Streptococci (plural of streptococci) are bacteria which are commonly found harmlessly living in the human respiratory, intestinal and genitourinary systems. Several species are capable of causing diseases in humans, including skin diseases.
What skin disease is caused by strep skin? infection?
Skin diseases due to direct infection with streptococci include:
- Necrotizing fasciitis
- Secondary skin infection of wounds, dermatitis, scabies, diabetic ulcers etc.
- Tropical ulcers
- Burning distal dactylitis
Streptococcus perianal and/or vulvar dermatitis.
Additionally, streptococci are capable of causing skin diseases through means other than direct infection of the skin; For example:
Scarlet fever It is a reaction to a circulation toxin produced by some strains of streptococci
- Streptococcus toxic like a shock syndrome (STSS)
- Allergic hypersensitivity to streptococcal bacteria can result in erythema nodose or vasculitis
Psoriasis, especially guttate forms, can be caused or aggravated by a streptococcal infection.
- Pustulosis acuta generalisata: sterile scattered pustules on hands, feet and other places after a streptococcal upper respiratory tract infection; may be associated with painful joints.
Bacteriology of streptococci.
Streptococci are classified as gram-positive cocci based on their appearance under a microscope. They are spherical or ovoid in shape and tend to form chains with each other.
Streptococci that cause human disease are generally facultative anaerobes; That is, they prefer lower levels of oxygen in their environment. Streptococci are further classified into subtypes based on sugar chains expressed in their outer layer (Lancefield group) and their behavior when grown in the laboratory (alpha or beta- hemolysis) Most streptococci important in skin infections belong to Lancefield groups A, C, and G, and are beta-hemolytic. Streptococci pneumoniae (pneumococci) are bacteria important in pneumonia and meningitis but rarely causes skin diseases. Pneumococci are alpha-hemolytic and do not belong to the Lancefield group.
Lancefield Group A
This group consists of a single type of streptococcus called Streptococcus pyogenes. Up to a fifth of the healthy population can carry S. pyogenes In the throat. S. pyogenes produces many toxins and enzymes that help him establish the infection. It is an important cause of pharyngitis, impetigo, cellulitis and necrotizing fasciitis. It is capable of inducing scarlet fever, postinfectious glomerulonephritis (kidney disease), and rheumatic fever (heart disease).
Several of these products produce a antibody response in the patient's blood that aids in the detection of recent streptococcal infection (e.g., anti-DNase, anti-streptolysin). These can help in the diagnosis of rheumatic fever, post-streptococcal glomerulonephritis, and erythema nodosum.
- the serum ASOT peaks around three to six weeks after infection and begins to fall in six to eight weeks, returning to base after 6 to 12 months.
- The anti-DNase B serum titer may take up to six to eight weeks to reach a peak and begins to fall three months after infection, returning to baseline more slowly.
Rapid-result throat swabs are also available, but are not absolutely reliable and must be interpreted in the clinical context (remembering that asymptomatic carriage of streptococci in the throat is common).
Lancefield Group C and G
These bacteria occasionally cause infections similar to Lancefield group A and generally affect elderly or chronically ill patients.
S. pneumoniae Bacteria can live in the throat and nose of healthy people. They produce a sticky substance on their outer layer that allows them to adhere to the lining of the nose or throat and invade, causing infections in some patients. Most infections involve the respiratory tract or meninges, but pneumococci occasionally cause cellulitis. Pneumococcus cellulitis usually affects patients with connective tissue illness or HIV infection.
Treatment of streptococcal skin infection.
It may be difficult to distinguish clinically between skin infection caused by streptococci and other bacteria such as Staphylococcus aureus. Therefore, antibiotics should be chosen to cover the most likely ones. organisms. Flucloxacillin is more appropriate than simple penicillin, as it treats both Staphylococcus (staphylococcus) and streptococcus.
If a streptococcal infection has been laboratory confirmed, the most appropriate antibiotic is usually penicillin. All Lancefield group streptococci are very sensitive to penicillin. Those patients with penicillin. allergy Erythromycin or a cephalosporin (eg, ceftriaxone) can be given, which are effective against most streptococci, although some resistance to erythromycin is emerging. in very serious S. pyogenes Infections, such as necrotizing fasciitis, clindamycin can be added to penicillin, as large numbers of bacteria can overwhelm penicillin's mechanism of action.
Pneumococcal skin infections are usually treated with penicillin, but low levels of resistance have recently been reported. In more severe infections, ceftriaxone or vancomycin may be more appropriate.