Medical: Antibiotic resistance is eons in the making
Bacteria keeps adjusting to antibiotics.
Scripps Howard News Service
It appears that germs are naturally craftier at dodging antibiotics than we've thought.
Bacteria, recent research suggests, have a lot more experience at making adjustments to hostile environments than just the 80 years or so that humans have been trying to quash them with manufactured medicines.
Scientists know that thousands of bacteria carry genes that can code buffering proteins, change cell shapes and perform other tricks to evade antimicrobials.
Canadian researchers recently rolled back the clock on these tools with analysis of bacterial DNA taken from 30,000-year-old permafrost. They found clear evidence of antibiotic resistance.
They contend their discovery counters conventional wisdom that resistance to antibiotics has arisen largely in response to clinical overuse in people and animals.
Writing in the journal Nature, Dr. Gerard Wright of McMaster University in Hamilton, Ontario, and colleagues say their work makes clear that low doses of molecules with antibiotic properties have long been around to influence bacteria, although maybe not kill them.
Still, there's little doubt that widespread exposure to sulfa drugs, penicillin and all that's come after them has sped along the evolutionary process in germs.
It's been an uneven process, shaped by genetics, medical practice and human nature, among other things. Physicians want patients to get better; patients who feel better stop taking their meds. And the surviving bacteria thrive and shrug off the same antibiotic next time.
One way to measure human-germ interactions is to track the extent of antibiotic resistance geographically. Extending the Cure, a Washington-based research group that studies antibiotic resistance, just updated its interactive ResistanceMap tool. It has tracked drug-resistant bacteria across North America and Europe for the past decade.
The maps show that while there have been gains in limiting the spread of methicillin-resistant Staphylococcus aureus bacteria, the U.S. still has one of the highest MRSA rates among developed countries and is far behind most of Europe. Nearly 52 percent of staph samples taken in the U.S. last year were resistant to methicillin, penicillin and related drugs, compared with just 1 percent in Sweden.
There are also clear regional differences in drug resistance within the U.S. For instance, at the end of the decade, nearly 70 percent of staph infections in the Southeast were resistant to methicillin and related drugs, compared to 40 percent of samples taken in New England.
Other research has concentrated on finding where and how drug-resistant germs are likely to be spread.
Hospital settings are a constant concern. A September report in the American Journal of Infection Control found that 60 percent of doctors' and nurses' uniforms collected at a university-affiliated hospital in Israel tested positive for potentially dangerous bacteria. Nearly a third of those were multi-drug resistant strains.
The notion of the contaminated white coat among physicians has been so strong that such garments, and long sleeves in general, were recently banned from British hospitals.
But another report published last February in the Journal of Hospital Medicine, and based on a sampling of Denver physicians, showed that after an eight-hour shift there was no difference in bacterial counts between doctors wearing long- or short-sleeved shirts, or on the skin at their wrists.
On the other hand, another Infection Control report published last spring found that cellphones used by patients and their visitors are twice as likely to harbor drug-resistant germs than those carried by health care workers in the same hospital.
A third study in the same journal last summer took more than a thousand samples from the surfaces of various equipment and furnishings inside firehouses in the Pacific Northwest and, later, from the noses of firefighters in the same region.
Drug-resistant bacteria were found on about 4 percent of all surfaces sampled, from kitchens and fire coats to gyms, although the most common site of contamination was inside ambulances. About a third of the firefighter samples were positive, with most strains genetically tied to the same types of germs found in the firehouses.
(Contact Lee Bowman at BowmanL@shns.com.)
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