week 4: diagnosis & pathogenesis of infectious diseases -

what are components of a diagnosis?

• combo of clinical cues, specimen collection, and testing

what is pathogenesis?

• disease development and influence of virulence factors

when does a lab result = diagnosis?

• when the result matches the clinical picture

• comes from a high quality specimen

what is a common diagnostic use for a blood specimen and what is its nursing focus?

• used for a bloodstream infection (bacteremia)

• sepsis evaluation

• focus:

  • aseptic collection

  • correct bottles for culture

  • timing

what is a common diagnostic use for a urine specimen and what is its nursing focus?

• UTI

• focus:

  • clean-catch midstream

  • ordered method

  • prompt transport

what is a common diagnostic use for a CSF specimen and what is its nursing focus?

• meningitis

• encephalitis

• focus:

  • urgent transport

  • follows strict protocol

what is a common diagnostic use for a sputum specimen and what is its nursing focus?

• lower respiratory infection (pneumonia)

• focus:

  • sputum (not salivia)

  • quality matters

what is a common diagnostic use for wound, tissue, and fluids specimen and what is its nursing focus?

• abscess or surgical site

• focus:

  • collect from infected site

  • avoid surface contamination

what 3 things determine specimen quality?

• proper selection

• proper collection

• proper transport

is blood normally sterile?

• yes!

what is bacteremia?

• bacteria in blood

• may or may not indicate disease

why are blood specimens easily contaminated?

• indigenous skin microbiota can get in the sample pretty easily

what do urine cultures include?

• colony count

• identification

• susceptibility testing

what does an order for a CSF specimen typically indicate?

• potential meningitis, encephalitis, or meningoencephalitis

• urgency is key!

what is sputum vs. salivia?

• sputum is from lower respiratory secretions

• saliva is oral and contains oral microbiota

where is the best location to collect wound, abscess, and body fluid specimens?

• in deep aspirate or deep tissue

• avoids indigenous microbiota of the skin

what is the process from specimen to result?

specimen processed —> pure culture obtained —> lab tests to identify —> antimicrobial susceptibility testing —> report findings to clinician

what is pathogenicity?

• ability of a microbe to cause disease

what is pathogenesis?

• the process of disease development

• describes process of exposure to tissue damage

what is an infection?

• pathogen becomes established in host

• may be asymptomatic and does not always lead to disease

what is an infectious disease?

• infection results in disease

• produces tissue damage and/or clinical manifestations

what is the chain of infection?

source of infection (pathogen) —> reservoir —> portal of exit —> mode of transmission —> portal of entry —> susceptible host

what is the incubation period?

• pathogen is present but symptoms are not apparent

what is the prodromal period?

• early period with vague symptoms

what is a localized infection and an example?

• limited to one area

• abscess, boil

what is a systemic/generalized infection and an example?

• affects body beyond local site

• disseminated infection

• systemic viral illness

what is a subacute infection and an example?

• between acute and chronic

• subacute bacterial endocarditis

what is an example of an acute infection?

influenze

what is an example of an chronic infection?

TB, syphilis

what are examples of localized cues of an infection?

• redness, warmth, swelling, pain, drainage

what are examples of systemic cues of an infection?

• fever, chills, tachy, hypotension, altered mental status

what is latency?

• pathogen is in host without causing symptoms

what is reactivation?

• pathogen reactivates and symptoms reoccur

what is virulence?

• ability to cause disease

what are virulence factors?

• things that help pathogens thrive (attach, evade host defenses, spread, and damage)

what are examples virulence factors?

• adhesins, capsules, exoenzymes, toxins

what is antigenic variation?

• a kind of invasion beyond capsules

• changes surface antigens to avoid detection

what is molecular mimicry?

• a kind of invasion beyond capsules

• pathogen resembles host which decreases detection and autoimmune response

what is intracellular survival?

• a kind of invasion beyond capsules

• pathogen hides in a host cell where defense and drugs are less effective

what do attachment virulence factors do?

• helps pathogen stay at correct site

  • adhesins, fimbriae

what do evade defense virulence factors do?

• reduce host clearence

  • capsule

  • antigenic variation, intracellular survival

what do spread/invade virulence factors do?

• supports tissue penetration and spread

  • hyaluronidase, collagenase, kinase

what do damage host virulence factors do?

• cause signs, symptoms, systemic inflammation

  • exotoxins, endotoxins, hemolysins, leukocidins

what is receptor specificity?

• specific pathogen ligands bind to specific tissue receptors

• explains why the same kind of pathogen affects the same tissues

what do exoenzymes do?

• support spread and survival of pathogen

what does hyaluronidase do and why does it matter?

• breaks down hyaluronic acid

• helps microbes move through CT

what does collagenase do and why does it matter?

• breaks down collagen

• supports tissue invasion and damage

what does kinase do and why does it matter?

• breaks down clots/fibrin

• may help spread through tissues

what does coagulase do and why does it matter?

• promotes clot formation

• may wall off bacteria from defenses

what does a neurotoxin affect?

nervous system

what does an enterotoxin affect?

• GI

• causes vomiting and diarrhea

what does a leukocidin affect?

• WBCs

• causes damage

what do pyrogenic toxins do?

• cause fever

what is the source, typical action, and clinical effect of an exotoxin?

• protein secreted by some bacteria

• often targets specific cells or body functions

• depends on toxin

what is the source, typical action, and clinical effect of an endotoxin?

• LPS in the outer membrane of a gram-neg bacteria

• Lipid A is the toxic part of an LPS

• triggers strong inflammatory response

• fever, inflammation, hypotension, and shock

what do pili/fimbriae do as a bacterial virulence structure?

• support attachment

what do capsules do as a bacterial virulence structure?

• evade phagocytosis

what do flagella do as a bacterial virulence structure?

• support movement

what do enzymes, toxins, and LPS do as a bacterial virulence structure?

• promote spread and damage

what is a primary infection?

• when a microorganism (like a virus or bacteria) enters an immunologically naive body—meaning the immune system has no prior antibodies or memory cells for that specific pathogen

what is a secondary infection?

• a new illness that develops during or after you are treated for a first, primary infection