Group C and G Streptococci Infections: Emerging Challenges

Extract

New reports of serious complications from Group C (GCS) and Group G streptococci (GGS) with probable respiratory entry have been described. Particularly interesting are cases of toxic shock-like syndrome and rheumatic fever in previously healthy patients. Serious GCS and GGS infections will be missed where selective methods for group A streptococci (GAS) only are used on throat specimens.

Group A streptococci (GAS) are considered the primary pathogenic β-hemolytic streptococci cultured from the throat.¹ GAS throat infections are routinely treated to reduce spread to patient contacts, and to reduce suppurative and non-suppurative complications. Standard protocol is to screen with a rapid test for GAS and perform throat cultures on specimens with negative screening results.² New, rapid, highly sensitive and specific screening methods have been developed to detect GAS, e.g., optical immunoassay (OIA) by BioStar and DNA probe hybridization by Gen-Probe.^3-5 Therefore, recommendations have been made to replace the standard protocol with these screening methods.^6-9 These recommendations are based on the assumption that GAS is the only dangerous streptococcal pathogen that may invade the throat.

Although GAS are the most frequent streptococci isolated from throat cultures, β-hemolytic GCS and GGS and hemolysin deficient variants cause epidemics of exudative pharyngitis/pharyngotonsillitis.^10-16 The rate of positive throat cultures that are GCS rather than GAS positive in certain seasons and geographical areas ranges from 1% to 11%.¹⁶ In addition, GCS and GGS are implicated as a cause of serious complications including rheumatic fever in previously healthy children and adults.^17-28 Notably, pharyngeal carriage of GGS and/or GCS…

ABBREVIATIONS: ASO = anti-streptolysin O; BAP = blood agar plate; GAS = group A streptococci; GCS = group C streptococci; GGS = group G streptococci; OIA = optical immunoassay.