Microbiology Flashcards
Produce disease in the tissue it infects
Pathogens
Exist without producing disease
Non-pathogen
Can either exist as a pathogen or non-pathogen depending on concentration, environment or nutrient supply
Opportunitistic pathogen
Examples of opportunistic pathogens
Bacteria in GI tract, Yeast infection
Number of microorganisms needed to cause disease
Infective dose
Some organisms have the type of tissue preferred to infect (if it does not come into contact with specific tissue will not cause disease)
Tissue Affinity
Pathogens that need to enter the body through defined route to produce disease
Portal of entry
Example of tissue affinity
Rabies
Example of portal of entry disease
Clostridium tetani
Gram negative bacteria within the cell and are excreted when the cell dies
Endotoxins
Immunizing agents in vaccines; good antigen, excreted from bacteria into the surrounding medium or tissues
Exotoxins
Basic unit of measurement for bacterial cells
Micrometer or micron (u)
Intracellular bodies that are resistant to heat, chemicals, and radiation
Endospores
Stain used primarily to detect Mycobacterium and Nocardia species
Acid-fast stain
Example of basic nutrient media/Enriched media
Blood Agar
3 types of hemolysis seen on blood agar cultures
Alpha, Beta, Gamma
Greenish zone around colony
Alpha hemolysis on blood agar
Clear zone around colony
Beta hemolysis on blood agar culture
No zone around colony
Gamma hemolysis on blood agar culture
Media that contain substances that allow growth of one group of organisms and not others
Selective Media
Example of selective media
MacConkey Agar
Media that only show gram negative bacteria growth, can identify lactose-fermenting organisms as pinkish red
MacConkey Agar
Media that display visible differences caused by growth of specific colonies
Differential media
Examples of differential media
Simmons Citrate
TSI (Triple Sugar Iron)
Urea
Examples of Enriched media
Thoglycollate Broth
Tripticase soy
Liquid media that favor growth of a particular group of organisms
Enriched media
Used to grow anaerobic bacteria to determine the oxygen tolerance of microbes
Thioglycollate broth
Used to culture for antibiotic susceptibility testing
Tripticase soy
What is the goal of streaking culture plates?
To isolate the bacterial colonies
What is the catalase test used for?
To differentiate Staphs, Streps, and Coliforms
What is the Coagulase test used for?
To tell Staph aureus from environmental staphs
What is the CAMP test used for?
To determine environmental strephs from strep agalactiae
What are two causes of mastitis?
Bacterial or mycotic organisms
What are 3 lab tests that can be used to diagnose mastitis?
CMT, somatic cell count, milk culture
How does the CMT test work?
Based on gel formation when the test reagent reacts with DNA in somatic cells
What are two common contagious pathogens in milk?
Staphylococcus aureus
Streptococcus agalactiae
Common pathogens found in milk
Environmental staph/strep, E. coli, Klebsiella
Pathogens found in milk that aren’t as common
Yeast
Prototheca
Mycoplasma bovis (Contagious)
Where is environmental staph found?
On skin and occasionally bedding materials
How do cows get environmental staph?
Via poor milking techniques or dirty bedding
*Not spread cow to cow*
How does Environmental Staph appear on blood agar?
usually gray/white color, usually no hemolysis
Environmental Staph catalase/coagulase testing results
Catalase positive
Coagulase negative
Where is Staphylococcus aureus found?
On infected udder and dirty bedding
How is S. aureus spread?
Via poor milking technique or milking equipment
*Spread cow to cow!*
How does S. aureus appear on blood agar?
Gray/white color, double zone of beta hemolysis
S. aureus catalase/coagulase testing results
Catalse positive
Coagulase positive
Gram stain results for S. aureus
Gram positive cocci clusters
How are cows infected with environmental strep?
From wet/dirty bedding, milking wet cows
*Not spread cow to cow*