Tonsillitis is a common disease of childhood and adolescence. The diagnosis of tonsillitis generally requires the consideration of Group A beta-hemolytic Streptococcus (GABHS) infection. However, numerous other bacteria alone or in combinations, viruses and other infections and non-infectious causes should be considered. Recognition of the cause and choice of appropriate therapy are of utmost importance in assuring rapid recovery and preventing complications.

Penicillin is currently the first-choice treatment for GABHS pharyngotonsillitis. However, the growing failure of penicillin to eradicate GABHS is of concern. This website discusses the potential causes of penicillin failure ( i.e. the presence of beta-lactamse producing bacteria that can “protect” GABHS from penicillins) and methods to overcome them. It also discusses the role of anaerobic bacteria in tonsillitis and its complications.

Saturday, February 18, 2012

Why does penicillin not work in Group A streptococcal tonsillitis?

Despite its excellent efficacy in the test tube, penicillin frequently does not work and fail to eradicate Group A beta-hemolytic streptococci (GABHS) from patients with acute and relapsing pharyngo-tonsillitis (PT) is cause for concern.  Over the past 50 years, the rate of penicillin failure has consistently increased from about 7% in 1950 to almost 40% in 2000.

Various explanations exist for the failure of penicillin to eradicate GABHS PT (see page).  One possibility is the poor penetration of penicillin into the tonsillar tissues as well as into the epithelial cells. Other explanations relate to the bacterial interactions between GABHS and other members of the pharyngo-tonsillar bacterial flora.  For example, it is hypothesized that beta-lactamase secreted by beta-lactamase-producing bacteria (BLPB), which colonize the pharynx and tonsils, may “shield” GABHS from penicillins. Another possibility is the coaggregation between Moraxella catarrhalis and GABHS, which can facilitate colonization by GABHS. Normal bacterial flora can interfere with the growth of GABHS, and the absence of such competitive bacteria makes it easier for GABHS to colonize and invade the pharyngo-tonsillar area.

Beta-lactamase producing organisms "protecting" penicillin susceptible bacteria from penicillin

Therapeutic strategies that allow overcoming the above mechanisms are available and are based on extensive clinical research. This website describes the research and therapeutic option for patients who fail penicillin therapy.  

Streptococcal tonsillitis