Streptococcus pyogenes: susceptibilidad in vitro y papel de las bacterias productoras de betalactamasa en la persistencia de la faringoamigdalitis estreptocócica

Abstract

To assess the frequency of association between Streptococcus pyogenes and beta-lactamase-producing-bacteria in the pharyngotonsillitis and the evaluate the in vitro susceptibility. Prospective, descriptive, transverse study. The present study was carried out in the Health Center Dr. José Castro Villagrana, in Tlalpan, México, D.F., from Juanary, 1996 to February 1999. In three hundred and ninety four patients with pharyngotonsillitis diagnosis we isolated the same number of Streptococcus pyogenes, and possible beta-lactamase-producing-bacteria. In 180 patients (45.7%) we isolated at least one possible beta-lactamase-producing-bacteria. Of these, in 138 patients (35%) were confirmed the enzyme presence. In total, we isolated 218 possible beta-lactamase-producing bacteria, and 152 (69.7%) were beta-lactamase positive. We found no significant change in the in vitro susceptibility of group A Streptococcus to penicillin, but erythromycin resistance is relatively common, approximately 10% in this study. Streptococcus pyogenes was uniformly susceptible to all penicillins and cephalosporins in vitro. Erythromycin treatment should not be promoted as first-line therapy because the consequent increase of bacterial resistance could create difficulty in treating penicillin-allergic patients. Because of the poor activity of trimetoprimsulfametoxazol, this drug no longer can be considered the drug of choice for the management of group A Streptococcal infections.