Erythromycin resistant Streptococcus pyogenes in Merseyside

Presence of mefA and mefE genes in Streptococcus agalactiae

Eighteen unrelated clinical isolates of Streptococcus agalactiae with the M phenotype harbored an mef gene. DNA sequencing showed that one of nine strains contained mefA (producing one amino acid substitution), whereas the remaining eight carried mefE (identity, 100%). Restriction analysis of PCR products indicated that the nine other strains also contained mefE.

Streptococcus pneumoniae and Streptococcus pyogenes resistant to macrolides but sensitive to clindamycin: a common resistance pattern mediated by an efflux system

Macrolide-resistant Streptococcus pyogenes isolates from Finland, Australia, and the United Kingdom and, more recently, Streptococcus pneumoniae and S. pyogenes strains from the United States were shown to have an unusual resistance pattern to macrolides, lincosamides, and streptogramin B antibiotics. This pattern, referred to as M resistance, consists of susceptibility to clindamycin and streptogramin B antibiotics but resistance to 14- and 15-membered macrolides. An evaluation of the macrolide-lincosamide-streptogramin B resistance phenotypes among our streptococcal strains collected from 1993 to 1995 suggested that this unusual resistance pattern is not rare. Eighty-five percent (n = 66) of the S. pneumoniae and 75% (n = 28) of the S. pyogenes strains in our collection had an M phenotype. The mechanism of M resistance was not mediated by target modification, as isolated ribosomes from a pneumococcal strain bearing the M phenotype were fully sensitive to erythromycin. Further, the presence of an erm methylase was excluded with primers specific for an erm consensus sequence. However, results of studies that determined the uptake and incorporation of radiolabeled erythromycin into cells were consistent with the presence of a macrolide efflux determinant. The putative efflux determinant in streptococci seems to be distinct from the multicomponent macrolide efflux system in coagulase-negative staphylococci. The recognition of the prevalence of the M phenotype in streptococci has implications for sensitivity testing and may have an impact on the choice of antibiotic therapy in clinical practice.

Streptococcus pyogenes vulvovaginitis in children in Nottingham

Isolates of Streptococcus pyogenes from vaginal swabs of children with vulvovaginitis received at Nottingham Public Health Laboratory during 1986-9 were studied. A total of 159 isolates was made during the 4 years, increasing from 17 in 1986 to 64 in 1989 and accounting for 11% of all vaginal swabs received from children. The numbers of throat swabs yielding S. pyogenes also showed an increase from 974 in 1986 to 1519 in 1989. A winter peak of isolates was noted for both vaginal swabs and throat swabs. A total of 98 strains from vaginal swabs were serotyped: 22 different types were identified, 61% of which were the common types M4, M6, R28 and M12. Erythromycin sensitivity was done on 89 strains; 84% were highly sensitive (MIC less than 0.03 mg/l). There are no other reports of such large numbers in the literature; the reason for seeing this increase in Nottingham is unclear.

Outbreaks of infections with erythromycin-resistant group A streptococci in child day care centres

Erythromycin-resistant group A streptococci (ERGAS) are considered rare in Sweden. In the county of Halland (240,000 inhabitants) in southern Sweden, we had 294 isolates of ERGAS between January 1984 and June 1985. Almost all strains were of T-type 12 and only resistant to erythromycin (MIC values approximately 8 g/l). Seven child day care centres (DCC) were involved in the outbreaks and on average 49% of all children were infected in each outbreak. Employees were seldom infected (8%), but parents and siblings more often (23% and 36%). One course of phenoxymethylpenicillin succeeded in eradicating ERGAS from 75% of those infected. The ERGAS strains are now established in southern Sweden and account for about 2% of all group A streptococcal infections in the county of Halland.

The emergence of erythromycin resistance in Streptococcus pyogenes in Fremantle, Western Australia

Erythromycin resistance in Streptococcus pyogenes is unusual except in Japan. Since January 1, 1985, a dramatic increase has occurred in the prevalence of erythromycin-resistant Strept. pyogenes infections in the outpatients who have presented to Fremantle Hospital, Western Australia. In 1985, 1% of isolates of Strept. pyogenes was erythromycin-resistant. This had risen to 9.1% of isolates in 1986 and to 17.6% of isolates in 1987. Several M- and T-types of Strept. pyogenes were involved. Treatment failure now can be expected when erythromycin is prescribed for the treatment of common infections in outpatients at this hospital. Laboratories that use disc methods of antimicrobial susceptibility testing may not detect erythromycin resistance in these organisms.

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

Erythromycin resistance amongst group A streptococci (GAS) in Great Britain is a relatively rare occurrence and outbreaks have been sporadically reported. Over an 8-month period in 1986 ten associated cases occurred in the town of Bridgewater in Somerset. Isolates were group A, type M4 and resistant to erythromycin (MIC 8 mg/l) but sensitive to lincomycin and clindamycin. Erythromycin resistance was transferable from all isolates to a group A recipient strain. No plasmid DNA could be detected in the original isolates or transconjugants.