Biol 251 lab 10

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  1. Define and differentiate natural antibiotic, semi-synthetic antibiotic and synthetic antibiotic.
    • Natural antibiotic: fund in nature produced by bacteria or fungi
    • Semi-synthetic antibiotic: natural antibiotic that its R group has modified
  2. Differentiate broad and narrow spectrum antibiotics.  Provide advantages and disadvantages of
    each use in treating infections.
    • Broad spectrum: kill all bacteria. advantage no need to identify bacteria before treatment begins. disadvantage kill natural body flora.
    • Narrow spectrum: kill one or few types of bacteria. Dis advantage: identification require before treatment starts.Advantage: does not kill natural body flora.
  3. Explain selective toxicity.
    Drugs that target bacteria cells and not human cells.
  4. What is a standardized test?   Name 5 standardized variables for the Kirby Bauer test.
    • Kirby-Bauer method to test susceptibility/resistance of bacteria to different antibiotics.
    • Mueler-Hinton agar II: pH 7.2-7.4, 4 mm thick
    • Bacteria must be grown to density of 107 cells/mL. Spread using lawn technique.
    • Plates incubate 16-18 hours.
    • Discs same amount of antibiotics. labled
    • Zone of inhibition measured in mm
  5. Were any antibiotics used in this lab narrow spectrum?  If so, name them and state their action.
    • Yes:
    • oxacillin: β-lactam cell wall inhibitor
    • Tetracyclin: Protein inhibitor
    • Vancomycin: cell wall inhibitor (non-β-lactam)
    • Clindamycin:protein inhibitor (50S)
  6. Were any antibiotics used broad spectrum?  If so, name 2 of them and state their action.  Did they
    work similarly on both Gram positive and Gram negative?
    • Ciprofloxacin: DNA inhibitor
    • Amikacin: Aminoglycoside

  7. State factors that influence the size of the zone of inhibition for an antibiotic?  What type of error
    could result for factors not controlled in this test.
    • Not following the standard variables of Kirby-Bauer method
    • Not using lawn technique
    • not incubate the agar plate between 16-18 hours
    • Not using the same amount of antibiotic in each disc
  8. Define and list characteristics of coliforms.  Why is water tested for coliforms?
    • enterobacteriaceae members
    • facultative anaerobic
    • Gram negative rods
    • ferment lactose
    • produce gas

    Because they cause gastrointestinal infections such as cholera and dysentery
  9. Name two bacterial pathogens, one viral pathogen, and two protozoan pathogens that
    may be found in water.
    • Bacteria: E. coli & Vibrio cholerae
    • Protozoan: Giardia & Cryptospordium
    • Virus: Norovirus
  10. Explain the selective and differential aspects of the media used. (coliforms test)
    • The media select the growth of gram negative and inhibit gram positive
    • It differentiate between lactose fermenters (coliforms) to other gram negative bacteria.
  11. Describe the appearance
    of E. coli on each media and describe the appearance of Salmonella on each media.
    • MacConkey Agar: E. coli ferment lactose and agar turn pink. salmonella did not ferment lactose agar color stayed yellow
    • Eosin Methylin Blue Agar: E. coli ferment lactose = metallic green stripes. Salmonella did not fermented lactose clear stripes  
    • Hekton Enteric Agar: E. coli ferment lactose agar turn orange. salmonella produce H2S = black but did not ferment lactose = green.
  12. Gram positive coccus possible clusters
    Which bacteria is positive in catalase test
    • Staphylococcus
    • Micrococcus
  13. Gram positive coccus possible clusters
    Which bacteria is negative in catalase test
    • Enterococcus or streptococcus
    • (gram + in chain)
  14. Gram positive coccus possible clusters
    Which bacteria is positive in mannitol salt fermentation?
    • Staphylococcus Aureus
    • Staphylococcus Saprophyticus
  15. Gram positive coccus possible clusters
    Which bacteria is negative in mannitol salt fermentation?
    Staphylococcus Epidermidis
  16. Gram positive coccus possible clusters
    Which bacteria is positive in β hemolysis on blood agar?
    Staphylococcus Aureus (produced cagulase)
  17. Describe one biochemical test to differentiate Staphylococcus from Enterococcus.
    • Catalase test:
    • Staphylococcus is positive for catalase that broke down oxygen radicals.
    • Enterococcus is negative for catalase could not break down oxygen radicals
  18. Explain two biochemical tests for differentiating S. aureus from S. epidermidis.
    • Mannitol salt fermentation
    • S. Aureus fermented mannitol
    • S. Epidermis did not ferment mannitol
    • Coagulase test S. aureus(+) and  S. epidermidis (-)
  19. Why is it important to differentiate S. aureus from S. epidermidis and S. saprophyticus?
    • They all associate with different types of infections.
    • S. aureus: produces coagulase (cause plasma clot) and it's cause β hemolysis.
    • S. epidermidis: Associate with hospital blood stream infection, coagulase negative, and non-hemolytic
    • S. sapophyticus: associate with urinary tract infection, non-hemolytic, and coagulase negative
  20. If Staphylococcus aureus is identified in a clinical specimen, what other important test should be
    • Coagulase test
    • Hemolysis test
  21. Discuss the role of S. aureus as a cause of opportunistic infections and as a cause of nosocomial infections.(hospital acquired infections)
    • S. aureus may be a resident (normal flora)of the of human skin and mucus membrane.
    • It is opportunist because it can be pathogenic if it is given the opportunity
    • In hospitals, S. aureus may gain virulence factors and resistant genes that may cause abscess, endocarditis, toxic sock syndrome, or pneumonia and MRSA.
  22. communicable
    Disease that spreads from one person to another
  23. Not communicable
    • Disease that not spread from person to person.
    • Graph is tall and narrow
  24. Define and differentiate a point source (common source) epidemic and propagated epidemic.
    • Point source (common source) epidemic: happen in one geographical place for short period of time. Graph is tall and narrow
    • Propagated epidemic: The outbreak is communicable and it's geographically spread and it no longer considered point source.
  25. State microorganisms causing pandemics that are occurring now or have recently occurred.   Why
    are they pandemics?
    • H1N1 and HIV AIDS
    • They are communicable carried and spread from person to person between continents.
  26. transient flora (in the skin)
    • Temporary micobiota in skin
    • Obtained via nosocomial infection
    • S. aureus resistant to methicillin (MRSA)
    • Enterococcus resistant to vancomycin (VRE) spores
    • Clostridium difficile (C. diff) spread through spores.
  27. Resident flora of the skin
    • microbiota that always present in the layers of the kin.
    • Staphylococcus:
    • S. epidermidis
    • S. aureus


    • Propinobacterium (anaerobic live in sebaceous glands)
  28. Nosocomial infection
    Infection that occur in medical setting
  29. Name opportunistic pathogen (s) normally associated with the skin.
    • Staphylococcus aureus
    • Staphylococcus epidemidis
  30. What type of soap did you use (germicidal or non-germicidal)?    Do you expect a difference
    between these two types of soap?  Explain.
    • We used non-germicidal soap
    • Yes, germicidal will remove more bacteria from the hands then non-germicidal soap
  31. List three professions where lack of handwashing could lead to infectious disease outbreaks.
    • Health care workers
    • Food handlers
    • People who work with the general public
  32. Why do surgeons still have to wear gloves even after they have scrubbed their hands prior to
    Even though they wash/scrub their hands with germicidal soap, they have to wear gloves because this process does not achieve sterility.
Card Set
Biol 251 lab 10
Lab 10
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