Bacteria exist in diverse environments, including within and on the human body. While many are harmless or beneficial, others can cause illness. Streptococcus dysgalactiae is a group of bacteria that can impact human health. This article explores its characteristics, the infections it causes, and their management.
Understanding Streptococcus dysgalactiae Group
Streptococcus dysgalactiae is a gram-positive, spherical bacterium that typically arranges itself in chains. These bacteria are part of the family Streptococcaceae and can infect both humans and animals. They are commonly found as part of the normal bacterial populations in the alimentary tract, genital tract, and sometimes on the skin.
Lancefield grouping categorizes streptococci based on specific carbohydrate antigens in their cell walls. Streptococcus dysgalactiae includes strains that react with Lancefield Group C and G antisera. The subspecies Streptococcus dysgalactiae subspecies equisimilis (SDSE) is most frequently associated with human infections, often expressing Lancefield group C or G antigens. In contrast, Streptococcus dysgalactiae subspecies dysgalactiae is primarily an animal pathogen.
Common Infections it Causes
Streptococcus dysgalactiae can cause various human infections, from superficial conditions to severe systemic diseases. Skin and soft tissue infections are common, including cellulitis, a deeper skin infection characterized by redness, swelling, warmth, and pain. Erysipelas, a more superficial skin infection, is also caused by S. dysgalactiae. In some instances, it can lead to more severe conditions like necrotizing fasciitis, a rapidly progressing infection that destroys soft tissue, or pyomyositis.
The bacterium can also cause serious invasive infections when it enters normally sterile body sites. These include bacteremia, where bacteria circulate in the bloodstream, and septic arthritis, an infection within a joint that causes pain and swelling. Osteomyelitis, an infection of the bone, and endocarditis, an infection of the heart valves, are other severe manifestations. While less common than with Streptococcus pyogenes (Group A Strep), S. dysgalactiae can also cause pharyngitis.
Diagnosis and Treatment
Diagnosing an infection caused by Streptococcus dysgalactiae requires laboratory testing. A healthcare provider collects a sample from the affected area, such as a swab from a wound or a blood sample if a systemic infection is suspected. This sample is then sent to a laboratory for bacterial culture, where the bacteria are grown and identified. Rapid antigen tests for strep throat, designed to detect Group A Strep, do not identify S. dysgalactiae.
Infections caused by Streptococcus dysgalactiae are treated with antibiotics. Penicillin is the preferred medication due to its effectiveness. For more severe or widespread infections, intravenous antibiotics may be administered in a hospital setting to ensure higher drug concentrations reach the site of infection. While S. dysgalactiae is susceptible to penicillin, healthcare providers select the appropriate antibiotic based on the specific infection and patient factors. Completing the full prescribed course of antibiotics is important to eradicate the infection and help prevent antibiotic resistance.
Preventing Infection
Preventing the spread of Streptococcus dysgalactiae infections involves practicing good general hygiene. Frequent handwashing with soap and water is an effective measure to reduce bacterial spread. Covering coughs and sneezes helps contain respiratory droplets that may carry bacteria. Avoiding the sharing of personal items like eating utensils, cups, and towels can further minimize transmission. While vaccines exist for some streptococcal infections, there is no widely available vaccine specifically for Streptococcus dysgalactiae in humans.