Shared Flashcard Set

Details

Corynebacterium, Listeria, Bacillus
and other facultative (aerobic) Gram-positive rods
52
Medical
Graduate
10/10/2009

Additional Medical Flashcards

 


 

Cards

Term
What are the Gram stain characteristics of Corynebacterium?
Definition
  • Gram-positive rods
  • not acid-fast
  • pleomorphic shapes resembling "Chinese letters"
Term
What is the main pathogen in the USA from the Corynebacterium genus?
Definition
Corynebacterium jeikeium
Term
What are diphtheroids?
Definition
Any coryneform bacteria that isn't diphtheriae/ulcerans/JK
Term

What else does Corynebacterium diphtheriae cause other than diphtheria?

 

Definition
impetigo-like skin lesions that has little or no toxin effect; most common in tropics and among American Indians
Term
What is the pathogenesis of diphtheria?
Definition

It begins as a local infection of the throat

- bacteria carries a phage that encodes a protein exotoxin, which spreads systemically

one molecule of exotoxin can halt protein synthesis in an entire cell

Term
What are the two components of diphtheria exotoxin?
Definition

A: actively shuts off protein synthesis by binding to protein elongation factor 2

*can be recycled from ribosome to ribosome

 

B: binds to cell receptor and facilitates movement of the toxin into the cell

Term
What is the D in DPT vaccine?
Definition
formalin is added to diphtheria toxin to convert it into a "toxoid" which is antigenic but no longer toxic - this prevents disease but does not prevent the actual infection
Term
How long is the incubation period for diphtheria?
Definition
2-4 days
Term
What is the clinical presentation of diphtheria?
Definition
  • pharyngitis/tonsillitis: malaise, sore throat, fever
  • grey-white patch of exudate on tonsils, uvula, soft palate, or pharyngeal wall
  • cervical adenitis: neck edema
Term
What would the grey-white patch of exudate on the tonsils of a diphtheria patient be composed of?
Definition
coagulum of fibrin, leukocytes, and cellular debris
Term
What is a major clinical complication of diphtheria?
Definition
mechanical obstruction of airway if the membrane separates from the trachea
Term
What is the difference between the phage in Corynebacterium diphtheriae and Corynebacterium ulcerans?
Definition
Corynebacterium ulcerans produces smaller amount of diphtheria toxin (milder symptoms)
Term

What parts of the body does Corynebacterium ulcerans infect?

 

Definition
throat, pharynx, skin
Term
What is Corynebacterium jeikeium and what does it cause?
Definition

opportunistic pathogen that infects immunosuppressed patients in the hospital:

- bacteremia, catheter infetions, artificial heart valve infections, wound infections

Term
What is Corynebacteriumjeikeium resistant to?
Definition
ampicillin and cephalosporins
Term
What is the appearance of Listeria monocytogenes on a Gram stain?
Definition
Gram-positive rods resembling diphtheroids
Term
What does a colony of Listeria monocytogenes look like on a blood agar plate?
Definition

narrow zone of beta hemolysis

catalase positive

characteristic tumbling motility

Term
What are some reservoirs for Listeria monocytogenes?
Definition
soil, water, decaying vegetation, animals (esp. dairy), asymptomatic humans (5-10%)
Term
Where do Listeria monocytogenes grow and what three proteins does it use to move
Definition

In macrophages:

internalin for cell attachment

listeriolysin for movement within a cell

host actin for moving to new cells

Term
What are some clinical conditions associated with Listeria monocytogenes?
Definition
  • meningitis in immunocompromised patients
  • spontaneous abortion in pregnant females
  • bacteremia and meningitis in neonates
Term

Why is Listeria monocytogenes particularly good at causing food-borne outbreaks?

 

Definition
It survives and grows in the cold (4 degrees C) so it can contaminate dairy food
Term

How is Listeria monocytogenes diagnosed in the lab?

