MICROBIO PRACTICUM 2

• Where is Staph. Aureus commonly found?

  Nasal passages
• What diseases does Staph. Aureus cause?

  Toxic shock syndrome, bacteremia, pneumonia, endocarditis, osteomyelitis
• What enzyme does Staph. aureus have that increases its virulence?

  Coagulase
• What disease does Staph. epidermidis cause?

  Catheter induced UTIs, septicemia, endocarditis
• Staph. epidermidis is a ______

  true pathogen
• What is an enriched media?

  Media containing additional nutrients or growth factors to support the growth of fastidious organisms.
• what is a selective media?


  Media that allows the growth of certain types of microorganisms while inhibiting the growth of others.
• What is differential media?

  Media that allows for the differentiation of different types of microorganisms based on their growth characteristics.
• What tests can be used to differentiate staph species?

  MSA, Blood agar plate (hemolysis), and coagulase test
• which staph species is able to form a slime layer?

  Staphylococcus epidermidis
• What type of test is the MSA test?

  used to differentiate staph species

  -Selective for salt tolerance

  -Differential: mannitol fermenters turn pH indicator
• What can we add to a media to make it more selective for staph aureus?

  6.5% salt
• what can we add to media to make it differential for staph. aureus?

  Mannitol
• Interpret the results for the following plate

  -This is an MSA plate

  -The left organism is salt tolerant and can ferment mannitol as indicated by the yellow color indicating a pH change

  -The right side is salt tolerant but not a mannitol fermenter because there was no color change but there was growth

  
• What would we expect to see on a MSA plate for staph. aureus?

  Yellow colonies
• what would we expect to see on a MSA plate for staph. epidermidis?

  no color change because they are not mannitol fermenters
• what is a fastidious organism?

  Organism that requires specific conditions for growth
• Describe the purpose of a Blood agar plate

  The purpose of this test is to see if the organism has the exotoxin hemolysin which is an enzyme that destroys erythrocytes and hemoglobin to release Iron
• What is the purpose of enzyme hemolysin

  enzyme that destroys erythrocytes and hemoglobin resulting in the release of iron for bacterial usage
• What type of media is a blood agar plate?

  enriched: contains blood cells

  differential: different patterns depending on the presence or absence of exotoxin hemolysin
• Describe the different patterns of hemolysis

  Beta: complete hemolysis characterized by a clear zone surrounding colonies

  Alpha: partial hemolysis of RBCs leaving colonies surrounded by a green, opaque zone
• How do we describe no pattern of hemolysis

  gamma hemolysis aka no hemolysis
• which organism is gamma hemolytic

  staph. epidermidis
• why do we streak and stab a blood agar plate?

  Bacteria that are on the surface might perform differently when in anaerobic conditions such as when in a deep wound
• Interpret the results of the following plates

  -The plate to the far left is beta hemolysis because we see a clearing around the colonies indicating that the erythrocytes have been destroyed

  -The plate in the middle is alpha hemolysis because The colony appears to be green and opaque indicating that erythrocytes were partially destroyed

  -The plate to the far right is gamma hemolysis because there is no change in color or opacity indicating that erythrocytes were not destroyed

  
• What is the purpose of a coagulase test?

  Detects the presence of coagulase enzyme in bacteria
• what does the enzyme coagulase do?


  it allows bacteria to form clots using fibrin in the blood plasma
• How does coagulase aid bacteria in pathogenicity?

  Coagulase aids bacteria in pathogenicity by causing blood clotting, which helps the bacteria evade the host immune response, resist phagocytosis, and some antimicrobial agents
• what type of bacteria is a coagulase test used for?

  gram + to identify staph. aureus
• Which species of staph is the only coagulase positive one?

  Staphylococcus aureus
• What is a nosocomial infection


  an infection that is acquired while going to receive services in a healthcare facility
• Who discovered that penicillin was produced by penicillium?

  Alexander Fleming
• What is an antimicrobial drug?


  a drug that interferes with the growth of microbes within a host
• what is an antibiotic?

  a substance produced by a microbe that, in small amounts, inhibits another microbe
• what is a bactericidal agent?


  used to kill microbes directly
• what is a bacteriostatic agent?

  Inhibits growth of bacteria.
• What are the different actions of antimicrobial drugs?

  -inhibition of cell wall synthesis

  -inhibition of protein synthesis

  -inhibition of nucleic acid synthesis

  -injury to plasma membrane

  -inhibition of metabolic processes
• what are the different mechanisms of antibiotic resistance?

  -enzymatic destruction of drug

  -prevention of penetration of drug

  -alteration of drug’s target site

  -rapid ejection of drug
• What is the purpose of performing a PYR test?

  To identify bacteria that can hydrolyze pyrrolidonyl-beta-naphthylamide (PYR) using enzyme PYRase.

  -identification of Strep A and Enterococci
• How do you know if an organism is PYR positive?

  A cherry red color after adding color developer