Laboratory Methods

Question 1

What is direct diagnosis

Answer 1

direct diagnosis? when it provides the diagnosis of the disease or condition by itself or when it provides decisive information for the diagnosis.

Question 2

What is the importance of laboratory diagnosis of infectious diseases

Answer 2

1. It is needed in the treatment of infection
2. It improves the effectiveness of treatment ( monitoring patients reactions the the treatment)
3. Early diagnosis helots to stop or prevent th spread of the infection . Example: if you’re sick and instead of going to the hospital for the doctor to diagnose the disease , you stay home and treat your disease it may get out of hand and worsen. Also if the disease you have is contagious and other people contract that disease, the disease will keep spreading.

Question 3

What are the main organisms that cause infection

Answer 3

Bacteria- Cholera( Vibrio Cholerae, Tuberculosis (mycobacterium tuberculosis),syphilis( Treponema pallidum )
Fungi- candidiasis(candida albicans ), athlete’s foot, ringworm
Virus- AIDS(HIV), common cold(rhinovirus),influenza(influenza virus, H1N1)
Helminths(worms)- hookworm infection, schistosomiasis
Protozoa -malaria(plasmodium parasite),trypanosomiasis (trypanosoma brucei), amoebic dysentery ( entamoeba histolytica

Question 4

What re the Methods of lab diagnosis

Answer 4

Direct method: detects the pathogen or the structural components of the pathogen (example DNA or RNA)
Examples: microscopy, culture,molecular test

Indirect: it shows a reaction that has occurred due to the infection or due to the presence of the pathogen in you body. It only shows positive or negative. ExMple: serological method,imaging, X-ray, CT scan, Ultrasound

Question 5

Microscopy can detect all the five groups of pathogens. True or false

Answer 5

True

Question 6

Name four Types of microscope , how they work and three merits and demerits of each.

Answer 6

Brightfield or light microscope: Examines stained and unstained specimen. Specimen appears dark in a white or bright background.

Merits: easy to use, not expensive to buy and maintain, Very specific( helps you see a specific pathogen), portable
Demerits: Time consuming, low resolution, low sensitivity especially when the pathogen load is low( sensitivity is the ability of a test to correctly identify all the true positive patients). If it’s high then the test will identify all the positive patients if it’s low test will be able to identify few of the positive patients.

Dark field microscope: Observes specimen that are unstained. It views live pathogen if present in the sample. Pathogens appear bright in a dark background.
Merits:
Demerits:

Fluorescent microscope: Intensity of the light source is high. This excites the molecules of the fluorescent dye used to stain the specimen, emitting light from the pathogen of it is present. Mainly used in research labs.
Merits
Demerits

Electron microscope: Uses beam of electron to create an image. It has high resolution to detect extremely small sized pathogens. It’s mainly used to examine viruses because of this.
Merits
Demerits

Question 7

Types of preparation

Answer 7

Stained- uses dye
Unstained - doesn’t ( examples, urine is put on slide and covered, shit is put on slide and normal saline is added to it then it is covered

Question 8

Types of stains

Answer 8

Simple stains: one color is used. Examples- iodine, methylene blue

Differential stains: two or more stains in staining procedure. ExMple, Gram staining

fluorescent stains( best used for mycobacterium species)

Question 9

When are concentration methods used

Answer 9

When parasitic infection is suspected

Question 10

Types of concentration methods

Answer 10

A.Sedimentation - example( if urine is centrifuged,the sediment is observed)

1. Simple sedimentation-only
2. Formalin ethyl centrifugation- formalin preserves pathogen there , then ethyl is added.

Microscopy observes how specimen looks. It’s collie and all

B.Floatation- NaCl or zinc sulphate are the reagents used. When centrifuged, pathogens appear at the upper portion. Upper portion is taken and lower portion is discarded

Question 11

Types of substrate for culture

Answer 11

1. Culture media(artificial media)(contains all necessary nutrients needed for pathogen to grow and is created in the laboratory )(viruses can’t grow in this media)
2. Living eukaryotic cell examples viruses, some bacteria need living cells to grow (intracellular pathogens), some Protozoa example toxoplasma

