M7 UCMS Flashcards
What organisms are in the HACEK group?
- Haemophilus aphrophilus (now Aggregatibacter aphrophilus)
- Actinobacillus (now Aggregatibacter actinomycetemcomitans)
- Cardiobacterium spp. (hominis)
- Eikenella spp. (corrodens)
- Kingella spp. (denitrificans and kingae species)
What are the common characteristics of the organisms in the HACEK group and what can they all cause?
The HACEK group are: 1. Fastidious 2. Slow growers, 48 hrs 3. gram-neg-bacilli Cause slowly progressive endocarditis.
What is the colonial morphology of Aggregatibacter aphrophilus and what mediums can it grow on?
Aggregatibacter aphrophilus colony morphology:
Round, convex with opaque zone near center.
Requires chocolate agar from growth (increased CO2) but can grow on Blood agar.
What tests can be done to I.D. Aggregatibacter aphrophilus after the colony morphology?
Aggregatibacter aphrophilus I.D. Tests:
- X and V factor negative (doesn’t need either to grow)
- Catalase negative.
- Lactose fermenters.
What does the gram stain of Aggregatibacter actinomycetemcomitans look like?
Aggregatibacter actinomycetemcomitans gram stain:
Very short gram-neg bacilli singly, in pairs and in chains like dots and dashes of Morse code.
What kind of reservoir in humans does Aggregatibacter actinomycetemcomitans tend to colonate in and common infections this organism is seen in?
Aggregatibacter actinomycetemcomitans:
Reservoir in mucous membranes of respiratory tract.
Seen in endocarditis and periodontitis infections.
Note: Resistant to penicillin.
What tests can be used to I.D. Cardiobacterium spp. (hominis)?
Cardiobacterium spp. I.D. tests:
- Gram stain: Gram-neg rods w/ one rounded end and one tapered end (teardrop), forming clusters/rosettes.
- Oxidase positive and
- Indole positive
- Catalase neg.
What type of specimens is used to take back to the lab for analysis for Cardiobacterium spp.?
Specimens for Cardiobacterium spp.:
Blood specimens, corneal scrapings, and periodontal specimens best for recover of organism.
Besides endocarditis and periodontitis, what other infections can be seen with Eikenella spp. and why?
Eikenella spp. can also cause:
Extra-oral infections related to human bites and clenched-fist wounds. That is because it is normal human flora in the oral cavity.
Occurs more in immunosuppressed.
What I.D. tests can be performed on Eikenella spp.?
Eikenella spp. I.D. tests:
- Gram stain: med-length, gram-neg straight rod, round ends.
- Colony morph: gray & may have a corrode or pit in agar. Chlorine bleach smell is characteristic! Small at 48 hrs.
- Oxidase +
- Nitrate reductase +
- Catalase -
- Beta lactamase testing is recommended, no routine AST.
What tests can be performed to I.D. Kingella spp. (denitrificans and kingae species)?
Kingella spp. I.D. Tests:
- Gram stain: Gram-neg short, plump cocobacilli with squared off ends that may form many chains. May appear gram variable.
- Oxidase +
- Catalase, Nitrate and indole - (Neg)
- Susceptible to beta-lactamase antibiotics.
What does the colonies for Kingella spp. look like and what atmosphere do they like?
Kingella spp. colonial morphology:
- Smooth, convex, tan to yellow colonies, sometimes pit agar.
- Grows on BA, CA and TM. (Might be confused with Neisseria to catalase and nitrate tests help.)
- They like CO2 for growth.
What organism causes relapsing fever and Lyme disease in humans? What does it take to get infected?
Borrelia spp.
- One bite from tick or Borrelia spirochete getting into host skin are examples of getting infected.
- Feed on hosts blood or spirochetes release into blood causes infection.
What is the name of the particular Borrelia spp. species that causes Lyme disease? What is the vector?
B. burgdorferri causes Lyme disease
Vector: Tick, common species Ixodes dammini
What is the Borrelia spp. that causes relapse fever?
B. recurrentis, transferred by body louse infected with spirochete.
