Streptococcal Pharyngitis (Strep Throat) Maria Pitaro, MD ore throat is a very common reason for a visit to a health care provider. While the major treatable pathogen is group A beta hemolytic Streptococcus (GAS), Sthis organism is responsible for only 15-30% of sore throat cases in children and 5-10% of cases in adults. Other pathogens that cause sore throat are viruses (about 50%), other bacteria (including Group C beta hemolytic Streptococci and Neisseria gonorrhea), Chlamydia, and Mycoplasma. In this era of increasing microbiologic resistance to antibiotics, the public health goal of all clinicians should be to avoid the inappropriate use of antibiotics and to target treatment to patients most likely to have infection due to GAS. Clinical Manifestations and chest and in the folds of the skin and usually Pharyngitis due to GAS varies in severity. The spares the face, palms, and soles. Flushing of the Streptococcal Pharyngitis most common presentation is an acute illness with cheeks and pallor around the mouth is common, (Strep Throat). sore throat, fever (often >101°F/38.3°C), tonsillar and the tongue becomes swollen, red, and mottled Inflammation of the exudates (pus on the tonsils), and tender cervical (“strawberry tongue”). Both skin and tongue may oropharynx with adenopathy (swollen glands). Patients may also have peel during recovery. petechiae, or small headache, malaise, and anorexia. Additional physical Pharyngitis due to GAS is usually a self-limited red spots, on the soft palate. examination findings may include petechiae of the condition with symptoms resolving in 2-5 days even Photo courtesy soft palate and a red, swollen uvula. Many patients if untreated. Treatment has been shown to prevent of the CDC have a milder illness without exudates. Nausea, some complications of GAS pharyngitis. vomiting, and abdominal pain may be prominent in children. Interestingly, the presence of cough, Complications coryza, runny nose, hoarseness, conjunctivitis, and Two classes of complications exist: suppurative diarrhea make infection with GAS less likely. and non-suppurative. Suppurative complications of Scarlet fever is caused by certain strains of GAS pharyngitis include the following infections: GAS. These patients have a diffuse, erythematous • retropharyngeal infections, including cel- rash with the texture of sandpaper that blanches lulitis or abscess; when pressed. The rash is most visible on the neck • otitis media; The Health Care of Homeless Persons - Part I - Streptococcal Pharyngitis (Strep Throat) 147 • sinusitis; and Transmission • rare complications due to bacteremia, such GAS spreads when a person coughs or sneezes as necrotizing fasciitis, meningitis, or brain infected droplets into the air that come into abscess. contact with another person’s mucous membranes. Some studies have shown that antibiotic Crowded settings such as schools and shelters therapy of GAS can decrease the incidence of otitis heighten the chance of transmission among pupils media and sinusitis. and guests. On rare occasions outbreaks have been The most common non-suppurative complica- attributed to contaminated food. tions are acute rheumatic fever and acute post- The average incubation period is 1-4 days, and streptococcal glomerulonephritis. Acute rheumatic the highest risk of transmission occurs during the fever (ARF) is an inflammatory disease involving the acute stage. The rate of transmission of GAS in heart, joints, connective tissue, and nervous system. untreated patients is approximately 35% in close This usually arises within 2-4 weeks of pharyngitis contacts, such as family members or schools. After and can result in progressive rheumatic heart disease. an infected person completes 24 hours of therapy ARF happens in < 3% of untreated cases of GAS with penicillin, the risk of transmission diminishes during an epidemic and in < 0.5% of sporadic cases. significantly. Penicillin therapy for treatment of GAS pharyngitis Sometimes people “carry” the GAS infection, within 9 days of onset of symptoms has been shown but they are not sick with GAS and pose no risk to to decrease the incidence of ARF by 75%. spread the disease. Carriers are those in whom GAS Acute post-streptococcal glomerulonephritis is has colonized the nose, throat, or skin and who do due to infection with certain strains of GAS that can not have clinical evidence of illness. These persons affect the kidneys and complicates approximately rarely transmit streptococcal infection and are not at 5% of cases of GAS pharyngitis in children. Most risk for developing rheumatic fever. cases occur in children younger than 7 years of age. The glomerulonephritis usually occurs within 10 Clinical Diagnosis days following a GAS upper respiratory infection. Since sore