The Infectious Process

The Infectious Process
Skin
Portals of Entry
Skin –the first line of defense
The skin must be broken to act as an entry portal
Including surgical skin incision, burns, cuts, scratches
Sebaceous glands - Secrete sebum (fatty acids)
Prevent bacterial and fungal infections
Low PH – inhibits microbes
The first line of defense – continued
Sweat glands – secrete perspiration
Has lysozyme – breaks down gram-positive bacterial cell walls
Also found in tears, saliva, and other tissue fluids
Common organisms entering the skin cause tetanus, gas gangrene, staphylococcal infection, and streptococcal infection
Note: Generally, these are opportunistic microorganisms which pose no threat of infection unless the skin is broken
Mucous Membranes
Line the respiratory tract
Easiest route of entry
They have specialized cells called goblet cells that secrete mucous
Including nasal secretions, tears, and saliva
Line nose, nasal passages, trachea, bronchi
Contain cilia that catch microbes and don’t allow them to penetrate furthered
Common organisms
Tuberculosis, pneumonia, common cold, measles (rubeola), German measles (rubella), scarlet fever, and smallpox

Gastrointestinal tract (Alimentary tract)
Include the mouth, esophagus, stomach, intestines
Enteric microorganisms enter through this route
Common organisms that enter through this route are
Typhoid fever, HEP A, HEP E, bacillary and amebic dysentery, and cholera.
Genitourinary tract
Kidney, ureters, bladder, urethra, vagina, uterus, penis
Infections are usually contracted sexually
Common organisms
All of the sexually transmitted diseases including HIV (AIDS)
Note: urinary infections are usually the result of the migration of microorganisms from the rectal area.

Placenta
There are certain microorganisms from the pregnant mother will penetrate the placenta and infect the fetus
These include: HIV (AIDS), smallpox, and German measles
Circulatory system
Organisms develop in one area then enter by invading the bloodstream
Example: an infection can start on the skin and the microorganism is picked up by the blood and spreads to other areas of the body
A tooth infection can enter the heart and cause endocarditis
Or they can be transmitted by contaminated blood transfusions, needle sticks, or cuts from sharp objects which are contaminated
Common organisms are HEP B and HIV
FYI: HIV can not transmitted through insect bites
Second Line of Defense
Phagocytes
They are called leukocytes (white blood cells)
Phagocytosis
The process where the leukocytes surround and ingesting a microbe or foreign particle and destroy it

Inflammation
A local response to infection
Includes pain, heat, redness and swelling (edema)
Vasodilation
Refers to the increase in diameter of blood vessels, which increases the blood flow to the area

Fever
A systemic reaction
Can be caused by a bacterial or viral infection
The infection produces prostaglandins from the hypothalamus, in the brain, which aid in the production of phagocytes aiding in phagocytosis
Interferons
What do interferons do?

Human Portals of Exit
A portal of exit is the pathway by which microorganisms leave the body
This depends largely on the part of the body affected by the disease.
Body secretions and excretions are potential portals of exit if they contain any component of blood
The main substances are blood, respiratory secretions, urine and feces

Blood
Include organisms causing HEP B and HIV
These are “blood-borne pathogens”
A major concern to health care professionals.
Fecal matter (feces)
Can include microorganisms causing hepatitis, polio and dysentery
Urine
Can include organisms causing typhoid fever
In the majority of cases urine is considered sterile when infection is not present
Respiratory secretions (sputum)
Can includes organisms causing tuberculosis, pneumonia, the common cold, or respiratory flu

Saliva
Includes organisms causing strep throat and may have the organism causing the common cold.
HIV will be transmitted in saliva only if it contains blood
Rabies: transmitted primarily by the saliva of an infected animal.
Tears
Can include organisms causing conjunctivitis
Semen and vaginal secretions
Can include organisms causing HIV (AIDS) and other sexually transmitted diseases

Other body fluids that may contain infectious blood cells include
Cerebrospinal fluid
Synovial fluid, found in the joints
Pericardial fluid
Peritoneal fluid
Amniotic fluid
Breast milk
Transmission of Pathogens
Direct contact
Patient to Worker/Worker to Patient
Can also include direct animal to person contact
Patient to Patient
Worker to Worker
Indirect Contact
The spread of contagious disease by some other medium than direct touching of infected person
Contaminated Food or water
Fomites
Inanimate objects
Example: bedpans, sheets, drinking cups, tables
Vectors
Examples: Flies, ticks, mosquitoes, mites
Vectors may carry pathogens inside their bodies and transfer this biologically through a bite as in Rocky Mountain spotted fever, or they may carry pathogens on their bodies and simply mechanically transfer these organisms as when flies land on food.
Dirt or dust
Air molecules

Factors Influencing Infection
Portal of entry
Most organisms will cause infection only when they enter a particular pathway
Example: swallowing malarial organisms would not cause the disease; they must enter through the bloodstream
Number of organisms
The normal body defenses can usually control a few organisms, but when large numbers are introduced, they usually cause infection

Virulence of the organism
Organisms are more virulent if they produce hemolysins, coagulase, enzymes, endotoxins, or exotoxins
The presence of a capsule also increases the virulence
Resistance of host
Resistance determines whether or not infection will take place and the severity of the disease.
Types of infection
Primary infection
The first or original infection
Secondary infection
One which follows or complicates the original disease
Latent infection
One which is inactive or hidden
Mixed infection
One caused by more than one organism
Examples: Appendicitis, wound infections
Acute and Chronic Infections
Acute
Runs a rapid and severe course terminating abruptly
Example: a cold or the flu
Chronic
Runs a slow course over a long period of time: may last from weeks to years
Example: Tuberculosis, syphilis, fungal infections

Stages of Infection
Incubation
Period between entrance of organisms to the body and onset of symptoms
Prodromal
Short period, usually a day or less, when symptoms are vague or cause only mild discomfort
Acute
Period of actual illness with symptoms, may have a degree of fever or not
The length of time depending on the disease, condition of patient, and the treatment

Convalescent
The beginning of the decline of the acute symptoms and fever (if present)
The length of time depends on the severity of the acute stage, the treatment of the pt, and their general health
Controlling Transmission
Portals of entry
Hand washing
Place sterile bandages over wounds
Wear masks over nose and mouth
Wearing protective eyewear
All of these can protect you or the pt
Use of insect repellent
Do not eat/drink contaminated food or beverage

Use only sterile supplies for invasive procedures (injections, surgery, etc.)
Cleansing (prepping) the proposed incision site
Providing sterile supplies and a sterile surgical environment
Properly clean hands after using the restroom
Get your required vaccination

Controlling transmission
Continued
Vectors, fomites, air
Sterilize or disinfect fomites
Used dust control measures
Don’t shake towels or drapes
Disinfect air
Properly handle food, water, and milk
Control insects
Vaccinate household pets
Words of Wisdom
There is no such thing as a great talent without great will-power.
Honore De Balzac
(1799 – 1850)