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Carbapenems Still Effective Against Most Microbial Isolates: Presented at ICAAC

By Ed Susman

SAN FRANCISCO, CA -- October 3, 2006 -- Antibiotics in the carbapenem class continue to be effective against most Gram-negative microbes responsible for bacteremia and pneumonia, researchers said here at the 46^th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

The carbapenems continued to show the widest overall antimicrobial activity among the broad spectrum agents tested in the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program, according to Paul Rhomberg, BS, laboratory manager, JMI Laboratories, North Liberty, Iowa, in a poster presentation on September 30^th.

"These drugs still work fairly well against most of the isolates we tested," Rhomberg said. He added that meropenem was more potent against Pseudomonas aeruginosa and other nonfermentors than was imipenem, but was less potent against Acinetobacter species as well as Staphylococci and Streptococci isolates.

The MYSTIC program tested drugs against 20,041 isolates between 1999 and 2006.

"Susceptibility and resistance rate trends among all Gram-negative bacilli tested in the United States MYSTIC program have generally remained stable from 1999 to 2006, except for a very recent decrease in carbapenem susceptibility among Enterobacteriaceae isolates. The greatest increase in resistance rates was detected for fluoroquinolones -- ciprofloxacin and levofloxacin," Rhomberg said.

He noted that the carbapenem agents have been the recommended drug of choice for treating Gram-negative bacilli which have become resistant to aminoglycosides, cephalosporins, and fluoroquinolones. However, he said resistance to the carbapenems has been noticed -- first in the nonfermenting Gram-negative bacilli and then in Enterobacteriaceae.

"Continued surveillance is warranted to monitor the activity of the carbapenems and comparator broad-spectrum antimicrobial agents within the clinically important Gram-negative bacilli," Rhomberg said.

The MYSTIC Program is a global longitudinal surveillance network of more than 100 medical centers actively using carbapenems that monitors the activity of meropenem and alternative broad-spectrum agents against pathogens collected from hospitalized patients. In the United States, 15 centers submit up to 200 clinical isolates each year from serious infections.


[Presentation title: Eight-Year Trends in Carbapenem Resistance Rates in the MYSTIC Programme (USA; 1999-2006). Abstract C2-1833]

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