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Microbiology > Unit 7A > Flashcards

Unit 7A Flashcards

1
Q

Describe staphylococcus

A

Gram positive
Cocci in Grape like clusters
Facultative anaerobes (can grow with or without oxygen)
Produces capsules and slime layers
Catalase positive (has the enzyme that breaks down hydrogen peroxide)

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2
Q

Examples of diseases of staphylococcus

A

S. aureus
MRSA
S. intermedius

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3
Q

What are some exotoxins that staphylococcus produce

A

Hemolysin (damage RBCs and hemoglobin) (most have some degree of hemolysis)

Coagulase (binds to fibrin and causes clotting, helps bacteria to hide and resist phagocytosis. Also causes pus to thicken)

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4
Q

Where is staphylococcus commonly found

A

In the nevironment and in hospital settings (nosocomial) and in normal flora

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5
Q

The slime layer staphylococcus produce allow

A

Bacteria to form biofilms

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6
Q

Where is staphylococcus commonly found on the body (normal flora)

A

Skin and mucus membranes (skin, eyes, ears, respiratory tract, urogenital tract, GI tract)

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7
Q

Staphylococcus is primarily opprotunistic , this means

A

Disease only occurs when natural barriers are compromised (trauma to skin/mucosa, or inflammation)

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8
Q

What is the number one cause of mastitis in dairy cows

A

Staphylococcus aureus

Can also be caused by S. intermedius or S. epidermidis

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9
Q

Mastitis is an opprotunistic infection and occurs when there is

A 
Poor herd management 
Poor hygiene 
Stress during 3rd trimester pregnancy, or gestation
Changes in diet
Lactation
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10
Q

Describe chronic subclinical mastitis due to S. aureus

A

Difficult to identify and treat

Milk and cow is normal/healthy on PE

Decreased total milk yield

Increased somatic cell count in milk, or low levels of bacteria in milk

Can be infected for months or years

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11
Q

Why can you not emilimate S. aureus mastitis

A

Ubiquitous

Part of normal flora

Resistant to drying -survuves weeks in environment

Resistant to extreme cold and pasteurization

Can survive in 12% NaCl or 1% phenol for up to 15 minutes

Some strains have antibiotic resistance

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12
Q

How can you prevent mastitis

A 
Maintain milk equipment 
Better milking practices (teat dripping)
Fly control
Nutritional management 
Calving management
Screening for chronically infected cows and removing the from the herd
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13
Q

What is MRSA

methicillin Resistant Staphylococcus aureus

A

Resistant to methicillin (antibiotic)

Can be acquired from the community or hospitals depending on the strain

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14
Q

What is methicillin

A

A semisynthetic derivative of penicillin used against bacteria that are resistant to penicillin but then bacterial resistance to methicillin developed

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15
Q

Why is hospital acquired MRSA difficult to treat

A

Because it is resistant to a wide range if different antibiotic classes

Common in skin and ear infections in vet clinics

Patient must be isolated to prevent spread

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16
Q

What is community acquired MRSA

A

Up to 2% of the human population carries MRSA in normal flora

Has limited antobiotic resistance (mostly to beta-lactam class)

Immunocompromised individuals develop a mild illness but is difficult to treat

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17
Q

How do you prevent MRSA

A

Testing before using antibiotics and only use antibiotics when needed
Autoclave materials
Hand washing

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18
Q

What is staphylococcus intermedius pyoderma

A

Common in dogs, part of their normal flora

Is an opprotunistic infection

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19
Q

The opprotunistic infection of staphylococcus intermedius pyoderma occurs with

A

Allergies (food) (atopy - allergy materials)

Skin parasites

Immunosuppression

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20
Q

Why do allergies cause Staph pyoderma

A

Primary inflammation causes a warm, moist environment, which danages skin barrier so bacteria can enter subcutis and allow overgrowth of normal flora

21
Q

How do you collect a sample for a culture

A

Clean AROUND the lesion with water and mild cleanser (not alcohol/disinfectant)

Use sterile culterette swab to collect a sample, rub gently over the lesion (brewk open pustules or lift crysts to reveal lesion) (avoid hair)

Place in transport media

22
Q

Describe streptococcus

A 
Geam positive
Cocci in chains or pairs 
Non motile
Facultative anaerobes 
Pathogenic soecies ferment carbohydrates 
Catalase negative
23
Q

What does the catalase test do

A

Used to differentiate between staphylococcus and streptococcus (staphylococcus is catalase positive, streptococcus is negative)

24
Q

What are some pathogenica factors of streptococcus

A

Capsules
Exotoxins
Part of normal flora
Primaryily opprotunistic

25
Q

What do capsules help streptococcus with

A

Helps resist phagocytosis by WBCs

More pathogenic strains have capsules

26
Q

What exotoxins do streptococcus make

A

Hemolysin
Cardiotoxin

Streptococcal pyrogenic exotoxins (cause toxic shock syndrome)

