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S1B5: Micro > Gram Positive Rods > Flashcards

Gram Positive Rods Flashcards

1
Q

How could you identiy a culture of Bacillus anthracis?

mobility?

hemolysis?

growth requirement?

Spore formation?

Capsule?

A
  • Gram positive rods
  • non-motlie
  • gamma- hemolytic (medusa-head colonies)– strongly adherent
  • non-fastidious large
  • form spores 2-3 in culture, not in clinical situation
  • Bicarbonate Agar is used to induce capsule production
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2
Q

What is the source of B. anthracis infection?

What are the primary virulence factors?

A

primary a disease of grazing herbivores– infection by contact with infected animals/products (human to human transmission is not documented)

2 large plasmids accound to all the birulence– produce binary exotoxins pXO2 (protective toxin, lethal toxin, edema toxin) and pXO1

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3
Q

Explain the virulence process of B. anthracis

A
  • PA binds to the ANTXR receptor, and a piece is cleaved off
  • then the process PA oligomarizes and form a receptor
  • LF and EF can bind with equal affinity,
  • once they are both bound, they are internalized
  • then there is acidification of this endosome, the LF, and EF are sent to cytoplasm
  • EF raises cAMP (the cell swells)
  • LF degrades MAPKK, cell will die
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4
Q

What disease is shown in the image provided?

Characterized by vesicles with no puss, necrosis, eschar formation and edema (may be massive), painful lymphadenopathy; hematogenous spread with resultant toxemia can occur

What bacteria is responsible for this disease?

A

Cutaneous anthrax

B. anthracis

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5
Q

What disease is charactered by the following symptoms and images?

begins with viral infection URT (fever, cough, myalgia)

septic shock and toxemia

hemorrhagic meningitis and lung compression

Respiratory distress due to blocked lymphatic drainage leading to pulmonary edema

What is the likely bacterial cause?

A

Inhalation anthrax (Woolsorter’s disease)

B. anthracis

Will see widening of mediastium (see in x-ray) and hemorrhagic meningitis

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6
Q

What disease is characterized by the following symptoms?

Oropharyngeal and or abdominal mucosal ulcer followed by lymphadenopathy and edema

acute inflammation, severe GI difficulty, bloody vomit/diarrhea

What is the likely bacterial cause?

A

Intestinal anthrax

B. antracis

Hematogenous spread & toxemia can occur, rare, but 100% lethal

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7
Q

Where would you obtain a culture of B. antracis from the following diseases? What other steps should be taken?

  1. Cutaneous
  2. Gastrointestinal
  3. Inhalation
A
  1. Cutaneous
    1. vesicular stage (vesicular fluid) or eschar material
  2. gastrointestinal
    1. blood, stool, rectal swab
  3. inhalation
    1. blood, sputum, stool

Quick EIA for protective antigen or PCR for bacterial presence

Contact state public health lab if suspected

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8
Q

How could you identify a cuture of Bacillus cereus?

growth requirement?

oxygen requirement?

gram staining?

hemolysis?

capsule?

motility?

lysis by gamma phage?

Where are they found?

A
  • non-fastidious
  • facultative
  • large gram positive rods
  • beta-hemolytic
  • no capsule
  • motility (+)
  • no lysis by gamma phage

Found

  • Cells/spores- everywhere in the environment
  • acquied from contaminated food (dairy, bakery, meat, rice, etc.)
  • may be acquired fro penetrating injuries (eg. to eye)
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9
Q

What are the two types of virulent toxins produced by B. cereus?

A
  • 1 emetic toxin (ETE) = emetic disease
    • heat stable
    • within an hour
  • 3 enterotoxins (HBL, Nhe, EntK) = diarrheal disease
    • heat sensitive (spores still there)
    • slow onset
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10
Q

What genus includes all gram positive anaerobic spore formers?

Where do they naturally colonize?

A

Clostridium

Part of the colonic normal flora

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11
Q

How many toxins are produced by C. perfringens?

Why are they not produced all the time?

A

12 different toxins, but does not produces them during normal growth b/c require specific signals

The signals come from necrotic tissues

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12
Q

What disease is common after surgery/trauma?

The damage to the arties allows for anaerobic conditions

does not involve the muscle

What bacteria is likely the cause of this disease?

A

Clostridial Cellulitis

C. perfringens

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13
Q

What disease is characterized by the following symptoms?

What bacteria is the likely cause of this disease?

Common in agricultural regions, frequently associated with gun-shots and deep knife wounds

very fast progression

sudden onset excruciating pain and gas bubbles

fast developing, foul smelling wound, crepitus also present

Extensive hemolysis, shock, renal failure

A

bacteria present in infected tissues; inflammatory cells-absent

Clostridial Myonecrosis (Gas Gangrene)

C. perfringens

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14
Q

What disease is characterize by diarrhea in 8-22 hrs after eating slow cooling or insufficintly reheated food?

