Microbiology lab practical - Karen


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What types of microbes dominated environmental plates
Bacteria because they were round and shiny
Why is it important to use aseptic technique when inoculating tubes and media plates?
It's important bc aseptic technique prevents unwanted microorganisms from contaminating sterile materials and making changed to your outcome
How does the procedure from using low power and high dry power differ?
Low power lens and high power lens differ in magnification. While low power is useful when viewing slides, high powe shows much more detail
How does loss of light affect the resolution of a specimen
Loss of light decreases clarity and resolution of the image
What is the purpose of immersion oil
Immersion oil is used to increase the resolution of a microscope. It is used to retract the kinky beam in the correct direction instead of the side at an angle w/o it
What 2 things can be adjusted to control the amount of light passing into a specimen?
Condenser and light control
Describe how to properly care for a microscope after using immersion oil.
You must use isopropanol alcohol and lens paper to remove oil from microscope optics
Why must we stain bacteria before examining them with a microscope
We must stain bacteria before examining them with a microscope bc most bacteria lack natural pigmentation So cells are difficult to see w/o staining first
What component of a stain gives bacteria their color
Chromosphere (carries color)
What advantage does knowing the morphology and arrangement of a culture provide
Each bacterium is treated w/ different antibiotics and based in the cell morphology and arrangement observed under microscope magnification. A physician can use this info to diagnose infectious organisms and prescribe correct antibiotics
Why must you use water when preparing a smear for a solid culture
Using wager allows for better or smoother smearing of culture. It produced a more dilute, even density of the culture.
What is a differential stain?
Differential staining is a method used to distinguish between dif types of bacteria
How can the age of the cell culture affect the results if a gram stain?
As cells age, they lose their ability to retain stains. Aging makes cells appear gram negative even through it's not.
Which is the most critical step in gram staining procedure?
How can the result of a gram stain on a bacterial culture help a physician decide which antibiotic to use against the bacterium
If you know it's gram positive, you may prescribe penicillin which affects the formation of peptidoglycan
Gram stains are normally preliminary test.
Gram tests shouldn't be misinterpreted bc it can cause misdiagnosis
Can a bacteria cell produce more than one spore?
No. One cell, one endospores
Why is hear required to stain endospores
Heat allows the dye to penetrate the cell
What is the advantage to bacteria To produce endospores
Endospores are resistant to both physical and chemical agents so bacteria would be better protected
Can bacteria survive with a capsule?
Yes. Some bacterial are surrounded by gelatinous or slime layer
What are the advantages of a capsule to bacterial cell
Capsules make it difficult for phagocytes to ingest a bacterial cells
After preforming the acid fast stain, snag color is the cell lacking mycolic acid?
These would be non Acid fast and would be blue.
How does a layer of mycolic acid contribute to bacteria ability to cause disease?
Those cells w/mycolic acid are acid fast. Acid fast cells aren't consistent. The mycolic acid makes them more resistant to phagocytosis and the waxy lipid makes staining and examination more difficult.
When preforming a streak plate, why is it necessary to flame a loop between each streak pattern?
The purpose of a streak image is to isolate a pure culture. You must run the loop thru a flame in order to sterilize the loop between streaks. By sterilizing the loop, you destroy one bacteria on the loop and more likely to isolate a colony.
How can you confirm that your isolated coming came from a single type of cell?
By using streak plate method, you are able to drop a single slice lol at a time. This cell will divide and form a colony.
If you were asked to isolate bacteria from a water sample, which method would you use and why?
Spread because it's a liquid.
When preforming the spread plate technique, why is it important to burn off all the alcohol from the glass rod before spreading the bacteria?
Alcohol is used as a sterilizer. If it's not burned off, the rod isn't sterilized, also alcohol is an antiseptic that will prevent growth of bacteria.
What is a complex media?
Complex media contains a nutrient rich substance so precise chemical constituents are unknown
What is the goal of selective media?
Prevent or inhibit growth of most microbes while supporting growth of very few microbes
Besides MacConkey agar, what other media would be useful for isolating E.coli from a stool sample?
Eosin methylene blue agar
Explain why pH indicator can be useful when determining whether or not fermentation has occurred?
PH indicator allows the differentiation between organisms that ferment a substrate to acid versus those who are incapable of fermenting a compound
Why, in clinical laboratories, are selective differential mediums employed most often?
Selective differentiation allows for the growth of specific bacteria and you can differentiate between organisms. These are used in the lab bc they are quick and effective
Describe the minimal components that would be necessary in a medium designed to show a difference between an organism and ferments X to Y. X has neutral pH and Y is acidic
PH indicator, nutrients, substrate
Why is NaCl used to select for bacteria from the skin?
Bc NaCl inhibits organisms other than staphylococci. It's selective growth media. While encouraging the growth of some, it inhibits most others. pH indicator distinguishes mannitol-fermenting staph
What would you use to differentiate between staph and strep?
Morphology, gram stain, and catalase
What type of microbes where on skin?
Was there fungi on your skin
What is a good test to screen for strep throat ?
What gas is given off during positive test for catalase?
What type if bacteria did you recover from your nose?
