A primer on use of inkjet printing and time-kill studies for combination antimicrobial susceptibility testing
Adopted by the CDC .in their Antimicrobial Resistance Laboratory Network based on our prior publications in Journal of Clinical Microbiology, Journal of Antimicrobial Chemotherapy, and Antimicrobial Agents and Chemotherapy for testing of aztreonam/ceftazidime-avibactam combination activity using inkjet printing. We provide a step by step video demonstration of assay setup in the Journal of Visualized Experimentation. Link to article landing page (PDF protocol access and video), "Antimicrobial Synergy Testing by the Inkjet Printer-assisted Automated Checkerboard Array and the Manual Time-kill Method" by Thea Brennan-Krohn and James E. Kirby.
"New Treatment Options against Carbapenem-Resistant Acinetobacter baumannii Infections" cites our preclinical studies on apramycin
"New Treatment Options against Carbapenem-Resistant Acinetobacter baumannii Infections" cites our murine apramycin PK/PD studies and activity spectrum studies against "CRAB.".
Gentian violet is diluted in hollow fiber cassette with a half life of approximately 4 hours based on dilution of initial "dose" in central compartment with fresh media at flow rate selected on peristaltic pump. Next two antibiotics with different half lives. Will the bacteria outside the hollow fibers survive and for how long?
BIDMC news release on Thea's antimicrobial synergy paper:
"Bacteria—especially Gram-negative strains—are becoming increasingly resistant to current antibiotic drugs, and the development of new classes of antibiotics has slowed. Faced with these challenges, investigators are studying the potential of combination therapy, in which two or more drugs are used together to increase or restore the efficacy of both drugs against a resistant bacterial pathogen. Now new research indicates that such synergy may work even when bacteria become resistant to colistin, which is considered a treatment agent of last resort.
The findings are especially promising because recent evidence indicates the potential for rapid worldwide spread of colistin resistance. “For an infected patient, if the multidrug-resistant Gram-negative bacterial pathogen is resistant to colistin, then there is a big problem,” said senior author James Kirby, MD, Director of the Clinical Microbiology Laboratory at BIDMC.
In their Antimicrobial Agents and Chemotherapy study, Kirby and his colleagues Thea Brennan-Krohn, MD and Alejandro Pironti, PhD screened 19 different antibiotics for synergy with colistin. The team discovered several combinations where synergy was present and infections with resistant pathogens could potentially be treated with the combination therapy.
Of particular interest, colistin demonstrated high rates of synergy with linezolid, fusidic acid, and clindamycin, which are protein synthesis inhibitor antibiotics that individually have no activity against Gram-negative bacteria. “It was remarkable to see two drugs, each of which is inactive on its own against these bacteria, inhibiting them in combination,” notes Brennan-Krohn. “These findings suggest that colistin retains sub-lethal activity against colistin-resistant bacteria, which may enable drugs like linezolid to reach their targets.”
“Faced with highly resistant pathogens, clinicians often currently treat with multiple antibiotics without knowing the benefit the combinations may provide,” said Kirby. “This study now provides some scientific underpinning for these choices and direction for future investigation.” He added that combination therapy may also allow clinicians to use lower effective doses of colistin and other drugs, which would help avoid toxicities associated with the medications as well as slow the development of antibiotic resistance.
This work was funded in part with Federal funds from the National Institute of Allergy and Infectious Diseases, the National Institutes of Health, and the Department of Health and Human Services."
.On acceptance of her manuscript by the Journal of Antimicrobial Chemotherapy:
Brennan-Krohn T, Truelson KA, Smith KP, Kirby JE. Screening for synergistic activity of antimicrobial combinations against carbapenem-resistant Enterobacteriaceae using inkjet printer-based technology. J Antimicrobial Chemotherapy. 2017 July.
Link to abstract. Link to Journal Full Text.
BIDMC issued a press release on our manuscript on at-will antimicrobial susceptibility testing performed using a digital dispensing method. "Simple Method Quickly Tests Hard-to-Treat Bacteria’s Susceptibility to Different Antibiotics".
The original article is now available online at: http://www.ncbi.nlm.nih.gov/pubmed/27335151
There has been a lot of attention paid recently to plasmid-borne colistin resistance. The presence of MCR-1 gene has now been examined in large collections of clinical bacterial isolates obtained during the past few years. Perhaps not surprisingly the MCR-1 gene was present at low frequency.
Here is a link to the CNN interview about MCR-1. I also indicated in my discussion with the CNN the need for improved diagnostics, but that did not make it into the article.
Kirby Lab Blog