 Dr. Rashad Shawgi Babiker M.Sc. (Microbiology) (UMST) M.Sc. Stud. (Immunology ) Institute of Tropical Medicine.(SAS)

Normal Flora

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Definition

Normal mixture flora of is the microorganisms (bacteria and fungi) that are regularly found at any anatomical site of human body.

Symbiotic Relationship

 1. Mutualistic  Both organisms benefit – “mutually benefical”  2. Commensalistic  One organism benefits, the other is neither helped nor harmed  3. Opportunistic  Under normal conditions, microbe does not cause disease, but if conditions become conducive , it can cause disease

Mutualistic

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Escherichia coli

 Synthesizes Vitamin K & B complex Vitamins  In return, we provide a warm, moist nutrient rich environment for E. coli

Commensalistic

 We have no Commensalistic relationships with Bacteria  If Bacteria are in or on our body, they are either helping us (Microbial Antagonism) or harming us.

Opportunistic

 Escherichia coli - normally in our digestive tract where it causes no problems, but if it gets into the urinary tract it can become pathogenic.

 Staphylococcus aureus – commonly found in the upper respiratory tract, but if it gets into a wound or a burn it can become pathogenic

The Three Types of Symbiotic Relationships

Table 14.1

Normal Microbial Flora

 1. Resident Flora  Microbes that are always present  2. Transient Flora  Microbes that live in or on your body for a period of time (hours, days, weeks, months) then move on or die off

Transient Microbiota

 Remain in the body for only hours to months before disappearing  Found in the same regions as resident microbiota  Cannot persist in the body…because…  Competition from other microorganisms  Elimination by the body’s defenses cells  Chemical or physical changes in the body

Normal Flora

Sterile tissues

In a healthy human, the internal tissues such as:  blood  brain  muscle  cerbrospinal fluid (csf.) are normally free of microorganisms.

Normal Flora

 Skin  Eyes (i.e.Cunjunctiva)  Nose (i.e. Respiratory tract)  Mouth (i.e Human Oral Cavity)  Ears  Urogenetal tract  Elementry tract

Normal Flora

 Resident flora  Acquired rapidly during & after birth

Normal Flora

 Resident flora  Reflects age of person

Normal Flora

Resident flora Changes continuously through out life .

Normal Flora

 Resident flora  Reflects nutrition of person

Normal Flora

 Resident flora  Reflects genetics of person

Normal Flora

Resident flora Reflects environment of person

Normal Flora

 Resident flora  Reflects sex of person

Importance of The Normal Flora (Advantages)

1. They constitute a protective host defense mechanism by occupying ecological niches.

Importance of The Normal Flora (Advantages)

2. They produce vitamin B and vitamin K in intestine.

Importance of The Normal Flora (Advantages)

3. The oral flora contribute to immunity by inducing low levels of circulating and secretory antibodies that may cross react with pathogens.

Importance of The Normal Flora (Advantages)

4. The oral bacteria flora exert microbial antagonism against nonindigenous species by production of inhibitory fatty acids, peroxides, bacteriocins, etc.

Importance of The Normal Flora (Advantages)

5. The normal flora may antagonize other bacteria through the production of substances which inhibit or kill nonindigenous species.

Importance of The Normal Flora (Disadvantages)

1. They can cause disease in the following: a) When individuals become immunocompromised.

b) When they change their usual anatomic location.

Importance of The Normal Flora

2. The oral flora of humans may harm their host since some of these bacteria are pathogens or opportunistic pathogens

Contamination vs. Infection

 Contamination – the mere presence of microbes in or on the body  Infection – results when the organism has evaded the body’s external defenses, multiplied, and become established in the body

Portals of Entry

 Sites through which pathogens enter the body  Four major types  Skin  Mucous membranes  Placenta  Parenteral route

Skin

 Outer layer of packed, dead, skin cells usually acts as a barrier to pathogens  Some pathogens can enter through openings or cuts  Others enter by burrowing into or digesting the outer layers of skin… flesh eating bacteria

Mucous Membranes

 Line the body cavities that are open to the environment  Provides a moist, warm environment that is hospitable to pathogens  Respiratory tract is the most commonly used site of entry – entry is through the nose, mouth or eyes  Pathogens able to survive the acidic pH of the stomach may use the gastrointestinal tract as a route of entry

Some Pathogens that Cross the Placenta

Table 14.3

Parenteral Route

 Pathogens deposited directly into tissues beneath the skin or mucous membranes

Infection vs. Disease

 Infection is the invasion of the host by a pathogen  Disease results only if the invading pathogen alters the normal functions of the body  Disease is also referred to as morbidity

Manifestations of Disease

 Symptoms – subjective characteristics of disease felt only by the patient  Signs – objective manifestations of disease that can be observed or measured by others  Syndrome – group of symptoms and signs that characterize a disease or abnormal condition  Asymptomatic, or subclinical, infections lack symptoms but may still have signs of infection

Etiology

 Study of the cause of disease  Germ theory of disease – disease caused by infections of pathogenic microorganisms  Robert Koch developed a set of postulates one must satisfy to prove a particular pathogen causes a particular disease

Koch’s Postulates

Figure 14.7