Microbiology Lab #6 & 7 on Microbial Growth Questions

Rank these organisms in the most difficult to destroy or control to the easiest to control:

- Enveloped viruses (such as influenza virus) - Mycobacterium tuberculosis - Prions

You test four different antibiotics against a beta-hemolytic streptococcus. Based on these results, which drugs are possible options for treating an infection with this bacterial pathogen?

- Erythromycin - Gentamycin

In which circumstances would we attempt to optimize conditions for microbial growth?

- Manufacturing yogurt - Composting yard waste - Culturing a urine specimen to detect a urinary tract infection

Which statement best describes the growth patterns of microorganisms based on their temperature preferences?

A microorganism will grow across the range of temperatures tolerated by its enzymes.

Which the following is indicate of a drug sensitivity?

A zone of inhibition that falls under the sun set of column and a standard chart

In an anaerobe jar, oxygen is:

Absent

What conclusion can you draw by looking at these Kirby-Bauer results?

- Both of these organisms could be sensitive to SXT - The antibiotics tested here appear to be more effective against gram-positive organims

Which of the following are chemical means of microbial growth?

- Disinfectant - Antibiotics

Which of the following drugs would be a poor choice in treating an infection with Pseudomonas aeruginosa based on the results of this Kirby-Bauer test?

- Penicillin - Tetracycline - Vancomycin

Which classifications of organisms can be a concern for growth in refrigerated foods?

- Psychrophiles - Psychrotrophs

What factors influence the size of the zone of inhibition for an antibiotic?

- The growth rate or inhibition of growth of the bacteria in the presence of the antibiotic - The rate of diffusion of the antibiotic through the Mueller Hinton agar

What are possible outcomes of selecting an antibiotic that is ineffective to treat a particular infection?

- The targeted pathogen will continue to grow and cause disease - The normal microbiota may be destroyed enabling the targeted pathogen to grow even better - The infection may worsen

Which of the following organisms are expected to grow within an anaerobe jar?

- facultative anaerobes - obligate anaerobes - aerotolerant anaerobes

Which of the following are used to describe the range of temperature over which a microbe will grow?

- minimum growth temperature - optimum growth temperature - maximum growth temperature

Which organism(s) should be able to grow in the anaerobe jar?

- obligate anaerobe - facultative anaerobe

Which of the following are environmental factors that affect microbial growth?

- pH - nutrients - temperature - osmotic pressure - atmospheric gases

Which of these laboratory items are usually used to inhibit the growth of most types of microorganisms by altering their environment?

- salt plates - refrigerator

Which of the following are correct statements regarding this FTM tube?

- the bottom region represents an area where oxygen is absent - the top pink area has oxygen present

You inoculate a plate with two different organisms and incubate in an anaerobic jar for 24 hours. This is the result you see after incubation. Which of the following are possible conclusions regarding these organisms?

- they may be obligate anaerobes - they cannot be obligate aerobes - they can grow in the absence of oxygen - they may be facultative anaerobes, but that cannot be determined from theses results alone

Which of the following environmental conditions are preferred by a majority of organisms?

- warm temperatures - neutral pH - isotonic environments

Rank the following, from the highest growth temperature range (at the top) to the lowest growth temperature range (at the bottom):

1) extreme thermophile 2) thermophile 3) mesophile 4) psychrotroph 5) psychrophile

The zone of inhibition is:

21 mm

Which of the following would be used to provide the optimum growth temperature for microorganisms that typically grow in humans?

37 C incubator

Based on these results, what can you conclude about the susceptibility of these two organisms?

Both of these organisms are likely resistant to penicillin and erythromycin.

A drug that is effective against a large variety of bacterial types including gram positive, gram negative, intracellular pathogens, and bacterial without cell walls (Mycoplasmas) is a ______ antimicrobial.

Broad spectrum

A particular microbial control agent weakens and destroys peptidoglycan. This was specifically damage the ______.

Cell wall

Temperature above the maximum growth temperature for a microorganism are likely to result in:

Denaturation of enzymes

The slowed growth or lack of growth of an organism at temperatures of pH outside of its ideal range is most likely due to changes in its:

Enzymes - Since they are proteins & their activity is dependent on their three-dimensional structure which is affected by temperature and pH

A tube of fluid thioglycollate medium is inoculated with a bacterial isolate. After incubation the bacteria appear to be growing throughout the tube. This bacterial isolate is most likely an:

Facultative anaerobe

Based on this FTM tube result, how would you classify this organism?

Facultative anaerobe

Match the oxygen requirement classification with the correct description of the expected FTM tube result:

Facultative anaerobe = growth throughout the tube Obligate anaerobe = growth towards the bottom of the tube Obligate aerobe = growth towards the top of the tube

T/F = All microorganisms use oxygen in their metabolism.

False

T/F = The sources of all antimicrobial drugs are fungi and other microorganisms.

False

Your task is to determine the oxygen requirement classification for several organisms. Choose an appropriate strategy for this experiment:

Inoculate two plates with three organisms in separate areas. Place one plate on incubator shelf and one in the anaerobe jar for 24 hours and observe.

You inoculated the broths seen here with Staphylococcus epidermidis and incubated at the labeled temperatures. How would you classify this organism based on its growth at different temperatures?

Mesophile

Most human pathogens are classified as:

Mesophiles

What is the preferred medium for use with the Kirby-Bauer susceptibility test?

Mueller Hinton agar

Match each description with the appropriate category.

Obligate aerobe = uses oxygen in its energy metabolism; can process toxic oxygen by-products Obligate anaerobe = does not use gaseous oxygen in its energy metabolism; unable to process toxic oxygen by-products Facultative anaerobe = can conduct aerobic or anaerobic metabolism; can process toxic oxygen by-products Microaerophile = unable to grow in the presence of atmospheric levels of gaseous oxygen, but needs a small amount of oxygen for its metabolism

The data table shown here indicates the absorbance readings for broth inoculations incubated at different temperatures. Based on these readings, how would you classify this organism according to its temperature preferences?

Psychrophile

Based on results of a disk diffusion antimicrobial susceptibility test, an organism may be described as sensitive, intermediate, or resistant to the drug. Match the term with its description.

Sensitive = the growth of the microorganism is significantly inhibited by the drug Intermediate = the drug demonstrates moderate inhibition of the microorganism Resistant = the microorganism is not affected by the drug and can grow in its presence

Which of the following processes removes or destroys endospores?

Sterilization

A microorganism is classified as a psychrophile, a mesophile, or a thermophile based on its optimum growth:

Temperature

What is your hypothesis?

The organism will grow within a range of temperatures.

The area around an antibiotic disk where microorganisms are NOT growing is referred to as the ______ of ______.

Zone of inhibition

If comparing growth of a microbe in broth tubes incubated at different temperatures, the tube incubated at the organism's optimum temperature would:

be the most turbid (cloudy)