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2nd year - Microbiology > Gram Positive Bacteria - Lecture 5 > Flashcards

Gram Positive Bacteria - Lecture 5 Flashcards

1
Q

What are streptococcus sp. characteristics? (Morphology)

A

These bacteria are gram positive COCCI bacteria that are organized in chains (~2-6/chain)

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2
Q

How are streptococcus bacteria clasified?

A

These are classified based on their hemolytic activity. Classified as alpha, beta or gamma.

Beta-hemolytic bacteria are further classified based on Lancefield groupings (A-U), which is their cell wall carbohydrate antigen.

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3
Q

What are the four streptococcus human pathogens?

A

1) Streptococcus pneumoniae
2) Streptococcus pyogenes
3) Streptococcus agalactiae
4) Streptococcus mutans

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4
Q

Describe alpha-hemolytic bacteria.
What colour does it appear on a blood agar where the colonies grow?
Give an example.

A

Partial hemolysis
Appears green in colour
S. pneumoniae

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5
Q

Describe beta-hemolytic bacteria.
What colour does it appear on a blood agar where the colonies grow?
Which further classes are the most pathogenic?
Give an example.

A

Complete hemolysis
Appears as a full clearing on and around where the colonies grow
Lancefield groups A and B are the most pathogenic
S. pyogenes (group A) and S. agalactiae (group B)

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6
Q

Describe gamma-hemolytic bacteria.
What colour does it appear on a blood agar where the colonies grow?
Give an example.

A

No hemolysis
No clearing
Enterococcus faecalis

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7
Q

What is another name for streptococcus pneumoniae?

A

Pneumococcus

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8
Q

Describe pneumococcus: morphology, encapsulated or acapsular, bile sensitivity or not?

A

Diplococci
Encapsulated
Bile sensitivity

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9
Q

What are two features of a pneumococcus infection?

A

Bacterial pneumonia

Bacterial meningitis

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10
Q

What bacterial infection is described as:
Fever, malaise, cough, pleuritic chest pain
Purulent or bloody sputum
Otitis media (inflammation of the inner ear)

A

Bacterial pneumonia

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11
Q

What bacterial infection is described as:

Stiff neck, headache, fever (characteristic triad)

A

Bacterial meningitis

streptococcus pneumoniae is the most common cause of meningitis in children

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12
Q

How is streptococcus pneumoniae transmitted and how long is the typical incubation period?

A

Transmitted via respiratory droplets

Incubation period is 1-3 days

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13
Q

What are treatment strategies for streptococcus pneumoniae?

A

Vaccine preventable

Broad-spectrum antibiotic resistance tests

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14
Q

What else is Streptococcus pyogenes known as?

A

Group A Streptococcus (GAS)

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15
Q

GAS is CAMP-tes negative, meaning what?

A

CAMP-factor does NOT increases hemolytic activity (unlike beta-hemolytic S. aureus)

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16
Q

What are clinical features of GAS?

A

Pharyngitis/Tonsilitis - aka “strep throat”
Scarlet fever
Infections of the skin

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17
Q

Describe pharyngitis/tonsilitis (strep thoat)

A

Inflammation of the pharynx/tonsils

Fever, malaise, sore throat

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18
Q

Describe scarlet fever

A

Occurs in patients with strep throat (usually children)

Erysypelas (rash), typically on the face, “strawberry tongue”

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19
Q

What are four infections of the skin caused by GAS? (give brief descriptors)

A

1) Impetigo - superficial, common in children, contact sport
2) Cellulitis - subcutaneous, inflammation of the skin and dermal layers
3) Folliculitis - inflammation of the hair follicles
4) Necrotizing fasciitis - aka flesh-eating disease

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20
Q

What are some potential complications of GAS infections? (3)

A

Acute rheumatic fever
Acute glomerulonephritis
Infective cardiopathies

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21
Q

What complication of GAS infection is described as:
Polyarthritis, carditis, rheumatic heart disease
May occur weeks following GAS infectoin

A

Acute rheumatic fever

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22
Q

Which complication of GAS infection could lead to an autoimmune disease - antibody cross-reactivity against joints and myocardium (type II hypersensitivity)

A

Acute rheumatic fever

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23
Q

What complication of GAS infection involves inflammation of the glomeruli (kidney) and may occur weeks following the GAS infection of the URT or skin

A

Acute glomerulonephritis

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24
Q

What is the most common infective cardiopathies (a complication of a GAS infection)

A

Endocarditis most common

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25
Q

How are GAS infections transmitted and how long is the typical incubation period?

