Numerous infections (e.g., bacteraemic urinary tract infections) are due to multiple bacteria (polymicrobial), requiring
a distinct antibiotic dosing regimen. These infections, however, are largely understudied and antibiotic susceptibility
information is inferred from their constituent bacterial isolates. We report a novel technology for determining antibiotic
susceptibility of mixed cultures comprising E. coli, P. aeruginosa, S. aureus, and K. pneumoniae using a multiplexed microfluidic
platform and time lapse fluorescence microscopy (TLFM).
We utilized a 4x12-array microfluidic chip that confines mixed populations of bacteria and antibiotics in 3 nL compartments
enabling automatic quantitative analysis by direct enumeration of individual cells and integration of assay steps in an on-chip
format. We used green and red fluorescent reporters to distinguish the polymicrobial community. Specifically, we employed
the device to compare the minimum inhibitory concentration (MIC) of the bacterial species against commonly used antibiotics
in mixed cultures to the MIC of their constituent bacterial isolates. Interestingly, we observed that the MIC changes drastically
when going from pure to a mixed culture. For example, in a mixed culture of P. aeruginosa and E. coli, the MIC of P. aeruginosa
against tobramycin increased by a factor of 10, while the MIC of E. coli against ampicillin decreased by a factor of 10.
In summary, these results confirm that the susceptibility of bacteria in mixed and pure cultures differs significantly. This
microfluidic platform enables the study of the understudied, yet clinically important field of polymicrobial infections, and it has
potential to be used for diagnosis and rapid determination of the most suitable antibiotic dosing regimen.
Ritika Mohan received her B.Sc degree in Chemical Engineering from the University of Arizona, Tucson. She received her M.Sc in Chemical
Engineering from the University of Illinois, Urbana-Champaign. Currently, she is in the fourth year of her Ph.D. at the same institution. Her current
research efforts are in the area of microfluidics, including the development of pneumatic normally closed microvalves for integrated microfluidics and
microfluidic devices for antibiotic susceptibility testing especially for polymicrobial infections.
Peer Reviewed Journals
Make the best use of Scientific Research and information from our 700 + peer reviewed, Open Access Journals