Group A Streptococcal Infection Follow-up

Further inpatient care may be necessary in patients with group A streptococcal infections for rehabilitative reasons (eg, chorea, neuropsychiatric manifestations of infection) or for debilitating arthritis. Consultation with a physical medicine and rehabilitation (PMR) physician, neurologist, or rheumatologist may be useful in these situations.

Outpatient follow-up care with infectious diseases specialists (management of long-term therapy or prophylaxis for acute rheumatic fever), surgeons, neurologists, rheumatologists, and nephrologists may be important. The primary care physician must be closely involved in managing and coordinating long-term special services.

Prophylaxis against streptococcal infection includes the following:

• Long-term antibiotic therapy to prevent streptococcal infection is indicated for patients with a history of acute rheumatic fever or rheumatic heart disease. The recommended regimen is an injection every 3-4 weeks with 1.2 million IU of benzathine penicillin G, 250 mg of oral penicillin V twice a day, or 0.5-1 g of sulfadiazine daily.
• The role of prophylaxis for household contacts of individuals with either acute streptococcal disease or nonsuppurative complications is uncertain. Some authorities recommend that cultures be obtained from all contacts if a family history of rheumatic fever is noted or when a patient with acute glomerulonephritis is identified.
• An alternative approach is to treat all household contacts in the setting of acute poststreptococcal glomerulonephritis (PSGN) in an effort to eradicate household transmission of nephritogenic strains. For invasive group A streptococcal infections (eg, necrotizing fasciitis, toxic shock syndrome [TSS]), no data are available on which to base assessment of risk to household contacts. However, because of the devastating nature of these infections and the observation that invasive disease may be due to clonal outbreaks of more virulent strains, empiric antibiotic therapy of household contacts seems warranted.

Prospects for streptococcal vaccines include the following:

• Apart from rheumatic fever prophylaxis and the prevention of intrafamily spread, few strategies are available to prevent streptococcal infection.
• A streptococcal vaccine could offer promise for prevention of disease, but an effective vaccine would have to provide protection from multiple serotypes. Furthermore, theoretical concern that vaccine-induced antibodies could injure host tissue and precipitate rheumatic fever is recognized.
• Multivalent vaccines that contain multiple M protein peptide epitopes have been engineered and show efficacy in animal models but have not yet entered clinical trials.^[12]
• Several vaccine candidates against group A streptococcal infection are in varying stages of preclinical and clinical development.^[13] However, the hope is that one of these vaccines will reach licensure within the next decade. Only the multivalent N-terminal vaccine has entered clinical trials over the last 30 years.

Acute rheumatic fever and acute PSGN are the classic nonsuppurative complications of S pyogenes infections. Although the link between group A streptococcal infections and these complications has been clearly established, the mechanism or mechanisms through which the injury is produced are incompletely defined.

