Gram Pos Bacilli Flashcards
Discuss the general characteristics of Corynebacterium:
Pleomorphic gram pos rods, non spore forming, chinese letters
What are the cultural characteristics, toxicity test, and media for isolation necessary for identification of C. diphtheria?
Diphtheria toxin - produced by a bacteriophage that blocks protein synthesis
Media: Loefflers serum agar, Cystine-tellurite blood agar (CTBA) a modified hinsdale agar C. diphtheriae appears brown/black from the reduction of tellurite
Toxicity test/Elek test - is an immunodiffusion test in which lines of precip. produce in the agar via toxin produced by the org and a purchased antitoxin. If the pos control precip and the unknown precip lines meet in an arch then the org positive for toxin
What are the metachromatic areas of the Corynebacteruim cell called and what are they stained with?
Babes-Ernst granules or nutrient reserves are stained using Methylene blue
What is a common name for other species of Corynebacterium other than diphtheriae?
Diphtheroids
List seven other species of Corynebacterium other than diphtheriae that have been implicated in patients who are immunocompromised:
Jeikeium, pseudohiphtheriticum, pseudotuberculosis, striatum, ulcerans, urealyticum, xerosis
Discuss the clinical significance of Listeria monocytogenes along with the microscopic and biochemical characteristics:
- Narrow ring B hemolytic on BAP similar to strep agalactiae
- Attacks immunocompromised, pregnant women (premature labor, stillborn), neonates there is a early and a late onset (early 50% mortality, late as meningitis and lower mortality)
- Halophilic, likes increased CO₂
- has a tumbling motility in hanging drop test
- CAMP test with block hemolysis (not arrow)
- Bile esculin and hippurate hydrolysis pos
- Can grow at 4°C
Discuss the clinical significance, source, and characteristics of Erysipelothrix rhusiopathiae:
- Gram pos, non spore forming, pleomorphic rod
- Source: domestic swine - infection through scratches on skin, painful swelling in hands
- H₂S production
- Characteristic lesion
- Nonmotile
- Indole and catalase pos
Lactobacillus is normal flora at what body sites?
Mouth, GI, female genital tract
-doesn’t have a single unique colony morphology can appear as many different ones
Discuss the clinical significance of Bacillus anthracis:
This is the causative agent of Woolsorters disease. Usually humans become infected when handling infected animals
Cutaneous - cuts on hands, small pimple appears 2 to 3 days post exposure followed by necrotic eschar, untreated has 20% mortality
Pulmonary - spores are inhaled and ingested by alveolar macrophages and take them to lymph nodes, 2 to 3 days post inhalation shortness of breath/fever/headaches/cough, secondary symptoms cough/fever/edema/shock and half of patients lead to meningeal symptoms which death occurs within 3 days
Gastrointestinal - ingested spores, <1% of cases diagnosed in US, Upper GI ulcers, Lower GI abdominal pain, nausea, vomiting, Mortality is thought to be 100%
Explain the virulence factors of B. anthracis
Spores - allow it to survive in harsh conditions for years
Capsule
Exotoxins
-Edema toxin + protective factor - edema
-Lethal toxin + protective factor - death
Explain the diagnostic characteristics of B. anthracis:
No hemolysis - white colony with whirling projections (medusa head)
Gram stain - large gram pos rod/spore/bamboo shoots
Biochem - Cat pos, string of pearls
What is the string of pearls phenomenon of B. anthracis?
Inoculate org on agar containing penicillin
-After 3-6 hrs. 37C incubation gram stain - will see large spherical bacilli in chains
Discuss the clinical significance, source, and identification criteria for B. cereus:
Common cause of food poisoning by one of two toxins
Emetic toxin - heat stable enterotoxin, typically caused by rice tables incubation 6 to 8 hrs.
Diarrheal toxin - heat liable enterotoxin, typically caused by meat and vegetables incubation 9-12 hrs
Biochemically opposite of B. anthraces (resistant to penicillin), can cause ocular infections
Describe the chemical significance, colony/stain morphology, and identification tests for Nocardia, Actinomadura and Streptomyces:
Nocardia
Actinomadura
Streptomyces
Nocardia - branched hyphae looking pos rods, colony morphology similar to fungus (7+ days), pulmonary and cutaneous infects in immunocomp., draining sinuses from cutaneous lesions may contain sulfur granules, bread crumb colony, partial acid fast
Actinomadura - causes mycetoma, neg acid fast stain, otherwise similar to Nocardia
Streptomycin - Similar to Nocardia and Actinomycetes, ID by ref lab
What biochemical test differentiates Listeria from Corynebacterium?
Bile esculin
