Streptococcal infection

Streptococcal infection is a group of infectious diseases caused by streptococci of various serological groups, with airborne and alimentary transmission of the pathogen, occurring with fever, intoxication, local suppurative processes and the development of post-streptococcal autoimmune (rheumatism, glomerulonephritis) complications.

ICD-10 codes

• A38. Scarlet fever.
• A40. Streptococcal septicemia.
  • A40.0. Septicemia due to group A streptococcus.
  • A40.1. Septicemia due to group B streptococcus.
  • A40.2. Septicemia due to group D streptococcus.
  • A40.3. Septicemia due to Streptococcus pneumoniae.
  • A40.8. Other streptococcal septicemias.
  • A40.9. Streptococcal septicemia, unspecified.
• A46. Erysipelas.
• A49.1. Streptococcal infection, unspecified.
• B95. Streptococci and staphylococci as the cause of diseases classified elsewhere.
  • B95.0. Group A streptococci as the cause of diseases classified elsewhere.
  • B95.1. Group B streptococci as the cause of diseases classified to other chapters.
  • B95.2. Group D streptococci as the cause of diseases classified elsewhere.
  • B95.3. Streptococcus pneumoniae as the cause of diseases classified to other chapters.
  • B95.4. Other streptococci as the cause of diseases classified to other chapters.
  • B95.5. Unspecified streptococci as the cause of diseases classified to other chapters.
• G00.2. Streptococcal meningitis.
• M00.2. Other streptococcal arthritis and polyarthritis.
• P23.3. Congenital pneumonia due to group B streptococcus.
• P23.6. Congenital pneumonia due to other bacterial agents (streptococci, except group B).
• P36.0. Sepsis of newborn due to group B streptococcus.
• P36.1 Sepsis of newborn due to other and unspecified streptococci.
• Z22.3. Carriage of pathogens of other specified bacterial diseases (streptococci).

What causes strep infection?

Streptococcal infection is caused by streptococci. The most significant streptococcal pathogen is S. Pyogenes, it is beta-hemolytic, and in the Lancefield classification it is classified as group A. Thus, we get: beta-hemolytic streptococcus group A (GABGS).

What are the symptoms of a strep infection?

The two most common acute illnesses caused by group A beta-hemolytic streptococci are pharyngitis and skin infections. In addition, delayed nonsuppurative complications such as acute rheumatic fever and acute glomerulonephritis sometimes appear 2 or more weeks after a group A beta-hemolytic streptococcal infection. Illnesses caused by other streptococcal species are generally less common and include soft-tissue infections or endocarditis. Some non-GABHS infections occur predominantly in certain populations (e.g., group B streptococci in neonates and postpartum women, enterococci in hospital patients).

Infections may spread along the extent of the affected tissues and via lymphatic pathways to regional lymph nodes. Local suppurative complications such as peritonsillar abscess, otitis media, and sinusitis may also occur. Bacteremia may also occur. Whether suppuration occurs depends on the severity of the disease and the susceptibility of the affected tissue.

Streptococcal pharyngitis is usually caused by group A beta-hemolytic streptococci. About 20% of patients with this disease experience symptoms of streptococcal infection, such as sore throat, fever, redness of the pharyngeal walls, and purulent plaque on the tonsils. In the remaining 80%, the symptoms of streptococcal infection are less pronounced, and the examination reveals the same signs as in viral pharyngitis. The cervical and submaxillary lymph nodes may be enlarged and painful. Streptococcal pharyngitis can lead to peritonsillar abscess. Cough, laryngitis, and nasal congestion are not characteristic of streptococcal pharyngeal infection. The presence of these symptoms usually indicates a disease of another etiology, most often viral or allergic. 20% of people are asymptomatic carriers of group A beta-hemolytic streptococci. Skin infections include impetigo and cellulitis. Cellulitis can spread very quickly. This is due to the numerous lytic enzymes that are produced mainly by group A streptococci. Erysipeloid is a special case of cellulitis.

Necrotizing fasciitis, caused by pyogenic streptococci, is an acute skin or, rarely, muscle infection that spreads along fascial webs. The streptococci in necrotizing fasciitis originate from the skin or viscera, and the injury may be surgical, trivial, distant from the site of the disease, or blind, as in colonic diverticula and appendiceal abscesses. The disease is more common in intravenous drug users. Previously known as streptococcal gangrene and popularly called meat-eating bacteria, the syndrome may also be polymicrobial, with aerobic and anaerobic saprophytic flora, including Clostridium Perfringens, also contributing to the inflammation. When the syndrome involves the peritoneum, it is called Fournier's gangrene. Associated diseases, such as immunocompromise, diabetes, and alcoholism, are common. Symptoms of streptococcal infection begin with fever and intense local pain. Thrombosis of the microcirculatory bed causes ischemic necrosis, which leads to rapid spread of infection and disproportionately increasing intoxication. In 20-40% of cases, adjacent muscles are involved in the process. Shock and renal dysfunction often occur. Even with adequate treatment, mortality remains high. Septicemia, purulent sepsis, endocarditis and pneumonia of streptococcal etiology remain serious complications, especially if the etiologic microorganism is a multiresistant enterococcus.

Streptococcal toxic shock syndrome is similar to that caused by Staphylococcus aureus. It may be caused by toxin-producing strains of group A beta-hemolytic streptococci. Patients are usually children and adults with otherwise healthy skin or soft tissue infections.

Late complications of streptococcal infection

The mechanism of occurrence of late complications is largely unknown, but it is known that cross-immunity reactions occur, in which the formed antibodies to streptococcal antigens react with the host tissues.

