Exam 1 Intro to ID Lec 1 Flashcards
Before prescribing antibiotics we must first do what?
Determine if there is an infection present
What is the hallmark of infection?
Fever
What temperature indicates a fever?
> 38C (100.4F)
What is a normal body temperature?
36-37C (98-98.6F)
What are some of the non-infectious causes of fever?
Drug-induced
Malignancy
Blood transfusion
Auto-immune disorder
What drugs can cause drug-induced fever?
Beta-lactam antibiotics
Sulfonamides
Anticonvulsants
*fever coincides with administration and disappears when the agent is stopped
What can cause a fever to be detected falsely as negative?
*Antipyretics (acetaminophen, NSAIDs, aspirin)
Corticosteroids
Overwhelming infection (can cause hypothermia)
What are the systemic signs of infection?
BP: Hypotension (S <90 or MAP <70)
HR: Tachycardia (>90)
RR: Tachypnea (>20)
Fever
Increased/decreased WBC count (>12,000 or <4000)
What are the 4 criteria for systemic inflammatory response syndrome (SIRS) and how many criteria need to be met?
Tachycardia (>90)
Tachypnea (>20 rpm)
Fever
Increased/Decreased WBC (>12,000 or < 4000)
What is the systemic inflammatory response syndrome (SIRS) criteria used to determine?
If a patient is septic or not
What are the systemic symptoms of infection?
Chills
Rigors
Malaise
Mental status changes
What are the local symptoms of infection?
Symptoms that are referable to a specific body system
Pain and Inflammation
(swelling, erythema, tenderness, purulent or abnormal drainage)
*note that these may be absent in neutropenic patients
What are the non-infectious causes of elevated WBC counts?
Steroids
Leukemia
Stress
Rheumatoid Arthritis
Pregnancy
What are mature neutrophils?
The most common WBC
-Fight infections
AKA: PMNs, polys, segs
What are immature neutrophils?
Immature neutrophils released by the bone marrow into the blood
Increase during an infection= “left shift”
AKA: bands
What are eosinophils?
Involved in allergic reactions and immune responses to parasites
What are basophils?
Associated with hypersensitivity reactions
What are lymphocytes?
Humoral (B cell) immunity
+
Cell-mediated (T cell) immunity
What are monocytes?
Mature into macrophages
-serve as scavengers for foreign substances
What is leukocytosis?
Elevated neutrophils + bands
ASSOCIATED WITH BACTERIAL INFECTIONS
What is lymphocytosis?
Increase in B and T lymphocytes
Associated with: viral, fungal, or tuberculosis infections
What is the role of B-lymphocytes?
Proliferate into plasma cells and produce antibodies + memory B cells
What is the role of T-helper (CD4) cells?
Regulate the immune system
Help with antibody production
Secrete lymphokines to help protect against infection and tumors
*Depleted in HIV infection
What is the role of T-suppressor (CD8) cells?
Bind and kill tumor cells directly
Help regulate humoral and cell-mediated immunity
What is the absolute neutrophil count (ANC)?
Total number of circulating segs + bands
What ANC indicated neutropenia?
ANC < 500 cells/mm3
or
ANC expected to decrease to < 500 in the next 48 hours
*ANC < 100 is termed “profound neutropenia”
How do ANC and infection risk correlate?
Infection risk increases as ANC decreases
What are ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein)?
Biomarkers that are elevated in the presence of an inflammatory process
**these do not confirm an infection but are often elevated
What is procalcitonin and what do its levels tell us?
Precursor to calcitonin
*More specific for bacterial infections than ESR or CRP
Normal: <0.05
Increases 3-12 hrs after stimulation and declines over 24-72 hrs
*can get serial measurements while on therapy to determine if weaning is appropriate
How often can we take serial measurements of procalcitonin?
Every 1-2 days
For osteomyelitis, where would we take a culture collection?
bone biopsy
For meningitis, where would we take a culture collection?
CSF
For endocarditis, where would we take a culture collection?
blood cultures, heart valve tissue
Who should blood cultures be taken in and how?