 

Definition

- Gram stain of the CSF (should see intracellular Gram-positive rods in macrophages and neutrophils)

- colonies look like beta-hemolytic strep, but:

  • are catalase-positive
  • sensitive to streptomycin
  • may have tumbling motility
Term
What is observable about the unusual motility of Listeria monocytogenes?
Definition

In motility agar stabs it forms an umbrella of turbidity

In broth it produces tumbling motility

Term
Where are erysipelothrix rhusiopathiae found?
Definition
in animals, meat, and seafood
Term
How can one get erysipeloid?
Definition

Following traumatic inoculation of the skin (associated w/ fishermen, butchers, and veterinarians)

 

Term
How is erysipeloid treated?
Definition
penicillin or erythromycin
Term
What are diagnostic characteristics of erysipelothrix rhusiopathiae?
Definition
  • positive for hydrogen sulfide
  • "test-tube brush" motility
Term
Which of the diphtheroids is anaerobic? (2)
Definition

Lactobacillus: aerotolerant

Propionibacterium: can't grow well aerobically

Term
What is the appearance of Lactobacillus acidophilus?
Definition

long, Gram-positive rods in chains

looks like viridans streptococci

Term
Where are Lactobacillus acidophilus considered a normal flora?
Definition
vagina, gut, and mouth
Term
How is Lactobacillus acidophilus associated with a healthy vagina?
Definition
Absence of Lactobacillus acidophilus allows the overgrowth of Gram-negative anaerobes, such as Gardnerella vaginalis, which is associated with vaginitis
Term
How is vaginitis diagnosed?
Definition
  • Gram stain of vaginal sample (count # of lactobacilli)
  • pH test of vaginal secretions (check for loss of acidity)
  • "Sniff" test of vaginal fluid: add KOH to release aromatic amines if present
  • NOT culture
Term
How is Propionibacterium an opportunistic pathogen?
Definition
It is a normal skin flora and common blood culture contaminant that can cause endocarditis, infected implants, wound infections, abscesses
Term
What other normal skin flora is Propionibacterium similar to in pathogenicity?
Definition
coagulase negative Staph (i.e. Staphylococcus epidermis)
Term
What are some characteristics of Bacillus species?
Definition
  • gram-positive rods
  • spore forming
  • grow best in air
  • catalase positive
  • motile
  • old cells may stain Gram-negative and mislead clinicians
Term
What do both Bacillus subtilis and bacillus cereus cause?
Definition
systemic infection w/ bacteremia, and wound infections in immunocompromised patients
Term
Which species, Bacillus subtilis and bacillus cereus, is responsible for food poisoning?
Definition
bacillus cereus
Term
What do Bacillus subtilis and bacillus cereus look like on blood agar plates?
Definition
greyish-white beta-hemolytic colonies
Term
What are two toxins produced by bacillus cereus?
Definition
enterotoxin and pyogenic toxin
Term
What are typical foods involved in bacillus cereus food poisoning?
Definition
"food warmer" foods (i.e. meats in gravy, fried rice)
Term
How are humans infected by Bacillus anthracis?
Definition
  • skin contact with infected articles
    • most common
  • breathing spores from wool/goat hair
    • most deadly
  • eating spores or infected meat
    • rare in humans, common in animals
Term
Where in the US and in what occupations is anthrax usually seen?
Definition
in the Southwest near Mexico
farmers, ranchers, butchers, vets, tapestry-weavers
Term
What are three anthrax virulence factors?
Definition
  • capsule is antiphagocytic
  • lethal exotoxin and edema exotoxin (protein-carbohydrate complexes)
Term
How are the anthrax exotoxins activated?
Definition
they need a protective antigen that binds and transports them into the host cell
Term
What is the clinical consequence of cutaneous anthrax infection?
Definition
half a day to 12 days after inoculation, an erythematous papule forms and grows until a black scab forms (complications include local edema, toxemia, bacteremia, death)
Term
What is the clinical consequence of gastrointestinal anthrax infection?
Definition

lesions at base of tongue or tonsils => sore throat, fever, regional lymphadenopathy

inflammation and lesions of intestines => nausea, vomiting, fever, pain, bloody vomit and diarrhea

Term
What is the clinical consequence of pulmonary anthrax infection?
Definition
initially: sore throat, mild fever, malaise, cough, muscle aches => then: difficulty breathing, shock, respiratory distress with cyanosis => massive edema of neck and chest
Term
How do inhaled anthrax spores multiply in the host
Definition
They reside for weeks in the alveolar recesses until taken up by macrophages, then germinate and replicate within the macrophages
Term
Why is it difficult to treat anthrax with antibiotic prophylaxis?
Definition
Inactive/latent spores are unaffected by antibiotics
Term
How are non-pathogenic Bacillus colonies (not anthracis) distinguished on agar plates?
Definition
dry, wrinkled, rarely mucoid, beta hemolytic
Term
When should culture for anthrax be done?
Definition
in clinically ill ppl with fever, myalgia, and other non-specific findings
Term
Which two places are inappropriate to obtain cultures from for anthrax detection/
Definition
sputum and nasal swabs
Supporting users have an ad free experience!