Lecture 3

Question 1

Endemics:

Answer 1

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

Question 2

Epidemic

Answer 2

Serious infections affecting a larger than normal number of population

Question 3

Pandemic

Answer 3

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

Question 4

Acute infections

Answer 4

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

Question 5

Chronic infection:

Answer 5

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

Question 6

Local infection:

Answer 6

are confined to a small area of the body

Question 7

Systemic infections:

Answer 7

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

Question 8

Primary Infections

Answer 8

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

Question 9

Secondary infections-

Answer 9

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

Question 10

Infectious disease:

Answer 10

require that microbes or their toxins enter the body

Question 11

Communicable Disease

Answer 11

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

Question 12

Contagious disease:

Answer 12

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

Question 13

Normal flora

Answer 13

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

Question 14

Opportunistic infections

Answer 14

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

Question 15

Translocation of normal flora

Answer 15

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.

Question 16

Genus-

Answer 16

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

Question 17

Species-

Answer 17

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

Question 18

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

Answer 18

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.

Question 19

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

Answer 19

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)

Question 20

Endospore

Answer 20

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

Question 21

Rickettsias:

Answer 21

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)

Question 22

Chlamydias:

Answer 22

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

Question 23

Spirochetes:

Answer 23

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

Question 24

Treponema:

Answer 24

Spirochetes

Treponema pallidum: cause of syphilis

Question 25

Borrelia:

Answer 25

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

Question 26

Leptospira:

Answer 26

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.

Question 27

Specimen for optical microscopy

Answer 27

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

Question 28

Positive staining:

Answer 28

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.

Question 29

Negative staining:

Answer 29

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

Question 30

Positive stains are classified as

Answer 30

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

Question 31

DNA Viruses

Answer 31

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

Question 32

RNA Virus:

Answer 32

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

Question 33

Bordetella pertusis

Answer 33

whooping cough coccobacilli gram negative NasoPharyngeal swab from nasal cavity

Question 34

Where are wet mounts seeN

Answer 34

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

Question 35

Bacterial Cell Wall

Answer 35

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

Question 36

Clinically cell wall is important since it:

Answer 36

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

Question 37

thick peptidoglycan layer

Answer 37

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

Question 38

very thin layer of peptidoglycan

Answer 38

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

Question 39

Gram Stain

Answer 39

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

Question 40

Reagents used for the Gram staining:

Answer 40

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

Question 41

Cell-wall and Gramstain Mechanism

Answer 41

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,