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Micro MLAB122 check 121 for lecture 4 > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

Endemics:

A

Infections normally present in a given region e.g cholera is endemic in India,rabies in Ontario

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2
Q

Epidemic

A

Serious infections affecting a larger than normal number of population

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3
Q

Pandemic

A

are world-wide epidemics-H1N1 viral influenza,Ebola infections

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4
Q

Acute infections

A

Rapid onset may be milder or serious and are of shorter duration.-influenza,food poisoning

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5
Q

Chronic infection:

A

have a slower onset and are usually of long duration. eg.TB,syphilis AIDS

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6
Q

Local infection:

A

are confined to a small area of the body

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7
Q

Systemic infections:

A

spread throughout the body by blood of lymphatics to affect many parts.

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8
Q

Primary Infections

A

are the first in a series of infections-usually local and acute

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9
Q

Secondary infections-

A

are those which occur as a result of weakness or increased susceptibility which may result from a primary infection

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10
Q

Infectious disease:

A

require that microbes or their toxins enter the body

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11
Q

Communicable Disease

A

are infectious disease which can be transmitted from one host to the other e.g STD’s TB,AIDS,Hepatitis

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12
Q

Contagious disease:

A

are highly communicable and are passed from one host to another easily e.g chickenpox,influenza,cholera\

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13
Q

Normal flora

A

bacteria,fungi and protozoa which live on or inside our body also known as commensals.They do not normally cause disease

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14
Q

Opportunistic infections

A

are caused by the normal flora when a person’s immune system and general health are affected due to malnutrition, surgical procedures.

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15
Q

Translocation of normal flora

A

occurs when microbes normally found in or on one part of the body are moved accidentally to an area normally sterile
Eg E.coli from the skin in the perineal region is carried to the bladder causing a UTI.

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16
Q

Genus-

A

The genus name is the first name , It begins with a capital letter eg.Staphylococcus, Escherichia
Both names are written in italics in the textbook.
In simple writing,we usually underline them

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17
Q

Species-

A

the species name is the second name.
It begins with a lower case.
Eg aureus,coli,
Both names are written in italics in the textbook.
In simple writing,we usually underline them

18
Q

Coccus (Round - only under a microscope) - most common

A

If the bacterial cell is spherical or ball shaped, the bacterium is described as coccus
Singular: coccus
Plural: cocci
Cocci can be perfect spheres, or oval/bean shaped, or even pointed variant.

Arrangement of cocci cells can be either as
1.Single
2.Diplococci
3.Tetrads- in four
4.Sarcena – cubes of 8
5.In chains-strepto
6.In clusters -Staphylo
  Species of Staphylococcus  form characteristic grapelike clusters.
19
Q

Bacillus (Rod– only under a microscope) Shaped - most common

A

If the bacterial cell is cylindrical (longer than it is wide),
then it is termed as a rod or bacillus
Bacilli are less varied in arrangement, because they divide only in the transverse plane.
Singular: bacillus
Plural: bacilli
There are a variety of rods: spindle shaped, round- ended, long and thread like When a rod is short and plump it is called a coccobacillus, bacilli in chain are called streptobacilli
A curved rod is known as a vibrio
Singular: Vibrio Plural: Vibrio Eg.Vibrio cholerae

However cells of the same species vary to some extent in shape and size. This is termed as pleomorphism eg.
   Corynebacterium diphtheriae (infection in kids  . Specially for C. diphtheriae, it is termed as a chinese letter arrangement

Singly
As a pair of cells or
randomly arranged
As a chain of several cells (streptobacilli)

20
Q

Endospore

A

These are dormant bodies produced by the bacteria
Bacillus, Clostridium , and Sporosarcina
These bacteria have a two-phase life cycle
Vegetative cell
Endospore
Vegetative cell: it is a metabolically active condition
Endospores: are induced by unfavourable environmental conditions. Allows the bacteria to cause infections after a long period as well
Both gram +ve and gram –ve bacteria produce spores, but medically relevant ones are all gram +ve
1,4- central
2,3,5- subterminal

21
Q

Rickettsias:

A

They are very tiny, gram-ve bacteria.They are parasitic
Most are pathogens that alternate between a mammalian host and blood sucking, arthopods-insects like fleas, lice, or ticks.
They cannot multiply or survive outside their host cell.
Disease caused by Rickettsia Rickettsii (transmitted by ticks)
Endemic typhs caused by Rickettsia typhi (transmitted by lice)

22
Q

Chlamydias:

A

Similar to rickettsias in the manner that they are also obligate parasites.
But are not transmitted by arthropods,but are bacteria that are sexually transmitted
Very tiny in size and at one time considered a type of virus
The family Chlamydiaceae consists of one genus Chlamydia with three species that cause human disease:
C. trachomatis, which can cause urogenital infections, trachoma(eye disease ), conjunctivitis, pneumonia and lymphogranuloma venereum (LGV)
C. pneumoniae, which can cause bronchitis, sinusitis, pneumonia and possibly atherosclerosis

23
Q

Spirochetes:

A

They are a type of bacterium.
Spirochetes have a coiled morphology resembling a metal spring.
Most distinctive characteristic of this species, is their method of Motility.
They move by the use of two or more axial filaments.
They are found in the human
Oral cavity

24
Q

Treponema:

A

Spirochetes

Treponema pallidum: cause of syphilis

25
Q

Borrelia:

A

Spirochetes

Borrelia cause lyme disease and relapsing fever, usually transmitted by ticks or lice.

