Bacterial Pneumonia Responds Best to an Antibiotic and Steroid Cocktail

Researchers working with a mouse model of bacterial pneumonia have found that treatment with a combination of antibiotic and corticosteroid was more effective than antibiotic treatment alone in curing the disease.

Mycoplasma pneumoniae causes a relatively benign type of respiratory disease that accounts for 20 to 30% of all community-acquired pneumonia cases. Traditionally, infections with M. pneumoniae are treated with antibiotics. However, while this treatment eliminates the causative agent of the respiratory disease, it does not aid in reducing inflammation and swelling in the lungs.

In a study published in the October 15, 2008, issue of the Journal of Infectious Diseases, investigators at the University of Texas Southwestern Medical Center (Dallas, USA) combined traditional antibiotic treatment (in this study clarithromycin) to kill the pathogenic bacteria with corticosteroid treatment to reduce inflammation.

Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. They are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte levels, and behavior. The steroid used in this study was dexamethasone.

Mice were infected with M. pneumoniae and then separated into separate treatment groups. Different groups were treated with clarithromycin, dexamethasone, combined clarithromycin/dexamethasone, or a placebo daily. The mice were evaluated at the start of the therapy and after one, three, and six days of treatment.

Results showed that while antibiotic therapy with clarithromycin had the greatest effect on reducing concentrations of M. pneumoniae, combination antibiotic/steroid therapy had the greatest effect on decreasing levels of cytokines and chemokines as well as reducing lung inflammation.

"It turns out that the group that got both the antibiotic and the steroids did the best,” said senior author Dr. Robert Hardy, associate professor of internal medicine and pediatrics at the University of Texas Southwestern Medical Center. "The inflammation in their lungs got significantly better. Some people might think that if you give steroids, it would counteract the effect of the antibiotic, but it turns out you need the antibiotic to kill the bug and the steroid to make the inflammation in the lung from the infection get better. The steroids do not kill the bugs, but they do help restore health.”

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University of Texas Southwestern Medical Center