The rise of antibiotic-resistant bacteria is growing at an alarming rate. New studies show that the single test – used for the past 50 years – to decide how to treat stubborn infections may be severely out-of-date.
The findings of a study conducted by Michael J. Mahan, a professor of microbiology at the University of California, Santa Barbara, may have huge implications for how doctors decide to treat those patients infected with superbugs. “We’re saying the standard way the world does this is wrong.”
His theory is that the standard test used to determine what antibiotics may work against a certain bacteria has holes. Presently, labs use a solution called Mueller-Hinton broth in which to grow the infecting bacteria. Then scientists attack the bacteria with various antibiotics to determine which one works best. This test is used around the world. Mahan points out, however, that the bacteria infecting live patients attack human cells – not the cells found in the broth. By changing the growth environment, the bacteria may react differently to certain antibiotics.
The study involved testing the salmonella bacteria in the Mueller-Hinton broth as well as in a solution that more closely resembles human cells. The findings indicate that the bacteria reacted differently to certain antibiotics in each solution. So, while a doctor may determine that an antibiotic would not be a good choice for a patient with a certain bacterial infection – as determined by the Mueller-Hinton test – he could be wrong.
Another recent study led by Victor Nizet, showed similar results. He observed that the traditional, standard test has “nothing to do with the patient. The patient’s not made out of Mueller-Hinton broth.”
Scientists and researchers know that the recent studies may have enormous impacts on how doctors choose which antibiotics to prescribe a patient. Stanley Maloy, dean of the college of sciences at San Diego State, points out that, “It’s really clear from these papers that there are key examples where the way we’ve been doing things up until now is probably inadequate. It is a very big shift.”
Still, it may be a while before new tests are used in hospitals. Mahan said that hospital labs could easily expand their procedures to include testing difficult-to-treat bacteria in the kind of solution he used – in addition to the standard Mueller-Hinton broth. However, Dan, Andersson, a professor of medical bacteriology at Uppsala University in Sweden notes that, “There are many things that clinical microbiology labs in principle could do, but they don’t do because it’s too complicated and too expensive.”
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