[Beta-lactamase producing bacteria in the pharyngeal flora of patients with acute pharyngitis]

Production of beta-lactamase by normal pharyngeal flora could account for penicillin treatment failure in patients with acute streptococcal pharyngitis. The aim of the present investigation was to study the beta-lactamase-producing bacteria (BLPB) in 58 patients with acute pharyngitis, and to investigate the impact of two antibiotics, amoxycillin vs amoxycillin/clavulanic acid in the pharyngeal microflora.

Rapid antigen detection tests for S. pyogenes and standard microbiologic cultures were performed on simultaneously obtained throat swabs from each enrolled patient. Patients with group A streptococcal pharyngitis (GASP) were randomized in two groups: patients treated with 10 days of oral amoxycillin (group I), and patients treated with 10 days of oral amoxicyllin/clavulanic acid (group II). Patients without GASP and without antibiotic treatment were considered as controls (group III). Cultures were repeated 15 days following the first culture. All of them were processed for aerobic and anaerobic organisms.

S. pyogenes was recovered in 25 patients (43.1%) and BLPB were isolated in 64% of the treated patients and in 78% of the non-treated control patients. We observed that the number of patients harboring BLPB did not change significantly in the untreated control group. After treatment we detected a similar increase in the number of patients harboring BLPB in groups I and II. In the present study BLPB were found in more than 70% of the patients and the failure rate was less than 10%.

The results of this study indicate that production of beta-lactamase by pharyngeal organisms does not fully explain the failures of penicillin therapy for acute streptococcal pharyngitis.