Susceptibility of group A beta-hemolytic Streptococcus isolates to penicillin and erythromycin

Abstract

We have reevaluated the antibiotic susceptibilities of group A beta-hemolytic streptococci in view of recent reports of a high prevalence of erythromycin resistance in Japan and of an increase in penicillin treatment failures in the United States. A total of 474 isolates recovered during a 2-to 3-month period in 1980 were tested. All were susceptible by microtiter broth dilution to a penicillin concentration of c0.03 ,ug/ml (minimal inhibitory concentration), and 473 were killed by c0.06 ug/ml (minimal bactericidal concentration). Erythromycin minimal inhibitory concentrations showed a bimodal distribution: 95% were -0.06,tg/ ml, and 5% were 21 ,ug/ml. Of the minimal bactericidal concentrations, 21% were 21 ,ug/ml and 3% were :16 ug/ml. Group A beta-hemolytic streptococci remain susceptible to the inhibitory and bactericidal actions of penicillin, thus providing no in vitro explanation for the bacteriological relapses reported in some clinical studies. Unlike the Japanese experience, only 5% of our isolates were resistant to erythromycin (minimal inhibitory concentration, 21 ug/ml); however, 22% were tolerant (ratio of minimal inhibitory/bactericidal concentrations, 232).Although in vitro resistance to penicillin has not been described for group A beta-hemolytic Streptococcus, a trend of increasing resistance to erythromycin has been reported (2-4, 9). Recently some clinicians have noted an increased incidence of treatment failure as compared with data relating to treatment results derived 2 decades ago (6,7,(10)(11)(12)14). In view of these findings, we have evaluated antibiotic susceptibilities of group A beta-hemolytic Streptococcus strains recently isolated from patients in Oklahoma.MATERIALS AND METHODS Group A beta-hemolytic Streptococcus isolates. Throat cultures submitted to the microbiology laboratories of Oklahoma Children's Memorial Hospital and the Oklahoma State Department of Health yielded 474 group A beta-hemolytic Streptococcus (S. pyogenes) isolates. Isolates originated, geographically, from a statewide region. Serogroup identification was based on the fluorescent-antibody technique, and hemolysis was determined by macroscopic examination of primary streak plate cultures containing 4 to 5% defibrinated sheep blood. Inocula were stabbed to facilitate detection of oxygen-labile hemolysin. Plates were incubated at 35 to 370C in an atmosphere containing 6% C02 and were examined at 24 and 48 h.Group A beta-hemolytic Streptococcus colonies were transferred to blood agar plates and maintained in pure culture at room temperature until susceptibility tests were performed. Susceptibility testing. Growth from 18-to 24-h cultures on sheep blood agar plates was adjusted to a density of approximately 10' colony-forming units per ml in Mueller-Hinton broth. A 1:10 dilution was then made in 5 ml of broth for micro-broth dilution testing, or a 1:20 dilution was made before agar dilution testing. Agar dilution tests were performed on antibiotic-supplemented Mueller-Hinton agar containing 5% sheep blood. Inoculati...

Antibiotic susceptibility of group A streptococci: a 6-year follow-up study

“…Our results are similar to those reported by others (5,20); in 1987 the results obtained (2) were almost identical. Amoxicillin-clavulanic acid displayed unaltered activity against GAS isolates over the study period, with MICs for 90% of isolates ranging from 0.06 jg/ml in 1990 to 0.015 ,ug/ml in all of the other years.…”

“…While in vitro resistance to penicillin has not been described for GAS strains, resistance to erythromycin has been reported. Since 1959, when the first erythromycin-resistant GAS was described by Lowbury and Hurst (9), resistance to this antibiotic has been reported from several countries, with important variations in the resistance rates in different geographic areas; in 1979, Maruyama et al (10) in Japan reported erythromycin resistance in 61.8% of GAS isolates, and in other parts of the world erythromycin-resistant GAS strains have occasionally been isolated, with resistance rates ranging from 0.7% (13) to 2 to 5% (1,5,6,16,19,20). In the last 5 years, an increased incidence has been reported from several centers (14,15,17,21).…”

Decreased activity of erythromycin against Streptococcus pyogenes in Taiwan

“…For the isolates in the United States and Europe for which erythromycin MICs were high the MICs of clindamycin were still low (3,5,6,10,11,(20)(21)(22)24). Because of this, clindamycin has been recommended as a drug of choice secondary to erythromycin.…”

“…Erythromycin or clindamycin has been recommended as an alternative treatment for patients who are allergic to penicillin (5,11). In 1959, Lowburry and Hurst (14) first reported the decreased potency of erythromycin against S. pyogenes isolates.…”

A community outbreak of group A beta haemolytic streptococci with transferable resistance to erythromycin

“…In 1984 outbreaks associated with schools in Liverpool (Youngs, 1984), Ayrshire (Hardie, 1984) and a hospital and school in Cambridge (Walker, Whetstone & Whipp, 1984) were reported. A number of sporadic isolates and a family outbreak were reported from North Yorkshire in 1986 (Barnham & Cole, 1986), the latter study reported 14/536 (2-6%) isolates of GAS resistant to erythromycin in an 18-month period during 1984-5. Reports from other countries have shown higher rates of erythromycin resistance in GAS; 5% in the United States (Istre et al 1981), 0-5-2 % in France (Horodniceanu, Bougueleret & Delbos, 1979), 4 4% in Taiwan (Tadano et al 1978), 2-9 % in Canada (Dixon & Lipinski, 1982) and 60% in Japan (Maruyama et al 1979).…”