Refers to the events that occur outside the body, whereas in vivo refers to the events that occur inside the body.

FACTORS THAT AFFECT MICROBIAL GROWTH…

All living organisms require nutrients ---the various chemical compounds that organisms used in order to sustain life.

Nutrients also serve as the sources of carbon, oxygen, hydrogen, nitrogen, phosphorus and sulfur (as well as other; sodium, potassium, chlorine, magnesium, calcium, trace elements such as iron, iodine and zinc.)

About two dozen of the approximately 92 naturally occurring elements are essential to life.

Cells consist of anywhere between 70% and 95% water.

All living organisms require water to carry out their normal metabolic processes, and most of them will die in the environments containing too little moisture.

Bacterial endospores, protozoan cysts can survive completely in the drying process called dessication.

Every microorganism has an optimal, a minimum, and a maximum growth temperature.

The temperature at which the organisms grows best

A temperature BELOW on which organism ceases to grow.

MAXIMUM GROWTH TEMPERATURE

ABOVE, temperatures which an organism dies.

Microorganisms that grows best at high temperature.

They can be found in hot springs, compost pits and silage as well as in and near hydrothermal vents at the bottom of the ocean.

Organisms that favor the temperatures above 100 degrees Celsius are referred to as hyperthermophiles (or extreme thermophiles)

Example: pylorobus fumarii– has found living at around 113 degrees Celsius.

Microbes that grows best at moderate temperatures.

This group includes most of the species that grow on plants and animals and in warm soil and water.

Most pathogens and members of the indigenous microflora are mesophilic.

PSYCHROPHILESPrefer cold temperatures. They thrive

in cold ocean water. At high altitudes, algae (often pink) can be seen living on snow.

Ironically, the optimum growth temperature of one group of psychropiles ( called psychrotrophs ) is at refrigerator temperature;

Examples, bread molds.

The term pH refers to the hydrogen ion concentration of the solution and thus the acidity or alkalinity of a solution.

Most organisms prefer a neutral growth medium (pH 7.0 – 7.4)

Acidophilic microbes or the acidophiles such as those that can live in the stomach and pickled foods prefer a pH of 2-5.

Fungi prefer acidic environments

Alkaliphiles pefer an alkaline environment pH greater than 8.5. examples of these are can be found living inside the intestine.

Osmotic pressure is the pressure that is exerted on a cell membrane by solutions both inside and outside the cell.

When cells are suspended in a solution, the ideal situation is that the pressure inside the cell is equal to the pressure of the solution outside the cell.

Substances dissolved in liquids are called solutes.

When the concentration of solute in the environment outside of a cell is greater that the concentration of solutes inside the cell, the solution in which the cell is suspended is said to be HYPERTONIC.

OSMOSIS is also defined as the movement of a solvent through a permeable membrane, from a solution having a higher concentration of solute..

If the cell is a human cell, such as red blood cell, the loss of the water causes the cell to shrink. This shrinkage is called CRENATION.

IF THE CELL IS A BACTERIAL CELL, having a rigid cell wall, the cell does not shrink. Instead, the cell membrane and cytoplasm shrink away from the cell wall. This condition is known as PLASMOLYSIS.

WHEN THE CONCENTRATION of the solutes outside the cell is less than the concentration of the solutes inside the cell, the solution in which the cell is suspended is said to be HYPOTONIC.

CELLS swell up, and sometimes burst, when place into hypotonic solution.

If the cell burst, the bursting is called hemolysis. If a bacterial cell is placed in a hypotonic solution, the cell may not burst. But the fluid pressure within the cell increases greatly.

This increased pressure in the cells having rigid cell walls such as plant cells and bacteria.

If the pressure becomes so great that the cell ruptures, the escape of cytoplasm from the cell is referred to as PLASMOPTYSIS.

WHEN THE CONCENTRATION OF solutes outside a cell equals the concentration of solutes inside the cell, the solution is said to be

ISOTONIC.

THOSE microbes that prefer salty environments, such as concentrated salt water found in great salt lake and salt evaporation ponds, are called HALOPHILIC.

ORGANISMS that do not prefer to live in a salty environments but capable of surviving there are called HALODURIC ORGANISMS.

MOST bacteria are not affected by minor changes in barometric pressure. Some thrive at normal atmospheric pressure, about 14.7 pounds per square inch or psi.

Others known as piezophiles, thrive deep in the oceans and in oil wells, where the atmospheric pressure is very high.

Microorganisms vary with respect to the type of the gaseous atmosphere that they require.

For example; some microbes (obligate aerobes) prefer the same atmosphere that humans do.

20-21% oxygen and 78-79% nitrogen with all other atmospheric gases combined representing less than 1%.

Obligate anaerobes are killed by the presence of oxygen.

To grow a particular microorganism in the laboratory, it is necessary, to provide the atmosphere that it requires.

Example; to obtain the maximum growth in the laboratory, capnophiles require increased concentrations of carbon dioxide. Usually from 5%-10% Carbon dioxide.

