Tonsillitis is a common disease of childhood and adolescence. The diagnosis of tonsillitis generally requires the consideration of Group A beta-hemolytic Streptococcus (GABHS) infection. However, numerous other bacteria alone or in combinations, viruses and other infections and non-infectious causes should be considered. Recognition of the cause and choice of appropriate therapy are of utmost importance in assuring rapid recovery and preventing complications.

Penicillin is currently the first-choice treatment for GABHS pharyngotonsillitis. However, the growing failure of penicillin to eradicate GABHS is of concern. This website discusses the potential causes of penicillin failure ( i.e. the presence of beta-lactamse producing bacteria that can “protect” GABHS from penicillins) and methods to overcome them. It also discusses the role of anaerobic bacteria in tonsillitis and its complications.

Clinical Findings and Diagnosis of Paryngo-tonsillitis

Clinical findings
Pharyngo-tonsillitis (PT) has generally a sudden onset, with fever and sore throat, nausea, vomiting, headache and rarely abdominal pain. 

 At an early stage redness of throat and tonsils is observed, and the cervical lymph glands become enlarged.  The clinical manifestations may vary by causative agent (see Microbiological causes section ), but are rarely specific.  Erythema is common to most agents, however the occurrence of ulceration, petichiae, exudation or follicles varies. The common features are:  exudative pharyngitis in GAHBS infection, ulcerative lesions in enteroviruses, and membranous pharyngitis in Cdiphtheriae.  Petechiae can often be seen in GABHS, Epstein-Barr, measles and rubella viruses infections.

Viral disease is generally self-limited and lasts 4 to 10 days and are generally associated with the presence of nasal secretions.  Bacterial illness lasts longer if untreated.  The most unique features of anaerobic tonsillitis or PT are enlargement and ulceration of the tonsils associated with fetid or foul odor and the presence of fusiform bacilli, spirochetes, and other organisms on Gram stain.

Throat culture obtained by throat swab of both tonsilar surfaces and the posterior pharyngeal wall, plated on sheep blood agar media is the standard.  Incubation in anaerobic condition and use of selective media can increase the recovery rate. A single throat culture has the sensitivity of 90%-95% in detection of GABHS in the pharynx. False negative results can occur in patients who received antibiotics. Throat culture generally identify GABHS by direct growth may take 24 to 48 hours. Re-examination of plates at 48 hours is advisable. The use of bacitracin disk provides presumptive identification.  Attempts to identify beta‑hemolytic streptococci, other than Group A, may be worth while in older individuals. Commercial kits containing group specific antisera are available for identifying the specific streptococcal group.

Obtaining tonsillar culture

However, these rapid methods It is therefore recommended that a bacterial culture is performed
Rapid methods for detection of GABHS that take10 to 60 minutes are available.  They are more expensive than the routine culture but allow for rapid administration of therapy and reduction of morbidity.   Antigen tests depend on the detection of the surface Lancefield group A carbohydrate. Newer tests use nucleic acid (DNA) probes and   polymerase chain reaction (PCR) with greater sensitivity and identify more pathogenic serotypes of GABHS. Early kits show low sensitivity, but the current ones have 85 to 90% sensitivity but are still associated with 5-15% false negative results.  It is therefore recommend that a bacterial culture is performed in instances where the rapid streptococcal test is negative. 

                                              Rapid method for detection of GABHS

More than 10 colonies of GABHS per plate are considered to represent a true infection rather than colonization. However, using the number of colonies of GABHS in the plate as an indicator for the presence of true infection, is difficult to implement, as there is overlap between carriers and infected individuals.

 Blood agar plate showing heavy growth of Group A beta hemolytic streptococci

A rise in ASO streptococcal antibodies titer after 3-6 weeks can provide retrospective evidence for GABHS infection, and assist in differentiating between the carrier state.  Determining the ASO titers is indicated when there is a need to prove the occurrence of GABHS infection.

Other pathogens should be identified in specific situations, when no GAHBS is found or when a search of other organisms is warranted.  Since many of the other potential pathogens are part of the normal pharyngeal flora, interpretation of the data is difficult.
Attempts to identify corynebacteria should be made whenever a membrane is present in the throat.  Cultures should be obtained from beneath the membrane, using a special moisture reducing transport media.  A Loeffler slant, a tellurite plate and a blood agar plate should be inoculated.  Identification by fluorescent antibody technique is possible.
Viral cultures, or rapid tests for some viruses (i.e. Respiratory Syncytial Virus) are available.  A heterophile slide test or other rapid tests for Infectious Mononucleosis can provide a specific diagnosis.

Suggested reading

Bisno AL, Gerber MA, Gwaltney JM Jr, Kaplan EL, Schwartz RH.  Practical guidelines for the diagnosis and management of group A streptococcal pharyngitis: a practice guideline. Infectious Diseases Society of America. Clin Infect Dis 2002, 35;113-125.
Brook I. The role of anaerobic bacteria in tonsillitis. Int J Pediatr Otorhinolaryngol. 2005 ;69:9-19.
Lindroos R.  Bacteriology of the tonsil core in recurrent tonsillitis and tonsillar hyperplasia--a short review. Acta Otolaryngol Suppl. 2000;543:206-8.
Pichichero ME, Cohen R.  Shortened course of antibiotic therapy for acute otitis media, sinusitis and tonsillopharyngitis.  Pediatr Infect Dis J. 1997;16:680-95.
Richter SS, Heilmann KP, Beekmann SE, Miller NJ, Miller AL, Rice CL, Doern CD, Reid SD, Doern GV. Macrolide-resistant Streptococcus pyogenes in the United States, 2002-2003. Clin Infect Dis.;41:599-608, 2005.
Shulman ST.  Value of new rapid tests for the diagnosis of group A streptococcal pharyngitis.   Pediatr Infect Dis J. 1995;14:923-4.
Shulman ST, Stollerman G, Beall B, Dale JB, Tanz RR. Temporal changes in streptococcal M protein types and the near-disappearance of acute rheumatic fever in the United States. Clin Infect Dis. 2006;42:441-7.