Use of WASP Touch to study the efficacy of antibiotic combinations

Use of WASP Touch to study the efficacy of antibiotic combinations against beta-lactamase producing Pseudomonas aeruginosa strains

This study is significant because, although there are data to support the activity of this combination against SBL- and MBL-producing members of the Enterobacterales (Enterobacteriaceae group), there is a paucity of data for P. aeruginosa strains that produce these enzymes. 

In the study, aztreonam and ceftazidime–avibactam were tested, alone and in combination, against 5 SBL- and MBL-producing P. aeruginosa strains using broth microdilution MIC methodology and time-kill experiments. None of the 5 strains were susceptible to aztreonam, aztreonam–avibactam, or ceftazidime–avibactam tested individually, but the combination of aztreonam with ceftazidime–avibactam at sub-MIC concentrations demonstrated synergy and produced bactericidal activity in 4/5 (80%) of  strains.

Determination of time-kill curves can be a laborious process but was facilitated in this study by using a Whitley WASP Touch spiral plater to enumerate bacteria at each time point.  This approach substantially reduces the need for agar plates, preparation of serial dilutions and manual plating. 

The study results suggest that the combination of aztreonam and ceftazidime–avibactam may be a viable treatment option against SBL- and MBL-producing P. aeruginosa strains, for which there are very few viable treatment options.

The published paper is available in PDF format at:

https://www.dwscientific.com/storage/app/uploads/public/605/a04/6f0/605a046f07be8207947141.pdf