Antibiotic therapy of biofilm-forming groupA streptococcal infections

Abstract number: S523

Baldassarri L.

Streptococcus pyogenes (group A streptococcus, GAS) is responsible for a diverse range of clinical manifestations, from mild skin/soft tissue infections and pharyngitis to more serious manifestations, such as bacteremia, cellulitis, puerperal sepsis, meningitis, pneumonia, and necrotizing fasciitis.

The drug of choice for streptococcal infections treatment still remains penicillin. In fact, the ability of penicillin and its related antibiotics (e.g., amoxicillin) to kill group A streptococci has not changed in more than 50 years and, to date, there has never been a report on a group A streptococcus resistant to this class of antibiotics. On the other hand, macrolide resistance has been showing an increasing trend, with resistance rates which vary considerably in different countries, reaching up to almost 30% in some part of Europe.

Effective treatment is of utmost importance, even for streptococcal pharyngitis, as it is primarily aimed at preventing non-suppurative and suppurative complications and decreasing infectivity.

Even if not frequently, S. pyogenes infections may fail to respond to antibiotic therapy leading to persistent throat carriage and recurrent infections. Such failures cannot always be explained with the occurrence of antibiotic resistance determinants. It was first suggested that erythromycin-resistant S. pyogenes may escape antimicrobial treatment and the host immune response through invasion of epithelial cells. Later, as GAS have recently been shown to be able to form biofilm, and being such character known to provide organisms with an improved antibiotic resistance besides supporting colonization and persistence, biofilm has been suggested as possibly responsible for unexplained treatment failures and recurrences due to susceptible microorganisms.

Preliminary data have shown that biofilm may be produced, and/or up-regulated, in S. pyogenes in response to either antibiotic treatment, other therapeutic molecules or environmental stimuli. In particular, subMIC antibiotic concentrations appear to stimulate biofilm formation; such phenomenon is being observed with increasing frequency for a number of microorganisms, both for biofilm and other virulence factors. The latest findings on what it is known on biofilm produced by S. pyogenes, its possible role in the pathogenesis of streptococcal infections, and on the interactions between antibiotics and other therapeutic molecules and streptococcal biofilm, will be examined.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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