Unit 7A Flashcards
Describe staphylococcus
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)
Examples of diseases of staphylococcus
S. aureus
MRSA
S. intermedius
What are some exotoxins that staphylococcus produce
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)
Where is staphylococcus commonly found
In the nevironment and in hospital settings (nosocomial) and in normal flora
The slime layer staphylococcus produce allow
Bacteria to form biofilms
Where is staphylococcus commonly found on the body (normal flora)
Skin and mucus membranes (skin, eyes, ears, respiratory tract, urogenital tract, GI tract)
Staphylococcus is primarily opprotunistic , this means
Disease only occurs when natural barriers are compromised (trauma to skin/mucosa, or inflammation)
What is the number one cause of mastitis in dairy cows
Staphylococcus aureus
Can also be caused by S. intermedius or S. epidermidis
Mastitis is an opprotunistic infection and occurs when there is
Poor herd management Poor hygiene Stress during 3rd trimester pregnancy, or gestation Changes in diet Lactation
Describe chronic subclinical mastitis due to S. aureus
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
Why can you not emilimate S. aureus mastitis
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
How can you prevent mastitis
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
What is MRSA
methicillin Resistant Staphylococcus aureus
Resistant to methicillin (antibiotic)
Can be acquired from the community or hospitals depending on the strain
What is methicillin
A semisynthetic derivative of penicillin used against bacteria that are resistant to penicillin but then bacterial resistance to methicillin developed
Why is hospital acquired MRSA difficult to treat
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
What is community acquired MRSA
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
How do you prevent MRSA
Testing before using antibiotics and only use antibiotics when needed
Autoclave materials
Hand washing
What is staphylococcus intermedius pyoderma
Common in dogs, part of their normal flora
Is an opprotunistic infection
The opprotunistic infection of staphylococcus intermedius pyoderma occurs with
Allergies (food) (atopy - allergy materials)
Skin parasites
Immunosuppression
Why do allergies cause Staph pyoderma
Primary inflammation causes a warm, moist environment, which danages skin barrier so bacteria can enter subcutis and allow overgrowth of normal flora
How do you collect a sample for a culture
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
Describe streptococcus
Geam positive Cocci in chains or pairs Non motile Facultative anaerobes Pathogenic soecies ferment carbohydrates Catalase negative
What does the catalase test do
Used to differentiate between staphylococcus and streptococcus (staphylococcus is catalase positive, streptococcus is negative)
What are some pathogenica factors of streptococcus
Capsules
Exotoxins
Part of normal flora
Primaryily opprotunistic
What do capsules help streptococcus with
Helps resist phagocytosis by WBCs
More pathogenic strains have capsules
What exotoxins do streptococcus make
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)
Where is streptococcus found in normal flora
Mucous membranes Upper respiratory tract Lower urogenital tract Skin GI tract
Describe how streptococcus is opportunistic
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)
Life cycle of a sporulation
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
Describe gram positive rods
Spore forming: Bacillus anthracis and clostridium
Non spore forming: histeria monocytogenes (zoonotic, neurological symptoms) and Rhodococcus equi (foal pneumonia)
What are bacterial endospores
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)
What are the physical changes that occur with endospores
Thick protein coat develops around the nucleoid
Chromosomal DNA condenses
Water is removed from the cytoplasm
What is germination and when is it triggered
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
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
True
Two important spore forming bacteria in vet med
Bacillus antracis (Anthrax)
C. perfeimgens: clostridial diarrhea
Describe Bacillus anthracis
Gram positive
Long chain rods
Strict anaerobe
Spore forming
Describe transmission and exposure of antrax
Horizontal transmission: most commonly ingestion if contaminated soil (gastrointestinal anthrax)
Zoonotic
Most common in cows and sheep
Describe anthrax Epidemiology
Endemic in saskatchewan
Environmental reservoir (soil, water, dried organic matter, aerosolized in air/wind, fludding causes spores in the ground to reach the surface)
Describe pathology of anthrax
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
What are the 2 exotoxins produced by vegetative B. anthracis
1) causes severe edema and tissue necrosis (causes decreased oxygen to advance spread)
2) kills WBCs so host camnot fight the infection
What are the clinical signs of anthrax
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
What is the treatment, prevention and control of anthrax
Vegetative form of anthrax: antibiotics
Vaccines
Control the spread of spores in environment
How do you control the spread of spores of anthrax in the environment
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
True or false
Anthrax is a reportable disease and must be reported to the CFIA
True
What is the purpose of tracking reportable diseases
To identify source of infection
To prevent spread
To track rate of spread
To ensure there is no risk of it entering canada
What are characteristics of reportable diseases
High mortality and/or morbidity Often no treatment High risk of transmission Economic importance Zoonosis Not currently in canada Emerging diseases
Describe Clostridium perfringens
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
Describe diagnosing C. perfringens diarrhea
Fecal smears , Swab of rectum or fecal sample
Diagnosis is by increased levels of typical large gram positive rods with or without spores