A

Transmitted via respiratory droplets

Incubation period - 1-5 days

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26
Q

What are treatment strategies of GAS infections?

A

Penicillin and related antibiotics, cephalosporins

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27
Q

What else is streptococcus agalactiae known as?

A

Group B streptococcus (GBS)

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28
Q

Are GBS CAMP-test positive or negative? meaning what?

Encapsulated or acapsular?

A

CAMP-test positive - meaning CAMP-factor increases hemolytic activity
Encapsulated

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29
Q

What are clinical features of GBS? Briefly describe. (5)

A

1) Symptomatic in newborns, elderly, immunocompromised, risk of maternal transmission
2) Newborn pneumonia - fever, myalgia, fatigue, consolidation of the lung, chest pain
3) Meningitis (neonatal) - fever, headache, neck stiffness
4) Sepsis - leading cause of neonatal sepsis
5) UTI - less common

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30
Q

How are GBS infections transmitted?

How long is the typical incubation period of GBS?

A

Transmitted via respiratory droplets

Incubation period 5-7 days

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31
Q

What are treatment strategies of GBS infections?

A

Penicillin and other bata-lactams

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32
Q

What does viridans streptococcui include?

A

Includes streptococci mutans and other commensals of the mouth

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33
Q

Are viridans streptococci optichin-sensitive or nonsensitive, encapsulated or acapsular?

A

Optihin-sensitive

Acapsular

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34
Q

These clinical features are characteristic of which bacterial infection?

1) Symptomatic in newborns, elderly, immunocompromised, risk of maternal transmission
2) Newborn pneumonia - fever, myalgia, fatigue, consolidation of the lung, chest pain
3) Meningitis (neonatal) - fever, headache, neck stiffness
4) Sepsis - leading cause of neonatal sepsis
5) UTI - less common

A

GBS clinical features

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35
Q

These clinical features are characteristic of which bacterial infection?

1) Impetigo - superficial, common in children, contact sport
2) Cellulitis - subcutaneous, inflammation of the skin and dermal layers
3) Folliculitis - inflammation of the hair follicles
4) Necrotizing fasciitis - aka flesh-eating disease

A

GAS clinical features

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36
Q

These clinical features are characteristic of which bacterial infection?

1) Plaque, tooth decay, cavities
2) infective cardiopathies - subacute infective carditis

A

Viridans streptococci

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37
Q

Wha are the assoiciated risk factors of cardiopathies? and describe presentation.

A

Risk factors: congenital heart defects/valvular defect, artificial heart valves, diabetes, dental surgery.

Presentation: slowly progressing, low grade to no fever, chest pain and sepsis

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38
Q

What are clinical features of viridans streptococci? (2)

A

1) Plaque, tooth decay, cavities

2) infective cardiopathies - subacute infective carditis

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39
Q

What is the incubation period of viridans streptococci?

A

variable incubation period

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40
Q

What are the treatment strategies for viridans streptococci?

A

Brushing and antiseptic mouthwash, antibiotics for sepsis and cardiopathy

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41
Q

What are the characteristics of Staphylococcus?

A

Gram positive cocci
Organized in grape-like clusters
Catalase-positive, facultative anaerobes

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42
Q

What are human pathogens of Staphylococcus? (3)

A

1) Staphylococcus aureus - skin infection, bacterial pneumonia, bacterial meningitis
2) Staphylococcus epidermidis - sepsis (IV catheters and medical prostheses
3) Staphylococcus saprophyticus - UTIs, cystitis

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43
Q

Give three characteristics of Staphylococcus aureus

A

1) Opportunistic pathogen - resident on skin
2) Characteristic golden colonies (“aura” = golden)
3) Identification - morphology, coagulase (+)

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44
Q

What are some diseases caused by Staphylococcus aureus? (7)

A

1) Skin infections - impetigo, abscess, cellulitis, scalded skin syndrome
2) Sepsis/Septic shock
3) Bacterial pneumonia
4) Bacterial meningitis
5) Mastitis
6) Infective cardiopathy
7) Food poisoning

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45
Q

These diseases can all be caused by which bacterial infection?

