© 2009 the mcgraw-hill companies, inc. all rights reserved introduction to microbiology...

© 2009 The McGraw-Hill Companies, Inc. All rights reserved

Introduction to MicrobiologyIntroduction to MicrobiologyPowerPoint® presentation to accompany:

Medical AssistingThird Edition

Booth, Whicker, Wyman, Pugh, Thompson

46-2


Learning Outcomes

46.1 Define microbiology.

46.2 Describe how microorganisms cause disease.

46.3 Describe how microorganisms are classified and named.

46.4 Explain how viruses, bacteria, protozoans, fungi, and parasites differ and give examples of each.

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Learning Outcomes (cont.)

46.5 Describe the process involved in diagnosing an infection.

46.6 List general guidelines for obtaining specimens.

46.7 Describe how throat culture, urine, sputum, wound, and stool specimens are obtained.

46.8 Explain how to transport specimens to outside laboratories.

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46.9 Describe two techniques used in the direct examination of culture specimens.

46.10 Explain how to prepare and examine stained specimens.

46.11 Describe how to culture specimens in the medical office.

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46.12 Explain how cultures are interpreted.

46.13 Describe how to perform an antimicrobial sensitivity determination.

46.14 Explain how to implement quality control measures in the microbiology laboratory.

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Introduction Microorganisms

cause disease or infection Pathogenic in nature Displaced from their

natural environment

Medical assistant Identification of

microorganisms Proper collection

techniques Testing procedures Quality control

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Microbiology and the Role of the Medical Assistant Microbiology – study of microorganisms

(simple forms of life visible only with a microscope)

Microorganisms Normal flora Pathogenic

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Medical assistant Assists physician Obtains specimens Prepares specimens for direct examination Prepares specimens for transportation to

reference laboratory If office has a POL, performs microbiologic

procedures

Microbiology and the Role of the Medical Assistant (cont.)

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How Microorganisms Cause Disease Cause disease in variety of ways

Use nutrients needed by cells and tissues Damage cells directly Produce toxins

May remain localized or become systemic Transmission

Direct contact Indirect contact

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How Microorganisms Cause Disease (cont.)

Localized symptoms Swelling Pain Warmth Redness

Generalized symptoms Fever Tiredness Aches Weakness

Normal flora Provides a barrier Can cause an infection

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Apply Your Knowledge

1. What role does the medical assistant play in relation to microbiology?

ANSWER: The medical assistant may assist the physician in obtaining specimens, obtain specimens herself, prepare specimens for direct examination or transport to a reference laboratory, and possibly perform microbiologic procedures.

2. How do microorganisms cause disease?

ANSWER: Organisms cause disease by using nutrients needed by cells and tissues, damaging cells directly, or producing toxins.

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Classification and Naming of Microorganisms Classification by structure

Subcellular – DNA or RNA surrounded by a protein coat – viruses

Prokaryotic – simple cell structure with no nucleus or organelles – bacteria

Eukaryotic – complex cell structure with nucleus and specialized organelles – protozoans, fungi, parasites

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Standardized naming Genus

Category of biologic classification Example – Staphylococcus

Species of organism Represents a distinct type of microorganisms Examples – Staphylococcus aureus and

Staphylococcus epidermidis

Classification and Naming of Microorganisms (cont.)

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Describe the classifications of microorganisms and give an example of each.

ANSWER: Microorganisms are classified as:Subcellular organisms that have DNA or RNA surrounded by a protein coat – virusesProkaryotic organisms have a simple cell structure with no nucleus or organelles – bacteria Eukaryotic have a complex cell structure with nucleus and specialized organelles – protozoans, fungi, parasites

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Viruses Smallest known

infectious agents Subcellular

microorganism Have only nucleic acid

surrounded by a protein coat

Must live and grow in living cells of other organisms

Hepatitis virus

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Viruses (cont.) Illnesses caused by viruses

Colds Influenza Croup Hepatitis Warts

Vaccines are available for many viruses

AIDS Mumps Rubella Measles Herpes

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Bacteria Single-celled prokaryotic organisms Reproduce rapidly Classification

Shape Ability to retain dyes Ability to grow

with / without air Biochemical reactions

Bacillus bacterial classification

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Bacteria: Classification and Identification

Shape Coccus – spherical, round, or ovoid

Bacillus – rod-shaped

Spirillum – spiral-shaped

Virbrio – comma-shaped Spirillum bacterial classification

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Ability to retain certain dyes Gram’s stain Acid-fast stain

Ability to grow in presence or absence of air Aerobes – grow best in the presence of oxygen Anaerobes – grow best in the absence of oxygen

Biochemical reactions

Bacteria: Classification and Identification (cont.)

