Group C and G Streptococcus (GCS/GGS) are bacteria related to Group A Streptococcus (GAS), the cause of “strep throat.” GCS and GGS are generally less virulent than GAS, but they can still cause a wide range of human illnesses. The most common species is Streptococcus dysgalactiae subspecies equisimilis (SDSE), which shares characteristics with GAS, including the ability to colonize the throat and skin. The danger of a Strep C or G infection depends heavily on the specific site of the infection and the overall health status of the person infected. While these organisms can be found harmlessly in the body, under certain conditions, they can lead to serious disease.
Types of Infections Caused by Strep C
Strep C and G bacteria are responsible for a broad spectrum of clinical disease, ranging from mild, localized issues to severe, systemic complications. A common presentation is pharyngitis (sore throat), similar to that caused by Group A Streptococcus. However, the role of Strep C/G in pharyngitis can be controversial, as the bacteria are frequently isolated from healthy individuals who are simply colonized. Colonization means the bacteria are present without causing symptoms, and this carrier state does not typically require antibiotic treatment.
The organisms are particularly well-known for causing infections of the skin and soft tissues. These localized infections often manifest as cellulitis, which is a deep skin infection, or erysipelas, a more superficial infection that presents with a raised, red rash. Streptococcus dysgalactiae subspecies equisimilis is a frequent cause of these skin problems, and the skin is often the initial entry point for more serious invasive disease. Less common localized infections include pyoderma and surgical wound infections.
Factors Determining Severity and Risk
A Strep C or G infection becomes life-threatening when the bacteria move beyond the localized site into normally sterile parts of the body, a condition known as invasive disease. Invasive infections include bacteremia (bacteria in the bloodstream), which can lead to severe conditions like sepsis, a widespread inflammatory response. Once in the blood, the bacteria can disseminate to deep tissue sites, causing infections such as endocarditis (inflammation of the heart lining) or bone and joint infections.
The most serious, though rare, manifestations are necrotizing fasciitis, sometimes called “flesh-eating disease,” and streptococcal toxic shock syndrome (STSS). Necrotizing fasciitis is a rapidly progressing infection that destroys muscle and fat tissue. STSS is characterized by a sudden drop in blood pressure and organ injury. These life-threatening invasive infections occur most frequently in individuals who have underlying medical conditions.
A person’s health status is the most significant factor determining the risk of severe infection. High-risk populations include the elderly and those with chronic illnesses that weaken the immune system. Individuals with diabetes, cancer, or cardiovascular disease are much more susceptible to invasive Strep C/G disease. Breaks in the skin, such as cuts or surgical wounds, also provide an opportunity for the bacteria to enter the body and initiate a severe infection.
Diagnosis and Standard Treatment Protocols
Diagnosis depends on the site and severity of the illness. For suspected pharyngitis, a throat swab is collected, while skin and soft tissue infections often require a wound culture. If an invasive disease is suspected, a blood culture is necessary to confirm the presence of the bacteria in the bloodstream. Modern molecular tests, like Polymerase Chain Reaction (PCR), can offer a rapid and highly sensitive way to detect the organism in clinical samples.
The standard medical management for Strep C/G infections involves the use of antibiotics. Penicillin is the primary treatment and is typically administered for a 10-day course to ensure complete eradication, particularly for pharyngitis. Amoxicillin is another commonly used penicillin-based option. For individuals who have an allergy to penicillin, alternative antibiotics are available, such as cephalexin, clindamycin, or azithromycin.
Prompt treatment is a factor in preventing the progression from a localized infection to the severe complications of invasive disease. While penicillin is generally effective, some strains of Strep C/G can show resistance to other classes of antibiotics, including macrolides and tetracyclines. In cases of severe or invasive disease, antibiotics may be given intravenously.