Download Suez Canal University

Suez Canal University
Faculty of Veterinary Medicine
Department of Bacteriology – Immunology- Mycology.
Answer model (1st semester 2009)
1-Effect of temperature on bacterial growth and viability?
A- Effect of temperature on bacterial growth:
*Each M.O has 3 levels of degree of temperature:
1-Maximum degree of temperature:
-Highest degree of temperature upon which the M.O can't live.
2-Minimum degree of temperature:
-Lowest degree of temperature under which the M.O can't live.
3-Optimum degree of temperature:
- Degree of temperature at which all physiological, metabolic and
biological activities take place.
*So we classify bacteria acc. to temperature requirement into:
1-Psychrophillic Bacteria:
-Bacteria that live below 20 c° (present in deep layer of ocean and cold
springs)
-Cause spoilage to frozen food.
2-Mesophillic bacteria (20 c° -40 c°):
-Include Saprophytic Bacteria (20 c° -30 c°) and Pathogenic bacteria
(37c°-40c°).
3-Thermophillic Bacteria (over 40c°-90c°):
-Cause spoilage of dairy products (pasteurized milk).
B-Effect of temperature on bacterial viability:
-Determined by:
1- Dry heat (Oxidation and charring of Bacterial cell)
2-Moist heat (Coagulation and denaturation of protein)
-Moist is more preferred than dry heat?
a-Has high penetration power
b-Require shorter time and lower temperature.
*****************
2-Difference between procaryotes and eukaryotes?
Characters
procaryotes
Eukaryotes
size
smaller
larger
nucleus
primitive
true
Nuclear membrane
absent
present
nucleolus
absent
present
chromosomes
Single ,circular
Multiple linear
reproduction
Asexual (binary fission)
Sexual & asexual
ribosomes
Small (in cytoplasm)
Large (carried on E.R)
Cytoplasmic
absent
present
absent
present
mitochondria
absent
present
Golgi apparatus
absent
present
Cytoplasmic
absent
present
Histone protein
absent
present
Examples
Bacteria, blue green
Fungi, plant cell.
streaming
Endoplasmic
reticulum
membrane
algae
3- Gene transmission from one bacteria to another:A- Transformation
B- Transduction.
C- Conjugation.
A- Transformation
- DNA is extracted either by natural or artificial lysis of bacterial cells, so
it become extracellular DNA ( Free in media), DNA can transfer to
another bacterial cell.
- Its mechanism of entrance is still unknown but
may be due to some species of bacteria have
receptors on cell wall due to some species have
receptors on cell wall which attract the DNA.
These cells termed (Competent cell).
Example:1- Make artificial extraction of DNA of
capsulated pneumococci.
2- Then bring 2 tubes contain broth culture of
non capsulated pneumococci.
3- Then the extracted DNA of capsulated bacteria in only one of the
two tubes.
4- Incubation for 24 hours at 37C°.
Observation:- When we take a film from tube one and examine under microscope, the
non capsulated bacteria become capsulated, but when we examine the
film from the second tube, non capsulated bacteria still non capsulated.
B- Transduction ( Bacteriophage mediated transfer)
-Phage definition:Is specific strain of virus which
live on specific bacterial strain (Highly specific in
action).
-Mechanism of attachment ( Phage host life cycle):
1- Specific
adsorption
2- Penetration
3- Eclipse
4- Replication
5- Assembly
6- Release
3-Conjugation
- Conjugation mainly occur in Gram negative bacteria
as E Coli, pseudomonas aeroginosa.
- One cell act as male ( donor cell or F +ve) and the
other act as female ( recipient or F –ve).
- F +ve cell make bridge between itself and F –ve
through this bridge genetic materials ( DNA or plasmid)
transmitted so both cells become F (+ve).
- Also it may occur in some G+ve bacteria as S.fecalis, The
recepiant cell produce extracellular substance ( Phermone) That
attract donar cell.
- Conjugation controlled by special type of plasmid ( F plasmid or F
factor).
***************************
4- Bacterial cell wall?
Bacterial cell wall is elastic and rigid, its rigidity is due to presence of
peptidoglycan .
- Its absent in Mcoplasma.
- The failure of synthesis may occur due to environmental factors as
presence of penicillin in the media.
- Removal of defective formation resulted in development of various
abnormal forms.
1- Spheroplast in Gram –ve bacteria.
2- Protoplast pleomorphic form of G+ve bacteria.
3- L- form.
Function of cell wall:1- Protect the bacteria from physical and chemical agents.