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Special groups Mycobacteria – bacilli

with a cell wall that differs from most bacteria

Rickettsiae Very small Live and grow within

other living organisms such as mites and ticks

Chlamydiae Cell wall structure

differs from other bacteria

Live and grow within other living cells

Mycoplasmas – completely lack the rigid cell wall

Bacteria: Classification and Identification (cont.)

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Protozoans Single-celled eukaryotic organisms, larger than

bacteria

Found in soil and water

Illnesses Malaria Amebic dysentery Trichomoniasis vaginitis

Leading cause of death in developing countries

Protozoan Trichomonas

vaginalis

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Fungi Eukaryotic organisms

with rigid cell wall Yeasts

Single-celled Reproduce by budding

Molds Large, fuzzy,

multicelled organisms Produce spores

Superficial infections Athlete’s foot Ringworm Thrush

Can cause systemic infections

Yeast: a single-celled fungi

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Multicellular Parasites Organisms that live on or in another organism and

use it for nourishment

Parasitic worms Usually due to poor

sanitation Roundworms Flatworms Tapeworms

Parasitic insects Bite or burrow under

the skin Mosquitoes Ticks Lice mites

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Matching:

___ Yeast or mold A. Virus

___ Tapeworm / lice B. Bacteria

___ Classified by shape C. Protozoan

___ Subcellular organism D. Fungus

___ May be aerobic or anaerobic E. Multicellular parasite

___ Smallest known organism

___ Found in soil and water

E

ANSWER:

D

A

B

B

C

A

Very Good

!

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How Infections Are Diagnosed

Steps to diagnosis and treatment1. Examine the patient

Presumptive diagnosis May or may not need additional tests

2. Obtain specimen(s) Label properly Include presumptive diagnosis

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How Infections Are Diagnosed (cont.)

3. Examine specimen directly Wet mount Smear

4. Culture specimen Culture medium – contains nutrients Examine culture visually and microscopically

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How Infections Are Diagnosed (cont.)

5. Determine sensitivity to antibiotics

6. Treat the patient as ordered Antimicrobial – to kill

pathogen or suppress its growth

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What is the process for diagnosing an infection?

ANSWER: There are six steps for diagnosis and treatment of an infection:

1. Examine the patient 4. Culture the specimen

2. Obtain specimen(s) 5. Determine sensitivity

3. Examine specimen directly 6. Treat patient / appropriate antimicrobial

Super!

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Specimen Collection

Must be collected correctly If not, may not grow in

culture

Contaminants may be mistakenly identified

Patient may receive incorrect or harmful therapy

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Specimen Collection (cont.)

Devices Use appropriate collection

device or specimen container Sterile swabs – absorbent

material on the tip

Collection and transporting systems Sterile, self-contained Transport medium Aerobic or anaerobic

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Specimen Collection: Guidelines

Avoid causing harm, discomfort, or undue embarrassment

Collect from appropriate site

Obtain specimen at correct time

Use appropriate devices

Obtain sufficient quantity of specimen

Obtain specimen prior to the start of antimicrobial therapy

Label correctly

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Throat culture specimens Swab back of throat in the area

of the tonsils Avoid touching any structures

in the mouth Prepare culture plate or

prepare correctly for transport to laboratory

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Urine specimen Clean-catch

midstream to minimize contaminants

Process within 60 minutes or refrigerate

Sputum specimen Specimen from

lungs Avoid

contaminating specimen with saliva

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Wound specimen Swab wound or

lesion Do not touch

outside of wound

Stool Specimens Technique varies

Bacterial infection Protozoal or

parasitic infection

Instruct patient in correct collection procedure

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What are the general guidelines for specimen collection?

ANSWER: They are to avoid causing harm, discomfort, or undue embarrassment; collect from appropriate site; obtain specimen at correct time; use appropriate collection devices; obtain sufficient quantity of specimen; obtain specimen prior to the start of antimicrobial therapy; and label specimen correctly.

