Bacillus, Cornynebacteria, Listeria Flashcards
Bacillus:
Bacillus anthracis-
Bacillus cereus -
Bacillus stearothermophilus
Bacillus anthracis:
Zoonosis
Human pathogen
Isolation considered to be clinically significant
Bacillus cereus:
Environmental organism
Contaminates food
Common cause of food poisoning
Bacillus stearothermophilus:
Tolerates very high temperatures
Used for quality control of autoclaves
Bacillis anthracis
large bacilli of 1-3 um Signle or paired in clinical isolates In vitro - prominent capsule Highly resistant spores gram positive
Virulence factors:
antiphagocytic capsule
toxin - oedema & death
Cutaneous anthrax - 20% mortalisty
Inhalation or GI anthrax - high mortality
Anthrax - diagnosis
Specimen - Aspirate or swab from from cutaneous lesion blood culture sputum Lab investigation: Gram stain culture identification of isolate
Anthrax - treatment & prevention
Peniciillin: (tetracycline/chloramphenicol) Erythromycin, clindamicin Prevention: Vaccination of animal herds Proper disposal of carcasses Active immunisation with live attenuated bacilli
Bacillus cereus
Large, motile, saprophytic bacillus
heat resistant spores
Pre formed heat and acid stable toxin (Emetic syndrome)
Heat labile enterotoxin ( diarrhoeal disease)
Lab diagnosis - demonstration of large number of bacilli in food
Emetic form
Incubation period 6 hours
lasts 20-36 hours
Corynebacteria diptheriods
Diptheroids: Normal flora of the skin Usual contaminants of samples Can cause diease in compromised host C. ulcerans C. haemolyticum C. jeikeium
Corynebacterium diphtheriae
Normal flora of nasopharynx in 10% of people
Dipthereia causec caused when infected by lysoenic bacteriophages
causes localised inflammation (pseudomembrane, greyish white exudate) and generalized toxaemia
Prevelent in babies after 3-6 months
Rare in developed countries a disease of 3rd world countries
spread through droplets
Effect of toxins:
Local
General
toxaemia acts on myocardium and on motor nerves and adrenals
Complications:
pseduomembrane may extend to larynx and cause obstruction
myocartidis/polyneuropathy
degenerative changes in the liver, kidney’s
other Corynebacteria
Called diptherioids and may occasionally cause disease
C. ulcerans toxigenic strains may produce a disease similar to, but
less severe than diphtheria.
C. jeikeium commonly cause infections in those with
underlying disease. Diseases include bacteremia,
meningitis, peritonitis, wound infections, etc. It is
becoming more and more of a problem with the large number of
immunocompromised individuals found in hospitals.
C. pseudotuberculosis found in those with exposure to animals. Can
cause pneumonia or lymphadenitis. Produces a different exotoxin
than C. diphtheriae.
Listeria monocytogenes
Gram + beta-hemolytic bacillis
multiply at refrigerator temperatures (4oc)
Listeria habitiat
intestinal tract of mammals and birds
soil
soft cheeses and unwashed raw vegetables
raw or undercooked food of animal origin
Listeriosis
Neonates, elderly & immunocompromised
Neonates, elderly & immunocompromised
Granulomatosis infantiseptica
Transmitted to fetus transplacentally
Early septicemic form: 1-5 days post-partum
Delayed meningitic form: 10-20 days following birth
Intracellular pathogen
Cell-mediated and humoral immunity develop
Only cell-mediated immunity is protective
