple freeze-thaw cycles of horse blood, centrifugation, and cell straining to enhance the clarity of the Mueller-Hinton fastidious (MH-F) medium defined by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical and Laboratory Standards Institute (CLSI). Additionally, we propose that the provision of a CO2 atmosphere, along with the utilization of gas-permeable tubing and gas vent filters, significantly facilitates the growth of fastidious organisms. Remarkably, both P. multocida and A. pleuropneumoniae were sustained for a period of up to 10 days under these optimized conditions. This study provides crucial insights into the modifications necessary to successfully culture fastidious organisms in the HFIM, paving the way for more accurate and representative in vitro models for antimicrobial drug testing. These advancements hold promise for advancing research in the field of antimicrobial pharmacokinetics and efficacy against challenging pathogens.