Chapter 24: Asepsis and Infection Control
Learning objectives
1. Explain the infection cycle.
Infectious agent: bacteria, viruses, fungi
o Bacteria: the most significant and most commonly observed infection-
causing agent
Shapes: spherical (cocci), rod shaped (bacilli), or corkscrew shaped
(spirochetes)
Gram+ : thick cell wall that resists decolorization (loss of color) and
are stained violet
Gram - : more complex cell walls and can be decolorized by alcohol.
Thus, gram-negative bacteria do not stain
Crucial when prescribing the most appropriate antibiotic therapy
because antibiotics are classified as specifically effective against only
gram-positive organisms or as broad spectrum and effective against
several groups of microorganisms
Aerobic (requires oxygen) vs. anaerobic
o Viruses: smallest; cause infections including the common cold and do not
respond to antibiotics; hep b&c, aids.
o Fungi: molds and yeasts, can cause infection and are present in the air, soil,
and water; athlete’s foot, ringworm, and yeast infections; parasites (malaria)
Reservoir: natural habitat of the organism
o Possible reservoirs for microorganisms:
Other people
Animals (rabies)
Soil
Food, water, milk
Inanimate objects
Portal of exit: point of escape for the organism
o In humans, common portals of exit include the respiratory, gastrointestinal,
and genitourinary tracts, as well as breaks in the skin. Blood and tissue can
also be portals of exit for pathogens.
Means of transmission:
o direct contact
o indirect contact: vector or fomite, such as equipment or countertops
o airborne route: cough, sneeze, talks
Portal of entry: point at which organisms enter a new host
o The skin and urinary, respiratory, and gastrointestinal tracts are common
portals of entry
Susceptible host: must overcome resistance mounted by host’s defenses
Factors affecting an organisms potential to produce disease:
o Number of organisms
, o Virulence (ability to cause disease)
o Competence of persons immune system
o Length and intimacy of contact between person and microorganism
ORGANISM RESERVOIR MEANS OF DISEASE
TRANSMISSION TRANSMITTED
Borrelia burgdorferi Ticks (sheep, cattle, deer, Contact (indirect-vectors) Lyme disease
mice)
Escherichia coli (E. coli) Feces Contact (direct/indirect) E. coli infection (Most common
Contaminated food or water manifestation is diarrhea)
Hepatitis B virus (HBV) Blood Contact (direct; indirect Hepatitis B
Feces possible, but unlikely)
Body fluids and excretions
Human immunodeficiency Blood Contact (direct) Acquired immunodeficiency
virus (HIV) Semen syndrome (AIDS)
Vaginal secretions
Breast milk
Mycobacterium Sputum (respiratory tract) Contact (airborne) Tuberculosis
tuberculosis (M.
tuberculosis [TB])
Salmonella Intestinal tracts of humans Contact (direct/indirect) Diarrheal illness
and other animals,
including birds
Staphylococcus aureus Skin surface Contact (direct/indirect) • Minor skin infections: Carbuncle,
Mouth boil, pimple, abscess
Nose • Respiratory infection
Throat • Endocarditis (infection of the
heart valves)
• Osteomyelitis (bone infection)
• Bacteremia (bloodstream
infections)
Organisms Capable of Causing Disease
A disease that is endemic (occurs with predictability in one specific region or
population) can appear in a different geographic location. For example, malaria that
is endemic in Africa
Which infection or disease may be spread by touching a contaminated inanimate article?
o Influenza
, 2. List the stages of an infection.
Incubation period: organisms growing and multiplying
Prodromal stage: person is most infections, vague and nonspecific signs of disease; lasts
several hours to several days
Full stage of illness: presence of specific signs and symptoms of disease
Convalescent period: recovery from the infection
The client is most infectious during the prodromal stage of the illness. Early signs and
symptoms of disease are present, but these are often vague and nonspecific, ranging from
fatigue and malaise to a low-grade fever. This period lasts from several hours to several
days. During this phase, the client often is unaware of being contagious. As a result, the
infection spreads. The incubation period is the interval between the pathogen’s invasion
of the body and the appearance of symptoms of infection. During this stage, the
organisms are growing and multiplying. The length of incubation may vary. The presence
of specific signs and symptoms indicates the full stage of illness. The type of infection
determines the length of the illness and the severity of the manifestations. The
convalescent period is the recovery period from the infection. Convalescence may vary
according to the severity of the infection and the client’s general condition. The signs and
symptoms disappear, and the person returns to a healthy state
Learning objectives
1. Explain the infection cycle.
Infectious agent: bacteria, viruses, fungi
o Bacteria: the most significant and most commonly observed infection-
causing agent
Shapes: spherical (cocci), rod shaped (bacilli), or corkscrew shaped
(spirochetes)
Gram+ : thick cell wall that resists decolorization (loss of color) and
are stained violet
Gram - : more complex cell walls and can be decolorized by alcohol.
