Synonym

Throat culture and sensitivity

Tubes

• Sterile swabs and/or sterile capped syringe/tube culture transport container (provided by lab)
• Specimens:
• Throat swab
• Throat washings
• May also obtain specimen for rapid streptococcal test at same time (sometimes with the same swab; check with your laboratory)

Additional information

• For adult patients:
• The patient is instructed to tilt the head back and close eyes
• Oral cavity/throat should be well illuminated, checked for inflamed areas by depressing the patient's tongue with a tongue blade
• Rotate the swab firmly and gently over the posterior pharynx, both tonsils or fossae, and on areas of inflammation, exudation, or ulceration
• Avoid touching the teeth, cheeks, tongue or lips with the swab
• Immediately place swab in culture tube so that it comes in contact with the culture medium
• For pediatric patients:
• The patient is instructed to gargle with 5-10 mL of sterile saline solution and then expectorate it into a sterile cup
• The specimen in the cup is transferred to culture tube/container and tightly capped
• Use a sterile throat culture kit with a polyester-tipped applicator or swab and a sterile container or tube of culture medium (provided by lab)
• Because most patients gag or cough, the collector should wear a facemask for protection
• Laryngospasm may occur after culture if patient has epiglottiditis or diphtheria. Keep resuscitation equipment nearby
• Immediately send the specimen to the lab
• Refrigerate the throat culture if delay is expected
• For gonorrhea do not allow specimen to dry, avoid refrigeration, and immediately plate the specimen on appropriate media
• Note date, time, patient’s details, and recent antimicrobial therapy (specimen before beginning microbial therapy is preferred) on lab request form
• Indicate suspected organism especially Corynebacterium diphtheriae (requires 2 swabs and special growth medium), Bordetella pertussis (requires nasopharyngeal culture and special growth medium), and N. meningitidis (requires enriched selective media)

Info

• This test is performed to isolate and identify pathogenic microorganisms (bacteria, fungi or viruses) that cause infections of the throat
• It is typical that sensitivity testing follow a positive culture (except in the case of organisms of well known an consistent sensitivity to antimicrobials, such as Group A Beta Hemolytic Streptococcus) to identify the which antimicrobials an isolated organism is sensitive to
• Normal throat flora includes
• Nonhemolytic and alpha-hemolytic streptococci
• Neisseria species (except meningititis or gonorrhea)
• Staphylococci
• Diphtheroids
• Hemophilus species
• Pneumococci
• Yeasts
• Enteric gram-negative rods
• Spirochetes
• Veillonella species
• Micrococcus species

