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Bacte - Reviewer > Gram Positive Bacilli > Flashcards

Gram Positive Bacilli Flashcards

1
Q

Medically Important Gram-Positive Bacilli
Three general groups

A

Endospore-formers
Non-endospore-formers
Irregular shaped and staining properties

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2
Q

Endospore-formers

A

Bacillus, Clostridium

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3
Q

Non-endospore-formers - Regular shaped

A

Listeria, Erysipelothrix

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4
Q

Non-endospore-formers
Irregular shaped and staining properties
Non-Acid Fast

A

Corynebacterium, Proprionibacterium

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5
Q

Non-endospore-formers
Irregular shaped and staining properties
Acid Fast

A

Mycobacterium

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6
Q

Non-endospore-formers
Irregular shaped and staining properties
Filamentous, branching cells

A

Actinomyces, Nocardia

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7
Q

Found in nature
Most are saprophytic and are isolated as contaminants
Bacillus anthracis as a major pathogen
Others are opportunists

A

Bacillus species

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8
Q

Spore-forming Bacilli

A

Genus Bacillus
Genus Clostridium

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9
Q

Gram-positive, endospore-forming
Mostly saprobic
Aerobic/ facultative and catalase positive
Often β hemolytic & motile
(except B. anthracis)
Versatile in degrading complex macromolecules
Source of antibiotics
Primary habitat is soil

A

Genus Bacillus

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10
Q

Thick walled structures formed by vegetative cells
Resistant to radiation, chemicals, heat, desiccation (dipicolinic acid)
Steam autoclaving necessary for destruction

A

Bacillus Endospores

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11
Q

Enzootic in middle east
Transmitted by contact with animal products
Spores remain infectious for years
Usually cutaneous inoculation - slow healing ulcer, bacilli spread to lymphatics and bloodstream
20% mortality if untreated
Respiratory anthrax is usually fatal even if treated
GI anthrax also occurs in some Asian countries
Excellent biological warfare agent

A

Bacillus anthracis

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12
Q

Large, block-shaped rods
Central spores that develop under all conditions except in the living body

A

Bacillus anthracis

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13
Q

Virulence factors of Bacillus anthracis

A

Polypeptide capsule & exotoxins

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14
Q

3 types of anthrax

A

cutaneous
pulmonary
gastrointestinal

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15
Q

the organisms gain access through cuts; localized infection

A

Cutaneous anthrax or “malignant pustule”:

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16
Q

acquired through inhalation of spores; may result in respiratory distress and death

A

Pulmonary anthrax or “woolsorter’s disease”

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17
Q

:acquired by ingestion of contaminated raw meat

A

Gastrointestinal anthrax

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18
Q

Gram stain: large, square-ended gram-positive rods; may appear end-to-end giving a “bamboo appearance”

A

Microscopic morphology of Bacillus anthracis

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19
Q

Nonhemolytic on 5% blood agar; raised, large, grayish-white, irregular, fingerlike edges described as “Medusa head” or “beaten egg whites”

A

Colonial morphology of Bacillus anthracis

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20
Q

Hemolysis on Blood agar plates: Bacillus anthracis

A

B. anthracis - = / non hemolytic
B. cereus - + / hemolytic

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21
Q

Motility

A

B. anthracis - = / non motile
B. cereus - + / motile

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22
Q

String of pearl

A

B. anthracis - +
B. cerues - =

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23
Q

Growth on PEA

A

B. anthracis - =
B. cereus. - +

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24
Q

Gelatin hydrolysis

A

B. anthracis - =
B. cereus. - +

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25
Q

Susceptibility to penicillin

A

B. anthracis - suceptible
B. cereus. - resistant

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26
Q

Anthrax pathogenesis: antiphagocytic

A

Poly-D-glutamic acid (protein) capsule

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27
Q

Anthrax pathogenesis - exotoxins 3 component

A

Protective antigen (PA)
Edema factor (EF)
Lethal factor (LF)

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28
Q

binds to cells, forms channel that permits EF and LF to enter

A

Protective antigen (PA)

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29
Q

adenyl cyclase causes fluid to accumulate at the site of infection and inhibit immune function

A

Edema factor (EF)

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30
Q

disrupts cell’s functions, stimulates TNF-alpha and IL-1-beta, kills infected cells

A

Lethal factor (LF)

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31
Q

Anthrax: Complications and Treatment

A

Fatality rate of gastrointestinal form is highest although rare
Meningitis may occur in 5% of cases
Antibiotic therapy: penicillin in high doses
Vaccination is available to those with high risk of exposure

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32
Q

Control and treatment : Anthrax

A

Treated with penicillin, tetracycline, or ciprofloxacin

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33
Q

Vaccine: Antrax

A

live spores and toxoid to protect livestock
purified toxoid (avirulent nonencapsulated B. anthracis strain); for high risk occupations and military personnel; toxoid 6X over 1.5 years; annual boosters