What are nosocomial infections?
Hospital acquired infections
What type of bacteria cause nosocomial infections?
Staph, pseudomonas
Why are bacterial endospores more resistant to UV light than vegetative cells?
Endospores are non dividing cells. They have acid soluble proteins which are preventive to UV light. Endospores have a protective capsule
Would incineration or autoclaving be an effective form of control on metal objects?
Would incineration or autoclaving be an effective form of control on plastic materials?
How is culture media sterilized prior to use
Some chemicals may have produced a zone of inhibition on nutrient agar plate but not on BAP. What is explanation?
The presence of organic material may neutralize the effects of many antimicrobial materials. Lack of inhibition means resistance and some microorganisms were killed
Some chemicals nah have bad better e.coli and mess staph. What is the difference between the two that leads to these results?
E.coli is gram negative and has a thicker peptidoglycan wall than the gram positive staph
Bacillus may have survived treatment w/ chemicals better than staph or E. coli. What special structures may give it resistance?
Does filter laker efficacy testing method examine the effect of bacteriostatic agents, bacteriocidal agents, or both?
Both. The chemicals that the paper is dipped into can whether kill of inhibit the growth of the bacteria.
What is an antibiotic
A metabolic product that in small amounts is detrimental or inhibitory to microorganisms
Which antibiotic was most effective against the bacteria played?
Was each antibiotic effective against all strains of bacteria? Explain.
No. Some bacteria are resistant to certain antibiotics or have certain characteristics that allow then to grow regardless. Some were effected (sensitive) and some wernt (resistant)
Can antibiotics be used to treat viral infections?
No. Bacterial infections only.
Examples if nonspecific chemical defense agents?
Interferons, low pH, high salt
Why did you get did results w/ e.coli and micro occurs luteus in lysozyme experiment?
Micro occurs are gram positive and were lysed. E. coli are gram negative so they were unaffected
Examples of mechanical defense mechanisms
Cilia in mucus mem, skin epithelial keratin barrier, sneezing, urine flow
Any foreign substance that causes the body to produce antibodies or synthesize T cells
Protein made by B cells and plasma cells in reaction to foreign substance or antigen
Precipitation reaction
Fine, cloudy reaction, liquid in test tube, insoluble
On slide or test tube. Soluble
How can serological tests be used to verify the etiology of a disease
Organisms are identified at strain level
What type if activities are associated w/ antibodies "in vivo"
It's an experiment using the whole living organism such as animal testing
Which if the bacterial respiratory pathogens can you be immunized against?
Mycobacterium tuberculosis, corynebacterium diphtheria, streptococcus pneumonia, Hib
How could you distinguish between staph epidermis and staph aureus
Colony morphology, coagulate test, hemolytic or not, metabolic tests
What are the symptoms of acute epiglottitis
Trouble breathing, drooling, sore throat, change in voice, rapid and shallow breaths
What is sputum specimen
A sample of material expelled from the respiratory passage which is taken to the lab to determine the presence of pathogens. Mucus from lungs or trachea
Why are pure cultures necessary for biochemical testing??
Biochemical tests are done to correctly identify particular organism/ microbe. It's crucial to be pure bc if it's contaminated, results may be scewed
Why do you need to know the gram reaction and morphology of an organism before preforming biochemical testing
We must know the gram reactions So we can use the right test to identify the bacteria. we must know the morphology to understand the potential outcomes
Relate urease production to diaper rash in infants.
"Diaper dermatitis" is the scientific name. This irritant inflamed the skin. The combination if warm and moist environment is optimal for growth of the bacteria. The breakdown of urease in diaper rash changed the pH and irritates the skin
Metabolic process that converts sugar to acid, gas, or alcohol
Removal if an amine group from a molecule
Why is testing for enzymes a reliable identification tool
These tests measure enzyme activity which generally reflects the genetic capabilities of the cell which can lead to ID
Which of the enzymes you tested for would be considered exoenzyme
Urease, DNase, amylase
What are the symptoms of a pinworm infection
Itching if vaginal/anal area. Insomnia. Irritability. Abdominal pain. Naseau. Pinworms in stool
Which protozoan is particular concern during pregnancy
Toxoplasma Gondi
Describe the symptoms of a giardia infection? How is it contracted in urban setting
Symptoms: watery greasy stool, fatigue, belching w/bad taste, weightloss
This many come from swallowing giardia locked up from surfaces containing stool, drinking water from contaminated source, contact w/ I'll person
What are three morphological types of capsids found in viruses
Helical, polyhedral, complex
For what viral diseases are immunization available
Chicken pox, HPV, STI's, hepatitis
What are retroviruses and what are some diseases w/ this group
They are a family of envelopes viruses that replicate in a host thru reverse transcriptase. It produces host DNA thru reverse transcriptase RNA. AIDS and leukemia
What does opportunistic mean
Opportunistic refers to taking advantage of a situation. Microorganism that don't normally cause disease but becomes pathogenic when the body's immune system is impaired
What type of patient specimen would you collect for histoplasmosis
Describe some infections associated w/ candida also and
Skin and mucosal infections.
Yeast infection