Actinomyces israelii is a bacteria that is found in the mouths of nearly all healthy children by two years of age.  It may also be found in the colon and female genital tract.  Disruption of the protective mucosal area can provide an entry point for Actinomyces israelii to invade and cause a localized infection (abscess).  Produces characteristic "sulfur" granules in pus (bright yellow clumps).

 

Diseases

• Actinomycosis (a painful collection of pus usually found near the teeth, neck, or jaw)

Habitat & Transmission

• Lives in normal, healthy mouths, especially in the crevices around the teeth
• Likes enclosed spaces without oxygen
• Not usually contagious, but it can be transmitted by a human bite!
• Has not been found in the environment

Weapons/Defenses

• Able to form an abscess to hide from the immune system
• Otherwise, it has no significant defenses or weapons
• May allow other bacteria to enter the abscess, worsening the infection

Weaknesses

• Actinomyces israelii is usually a harmless, slow-growing freeloader of the mouth
• It takes a long time to form an abscess
• Susceptible to many different antibiotics (including penicillin)

Notes

• For people who rarely brush their teeth or with weak immune systems, they can form an abscess. 
• Actinomyces will recruit the help of other more dangerous bacteria to cause problems.
• Person-to-person transmission has not been demonstrated (and almost everyone has this bacteria in the mouth anyway)
• Sometimes confused with a cancer growth