Gram Positive Bacilli and Gram Negative Cocci (pics) Flashcards
Bacillus anthrasis
Pathogenesis of B. anthracis
Inhalational (Pulmonary) Anthrax/Woolsorter’s
Disease
Chest x-ray. There is widening of the mediastinum.
Dried smear of B. anthracis
LEFT: 5% Blood agar plate; RIGHT: Bicarbonatecontaining medium in 5-7% CO2
LEFT: organisms produce nonhemolytic gray to white, tenacious colonies with a rough texture and a ground-glass appearance.
RIGHT: Mucoid colonies can be appreciated because of the presence of capsule
Blood agar plate
Comma-shaped outgrowths (Medusa head, “curled hair”) may project from the colony (if viewed in high magnification)
Agar with bacteriophage
Lysis of B. anthracis by lytic phage gamma.
Bacillus cereus.
Corynebacterium diphtheriae
LEFT: Gram stain; RIGHT: Metachromatic Granules stain
Pathogenesis of C. diphtheriae
Corynebacterium Gravis, Intermedius, and Mitis in Chocolate agar added with tellurit
Note the BLACK color of the colonies formed as compared to the white colonies seen in blood agar alone
C. diphtheriae in potassium tellurite plate
Note the presence of the grayish-black colonies indicating growth of the bacteria
Loeffler slant
C. diphthteria grows on this and presence of cream to yellow colonies indicates the presence of the organism
Elek’s Toxigenicity Test
Filter paper contains antitoxin, (+) control produces toxin, (-) control does not produce toxin. Antitoxin from the filter paper and the toxin from the test organism migrate in the agar and produces precipitate in the area where they are specific.
Listeria monocytogenes in a blood culture
Note that this bacteria is facultative intracellular so some of the organism are seen inside and outside of the RBCs.
Life cycle of Listeria monocytogenes
Virulence factors are encircled in yellow.
Gram staining of Neisseria meningitidis
Notice the bacteria present in the cytoplasm of the PMNs (the cytoplasm does not stain so only the bacteria can be seen)