A

Food poinsoning from C. perfringens

happens when large number of bugs are ingested

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15
Q

What disease is characterized by necrotic destruction of jejunum and or ileum particulary after eating sweet potaotes?

Peritonitis, abdominal pain, bloody diarrhea, shock

What bacteria is the likely cause?

A

Necrotizing enteritis (ileum) & enteritis necroticans (jejunum)

Sweet potatoes conatins trypsin inhibitor

C. perfringens (produced by strains producing alpha and beta toxins)

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16
Q

How could you identify a culture of C. perfringens?

motility?

gram staining?

other cells present in sample?

naglar test?

A
  • non-motile
  • box-car gram positive rod
  • no leukocytes in clinical sample (good indicator)
  • positive naglar reaction

b/c they are native to GI, may find some in a blood sample, so be careful to correlate lab measures with symptoms to confirm diagnosis

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17
Q

Explain the virulence of C. tetani

A

tetanospasmin (tetanus toxin)

  • plasmid encoded, responsible for tetnus symptoms
  • blocks release of GABA and glycine (inhibits inhibitory neurons)
  • GABA inhibits motor neurons and causes muscle spasms
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18
Q

What disease is characted by the following symptoms

excessive crying, trismus, tetanic spasms, opisthotonus in infants

What bacteria is responsible for the infection?

What is often the cause of the disease?

A

Neonatal tetanus (tetnus neonatorum)

C. tetani

Mostly in developing countries; infection usually through umbilical stumb; dirty tools to sever cord & cloths, soil or dung to stump

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19
Q

How would you identify a culture of C. tetani?

gram staining?

Spore shape?

A
  • Clinical presentation and presence of wound
  • anaerobic gram (+) rod
  • round terminal spores (“tennis raquet”)
20
Q

Which botulinum toxin is the predominant cause of human disease? What is the mechanism of this toxin?

Where are spores found?

A

A

Toxin prevents Ach rrelease at peripheral cholinergic receptors, results in flaccid paralysis

Spores found in soil worldwide

21
Q

What are the differences between a botulinum toxin infection and a tetanus toxin infection?

A
22
Q

Describe the disease characterized by the following symptoms:

blurred vision, constipation, abdominal pain, symmetric descending paralysis

patient ate canned food

A

Foodborne botulism

C. botulinum

Death from respiratory paralysis (10%)

23
Q

Describe the disease characterized by the following symptoms:

infants, constipation, weak cry

flaccid paralysis, respiratory arrest possible

consumption of honey

A

Intestinal botulism

C. botulinum

24
Q

Describe the disease characterized by the following symptoms:

flaccid paralysis and prominent bulbar palsies, outbreak with no common source except geographic factor

A

Inhalation botulism

C. botulinum

Class A terrorism concern

25
Q

How could you identify a culture of Clostridiodes difficle (C. diff)?

gram staining?

oxygen requirement?

A
  • >3 unformed stolls per 24 hrs for > 2 days wiht no other recognized cause
    • toxin A & B detected in stool
    • pseudoomembran colonoscopy & PCR for presence toxin genes
  • gram positive spore formign rod
  • strick anaerobe
26
Q

When is disease caused by C. diff most common?

A

after antibiotic use (b/c very resistant)

very common in hospitals/nursing homes b/c transfer from spores on hand of hospital personnel

27
Q

What are the two majore virulence toxins produced by C. diff?

A

spores survive gastric pH, germinate adn colonize GIT

  • Toxin A (enterotoxin) & toxin B (cytotoxin)
    • disrupt epithelial cells & cytoskeletan = diarrhea
    • Toxin A also kills cells in bowel wall
      • ulcer, necrosis, pseudomembrane
28
Q

What are the 3 important steps for C. difficle colitis?

A
  1. exposure to antibiotics
  2. exposure to C. difficile capable of producing the toxins
  3. inadequate immune response (antibodies to toxin A is protective)
29
Q

What mild diseases are caused by C. difficle?

A

diarrhea, abdominal cramp, mild fever

30
Q

What disease is characterized by the following symptoms?

1-2 mm white yelllow plaques in colonic mucosa

may cover the entire colon surface

infants not usually susceptable

What bacteria is responsible and how would you treat?

A

Pseudomembranous (PSM) colitis

C. diff

rePOOPulate (infusion of fecal content from healthy donor is an effective treatment)

31
Q

How could you identify a culture of Listeria monocytogenes?

gram stain?

catalse?

CAMP?

Where do cultures naturally grow?

A
  • small, gram (+) coccobacilli in pairs
  • catalase positive
  • Positive CAMP test
  • can grow in the refrigerator (4 degrees C)
    • uncommon but significant foodborne mortality in US
    • unusual person-to-person transmission except in hospitals
  • ubiquitous saprophyte - humans only accidental
    • can cross placental barrier
32
Q

Describe the virulence of L. monocytogenes. What is the virulence transcriptional regulator?

motility?

adherence?

proteins?

toxin?

