Microbiology Introduction 2

Microbiology Introduction 2

Normal Human Flora:

Normal microflora/ normal microbiota/ normal flora.

Bacteria makes up most of the normal flora

Symbiosis: more than two organism living  together ( bacteria on our skin)

  • Ecto-symbiosis: one organism remains outside the other
  • Endo-symbiosis: one organism is present within the other
  • Commensalism: one organism benefits while the other is neither harmed or benified (bacteria on the skin = we live happily)
  • Mutualism: both benefit: In the gut – they live and eat and they also help us with digestion.
  • Parasitism: benefits only go to the parasite while the host has to provide food, and other metabolic needs (disease)

Normal Flora Function:

  • They colonise specific sites (may turn pathogenic if they move to a different location) They inhabit different parts of the body doing no harm
  • They create an environment that inhibits growth of other microbes
  • They help provide vitamins and eliminate toxins
  • They don’t do harm to us, instead, they protect us from harmful bodies

It has to be balanced, if there is too much = it isn’t good at all.

Normal flora location:

  • Skin
  • Mouth
  • Gut
  • Digestive tract
  • Respitory tract
  • Genitourinary system

Location is most important as if moved  it may turn pathogenic.

Micoflora plays and important part in stimulating the bodies immune system


Susceptibility to infection depends on:

  1.  Where the disease is living, on a cat, tick, human
  2. How it got into the body, eating or a scratch
  3. If our immune system is down we may have trouble fighting it off
  4. Circumstance of Infection
  5. How strong the pathogen  is (immune to antibiotics or such)

Reservoirs/ Habitat

  • in or on animals
  • in or on insect (vectors)
  • in or on food
  • in or on soil
  • in or on water
  • in water
  • in or on inanimate objects
  • in or on people

Microbes like moisture but there are some that like the dry.

The reservoirs can either be favourable=survive and increase in number or unfavourable=survivable as a resistant form

Disease can be spread via human to human or animal to human (zoonosis), and non-living reservoirs (soils and water)

Human Reservoirs:

  • constant production and shedding of pathogens
  • change in degrees of infectivity at different times

Animal Reservoirs:

  • Animals harbour microbes for a long time without any symptoms
  • Often animals get infected and no one notices, animal infects human, either by vector or direct contact.

NonLiving Reservoirs:

  • Can lie dormant for a very very long time
  • Spors, lave, eggs, fungi, some can be found in canned foods.
  • Water is vital to be clean and filtered

Has to enter the body and in significant numbers, have a safe place (ph, temp ) to colonise


Dependant on 3 factors:

  1. Number of microorganisms entering host
  2. Optimal environment, stability to grow and thrive
  3. Number of microbes needed to start an infection

Mode of Transmission:

  • Contact:
  1. Direct

(a)    Self to self ;children- faecle/oral route

(b)   Person to person

(c)    Animal to person (anthrax)

(d)   Water or soil to person

  1. Indirect

(a)    Left behind by others : touching places where they had touched

  1. Droplet

(a)    Coughing

(b)   Sneezing (easy to infect others)

  • Vechicle
  1. Air-Born

(a)    Aircon spreads germs around

(b)   Contracted by inhalation

(c)    Aerosols – water droplets : eg Legionnaires

(d)   Microbes must be able to survive outside a body (fungi, TB – can survive several days without a host)

  1. Water-Born

(a)    Ingestion

(b)   Bathing

  1. Food-Born

(a)    Food spoilage sue to microbe growth

  • Vector
  1. Mechanical

(a)Passive, outside the insect body: touch: a fly landed on me.

  1. Biological

(a)    Susceptible to insect bite

One person can infect a whole group of people, eg one sick person cooking food for everyone else can infect them all. (branch, like stds)

Portal Of Entry Into The Body

  • Eating (mouth)
  • Breathing (nose)
  • (Genital) =  Orifices
  • Burns, damage to the skin
  • Skin
  • Contact with blood if skin was broken
  • Mucosal
  • Eyes
  • Ears
  • Conjunctiva, Lacrimal glands
  • Puncture wounds
  • Burrowing parasites
  • Splits or tears from dehydration
  • Odeama
  • Hair follicles
  • itching scratched/bites

Waterborn/ Foodborn microbes affect Git: Gastro Intestinal Tract, from entering through nose and mouth.
Microbes causing STD’s enter through Gut: Genital Tract

Portal Of Exit

  • Mucus (sneezing, coughing and spluttering) Sputum (Whooping cough, TB)
  • Saliva (Mumps, G Fever, HepB)
  • Urine
  • Semen and Vaginal secretion (HepB and AIDS and STD)
  • Faeces (Polio, Colera)
  • Blood (HIV, AIDS, HepB and C)

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