Wk 1 Infection Flashcards
Infection
colonization of a host by a microbial species
Localized
in a specific place
Systemic
spread to several regions/areas of the body
Common cause of infection
- virus - only DNA or RNA, surrounded by a protein shell, must have a host cell
- bacteria = much larger than a virus, single-celled organism
Rare causes of infection
- fungal = spore forming organisms
- protozoa = typically live in water/environment = malaria
- helminths - parasitic worms
- prions = rarest, proteinaceous infectious particles, only composed of protein, ex is mad-cow disease
Modes of transmission
microorganism must have a reservoir –> habitat where they usually live and grow (can be human, animal, insect, environment)
Direct transmission
kissing, sex, direct contact with contaminated soil or vegetation, droplet
Indirect transmission
airborne (droplet stay suspended in air), vehicle or vector born
Vehicle born
indirect transmit from food, water, or blood
Vector born
when something else carries the disease, like mosquitoes carry malaria
Portal of entry
how they get into the body
- oropharynx or nasopharynx (bronchial airways, lungs, stomach or GI tract)
- genitourinary tract (urinary tract)
Body’s biggest barrier
skin
Translocation
movement of bacteria across the intestinal lining
- occurs frequently in the peritoneal cavity
- bloodstream (like infection in your blood, then blood takes it to your bones)
Blood
blood transfusion contamination or needlestick
Maternal-fetal transmission
- some microorganisms can cross the placental barrier and get directly to the fetus
- some can occur during childbirth
Stages of Infection
- Incubation
- prodromal
- period of illness
- period of decline
- period of convalescence
- resolution
Incubation period
time from when that microorganism gets into the body and when symptoms first appear
Prodromal stage
onset of non-specific symptoms
Acute stage
period of illness
- full-blown
Convalescent stage
coming out of acute stage, symptoms getting better
Resolution phase
pathogen is completely eliminated from your body
- some infectious agents never get to this stage, like chickenpox laying dormant in your body
The infectious/inflammatory process
- injury
- increased permeability
- immigration of leukocytes
- phagocytosis
- exudate
- systemic symptoms
Injury
- initial insult to area occurs
- short period of vasoconstriction (very short so you stop bleeding and prevent movement of invading organisms)
- Prolonged period of vasodilation
Injury + Vasodilation
- allows blood to flow freely to the area
- brings immune cells to the area
- contributes to symptoms of inflammation such as warmth, redness, and swelling
Increased permeability
At site of injury
- fluid pulled out of vascular space because injury rarely occurs directly in vascular space (blood vessel)
- fluid moves out of vessel to the place of injury
Immigration of leukocytes
from the fluid out of vascular space
–> neutrophils attracted to area of injury
- neutrophils attach to the endothelium of injured cells and moved through into surrounding injured tissues
- other cells there = eosinophils, NK cells, monocytes
Phagocytosis
once leukocytes (wbc) make it to injury area, phagocytosis can occur
- neutrophils and monocytes are the specific WBCs involved
- they recognize, engulf, and destroy invading organisms
Exudate
the “stuff” that comes from the fluid leaking from blood vessels, along with cells and debris from phagocytosis
Exudate purpose
its purpose is to transport the leukocytes to injured areas, dilute toxins that might be present, and transport nutrients for the healing process
Types of exudate
- serous
- serosanguinous
- purulent
- hemorrhagic
Systemic symptoms
can occur if infectious process does not remain localized
Systemic symptoms + total body response
stimulates the hypothalamic fever set point
- fever set point increases
– helps body conserve heat
– stimulates defense mechanisms to help rid body of organisms
Higher body temperature
- in heat, some bacteria less virulent and divide slower
- improves our own immune system
– better neutrophil and macrophage function
– improves antibody release and T-cell activation
Colonization
where a pathogen inhabit a specific body site, does not cause s/s of infection
- can turn into active infection
Infection (vs. colonization)
clinical s/s of illness, inflammation
- caused by tissue damage r/t invasion of micro-organism
VS + infection
temperature, HR, RR all impacted when body fighting an infection
Labs + infection
cultures, urinalysis
Gram stain culture
- returned within hours
- takes a stain of bacteria and shows whether gram (+) or gram (-)
- also show bacteria shape and arrangement
- gram (-) is more dangerous, can disguise
Culture and sensitivity
- takes at least 24 hours for a basic results
- may take up to 72 hours for full identification and sensitivity pattern
What can you culture
- blood
- urine
- sputum
Culturing blood
- aerobic and anaerobic bottles
- ideally 2 sets obtained
- ideally at least one a peripheral stick
- high likelihood of skin contamination
Urinalysis normal pH
dipstick
- normal pH 5.0-9.0
Urinalysis + nitrites
normal = negative
- bacteria change from nitrates into nitrites
- positive = indicative of bacteria
Urinalysis + leukocyte esterase
normal = negative
- enzyme produced by WBCs
- indicates leukocytes in the urine and indicative of infection
Urinalysis + blood
normal = <5
if higher, can indicate infection
Healthcare setting infections
nosocomial –> infections that occur while in healthcare facility
- normally more virulent
- more likely to become drug resistant
Superinfections
new infection that occurs during treatment for a DIFFERENT infection
- typically caused by a resistant organism
Superinfection origination
the antimicrobials we use to treat initial/primary infection inhibit or kill normal helpful flora
- typically occurs within the GI tract
- skin or mucosal surfaces
Superinfection: C Diff
clostridium difficile
- normal intestinal flora killed by antimicrobial administration
- C diff able to grow w/o normal control factor
- diarrhea (orange + watery), abd cramping + tenderness, can occur days to months after abx treatment
- identify with PCR, NOT CULTURE
C diff isolation
Contact isolation (contact D at UK)
- gowns and gloves, wash hands with soap and water
C diff treatment
- treatment with PO/IV metronidazole (Flagyl) or PO vancomycin
-never give antidiarrheal meds until sure pt does not have C Diff
C Diff Complications
Pseudomembranous colitis
- life threatening
- causes colon to dilate, which may need decompression (air removal)
- may require surgery
Superinfection: Candidiasis
antimicrobial agents kill normal flora along with the pathogens they are supposed to
- can cause overgrowth of fungus
Candidiasis
typically occurs in mucous membranes
- oral/vaginal
- thrush when it is in the mouth
- can descend into the esophagus and cause problems if not treated
skin surfaces
- moist
- under the breasts or fat folds
Candidiasis treatment
- try and prevent this
- mycostatin = swish and spit anti-fungal medication, can also be vaginal suppositories
- nystatin = antifungal powder, think athlete’s foot
