Chapter 20 Medical Microbiology

– is the scientific study of microorganisms and their activities.

-Microorganisms are tiny living plants and animals that cannot be seen by the naked eye, but must be viewed under a microscope.

-Microorganisms are ubiquitous; they are found almost everywhere– in the air, in food and water, in the soil, and in association with plants, animals, and human life.

-When a pathogen infects a host, it often produces a set of symptoms peculiar to that disease.

-The M.A must be alert to all symptoms that the pt describes and must relay this information to the physician through careful and concise charting of these symptoms in the pt’s medical record.

-Every individual has normal flora
-Normal flora- consists of the harmless microorganisms that normally reside in many parts of the body but do not cause disease.

-Mucous membrane
the surface of the skin; the gastrointestinal tract, and parts of the respiratory and genitourinary tracts all have an abundant normal flora.

– Invasion of the body by pathogenic microorganisms is known as:

incubation period
during this time, the pathogen is growing and multiplying.

prodromal period
is a short period in which the first symptoms that indicate an approaching disease occur.

acute period
is when the disease is at peak and symptoms are fully developed.

decline period
is when symptoms of the disease begin to subside.

convalescent period
is the stage in which the patient regains strength and returns to a state of good health.

Bacteria are known as microscopic single- celled organisms

The discovery of antibiotics has helped immensely in combating and controlling bacterial infections. Antibiotics are not effective against viral infection.

Staphylococcus aureus
is commonly associated with pathologic conditions such as boils, carbuncles, pimples, impetigo, abscesses

Streptococci are round bacteria that grow in chains before the advent of antibiotics, streptococcal infections were a major cause of human death.

Diplococci are round bacteria that grow in pairs. Pneumonia, gonorrhea, and meningitis are infectious diseases caused by diplococci.

Bacilli are rod- shaped bacteria that are frequently found in the soil and air. Some bacilli are able to form spores, a characteristic that enables them to resist adverse conditions such as heat and disinfectants.
Diseases caused by bacilli include botulism, tetanus, gas gangrene, gastroenteritis produced by Salmonella food poisoning, typhoid fever, pertussis ( whooping cough), bacillary dysentery, diphtheria, tuberculosis, leprosy, and plaque.

Escherichia coli
is a species of bacillus that is found among the normal flora of the large intestine in enormous numbers. It is normally a harmless bacterium; however, if it enters the urinary tract as a result of lowered resistance, poor hygiene practices, or both, it may cause a urinary tract infection.

Treponema palidum a spirochete, is the causative agent of syphilis.

Virus are the smallest living organisms. They are so small that an electron microscope must be used to view them.

Many kinds of microscopes are available, but the type used most often for office laboratory work is the compound microscope.
The compound microscope consists of a two-lens system, and the magnification of one system is increased by the other. A source of bright light is required for proper illumination of the object to be viewed.

Two adjustment knobs are used to bring the specimen into focus: the coarse adjustment knob and the fine adjustment knob.
– The coarse adjustment is used first to obtain an approximate focus quickly.
-The fine adjustment is then used to obtain the precise focusing necessary to produce a sharp, clear image.

The lower power objective is used for the initial focusing and light adjustment of the microscope. The lower power objective also is used for the initial observation and scanning requirements needed for most microscopic work.
The higher power objective is used for a more thorough study, such as observing cells in greater detail.

The oil immersion objective provides the highest magnification and is used to view very small structures or the detail of larger structures, such as microorganisms and blood cells.

These guidelines should be followed to care for the microscope properly:
– Always carry the microscope with two hands.
– Always handle the microscope in such a way that your fingers do not touch the lenses
– When it is not in use, keep the microscope covered with its plastic dust cover and stored in a case

A specimen is a small sample or part taken from the body to represent the whole.
– The medical assistant is often responsible for collecting specimens from certain areas of the body, such as the throat, nose, and wounds.

In most instances, a sterile swab is used to collect the specimen. A SWAB is a small piece of cotton wrapped around the end of a slender wooden or plastic stick. It is passed across a body surface or opening to obtain a specimen for micro biologic analysis.
All supplies used to obtain specimen must be sterile.

When obtaining a throat specimen, the swab should not be allowed to touch the inside of the mouth.

If the medical asst accidentally touches some of the material in the speicemen, the area of contact should be washed immediately and thoroughly with soap and water. If the specimen comes in contact with the work table, the table should be cleaned immediately with soap and water, followed by a suitable disinfectant, such as phenol.
Delay in processing the specimen may cause the death of pathogens or overgrowth of the specimen by microorganism.

The specimen is obtained by inserting the swab into the area of the wound that contains the most drainage and gently rotating the swab from side to side to allow it to absorb completely any microorganisms.

Blood agar is one of the most frequently used solid culture media. Its prepared by adding sheep blood to a substance known as agar; which is transport and colorless.
Blood added to the agar provides nutrients that support the growth of a variety of bacteria.

Culture media must be stored in the refrigerator and warmed to room temperature before use. A cold culture medium must not be used because the cold temperature results in the death of microorganisms placed on it.

