Microbial Pathogenesis

Microbial pathogenesis:-

Microbial mean Micro-organisms for example Bacteria, virus, fungi pathogenesis means disease-causing so microbial pathogenesis is the story of those micro-organisms which cause disease.

There are two types of micro-organisms.
1 Normal Flora. 2 Pathogenic.

Normal flora and pathogenic:

These are those micro-organisms which are present in different parts of the body and they cannot cause disease. These micro-organisms are present in a specific form so it means that those micro-organisms are not harmful but if these micro-organisms leave has specific Place and they move to another part of the body then these micro-organisms are not normal flora, they will cause disease. So these micro-organisms are pathogenic because of causal disease. The normal flora is Avirulent.

The pathogenic is virulent.

Avirulent:-
Those micro-organisms which cannot cause disease.

Virulent:-
Those micro-organisms which can cause disease.
There are two types of virulent organisms.

1 More virulent (Danger)

2 Less virulent

Here a question can arise that what is Virulency? So

Virulency:-
The degree of pathogenicity is called Virulency.

So what is pathogenicity?

Pathogenicity: -
The ability of micro-organisms to cause a disease in Host.

Lethal dose:

The lethal dose is also called LD₅₀

ID₅₀:-

Full form infection dose 50.

What are ID₅₀ and LD₅₀?
The ID₅₀ full from is infection the LD₅₀ is lethal dose ID₅₀ is used for the dose of bacteria and LD₅₀ is used as disease-causing agents.

So ID₅₀ means that how many organisms require to cause disease in 50% of those exposes to the pathogens.

LD₅₀ the number of Pathogens that we take for killing 50% of that particular population.

why they are lethal?

Because they are killing the organisms. So lethal dose means that the particular number of pathogens which is killing 50% of the individual and infection Dose means the Parboil number of the pathogens that are taken for the treating of infection or disease in 50% of the individual.

Infection Definition:

The result of affecting injuriously.

Disease Definition: The abnormal condition of the body.

Difference between disease and infection:

Disease:

In a disease, the micro-organism may involve or may not. The disease is the abnormal condition of the body.

Infection:

In an infection, the micro-organisms are always involved. The infection is the result of affection injuriously.

Opportunistic Micro-organisms:

The Opportunistic micro-organisms are those micro-organisms when the immune system is a week then they cause disease in the host. A bacteria, virus, protozoan or fungus that take advantage of certain opportunities to cause disease. These opportunities are called opportunistic condition.

These micro-organisms with compromised with host e.g of opportunistic disease AIDs
.

Anthrax:- (splenic fever)

It is a disease caused by Bacillus anthraces (a germ (bacteria) that’live in soil ) many People know about it from the 2001 bioterrorist attacks. In the attacks, someone purposely spread anthrax through the U.S. mail. This killed 5 People and make 22 sick. Anthrax is rare its affects animals such as cattle, sheep, and goat more often than people. People can get anthrax from, contact with infected animals, wool, meat or hides it can cause three types of disease in people.

1 Cutaneous: -
which affects the skin. People with cuts or open sores can get it if they touch the bacteria.

2 Inhalation:-
Which affects the lungs we can get this if we breathe in spores of the bacteria.

3 Gastrointestinal:
Which affects the digestive system you can get it by eating infected meat Cure.

NIH: National Institute of allergy and Diagnosis in an animal:

Koch Postulates:

The Doctor Koch is a German scientist he first Established that the disease-causing by bacteria. The relation between the disease and bacteria or caused organisms is defended by these postulates. The defined 4 Postulates.

1 Micro-organisms should present in all the diseased organisms and absent in healthy organisms.

2 Causal organisms should be isolated in culture and Pure form.

3 Isolated Organisms à if calculated in a healthy organism the same disease should accord.

4 It should be again isolated and the organisms are cause some diseases in an individual.

The exception of Koch postulate:

1. some microbes need unique culture condition they are intracellular parasites ( Like viruses) They can’t grow on artificial media.

2. some pathogens cause different types of disease.

3. Some disease may be caused by a variety of microbes (involving a lot of micro-organisms )

4. Some pathogens, such as S pyogenes cause several types of diseases.

5. Certain pathogens such as HIV cause disease in human only.

Classification of disease

1. Infectious disease.

2. Communicable disease.

3. Non-communicable disease.

4. Contiguous disease.

1 infectious disease:

The disease which causes by the micro-organisms.
for example. Influenza
(Flu) its caused by the influenza viruses.

2 Communicable disease:

That disease which can transfer from one person to another. Example Hepatitis A.B.C

3 Non-communicable disease:-

That disease which cannot transfer from one person to another. Example Heart disease Diabetes.

4 Contiguous Disease:

That disease which can Transfer by the physical contact with the person suffering the disease. Example of AIDs.

Occurrences of Disease

1 The incidence of disease:

The number of people in a population who develop a disease during particular time 2009 (30, 000)

Prevalence:

The number of people in a population who develops the disease old and new both during specific time period e.g AIDs in us 2004 incidence 40,000, 2004 Prevalence 90,-0000.

