Rapid Differentiation between Members of the Anginosus Group and Streptococcus dysgalactiae subsp. equisimilis within Beta-Hemolytic Group C and G Streptococci by PCR

Abstract

Based on a pair of primers developed initially for differentiating the anginosus group from other viridans streptococci, the PCR reported here can also differentiate between members of the anginosus group and Streptococcus dysgalactiae subsp. equisimilis among beta-hemolytic group C and G streptococci. The resulting 742-bp PCR product was specific for members of the anginosus group, although a smaller, nonspecific product (361 bp) was generated from S. dysgalactiae subsp. equisimilis. Restriction digestion of the amplicon with XbaI and BsmI further differentiated Streptococcus anginosus from Streptococcus constellatus within the anginosus group.The human isolates of beta-hemolytic group C (group C streptococci [GCS]) and group G streptococci (GGS) include the anginosus group (Streptococcus anginosus and/or Streptococcus constellatus) and Streptococcus dysgalactiae subsp. equisimilis. Among them, S. anginosus and S. dysgalactiae subsp. equisimilis are found in both GCS and GGS, but S. constellatus is found only in GCS. While these species are regarded as normal flora that colonize human skin, throat, intestine, and vaginal tract (6, 15), they can cause serious infections such as bacteremia, endocarditis, rheumatic fever, and streptococcal toxic shock syndrome (7, 9, 16).Identification of the above-mentioned bacteria in the clinical laboratory setting usually depends on morphological observation and biochemical tests and serogrouping. Many laboratories report the identification of these bacteria to the group level but not the species level. However, differentiation to the precise species among these GCS and GGS should not be ignored, because it has been reported that large-colony GCS or GGS (referring to S. dysgalactiae subsp. equisimilis) may have virulence factors similar to those of Streptococcus pyogenes (9, 13) and are more invasive than the anginosus group among GCS or GGS (4).Conventional methods of differentiation based on morphology and biochemical reactions were time-consuming, and the results were usually unsatisfactory (5). Molecular methods targeting the 16S rRNA gene, the 16S-23S rRNA intergenic spacer, or the groEL gene have recently been used as more accurate methods to identify species of the anginosus group or S. dysgalactiae subgroups (1,2,8,16,17). However, these methods usually need sequence determination and were not economical for clinical use.We have previously determined the groESL sequences in viridans group streptococci (14). The groES and groEL genes (also known as cpn10/60) are evolutionarily conserved and are considered as an alternative for the identification of microorganisms. To differentiate the anginosus group from other viridans group streptococci, we designed a set of PCR primers specific for members of the anginosus group. In this study, we unexpectedly found that beta-hemolytic S. dysgalactiae subsp. equisimilis also generated a smaller, nonspecific PCR product.Bacterial strains. The bacterial strains used in this study consisted of the following reference strains obtained fr...

Bacteremia Caused by Group G Streptococci, Taiwan

“…The PCR method developed in our hospital and used in this study could effectively differentiate S. anginosus from S. dysgalactiae subsp. equisimilis (7).…”

“…PCR to differentiate between S. anginosus and S. dysgalactiae subsp. equisimilis was performed for all GGS isolates as described (7). For identifi cation of S. canis, a probable isolate was identifi ed by a negative β-glucuronidase result and further confi rmed with the 16sRNA method as described (8).…”

Distribution of emm Types and Genetic Characterization of the mgc Locus in Group G Streptococcus dysgalactiae subsp. equisimilis from a Hospital in Northern Taiwan

“…Species identification was reconfirmed by the method described previously (10) (4,11,14). It is noted that stC839.0 was reported to be a dominant emm type from group C S. dysgalactiae subsp.…”

Soft tissue infection caused by Streptococcus dysgalactiae subsp. equisimilis possessing group Aantigen: a and review of the literature

“…For SDSE identification, the following molecular methods were used: 16S rRNA gene sequencing [5,12,[28][29][30], polymerase chain reaction (PCR) [15,28], 23S rRNA gene sequencing [31] and in situ hybridization [29].…”