1) Skin infections - impetigo, abscess, cellulitis, scalded skin syndrome
2) Sepsis/Septic shock
3) Bacterial pneumonia
4) Bacterial meningitis
5) Mastitis
6) Infective cardiopathy
7) Food poisoning

A

Staphylococcus aureus infection can cause these diseases

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46
Q

What is described as a collection of pus in a tissue associated with inflammation?

A

An abscess

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47
Q

What is described as blisters and sores (pustulous or not), found commonly on the face/neck?

A

Impetigo

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48
Q

What is described as an inflammation of connective tissue in the dermal, subcutaneous layers of the skin?

A

Cellulitis

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49
Q

What is described as pain and redness of the skin, blisters and desquamation?

A

Scalded skin syndrome

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50
Q

Describe staphylococcal bacterial pneumonia (caused by staphylococcus aureus)

How would it be treated?

A

Commonly nosocomial, secondary pneumonia
Fever, chest pain, coughing, difficulty breathing
Patchy areas of consolidation in the lung
Rapidly progressive

Treat with antibiotics, steroids

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51
Q

Describe Sepsis

A

Septic inflammatory response, spread to various organs

Multiple presentations, organ effects, may lead to secondary infection even following clearance from the blood

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52
Q

What percentage of bacterial meningitis is due to staphylococcal aureus?

A

1-10% of meningitis

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53
Q

What is meningitis?

What does it cause/symptoms?

A

Inflammation of the meninges in the brain causing cognitive impairment and fever

54
Q

Describe acute infective endocarditis:

What is it, and what are the symptoms?

A

Inflammation of the endocardium

Sudden onset of fever, new/changing heart murmer, chest pain, Osler’s nodes and Janeway lesions on the hands and feet

55
Q

What bacterial infection can cause mastitis?

Describe mastitis

Common treatments

A

Caused by Staphylococcus aureus

Infection of the breast tissue
Abrasions and skin breaks during breastfeeding common, risk of sepsis and ineffective cardiopathy
Very common in cattle

Common treatments: antibiotics, surgery

56
Q

Describe food poisoning as caused by Staphylococcus aureus

Source

A

Mishandled meat, poultry, eggs, dairy
Salt-stable (cured foods)
Mostly due to toxin production (heat-stable)
produce enterotoxins A-E
Do not reheat food that has been at room temperature for more than 2hrs
Causes severe vomiting 2-4hrs after infection

57
Q

What are drug-resistant staphylococcus aureus?

Caused by what?

A

Methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA & VRSA)

Caused by antibiotic overuse, misuse, and patient non-compliance

Nosocomial

58
Q

What are treatment strategies for MRSA and VRSA?

A

Incision, drainage or surgery of affected area
1st and 2nd generation glycopeptide antibiotics - inhibit bacterial cell wall and RNA synthesis
Streptogramins - inhibit bacterial ribosome

59
Q

staphylococcus aureus caused epidermidis is commensal of the skin. is it
Coagulase positive or negative?
Hemolytic or non-hemolytic
Encapsulated or acapsular?

A

Coagulase negative
Non-hemolytic
Encapsulated

60
Q

Septicemia is caused by an opportunistic infection transmitted from what (typically)?

A

Medical devices - catheters, shunts, prostheses etc.
Biofilm formations on devices is a major virulence factor due to adhesion molecules and ability to bind to plastic device

61
Q

What are some clinical features of staphylococcus aureus epidermidis?

A

Depends on site of infection
UTI - pain or difficulty urinating
Subacute infective endocarditis

62
Q

What are treatment strategies for staphylococcus aureus epidermidis?

A

vancomycin and related, although antibiotic resistance is common

63
Q

Staphylococcus saprophyticus
Coagulase positive or negative?
Drug resistant? to what?
Encapsulated or acapsular?

A

Coagulase negative
Novobiocin resistant
Some capsulated, some acapsular strains

64
Q

Treatment for Staphylococcus saprophyticus

A

Treat with Quinolones - inhibit DNA replication and trimethoprim - folic acid and metabolism inhibitor

65
Q

Give characteristics of Bacillus sp.