Question 12

Types of culture

Answer 12

1. Blood culture
2. Urine culture
3. Stool culture
   Sputum culture

Question 13

Merits and demerits of culture

Answer 13

Very good sensitivity

Demerit- requires longer time to get results

Question 14

Explain molecular method and the principle it works on and it’s merits and demerits

Answer 14

Detects nucleic acid of the pathogen. Works on the method of PCR- polymerase chain reaction ( makes many copies of the DNA or RNA using different temperatures or temperature cycles)

Demerits- expensive and requires training
Merits- useful for fastidious pathogens ( pathogens that are difficult to culture in the lab), doesn’t need many samples, even one sample is okay

Question 15

Serology detects what and what

Answer 15

Antigen in the body and the antibodies induced by the antigen

Question 16

What is sterilization

Answer 16

It is the complete removal of viable pathogenic microbes using physical or chemical methods

Question 17

Merits and demerits of serological methods

Answer 17

Easy to use
Not expensive

Demerits: can produce a negative result if the time the body takes to develop antibodies in response to the antigen is long

Question 18

ELISA stands for

Answer 18

Enzyme linked immunoassay

Question 19

What is disinfection

Answer 19

Process of killing microbes with the exception of spore forming bacteria on inanimate surfaces. Biocides or disinfectants are used
If disinfectant is effective against spores it’s called- spirocides
If it’s effective against bacteria it’s called biocide

Question 20

Define antiseptics and the term aseptic

Answer 20

Biocide used to destroy microbes on or in living tissues.

Aseptic means the absence of pathogens in or on living tissues

Question 21

Methods of sterilization are groups into two, name them

Answer 21

Physical and chemical methods

Question 22

Physical method of sterilization is divided into three name them

Answer 22

Heat method ( dry heat method( hot air oven( forceps , scissors, glassware, slides,test tubes) are put in there is used and is heated to 180degrees Celsius for two hours. Bunsen burner and incineration is also used ) and moist heat method(boiling the instruments 100 degrees for 10 mins or more)

Radiation method( non ionizing and ionizing method)

Filtration

Question 23

What is tyndallization

Answer 23

It targets spore forming pathogens or pathogens that were not killed by simple boiling. Items are boiled for three consecutive days

Boil and cool and boil and cool and boil and cool.

Question 24

What is pasteurization

Answer 24

Mild heat is applied to

Most food and beverages. 62 degrees Celsius for thirty minutes

Question 25

What is the principle auto claving is founded on

Answer 25

Steam under pressure for 121 degrees , 15 mins, 151bs | For surgical instruments, culture media

Question 26

How to be sure if sterilizing successful

Answer 26

Bowie and Dick tape is used. If sterilization was successful, there’ll be a color change

Question 27

What is non ionizing radiation

Answer 27

Example- UV light. | Low energy is used so more time is taken to break the bonds

Question 28

What is ionizing radiation

Answer 28

Energy is so high | ExMple X ray

Question 29

What is filtration

Answer 29

Removal of microbes from liquids. Polyester can be used as well as candles in filter containers

Question 30

What is used in Chemical sterilization

Answer 30

Alcohol can be used as a disinfectant and an antiseptic It exhibits rapid and broad spectrum anti microbial activity Example ethanol Optimum results are achieved when the 70 percent is used

Question 31

Aldehyde is used as

Answer 31

Disinfectant

Question 32

Formaldehyde function

Answer 32

storing tissues

Question 33

Halogen releasing agents examples

Answer 33

Iodine, household bleach, chlorine for water treatment

Question 34

Hydrogen peroxide is used as only antiseptic. True or false

Answer 34

False. It’s used as both disinfectant and antiseptic. | It inhibits bacterial fatty acid synthesis.

