OVERVIEW
Group A Streptococcus (GAS), also known as Streptococcus pyogenes, is one of the most important pathogens of bacterial infections in humans.GAS can affect any part of the body, but is most common in upper respiratory tract infections, followed by infections of soft tissues of the skin.It can cause both suppurative and non-suppurative complications, and is an indirect cause of the allergic diseases rheumatic fever and acute glomerulonephritis. In recent years the increase in the incidence of serious infections caused by GAS, invasive group A streptococcal infections, and their serious consequences have also drawn greater attention to this group of bacterial infections.
Etiology
The causative agent is group A streptococcus. The pathogen can reside in the oral cavity and can survive for several weeks in sputum, exudate, etc. The pathogenicity of streptococci is related to their virulence. The pathogenicity of streptococci is related to the composition of the organism and the toxins and enzymes it produces. Streptococcal infections can also be transmitted through skin wounds. Infection of the nasopharynx or wounds with virulent streptococci is an important cause of skin wound infections, and dry secretion particles or dander can be airborne or indirectly transmitted by hand or handkerchief. Streptococci spread in the air or contaminate the environment and utensils can also spread this type of bacterial infection. Puerperal infections can be spread by a midwife who carries the bacteria in the throat or by an infected infant in the nursery.
Transmission of streptococcal infections via streptococcal-contaminated foods such as milk or milk products is now rare. Invasive group A streptococcal infections present as toxic shock syndrome (TSS) which is often life-threatening. Infection occurs in healthy adults, most often between the ages of 20 and 50 years, and has been reported in children. The disease can spread from person to person.
Symptoms
1. Respiratory tract infections
(1) Acute pharyngitis and acute tonsillitis The incubation period is usually 2 to 4 days. The onset of acute, with chills or chills with high fever of about 39 ℃, sore throat is obvious, exacerbated when swallowing. In addition there are still generalized pain, fatigue, headache and so on. Nausea, vomiting and diarrhea are common in children.
(2) Scarlet fever: In addition to the clinical manifestations of acute tonsillitis, scarlet fever patients have special manifestations such as skin rash. The rash usually appears within 24 hours after the onset of the disease, and there are also special manifestations such as skin rash. Typical rash is on the basis of diffuse congestive redness of the skin, widely scattered pinpoint size, dense and uniform punctate slightly elevated scarlet rash, finger pressure after congestion subsides, touch a fine sand-like sensation, severe cases can be hemorrhagic rash.
2. Skin and soft tissue infections
(1) Dengue Clinical manifestation is localized skin inflammation, accompanied by chills, fever and obvious toxic symptoms.
(2) Streptococcal pyoderma, manifested as superficial skin infections with pustules, mostly seen in children aged 2 to 5 years old or army soldiers in poor sanitary conditions, and is common in summer.
(3) Other infections Streptococcal cellulitis can occur in burns or wound infections; recurrent cellulitis occurs in cases of impaired lymphatic circulation, such as filariasis and radical surgery for breast tumors axillary lymph node dissection.
(4) Invasive group A streptococcal infection Clinical manifestations include toxic shock syndrome, necrotizing fasciitis and myositis, cellulitis, and often multiple organ failure.
Examination
1. Peripheral blood picture
The total number of leukocytes and neutrophils are increased, and it is higher in patients with septic complications. In patients with severe infections, such as TSS, the cell classification may be shifted to the left, and the eosinophils of scarlet fever patients may be increased to 5%-10% after the rash. the platelet count of patients with TSS may be normal at the beginning of the disease, and then decrease.
2. Urine routine
Proteinuria can be seen in patients with high fever, and the urine protein increases and erythrocytes and tubular pattern appear when nephritis is complicated, and the urinary abnormality disappears after the fever subsides in patients without complications.
3. Pathologic examination
Pathogenic examination of acute pharyngitis and tonsillitis patients should firstly make pharyngeal swab culture, such as sampling, culture in time and in the right way, most of the patients can get positive results, only about 10% of the patients are false-negative.
4. Other
Patients with TSS may have pulmonary hypoplasia, decreased oxygen saturation, hepatic and renal hypoplasia, hypoproteinemia and other manifestations.
Diagnosis
A positive throat swab culture is still the “gold standard” for the diagnosis of group A streptococcal pharyngitis or tonsillitis. The recent development of rapid antigen detection test kits (RADTs) has been used as an adjunctive diagnostic method to pharyngeal swab cultures. When RADTs are negative, a throat swab culture is needed to make a definitive diagnosis.
Treatment
1. Patients with acute group A streptococcal pharyngitis or tonsillitis should receive antimicrobial medications and should complete a course of therapy sufficient to achieve clearance of the bacteria from the lesion.
There are a variety of antimicrobial therapeutic agents, but penicillin is still preferred. ① Penicillin and its analogs: penicillin intramuscular injection; application of procaine penicillin daily intramuscular injection. ② patients allergic to penicillin alternative choice of erythromycin in various preparations. ③ patients allergic to penicillin, but not a serious reaction that is anaphylactic shock, can also be a prudent alternative to the oral first-generation, second-generation cephalosporins, one of the antibiotics.
2. The antimicrobial drug selection for dengue and streptococcal impetigo is the same as that for pharyngitis and tonsillitis.
3. The antimicrobial treatment of invasive group A streptococcal infection should be rapidly administered broad-spectrum antimicrobial drugs as empirical treatment at the onset of the disease, and once the pathogenic bacteria are determined, high dose of penicillin should be administered intravenously, and penicillin allergy can be changed to the first-generation cephalosporins, but should be excluded from the penicillin class with a history of anaphylactic shock in patients.
4. In addition to antimicrobial treatment, the patient should be under close supervision at the beginning of the disease, and it is often necessary to assist the application of respiration, hemodialysis, necrotic fasciectomy, drainage of abscesses and other measures.
5. The application of specific antibodies to neutralize the toxin is still under study. The use of intravenous immunoglobulin has also been reported to help reduce the morbidity and mortality rate.