Results from a double-blind study published in the June issue of Chest, the use of clarithromycin increases forced expiratory volume (FEV1) in patients with bronchial asthma with positive polymerase chain reaction (PCR) result on Mycoplasma pneumoniae or Chlamydia pneumoniae.

According to researchers at the National Jewish Medical and Research Center in Denver, Colorado, antibiotics can be an important addition to the treatment of some patients with bronchial asthma.

In 55 patients with moderate to severe bronchial asthma, examination of several tissue samples from the upper and lower respiratory tract by the cultural method gave a negative result. However, PCR detected the DNA of M. pneumoniae or C. pneumoniae in 31 patients (56%) in this group.

The diagnosis of chlamydia and mycoplasma infections is quite complicated, and today very few centers are able to perform all the necessary tests. Therefore, scientists are developing simpler methods to diagnose such infections.

Before starting antimicrobial therapy, FEV1 was similar in patients with positive and negative PCR results. Without stopping the standard asthma treatment, the patients were randomized into a placebo group and a clarithromycin 500 mg group twice daily for 6 weeks.

In patients with negative PCR who received clarithromycin, there was no significant change in lung function, while the mean FEV1 in patients with positive PCR increased by 200 ml. According to the researchers, this is a clinically significant improvement, as evidenced by the patients' subjective feelings.

Despite this improvement, presumably associated with a decrease in the level of pro-inflammatory cytokines, the researchers do not recommend the widespread use of antibiotics for the treatment of bronchial asthma. Standard drug therapy for this disease is sufficient to control symptoms in most patients, and excessive use of antibiotics leads to the emergence of resistant strains of microorganisms. Nevertheless, tests should be performed to identify bacterial infections in patients with bronchial asthma, which does not lend itself to standard drug therapy, and antimicrobial chemotherapy should be performed if signs of lung infection are obtained.