throat is such a common problem The clinical presentation is variable, ranging from and distinguishing viral infection from GAS infec- asymptomatic microscopic hematuria to acute tion can be difficult, several clinical prediction rules nephrotic syndrome with proteinuria, edema, have been developed. These rules can help providers hypertension, and acute renal failure. Unlike ARF, predict which patients are likely to have GAS and antimicrobial therapy does not prevent acute post- need treatment, which patients should be tested, streptococcal glomerulonephritis. Recurrence is and which patients are unlikely to have GAS and in rare, and the disease does not usually lead to residual whom antibiotics can be safely withheld. Because of renal damage. A very rare non-suppurative compli- recent overuse of antibiotics and the emergence of cation of GAS pharyngitis is streptococcal toxic antibiotic resistance, some experts recommend that shock syndrome, a severe systemic illness with shock only patients with positive cultures or rapid antigen and organ failure. Recently a new syndrome called tests should be treated. PANDAS (Pediatric Autoimmune Neuropsychiatric In adults, the Centor criteria are most often Disorder Associated with Group A Streptococci) used. The 4 criteria are: has been described. The syndrome involves obses- • tonsillar exudates; sive-compulsive disorder or tic disorder with other • tender anterior cervical adenopathy; neurologic abnormalities of abrupt onset in associa- • fever by history; tion with GAS infections. A clear-cut relationship • absence of cough. of the syndrome with GAS infection has yet to be Persons with three or four of these criteria may established. be treated empirically for GAS. Those with zero or one criterion do not need to be tested or treated. If Prevalence and Distribution two or three criteria are present, testing should be GAS most often affects children and young performed and patients treated only if the test is adults (5-15 years of age). Infection is most positive. common during the winter and early spring. GAS The McIsaac modification of the Centor criteria is the cause of approximately 15-30% of acute has been studied in children. Points for a patient are pharyngitis in children and 5-10% in adults. added based on the following scoring: 148 The Health Care of Homeless Persons - Part I - Streptococcal Pharyngitis (Strep Throat) The Health Care of Homeless Persons - Part I - Streptococcal Pharyngitis (Strep Throat) 149 • history of fever or T>101°F (38oC) +1 • absence of cough +1 Streptococcal • tender anterior cervical adenopathy +1 Pharyngitis (Strep Throat). • tonsillar swelling or exudates +1 The tonsils are • age <15 years +1 swollen and • age > or = 45 years -1 reddened in this child with a fever, tender anterior cervical Children with 0 points are unlikely to have lymph nodes, and an GAS infection and do not need to be tested. Those absence of cough. with 1-3 points should be tested and treatment Photo courtesy based on the test result. Those with 4-5 points have of the CDC a high likelihood of having GAS infection and may be treated empirically or tested and treated if the test children >60 pounds, and 600,000 units in children is positive. < 60 pounds), may be a more practical regimen for those who will have difficulty following the oral Laboratory Diagnosis regimen. If oral therapy is chosen, completion of Throat culture is the gold standard for the the full 10-day course is essential to ensure adequate definitive diagnosis of GAS pharyngitis. Although treatment. Symptoms generally subside before the it takes 24-48 hours to obtain results from a culture, therapy is complete. delaying therapy for this period of time will usually For penicillin-allergic patients, erythromycin not be harmful to patients. In the shelter settings (Eryc TM, E-mycin TM) is the recommended therapy. where follow-up may be difficult, clinicians must Many broader spectrum antibiotics have been make a clinical determination whether to treat shown to be effective in treating GAS pharyngitis, empirically or wait for the culture results. such as azithromycin (ZithromaxTM), clarithromycin Rapid antigen-detection tests are available (BiaxinTM), cephalosporins and amoxicillin- in some settings and can provide an immediate clavulanate (AugmentinTM). However, the use of diagnosis. If the rapid antigen test is positive, treat- these agents is not recommended as they have the ment should be initiated. If the rapid antigen test is potential to increase antibiotic resistance among negative, a throat culture should be obtained. False respiratory pathogens. positive throat cultures and rapid antigen tests may result from a GAS carrier who has pharyngitis due Prevention and Control to another organism, such