Nurudeen++kallon

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The most common and important bacterial cause of pharyngitis is //[|Streptococcus pyogenes]//. When suspected, bacterial pharyngitis can be confirmed with routine diagnostic tests and treated with various antibiotics. If left untreated, //S pyogenes// pharyngitis may lead to local and distant complications. To a lesser extent, bacteria other than //S pyogenes// are known to cause pharyngitis, and these are discussed in [|Causes].=====

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Beta-hemolytic streptococci have the ability to cause large zones of hemolysis on blood agar, aiding in microbiological identification.[[javascript:showcontent('active','references');|1]] Lancefield antigens, carbohydrates in the cell wall, provide further differentiation of streptococci. //S pyogenes,// which contains group A antigens and displays beta-hemolysis, is the most common species referred to as a group A beta-hemolytic streptococci (GABHS). //Streptococcus dysgalactiae// subspecies //equisimilis// and some species from the //Streptococcus anginosus// group may share laboratory characteristics with //S pyogenes// but do not commonly cause human disease.=====

Causes 
 * Viruses cause the vast majority of pharyngitis cases. Common agents include coronavirus, [|rhinovirus], [|adenovirus], [|parainfluenza], [|influenza], [|Epstein-Barr virus], [|cytomegalovirus], and [|HIV].
 * GABHS accounts for 15%-30% of pharyngitis cases in children and 5%-10% of cases in adults.
 * The following are bacteria other than GABHS that may cause pharyngitis:
 * Group C and G streptococci: Like GABHS, these pathogenic bacteria cause beta-hemolysis, form large colonies, and produce an M protein, yet neither are detected with rapid antigen detection tests (RADTs). Pharyngitis caused by either of these non-GABHS streptococci have a clinical presentation similar to that of GABHS pharyngitis and should be considered in patients with worsening symptoms and an initial negative RADT result. Diagnosis can be achieved with a normal bacterial throat culture and identification based on Lancefield antigens.These bacteria are an uncommon cause of acute pharyngitis in pediatric patients.
 * //Arcanobacterium haemolyticum//: This gram-positive rod accounts for between 0.5% and 3% of pharyngitis cases. Clinical manifestations are similar to those of GABHS pharyngitis, although about half of patients with //A haemolyticum// pharyngitis develop a rash, which typically starts on the extensor surfaces; spares the palms, soles, and head; and moves centrally to involve the trunk with a maculopapular or scarlatiniform appearance. //A haemolyticum// exhibits variable susceptibility to penicillin and is identified more easily on human or rabbit blood agar than on sheep agar, the media traditionally used to identify GABHS.
 * //[|Neisseria gonorrhoeae]//: Infection with this pathogen is associated with oral-genital contact and is often asymptomatic. //N gonorrhoeae// may be identified using chocolate or Thayer-Martin agar. Nucleic acid amplification tests from throat rinses appear to be a promising alternative. Because of increasing rates of fluoroquinolone resistance, ceftriaxone is now the only recommended option for treatment of pharyngeal gonorrhea. Treatment aimed at //[|Chlamydia trachomatis]// is also recommended, since co-infection is common.
 * //[|Mycoplasma pneumoniae]//: This atypical bacterium is increasingly being identified as an etiologic agent of pharyngitis. //M pneumoniae// pharyngitis may be associated with pulmonary findings.
 * //Yersinia// species: Both //[|Yersinia enterocolitica]// and //Yersinia pestis// may cause disease. Pharyngeal plague has been linked to the consumption of camel meat.
 * //Chlamydia trachomatis// and //Chlamydophila pneumoniae//: Both of these organisms are rare causes of pharyngitis.
 * //[|Corynebacterium diphtheriae]//: Toxigenic strains of this gram-positive bacillus are common causes of croup. Young patients with //C diphtheriae// pharyngitis often exhibit inspiratory stridor, sternal retraction, and a barking cough. In severe cases, a membrane formation may impair breathing. The incidence of //C diphtheriae// pharyngitis in developed countries is low because of high immunization rates.

Medication  The goals of pharmacotherapy are to eradicate the infection, to reduce morbidity, and to prevent complications.

Antibiotics Oral penicillin is currently the drug of choice for GABHS pharyngitis. Amoxicillin remains a reliable alternative and offers advantages in terms of easier dosing and increased palatability. Tetracyclines and trimethoprim/sulfamethoxazole should not be used to treat GABHS pharyngitis owing to higher rates of resistance.

Penicillin G benzathine (Bicillin L-A, Permapen) Interferes with synthesis of cell wall by binding to penicillin-binding proteins. Penicillin is the drug of choice to treat GABHS pharyngitis, as recommended by expert committees of the American Heart Association, American Academy of Pediatrics, and the Infectious Disease Society of America, because of proven efficacy, safety, narrow spectrum, and low cost. Preferred for patients unlikely to complete a full 10-d PO course. //S pyogenes// remains universally sensitive to penicillin.

Penicillin VK (Beepen VK)
Treatment of choice for GAS pharyngitis, as recommended by expert committees of the American Heart Association, American Academy of Pediatrics, and the Infectious Disease Society of America, because of its proven efficacy, safety, narrow spectrum, and low cost. Inhibits biosynthesis of cell wall by binding to penicillin-binding proteins. Bactericidal against sensitive organisms when adequate concentrations are reached and most effective during stage of active multiplication. Inadequate concentrations may be ineffective. GABHS remains uniformly susceptible in vitro.

Amoxicillin (Amoxil, Biomox, Trimox) Interferes with synthesis of cell wall mucopeptides by binding to penicillin-binding proteins. Often used in place of oral penicillin VK in young children. Efficacy equal to penicillin, and often chosen because of the unpalatability of the penicillin susp. Azithromycin (Zithromax)

Inhibits RNA-dependent protein synthesis at the 50s ribosome. Can be given as a single daily dose, is better tolerated than erythromycin in patients who are allergic to penicillin, and is effective in a 5-d course. However, much more expensive and should be avoided as first-line therapy in patients with streptococcal pharyngitis. Sporadic resistance has been reported.

Erythromycin (E.E.S., E-Mycin, Ery-Tab, Erythrocin) Inhibits RNA-dependent protein synthesis at the 50s ribosome. An option in those with severe allergic reactions to beta-lactam antibiotics. Sporadic resistance has been reported.

**Precautions**
Liver disease; estolate formulation may cause cholestatic jaundice; adverse GI effects are common; discontinue use if nausea, vomiting, malaise, abdominal colic, or fever occur

Clindamycin (Cleocin) Belongs to the lincosamide class of antibiotics. Binds to the 50s ribosome and prevents bacterial protein synthesis. Is an option for symptomatic patients with multiple, recurrent episodes of pharyngitis proven by culture or rapid antigen testing. Adjust dose in severe hepatic dysfunction; no adjustment necessary in renal insufficiency; associated with severe and possibly fatal colitis by allowing overgrowth of //Clostridium difficile//
 * Precautions**

Cephalexin (Keflex) First-generation cephalosporin that arrests bacterial growth by inhibiting bacterial cell wall synthesis. Bactericidal activity against rapidly growing organisms. Oral cephalosporins are highly effective for streptococcal pharyngitis, and several studies have found them to have slightly higher eradication rates than those of penicillin. Second-line agents in the treatment of patients with GABHS pharyngitis.

Posterior pharynx with petechiae and exudates in a 12-year-old girl. Both the rapid antigen detection test and throat culture were positive for group A beta-hemolytic //Streptococcus.//