Have you ever called the doctor's office hoping for a quick antibiotic fix for your sore throat, only to be told you'll need a strep test first? Strep can cause rheumatic fever, which is why your doctor wants to launch a quick antibiotic assault—if it is strep that's causing your sore throat. If it's a virus, antibiotics won't help, and taking them only contributes to antibiotic resistance. So if the strep test is negative, your doctor will send you packing. But one doctor, writing in a recent issue of the Annals of Internal Medicine, says this simple strategy, backed by infectious disease specialists and public-health experts, is no longer viable for adolescents and young adults. Robert Centor, an internist and a dean at the University of Alabama School of Medicine, thinks our tight focus on what's best for strep has allowed the resurgence of a deadlier bug that the strep test misses altogether. It's called Fusobacterium necrophorum.
F. necrophorum is a common bacteria in our mouths, digestive systems, and urinary tracts. In the early 20th century, it was widely known for causing a ferocious illness called Lemierre's syndrome. Centor's concern: Thanks to overreliance on the strep test and on conservative antibiotic use, Lemierre's is on the rise again. In this disease, the inflamed throat tissues allow F. necrophorum to pass deep into the neck to the blood vessels, where its toxins clot the blood. The infectious clots can break off and land in the lungs, causing abscesses or lung collapse, or travel to the brain, causing meningitis, encephalitis, or abscesses that require surgery. In either case, death or devastating disability can result. Most patients are from 15 to 30 years old.
It's unclear how many sore throats that fail the strep test are caused by F. necrophorum. Centor cites a Danish study in which researchers found that 29 out of 61 adult sore throat patients tested for F. necrophorum had the bug, more than double its prevalence in healthy people. Lemierre's is relatively rare, but findings like those in the Danish study suggest that a large percentage of strep-negative sore throats are in fact F. necrophorum infections. The bug has already reached a par with better known bacteria as a source of illness. A large study published this spring identified it as the cause of 13.6 percent of ear, nose, and throat infections bad enough to require hospitalization. That compares with 13.7 percent for group A strep. Centor estimates that Lemierre's happens in 1 out of every 400 F. Necrophorum infections, five times as often as strep causes rheumatic fever. By Centor's estimate, the bug also results in 10 times the number of deaths and four times as many disabilities as strep. "These are healthy teenagers, often athletes, living normal lives, who get a sore throat, and the next thing you know they're in the ICU," he says.
This isn't the first time Centor has weighed in on sore throat practice. Nearly 30 years ago, when he was chief medical resident at the Medical College of Virginia, he devised what became the "Centor criteria" for diagnosing strep throat based on examination and symptoms. Back then there was no rapid strep test, and cultures took days to grow. But Centor's clinic saw mostly poor patients without telephones, so relying on follow-up wasn't practical, and the patients who came in were suffering. He started an experiment, studying the patients who visited the clinic in 1980 to see how well four features (fever, lack of cough, pus on the tonsils, and swollen lymph nodes) matched up with culture results. He found that someone with all four symptoms had a 56 percent chance of having verified strep throat.
Centor's old-school criteria are no match for the rapid strep test, widely adopted by the mid-1990s, and its 90 percent accuracy rate. But they are valid for all bacterial infections, not just strep, and patients who display them clearly are in the midst of a full-blown infection. Centor has long argued that doctors are undertreating people with severe sore throats, letting some suffer needlessly without antibiotics. As for the threat of antibiotic resistance, he points to penicillin, which is effective against both strep and F. necrophorum. "Despite over 50 years of penicillin use, we still do not have penicillin-resistant group A beta-hemolytic streptococci," he wrote in the Journal of General Internal Medicine two years ago. The professional organization of internists takes the position that doctors can give antibiotics to somebody with three or four of the Centor criteria. The infectious disease specialists, referring to the danger posed by antibiotic resistance, insist on a positive strep test or culture, regardless of how many signs are present.