Infection Process

Infection Process

Infection is the invasion or colonization of the body by pathogenic microorganisms.

Disease occur when an infection results in any change from a state of health.

Development of an infection occurs in a cycle that depends on the following elements.

·           An infectious agent or pathogen Ex. Salmonella

·           A continual source of infection is called a reservoir of infection (spread of infection)

·           A mode of transmission of disease

·           A portal of entry to a host

·           A susceptible host.

An infection will develop if this chain remains intact. Nurse use infection prevention and control practices to break the chain so that infection will not develop.

Chains of infection:

Infectious Agent: -

Microorganisms include bacteria, viruses, fungi and protozoa. They are common infectious agents or pathogens. The potential for microorganisms to cause disease is depends on the following factors.

·           Sufficient number of pathogens (Inoculum) which enter into the body.

·           Virulence or ability to produce disease.

·           Ability to enter and survive in the host (overcome the immune system of the host).

·           Susceptibility of host.

Reservoir: - A reservoir is where a pathogen can survive.

·           A continual source of infection is called a reservoir infection.

·           People who have a disease are carriers of pathogenic organisms (human reservoir).

·           Zoonoses can be transmitted to humans from animal reservoirs of infection.

·           Some pathogenic microorganisms grow in nonliving reservoirs Ex-Soil, Water.

Portal of exit: -

·           Pathogens have preferred portals of entry, they also have definite portal of exit.

·           3 common portal of exit.

Respiratory tract – coughing, sneezing

Gastro intestinal tract – Saliva, feaces

Genital tract – Vagina and penis

·           Arthropods and syringes provide a portal of exit for microbes in blood.

Modes of transmission: -

Mode of transmission is through direct or indirect contact, droplet infection, vehicle transmission, air borne, arthropod vector.

Portal of entry: -

Organism can enter the body through skin, mucous membrane, gastro intestinal tract, intestinal tract, blood, genital tract.

Compromised host: -

When a person acquires an infection depends on the susceptibility of an infectious agent.

·           Individual degree of resistance to a pathogen.

·           Patients with burn, surgical wounds, and suppressed immune system are the most susceptible.

·           According to the virulence of the microbes.

Course of Infection

Once a microorganism does overcome the defenses of the host, development of the disease follows a certain sequence of steps that tends to be similar whether the disease be acute or chronic.

·           Incubation period Proximal stage

·           Period of illness stage

·           Period of decline

·           Period of convalescence

Incubation Period: - The period of incubation is the time interval between the actual infection and the first appearance of signs and symptoms interval between entrance of pathogen into body and appearance of first symptoms.

e.g. Common cold -  1 to 2 days

Mumps - 18 days

Prodromal Stage: -The prodromal period is characterized by the appearance of the first mild signs and symptoms (low-grade, fever, fatigue). During this time microorganism grow and multiply and patient is more capable of spreading disease to others.

Illness Stage: - During this period of illness, the disease is at its height and all disease signs and symptoms are apparent.

e.g. Common cold - Sore throat, sinus

Mumps - Earache, high fever, parotid, salivary gland swelling

The severity of the patients’ illness depends on the extent of infection, the pathogenicity of the microorganism, susceptibility of individuals.

Decline Stage: -

During the period of decline, the signs and symptoms subside.

Convalescence Period: -

During the period of convalescence, the body returns to its predeceased state, the health is restored. Length of recovery depends on severity of infection and patients’ general health status. Recovery may take several days to month.

Defense Against Infection: -

1.        The immune system is one portion of  the  body’s  defense  against infection.

2.        Normal body flora that reside inside and outside of the body protect from several pathogens.

3.        Skin and mucous membrane both prevent pathogens from entering the body by creating a barrier, mucous traps microorganisms.

4.        Skin & Mucous Membrane

·           Acidity of Skin,

·           Saliva, tears (Ig A) Nostril hairs

·           Stomach Acidity

Provide first line of Defense against Infection it contains Ig A

·           The inflammatory response is a protective vascular and cellular reaction that neutralizes pathogens and repair body cells.

·           Inflammatory response – bring blood and therefore more phagocytes to the area.

·           IgA is predominantly present in secretion (tears, saliva, milk) is the first line of defense.

·           Lysozyme is present in phagocytes which digest the foreign particles, break the cell wall of gram positive bacteria

Types of Infection: -

Nosocomial Infection:-It is defined as any infections that are acquired during the course of stay in a hospital, nursing home, or other health care facility health care workers.

Iatrogenic   Infection:-Iatrogenic

infections are a type of nosocomial infection resulting from a diagnostic or therapeutic procedure.

i.e. UTI that develops after catheter insertion

·           Exogenous

·           Endogenous

Exogenous Infection: - Exogenous infection arises from microorganism external to the individual which do not exist as normal flora

Ex. Salmonella typhi – Typhoid fever

Endogenous Infection: - Endogenous infection occurs when part of the patient’s normal flora becomes altered (virulent) and also increase in number it will become opportunistic infection. Ex. Streptococci in mouth

E. coli in intestine as normal flora which may cause UTI. When it reach the urinary bladder.

Sites and causes for cross infection: -

Risk factors for infection

·           Broken skin or mucous membrane Obstructed urine outflow

·           Decreased mobility

·           Reduced hemoglobin level