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Six links in the chain of infections
- Infectious agent
- Portal of exit
- Mode of transmission
- Portal of entry
- Susceptible host
- beneficial microorganisms or even essential for human health and well-being.
- Normal flora in the intestine aid in digestion and synthesized vitamin K, and release vitamin B12, thiamine, and riboflavin when they die.
- Transient flora: are normal microbes that a peson picks up by coming in contact with objects or other person(ex. soiled dressing) And you can remove with hand washing
- Resident flora: live deep in skin lyaers, where they live and multiply harmlessly. They are permanent inhibitants of the skin and cannot be removed with handwashing. Not uusually harful unless they enter the deep dissues or unless the patient is especially vulnerable to disease.
- microorganisms capable of causing disease
- Ex. large groups are bacteria, viruses, fungi
- Less common are protozoa, helminths and prions(infectious protein particles)
successful invasion of the body by a pathogen
power of the organism to cause a disease
is a source of infection:a place where pathogens survive and multiply. Living reserviours and nonliving.
indivisuals that have no simptoms of disease, yetthey serve as reserviours and can pass the disease to others
Portal of exit
for infection to spread, a pathogen must exit the reservior. In the case of human or animal reservoirs, the most frequent portal of exit is through body fluids, including blood, mucus, saliva, breast milk,urine, feces, vomitus, semen or other sercretions.
Mode of transmision
- Direct contact: between two people usually involves touching, kissing, or sexual intercoursel Animals commonly transmit infection via scratching and biting as well.
- Indirect contact: involves contact with a fomite, a contaminated object that transfers a pathogen.
- Droplet transmission: occurs when the pathogen travels in water droplets expelled as an infected person exhales, coughs, sneezes or talks
- Airborne transmission: folat on air currents. Travel through heating and air conditioning systems.
- Vector: is an organism that carries a pathogen to a susceptible host, typically by biting or stinging, creating another portal of entery into the body. Ex. mosquito, ticks, fleas, mites are vectors.
Portal of Entery
Pathogens enter trough normal body openings, such as conjuctiva of the eye, the nares, mouth, urethra, vagina, and anus. Anormal openings such as cuts, scrapes, surgical invicions.
or compramised host is a person who is atrisk for infection becuase of inadequate defenses against the invading pathogen.
Predictable stages of infection pg. 413
- Prodromal stage
Primary defences pg. 416
- respiratory tree
- gastointestinal tract
- genitourinary tract
- are triggered when pathogens dodge primary defenses and gain entry into the body and begin to release wastes and secretions and to cause the breakdown of cels and tissues.The presence of such chemical activates a set of secondary defenses.
- The complement cascade
- Humoral immunity: response acts directly against antigens - have molecules on their surface that trigger a specific immune response recognized by Lyimphocytes(T and B cells) as soon as they recognize antigens they create antibodies (immunoglobulines) that bind to atigens and destroy them.
- Cell-medicated immunity: destroy body cells that have become infected. T cells
- asepsis: absence of contamination by disease-causing microorganisms.
- medical asepsis: clean technique refers to procedures that decrease the potential for the spread of infections. It inculde hand hygiene, environmental cheanliness, standard precautions, and protective isolation.
first tier of protection, apply to care of all patients
second tier(yarus) of protection, outline precations to be taken based on mode of transmission of the infection (contact, droplet, or air)