Lecture Clinical procedures for medical assisting (4/e): Chapter 15 – Booth, Whicker, Wyman

Chapter 15 - Introduction to microbiology. The objectives of this chapter are: Define microbiology; describe how microorganisms cause disease; describe how microorganisms are classified and named; explain how viruses, bacteria, protozoans, fungi, and parasites differ and give examples of each;...

Introduction to

Microbiology

Learning Outcomes

15.1 Define microbiology.

15.2 Describe how microorganisms cause disease.

15.3 Describe how microorganisms are classified

and named.

15.4 Explain how viruses, bacteria, protozoans,

fungi, and parasites differ and give examples

of each

Learning Outcomes (cont.)

15.5 Describe the process involved in diagnosing

an infection.

15.6 List general guidelines for obtaining

specimens

15.7 Describe how throat culture, urine, sputum,

wound, and stool specimens are obtained.

15.8 Explain how to transport specimens to outside

laboratories.

Learning Outcomes (cont.)

15.9 Describe two techniques used in the direct

examination of culture specimens.

15.10Explain how to prepare and examine stained

specimens.

15.11Describe how to culture specimens in the

medical office

Learning Outcomes (cont.)

15.12Explain how cultures are interpreted.

15.13Describe how to perform an antimicrobial

sensitivity determination.

15.14Explain how to implement quality control

measures in the microbiology laboratory

their natural environment

• Medical assistant

– Identification of microorganisms – Proper collection techniques

– Testing procedures – Quality control

Assistant

(simple forms of life visible only with a

microscope)

• Microorganisms

– Normal flora – Pathogenic

Assistant (cont.)

• 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

How Microorganisms Cause Disease

• Cause disease in variety of ways

– Use nutrients needed by cells and tissues

– Damage cells directly

How Microorganisms Cause Disease (cont.)

– Tiredness– Aches

– Weakness

• Normal flora

– Provides a barrier– Can cause an infection

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.

Classification and Naming of Microorganisms

– Eukaryotic – complex cell structure with nucleus and

specialized organelles – protozoans, fungi, parasites

• Represents a distinct type of microorganisms

• Examples – Staphylococcus aureus and

Staphylococcus epidermidis

Apply Your Knowledge

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 – viruses

Prokaryotic 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

– Must live and grow in

living cells of other

Bacterial Classification and Identification

Bacterial Classification and Identification (cont.)

• 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

– 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

• Superficial infections

– Athlete’s foot– Ringworm– Thrush

• Can cause systemic

Yeasts: celled fungi

– Lice – Mites

Apply Your Knowledge

Matching:

_ 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

How Infections Are Diagnosed

• Steps to diagnosis and treatment

1 Examine the patient

How Infections Are Diagnosed (cont.)

3 Examine specimen directly

• Wet mount

• Smear

4 Culture specimen

 Culture medium – contains nutrients

 Examine culture visually and microscopically

How Infections Are Diagnosed (cont.)

5 Determine sensitivity to antibiotics

6 Treat the patient as ordered

suppress its growth

Apply Your Knowledge

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!

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

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

Guidelines for Specimen Collection

• Avoid causing harm,

• Obtain specimen prior

to the start of antimicrobial therapy

• Label correctly

Specimen Collection (cont.)

• 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

Specimen Collection (cont.)

• Urine specimen

– Clean-catch

midstream to minimize

contaminants – Process within 60

minutes or refrigerate

• Sputum specimen

– Specimen from lungs

– Avoid contaminating specimen with saliva

Specimen Collection (cont.)

• Wound specimen

– Swab wound or

lesion – Do not touch

Apply Your Knowledge

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.

Outside Laboratory

• Many offices send cultures to an outside

lab

• Three main objectives

– Follow proper collection

procedures and use proper collection device

– Prevent deterioration of

specimen – Protect anyone handling

Laboratory (cont.)

• Regularly scheduled daily pickups by the lab

• As-needed pickup by the lab

• Through the mail

– Follow U.S Public Health Service regulations

– Etiologic Agent label

Apply Your Knowledge

What are the objectives for transporting a specimen

to an outside laboratory?

ANSWER: They are to follow proper collection procedures

and use the proper collection device, prevent deterioration of

the specimen during transport, and protect anyone that will

handle the specimen from exposure.

Impressive!

Direct Examination of Specimens

– 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

• Gram-positive

bacteria

• Gram-negative

bacteria

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

Apply Your Knowledge

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.

Apply Your Knowledge

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.

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

Culturing Specimens (cont.)

• 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

Culturing Specimens (cont.)

• 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

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

Apply Your Knowledge

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.

Quality Control in the Medical Office

 Equipment

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

Apply Your Knowledge

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!

In Summary

15.1 Microbiology is the study of microorganisms, which

are simple life forms that are microscopic and are commonly made up of a single cell

15.2 Microorganisms can cause disease by using up

nutrients or other materials needed by the cells and tissues they invade, damaging body cells, and

producing toxins

15.3 Microorganisms are classified on the basis of their

structure and are named in a standard way, using the genus to which the microorganism belongs and the particular species of the organism

In Summary (cont.)

15.4 Viruses, bacteria, protozoans, fungi, and parasites

differ in the following ways: viruses are among the smallest known infectious agents; bacteria are single-celled prokaryotic organisms that reproduce very

quickly; protozoans are single-celled eukaryotic organisms that are generally much larger than bacteria; and fungi are eukaryotic organisms that have a rigid cell wall

15.5 The steps involved in diagnosing an infection are to

examine the patient, obtain specimens, examine the specimen, culture the specimen, and determine the

In Summary (cont.)

15.6 The general guidelines for obtaining specimens are:

obtain the specimen with care; collect the material from a site; obtain the specimen at the proper time;

use appropriate collection devices; obtain a sufficient quantity of the specimen; and obtain the specimen before antimicrobial therapy begins

15.7 Throat culture, urine, sputum, wound, and stool

specimens are obtained in very specific ways It is important to follow office procedures when obtaining specimens for testing purposes

In Summary (cont.)

15.8 When transporting specimens to outside laboratories,

the medical assistant should follow proper collection techniques using specific containers provided by the laboratory, maintain the samples in a state as close to their original as possible, and protect anyone who

handles a specimen container from exposure to potentially infectious material

15.9 Direct examination of culture specimens is

accomplished in two ways: wet mounts and KOH mounts

In Summary (cont.)

15.10 To prepare a stained specimen, the medical

assistant must first prepare a smear, fix the sample

to the slide so that it does not wash off during the staining process, and follow a specific staining procedure The sample is then observed under a microscope for certain characteristics

15.11 To culture a specimen, the medical assistant should

place a sample of the specimen on or in a specialized culture medium and allow it to grow in an incubator for 24 to 48 hours

In Summary (cont.)

15.12 The process of interpreting a culture involves noting

the characteristics and relative numbers of the colonies growing on the agar as well as any changes

in the media surrounding the colonies

15.13 Performing an antimicrobial sensitivity test involves

taking a sample of the isolated pathogen, suspending

it in a small amount of liquid medium, and streaking it evenly on the surface of a culture plate Small disks

of filter paper containing various antimicrobial agents are placed on top of the inoculated agar plate and the plate is then incubated at 37°C, and the results are

In Summary (cont.)

15.14 To implement a quality control program in a

microbiology laboratory, the medical assistant should develop an up-to-date procedures manual; monitor laboratory equipment; monitor media, supplies, and reagents; ensure that the laboratory personnel are qualified; and ensure adequate space

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

~ Kevin Kelly

End of Chapter 15