Question 35

Name some | Modes of action of disinfectants and antiseptic

Answer 35

Disrupt cells membrane or cell wall Damage DNA Denature proteins

Question 36

Factors that affect the effectiveness of a chemical agent

Answer 36

1. The concentration of the disinfectant and antiseptic:High or low concentrations of these chemicals affect it’s ability to produce the desired result which is destroying the microbes it comes into contact with. For a chemical agent to be effective, the concentration must be high enough to kill the microbes it comes into contact with. If the concentration is low, the chemical agent will not be able to kill the microbes thus rendering it ineffective. 2. Temperature at which the disinfectant and antiseptic is used:High or low temperatures affect the way chemical agents work. The chemical agents have optimal temperatures at which their activity increases thereby making them effective. When the temperature of the disinfectant and antiseptic increase too much it weakens its activity. When the temperature is decreased, the chemical agent’s activity decreases 3. Number of microorganisms present on the material : When the number of microorganisms is large, more time and more of the chemical agent is needed to remove all the microorganisms. When the number of microorganisms is large and the concentration of the agent is low , the effectiveness of the disinfectant and antiseptic reduces. 4. Nature of the material bearing the microorganisms: The material should be free of dirt and anything that can interfere with the activity of the disinfectant and antiseptic. If the material has dirt on it and the dirt interferes with the activity of the chemical agent, the chemical agent’s effectiveness reduces. 5. The kind of microorganisms present:Disinfectants destroy microbes with the exception of spore forming microorganisms. These spore forming microorganisms are difficult to handle. If the kind of microorganisms on the material are spore forming microorganisms and a disinfectant or antiseptic comes into contact with it, it may not be able to remove the spore forming microorganisms thus rendering the chemical agents ineffective .

Question 37

Why is 70percent alcohol used and not 100 percent

Answer 37

70% percent of alcohol is ideal to a stronger solution. Pure alcohol coagulates protein in contact. Suppose the pure alcohol is poured over a single celled organism. The alcohol will go through the cell wall of the organism in all direction, coagulating the protein just inside the cell wall. The ring of the coagulated protein would then stop the alcohol from penetrating farther from the cell, and no more coagulation would take place. At this time the cell would become inactive but not dead. Under the favorable conditions the cell would then begin to function. If 70 percent of alcohol is poured to a single celled organism, the diluted alcohol also coagulates the protein, but at a slower rate, so that it penetrates all the way through the cell before coagulation can block it. Then the entire cell is coagulated and the organism dies.

Question 38

Merits and demerits of dark field microscope

Answer 38

Easy to use or simple and effective techniques Quality of images obtained are very high Well suited for uses involving live and instained biological samples Demerits Dark field needs an intense amount of light to work. This intense light can create glare and distortion. Therefore, dark field does not create reliable specimen measurements. 2. Dark field is sensitive to contaminants. The sample must be very strongly illuminated, which can cause damage to the sample 3. Specimens which are not thin enough are prone to degradation and distortion

Question 39

Merits and demerits of electron microscopy

Answer 39

``` High cost High maintenance Not portable due to its large size Needs high level of expertise Can’t analyze live specimen ``` Merits High resolution High quality images

Question 40

Merits and demerits of fluorescent microscope

Answer 40

Very specific High sensitivity Different molecules can now be stained with different colors, allowing multiple types of the molecule to be tracked simultaneously. Demerits Photo bleaching Cells are susceptible to phototoxicity, particularly with short-wavelength light.

Question 41

Explanation of tyndallization

Answer 41

substance to boiling point (or just a little below boiling point) and holding it there for 15 minutes, three days in succession. After each heating, the resting period will allow spores that have survived to germinate into bacterial cells; these cells will be killed by the next day's heating. During the resting periods the substance being sterilized is kept in a moist environment at a warm room temperature, conducive to germination of the spores. When the environment is favourable for bacteria, it is conducive to the germination of cells from spores, and spores do not form from cells in th

Question 42

Importance of the aura mine phenol stain

Answer 42

Auramine phenol stain is a stain used in clinical microbiology and histology to identify tuberculosis mycobacteria

Question 43

Surgical instruments and culture media are usually sterilized by

Answer 43

Steam under pressure or autoclaving

Question 44

Glassware such as Petri dishes etc are sterilized using what method

Answer 44

Hot air oven method

Question 45

Inoculating needles or loops are sterilized using

Answer 45

Naked flame

Question 46

If there is fluid in the lung

Answer 46

There will be a change in colour in the x ray MRI doesn’t use radiation. It uses magnetic field and for soft tissues CT scan uses ionizing radiation. Usually for bones or bony tissues and for seeing things in segments