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34
Q

Common airborne and dustborne; usual methods of disinfection and antisepsis are ineffective
Grows in foods, spores survive cooking and reheating
Ingestion of toxin-containing food causes nausea, vomiting, abdominal cramps and diarrhea; 24 hour duration
No treatment
Increasingly reported in immunosuppressed

A

Bacillus cereus

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35
Q

Associated with meat, poultry, and soups
Incubation period of 8 to16 hours
Fever uncommon
Resolves within 24 hours

A

Bacillus cereus: Food poisoning - Diarrheal syndrome

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36
Q

Associated with fried rice
Abdominal cramps and vomiting
Incubation period of 1 to 5 hours
Resolves in 9 hours

A

Bacillus cereus: Food poisoning- Emetic form

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37
Q

Heat-stable enterotoxin (emetic form)
Heat-labile enterotoxin (diarrheal form)
- Similar to V. cholera – stimulates cAMP watery diarrhea
- Contaminated rice, meat, vegetables

A

Bacillus cereus: Gastroenteritis

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38
Q

Necrotic toxin, hemolysin, phospholipase C

A

Bacillus cereus: other clinical condition - Ocular infections after trauma

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39
Q

Immunocompromised persons and drug abusers

A

Bacillus cereus: other clinical condition - IV-catheter-related sepsis, endocarditis, meningitis

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40
Q

Opportunistic infections of the eye
Meningitis, septicemia, and osteomyelitis
Found as contaminants in drug paraphernalia

A

Bacillus cereus : Infections in the immunosuppressed hosts

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41
Q

Other Bacillus species
Common laboratory contaminant

A

Bacillus subtilis

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42
Q

Gram-positive, spore-forming rods
Anaerobic and catalase negative
120 species
Oval or spherical spores produced only under anaerobic conditions
Synthesize organic acids, alcohols, and exotoxins
Cause wound infections, tissue infections, and food intoxications

A

Genus Clostridium

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43
Q

most frequent clostridia involved in soft tissue and wound infections - myonecrosis or gas gangrene

A

Clostridium perfringens

44
Q

Where does clostridium in gas gangrene found

A

Spores found in soil, human skin, intestine, and vagina

45
Q

Predisposing factors of gas gangrene

A

surgical incisions, compound fractures, diabetic ulcers, septic abortions, puncture wounds, gunshot wounds

46
Q

Virulence factors of Gas gangrene: Clostridium

A

toxins – alpha toxin – causes RBC rupture, edema and tissue destruction
collagenase
hyaluronidase
DNase

47
Q

Pathology of Gas gangrene: Clostridium

A

Not highly invasive; requires damaged and dead tissue and anaerobic conditions
Conditions stimulate spore germination, vegetative growth and release of exotoxins, and other virulence factors.
Fermentation of muscle carbohydrates results in the formation of gas and further destruction of tissue.

48
Q

Gas gangrene treatment and prevention

A

Immediate cleansing of dirty wounds, deep wounds, decubitus ulcers, compound fractures, and infected incisions
Debridement of disease tissue
Large doses of cephalosporin or penicillin
Hyperbaric oxygen therapy
No vaccines available

49
Q

Clostridium difficile-Associated Disease (CDAD)

A
  • Normal resident of colon, in low numbers
    *.Causes antibiotic-associated colitis
  • relatively non-invasive; treatment with broad-spectrum antibiotics kills the other bacteria, allowing C. difficile to overgrow
  • Produces enterotoxins that damage intestines
  • Major cause of diarrhea in hospitals
  • Increasingly more common in community acquired diarrhea
50
Q

Clostridium difficile-Associated Disease (CDAD)
Treatment and prevention

A

Mild uncomplicated cases respond to fluid and electrolyte replacement and withdrawal of antimicrobials.
Severe infections treated with oral vancomycin or metronidazole and replacement cultures
Increased precautions to prevent spread

51
Q

Clostridium tetani
Common resident of soil and GI tracts of animals
Causes tetanus or lockjaw, a neuromuscular disease
Most commonly among geriatric patients and IV drug abusers; neonates in developing countries

A

Tetanus

52
Q

Tetanus pathology

A

Spores usually enter through accidental puncture wounds, burns, umbilical stumps, frostbite, and crushed body parts.

Anaerobic environment is ideal for vegetative cells to grow and release toxin.

Tetanospasmin

Anaerobic environment is ideal for vegetative cells to grow and release toxin.

