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Chapter 3

Pre-Study Session Quiz

APIC DFW Professional

Advancement Committee

1. A patient has VRE from a rectal swab but does

not have any signs and symptoms of being sick. This

patient has a VRE _______.

a. Infection

b. Colonization

c. Contamination

d. None of the above

2. Which part of the chain of infection does a

sneeze represent?

a. Reservoir of the agent

b. Portal of exit of the agent from the reservoir

c. Mode of transmission of the agent

d. Portal of entry into host

3. What is the name for a substance that prevents water-

soluble elements such as antibiotics and disinfectants

from reaching pathogens?

a. Cell wall

b. Biofilm

c. Sludge

d. Biocarbon

Chapter 3: Identification of

Infectious Disease Processes

Prepared by:

APIC DFW Professional Advancement Committee

Affiliated Resources for Study

(22 questions)

• APIC Text Chapters 21-26, Chapters 70-99

• Ready Reference for Microbes

• Control of Communicable Diseases Manual

• The Infection Preventionists’ Guide to the Lab

Colonization, Infection, and Contamination

• Colonization: presence of microorganisms in or on a host with growth but

without tissue invasion or damage

• Infection: entry of an infectious agent in the tissues of the host that

multiplies and creates symptoms

• Contamination: presence of microorganisms on inanimate objects (i.e.,

clothing, surgical instruments), on skin or in substances (i.e., water, food,

milk)

• Causative agent—microbial organism with the ability to cause

disease

• Reservoir of the agent—where organism can survive but may

or may not multiply (Humans, animals, insects, food,

environment: Hep B on a hemodialysis machine, healthcare

workers)

• Portal of exit of the agent from the reservoir—provides a

way for a microorganism to leave the reservoir (respiratory:

nose, mouth; GI: feces; skin; inanimate objects)

• Mode of transmission of the agent—method of transfer by

which the organism moves or is carried from one place to

another (hands, air/droplets, objects)

• Portal of entry into host—an opening allowing the

microorganism to enter the host (mouth, nose, indwelling

devices, contaminated food/water, wounds)

• Susceptible host—microorganism invading the body, then

multiplying, and resulting in infection. The host is susceptible to

the disease, lacking immunity of physical resistance to

overcome the invasion by the pathogenic micoorganism

Risk Factors for Infection Transmission:

Transmissibility of Organism

• Virulence

• Infectivity

• Pathogenicity

• Duration of Exposure

• Size of Inoculum

a. Ability to cause disease

b. Ability to enter tissues

c. Length of time the person is

exposed to the organism

d. Ability to grow and multiply

e. The number of organisms needed

to cause disease

Match the term on the left to the definition on the right.

Essential Knowledge for IPs

• Consider that an almost invisible crack in equipment such as an endoscope could

contain numerous bacteria, such as Clostridium difficile, that could enter a patient.

• The reproduction rate of many species of bacteria is as astounding as their small size.

About 30 minutes are required for a bacterium of some species to divide into two

bacteria and another 30 minutes for the two to divide into four, etc.

• Some bacteria, for example, Clostridium, can transform into endospores that can

survive in water heated to well above boiling temperature, are resistant to drying, are

resistant to harsh chemicals, and can be dispersed in dust. These characteristics make

cleaning medical equipment and facilities difficult tasks that must be done thoroughly.

Diagnostics and Laboratory Reports

• Direct examination: gram stain, histology

• Detection of antigen/antibody reaction: varicella, MMR

• Molecular Diagnostic Testing: PCR for TB

• Test for Infectious Process: CBC, urinalysis, CSF analysis

The Field of Microbiology

Microbiology

• The microbiology lab is an important partner in the practice of infection

prevention.

• Routine environmental monitoring generally not recommended

• Quality assurance

• Biologicals for sterilizers

• Monthly dialysis cultures

• Special environmental monitoring (epidemiological investigation)

Appropriate Practices for Specimen Collection,

Transportation, Handling, Storage

• Review Specimen Collection and Transport Chapter of the Infection Preventionists’ Guide to the Lab

• Specimen selection, collection, transportation of specimens to the diagnostic microbiology laboratory are essential parts in the accurate identification of microorganisms that cause infections

• All specimens must be transported within 2 hours of collection

• Specimens must be transported in a container designed to ensure survival of suspected agents

Appropriate Practices for Specimen Collection,

Transportation, Handling, Storage

• Materials for transport must be labeled properly, packaged, and protected

during transport

• Use leakproof specimen containers and transport them in sealable, leakproof

plastic bags

• Laboratories must have enforceable criteria for rejection of unsuitable

specimens.

Sensitivity vs. Specificity

• Sensitivity: a test to prove that a positive test is truly positive

• Specificity: a test to prove that a negative test is truly negative

Biofilm

• Attach to surfaces and can spread infection

• Contain cohabiting microorganisms which may be part of the host normal

flora.

• Can form on living or non living surfaces

• Prevents water-soluble elements such as antibiotics and disinfectants from

reaching pathogens

• Not culturable, necessitating newer nonculture lab techniques

Organisms and Medical Devices

Good Resources to Look At

• Table 70-4 Planktonic Organisms Associated with Medical Devices

• Table 70-6 Medical Biofilm Diseases

• Catheter removal could be the most effective treatment of choice for urinary

catheters; Central venous catheters may be more impractical depending on

the situation

Prophylactic, Empiric, and Therapeutic

Uses of Antimicrobials

• Prophylactic: antimicrobial given to prevent infection when there has been

potential exposure or when situation will involve potential risk for infection

• Empiric: antimicrobial therapy (usually broad spectrum) initiated when no

information about the causative agent is known, patient sufficiently ill to

warrant treatment before culture and sensitivity tests are available or site of

infection may indicate likely pathogen

• Therapeutic: pathogen directed

Correlate Clinical Signs & Symptoms with

Infectious Disease Processes

• Review APIC Text Chapters 70-99

• Additional Resources to Review:

• HICPAC Isolation Guidelines:

http://www.cdc.gov/hicpac/2007IP/2007isolationPrecautions.html

• APIC Text Chapter 29 Transmission Based Precautions (will cover more in Study Guide

Chapter 5)

http://www.cdc.gov/hicpac/2007IP/2007isolationPrecautions.html

Chapter 3

Post-Study Session Quiz

APIC DFW Professional

Advancement Committee

1. A patient has VRE from a rectal swab but does

not have any signs and symptoms of being sick. This

patient has a VRE _______.

a. Infection

b. Colonization

c. Contamination

d. None of the above

2. Which part of the chain of infection does a

sneeze represent?

a. Reservoir of the agent

b. Portal of exit of the agent from the reservoir

c. Mode of transmission of the agent

d. Portal of entry into host

3. What is the name for a substance that prevents

water-soluble elements such as antibiotics and

disinfectants from reaching pathogens?

a. Cell wall

b. Biofilm

c. Sludge

d. Biocarbon

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