HNN112 Study Guide - Final Guide: Bacteremia, Integumentary System, Immunosuppression
HNN112
INFECTION CONTROL
1
DEFINE MICRO-ORGANISM AND HEALTH CARE ASSOCIATED INFECTIONS
There are approximately 1400 micro-organisms known to be able to infect humans.
These are divided into several ategoies…
- Bacteria are by far the most common infection-causing micro-organisms. It can live and be
transported via air, water, food, soil, body tissues and fluids and inanimate objects.
- Viruses consist primarily of nucleic acid and therefore must enter living cells in order to reproduce.
Common virus families include the Rhinovirus, hepatitis, herpes and human immune-deficiency
virus (HIV).
- Fungi include yeast and moulds.
- Parasites live on other living organisms including protozoa.
- Prions are infective particles consisting of only proteins and responsible for a group of fatal
neurological disorders.
Many micro-organisms can cause sepsis, the development of the systemic inflammatory response
syndrome in the presence of infection.
An infection is an invasion of the body tissue by micro-organisms and their proliferation. These micro-
organisms are referred to as pathogens or infectious agents.
Infection occurs when newly introduced or resident micro-organisms succeed in invading part of the body
hee the host’s defee ehais are ineffective and the pathogen causes tissue damage, the infection
then becomes a disease.
Disease is a detectable alteration in normal tissue function.
Pathogenicity is the ability of micro-organisms existing in blood or body tissues to produce toxins that
damages healthy tissue. Micro-organisms causing disease in humans are referred to as pathogens.
An opportunistic pathogen causes disease only in susceptible individual.
A micro-organism varies in its virulence (their ability to produce disease).
Infectious agents capable of being transmitted from one individual through direct or indirect contact via a
vector or airborne route are called communicable agents, which lead to communicable diseases.
Non-communicable diseases are those that do not usually spread from an infected host to a healthy
person during normal contact, they require a mechanical transfer (e.g. tetanus).
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TYPES OF INFECTION
Local infections are limited to the specific part of the body where the micro-organisms remain.
If the micro-organisms spread and damage different parts of the body, it becomes a systemic infection.
Acute infections generally appear suddenly or last a short time. A chronic infection occurs slowly, or over a
very long period, lasting months or years.
Endogenous infections are caused by the micro-ogaiss aleady peset i idiidual’s ody atig.
Exogenous infections are caused micro-organisms from a source external to the individual.
HOSPITAL-ACQUIRED INFECTIONS/HEALTH CARE ASSOCIATED INFECTIONS (HAI)
HAI are classified as infections associated with the delivery of health care services in a health care facility.
Despite the precautions we take and all policies/procedures in place, infections remain a major health
problem within clinical settings and in the community. Infections are in fact more easily acquired in a
hospital eause a peso’s defee ehaiss ae iteupted o opoised.
They are also bought out into the community because of early discharges.
Each year there are 200,000 HAIs in Australia.
Staphylococcus aureus bacteraemia (SAB) is the most common cause of HA bloodstream infections and is
linked to the presence of an indwelling medical device like an IV line and urinary catheter.
C. Difficile is a common HAI causing significant morbidity and mortality.
IDENTIFY MODES OF TRANSMISSION
After a micro-organism leaves its source, it requires a means of transmission to reach another person or
host through a receptive portal of entry.
- Direct transmission: this involves immediate and direct transfer of micro-organisms from person to
person through touching, biting, kissing or sex. Droplet spread is included in this; sneezing,
coughing, spitting, singing or talking.
- Indirect transmission: this is vehicle-borne or vector-borne.
Vehicle-borne: a vehicle is any substance serving as an intermediate means to transport that
introduces an infectious agent into a susceptible host through a suitable portal of entry.
Vector-borne: a vector is an animal or flying or crawling insect serving as an intermediate means of
transporting infectious agent. Transmission can occur by injecting salivary fluid during biting or by
depositing faeces or other materials on the skin through the bite wound or on an area of
traumatised skin.
- Airborne transmission: this may involve droplets or dust, the residue of evaporated droplets
emitted by an infected host. The material is transmitted by air currents to a suitable entry, usually
the respiratory tract.
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