What microorganisms may produce acute pharyngitis? Discuss the microbiological investigations and clinical management of this condition.

Outline:
•	Etiological agents:
- virus: type A coxsackievirus, adenovirus, herpes simplex virus, Epstein-Barr virus & cytomegalovirus.
- bacteria: streptococcus pyogenes, corynebacterium diphtheriae, neisseria gonorrhoeae & chlamydia trachomatis.
- fungus: candida albicans.
•	Investigations:
- culture on blood agar: streptococcus pyogenes.
- culture on Thayer-Martin medium: neisseria gonorrhoeae
- Paul-Bunnell test: Epstein-Barr virus
•	Management:
- symptomatic relief for viral infections.
- antibiotics for bacterial infections: penicillin G, erythromycin.
- use antimicrobial therapy only as required.

Suggested Answer:

	Pharyngitis is an acute inflammation of the throat (pharynx), resulting in pain on swallowing and swollen, red pharyngeal mucosa. It often involves lymphoid tissues of the posterior pharynx and lateral pharyngeal bands. The etiology can be bacterial, viral and fungal infections as well as noninfectious etiologies such as smoking. Most cases are due to viral infections and accompany a common cold or influenza. Type A coxsackieviruses can cause a severe ulcerative pharyngitis in children (herpangina), and adenovirus and herpes simplex virus, although less common, also can cause severe pharyngitis. Pharyngitis is a common symptom of Epstein-Barr virus and cytomegalovirus infections. 
Group A beta-hemolytic streptococcus or Streptococcus pyogenes is the most important bacterial agent associated with acute pharyngitis and tonsillitis. Corynebacterium diphtheriae causes occasional cases of acute pharyngitis, as do mixed anaerobic infections (Vincent's angina), Corynebacterium haemolyticum, Neisseria gonorrhoeae, and Chlamydia trachomatis. Outbreaks of Chlamydia pneumoniae (TWAR agent) causing pharyngitis or pneumonitis have occurred in military recruits. Mycoplasma pneumoniae and Mycoplasma hominis have been associated with acute pharyngitis. Candida albicans, which causes oral candidiasis or thrush, can involve the pharynx, leading to inflammation and pain. 
Pharyngitis usually presents with a red, sore, or "scratchy" throat. An inflammatory exudate or membranes may cover the tonsils and tonsillar pillars. Vesicles or ulcers may also be seen on the pharyngeal walls. Depending on the pathogen, fever and systemic manifestations such as malaise, myalgia, or headache may be present. Anterior cervical lymphadenopathy is common in bacterial pharyngitis and difficulty in swallowing may be present. 
Aetiological clues on the causative agent include conjunctivitis (adenovirus), lethargy, malaise and tonsillar exudate (Epstein-Barr virus), posterior palatal ulcers (coxsackievirus), abrupt onset, ‘doughnut’ pharyngeal lesions and beefy uvula (S. pyogenes) or grey pharyngeal pseudomembrane (C. diphtheriae). 
Viral pharyngitis is a self-limiting condition that does not usually require a specific aetiological diagnosis. When Epstein-Barr virus infection is suspected, full blood count, blood flim and Paul-Bunnell test for heterophile antibodies should be requested. The goal in the diagnosis of pharyngitis is to identify cases that are due to group A beta-hemolytic streptococci, as well as the more unusual and potentially serious infections. The various forms of pharyngitis cannot be distinguished on clinical grounds. Streptococcus pyogenes is detected either by culture on blood agar and subsequent latex agglutination reaction for group-specific polysaccharide, or by direct antigen detection.
Thayer-Martin medium is used if N gonorrhoeae is suspected. Viral cultures are not routinely obtained for most cases of pharyngitis. Serologic studies may be used to confirm the diagnosis of pharyngitis due to viral, mycoplasmal or chlamydial pathogens. Rapid diagnostic tests with fluorescent antibody or latex agglutination to identify group A streptococci from pharyngeal swabs are available. Gene probe and polymerase chain reaction can be used to detect unusual organisms such as M pneumoniae, chlamydia or viruses but these procedures are not routine diagnostic methods. 

Symptomatic treatment is recommended for viral pharyngitis. The exception is herpes simplex virus infection, which can be treated with acyclovir if clinically warranted or if diagnosed in immunocompromised patients. The specific antibacterial agents will depend on the causative organism, but penicillin G is the therapy of choice for streptococcal pharyngitis. An alternative is erythromycin. Treatment may not alter the course of the primary pharyngeal infection, but it should reduce the risk of major non-infective sequelae such as rheumatic heart disease and poststreptococcal glomerulonephritis. Mycoplasma and chlamydial infections respond to erythromycin, tetracyclines and the new macrolides. 

The primary care physician needs to identify those patients with acute pharyngitis who require specific antimicrobial therapy and to avoid unnecessary and potentially deleterious treatment in the large majority of patients who have a benign, self-limited infection that is usually viral. In most cases, differentiating between these two types of infection can be accomplished easily if the physician considers the epidemiologic setting, the history, and the physical findings, plus the results of a few readily available laboratory tests. When antimicrobial therapy is required, the safest, narrowest-spectrum, and most cost- effective drugs should be used.