53
Q

neurotoxin causes paralysis by binding to motor nerve endings; blocking the release of neurotransmitter for muscular contraction inhibition; muscles contract uncontrollably

A

Tetanospasmin

54
Q

Tetanus treatment and prevention

A

Treatment aimed at deterring degree of toxemia and infection and maintaining homeostasis
Antitoxin therapy with human tetanus immune globulin; inactivates circulating toxin but does not counteract that which is already bound
Control infection with penicillin or tetracycline; and muscle relaxants
Vaccine available; booster needed every 10 years

55
Q

rare but severe intoxication usually from home canned food

A

Clostridium botulinum : clostridial food poisoning

56
Q

mild intestinal illness; second most common form of food poisoning worldwide

A

Clostridium perfringens: clostridial food poisoning

57
Q

intoxication associated with inadequate food preservation

A

Botulism

58
Q

spore-forming anaerobe; commonly inhabits soil and water

A

Clostridium botulinum

59
Q

Botulinum Food Poisoning pathogenesis

A

Spores are present on food when gathered and processed.
If reliable temperature and pressure are not achieved air will be evacuated but spores will remain.
Anaerobic conditions favor spore germination and vegetative growth.
Potent toxin, botulin, is released.
Toxin is carried to neuromuscular junctions and blocks the release of acetylcholine, necessary for muscle contraction to occur.
Double or blurred vision, difficulty swallowing, neuromuscular symptoms

60
Q

caused by ingested spores that germinate and release toxin; flaccid paralysis

A

Infant botulism

61
Q

spores enter wound and cause food poisoning symptoms

A

Wound botulism

62
Q

Infant and Wound Botulism
Treatment and prevention

A

Determine presence of toxin in food, intestinal contents or feces
Administer antitoxin; cardiac and respiratory support
Infectious botulism treated with penicillin
Practice proper methods of preserving and handling canned foods; addition of preservatives.

63
Q

Clostrium perfringens
Spores contaminate food that has not been cooked thoroughly enough to destroy spores.
Spores germinate and multiply (especially if unrefrigerated).
When consumed, toxin is produced in the intestine; acts on epithelial cells, acute abdominal pain, diarrhea, and nausea
Rapid recovery

A

Clostridial Gastroenteritis

64
Q

Gram-Positive Regular Non-Spore-Forming Bacilli

A

Listeria monocytogenes
Erysipelothrix rhusiopathiae

65
Q

Non-spore-forming Gram-positive
Ranging from coccobacilli to long filaments
1-4 flagella
No capsules
Resistant to cold, heat, salt, pH extremes and bile
Virulence attributed to ability to replicate in the cytoplasm of cells after inducing phagocytosis; avoids humoral immune system

A

Listeria monocytogenes

66
Q

Listeria monocytogenes
Epidemiology and pathology

A

Primary reservoir is soil and water; animal intestines
Can contaminate foods and grow during refrigeration
Listeriosis - most cases associated with dairy products, poultry, and meat
Often mild or subclinical in normal adults
Immunocompromised patients, fetuses and neonates; affects brain and meninges
20% death rate

67
Q

Listeria monocytogenes
Diagnosis and Control

A

Culture requires lengthy cold enrichment process.
Rapid diagnostic tests using ELISA available
Ampicillin and trimethoprimsulfamethoxazole
Prevention – pasteurization and cooking

68
Q

Gram-positive bacillus
Common in animals
Transmitted to humans by skin wound
Occupational hazard in butchers, farmers, veterinarians
Self-limited skin lesions with erythema & eruption
May spread to bloodstream

A

Erisipelothrix rhusopathiae

69
Q

Primary reservoir – tonsils of healthy pigs
Enters through skin abrasion, multiples to produce erysipeloid, dark red lesions
Penicillin or erythromycin
Vaccine for pigs

A

Erysipelothrix rhusiopathiae

70
Q

Gram-positive, catalase-positive rods
Occur in soil and decaying vegetation

A

Aerobic Actinomycetes

71
Q

Positive (+) Mycolic acid

A

Mycobacterium
Corynebacterium

72
Q

Negative (-) mycolic acid

A

Nocardia
Streptomyces
Rhodococcus
Tropheryma
Others

73
Q

Gram-Positive Irregular Non-Spore-Forming Bacilli

A

Medically important genera:
Corynebacterium
Proprionibacterium
Mycobacterium
Actinomyces
Nocardia

74
Q

Pleomorphic; stain unevenly
20 genera; Corynebacterium, Mycobacterium, and Nocardia greatest clinical significance
All produce catalase, possess mycolic acids, and a unique peptidoglycan.