• Acute rheumatic fever

  • During the 1960s and 1970s, this disease nearly disappeared in the United States, although it continued unabated in developing countries. This decline in disease was largely attributed to careful disease surveillance and initiation of prompt aggressive antibiotic therapy in primary care practice. However, in 1985, several multifocal outbreaks of rheumatic fever occurred in several parts of the United States. In contrast with earlier outbreaks in this country, most of the patients were white, middle-class children from rural and suburban communities who had good access to health care. This unexplained resurgence in acute rheumatic fever underscores the point that a great deal remains to be learned about the pathogenesis of this disease.
  • Epidemiologically, considerable evidence supports the link between group A streptococcal infections of the upper respiratory tract and acute rheumatic fever, although only certain M group serotypes (ie, 1, 3, 5, 6, 18, 24) are associated with this complication. Very mucoid strains, particularly strains of M type 18, have appeared in numerous communities prior to the appearance of rheumatic fever. Rheumatic fever is most frequently observed in children aged 5-15 years (the age group most susceptible to group A streptococcal infections). The attack rate following upper respiratory tract infection is approximately 3% for individuals with untreated or inadequately treated infection. The latent period between the group A streptococcal infection and the onset of rheumatic fever varies from 2-4 weeks. In contrast to PSGN, which may follow either pharyngitis or streptococcal pyoderma, rheumatic fever can occur only after an infection of the upper respiratory tract.
  • Despite the depth of knowledge about the molecular microbiology of Streptococcus pyogenes that has accumulated in recent years, the pathogenesis of acute rheumatic fever remains unknown. A direct effect of a streptococcal extracellular toxin, in particular streptolysin O, may be responsible for the pathogenesis of acute rheumatic fever, according to some hypotheses. Observations that streptolysin O is cardiotoxic in animal models support this hypothesis, but linking this toxicity to the valvular damage observed in acute rheumatic fever has been difficult.
  • A more popular hypothesis is that an abnormal host immune response to some component of the group A Streptococcus is responsible. The group A streptococcal M protein shares certain amino acid sequences with some human tissues, and this has been proposed as a source of cross-reactivity between the organism and human host that could lead to an immunopathologic immune response. Also, antigenic similarity between the group-specific polysaccharide of S pyogenes and glycoproteins found in human and bovine cardiac valves has been recognized, and patients with acute rheumatic fever have prolonged persistence of these antibodies compared with controls with uncomplicated pharyngitis. Other group A streptococcal antigens appear to cross-react with cardiac sarcolemma membranes.
  • As a result of this molecular mimicry, during the course of the host's immune response to the group A streptococci, the host's antigens may be mistaken as foreign; this leads to an inflammatory cascade with resultant tissue damage. In patients with acute rheumatic fever with Sydenham chorea, common antibodies to antigens found in the S pyogenes cell membrane and the caudate nucleus of the brain are present, further supporting the concept of an aberrant autoimmune response in the development of acute rheumatic fever.
  • Recently, interest in whether such autoimmune responses may play a role in the pathogenesis of the pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) syndrome has been considerable, although further work is necessary to establish the link between streptococcal infections and these syndromes. Differences in genetic susceptibility apparently play an important role in the likelihood of developing poststreptococcal sequelae, although the exact nature of the genetic predisposition remains undefined.
  • Acute rheumatic fever is largely a clinical diagnosis best established by careful physical examination. The Jones criteria for the diagnosis are outlined in Rheumatic Fever. Few patients with acute rheumatic fever have positive throat culture or rapid streptococcal antigen test findings at the time of presentation.
  • Because the isolation or identification of group A streptococci from a throat swab does not distinguish between a person with acute streptococcal infection and a person who is a streptococcal carrier, the best evidence of an antecedent streptococcal infection is a serologic response to the organism. An elevated streptococcal antibody titer can be used as serologic evidence of a recent group A streptococcal infection. Serial samples should be obtained because identification of a rising titer is particularly helpful. The most commonly used streptococcal antibody test is the ASO titer, although anti-DNase B and antihyaluronidase assays, which can be measured as a part of a panel of streptococcal antibodies referred to as the streptozyme panel, are also helpful. When 2 or more different streptococcal antibody tests are performed, an increased titer is found within the first few months of onset in most instances of acute rheumatic fever.
• Acute glomerulonephritis

  • Glomerulonephritis can follow group A streptococcal infections of either the pharynx or the skin, and incidence varies with the prevalence of so-called nephritogenic strains of group A streptococci in the community. Type 12 is the most frequent M serotype that causes PSGN after pharyngitis, and M type 49 is the type most commonly related to pyoderma-associated nephritis. The latent period between group A streptococcal infection and the onset of glomerulonephritis varies from 1-2 weeks.
  • Pathogenesis appears to be immunologically mediated. Immunoglobulins, complement components, and antigens that react with streptococcal antisera are present in the glomerulus early in the course of the disease, and antibodies elicited by nephritogenic streptococci are postulated to react with renal tissue in such a way as to promote glomerular injury. In contrast to acute rheumatic fever, recurrences of PSGN are rare. Diagnosis of PSGN is based on clinical history, physical examination findings, and confirmatory evidence of recent streptococcal infection (see Glomerulonephritis, Poststreptococcal).
  • Even in the absence of bacteriologic confirmation of S pyogenes, the presence of skin lesions compatible with streptococcal impetigo is highly suggestive, and elevated streptococcal antibody titers in the setting of a hypocomplementemic nephritis is essentially diagnostic of PSGN. Over the past several decades, incidence of acute PSGN in the United States has been steadily declining.

Educate patients with acute rheumatic fever on the need for long-term penicillin prophylaxis. For excellent patient education resources, visit eMedicine's Ear, Nose, and Throat Center and Women's Health Center. Also, see eMedicine's patient education articles Sore Throat, Strep Throat and Toxic Shock Syndrome.