Microbiology Quiz 3
What is Resazurin and what do the colors mean
It's an indicator Pink when oxidized Colorless when reduced
Penicillin abx
Produced by mold Penicillium notatum
Use-Dilution test
Publishes by the Association of Official Analytical Chemists (AOAC) It's a standard procedure. If prevents growth at 95% of the time, it meets the standards Measures effectiveness of disinfectants, specifically against Staphylococcus aureus, Salmonella enterica serovar Cholerasuis, and Pseudomonas aeruginosa
Obligate (strict) aerobe
Require oxygen for respiration Grow at the top where oxygen is most plentiful
Anaerobic jar results
S. epi Grew little on aerobic plate. Grew little on anaerobic plate It's facultative Clostridium sporagenes Did not grow on aerobic plate. Grew little on anaerobic plate It's mostly strict aerobe A. Faecalis Gre on aerobic plate. Did not grow on anaerobic plate It's anaerobic
Abx. Ciprofloxacin
Cellular Target: Interferes with DNA replication Resistance Mechanism: 1. Altered target 2. Poor uptake of drug
Abx. Chloramphenicol
Cellular Target: Prevents peptide bond formation during translation Resistance Mechanism: 1. Poor uptake 2. Inactivation of drug
Components required for anaerobic growth
Chemical gas generator packet envelope containing sodium borohydride and sodium bicarbonate Paper indicator strip saturated with methylene blue Palladium
Why is methylene blue used?
It confirms the absence of oxygen If reduced, will be colorless If it's blue it'll be oxidized
Fluid Thioglycollate Medium
It's a reducing agent. Reduces oxygen into water so we can grow anaerobic bacteria It's a medium to test the aero tolerance of bacteria
Why are most media sterilized in an autoclave during preparation?
Kill unwanted microbes Remove most of the free oxygen from the medium as well When medium removed from autoclave and cools down, oxygen begins to diffuse back in Creates a gradient of oxygen concentrations from aerobic to anaerobic
Disinfectants
Germicides designed for use on surfaces (floors, tables, sinks, countertops, etc) Ex. Lysol, and bleach
Aerotolerant anaerobe culture
Clostridium sporogenes
Facultative anaerobe
Staphylococcus epidermidis
Which of the three organisms would be most negatively affected by the conditions described in question 1?
...
Capnophiles
A type of microaerophile Can only survive if carbon dioxide levels are high
Kirby-Bauer test
AKA Disk diffusion Measures effectiveness of antimicrobics against pathogenic microorganisms
Aerotolerance
Ability / Inability to live in the presence of oxygen
Aerobic culture
Alcaligenes faecalis
Mesophiles
Bacteria adapted to temperatures between 15 degrees and 45 degrees Minimal: 15 Maximal: 45 Optimal: 37 Most bacterial residents in the human body as well as numerous human pathogens
Extreme thermophiles
Bacteria isolated from hot ocean floor ridges living between 65 and 110 degrees Celsius Grow best above 80 degrees Celcius
Abx. Penicillin
Cellular Target: Inhibits cross-linking of the cell wall's peptidoglycan Resistance Medium: ~~one of more of~~ 1. Altered target 2. Poor uptake of drug 3. Production of beta-lactamases
Abx. Trimethoprim
Cellular Target: Inhibits purine and pyrimidine synthesis Resistance Medium: 1. Altered target
Bacteriostatic
Drug may stop bacterial growth without killing them
Results of Disinfectants/Antiseptics
E. coli is more resistant to Hydrogen Peroxide because it has super oxide dismutase E. coli has enzymes to break down hydrogen peroxide toxins
If, after incubation, you observed that the methylene blue indication strip inside the jar was blue, what would you guess the internal environment to be - aerobic or anaerobic? How would you expect the growth on the plate inside the jar to differ from the plate incubated outside the jar?
Environment would be aerobic. Growth would be similar inside and outside Blue strip means it has been oxidized and the environment would be aerobic the growth on the inside of jar and outside of jar would be similar
Culture temperatures
Escherichia coli: Mesophile Serratia marcescens: Mesophile Geobacillus stearothermohilus: Thermophile (optimal @ 55) Pseudomonas fluorescens: Psychotroph
What happens after inoculated media are placed inside the jar?
Gas generator envelope is opened along with the strip. Water is added an the jar lid immediately is fastened down. Sodium borohydride and sodium bicarbonate react with the water to produce hydroge nand carbon dioxide gases Palladium catalyzes a reaction between the hydrogen and free oxygen in the jar to reduce water Removal of free oxygen produces anaerobic conditions in the jar within approximately an hour as evidenced by a white indicator strip and moisture on the inside of the jar.
Antiseptics
Germicides designed for use on or in living tissue Ex. Hydrogen peroxide and Isopropyl alcohol
Facultative thermophiles
Grow below 40 degrees
Psychrophiles
Grow only below 20 degrees Common in ocean, Arctic / Antarctic habitants where temperature remains permanently cold with little or no fluctuation
Facultative anaerobe
Grow with/without oxygen Prefer oxygen but do not need it Most of the growth is on top
Oxygen
Important resource influencing microbial growth
What does Palladium do?
It acts as a catalyst for the reaction that will produce the necessary conditions inside the jar
Obligate thermophiles
Thermophiles that will not grow at temperatures below 40 degrees
An alternative to the anaerobic jar is a candle jar, in which a candle is placed in the jar, lit, and the lid closed to enable the flame to use the available oxygen. Typically, in this system, not all of the oxygen is used. Which types of organisms would most likely benefit from this environment?
Microaerophiles and aerotolerant facultative
Cardinal temperatures
Minimum / maximum: Temperatures below and above which the organism will not survive Optimum temperature: Temperature at which organism shows the greatest growth over time. Its highest growth rate
Antibiotics
Natural antimicrobial agents produced by microorganisms
Psychrotrophs
Organisms adapted to cold habitats that fluctuate from about 0 to above 30 degrees Celcius
Termophiles
Organisms adapted to temperatures above 40 degrees Celsius Tipically found in composting organic material and in hot springs
Gaspak Anaerobic System by BBL
Plastic jar Used in the production of an anaerobic environment
Why is Agar included in the Fluid Thioglycollate Medium?
To slow oxygen diffusion and stabilize growth
Aerotolerant anaerobes
Will always do fermentation 100% Do not require oxygen and are not affected by it They grow evenly throughout tube
Obligate (strict) anaerobe
Will die if Oxygen is present Will be seen at the bottom of the tube
Microaerophiles
Will grow under surface They require oxygen at a low atmospheric concentration
What are the components of Fluid Thioglycollate Medium?
Yeast extract Pancreatic digest of casein Dextrose Sodium chloride Sodium thioglycollate L-cysteine reduce oxygen to water Agar Resazurin DI water
Bactericidal
Zone of inhibition produced as a result of killing the bacteria
Mueller-Hinton Agar
pH between 7.2 - 7.4 Allows diffusion of antibiotic into agar Is poured to a depth of 4mm in 150/100mm petri dishes