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Transporting Specimens to an Outside Laboratory Many offices send cultures to an outside lab

Three main objectives Follow proper collection

procedures and proper collection device

Prevent deterioration of specimen

Protect anyone handling specimen

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Transporting Specimens to an Outside Laboratory (cont.)

Regularly scheduled daily pickups by the lab

Most reliable

As-needed pickup by the lab

Through the mail Follow U.S. Public Health Service

regulations Etiologic Agent label

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What are the objectives for transporting a specimen to an outside laboratory?

ANSWER: They are to follow proper collection procedures and use proper collection device, prevent deterioration of the specimen during transport, and protect anyone that will handle specimen from exposure.

Impressive!

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Direct Examination of Specimens Enables physician to initiate treatment immediately

Wet mounts NaCl mixed with

specimen of glass slide Presence of pathogen

and movement of microorganism

Potassium hydroxide (KOH) mounts Used if a fungal

infection of the skin, nails, or hair is suspected

KOH dissolves keratin that can mask presence of a fungus

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Preparation and Examination of Stained Specimens Quick, tentative

diagnosis Differentiation

between types of infections

Gram’s stain Moderate-

complexity test Bacteria either

retain or lose purple color Gram-positive

bacteria Gram-negative

bacteria

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Culturing Specimens in the Medical Office More common to send

specimens for culture to outside labs

Culturing involves placing a sample of specimen on a culture medium Medium – nutrients Place in incubator for growth – colony develops

as microorganism multiplies

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1. What are the methods for preparing a slide for direct examination by the physician?

ANSWER: They are wet mount and KOH mount.

2. How does the examination of stained specimens facilitate patient care?

ANSWER: Stained specimens enable the physician to provide a quick, tentative diagnosis and differentiate between types of infections.

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3. What is the process for culturing a specimen?

ANSWER: The culture medium is inoculated with the specimen and placed in an incubator to promote growth of the organism on the culture medium.

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Culturing Specimens (cont.)

Culture media Liquid, semisolid, or

solid forms Contains agar Selective or nonselective

Special culture units Rapid urine culture – Uricult Also available for throat, vaginal, and blood

specimens

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Inoculating a culture plate Transfer some of the specimen onto a culture

plate Label the plate correctly Qualitative analysis – determination of type of

pathogen Quantitative analysis – number of bacteria

present in sample

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Incubating culture plates 35 to 37º C for 24 to 78 hours Agar side up

Interpreting cultures Requires skill and practice Characteristics of colonies Relative number Changes to media around colonies

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Determining Antimicrobial Sensitivity An outside lab

reports Sensitive – no

growth Intermediate – little

growth Resistant –

overgrown

Procedure Filter paper containing

antimicrobial agents placed on inoculated agar plate

Incubated for 24 hours Evaluate effectiveness

of agent

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1. What is the difference between selective and nonselective culture media?

ANSWER: Selective culture media allows the growth of only certain kinds of bacteria. Unselective culture media support the growth of most organisms.

2. The office received a culture sensitivity report on a bacteria that said it was resistant to an antimicrobial. What does this mean?

ANSWER: It means that the bacteria was not killed by the antimicrobial and that there was an overgrowth of the bacteria.

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Quality Control in the Medical Office Ongoing evaluation

of the quality of medical care being provided

Objective means to define, monitor, and correct potential problems

Routine evaluation All media, staining

solutions, and reagents

Equipment

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Quality Control: Impact of CLIA ’88 Appropriate policies and procedures

Proper documentation Lab policies and procedures Materials Personnel qualifications and training

Participation in proficiency testing program

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What is the purpose of a quality control program in the medical office?

ANSWER: To provide an ongoing evaluation of the quality of medical care provided and to provide an objective means to define, monitor, and correct potential problems.

Very Good!

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In Summary Microorganisms are a major cause of disease

Medical assistant Collects specimens Processes or transports specimens

Quality control – ensures quality medical care

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End of Chapter

Each organism's environment, for the most part, consists of other organisms.

~ Kevin Kelly

© 2009 the mcgraw-hill companies, inc. all rights reserved introduction to microbiology...

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