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6 links in the chain of infection

1. pathogen
2. reservoir
3. portal of exit
4. means of transportation
5. portal of entry
6. susceptible person


-causative agent (viruses, bacteria, fungus)
- how many, how strong


- don't respond to antibiotics
ex. cold, HIV


- most common & most significant
- categorize by shape, gram stain & oxygen
- cocci (round/spherical)
- bacilli (rod)
- spirochetes (corkscrew)


patients, staff, food, equipment, solutions

portal of exit

body fluids, secretion containers, sneezing, coughing


- how it moves, multiplies
- can be direct = touch, intercourse, kissing
- indirect = instrument (toothbrush, needle)
hands, dirty equipment, air currents


breaks in skin, any body opening,

susceptible person

- degree of resistance to pathogen
Ex. sick, elderly, young, diabetics, after surgery, burn patients, chemo treatment

Reasons for increase in infections

↑ in antibiotic use, ↑ in mobility, ↑ # of people & people living longer (many illnesses), ↓ hygiene (lack of performance/access), ↓ immunizations, lack of resources (waiting to treat) lack of taking Rx appropriately, communal living (nursing homes & assisted living)

breaking chain of infections

pathogens = antibiotics
reservoir = isolation, screening, proper food, handling, housekeeping, sterilization, air filtering
exit = HANDWASHING/hygiene, red bagging, sharps container
transport = handwashing, PPE, dirty utility, sterile, air flow, proper food, handling
entry = skin intact, hygiene, catheter care, peri-care, mouth care, aseptic techniques
susceptible person = recognize those at risk & take precautions

Defense mechanisms: skin (3)

1. intact = 1st line of defense. provides barrier. cuts, abrasions, etc → alters defense
2. shredding of outer layer = removes organisms stuck to skin. failure to bath regularly → alters defense
3. sebum = contains FA that kills some bacteria. excessive bathing → alters defense

Defense mechanisms: Mouth (2)

1. intact, multilayered mucosa = provides mechanical barrier. lacerations, trauma & extract teeth → alters defense
2. saliva = washes away microbes, has microbial inhibitors (lysozyme). poor oral hygiene, dehydration →alters defense

Defense mechanisms: Respiratory tract

Defenses = cilia & macrophages (engulf & destroy MO that reach lung's alveoli)
Factors against defenses = smoking

Defense mechanisms: urinary tract

Defenses = flushing action of urine flow & multilayered epithelium
Factors against defenses = urinary catheters

Defense mechanisms: GI Tract

Defenses = acidity of gastric juices (chemically destroys MO) & rapid peristalsis (prevents retention)
Factors against defenses = antacids & delayed mobility

defense mechanisms: vagina

Defenses = normal flora (achieving low pH)
Factors against defenses = antibiotics & contraceptives

medical asepsis

- "clean as possible" & "clean techniques"
- used all the time
- reduces # of pathogens
- used in administration of: medications, enema, tube feedings, daily hygiene

surgical asepsis

- removal of all pathogens
- "sterile technique"
- nurses use infrequently
- used in: dressing changes, catheterizations, surgical procedures


- Methacillin resistant staphylococccus aureus
- very resistant,
- spread by contact, wounds on skin
- high mortality rate
Clearance guidelines = 3 negative cultures at least 24 hrs apart after antibiotics are complete


vancomycin resistant enterococcus
- limited treatment
- clearance = 3 negative cultures at least 1 week apart after antibiotics are complete

C Diff

clostridium difficile
- found in stool, diarrhea, distinctive odor
- clearance = when signs/symptoms stop


- usually sputum but also in blood & urine
- clearance = 1 negative culture from site of infection after antibiotics are complete


- multi-drug resistant gram negative bacteria (klebsiella, pseudomonas, acinetobacter)
- clearance = 1 negative culture from site of infection after antibiotics are complete

infection stages: 4

1. incubation period
2. prodromal stage
3. full illness stage
4. convalescent period

incubation period

- time of pathogen invading until symptoms appear
- time can vary
- ex. cold 1-2 days

prodromal stage

* most dangerous
- the time the person/host is most dangerous. you are infectious
- infectious time varies (hours, days)
- person may not realize how contagious they are b/c they don't feel terrible

full illness stage

- very sick
- time varies

convalescent period

- sign/symptoms resolve
- health returns

gram stain positive

apply stain bacteria is visualized

gram stain negative

apply stain bacteria is not visualized

fighting infections (3)

1. normal flora = keep bacteria at bay
2. inflammatory response (eliminate pathogen & help repair tissue)
3. immune system = produces antibodies to the antigen

immune system response

1. foreign antigen invades causing antigenic response
2. antibody surrounds foreign body
3. foreign body attacked
4. body will remember foreign antigen in case of future attacks


1. attack & destroy
2. Normal 5,000-10,000
3. Critical value = 15,000 (but it depends, look at trends & look at patient --> temp, vomit) Holistic care/big picture
4. Leukocytes, neutrophils, eosinophils, basophils are all baby WBC. Help Big WBC when they can't handle
5. Neutrophils come out first --> so need to consider these when looking at WBC ("Elevated WBC w/positive neutrophils" or "Elevated WBC with a left shift" = infection/severity of disease)

infection risk: Who?

young, old, people under stress, fatigue, malnutrition, contact w/people who are sick, multiple medications, devices (catheter), skin breaks, non-immunized

inadequate primary defenses

- broken skin or mucosa
- traumatized tissue
- decreased ciliary action
- obstructed urine flow
- altered peristalsis
- change in pH of secretions
- decreased mobility

inadequate secondary defenses

1. reduced Hbg level
2. nutrition
3. suppression of WBC's (drug or disease related)
4. suppressed inflammatory response (drug or disease related)
5. Low WBC count (leukopenia)

nosocomial "No so co mial"

- hospital acquired.
- important to recognize people who come in w/an infection


acquired from another person


acquired from inside you


infection from treatment or procedure

wound cultures

- remove superficial debris, then culture

urine cultures

- clean catch, if no catheter
- send to lab immediately so nothing starts to grow

throat culture

- take before antibiotics

stool culture

- just a little bit
- specimen container
- try not to send urine w/it

sputum culture

- collect before antibiotic
- deep secretions, not saliva
- usually 1st thing in the morning

blood culture

- 2 cultures CDC says 40-60 minutes apart (usually done 10 minutes apart)
- follow your agency rules (the minutes apart might be different

what is the purpose of infection control

to prevent transmission of infectious diseases to patients, you and families

most serious infections: nosocomial

- post operative infections (↑ LOS, ↑ tx costs, ↑ risk of death)
- to prevent use sterile techniques

contact precautions

direct = skin to skin
indirect = inanimate
- standard precautions + private room or cohorted, gloves worn when entering room

airborne precautions

- standard precautions + private room, monitored negative air, doors closed, limit patient movement
- TB, rubeola, varicella

droplet precautions

- standard precautions + private room, gloves, surgical mask w/in 3 feet, limit patient movement
-large droplet = no special air handling & ventilation
- meningitis, rubella, mumps, flu

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