Sporadic Disease:

If a disease occurs occasionally e.g Typhoid fever in us.

Endemic disease:

A Disease constantly presents in a population. e.g in Pakistan tuberculosis 5/20 malaria 1 million people per year. Polio à in country Pakistan one of them.

Epidemic disease:

The disease which developed in many people in a very short time. e.g influenza.

Pandemic Disease:

All over the world severity of the disease.

1 Acute Disease:
e.g influenza suddenly occur but for short time.

2 Chronic Disease:

Develop more slowly but body reaction is more severe e.g HIV.

3 Latent disease:

The causative agent remains inactive for a longer period and the suddenly become activated and cause disease e.gVaricella zoster virus.

They cause through animals:

Shingles create and they too painful.

The extent of host insolvent

Two types

1 Local infection:
Locally specific area e.g: absences

2 General infection:

It's also called generalized or systematic infection.

Micro-organism:

Get entered into the blood or lymph. They can spread throughout the body suitable condition e.g measles.

SEPSIS:
Inflammation condition arises from the spread of Mo through blood.

Specimina:

The pathogen is blood e.g. Bacteria, virus, toxin.

If bacteria involved in blood is called bacteremia.

If virus involves in blood its called viremia.

If toxin involves in blood its called toxemia.

Primary infection: initial illness.

Secondary infection: Opportunistic infection.

Pattern of disease

1^st Phase: - Reservoir of pathogen must be present for causing a disease.

2^nd Phase: The pathogen must be transmitted to a susceptible host through directly, indirectly or vector.

3^rd Phase: Reproduction (also called Multiplication )

4^th Phase: Invasions. (Attack)

5^th Phase: Transmission to the other host.

Predisposing factors:-

The factor which may the host more susceptible to a specific disease.

Example (1) Genetics. (2) Gender. (3) Diabetic. (4) Climate. (5) Occupation. (6) Life style (7) Habits (8) involute nutrition (9) fatigue.

Development of disease:
There are five major periods of development of the disease.

(1) Incubation period.

(2) Period of illness.

(3) Prodromal period.

(4) Convalescence Period.

(5) Period of Decline.

1 Incubation Period:
The time interval between the initial infection and appearances of first sign and symptoms.

They are save for some micro-organisms and also variable.

S pyogenà 1-3 days.

Factors: 1 types of micro-organisms. 2 Hostà defend. 3 Virulent. 4 A number of infecting micro-organisms.

2 Prodromal period:

Following by infection period.

è Very short period.

è Appearance of general systems.

Oches à Painful. And Malaiseà discomfort.

3 Period of illness:

it is an acute phase: most severe sign and symptoms.
The immune system either overcomes pathogen or person dies.

4 Period of decline:
Signs and symptoms begin to subside, but Host vulnerable to secondary infections.

5 Period of convalescence:
Host returns to the pre-disease state.
For some diseases, a person is contagious from incubation to convalescence, for others only during illness.

Spread of infection:
1 Reservoir of infection
2 Transmission
   1 Reservoir of infection: ( Source of disease agent)
There are two types of reservoir.
1 Living
2 Non living

   1 Living:
In living humans and animals are present.
Humans:
Sick people = Actively ill
carriers = never any symptoms / sign of disease.
Latent infection carriers = Contagious during incubation period or convalescent period.
Animals:
Zoonoses = Disease that can be transmitted from animal to human e.g Rabies

2 Non living:
There are three types of non living reservoir.
1 Food = In food (food borns) micro-organisms is present which cause food poisioning.
2 Water = In water (Water borns) Micro-organisms is present which cause dirahral infection.
3 Air = In Air (Air born micro-organisms) streptococus ( Bacteria) is present which enter through respiratory track in cause many disease.
2 Transmission:
There are three types of transmission.
1 contact transmission.
2 vehicle transmission.
3 Vectors
1 Contact transmission:
1 Direct contact:
(Person to person)
(e.g STDs)
2 Indirect contact:
Reservoir to Host Via fomite ( a non living object that transmits disease ) e.g syringe, surfaces.
3 Droplet transmission:
Mucus droplets for sneeze or cough e.g pertussis.

2 Vehicle Transmission:
In a medium
1 Water born transmission e.g cholera.
2 Food born transmission e.g food poisoning.
3 Air born transmission like Droplet transmission but travels further then one meter or on dust. or by spores (e.g histoplasmosis)
4 Other media: Body fluids, Drugs ( e.g HIV).

3 Vectors:
animal that carry pathogens from one host to another: mostly arthropod.
There are two types of vectors.
1 Mechanical transmission.
2 Biological transmission.

1 Mechanical transmission:
Passively carry pathogens on body parts e.g houseflies.
2 Biological Transmission:
From bites usually involves complex life cycle of pathogen. Cycling between vector and host e.g mosquito=malaria.

Keywords : mycology ,  Microbial anatomy and physiology , Microbial Pathogenesis , Soil Microbiology , Immunology.

Microbiology

Microbial Pathogenesis