Gram - or +

Catalase - or +

Size

Oxygen tolerance

Spore-forming or not

A

Gram (+) rods, catalase (+)

Relatively large bacteria (35um long)

Aerobic or facultatively anaerobic

Sporeforming

66
Q

Give four important species of Bacillus

A

1) Bacillus subtilus
2) Bacillus cereus
3) Bacillus anthracis
4) Bacillus thurigiensis

67
Q

Describe the characteristics of endospores including structure, conditions of formation, content

A

Dormant, hearty, nonreproductive structure

Formed ‘from within’, during conditions of stress

Genetic material, some cytoplasm, tough exterior

‘Cryptobiotic’

68
Q

What makes endospores particularly hearty

A

Resist heat, freezing,
dessication

Resist acidity, chemical disinfectants, irradiation

Commonly found in soil and water

Survive long periods of time (millions of years)

Endospores can survive unfavourable conditions for extremely long periods of time

Conditions that favour vegetation lead to germination of spores (sufficient nutrients, oxygen, moisture, etc.)

69
Q

Other than Bacillus, what are some other spore forming bacteria?

A

Clostridium sp. cyanobacteria

70
Q

Saporophytes a classification of bacillus
How do they obtain nutrients?
Where do they live?

A

Obtain nutrients from dead organic matter

Saprophytic bacteria live mostly in soil/water

71
Q

Give three Saprophyte human pathogens

A

1) Bacillus subtilus - food poisoning
2) Bacillus cereus – food poisoning, mastitis, skin infections

3) Bacillus anthracis – anthrax
diseases

72
Q

What are some saprophyte probiotics? (3)

A

1) Lactobacillus sp.
2) B. subtilis
3) B. cereus

73
Q

What is a saprophyte insect pathogen?

A

Bacillus thuringiensis

74
Q

This bacteria is a saprophyte and member of the resident gut flora. It is motile (flagellate) and may appear in groups or chains. What is it?

A

B. subtilus

75
Q

Pathogenic B. subtilus can cause ___1___
It is ___2___ in early phase and ___3___ in late phase
4) How long does it take to resolve and 5) how long is the incubation period?

A

1) food poisoning - rare
2) Emetic
3) Diarrheal
4) 24-48hrs
5) Short incubation - hours

76
Q

What are virulence factors of B. subtilus?

A

Sibtilisin - serine endopeptidase

Catalase - metabolize H2O2

77
Q

This bacteria is a saprophyte and a member of the resident gut flora. It is motile (flagellate), appears in groups or chains and is β-haemolytic. What is it?

A

B. cereus

78
Q

What are four clinical presentations of pathogenic B. cereus?

A

1) Food poisoning (2-5%) - diarrheal (long incubation), Emetic (short incubation)
2) Mastitis
3) Skin infection
4) Diseases associated with the sepsis in immunocompromised patients

79
Q

This bacteria is a saprophyte, nonmotile (aflagellate) and chainforming. It is an etiological agent of anthrax diseases and was discovered by Robert Koch in 1877. What is it?

A

B. anthracis

80
Q

What are Koch’s four postulates?

A
  1. The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
  2. The microorganism must be isolated from a diseased organism and grown in pure culture.
  3. The cultured microorganism should cause disease when introduced into a
    healthy organism.
  4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific
    causative agent.
81
Q

What are the three classifications of B. anthracis?
Which is most fatal, very rare?
Causes?

A

1) Pulmonary anthrax - most fatal
- Caused by inhalation of spores (not contagious)

2) Cutaneous anthrax
- Introduction of spores through breaches in the skin

3) Intestinal anthrax - very rare
- Ingestion, symptoms of food poisoning

82
Q

Describe the Early stages of pulmonary anthrax

A

Fever, coughing, sore throat, fatigue, sweating, vomiting, diarrhea, headache, nausea, chest pain, and shortness of breath

83
Q

Describe the late stages of pulmonary anthrax

A

High fever, chest pain, hemorrhagic pathology, death within 48 hours

84
Q

Describe the appearance of cutaneous anthrax

A

Lesions with black necrotic center

85
Q

What could Septicemia following an infection of anthrax lead to?

A

Meningitis

86
Q

What are virulence factors of B. anthracis?