Streptococcal group antigens (species grouped accoriding to group A and B antigens) (help in attaching to tissues)

27
Q

Where is streptococcus found in normal flora

A 
Mucous membranes 
Upper respiratory tract
Lower urogenital tract 
Skin
GI tract
28
Q

Describe how streptococcus is opportunistic

A

It is in some areas of normal flora, if it is present in urine ir internal tissues it is pathogenic

Can be secondary in diseased tissues (have hugher than normal numbers but did not cause disease)

29
Q

Life cycle of a sporulation

A

Sporulation: spore forms inside cytoplasm (6-12 hours)

Free spore (thick shell, resistant, dominant, metabolically inactive)

-return of H2O and nutrients in hospital environment-

Germination: return to metabolically active form (1-1.5 hours)

Vegetative form: growing, metabolically active

-lack of nutrients-

Sporulation

30
Q

Describe gram positive rods

A

Spore forming: Bacillus anthracis and clostridium

Non spore forming: histeria monocytogenes (zoonotic, neurological symptoms) and Rhodococcus equi (foal pneumonia)

31
Q

What are bacterial endospores

A

The hibernation stage of some bacteria (Bacillus spp. and Clostridium spp.)

Different than persister cells, sporulation is triggered by starvation: spore genes are turned on and the genes for metabolism, growth and repair are turn off (vise versa during growth)

32
Q

What are the physical changes that occur with endospores

A

Thick protein coat develops around the nucleoid

Chromosomal DNA condenses

Water is removed from the cytoplasm

33
Q

What is germination and when is it triggered

A

When a bacteria breaks out of the protein coat and it can start replicating again

Triggered by the return of water and nutrients

Genes for growth, replication and repair are turned on

Bacteria becomes metabolically active

34
Q

True or false
Endospores are easy to see when being stained because they do not takenup the stain, then are clear spots in the center of the rod

A

True

35
Q

Two important spore forming bacteria in vet med

A

Bacillus antracis (Anthrax)

C. perfeimgens: clostridial diarrhea

36
Q

Describe Bacillus anthracis

A

Gram positive
Long chain rods
Strict anaerobe
Spore forming

37
Q

Describe transmission and exposure of antrax

A

Horizontal transmission: most commonly ingestion if contaminated soil (gastrointestinal anthrax)

Zoonotic

Most common in cows and sheep

38
Q

Describe anthrax Epidemiology

A

Endemic in saskatchewan

Environmental reservoir (soil, water, dried organic matter, aerosolized in air/wind, fludding causes spores in the ground to reach the surface)

39
Q

Describe pathology of anthrax

A

Ingestion, inhalation ot absorption through skin of spore enters the small intestine (triggers germination)

Incubation period: few hours to 3 weeks depending on dose)

Absorption of exotoxins

40
Q

What are the 2 exotoxins produced by vegetative B. anthracis

A

1) causes severe edema and tissue necrosis (causes decreased oxygen to advance spread)
2) kills WBCs so host camnot fight the infection

41
Q

What are the clinical signs of anthrax

A

Related to tissue necrosis and edema

Death (24-48 hours of the start of clinical signs)

Severe damage to cessel walls due to edema toxin causes fatal hemorrhage

42
Q

What is the treatment, prevention and control of anthrax

A

Vegetative form of anthrax: antibiotics

Vaccines

Control the spread of spores in environment

43
Q

How do you control the spread of spores of anthrax in the environment

A

Very hard to destroy spores

Prevent air exposure
Plug all openings of carcasses 
Secure head in a plastic bag tied around neck
Protect carcass from scavengers 
Burn carcass
44
Q

True or false

Anthrax is a reportable disease and must be reported to the CFIA

A

True

45
Q

What is the purpose of tracking reportable diseases

A

To identify source of infection
To prevent spread
To track rate of spread
To ensure there is no risk of it entering canada

46
Q

What are characteristics of reportable diseases

A 
High mortality and/or morbidity 
Often no treatment
High risk of transmission 
Economic importance 
Zoonosis 
Not currently in canada 
Emerging diseases
47
Q

Describe Clostridium perfringens

A

Widespread in nature

Part of normal GI flora in most species

NOT a strict anaerobe (different from other clostridia strains)

Most common cause of small animla diarrhea (mild but can be fatal) (scowers in calces, lambs, piglets, foals)

Can cause fatal diarrhea in adult livestock

Associated with antibiotic triggered diarrhea in pocket pets

Zoonotic

48
Q

Describe diagnosing C. perfringens diarrhea

A

Fecal smears , Swab of rectum or fecal sample

Diagnosis is by increased levels of typical large gram positive rods with or without spores

Microbiology (12 decks)

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