Pathogenicity Factors in Group C and G Streptococci

Abstract

This chapter is dedicated to the memory of Professor Singh Chatwal, an inspiring 'streptococcologist' who leaves us with wonderful memories of Lancefield 2002 held in Goa, India. (animal GCS), Streptococcus zooepidemicus (animal and human GCS), Streptococcus canis (animal GGS), the Streptococcus anginosus group and Streptococcus phocae (1). GCS and GGS of human origin are now considered to constitute a single subspecies, Streptococcus dysgalactiae subsp equisimilis. Therefore, the current taxonomy characterises the species as follows; S. dysgalactiae is divided into the subspecies S. dysgalactiae subsp. equisimilis and S. dysgalactiae subsp. dysgalactiae (hereafter referred to in this chapter as S. equisimilis and S. dysgalactiae). Streptococcus equi is divided into the subspecies S. equi subsp. equi and S. equi subsp. zooepidemicus (hereafter referred to as S. equi and S. zooepidemicus). On the basis of genetic evidence, Streptococcus dysgalactiae, Streptococcus equi, Streptococcus canis are more closely related to each other than to the 'S. anginosus group', and constitute species with the 'large-colony' colony phenotype. Recent data now suggests that S. equi may simply be a subclone of S. zooepidemicus (2). S. phocae is a new species expressing the group C antigen thus far only isolated from seals (3, 4). Some of these species may also contain strains which express the Lancefield group A or group F antigens (Table 2). HUMAN DISEASE AND DIAGNOSIS GCS and GGS can cause a wide range of diseases from mild to severe, both among human and animal populations. GCS and GGS generally colonize the human respiratory, gastrointestinal and genitourinary tracts, with an estimated <4% asymptomatic pharyngeal carriage rate in adults (5-7). Human invasive infections caused by GCS and GGS have been associated with underlying conditions, such as diabetes, cardiovascular diseases and chronic skin conditions (8-10). While S. dysgalactiae is considered an animal pathogen, S. equisimilis is almost exclusively a human pathogen, with increasing prevalence and overlaps in clinical manifestations with group A Streptococcus (GAS). S. equisimilis infections include acute pharyngitis, pneumonia, endocarditis, cellulitis, peritonitis, septic arthritis, bacteraemia, and toxic shock syndrome (11-23). Like GAS, S. equisimilis has also been linked to the post streptococcal sequelae rheumatic heart disease, and in high endemic areas of rheumatic fever, carriage rates of GCS/GGS have been found to be higher than GAS (24, 25).

Pathogenicity and drug resistance of animal streptococci responsible for human infections

“…However, molecular methods of species identification show that it can be unreliable and does not cover all species within the genus [16]. Strains belonging to the species S. iniae, similarly to S. pneumoniae, do not have polysaccharide C and do not fall under this classification [3,15]. Table 1 shows how the species described in this paper fit into these divisions.…”

“…This method allows us to obtain Table 1. Assignment of Streptococcus species to phylogenetic and serological groups [3,9,15,183].…”

“…Increasing attention has been paid to streptococcal infections in recent years due to their increasing role in human medicine. New diseases in humans resulting from infection with bacteria of the genus Streptococcus so far have typically concerned animals [3,4]. Moreover, Streptococcus species such as S. suis, S. dysgalactiae, S. iniae and S. equi have garnered the most attention [3].…”

“…iniae and S. equi have garnered the most attention [3]. This review discusses streptococci species with multiple virulence factors.…”

“…iniae , similarly to S. pneumoniae , do not have polysaccharide C and do not fall under this classification [3, 15]. shows how the species described in this paper fit into these divisions.…”