Bacteriology of Oro-facial Infections

• Group A Streptococcus (S. pyogenes):

  • Always treat with systemic antibiotic therapy if isolated on culture
  • Don't attempt treatment or eradication with topical antimicrobials or disinfectants
  • Infection control hazard organism
  • Public health hazard organism
  • Diagnosis
  • Culture at 24-48 hour incubation at any laboratory
  • 16s PCR at reference laboratory
  • Serology (ASO titre)
  • Complications:
  • Peritonsillar abscess (aka quinsy)
  • Scarlet fever (notifiable illness)
  • Systemic sepsis (notifiable illness)
  • Rheumatic fever
  • Acute glomerulonephritis (GN)
• Scarlet fever (Group A Streptococcus):

  • Notifiable illness
  • Children mainly
  • Strawberry tongue (swollen and bumpy)
  • Sandpaper-like skin rash

  
• Corynebacterium diphtheriae & C. ulcerans:

  • Diphtheria toxin
  • Inhibits protein synthesis
  • Rare, mostly imported illness
  • Non-vaccinated populations
  • Causes
  • Pharyngitis
  • Diphtheria
  • 2-5 days after infection, pseudomembrane forms, risking airway obstruction
  • Later, once toxin has been absorbed, the toxin can cause myocarditis, paralytic symptoms and nephritis
  • High vaccination coverage is crucial to prevent diphtheria
• Arcanobacterium haemolyticum:

  • Appears similar to B-haem Strep on agar plate, but is actually Group positive bacillus on microscopy
  • Formerly classified in the genus Corynebacterium
  • Causes 0.5% - 2.5% of bacterial pharyngitis, especially among adolescents
• Peritonsillar abscess (quinsy):

  • Mixed flora present in 90%
  • Group A streptococcus present in ~30%
  • Please isolate inpatients with suspected quinsy on admission to hospital (infection control hazard)
• Gonorrhoea:

  • Fastidious (hard to culture), Gram-negative diplococci
  • Gram staining can be misleading
  • Culture on special agar
  • PCR on special swabs
  • Anyone who is sexually active can get gonorrhoea (STD/STI) -> GUM (genitourinary medicine)/sexual health referral advised
  • A pregnant woman with gonorrhoea can give the infection to her baby during childbirth
  • Cause infections in the genitals, rectum, and throat
  • Very common infection, especially among young people aged 15-24 years

  
• Syphilis:

  • Caused by Treponema pallidum
  • Spirochaete
  • Not visible on standard microscopy (Gram stain)
  • Non-cultivable in vitro
  • Anyone who is sexually active can get syphilis (STD/STI) -> GUM/sexual health referral advised
  • A pregnant woman with syphilis can give the infection to her baby during childbirth
  • Diagnosis:
  • Serology
  • Combination of tests
  • Treponemal and non-treponemal tests
  • PCR using special swabs
• Patients with syphilis should be screened for HIV, gonorrhoea, and chlamydia.
• Primary syphilis classically presents as a single, painless, indurated genital ulcer (chancre) - this presentation is only 31% sensitive; lesions can (sometimes) also be painful, multiple, and extra-genital

  
• Untreated syphilis can lead to chronic, progressive disease

  
• Mycobacterium tuberculosis (TB):

  • Acid-alcohol fast bacilli
  • Massive problem globally (billions of people infected)
  • UK ~5-10 cases reported/100,000 population
  • Oral mucosal lesions
  • Usually secondary to pulmonary infection
  • Pain and ulceration
  • More commonly in posterior part of mouth
  • Cervical lymphadenopathy
  • May develop abscesses and sinuses
  • Biopsy
  • Histology
  • Culture
  • Refer to respiratory/ID team
  • Triple/quadruple antituberculous therapy
• Salivary gland infection:

  • Viral infection
  • Mumps (notifiable illness)
  • Bacterial infections
  • Polymicrobial
  • Associated with reduced salivary flow and/or abnormal anatomy/blockages