Thus, gram-negative bacteria do not stain
Crucial when prescribing the most appropriate antibiotic therapy
because antibiotics are classified as specifically effective against only
gram-positive organisms or as broad spectrum and effective against
several groups of microorganisms
Aerobic (requires oxygen) vs. anaerobic
o Viruses: smallest; cause infections including the common cold and do not
respond to antibiotics; hep b&c, aids.
o Fungi: molds and yeasts, can cause infection and are present in the air, soil,
and water; athlete’s foot, ringworm, and yeast infections; parasites (malaria)
Reservoir: natural habitat of the organism
o Possible reservoirs for microorganisms:
Other people
Animals (rabies)
Soil
Food, water, milk
Inanimate objects
Portal of exit: point of escape for the organism
o In humans, common portals of exit include the respiratory, gastrointestinal,
and genitourinary tracts, as well as breaks in the skin. Blood and tissue can
also be portals of exit for pathogens.
Means of transmission:
o direct contact
o indirect contact: vector or fomite, such as equipment or countertops
o airborne route: cough, sneeze, talks
Portal of entry: point at which organisms enter a new host
o The skin and urinary, respiratory, and gastrointestinal tracts are common
portals of entry
Susceptible host: must overcome resistance mounted by host’s defenses
Factors affecting an organisms potential to produce disease:
o Number of organisms
, o Virulence (ability to cause disease)
o Competence of persons immune system
o Length and intimacy of contact between person and microorganism
ORGANISM RESERVOIR MEANS OF DISEASE
TRANSMISSION TRANSMITTED
Borrelia burgdorferi Ticks (sheep, cattle, deer, Contact (indirect-vectors) Lyme disease
mice)
Escherichia coli (E. coli) Feces Contact (direct/indirect) E. coli infection (Most common
Contaminated food or water manifestation is diarrhea)
Hepatitis B virus (HBV) Blood Contact (direct; indirect Hepatitis B
Feces possible, but unlikely)
Body fluids and excretions
Human immunodeficiency Blood Contact (direct) Acquired immunodeficiency
virus (HIV) Semen syndrome (AIDS)
Vaginal secretions
Breast milk
Mycobacterium Sputum (respiratory tract) Contact (airborne) Tuberculosis
tuberculosis (M.
tuberculosis [TB])
Salmonella Intestinal tracts of humans Contact (direct/indirect) Diarrheal illness
and other animals,
including birds
Staphylococcus aureus Skin surface Contact (direct/indirect) • Minor skin infections: Carbuncle,
Mouth boil, pimple, abscess
Nose • Respiratory infection
Throat • Endocarditis (infection of the
heart valves)
• Osteomyelitis (bone infection)
• Bacteremia (bloodstream
infections)
Organisms Capable of Causing Disease
A disease that is endemic (occurs with predictability in one specific region or
population) can appear in a different geographic location. For example, malaria that
is endemic in Africa
Which infection or disease may be spread by touching a contaminated inanimate article?
o Influenza
, 2. List the stages of an infection.
Incubation period: organisms growing and multiplying
Prodromal stage: person is most infections, vague and nonspecific signs of disease; lasts
several hours to several days
Full stage of illness: presence of specific signs and symptoms of disease
Convalescent period: recovery from the infection
The client is most infectious during the prodromal stage of the illness. Early signs and
symptoms of disease are present, but these are often vague and nonspecific, ranging from
fatigue and malaise to a low-grade fever. This period lasts from several hours to several
days. During this phase, the client often is unaware of being contagious. As a result, the
infection spreads. The incubation period is the interval between the pathogen’s invasion
of the body and the appearance of symptoms of infection. During this stage, the
organisms are growing and multiplying. The length of incubation may vary. The presence
of specific signs and symptoms indicates the full stage of illness. The type of infection
determines the length of the illness and the severity of the manifestations. The
convalescent period is the recovery period from the infection. Convalescence may vary
according to the severity of the infection and the client’s general condition. The signs and
symptoms disappear, and the person returns to a healthy state