2- Selective and osmotic permeability
3- Act as exoskeleton responsible for the shape of bacterial cell
4- Support the cytoplasmic membrane against the high internal
osmotic pressure of cytoplasm
5- Responsible for integrity of bacterial cell
6- Play a great role in bacterial cell division
7- Target of most antibiotics as penicillin and its derivatives
5- Bacterial motility ?
- Flagellum is thread like structure arise from the cytoplasmic membrane
act as organ of locomotion formed from protein ( Flagellin) and contain
flagellar antigen ( H Antigen)
- We classify bacteria according to motility into:-
Motile bacteria
Flagellar
motility
EX. E Coli
and proteus.
Non motile bacteria
Ex. Staphylococcus
and Streptococcus.
Spirochaetal or
contractile body
movement
- In spirochaetes.
-We classify bacteria according to distribution of flagella
into:-
1- Atrichous:- no flagella present.
2- Monotrichous:- presence of single polar flagellum.
3- Amphitrichous:- presence of single flagellium at each side.
4- Lophotrichous:- tuft of flagella at one or both end.
5- Peritrichous:- soft fewer flagella all over the body.
-Detection of bacterial motility:1- Hanging drop technique.
2- Cultivation on semisolid agar or U tube method.
3- Cultivation on solid media ( swarming in proteus).
6-Bacterial virulence?
Definition:-Is temporary natural property of any bacterial strain in certain growth
phase in order to produce pathological status in a specific host when
introduced under a certain condition.
Components of virulence:1- Toxigenicity:- Is ability of bacteria to produce toxins which cause damage of living
tissues.
- The more the power of toxin the higher degree of virulence.
- EX. Cl.tetani:- Tetanus disease.
Cl.botulinum:- Botulism.
- Both produce neurotoxins that affect the nervous system.
2- Invasiveness:- It’s the ability of bacteria to invade the host tissues and organs.
- The more the invasiveness the higher the degree of virulence.
- It may be accompanied by toxicity.
- Ex. Bacillus anthracis.
3- Communicability of he disease:- It’s the ability of bacteria to become established in the host under
natural condition to be shed in large number in body fluids or excretions
in order to infect or transmitted to new host.
4- Physiological sate of bacteria:- In Most species of S- form is more virulent than R -form except
B.anthracis.
5- Resistance to the host defense mechanism:- Presence of capsule ( prevent phagocytosis) and other antigens (O & VI
antigen in salmonella), make bacteria more resistance to phagocytois.
Alteration of virulence
1- Exultation:- It means increase of virulence of bacteria and done by :A- Addition of mucin to bacterial suspension.
B- Addition of aggressin to bacterial suspension
C- Addition of irritant substances as CaCl2.
D- Several cultivation on highly enriched media (as Blood agar,
milk agar and egg media).
E- Serial passage in susceptible lab animals.
2- Attenuation:- It means decrease the virulence of bacteria and done by:A- Serial passage in unsusceptible lab animal as injection of cattle
plague in rabbit.
B- Cultivation of M.O under unfavorable conditions.
C- Prolonged period of incubation as Pasteur vaccine of
B.anthracis.
D- Addition of specific antisera to the media.
E- Addition of dyes and disinfectants to the media.
Measurement of virulence:- By LD50 (It means the dose of M.O that kill 50% of inculated Lab
animals).
7- Synergistic bacteria:-When two or more bacteria produce certain effect at which non of them
could do it alone.
Ex:- E coli not make gas production in milk unless presence of
proteolyic bacteria such as clostridium perferingens.
*******************
8- Heterotrophic bacteria:( Chemo-organotrophic bacteria)
-Bacteria that derive their energy by utilization of organic compounds
derived from animal or plant source, they live mainly in or on the animal
body and have veterinary and medical importance.
Ex.
Pathogenic bacteria.
****************
9- Bacterial products
- It includes:1- Pigments.
2- Toxins.
3- Enzymes.
4- Light production.
5- Heat production.
6- Miscellaneous products.
1- Bacterial pigments
A- Exopigemnts:- this pigment diffuse into surrounding media.
- Have diagnostic value in many bacterial types.
- EX. Ps.aeroginosa pyocyanin (Blue).
Ps.aeroginosa fluorescin (yellowish green).
- May have role in bacterial respiration and some have antibacterial
action.
B- Endopigments:- Don’t diffuse to the media so bacterial colonies are coloured but media
is not.
- Ex. S.aureus:- golden yellow.
S.albus:- white.
S.citrus:- lemone yellow.
Serratia marcessens:- red.
2- Bacterial toxins:properity
1- Production.
2- Nature.
Exotoxin
Endotoxin
Gram +ve bacteria
Gram -ve bacteria
Protein
Phospholipids
polysaccharide
complex.
3- Diffusibilty.