Acute rheumatic fever (ARF) is an inflammatory disorder. It occurs in less than 3% of patients within a few weeks of an untreated upper respiratory tract infection caused by group A beta-hemolytic streptococci. Today, ARF is much less common than in the pre-antibiotic era. Diagnosis is based on a combination of carditis, arthritis, chorea, specific skin manifestations, and laboratory tests. The most important aspect of treating streptococcal pharyngitis is preventing ARF.

Poststreptococcal acute glomerulonephritis is an acute nephritic syndrome that follows pharyngitis or skin infection caused by certain nephritogenic strains of group A beta-hemolytic streptococci. Only a certain number of group A streptococcal serotypes can cause this sequela. The overall incidence of attacks following pharyngitis or skin infection is approximately 10-15%. It most often occurs in children 1-3 weeks after the illness. Almost all children recover without permanent renal impairment, but some adults may develop it. Antibiotic treatment of streptococcal infection does not significantly affect the development of poststreptococcal glomerulonephritis.

How is strep infection diagnosed?

Streptococci are rarely identified by sheep blood agar culture. Rapid antigen tests are now available that can detect group A beta-hemolytic streptococci directly from throat swabs. Many of these tests are based on immunoassay methodology. Recently, optical immunoassays have become more widely available. They have high sensitivity (>95%) but vary in specificity (50-80% and 80-90% for the most recent optical immunoassays). Negative results should be confirmed by culture (particularly when there is a question of the use of macrolides because of potential resistance). By the time of recovery, evidence of infection may be obtained indirectly by measuring antistreptococcal antibody titers in the serum. Detection of antibodies is very important in the diagnosis of poststreptococcal diseases such as acute rheumatic fever and glomerulonephritis. Confirmation requires consistent increases in antibody titers in samples, as a single increase in antibody titers may be due to a previous prolonged infection. Serum samples should not be taken more frequently than every 2 weeks, and may also be taken every 2 months. The antistreptolysin-O (ASL-O) titer increases in only 75-80% of cases of infection. For a complete diagnosis in difficult cases, the following tests may be used to determine: antihyaluronidase, antideoxyribonuclease B, antinicotinamide adenine dinucleotidase, or antistreptokinase. Penicillin given in the first 5 days of illness for symptomatic treatment of streptococcal pharyngitis may delay the onset and decrease the ASL-O response. Patients with streptococcal pyoderma usually do not produce a significant ASL-O response, but may generate a response to other antigens (particularly anti-DNAase or antihyaluronidase).

How is streptococcal infection treated?

Streptococcal pharyngitis

Pharyngeal beta-hemolytic group A streptococcal infections are usually self-limited. Antibiotics may shorten the duration of illness in children, especially with scarlet fever, but have little effect on symptom development in adults. However, antibiotics can prevent local purulent complications and acute rheumatic fever.

Penicillin is the drug of choice. A single injection of benzathine penicillin G 600,000 units intramuscularly for small children (less than 27.3 kg) and 1.2 million units intravenously for adolescents and adults is often sufficient. Oral penicillin V may be used when the patient is confident that he or she will complete the required 10-day course and will follow directions. The dose is 500 mg of penicillin V (250 mg for children less than 27 kg). Oral cephalosporins are also effective. Cefdinir, cefpodoxime, and azithromycin may be used for a 5-day course of therapy. Delaying therapy for 1 to 2 days until laboratory confirmation does not increase the duration of the disease or the incidence of complications.

In cases where penicillin and beta-lactam are contraindicated, erythromycin 250 mg orally or clindamycin 300 mg orally for 10 days is prescribed, but resistance of group A beta-hemolytic streptococci to macrolides has been noted (some authors recommend confirming in vitro susceptibility in cases where a macrolide is to be prescribed and there is a possibility of macrolide resistance in the community). Trimethoprim-sulfamethoxazole, some fluoroquinolones, and tetracyclines are unreliable for the treatment of streptococcal infections. Clindamycin (5 mg/kg orally) is a more preferable drug in children with frequent exacerbations of chronic tonsillitis. This may be due to the fact that chronic tonsillitis causes co-infection in the tonsil crypts with penicillinase-producing staphylococci or anaerobes, which inactivate penicillin G, and clindamycin has good activity against these agents. It has also become known that clindamycin suppresses exotoxin production faster than other drugs.

Sore throat, fever, headache can be treated with analgesics and antipyretics. Bed rest and isolation are not necessary. Close contacts of people with symptoms of streptococcal infection or a history of post-streptococcal complications should be examined for the presence of streptococci.

Skin streptococcal infections

Cellulitis is often treated without performing a culture. This is because it is very difficult to isolate a culture. Therefore, agents effective against not only streptococci but also staphylococci are used for treatment. Necrotizing fasciitis should be treated in the intensive care unit. Extensive (possibly repeated) surgical debridement is necessary. The recommended initial antibiotic is a beta-lactam (often a broad-spectrum agent until the etiology is confirmed by culture) plus clindamycin.

Although staphylococci remain sensitive to lactam antibiotics, animal studies have shown that penicillin is not always effective against large bacterial inoculums because streptococci grow slowly.

Other streptococcal infections

The drugs of choice for treating infections caused by groups B, C, and G are penicillin, ampicillin, and vancomycin. Cephalosporins and macrolides are generally effective, but they must be prescribed taking into account the susceptibility of the microorganisms, especially in seriously ill, immunocompromised, or weakened patients and in people with foreign bodies in the infection. Surgical drainage and wound debridement as an adjunct to antimicrobial therapy may be life-saving.

S. bovis is relatively sensitive to antibiotics. Although vancomycin-resistant isolates of S. bow's have recently been reported, the organism remains sensitive to penicillin and aminoglycosides.

Most viridans streptococci are sensitive to penicillin G, and the remainder are sensitive to lactams. Resistance is increasing, and therapy for these strains should be guided by in vitro susceptibility testing.