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BACT211 (LECTURE) > WEEK 14: GRAM POSITIVE RODS > Flashcards

WEEK 14: GRAM POSITIVE RODS Flashcards

1
Q

What are the tests used to differentiate Corynebacterium (-) to Listeria(+)?

A
  • Motility (22C)
  • Bile esculin Hydrolysis
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2
Q
  • Found as free-living saprophytes
  • Water, soil, air
  • Resistant to drying
  • 80 species, of which 50 are clinically significant
  • Members of the usual flora of humans and animals
  • Closely related to Mycobacteria and Nocardia
  • Clinically significant isolates
  • Catalase positive and nonmotile
A

Corynebacterium

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3
Q
  • Facultatively anaerobic
  • Gram-positive, non–spore-
    forming rods
  • Arranged in palisades
  • Club-shaped
  • Babes-Ernst granules
  • Polymerized phosphates
A

Corynebacterium

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3
Q
  • is the most significant pathogen.
  • Causes diphtheria
  • Difficult to speciate other species
  • Other species may cause infections in immunocompromised hosts.
  • Generally thought of as contaminants
A

Corynebacterium diphtheriae

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4
Q
  • Worldwide distribution
  • Rare in places where vaccination programs exist
  • Exotoxin is a major virulence factor.
  • Diphtheria toxin
  • Toxin is produced by certain strains.
  • Lysogenized by bacteriophage with toxin gene (tox+)
  • Only toxin-producing bacteria can cause diphtheria.
  • Toxin production is inversely proportional to iron availability.
  • Toxin is antigenic.
  • Thus can use immunoglobulin G (IgG) to block toxin effects
A

Toxigenic Corynebacterium diphtheriae

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5
Q

What is the major virulence factor of Corynebacterium diphtheriae?

A

Exotoxin

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6
Q
  • Inhibits protein synthesis
  • NAD+ + EF-2 → ADPR-EF-2 + Nicotinamide + H+
  • Catalyzes transfer of ADPR to link with EF2 ADPR.EF (inactive)
  • Leads to cell/tissue death
A

A: active fragment

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7
Q
  • Mediates entry of fragment A
  • binds to specific cell membrane receptors
A

Fragment B

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8
Q
  • Respiratory
  • Acquired by droplet spray
  • Aerosol or hand-to-mouth contact
  • Unimmunized individuals are susceptibleb
A

Clinical Infections of Diphtheria

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9
Q
  • More prevalent in the tropics
  • Infections occur at the site of minor abrasions.
  • Nonhealing ulcers with a dirty gray membrane
A

Cutaneous form of C. diphtheriae

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10
Q
  • Used to demonstrate
    pleomorphism and
    metachromatic granules
  • Babes-Ernst granules
A

Loeffler’s serum agar

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11
Q
  • Modified Tinsdale medium
  • Selective and differential
  • Black colonies with brown
    halos around the colonies
A

Cystine-tellurite blood
agar (CTBA)

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12
Q
  • Common on skin and most frequently recovered species
  • Opportunistic infections
  • Prosthetic joint infections, sepsis, and endocarditis
  • In nosocomial or immunocompromised patients
A

C. amycolatum

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13
Q
  • Mastitis in cattle
  • Contact with animals or unpasteurized milk
A

C. ulcerans

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14
Q
  • Infections from catheters or prosthetic devices
  • Prosthetic valve endocarditis
A

C. jeikeium

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15
Q
  • Urinary pathogen
  • Highly urease positive (within minutes)
A

C. urealyticum

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15
Q
  • Opportunistic infection
  • Often endocarditis
A

C. pseudodiphtheriticum

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16
Q
  • Contact with sheep
  • Dermonecrotic toxin
A

C. pseudotuberculosis

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17
Q
  • Rare infections
  • Normal flora
A

C. striatum

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18
Q

Gram-positive non–spore-forming coccobacillary

A

L. monocytogenes

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18
Q

Induces phagocytosis

A

Surface protein p60

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18
Q
  • Cold enrichment
  • Grows at 4°C
  • Catalase positive
  • Rules out Streptococcus
  • Negative for hippurate hydrolysis
  • Motility
  • Motile at 25°C
  • “Umbrella” type motility
  • Tumbling motility in hanging drop method
A

L. monocytogenes

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18
Q
  • Likely develop disease from penetration of the intestine
    and systemic spread
  • Septicemia/meningitis in the compromised/elderly
  • Also endocarditis
  • Mild flulike syndrome in pregnant women could be fatal to fetus
  • Premature labor, spontaneous abortion
A

Listeriosis

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19
Q
  • Gram-positive, nonsporulating forming rods
  • Coccobacillus that often appears like cocci
  • Widespread in nature
  • Primarily infect animals
  • Human exposure is limited.
  • Generally dairy products because it grows at low temperature
  • Processed meats can also contain this bacteria
A