A

Anthrax lethal toxin – degrades host signalling
pathway components, leading to cell death

Anthrax edema toxin – causes accumulation of fluid in tissue

87
Q

What are the incubation periods of B. anthracis infections?

1) pulmonary
2) Cutaneous
3) GI

A

1) 1-7 days
2) 1-2 days
3) 1-7 days

88
Q

What are treatments for B. anthracis?

A

Vaccine limited availability (military personnel)

Early tx very key – 60 day regimen of ciproflaxin (quinolone) or doxycycline (tetracycline)

89
Q

Give characteristics of Clostridium sp.

Gram - or +

Morphology

Oxygen tolerance

Spore-forming or not

A

Gram positive

Rods

Anaerobic (mostly obligate anaerobic)

Endospore forming

90
Q

What are four Clostridium human pathogens?

A

1) Clostridium tetani
2) Clostridium botulinum
3) Clostridium perfringens
4) Clostridium difficile

91
Q

What do free radicals/reactive oxygen species (ROS) do? (4)

A

1) Modify proteins
2) Regulate the function of proteins
3) Damage nucleic acid
4) Cause cell death

92
Q

What antioxidant defenses to some bacteria posses? (3)

A

1) Superoxide dismutase
2) Peroxidase
3) Catalase

93
Q

What are four diseases caused by Clostridium sp.?

A

1) C. tetani - Tetanus
2) C. botulinum - Botulism, Floppy baby syndrome, Wound infection
3) C. perfringens - Gastroenteritis, Gas gangrene
4) C. difficile - Antibiotic-associated diarrhea

94
Q

Describe C. tetani
Oxygen tolerance
Motility

A

Appear as ‘tennis rackets’ under microscope examination
Obligate anaerobe
Motile

95
Q

Describe generalized tetanus and what it may lead to

A

Prolonged contraction of skeletal muscle fibers

Characteristic opisthotonus
–Severe hyperextension and spasticity of head, neck, and spine
–Spasm of axial muscles of the spinal column leads to characteristic arching

May lead to respiratory failure

Hypertension, tachycardia

96
Q

How is C. tetani transmitted?

What is its incubation period?

A

Transmitted via infected wounds

Incubation period usually 1 wk, but could be several months

97
Q

How is neonatal tetanus infection transmitted?

A

Infection through umbilical stump

98
Q

Describe localized tetanus

A

Spasms are isolated to the site of injury

Self-resolving

99
Q

What classifies cephalic tetanus?

A

CNS involvement - rare

100
Q

What is the treatment for C. tetani?

A

Vaccine (tetanus shot) = toxoid vaccine

Childhood vaccine with booster recommended every 10 years

Administered following severe trauma to the skin (postexposure prophylaxis)

101
Q

What is C. botulinum oxygen tolerance?

A

Obligate anaerobe - expresses superoxide dismutase

102
Q

How is food-borne botulism transmitted? (What are risk factors)

A

Ingestion of spores from improperly canned foods

Sporulation may occur at higher pH

103
Q

What are symptoms of botulism?

A

Flaccid muscle paralysis - slurred speech, droopy eyelids, difficulty swallowing, generalized muscle weakness

104
Q

Botulinum toxin is a neurotoxin with multiple serotypes. Which serotypes cause human disease and how does the toxin act?

A

Serotypes A-G exist, with A, B, E & F causing human disease.

Toxin acts by blocking the release of acetylcholine from motor nerve endings

105
Q

How is infant botulism transmitted?

“floppy baby syndrome”

A

Food-borne

Honey - spores found in honey can germinate in the less acidic gut of newborns

106
Q

What is wound botulism?

A

Infection of wound with spores

107
Q

What are treatments for C. botulinum?

A

Antitoxin - antibody against botulinum toxin
Ventilator for respiratory complications
No vaccine available

108
Q

What are commercial uses for C. botulinum?

A

Muscle pain disorders
Hyperhydrosis
Botox - cosmetic

109
Q

Compare direct vs indirect pathology

A

Direct pathology comes from the effect of the pathogen of a cell, tissue or organ

  • Viral replication and lysis in a tissue causes damage to that tissue
  • Bacterial toxins may cause local or distal effects - tetanospasmin and botulinum toxin exert their effect in the CNS even though the bacteria don’t replicate in the CNS

Indirect pathology comes from secondary effects and immune pathology

  • Cell damage mediated by inflammatory mediators at a site of replication
  • Symptoms associated with tissue remodeling following damage
110
Q

Which bacteria is non-motile and double-zone heamolysis?