Technologists and technicians who work in clinical microbiology laboratories must be able to isolate microorganisms from clinical specimen, so that they can gather information that will enable identification of any pathogens that are present.

TODAY’S laboratories still use many of the same basic tools that were used in the past.

For example the use compound light microscope, petri dishes solid culture media, tubes containing liquid culture media, bunsen burner, and etc.

With respect to humans, the term growth refers to an increase in size;

for example; going from a tiny new born to a large adult.

Although bacteria do increase in size, before cell division, bacterial growth refers to an increase in the number of organisms rather than increase in their size.

Bacteria multiply by binary fission. The time it takes a particular bacterial species to undergo binary fission is called organism generation time.

When each bacteria cell reaches its optimum size, it divides by binary fission, into two daughter cell.

The media that are used in the microbiology laboratories to culture bacteria are referred to as ARTIFICIAL MEDIA OR SYNTHETIC MEDIA.—because they do not occur naturally; rather than they are prepared in the laboratory.

One way to classify media on whether the exact contents of the media are known.

A CHEMICALLY DEFINED MEDIUM is one which all ingredients are known.

A COMPLEX MEDIUM is one which all ingredients are not known.

Culture media can also be categorized as liquid or solid. Liquid media also known as broth are contained in tube and are thus often referred to as tubed media.

Solid media are prepared by adding agar to liquid media and pouring the media into tubes or petri dishes where the media solidifies.

An enriched medium is a broth or solid medium containing a rich supply of special nutrients that promotes the growth of fastidious organisms. Blood agar and chocolate agar are examples of enriched media.

It is used to discourage the growth of certain organisms without inhibiting growth of the organism being sought.

Allows one to readily differentiate among the various types of organisms that are growing on the medium.

In clinical microbiology laboratories, culture media are routinely inoculated with clinical specimens(i.e specimens that have been collected from patience suspected with infectious diseases).

ASEPTIC technique is practiced to prevent microbiology professionals from becoming infected and also prevent contamination of their work environment and of clinical specimens, cultures, and subcultures

AFTER media are inoculated, they must be incubated that contains the appropriate atmosphere and moisture level and is set to maintain the appropriate temperature.

The three types of incubators used in microbiology incubators are CO2 incubators, non- CO2 incubators and anaerobic incubators.

STERILIZATION– involves the destruction or elimination of all microbes, including cells, spores, and viruses.

DISINFECTION– involve the elimination of most of all pathogens.

PASTEURIZATION– it’s a method of disinfecting liquids.

DISINFECTANTS--- are chemicals used to disinfect inanimate objects such as bedside equipments and operating rooms. Disinfectants do not kill spores.

ANTISEPTICS--- are solutions used to disinfect skin and other living tissues.

SANITATION– Is the reduction of microbial populations to levels considered safe by public health standards, such as those applied in restaurants.

-----Disinfectant or antiseptic that kill microbes.

**agents having the suffix ―cidal‖ kill organisms, whereas agents having the suffix ―static‖ merely inhibit their growth and reproduction

Examples: Microbicidal, biocidal, sporicidal,fungicidal, germicidal, algicidal, bactericidal, viricidal.

--- is a drug or chemical that inhibits reproduction of microorganisms, but does not necessarily kill them.

A BACTERIOSTATIC AGENT is one that specifically inhibits the metabolism and reproduction of bacteria.

THE methods used to destroy or inhibit microbial life are either physical or chemical, and sometimes both types are used.

Commonly used in hospitals, clinics and laboratories to destroy or control pathogens include heat, the combination of heat and pressure, dessication, radiation, sonic disruption, and filtration.

HEAT--- is the most common type of sterilization for inanimate objects able to withstand high temperature.

COLD--- refrigeration cannot be relied upon to kill microorganisms; it merely slows down their metabolism and their rate of growth.

DESSICATION—drying process.

RADIATION– pertains to the use of rays in order to inhibit the growth of microorganisms.

ULTRASONIC WAVES– are used frequently as a means of cleaning delicate equipment.

FILTRATION—used to filter or separate cells, larger viruses, bacteria and certain microorganisms from the liquid or gases on which they are suspended.

CHEMICAL DISINFECTIONS refers to the use of chemical agents to inhibit the growth of pathogens either temporarily or permanently..

Various factors affect the efficiency or effectiveness of a disinfectant.

1. Prior cleaning of the object or surface to be disinfected.

2. The organic load that is present on the materials being treated.

3. The concentration of the disinfectant.

4. The bioburden

Some disinfectants (e.g, surface active soaps and detergents, alcohols, phenolic compounds) target and destroy cell membranes.

Others (e.g, halogens, hydrogen peroxide, salts of heavy metals, formaldehyde, ethylene oxide) destroy enzymes and structural proteins.

Others also attack cell walls or nucleic acids.

*antimicrobial chemical agents that can safely be applied to skin are called antiseptics.

THANKS FOR LISTENING

Exitos!!!