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