Mode of transmission
Vehicle: the of microorganisms by way of
vehicles, or contaminated items that transmit pathogens. Eg; food can carry salmonella, blood can carry hepatitis, HIV.
Droplet Transmission: occurs when the mucous membranes of
the nose, mouth, or conjunctiva are exposed to secretions of an infected person
who is coughing, sneezing or talking. Examples of infectious agents that are
transmitted via droplets include influenza virus and meningococcus.
Airborne transmission: occurs when fine particles are
suspended in the air for a longer time or when dust particles contain
pathogens.
Examples of infectious agents that are transmitted via the
airborne route include measles (rubeola) virus, chickenpox (varicella) virus
and M. tuberculosis.
Vector borne: vectors are biological or mechanical.
·
Biological
vectors are living creatures that carry pathogens, such as rats, insects, or
Birds Eg; Malaria.
·
Mechanical
vectors inanimate objects that are contaminated with infected body fluids.
Central line catheters, which are used for medications, blood draws and total
parenteral nutrition and ventilators.
Factors have contributed resistant microbial organisms:
·
Over
prescription of antibiotics
·
Use
of inappropriate antibiotics for the infecting organism
·
Incomplete
use of antibiotics prescriptions
·
Harboring
and spreading od resistant organisms
·
Increased
use of antibiotics in farming thus contaminating milk and meat.
CHAIN OF INFECTION
The life cycle of pathogens is frequently described as an
uninterrupted chain of events. To spread the disease they must grow, reproduce
and move from one source to another.
Interventions are directed at stopping the transmission from
the source to the directed at stopping the transmission from the source to the
patient controlling other links in the chain, thereby controlling infection.
Interruption of this cycle is a strategy to limit the spread of infection.
Transmission of infectious agents within a healthcare setting requires the
following elements.
Infectious agent:
Microbial
agent which may be bacteria, Virus, fungus, Prion or parasite.
Infection is depending on following factors;
·
Pathogenicity:
organisms ability to harm and to cause disease.
·
Virulence:
the vigor with which the organism grow and multiply.
·
Invasiveness:
organisms ability to enter the tissue.
·
Specificity:
organisms attraction to a specific host.
Source:
The source of organisms are called
reservoirs, are elements in the environment.
·
Inanimate objects includes medications, food, air
water or any other material on which organisms find nourishment and survive.
·
Human sources include other patients, healthcare
personnel family members, visitors and patient themselves.
·
Carriers: people who are in incubation or
having active disease and able to
harbor the pathogens but have no symptoms of disease
·
Animals:
insects, rats (leptospirosis), influence virus A (birds)
·
Organism
gaining access in to the host. Pathogens enter the susceptible hosts through
body orifices such as the mouth, nose, eyes, vagina, rectum or urethra.
·
Break
into the skin and mucus membrane from wounds or abrasions increase the
opportunities for organisms to enter hosts.
·
Central
venous catheters, for long term IV therapies or tubes for gastric feeding.
DEFENSES AGAINST INFECTION:
Normally each
Individual have their own defenses that protect the body from infection. These
defenses can be categorized as nonspecific and specific.
Nonspecific defenses protect the person against all
microorganisms, regardless of prior exposure. Specific (immune) defenses, by
contrast, are directed against identifiable bacteria, viruses, fungi, or other
infectious agents.
·
Natural: nonspecific natural defenses
Defense
|
Example
|
Individual
factors
|
·
Heredity
·
Good hygiene practices
·
Good nutritional status
·
Immunization history
|
Anatomic
Barriers
|
·
Intact skin
·
Intact mucous membranes
|
Mechanical
removal of microorganisms
|
·
GI motility
·
Ciliary action in the respiratory tract
·
Cleansing effect of urine
·
Expulsive effect of coughing and sneezing
·
Lavaging effects of tears and saliva
·
Shedding of uterine lining in menstruation
|
Chemical
factors
|
·
Acidity of gastric secretion, vaginal secretions and fatty acids of
skin.
·
Lysozyme enzymes in tears, nasal secretion, urine and saliva.
|
Local
tissue factors
|
·
Inflammation
|
WBC
function
|
·
Fever
·
Phagocytosis
|
Acquired: specific acquired defenses
Defense
|
Example
|
Another
important defense against infection is immunity. Antigens are foreign
particles Such as microbes, that enter a host.
In some
cases such as in autoimmune diseases the immune system senses or recognizes
the person’s own cells as antigens.
|
Cellular
immunity (T lymphocytes)
Humoral
immunity/ Antibody mediated immunity (B lymphocytes produce antibodies to
specific microorganisms).
|
COMMENTS