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WEDNESDAY, April 7 (HealthDayNews) -- Two new studies shed light on the latest thinking about diagnosing and treating strep throat.

Strep throat is caused by Streptococcus bacteria and is the most common bacterial infection of the throat. It is a common condition in children and can also infect adults. While the condition is usually harmless, it can lead to complications, especially in children.

Strep usually responds well to antibiotics. However, the overuse of antibiotics to treat common sore throats has resulted in strep becoming resistant to some drugs.

In the first study, Dr. Warren J. McIsaac, from the department of family medicine at Mount Sinai Hospital in Toronto, and his colleagues looked at the various ways doctors diagnose strep.

The research team looked at throat cultures and rapid antigen tests that detect strep, from 787 children and adults with acute sore throat. The team then compared the value of these tests along with diagnostic protocols to determine the best way to find strep.

They report their findings in the April 7 issue of the Journal of the American Medical Association.

McIsaac said that depending on whether you wanted to reduce the use of antibiotics or find all the cases of strep, the best diagnostic methods varied. "There was no one best way to do this," he added.

The standard approach has been to take a throat culture in everyone with a sore throat to find all the cases of strep. Recently, the need to take a throat culture on everyone has been questioned and the use of rapid antigen tests has been promoted.

Based on their analysis, McIsaac said that he believes that any child with a positive rapid test for strep should be given antibiotics. In addition, those with a negative test should then have a throat culture.

For adults, McIsaac recommends that a positive rapid test alone is enough to find most cases of strep, but clinical presentation also needs to be taken into account.

There is more than one way to evaluate patients for strep throat, McIsaac said. Doctors, he added, should use one method and stick with it, "because this is the only way to reduce antibiotic use."

Dr. Robert S. Baltimore, a professor of pediatrics, infectious diseases and epidemiology/public health at Yale University, said that "treating only those with a positive rapid test or culture is best in terms of reducing unnecessary use of antibiotics."

In addition, recommendations that suggest treating all adults with a high probability of strep based on clinical presentation may result in overuse of antibiotics, Baltimore said.

The second study, which is in the April issue of the journal Pediatrics, challenges the notion that penicillin is the best way to attack strep throat in kids.

A team led by Dr. Janet R. Casey, a pediatrician at the University of Rochester, looked at 35 studies done since 1969 that compared antibiotic use for treating strep throat in children.

"We found that antibiotics called cephalosporins outperformed penicillin," Casey said. "Penicillin had a greater than three times likelihood of failing compared with cephalosporins."

Over the years there has been increasing bacterial resistance to penicillin. "I don't think penicillin should be abandoned," Casey said, "but cephalosporins should be an option that doctors can use to treat strep throat."

Although penicillin kills strep, other bacteria that live in the mouth and throat normally may have developed a resistance to the drug, which weaken its ability to fight the bug, Casey noted.

Casey recommends that doctors use what are called first-generation cephalosporins, such as Cephalexin and Cefadroxil, on patients for whom penicillin does not work. However, these drugs can also be used from the start, she added.

Baltimore pointed out that many normal children carry Streptococcus in their throats when they are well. "This is not a health problem and they do not require treatment."

Therefore, "the American Academy of Pediatrics does not believe that the more expensive and broader spectrum cephalosporins need to be used routinely," he said.

Baltimore also noted that this study mixed children with strep throat with those who carry the strep bacteria normally.

"Since eradication of symptoms is a minor issue in treatment of strep throat, because symptoms abate by themselves, it is difficult to draw any conclusion about their data on clinical outcome after therapy," he said.

More information

MedlinePlus can tell you all about strep throat, while the National Institute of Allergy and Infectious Diseases can tell you more about antibiotic resistance.

(SOURCES: Janet R. Casey, M.D., department of pediatrics, University of Rochester, Rochester, N.Y.; Warren J. McIsaac, M.D., M.Sc., department of family medicine, Mount Sinai Hospital, Toronto; Robert S. Baltimore, M.D., professor of pediatrics, infectious diseases and epidemiology/public health, Yale University, New Haven, Conn.; April 7, 2004, Journal of the American Medical Association; April 2004 Pediatrics)

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