A petri plate is frequently used to hold solid culture medium. The plate consists of a shallow circular dish made of glass or clear plastic with a cover, the diameter of which is greater than that of a base.

Petri plates allow examination of a culture while preventing microorganisms from entering or escaping.

The most common streptococcal condition is streptococcal sore throat, or streptococcal pharyngitis which primarily affects children and young adults.

Most tests require only 4 to 10 minutes to process; diagnosis can often be made and antibiotics prescribed, if necessary, before the patient leaves the office.

The physician may request not only that the laboratory identify the infecting pathogen, but also that a sensitivity test be performed on it to determine the best antibiotic to treat the condition.
A sensitivity test determines the susceptibility of pathogenic bacteria to various antibiotics; only the growth of the infectious pathogen is desired on the culture– is called C & S.

Gram stain allows the observer to view directly the size, shape, and growth patterns of the bacteria.
Gram stain is based on the fact that when treated with crystal violet dye, cerain bacteria permanently retain this dye after undergoing a decolorization process. These bacteria exhibit a purple color when viewed under the microscope and are known as gram-positive bacteria. Other bacteria are unable to retain this dye after being decolorized and become colorless.

Preparing a Smear
Principle: The specimen may contain pathogens that are capable of infecting the medical assistant; it is important to wear gloves. A rolling motion is used to deposit the maximal amount of material possible on the slide.

A mass of bacteria growing on a solid culture medium that have arisen from the multiplication of a single bacterium.

Capable of being transmitted directly or indirectly from one person to another.

Culture Medium
A mixture of nutrients on which microorganisms are grown in the laboratory.

A test result denoting that a condition is absent when it is actually present.

A test result denoting that a condition is present when it is actually absent.

In microbiology, the act of placing a culture in a chamber(incubator) that provides optimal growth requirements for the multiplication of the organisms, such as the proper temperature, humidity, and darkness.

The scientific study of microorganisms and their activities.

Mucous Membrane
A membrane lining body passages or cavities that open to the outside.

A morbid(secondary) condition occurring as a result of a less serious primary infection.

A material spread on a slide for microscopic examination.

A small sample or part taken from the body to show the nature of the whole.

In microbiology, the process of inoculating a culture to provide for the growth of colonies on the surface of a solid medium. Streaking is accomplished by skimming a wire inoculating loop that contains the specimen across the surface of the medium, using a back-and-forth motion.

Easily affected, lacking resistance.

Microbiology is the scientific study of microorganisms and their activity.

A disease that can be spread from one person to another is known as an infectious disease.

Droplet infection is the transfer of pathogens from a fine spray emitted from a person already infected with the disease.

Streptococci are round bacteria that grow in pairs.

Chickenpox is caused by a virus.

The course adjustment on a microscope is used to obtain precise focusing of an object.

The purpose of transport media is to provide nutrients for the multiplication of the specimen.

A throat specimen should be collected from the tonsillar area and posterior pharynx.

A wet mount is used to examine microorganisms in the living state.

A smear is material spread on a slide for microscopic examination.

Microorganisms that reside in the body but do not cause disease are known as transient flora.

The invasion of the body by a pathogenic microorganisms is known as inflection.

The interval of time between the invasion by a pathogen and the first symptoms of disease is known as the prodromal period.

Staphylococcal infections usually result in pus formation.

E.Coli normally reside in the urinary tract.

The high-power objective has a magnification of 40x.

Examination of the urine sediment requires the use of the oil immersion objective.

A mixed culture contains two or more types of microorganisms.

The purpose of sensitivity testing is to identify the type of microorganism present.

When viewed under a microscope, gram-positive bacteria appear pink or red.

•This common occurring worm is acquired through contaminated food, water, and house dust, as well as human-to-human contact.
•Eggs are usually found on the infected person’s pajamas and bed linen. Children can easily infect the entire family through the bathtub, toilet seat, and bedclothes.
•They can easily stay viable for weeks. Infections and reinfections continue by wearing clothes or sleeping in the bed of an infected person, as well as handling infected pets.
•This is a very contagious organism.
•Symptoms also include poor appetite, teeth grinding, hyperactivity, nervousness, irritability, insomnia, bed wetting, stomach aches, nausea and vomiting. Sometimes anal area becomes infected with bacteria because of the constant scratching. Pinworms are also often found within the appendix and have been associated with acute and chronic inflammation.
•One way is to perform a Scotch tape test. The first thing in the morning pat the sticky side of the scotch tape around the childs’ anal opening. Fold the tape together with the smooth side out, the pinworm eggs will be viewable under a microscope.

Stages of Infections Disease
• 1. Healthy Individual: person is in a healthy state.
• 2. Infection: invasion and multiplying pathogenic microorganisms in the body.
• 3. Incubation Period: interval of time between the invasion by a pathogen, appearance of 1st symptom growing and multiplying.
• 4. Prodromal Period: short period in which the 1st indicate an approaching disease occur.
• 5. Acute Period: the disease is at its peak and symptoms are fully develope.
• 6. Decline Period: symptoms of the disease begin to subside.
• 7. Convalescent Period: the patient regains to a state of good health.

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