Listeria monocytogenes

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19
Q
  • Normal oral flora
  • Endocarditis
A

Rothia dentocariosa

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19
Q
  • Damages phagocytic membrane and prevents killing of the organism
A

Listeriolysin O

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20
Q
  • Grows well on sheep blood agar (SBA) and chocolate
    agar
  • Prefers slightly increased carbon dioxide (CO2)
  • Colonies produce a narrow zone of hemolysis.
  • Similar to group B Streptococcus
A

L. monocytogenes

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21
Q

Produces a “block” type of hemolysis in contrast to “arrow” shape produced by group B Streptococcus

A

Christie Atkins Munch-Petersen (CAMP) test (L. monocytogenes)

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22
Q
  • Gram positive, non–spore-forming, pleomorphic
    rods
  • Distributed in nature
  • Can cause disease in animals (swine, turkey, sheep)
  • Infection through occupational exposure
  • Erysipeloid
  • Heals within 3 to 4 weeks
  • Endocarditis
A

Erysipelothrix rhusiopathiae

23
Q
  • CO2 is required.
  • Grows on blood or chocolate agar
  • Colonies may appear gray or translucent with alpha hemolysis.
  • Pleomorphic, gram-positive thin rods that may form long filaments
  • Singly, in short chains, or in a V shape
  • Catalase negative
  • Production of hydrogen sulfide (H2S) on triple sugar iron (TSI)
A

Erysipelothrix rhusiopathiae

24
Q
  • SBA or chocolate agar
  • 5% to 7% CO2 at 35°to 37°C
  • Human blood bilayer Tween (HBT) agar
  • Medium of choice
  • Treatment
  • Metronidazole
  • Clindamycin
A

Gardnerella vaginalis

24
Q
  • Pharyngitis and pruritic scarlatiniform rash with desquamation of the skin of the hands and feet
  • Lipase and lecithinase positive
  • Exhibits a CAMP inhibition reaction
A

Arcanobacterium haemolyticum

24
Q

Sepsis and wound infections in those with animal contact

A

A. pyogenes

24
Q
  • Catalase negative
  • Narrow zone β-hemolysis
  • Black dot on agar surface under the colony
A

Arcanobacterium

24
Q
  • Short, pleomorphic gram-positive rod or coccobacillus
  • Often stains gram-variable or gram-negative
  • Infections
  • Bacterial vaginosis (BV)
  • Malodorous discharge
  • Vaginal pH of greater than 4.5
  • Wet mounts of vaginal fluid
  • Observe clue cells
A

Gardnerella vaginalis

25
Q

Bacteriemia, wound infections, urinary tract infections (UTIs), and septic arthritis

A

A. bernardiae

25
Q
  • Aerobic
  • Gram-positive filamentous rods
  • Weakly acid-fast and may stain gram-variable
  • Sometimes resembling branched hyphae
  • Morphologically resemble fungi
  • In culture and in types of infections
  • Generally found in the environment and mostly affect
    immunocompromised individuals
     Sulfur granules
A

Nocardia

26
Q
  • Slow growers, may take 3 to 6 days
  • Primarily affect immunocompromised
  • Rare but high mortality rate (40%)
  • Gram-positive branching filaments are seen in direct smears from
    sputum or aspirated material.
  • May show beading appearance
A

Nocardia

26
Q
  • Confluent bronchopneumonia
  • Necrosis with abscesses
  • No “sulfur granules”
A

N. cyriacigeorgica and N. farcinica

27
Q
  • Cutaneous infection termed actinomycotic mycetomas
  • Trauma to skin
  • Major destruction of the tissue and bone
  • “Sulfur granules” present
A

N. brasiliensis

28
Q
  • Large, square-ended
    gram-positive rods
  • Bamboo appearance
  • Nonhemolytic on 5%
    blood agar; raised,
    large, grayish-white,
    irregular, fingerlike
    edges
  • “Medusa head” or
    “beaten egg whites”
A

Bacillus anthracis

28
Q

Nocardia can be identified using?

A

paraffin bait test

28
Q
  • Agent of anthrax, a disease in livestock
  • Humans acquire infection by contamination of wound or
    ingestion or inhalation of spores.
  • Morphology
  • Large, spore-forming, gram-positive bacilli
  • Spores viable for over 50 years (even restored from fossils)
  • Nonhemolytic on SBA
A

Bacillus anthracis

28
Q
  • Found in nature
  • Most are saprophytic and are isolated as contaminants
  • Gram-positive large rods with “empty” spaces
  • Endospores
  • Highly resistant to heat, drying, and chemicals
  • Catalase positive
A

Bacillus

29
Q
  • Acquired through inhalation of spores
  • Mild fever, fatigue, and malaise 2 to 5 days after exposure
  • Similar to flu or common cold, lasting 2 to 3 days
  • Sudden respiratory distress, disorientation, coma, and
    death
  • May last less than 24 hours from onset to death
A

