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Bacterial structure and functions
Bacillus anthracis (Anthrax)
Bacillus cereus (Food poisoning)
Corynebacterium diphtheriae (Diphtheria)
Clostridium botulinum (Botulism)
Clostridium difficile (Pseudomembranous colitis)
Clostridium tetani (Tetanus)
Streptococcus agalactiae (Group B Strep)
Streptococcus pyogenes (Group A Strep)
Bartonella henselae (Cat-scratch disease and Bacillary angiomatosis)
Legionella pneumophila (Legionnaires disease and Pontiac fever)
Salmonella typhi (typhoid fever)
Yersinia pestis (Plague)
Vibrio cholerae (Cholera)
Bordetella pertussis (Pertussis/Whooping cough)
Francisella tularensis (Tularemia)
Haemophilus ducreyi (Chancroid)
Gardnerella vaginalis (Bacterial vaginosis)
Coxiella burnetii (Q fever)
Ehrlichia and Anaplasma
Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species
Borrelia burgdorferi (Lyme disease)
Borrelia species (Relapsing fever)
Treponema pallidum (Syphilis)
0 / 9 complete
0 / 1 complete
labs/findings p. 720
oral infections p. 183
pigment production p. 127
Actinomyces israelii, or just A. israelii, is a gram-positive rod-shaped bacteria that causes a human infection called actinomycosis.
Calling this bug actinomyces implies that it’s morphologically similar to fungus, because both form microscopic branching filaments (or mycelium), while the word Israelii comes from James Adolf Israel, the German surgeon who first described it.
OK, A. israelii is a rod-shaped gram-positive bacteria, we’ve got that part down, but what this means is that it goes purple when gram-stained.
When there’s many of them, they arrange themselves in the shape of purple branching filaments.
They are anaerobes, meaning they grow better without oxygen, they are also non-motile, and don’t form spores.
But wait… that sounds exactly like Nocardia, another group of rod shaped, gram-positive, filamentous bacteria with a lot of other similar features.
To distinguish them, an acid-fast stain, also called Ziehl-Neelsen stain is done.
With this test, a red dye called carbon fuchsin, binds to lipids in the cell wall, coloring them red.
Then alcohol is applied to wash out any dye that hasn’t colored bacteria, and a second dye, methylene blue, is applied.
Another difference is that A. Israelii is catalase negative, so it doesn’t make an enzyme called catalase, whereas Nocardia is catalase positive.
Finally, A. israelii is cultivated on blood agar, and then incubated in anaerobic conditions.
Alright, now, A. Israelii can asymptomatically colonize the oral cavity, particularly the space between the roots and gums, as well as the pharynx, where they gather around the tonsils, and also the intestinal tract, and the urogenital tract, where they coexist with other commensal bacteria.
Actinomyces israelii is a type of bacteria that typically inhabits the mouth, skin, and gastrointestinal tract. However, they can also be found in other body sites, such as the lungs and the genital tract. These bacteria are normally harmless, but they can cause infections if they enter the body through a cut or wound.
A. israelii infections are more common in immunocompromised individuals, such as those with HIV/AIDS or cancer. Symptoms of A. israelii infections depend on the infected organs and can include fever, lower abdominal pain, chronic cough, and unusual vaginal discharge.
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