A

C. perfringens

111
Q

Describe the effects of Clostridium perfringens enterotoxin (CPE)

A

Tissue necrosis

Destroys tight junctions between endothelial cells in the gut

112
Q

What are symptoms of C. perfringens

A

Diarrhea, vomiting, abdominal cramping, fever

Clostridial necrotizing enteritis (rare, fatal)

113
Q

How long is the incubation period for C. perfringens?

A

8-24 hours

114
Q

Gas gangrene is a serotype of C. perfringens, which one? and what is it also known as?

How is it transmitted?

A

Serotype A
aka clostridial myonecrosis

Transmitted by infection at a site of trauma, usually lacking blood supply - contaminated surgical equipment, gloves et.

115
Q

What are the symptoms of gas gangrene?

what is its incubation period?

A

Muscle wasting
Edematous, necrotic blisters
Putrefcation of tissue with smell

Incubation period 1-4 days

116
Q

What are the virulence factors of C. perfringens?

A

α-toxin – destroys tissue and produces gas

β, ε, ι toxins – increase vascular permeability

δ, φ toxins – haemolysins

117
Q

What are treatments for C. perfringens?

A

Amputation

Penicillin, clindamycin, rifampicin, metronidazole

118
Q

Describe C. difficile:
Motility?
Oxygen tolerance?
Opportunistic?

A

Motile
Obligate anaerobe
Opportunistic pathogen

119
Q

Describe antibiotic resistant diarrhea (c. difficile)

A

occurs as a consequence of antibiotic useage

Fever, diarrhea, vomiting, abdominal pain, crampin

120
Q

Describe pseudomembranous colitis (c. difficile)

A

Inflammation of the colon
Pseudomembrane formation in the colon
Abdominal pain with rebound tenderness

121
Q

What are treatments for c. difficile?

What is the recurrence rate

A

Halting current antibiotics
Vancomycin, metronidazole
Recurrence rate is extremely high

122
Q

How is c. difficile transmitted and how can it be prevented?

A

Transmitted fecal-oral

Prevented via hygiene!!

123
Q

This bacteria is gram positive and polymorphic.
It’s toxin inhibits translational machinery.
What is it?

A

Corynebacterium diptheria (diptheria)

124
Q

What are clinical features of diptheria?

A

Sore throat, low fever, dark pseudomembrane on the tonsils, pharynx, and/or nasal cavity

Fever, chills, fatigue, sore throat, hoarseness, cough, headache, painful swallowing, difficulty breathing

Skin lesions also common

125
Q

What are complications of diptheria?

A

Cardiac and nervous system complications

126
Q

How is diptheria transmitted and what is its incubation period?

A

Transmitted through contact, respiratory droplets and contaminated food

Incubation period 2-5 days

127
Q

What are treatments for diptheria?

A

Toxoid vaccine available (pentavalent or DPT)

Responsive to multiple antibiotics

Severe cases treated with diptheria
antitoxin

128
Q 
Describe characteristics of Listeria monocytogenes (lysteriosis)
Gram positive/negative?
Morphology
Food- air- water-borne?
Oxygen tolerance?
Motility?
Psychrotrophic?
Reproduction?
Hemolysis?
Catalase positive/negative>
A 
Gram positive
Rod-shaped
Food-born pathogen
Facultative anaerobe
Motile
Psychrotrophic (survive cold temps)
May reproduce extracellularly or intracellularly in macrophages
Beta-hemolytic
Catalase positive
129
Q

What are clinical presentations of Listeriosis?

A

Diarrhea, fever, muscle aches
CNS involvement
20-30% fatality rate in infected patients

130
Q

How is listeriosis transmitted and how long is its incubation period?

A

Transmitted through ingestion of contaminated food (processed or fresh)

incubation period is 1-70 days (typically 2-3 wks)

131
Q

What are treatments for listeriosis?

A

Ampicillin or other antibiotics

2nd year - Microbiology (21 decks)

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