A

Can withstand protesases, acid and bile to reach GIT

saprophyte to pathogen regulated by transcriptional regulator PrfA

  • motility
    • flagella-mediated:
      • only RT (virulence) – helps scientists identify
    • Actin-mediated: helps bacterial spread in the host
  • Adherence:
    • bacterial alpha-D-galactose binds E-cadherin of intestinal cells
  • Internalin (InIA, InIB, & InIC)
    • promotes endocytosis even by non-phagocytic cells
    • Helps Listeria cross BBB and feto-placental
  • Listeriolysin (LLO)– cholesterol dependent
    • helps rupture the endosome, releases Listeria in the cytosol
    • LLO helps translocation of 2 listerial phospholipases (contribute to lysis of endosomes)
33
Q

Life cycle of L. monocytogenes?

A
  • Listerial ActA helps actin nucleation to build a tail
    • tails propel Listeria intra- and inter-cellularly
    • stays mostly inside the cell, thus immunity is cell mediated
      • antibodies play no role
34
Q

What disease is characterize by the following symptoms?

Food poisoning ~48 hrs after eating a meal, resulting in 2-3 days of watery diarrhea, fever, nausea, headache in healthy adults

What is the bacterial cause?

A

Gastroenteritis

L. monocytogenes

35
Q

What can happen if a fetus is infected by L. monocytogenes?

At or shortly after birth?

A

50% mortality rate

abortion, still birth, or premature death

graulomatoisis infantseptica

Late: meningoencephalitis

36
Q

How could you identify Erysipelothrix rhusiopathiae?

gram stain?

growth?

A
  • pleomorphic, gram (+) rod
  • slow growing, non-fastidious
    • incubate plate for a week before considering negative
  • acquired through scratches/puncture wounds (veterinary pathogen)
  • need to biopsy deep tissue
37
Q

What disease is characterized by the following symptoms?

localized cutaneous lesion 1-7 days after inoculatio into skin

painful and pruitic, ususally self-limited

lack of supuration

What bacteria is responsible for this disease?

A

erysipeloid

E. husiopathiae?

lack of supuration distinguishes it form erysipelas

38
Q

How can you identify a culture of Corynebacterium?

gram stain?

Where does it colonize?

A
  • gram positive coryne “club”
  • short mycolic acids
  • Colonization
    • skin and URT
39
Q

Describe the virulence of C. diphtheriae

A

encoded by bacteriophage tox gene– iron dependent production

Production is inhibited by Fe-DtxR (high iron levels)

When iron levels are low, (like in the human body), inhibitor leaves, alowing transcription diptheria toxin

Dipteria toxin inhibits protein synthesis – leads to “pseudomembrane”; toxicity is prominent in heart and kidney

40
Q

Identify the disease characterized by the following symptoms

initially sore throat, fever, and weakness

neck edema & difficulty breathing

mucosal ulcer maybe seen wiht pseudomembrane (causes bleeding when removed); may extend from pharynx to bronchial airways

A

Nasopharyngeal diphtheria

C. diphtheriae

Expanding & sloughing may lead to fatal airway obstruction

41
Q

Identify the disease characterized by the following symptoms:

initially sore throat, fever, and weakness

punched-out ulcerative lesions with necrotic sloghing or pseudmembrane

What is the likely bacterial cause?

A

Cutaneous diptheria

C. diptheriae

poses greater risk of transmission

42
Q

What is the cause of septicemic diptheria?

A

Toxin reaches distant organs via circulation

toxin can cause fatal heart failure and polyneuritis

*due to toxin spread, not bacterial spread

43
Q

How could you identify a culture of C. diptheriae?

Growth on blood agar/ blood tellurite?

Specific growth medium?

A
  • White colonies on blood again; black colonies on blood tellurite agar
  • Loeffler medium
44
Q

How could you identify a culture of Corynebacterium minutissimum?

gram stain?

growth conditions?

typical colony location?

A
  • gram-positive rod
  • grows well in humid conditions
  • infects inter-triginous regions (axilla, anogenital); upper 1/3 stratum corneum
45
Q

Wha disease is charcterized by the following symptoms:

dark skin discoloration

A

Erythrasma

C. minutissiumum

46
Q

How could you identify a culture of Cutibacterium acnes?

gram stain?

oxygen needs?

natural colony location?

A
  • gram-positive anaerobic rod
  • common resident in pilosebaceous glands
    • acne during puberty
47
Q

What diesease is characteized by the following symptoms?

localized inflammatory response in hair follicles; can also cause abseces in the mouth and tear ducts

A

acne vulgaris

canaliculitis = inflammation tear duct

enzymes stimulate local inflammatory response; attracts PMNs

S1B5: Micro (12 decks)

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