Unit 12

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Unit 12

Infection


Objectives

• Spell and define terms.• Identify the most common microbes and

describe some of their characteristics.• List the links in the chain of infection.• List the ways that infectious diseases

are spread.


Objectives

• Define spores and explain how spores differ from other pathogens.

• Name five serious infectious diseases.• Identify the causes of several important

infectious diseases.• Describe common treatments for

infectious disease.


Objectives

• List natural body defenses against infections.

• Explain why patients are at risk for infections.


Introduction

• Humans are surrounded by a world of tiny organisms

• These beings cannot be seen with the naked eye

• They make their presence known only by their effects– Same way we become aware of the wind


Microbes

• There are many different types of microbes– Many of which are pathogenic to humans


Bacteria

• Simple one-celled microbes • Named according to their shapes and

arrangement • Cause infections in the skin, respiratory

tract, urinary tract, and bloodstream


Fungi

• Two groups of fungi are most commonly associated with infection in humans – Yeasts– Molds


Viruses

• Smallest microbe • Has a variety of shapes


Protozoa

• Simple one-celled organisms • Live on living matter


The Chain of Infection

• Infections occur when certain conditions exist

• Conditions are called the chain of infection

• Refer to Figure 12-3A


The Chain of Infection


Chain of Infection

• Breaking one link in the chain of infection is all that is needed to prevent the spread of disease

• Refer to Figure 12-3B


Chain of Infection


Causative Agent

• Microorganism that can produce the disease process in humans


Susceptible Host

• Person who can become infected with a pathogen

• Unable to resist a microorganism invading the body, multiplying, and causing infection


Susceptible Host

• Host is susceptible to the disease– Lacks immunity or physical resistance to

overcome the invasion of pathogens


Reservoir

• Where pathogens live, multiply, and survive

• May or may not multiply in the reservoir


Reservoir

• Source – Person, animal, or substance from which

the infectious agent passes to the host– May also be an inanimate object, such as

water, a sink or counter top, or doorknob


Source

• Reservoir may be the same as the source or different from the source – Reservoir is where the pathogen lives or

resides– Source is the site from which the pathogen

is transmitted to a susceptible host• Directly or indirectly through an object or in the

environment


Source

• This distinction is important when deciding the types of precautions and control measures to use to prevent further spread


Portals of Entry

• Where organisms enter the body are called portals of entry


Portals of Entry

• Portals – Body openings, mucous membranes, and

breaks in the skin • Portals also result from tubes placed in

body– Urinary catheters, or from punctures

produced by invasive procedures such as intravenous fluids


Portals of Exit

• Infectious organisms leave the reservoir of the human host through body secretions or portals of exit

• Portal provides a way for a pathogen to leave the reservoir– Leaving nose or mouth on a sneeze or

cough


Mode of Transmission

• Mode or method of transmission:– Method by which the infectious agent

passes from a source to the host– May be transmitted by more than one route


Mode of Transmission• Methods of transmission are:

– Direct contact– Indirect contact– Airborne and droplet spread– Fomites (a method of indirect contact)– Vectors– Common vehicles


Types of Infections

• Infections can be:– Local– Generalized– Systemic


Body Flora

• Different microbes live on our body surfaces– Microbes are called the normal body flora– Flora are not the same in all body areas


Body Flora

• They are not harmful in the area in which they normally reside– But may cause infection if they are moved

to another area of the body


How PathogensAffect the Body

• Potential for infection depends on the risk factors listed previously

• Two major factors are:– Susceptibility of the host– Amount of infectious agent that finds a

portal of entry into the host


Body Defenses • The body has some natural defenses to

protect itself from infections• There are several natural external

defenses• The most important of these is the skin


Immunity • Immunity is the ability to fight off

disease caused by microbes


Immunizations

• Artificial defenses called immunizations protect against specific pathogens

• Immunization is provided by vaccines


Immunosuppression

• Occurs when the body’s immune system is inadequate– Fails to respond to the challenge of

infectious disease organisms that it normally would fight successfully


Serious Infections in Health Care Facilities

• Serious bacterial and viral infections are increasing in health care facilities as well as in the general public


Bacterial Infections• Bacteria are often the cause of serious

skin, respiratory, urinary, and gastrointestinal infections in patients

• If a physician suspects that a patient has a bacterial infection:– Culture and sensitivity test may be ordered


MRSA and VRE• Two groups of organisms have become

resistant to two powerful antibiotics– Methicillin and vancomycin

• These organisms are:– Methicillin-resistant Staphylococcus aureus

(MRSA)– Vancomycin-resistant enterococci (VRE)


Tuberculosis• Before the development of antibiotics:

– Tuberculosis was a widespread disease with a high fatality rate

• In the 1950s:– Use of antibiotics effective against

tuberculosis caused deaths to drop sharply


Escherichia Coli 0157:H7

• You have learned that Escherichia coli can cause serious problems outside the intestinal tract.

• E. coli 0157:H7– Caused outbreaks resulting in serious

illness and death


Pseudomembranous Colitis• Many bacteria live in the bowel of a

healthy person• Most of them are harmless

– Some friendly bacteria help with digestion• A few of these have the potential to be

troublemakers if they get out of control


Viral Infections

• Viral infections include:– Shingles– Influenza– Hepatitis– Acquired immune deficiency syndrome

(AIDS)


Other Important Infections• Infection caused by fungi:

– Coccidioidomycosis• Infection caused by protozoa:

– Giardiasis– Cryptosporidiosis


Spores

• Microscopic reproductive bodies are responsible for the spread of some diseases

• They can survive in a dormant form until conditions are ideal for reproduction

• Spores will multiply and continue to spread infection

• They are very difficult to eliminate


Spores

• Avoid alcohol products for cleansing hands if a patient has a disease spread by spores:– Alcohol will not kill spores– Mechanical action of washing with soap

and water loosens spores and washes them down the drain


Severe Acute Respiratory Syndrome

• SARS is a highly contagious viral respiratory illness caused by a coronavirus

• Special isolation precautions are required

• Much remains to be learned about SARS


Parasites• Survive by feeding off another human or

animal– Head lice are parasites that spread by

direct and indirect contact– Scabies is a skin disease caused by a

parasite called a mite– Mites are microscopic organisms that

cannot be seen with the eye


Parasites• Both head lice and scabies are known

for spreading rapidly through health care facilities


Bedbugs

• Are real parasites– Most people believe they are imaginary– Survive in hot and cold environments and

live up to a year without eating


Bedbugs

• There is no recorded incidence of disease as a result of bedbugs, although it is suspected

• Bites cause a painful rash on the skin • Bedbugs feed at night


Bedbugs

• Bedbugs hide in or around the bed, including: – In the mattress– Behind the headboard– Behind the baseboard on the wall


Bioterrorism

• Use of biological agents– Pathogenic organisms or agricultural pests,

for terrorist purposes


Smallpox• Smallpox is a serious viral infection that

is sometimes fatal• Disease emerged thousands of years

ago but was eliminated during the twentieth century


Outbreak of Infectious Disease in a Health Care Facility

• An outbreak of an infection in a health care facility can be serious for all patients

• Unless steps are taken immediately– Infection can spread rapidly

Unit 12

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