26
Q

Leptospira:

A

Spirochetes
The bacteria are excreted in the urine of animals such as dogs, rats, and swine.
- Cause Leptospirosis, a disease spread to humans by water contaminated by Leptospira.

27
Q

Specimen for optical microscopy

A

Specimen can be:

  1. Live samples of morgs placed in wet mounts to check motility
  2. Also hanging drop mounts for motility,especially of V.cholerae.
  3. Permanent samples prepared by fixing and staining the specimen

Basic two types of stain are used.

  1. Positive staining
    a. simple staining
    b. Differential staining.
  2. Negative staining
28
Q

Positive staining:

A

Most procedures involve positive .staining,
where the dye actually sticks to the specimen and gives it color
Positive staining is based on the principle that the color bearing ion in the dye called the chromophore (postively charged), is positively charged and it gets attached to certain cell parts that have the
opposite charge – bacterial cell has negative charge
Staining the cell ,the color of the dye.

29
Q

Negative staining:

A

the dye does not stick to the specimen but settles around its outer boundary
It is based on the principle that the dye does not stain the cells
AS these dyes are negatively charged and are repelled by the negatively charged surface of the bacterial cells.
India ink being the most frequently used stain for this purpose and used to observe Cryptococcus neoformans,
It is an encapsulated yeast mainly causes lung infections, esp as a secondary infection in AID patients.,
Also causes meningitis

30
Q

Positive stains are classified as

A

Simple Stain: where it requires only a single dye
Differential Stain: Where in it requires
the use of two different dyes and also some additional chemical reagents to give the desired reaction
Examples-
Gram Stain,
Acid-fast
Endo-spore Staining
The base for the Gram stain and AFB stain is the bacterial Cell wall

31
Q

DNA Viruses

A

Variola and Vaccinia – small pox
Human Papilloma Virus(HPV)- Several types of warts
Hepatits B Virus (HBV) – Serum hepatits

32
Q

RNA Virus:

A

Polio Virus – Poliomyelitis
Hepatitis A Virus (HAV) - Short term hepatitis
Rubella Virus –
Mumps Virus –
Measles Virus –
Lassa Virus –
Influenza Virus –
SARS Virus – MERS Severe Acute Respiratory Syndrome
H1N1 Virus-A subtype of influenza virus Influenza like symptoms

33
Q

Bordetella pertusis

A

whooping cough
coccobacilli gram negative
NasoPharyngeal swab from nasal cavity

34
Q

Where are wet mounts seeN

A

only under 10x and 40X
Not under oil, because your condenser has to be up so you need so much light. You will miss it because the refractive index of light is the same as that of the cells which means you might miss it . So you need less light under 10 and 40X - low condenser

35
Q

Bacterial Cell Wall

A

The cell wall of the bacteria cell is a complex, semi-rigid structure which is responsible for the shape of the cell

36
Q

Clinically cell wall is important since it:

A

Contributes to the ability of some species to cause disease also known as virulency
Site of action of some antibiotics- eg.Penicillin
Differentiate major types of bacteria
Bacterial cell wall is composed of a macromolecular network called peptidoglycan - gram postive more pep ..in gram neg - less pep covered with phopholipids

37
Q

thick peptidoglycan layer

A

Some bacterial cells have a thick peptidoglycan layer forming a thick rigid structure
also Contain teichoic acids - prevent cell wall shrinkage
TAs are polymers of glycerol phosphate that help prevent extensive wall breakdown and thus helps to prevent cell lysis
Due to their negative charge, bind and regulate movement of the ions

38
Q

very thin layer of peptidoglycan

A

Some bacterial cells have a very thin layer of peptidoglycan
Consists of an outer membrane , that have lipopolysacharides
Pepitidogycan is bonded to lipoproteins in the outer membrane
They do not contain teichoic acid
More susceptible to mechanical breakage
These characteristics form the bases of the Gram’s stain

39
Q

Gram Stain

A

It is a differential stain,developed by the scientist Gram in 1884.
It is a differential stain because it seperates the bacteria into two large categories

40
Q

Reagents used for the Gram staining:

A
  1. Crystal violet: Primary stain
  2. Iodine as the mordant
  3. Acetone : Decolourizer
  4. Saffranin : Counter stain or secondary stain
41
Q

Cell-wall and Gramstain Mechanism

A

Crystal violet, the primary stain, enter both type of cells,staining the entire cell uniformly, a violet(some say a blue) color

When iodine (the mordant) is applied, CV forms large crystals with the dye forming the crystal violet-iodine complex( CVI) that are too large to escape through the cell wall

When decolorized with acetone or alcohol, alcohol dehydrates the thick peptidoglycan of some cells and makes it impermeable for the CVI complex, thus retaining the CVI complex

Whereas alcohol dissolves the outer membrane(lipids) of some cells, and leaves small hole in the thin layer of peptidoglycan through which the CVI complex diffuses out.

Thus these cells are colorless after alcohol /acetone wash
So when safranin, the counterstain is added these become pink
That is why gram +ve cells are purple
And gram –ve cells are - pink

When decolorized with acetone or alcohol,

Micro MLAB122 check 121 for lecture 4 (8 decks)

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