LAB 4 : Sources of Contamination and Infection

Introduction :

     Airborne micro-organisms are usually carried on dust particles, although some ( fungal spores, for example ) ay be carried directly by air currents. It is important for microbiologist to be aware of the potential for contamination by airborne micro-organisms. Carefully observation of simple precautions dramatically reduces the risk of contamination of the cultures.

     Every human is colonized by billions of micro-organisms. These micro-organisms, some of which are vital to our well-being, constitute our resident or normal microflora. Resident micro-organisms are nourished by the chemicals and moisture excreted by the human bod. In moist areas such as armpit, there may be one billion bacteria per cm^3 ; on the drier skin of the forearm, there may be 10000 bacteria per cm^3!!!

     Resident micro-organisms are either non-pathogenic or are prevented from infecting the body by an array of mechanical and chemicals defences. Some resident microbes are, however, opportunistic pathogens which may cause infection if the body's defences are breached-for example, if the skin is broken.

      Transient micro-organisms are picked up from our environment- for example from faecal contact or from soil-and usually fail to become permanent skin residents. One of the most important reasons for failure to gain permanence is that the established residents are better able to compete for nutrients, Since transients generally originate in other environments, they are poorly adapted to conditions on the skin and usually disappear within 24 hours arrival.

     Micro-organisms in the upper respiratory tract are either normal residents or transients, As with the skin, normal microflora largely consists of non-pathogens or opportunistic pathogens.

     Large numbers of transients enter the upper respiratory tract as we breathe or eat. They may also come from our own hands or from improper sanitation during food preparation. Regardless of their origin, most transients are non-pathogenic and are quickly killed by various defences arrayed against them.

Objective :

To determine the micro-organisms in the air and from healthy humans.

Materials and reagents :

Molten nutrient agar
Sterile water
sterile Petri dishes
Sterile clinical swab
Pipette and tips

Procedure :

Air :
         1. Pour the molten agar into sterile Petri dish and cool.
         2. Remove the lid from the plate and leave it resting on the side of the plate, facing
             down. ( Never invert the lid of the Petri dish). Leaves the plates exposed for 5
             minutes.
         3. Replace the lids and incubate at 37^oC for 48 hours.

Hands :
         1. Wash hand using sterile water. Do not use soap.
         2. Use an automatic pipette to transfer 1mL of wash water to the Petri dish.
         3. Add molten nutrient agar to the Petri dish.
         4. Replace the lids of the Petri dish and gently rotate the dish until the wash water is
             thoroughly mixed with the molten agar. Do not allow the agar to contact the lid of the
             dish.
         5. After the agar has set, invert the dish and incubate at 37^oC  for 48 hours.

Ear :
         1. Pour the molten agar into the sterile Petri dish and cool.
         2. Using extreme care, rub the sterile swab moistened with sterile isotonic solution into
             the ear of the subject.
         3. Use the swab to inoculate the labelled plate. Distribute the inoculum as in the streak
              method.
         4. Incubate at 37^oC  for 48 hours.

Normal breathing :
         1. Pour the molten agar into the sterile Petri dish and cool.
         2. Remove the lid and hold the plate about 15cm from your mouth. Breathe normally
             but directly onto the plate for one minute. Replace the lid.
         3. Incubate at 37^oC  for 48 hours.

Violent coughing :
         1. Pour the molten agar into sterile Petri dish and cool.
         2. Remove the lid and hold the plate 15cm from your mouth. Cough violently onto the
             agar. Replace the lid.
         3. Incubate 37^oC for 48 hours.

Results :

a) Using nutrient (commercial) agar : 

1) Air colonies

Form	Irregular, Filamentous
Elavation	Raised, Umbonate
Margin	Curled

2) Cough colonies

Form	Circular, Irregular, Filamentous
Elavation	Raised
Margin	Curled

3) Breath colonies

Form	Circular, Irregular
Elavation	Raised, Umbonate
Margin	Entire

4) Ear Colonies

Form	Circular, Irregular
Elavation	Raised, Flat, Crateriform
Margin	Entire, Filiform

5) Hand Colonies

Form	Circular, Irregular
Elavation	Flat
Margin	Entire

b) Using Own Recipe :

1) Air Colonies 

Form	Circular, rhizoid
Elavation	Raised
Margin	Curled

2) Hand Colonies

Form	Rhizoid, irregular, circular
Elavation	Umbonate, crateriform, raised, flat
Margin	Entire, lobate

3) Ear Colonies

Form	Circular, irregular
Elavation	Convex, raised
Margin	Filiform, entire

4) Breath Colonies

Form	Circular, irregular
Elavation	Convex, flat, umbonate
Magin	entire

5) Cough Colonies

Form	Filamentous
Elavation	Crateriform,  umbonate, flat, raised
Margin	Entire,  undulate

Discussion :

1. When pour the nutrient in to the Petri dish, remember mix well the solution. This is to

    avoid the agar from deposit at the bottom of the solution which may result the agar being

    solidify at the bottom and causes the nutrient in the Petri dish cannot be solidify.

2. The nutrient must keep at certain temperature to avoid the agar from being solidify.

    When see the bottom of the agar start to solidify, put the agar solution in the oven and

    reheat it.

3. When pour the nutrient avoid the nutrient touching the lid or side of the Petri dish.

    Because this may cause contamination that will affect your result.

4. When doing the each contaminant sample, remember to cool down the temperature of the

    nutrient solution until the temperature that are touchable by our hands. This is to avoid

    the bacteria killed due to the high temperature of the nutrient and affected the result.

5. After pour the nutrient into the hands` sample remember to mix the hand washed water

    and nutrient agar by doing 5 times “ 8 “ number motion slowly to mix it well.

Conclusion :

Micro-organism like fungi, bacteria and protozoa can be found in air and surrounding environment that compatible to their living condition. micro-organism also can live within living host like us for example in our hand and some of them might cause harm if a proper technique of hang washing is ignore. but most of them are symbiont living thing without causing any harm or good.

Reference :

http://en.wikipedia.org/wiki/Infection

http://en.wikipedia.org/wiki/Contamination

http://en.wikipedia.org/wiki/Microorganism#Habitats_and_ecology

http://wiki.answers.com/Q/Do_we_have_bacteria_on_our_hands#ixzz1IFqPqcDp

http://www.articlesbase.com/diseases-and-conditions-articles/types-and-prevention-of-bacteria-471084.html