Diffusible
Non
4- Toxicity
High
Low
5- Specifity.
Highly specific in action
Non specific
6- Antigenicity.
Strongly antigenic
Weak antigenic
7- Heating at 60
Destroyed
Stable
8- Effect of
Changed into toxoid( loss
Not detoxified by
formaline.
toxicity but still antigenic)
formalin
9- EX. of
Cl.tetani
Salmonella typhi
bacteria
C.diphteria
– 80C.
3- Bacterial enzymes:- Protein in nature, act as a biological catalyst.
- Types:A- Exoenzymes( digestive enzymes).
B- Endoenzymes ( Responsible for energy transformation of the
cell.
4- Heat production:- All bacteria produce heat, but variable according to species and
nature of MO.
5- Light production:- Fluorescent bacteria produce light and not affected by UV rays because
they convert short wave length into longer wave length UV rays.
6- Miscellenous products:- As CO2, indol, Methane and H2S
******************
10 –Koch's postulates?:
1- The microorganism must be constantly present in every case of the
disease
2- It should be isolated in pure culture in vitro.
3- It must be reproduced into a susceptible lab. animal.
4-It must be reisolated in a pure culture.
5- The demonstration of specific antibody against the microorganism in
serum of infected cases and its absence in normal cases.
Exceptions:1- Some M.O can't be cultivated on artificial media as viruses.
2- Synergistic action of bacteria (mixed infection).
3- Some M.O needs serial passage firstly in susceptible lab animals to
regain their virulence.
***********************
11- Serum Sickness
- Is systemic form of type two immediate hypersensitivity ( Cytotoxic
reaction).
- When the antigen is injected I.V combined with the circulating IgG and
IgM then subsequent complement fixation.
- That resulted in the formation of microprecipitate complex around blood
vessels and in tissues
- Ex.
1- Injection of horse serum (The antitetanic serum) characterized by (
high fever, swelling in lymph nodes, swelling and pain in joints)
2- Penicillin injection.
*******************
12- Role of macrophage in immunity
- They are active phagocytic cells distributed in different tissues and
organs as:( Kupfer cell in liver, Monocytes in blood, Dust cell in lung and
histocytes in connective tissues).
- The process of phagocytosis:1- Chemotaxis:- It’s the attraction and movement of phagocytes toward the site of
inflammation.
2- Opsonization:- Increase the efficiency of macrophage to ingest the MO by coating it by
opsonin protein.
- Example:- Plasma opsonin and complement C3b.
3- Ingestion:- Is the englfment of the adherent MO to macrophage
surface internally by the pseudopodia.
4- Degranulation:- Release of antibacterial agent ( The lysozymes and digestive enzymes).
5- Killing and digestion of M.O:- Take place by the help of bactericidal and digestive enzymes.
*************************
13- Requirement of immunogenicity:1- Foreignness:
- Immune system differentiate between self and non self cells, the foreign
molecules is only immunogenic.
2- Molecular weight:- Must be not less than 10.000 daltons.
- The most potent one are macromolecules proteins ( more than 100.000
daltons).
3- Chemical complexicity:- The more chemical complexicity , the more immunogenicity.
4- Physical state of antigen:- Soluble antigen as toxin and extract are highly immunogenic than
suspension of bacteria or RBCS.
5- Antigenic valency:- i.e Number of epitopes of antigen ( The high number the more
immunogenicity)
6- Genetic constitution of individual:-Some antigens are immunogenic to some individuals and non to the
other.
- EX. Pure polysaccharides are immunogenic to human and mouse and
not in G. pig.
7- Methods of antigen administration:- I.V and S.C route are effective but S.C + adjuvant is more
immunogenic.
******************************
14- Lysozymes?
Definition:- Basic protein of low molecular weight found in high concentration in
neutrophil as well as tissue fluids except CSF, also present in human tears
and egg white.
- Function:1- Act as mucolytic enzyme against G +ve bacteria resulting in lysis of
bacterial cell wall.
2- Play role in destruction of some G – ve bacteria by help of complement
and action of enzymes of phagocytes that remove LPS and expose
mucopeptide to action of lysozymes.
************************
15- Natural active acquired immunity?
- Occur due to infection either with or without symptoms then followed
by recovery.
A- Long lasting immunity:- when the causative agent characterized by
constant antigenic structure as diphtheria, pox and measles.
B- Short or medium lasting immunity:- when the causative agent
characterized by different serotypes of the species as Influenza and FMD
in cattle.
***************************
*Under supervision of:
-'Prof.Dr: Mohammed EL-Sayed Enany'.
Head of department of Bacteriology - Immunology- Mycology.