A

Gram-Positive Irregular Non-Spore-Forming Bacilli

75
Q

Gram-positive irregular bacilli
Virulence factors assist in attachment and growth.
diphtherotoxin – exotoxin

A

Corynbacterium diptheriae

76
Q

part B binds and induces endocytosis; part A arrests protein synthesis

A

2 part toxin : diphtherotoxin – exotoxin

77
Q

Gram-positive, curved pleomorphic rods
“Chinese Letters”
Aerobic/facultatively anaerobic
Grow readily on Sheep blood agar
Catalase & oxidase positive
Usually non-motile
Commensals on skin
Some species pathogenic

A

Corynebacterium

78
Q

Corynebacterium
Epidemiology and pathology

A

Reservoir of healthy carriers; potential for diphtheria is always present
Most cases occur in non-immunized children living in crowded, unsanitary conditions.
Acquired via respiratory droplets from carriers or actively infected individuals

79
Q
  • upper respiratory tract inflammation
    – sore throat, nausea, vomiting, swollen lymph nodes; pseudomembrane formation can cause asphyxiation
A

Local infection (2 stages of disease corynebacterium)

80
Q

target organs primarily heart and nerves

A

Diptherotoxin production and toxemia
( 2 stages of disease corynebacterium)

81
Q

Corynebacterium diagnostic methods

A

Pseudomembrane and swelling indicative
Stains
Conditions, history
Serological assay

82
Q

Corynebacterium treatment and prevention

A

Antitoxin
Penicillin or erythromycin
Prevented by toxoid vaccine series and boosters

83
Q

Spreads by droplet
Phospholipase D increases vascular permeability & promotes spread
Phage-coded exotoxin (A&B subunits) acts on respiratory mucous membranes interfering with protein synthesis by inactivating EF-2
Pseudomembrane of fibrin, bacteria, epithelial & phagocytic cells impairs breathing
Toxin spreads to heart, CNS, & adrenals
Selective media (cysteine-tellurite)
Identify in Public Health Labs
Protect by toxoid vaccination – DaPT

A

Diphtheria (C. diphtheriae)

84
Q

increases vascular permeability & promotes spread ( Diphtheria )

A

Phospholipase D

85
Q

acts on respiratory mucous membranes interfering with protein synthesis by inactivating EF-2 ( Diphtheria)

A

Phage-coded exotoxin (A&B subunits)

86
Q

Diphtheria selective media

A

Cysteine-tellurite

87
Q

Other pathogenic corynebacterium
Opportunistic bloodstream infections in bone marrow transplant recipients
Multiple antibiotic resistance - except vancomycin and tetracycline
Commonly carried on skin of hospitalized persons

A

C. jeikeium (JK)

88
Q

Occasional cause of UTI & stones (splits urea)
Other pathogenic corynebacterium

A

C. urealyticum

89
Q

Propionibacterium acnes most common
Gram-positive rods
Aerotolerant or anaerobic
Nontoxigenic
Common resident of sebaceous glands
Causes acne

A

Genus Proprionibacterium

90
Q

nonmotile filamentous bacteria related to mycobacteria.

A

Genera Actinomyces & Nocardia

91
Q

May cause chronic infection of skin and soft tissues

A

Actinomycetes: Filamentous Bacilli

92
Q

responsible for diseases of the oral cavity, thoracic or intestines - actinomycoses

A

Actinomyces israelii

93
Q

causes pulmonary disease similar to TB.

A

Nocardia brasiliensis

94
Q

General Characteristics
Aerobic, gram-positive, filamentous rods, sometimes resembling branched hyphae
Weakly acid-fast and may stain gram-variable
Morphologically resemble fungi, both in culture and in types of infections produced
Generally found in the environment and mostly affect immunocompromised individuals

A

Aerobic Actinomycetes:Nocardia species

95
Q

Aerobic Actinomycetes

A

Nocardia, Actinomadura, and Streptomyces species

96
Q

Significant Nocardia species

A

N. asteroides
N. braziliensis
N. caviae

97
Q

Actinomadura species

A

A. madurae
A. pelletieri

98
Q

Streptomyces species

A

None

99
Q

Clinical infections
Aerobic Actinomycetes: Nocardia, Actinomadura, and Streptomyces species

A

Pulmonary form
Mycetomas

100
Q

Laboratory Diagnosis: Nocardia, Actinomadura, and Streptomyces species
MICROSCOPY

A

Gram-positive branching filaments are seen in direct smears from sputum or aspirated material
May show beading appearance

101
Q

Expectorated sputum with purulence
Gram-positive filamentous bacilli
Suspicious for actinomycetes

A

Nocardia, Actinomadura, and Streptomyces species

102
Q

Nocardia, Actinomadura, and Streptomyces species
Cultural characteristics

A

Chalky, matte, dry, crumbly appearance
May be pigmented

103
Q

Nocardia, Actinomadura, and Streptomyces species
Identification

A

Utilization of carbohydrates
Hydrolysis of casein, tyrosine, and xanthine

104
Q

are not acid-fast

A

Actinomadura and Streptomyces sp.

105
Q

Sputum smear, partially acid-fast bacilli, consistent

A

Nocardia sp.

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