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Resistance to First-Line Antibiotics to Treat Community Acquired Pneumonia Linked to Treatment Failure

TORONTO, CANADA -- October 12, 2006 -- According to study data presented at the Third International Symposium on Resistant Gram-Positive Infections, and recently published in the journal Clinical Infectious Diseases, the class of antibiotics recommended as first-line therapy in Canadian Guidelines for the Initial Management of Community Acquired Pneumonia (CAP) has been linked to treatment failures due to the development of resistance.

The prospective, population-based surveillance study was conducted by the Toronto Invasive Bacterial Diseases Network (TIBDN) over a five-year period. It showed that resistance to macrolides -- the class of antibiotics most often used first-line to fight the Streptococcus pneumoniae bacterium, the most commonly identified cause of serious illness in young children and of CAP in adults –is an important cause of macrolide therapy failure.1

In the past 20 years there have been an increasing number of patients with Streptococcus pneumoniae infections who are failing to recover after treatment with certain macrolides.

"This study shows us that macrolides should be avoided as empirical therapy in certain patients due to emerging resistance issues," says Dr. Donald Low, one of the study investigators and a Toronto microbiologist. "The treatment paradigm is shifting due to new antibiotic resistance trends. Physicians need to assess patients' antibiotic treatment histories as part of their evaluation and consider using the most effective agents first. Taking this approach may help get patients on their feet faster and avoid contributing to growing resistance with the macrolide class of medications."

Despite macrolide-related pneumococcal antibiotic resistance rates in excess of 18 per cent,2 macrolides (erythromycin, azithromycin and clarithromycin) are the class of antibiotics recommended in Canadian guidelines as first-line therapy for pneumococcal infections, including CAP. Respiratory fluoroquinolones (moxifloxacin, levofloxacin and gatifloxacin), oral beta-lactams (amoxicillin-clavulanate + macrolides, cephalosporins + macrolides) and tetracycline (doxycycline) are other antibiotic treatment options recommended in the Canadian guidelines to treat CAP.

About the Study
The study, Macrolide Resistance in Bacteremic Pneumococcal Disease: Implications for Patient Management was a prospective population-based surveillance program of pneumococcal disease in Toronto and Peel regions between January 1, 2000 and December 31, 2004. During the five years of surveillance, 60 out of 1,696 cases of pneumococcal bacteremia (8.5 cases/100,000) were reported as failures of outpatient macrolide therapy. The study found that macrolide resistant bacteria were more commonly isolated in cases that had failed on macrolide therapy compared to all other cases (after failure of non-macrolide antibiotics, or cases that occurred without prior antibiotic therapy) (p< 0.001).

Based on the study results, macrolide antibiotic use should be avoided for patients with known clinical risk factors for macrolide resistance (including patients treated with macrolides within the previous 3 months3,4, patients treated with penicillin or trimethroprim-sulfamethoxazole5,6, extremes of age6, HIV infection5, and exposure to siblings with resistant isolates including children attending daycare7) and for patients residing in areas with high rates of macrolide resistance.

Patients admitted to the emergency department with CAP who are deteriorating despite receiving macrolide therapy should also receive treatment with a different class of antibiotics.

Bayer Inc., the makers of Avelox® (moxifloxacin hydrochloride), an antibiotic in the fluoroquinolone class, was among the companies that supported the TIBDN surveillance through an unrestricted educational grant.


SOURCE: Bayer Healthcare

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