Carbapenem susceptibility test results widely variable, study finds
A study by Italian investigators in Clinical Microbiology and Infection has found that commercial methods for testing carbapenem susceptibility produced widely variable results in a sample of carbapenemase-producing Escherichia coli, with none satisfying the criteria for acceptable antimicrobial susceptibility testing (AST) performance.
In the study, the researchers tested a total of 54 non-replicate Klebsiella pneumoniae carbapenemase (KPC)-producing E coli isolates from two Italian hospitals for susceptibility to imipenem, meropenem, and ertapenem. They used the broth microdilution method (BMD) as a reference and several commercial testing systems (Vitek2, MicroScan, Etest, MIC Test Strip). Susceptibility to imipenem and meropenem was also tested by Sensititre and disk diffusion (Bio-Rad).
Results were interpreted according to EUCAST (European Committee on Antimicrobial Susceptibility Testing) clinical breakpoints. Essential agreement (EA), category agreement (CA), and error rates were calculated as described by the International Organization for Standardization (ISO) guidelines and also considering the new EUCAST definitions.
Reference BMD results showed that, of the 54 KPC-positive E. coli isolates, 5.6%, 7.4%, and 0% were susceptible to the standard dosing regimen, 55.6%, 72.2%, and 0% were susceptible to increased exposure, and 38.9%, 20.4%, and 100.0% were resistant to imipenem, meropenem and ertapenem, respectively. CA lower than 90% was observed with all systems for imipenem and meropenem, using both the ISO and the modified EUCAST criteria. With ertapenem, CA greater than 90% was observed with all methods except Vitek2. Overall, for commercial methods returning minimum inhibitory concentration (MIC) values and for all molecules, the EA with the reference method was relatively low, with no method being acceptable according to the ISO criteria.
"This study suggests that, whatever semiautomated AST systems are used for testing KPC-producing E. coli, laboratories should always confirm carbapenems MICs with reference BMD in order to carry out an appropriate antimicrobial therapy," the authors of the study conclude.
Aug 16 Clin Microbiol Infect study
New Australian AMR hub launched
The Australian Research Council (ARC) yesterday announced nearly $3.4 million in funding for a new antimicrobial resistance research center.
The ARC Research Hub to Combat Antimicrobial Resistance, which will focus on sexually transmitted microorganisms, aims to develop new technology to fight drug-resistant pathogens and guide investments in new antibiotics and diagnostics. The hub will bring together Australian universities, pharmaceutical and diagnostics companies, and healthcare partners and be led by Rebecca Guy, PhD, a professor of epidemiology the University of New South Wales.
"We plan to develop new molecular diagnostic technology and improve the processes for identifying potential new antibiotics," Guy said in a university press release. "The hub aims to connect the many complex facets of antimicrobial resistance, to provide a highly integrated diagnostic and pharmaceutical solution to the problem of antimicrobial resistance."
The ARC is contributing almost $5 million Australian ($3.4 million US) to the project. An additional $3.8 million Australian ($2.6 million US) is being provided by Australian-based biotech company SpeeDx and other industry partners.
Aug 18 ARC press release
Aug 19 University of New South Wales press release