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► Med - Pathology > Gram Positive Rods > Flashcards

Gram Positive Rods Flashcards

1
Q

What are the characteristics of Bacillus?

A
  • Spore forming Gram positive rod
  • Widespread in nature
  • Prefers aerobic conditions
  • Motile except for B. anthracis
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2
Q

What disease does Bacillus anthracis cause?

A

Anthrax

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3
Q

What are Biothreat Category A pathogens?

A

Category A pathogens are those organisms/biological agents that pose highest risk to national security and public health because they:
– Can be easily disseminated or transmitted from person to person
– Result in high mortality rates and have potential for major public health impact
– Might cause public panic and social disruption

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4
Q

What are the 3 types of anthrax infections found in humans?

A
  • Cutaneous
  • Gatrointestinal
  • Inhalation
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5
Q

What are the characteristics of cutaneous anthrax?

A 
– Painless papule
– Ulcer surrounded by
vesicles
– Necrotic eschar
– 20% mortality
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6
Q

What are the characteristics of GI anthrax?

A 
• Upper GI
– Ulcers in mouth and esophagus
• Lower GI
– Terminal ileum most common – N/V, malaise, bloody diarrhea
• Mortality 100%
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7
Q

What are the characteristics of inhalation anthrax?

A

• Prolonged latent period (2 months or more)
– Fever, SOB, cough, HA, vomiting, chills, chest and abdominal pain
• Second stage
– Rapidly worsening fever, edema and enlargement of
mediastinal lymph modes

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8
Q

What is seen on the x-ray of inhalation anthrax patients?

A

Widened mediastinal area

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9
Q

What are the virulence factors of B. anthracis that lead to pathogenesis?

A
  • Edema toxin: fluid accumulation

* Lethal toxin: stimulates macrophages to release tumor necrosis factor and interleukin 1 beta

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10
Q

What biochemical test results can confirm anthrax?

A

– Motility - negative
– Non-Hemolytic
– PCN susceptible

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11
Q

What does Bacillus cereus infection cause?

A

Mainly food poisoning
– Caused by exotoxins
– Emetic form
– Diarrheal form

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12
Q

What are the Gram positive rods that can cause food poisoning?

A

Bacillus cereus

Clostridium perfringens

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13
Q

What is a possible unique habitat for Listeria monocytogenes?

A

Refrigerated food

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14
Q

What is the mechanism of infection of Listeria?

A
  • Bacteria invade epithelial cells, M cells, macrophages by internalin protein
  • ActA protein allows them to move into adjacent cells without exposure to immune system
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15
Q

Why are patients with defects in cellular immunity especially susceptible to Listeria?

A

Humoral immunity relatively unimportant because bacteria move within cells, thus avoiding antibody-mediated clearance

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16
Q

What are the 3 populations that are at the largest risk for Listeria infection?

A
  • Neonates
  • Pregnant women
  • Elderly
17
Q

What bacteria has umbrella motility?

A

Listeria

18
Q

What are the laboratory characteristics of L. monocytogenes?

A

– Catalase +
– Tumbling motility
– Motile at RT

19
Q

What is a fruit that is at high risk for Listeria?

A

Cantaloupe

20
Q

What are the characteristics of Erysipelothrix rhusiopathiae?

A

Catalase negative
Non-motile
Weakly fermentative
Produces H2S on triple sugar iron agar (TSI)

21
Q

What populations are at main risk of Erysipelothrix rhusiopathiae infection?

A

Butchers, meat processors, farmers, poultry workers, fish handlers and veterinarians

22
Q

What are the 2 types of E. rhusiopathiae infection?

A

– Erysipeloid: localized skin infection, on fingers or
hands and appears violaceous with a raised edge.

– Septicemic form: uncommon, when present frequently associated with endocarditis

23
Q

What are the characteristics of Corynebacterium?

A
  • Pleomorphic Gram positive rods
  • Clumps of organisms resembling Chinese “letters”
  • Grows aerobic or facultatively anaerobic
24
Q

What is the pathogenesis of C. diphtheriae?

A

Disease caused by potent exotoxin&raquo_space; inhibits protein synthesis of eukaryotic cells

25
Q

What is the origin of the diphtheria toxin?

A

Bacteriophages

26
Q

What are clinical manifestations of C. diphtheriae infection?

A
  • Pharyngitis with patchy exudates on tonsils, uvula, soft palate
  • Tough gray pseudomembrane consists of fibrin, white cells, bacteria, debris&raquo_space; respiratory obstruction and suffocation
27
Q

Who is at most risk to contract C. jeikeium?

A

• Infects immunocompromised patients

28
Q

What is used to treat C. jeikeium?

A

Organisms are resistant to most antibiotics, except vancomycin

29
Q

Arcanobacterium hemolyticum characteristics

A

Beta hemolytic
Forms a “V” formation
Chinese character morphology
Mostly found on young adults

30
Q

Lactobacillus characteristics

A
  • Normal flora of oral cavity, vaginal tract
  • Found in food products (yogurt)
  • Prefers carbon dioxide or anaerobic atmosphere
31
Q

Nocardia characteristics

A

Gram-positive
Partially acid-fast rods
Cell wall with mycolic acid
Strict aerobe, will grow on most agars but takes a long time

32
Q

Nocardia reservoir

A

Found worldwide in the soil

33
Q

Who is Nocardia infection most often seen in?

A

Disease most common in immunocompetent pts. with chronic pulmonary disease or immunocompromised pts. with T-cell deficiencies

34
Q

Why is Nocardia not seen in HIV patients?

A

Not seen in AIDs due to treatment with sulfonamides

so they are treated prophylactically and it hits nocardia too

35
Q

A 22 year old medical student presents with symptoms of pharyngitis with a fever, and cutaneous rash. A throat culture reveals small beta hemolytic colonies that are catalase-negative and stain as short Gram- positive rods exhibiting Chinese character morphology. What is the most likely agent of this students pharyngitis?

A. Arcanobacterium hemolyticum 
B. Corynebacterium diphtheriae 
C. Erysipelothrix rhusiopathiae 
D. Listeria monocytogenes
E. Streptococcus pyogenes
A

A. Arcanobacterium hemolyticum

36
Q

What is the most common disease associated with Nocardia?

A

Pulmonary Disease

37
Q

What is the most common disease associated with Rhodococcus?

A

Pulmonary Disease

38
Q

What is the most common disease associated with Tropheryma?

A

Whipple’s Disease

► Med - Pathology (203 decks)

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