Pulmonary anthrax or “woolsorter’s disease”

29
Q
  • Polypeptide capsule
  • Potent exotoxin
  • Edema factor (EF)
  • Protective antigen (PA)
  • Lethal factor (LF)
A

Virulence factors of Bacillus anthracis

29
Q
  • Acquired by ingestion of contaminated raw meat
  • Inoculates into a lesion on the intestinal mucosa
  • Abdominal pain, nausea, anorexia, vomiting, and
    sometimes bloody diarrhea
  • More likely to be fatal but less likely to occur than
    cutaneous form
A

Gastrointestinal anthrax

30
Q
  • Enter through cuts causing a localized infection
  • Malignant pustule or black eschar
  • Painless and non–pus-producing
  • Produces a permanent scar
A

cutaneous anthrax

31
Q
  • Acquired by direct injection of the endospores into tissue
  • Injection drug use
  • Does not form black eschar
  • Causes necrotizing fasciitis, organ failure, shock, coma, and meningitis
A

Injectional anthrax

31
Q
  • Caused by distinct enterotoxins
  • Diarrheal syndrome
  • Associated with meat, poultry, and soups
  • Incubation period of 8 to 16 hours
  • Fever uncommon
  • Resolves within 24 hours
  • Emetic form
  • Associated with fried rice
  • Abdominal cramps and vomiting
  • Incubation period of 1 to 5 hours
  • Resolves in 9 hours
A

B. cereus

31
Q
  • Infections in the immunosuppressed hosts
  • Opportunistic infections of the eye
  • Endophthalmitis, panophthalmitis, and keratitis
  • Forms abscesses
  • Meningitis, septicemia, and osteomyelitis
A

B. cereus

32
Q
  • Boxcar-shaped, gram-negative bacillus
  • Produces a double zone of hemolysis on Brucella blood agar or blood agar
A

Clostridium perfringens

32
Q

Antibiotic-associated diarrhea and pseudomembranous colitis

A

Clostridium difficile

33
Q

Heavily swarming with terminal spores

A

C. tetani

33
Q

Heavily swarming with subterminal spores

A

C. septicum

34
Q
  • Enteritis necroticans
  • Acute onset of severe abdominal pain and diarrhea, which is often bloody, and may be accompanied by vomiting
  • Followed by necrotic inflammation of the small intestines, at times
    leading to bowel perforation
  • Without treatment it can be fatal
A

Type C Clostridium perfringens

34
Q
  • A through G, but only types A, B, and E are associated with human disease
  • Toxin A is now used in medical treatments, including Botox®
A

Botulinum toxins

35
Q
  • Causes flaccid paralysis
  • In contrast to tetanus
A

Clostridium botulinum

35
Q
  • Ingestion of enterotoxin causing diarrhea and cramps
  • Usually self-resolving
A

Type A Clostridium perfringens

36
Q
  • Home canning
  • Home-cured meats
  • 2 hours to 8 days later
  • Infant botulism
  • Ingestion of spores in contaminated honey
  • Colonize the colon and produce toxins
A

Botulism

36
Q
  • Also known as gas gangrene
  • Contaminated wounds from trauma or surgery
A

Myonecrosis

36
Q
  • Develops from tetanospasmin neurotoxin
  • Inhibits neurons by inhibiting neurotransmitters
  • Symptoms:
  • Begin about 7 days after inoculation
  • Muscular rigidity of the jaw, neck, and lumbar region
  • Difficulty in swallowing
  • Sometimes involves limbs as well
A

Tetanus

36
Q

most common cause of Myonecrosis

A

C. perfringens

37
Q

Most common isolate from blood cultures

A

C. perfringens

37
Q
  • Grow, multiply, and produce toxin
  • Alpha toxin causes tissue necrosis and deeper invasion
  • Causes death of tissue that can require amputation
  • Symptoms
  • Pain and swelling with obvious tissue necrosis
  • Treatment
  • Antibiotic and surgical débridement of necrotic tissue
  • Hyperbaric oxygen can help destroy anaerobes
A

Myonecrosis

38
Q

Marker organism for malignancy of GI tract

A

C. septicum

39
Q

Both isolated from patients with underlying disease

A

C. tertium

40
Q
  • Most common isolate in antibiotic-associated diarrhea
  • Can cause pseudomembranous colitis
  • Necrosis of colon tissue and bloody diarrhea
A

C. difficile

41
Q
  • Commonly transmitted as a nosocomial infection
  • Transferred among patients
  • Hands of hospital personnel
A

Antibiotic-Associated Diarrhea

42
Q

Chronic, granulomatous disease characterized by sinus tracts and fistulae
that erupt to the surface and drain pus that contains “sulfur granules”

A

Actinomycosis

BACT211 (LECTURE) (18 decks)

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