Clinical

• The clinical utility of throat culture includes:
• Aids in the diagnosis of bacterial infections such as tonsillitis, diphtheria, Gonococcal pharyngitis, Bordetella pertussis, or CMV
• Aids in the diagnosis of upper respiratory infections resulting in bronchitis, pharyngitis, croup, and influenza
• Isolate and identify group A -hemolytic streptococci (GABHS) as the cause of streptococcal throat infection, acute glomerulonephritis, scarlet fever, or rheumatic fever
• To screen asymptomatic carriers of pathogens such as:
• Neisseria meningitides
• Beta-hemolytic streptococcus
• Corynebacterium diphtheriae
• Staphylococcus aureus
• Aids in the diagnosis of thrush (candidal infection)
• Aids in the diagnosis of viral infection (adenovirus, enterovirus)
• Common potential pathogenic organisms detectable on throat culture include:
• Bacterial
• Streptococcus pyogenes (Group A beta-hemolytic streptococci/GABHS)
• Bordetella pertussis
• Arcanobacterium haemolyticus
• Mycoplasma pneumoniae
• Chlamydia pneumoniae
• Neisseria gonorrheae
• Corynebacterium diphtheriae
• Leptotrichia buccalis
• Viral
• Adenovirus
• Coxsackieviruses A and B virus
• Cytomegalovirus (CMV)
• Enterovirus
• Epstein-Barr virus [Infectious mononucleosis]
• Herpes simplex
• HIV-1
• Parainfluenza virus
• Reovirus
• Rhinovirus
• Fungal
• Candida albicans
• Organisms commonly present in the normal oropharynx include:
• Actinomyces israelii (tonsils)
• Bacteroides sp (tonsils)
• Candida albicans
• Candida sp
• Corynebacterium sp (diphtheroids)
• E. coli
• Enterococci
• Fusobacterium sp (tonsils)
• Haemophilus influenzae
• Haemophilus parainfluenzae
• Klebsiella sp
• Neisseria meningitidis
• Nonhemolytic streptococci
• Proteus sp
• Staphylococcus aureus
• Staphylococcus epidermidis
• Streptococcus pneumoniae
• Streptococcus pyogenes
• Veillonella sp
• Pharyngitis is an infection, inflammation, or irritation of the pharynx and/or tonsils due to virus (40-60% cases), bacteria (5-40% cases), or other causes (allergy, fungal, trauma, toxins, smoking, gastroesophageal reflux, and neoplasia), and is seen more often in children than adults
• The clinical presentation of pharyngitis depends on the causative agent and includes:
• Cough (Usually viral or atypical bacteria)
• Headache (GABHS or mycoplasma infection)
• Rhinorrhea (viral)
• Fever (high grade in coxsackievirus A, coxsackievirus B, herpes simplex, GABHS infection, HIV-1, infectious mononucleosis, and Cytomegalovirus)
• Dehydration (due to odynophagia)
• Conjunctivitis (adenovirus)
• Scleral icterus (infectious mononucleosis)
• Tonsillopharyngeal/palatal petechiae (GABHS infections and infectious mononucleosis)
• A tonsillopharyngeal exudate [streptococcal infectious (15-30%), mononucleosis, viruses (rhinovirus, coronavirus, adenovirus, herpesvirus; 30%), and occasionally in M pneumoniae, C pneumoniae, A haemolyticus, and N gonorrheae
• Membranous coating (C diphtheriae, C pseudodiphtheriticum, Epstein-Barr virus)
• Oropharyngeal vesicular lesions (coxsackievirus and herpesvirus)
• Lymphadenopathy
• Moderate-Severe: streptococcus, infectious mononucleosis
• Mild-Moderate: Viral infections, atypical bacterial, sometimes with streptococcus
• Lower respiratory tract infection (M pneumoniae or C pneumoniae)
• Complications of pharyngitis include:
• Peritonsillar abscess
• Epiglottitis
• Lemierre syndrome (fusobacterium sp.), which can progress to sepsis and multi-organ failure
• Toxic shock syndrome (Streptococcal)
• Acute glomerulonephritis
• Scarlet fever
• Rheumatic fever

Additional information

• Culture results are considered in relation to patient's clinical presentation, recent antimicrobial therapy, and amount of normal flora
• Throat washings provides more specimen than a throat swab and is more definitive for viral isolation
• Factors interfering with test results include:
• Recent or current antimicrobial therapy (possible false-negative)
• Using antiseptic mouthwashes before the culture is taken
• Contamination with oral flora
• Improper collection technique
• >15-min delay in sending specimen to lab
• Related laboratory tests include:
• Cold agglutinins
• Complete blood count (CBC)
• C-reactive protein (CRP)
• Erythrocyte sedimentation rate (ESR)
• Fluorescent monoclonal antibody test for C pneumoniae
• Gram stain
• Monospot test
• Rapid tests for group A streptococcus

Nl Result

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

Normal: Negative/Normal oral flora

High Result

Positive findings are associated with infection with the isolated pathogenic organism

References

• eMedicine from WebMD®. Pharyngitis. [Homepage on the Internet] ©1996-2006. Last updated on April 21, 2005. Last accessed on June 30, 2007. Available at URL: http://www.emedicine.com/EMERG/topic419.htm
• Laboratory Corporation of America. Upper Respiratory Culture, Routine. [Homepage on the internet]©2007. Last accessed on June 30, 2007. Available at URL: http://www.labcorp.com/datasets/labcorp/html/chapter/mono/mb014700.htm
• Morris DP et al. Bacterial biofilm in upper respiratory tract infections. Curr Infect Dis Rep. 2007 May;9(3):186-92.
• van der Veen EL et al. Optimal site for throat culture: tonsillar surface versus posterior pharyngeal wall. Eur Arch Otorhinolaryngol. 2006 Aug;263(8):750-3. Epub 2006 May 4.
• Van Staaij BK et al. Does the tonsillar surface flora differ in children with and without tonsillar disease? Acta Otolaryngol. 2003 Sep;123(7):873-8.
• Vincent MT et al. Pharyngitis. Am Fam Physician. 2004 Mar 15;69(6):1465-70. Available at URL: http://www.aafp.org/afp/20040315/1465.html