Source: Cardiology  |  Posted 5 years ago

By Ed Susman

SAN FRANCISCO, CA -- October 3, 2006 -- Incidence of microbes that are resistant to linezolid (Zyvox) remains low outside the United States, researchers said here at the 46[^]th[] Annual Interscience Conference on Antimicrobial Agents and Chemotherapy, an infectious diseases (ICAAC).

The findings, from the Zyvox Annual Appraisal of Potency and Spectrum Surveillance Program (ZAAPS), were presented on September 30[^]th[].

In the ZAAPS program, researchers collected 14,750 isolates from 16 different countries on 5 continents. More than half the isolates collected were staphylococci.

"The fact that there is more linezolid being used in the United States than abroad appears to be the reason we haven't seen much resistance to this antibiotic," said James Ross, MBA, medical technicians and quality assurance manager, JMI Laboratories, North Liberty, Iowa.

"However, after this abstract was submitted we did find 1 isolate of coagulase negative Staphylococcus that was resistant to linezolid," Ross said at his poster presentation. That isolate was detected in Rome, Italy this year, Ross said. The minimum inhibitory concentration (Cmin) required to control the organism was 8 mcg/mL. Linezolid resistance is defined as a Cmin that is 8 mcg/mL or greater.

"No linezolid-resistant strains were detected in the protocol isolates from the non-USA sample through 2005," Ross reported.

Linezolid continues to show excellent activity with a narrow Cmin range among all 6 Gram-positive subsets that included vancomycin resistant enterococci, methicillin-resistant Staphylococcus aureus, and drug-resistant Steptococcus pneumoniae."

"No trend toward greater linezolid resistance was observed throughout the ZAAPS program," he said.

"As linezolid-resistant isolates emerge in areas of increased exposure -- the United States at this point -- continued surveillance appears prudent and should also include baseline sampling from nations having limited linezolid use," Ross concluded.

[Presentation title: Longitudinal Evaluation of Linezolid Activity: Results From the Zyvox Annual Appraisal of Potency and Spectrum (ZAAPS) Surveillance Program (2002-2005). Abstract E-1849]