Nature | Health

Poor training in use of tests is part of the issue. Microbiology companies could help by revealing the exact composition of their test media, which might help improve understanding of tests' limitations

April 27, 2012

By Daniel Cressey of Nature magazine

Efforts to detect and halt the global spread of drug-resistant bacteria are being hindered by a poor understanding of the limitations of crucial laboratory tests. Because infected patients need to be isolated quickly to avoid spreading infections, the failure to identify antibiotic-resistant pathogens is increasing the risk of untreatable outbreaks, microbiologists argue.

This month at the European Congress of Clinical Microbiology and Infectious Diseases in London, Herman Goossens, director of the Laboratory of Medical Microbiology at the Vaccine and Infectious Disease Institute of the University of Antwerp in Belgium, presented data about one type of commercial kit often used to identify particular drug-resistant pathogens.

The tests contain mixtures of chemicals that encourage some bacteria to grow and discourage others. Samples from stools or rectal swabs are streaked across the growth medium on a plate and then left overnight. The next day, different-colored growths indicate the presence of different species of resistant bacteria.

Under the radar

One type of bacterium that is causing concern carries genetic mutations that cause it to produce carbapenemase enzymes, which confer resistance to carbapenem antibiotics. Health agencies around the world have reported a surge in infections involving carbapenem-resistant bacteria over the past decade. Another worrying mutation produces extended-spectrum -lactamases (ESBLs), which are resistant to cephalosporin drugs.

An example of the difficulties with identifying these bacteria, Goossens says, is a common test for carbapenem-resistant bacteria using plates made by CHROMagar, a microbiology company based in Paris. The plates detect only high levels of carbapenem resistance, meaning that laboratories may fail to detect bacteria with low but clinically important levels of resistance, he says.

See original here:
Drug-Resistant 'Superbugs' Go Undetected