-Acutely ill, febrile patients
Obtain from two different peripheral sites as two sets
*1 set= 1 aerobic and 1 anerobic bottle
*Take 1hr apart, with one from each arm
What is colonization?
A potentially pathogenic organism is present at the body site but is not invading host tissue or eliciting an immune response
What is infection?
A pathogenic organism is present at the body site and is damaging host tissue + eliciting host responses and symptoms consistent with infection
What is the only rapid diagnostic for bloodstream infections that can tell you susceptibility of the organism?
PhenoTest BC Kit
What is Minimum Inhibitory Concentration (MIC)?
The lowest antimicrobial concentration that prevents visible growth
Concentration of first vial with no growth in it
In susceptibility testing, what is the breakpoint?
MIC or zone diameter value used to categorize an organism as: susceptible, susceptible dose-dependent, intermediate, resistant, or non-susceptible
In susceptibility testing, what is “susceptible”? (S)
Isolates with an MIC at or below, or a zone diameter at or below the (S) breakpoint are considered inhibited by the usually achievable concentrations of antimicrobial agent when the normal dosing regimens are used
-this results in likely clinical efficacy
In susceptibility testing, what is “susceptible-dose dependent”? (S-DD)
Implies susceptibility is dependent on the dosing regimen used
*need to use higher doses than standard to adequately treat
In susceptibility testing, what is “Intermediate”? (I)
Isolates with MICs approach achievable blood or tissue concentrations and response rates may be lower than for susceptible isolates
In susceptibility testing, what is “Resistant”? (R)
Isolates not inhibited by usually achievable concentrations of agent with normal dosage schedules
-clinical efficacy has not been reliably demonstrated
In susceptibility testing, what is “non-susceptible”? (NS)
If MIC is above or zone diameter is below the susceptible breakpoint, the isolate is categorized as NS
What test is the gold standard for identifying a pathogen?
Broth dilution
What is the Kirby-Bauer method of pathogen identification?
AKA Disk Diffusion Assay
-put antibiotic impregnated disks on agar streaked with bacteria
-the drugs in the disks diffuse out into the agar
-there is visual bacterial growth only in areas where drug concentrations fall below those required for growth
-zone diameters are measured and compared with standard size ranges
What can you not determine from the Kirby-Bauer method?
Cannot derive MIC
*can only determine if susceptible, intermediate, or resistant
What is the Epsilometer test/ E test for pathogen susceptibility?
Gradient strip test
-Plastic strip is impregnated with known prefixed antibiotic concentration gradient placed on agar streaked with known bacteria
*MIC= concentration on strip where inhibition ellipse intersects the scale of the strip
*More precise than standard methods
*Expensive
*Used for newer agents with no other means of testing or for agents that are not in standard panels
What is the Vitek-2 System for determining MIC?
-Uses small reagent cards that test predetermined bug/drug combinations
-Growth curves are calculated for all wells compared to growth control curves
True or False: MICs are unique for each bug/drug combo
TRUE
-cannot compare different drugs based on MIC
What is Empiric Therapy?
Initial anti-infective therapy administered before identification and susceptibility results are known
*The selective anti-infective should cover most common pathogens
What is Directed (targeted) Therapy?
Therapy selected after the organism is identified and/or susceptibility is known
What is De-escalation?
Selecting an anti-infective with the narrowest spectrum of activity
-either stepwise or all at once
What is Spectrum of Activity?
What anti-microbials the drug covers
If a patient has pneumonia, what drug can be used as empiric therapy?
Cefepime
-covers a lot of bugs
If a patient has preliminary cultures that grow e.coli, what de-escalation drug can be used?
Ceftriaxone
-more specific for e.coli
If a patient is found to have pan-susceptible e.coli, what de-escalation targeted therapy can be used?
Amoxicillin
-the most targeted therapy
What is an Antibiogram?
Annual summary of institution-specific anti-infective susceptibility
**Want at least 80% susceptibility!!!
What can happen with a G6PG genetic deficiency?
Causes hemolytic anemia when given certain antibiotics
Which antibiotics have therapeutic drug monitoring available?
Vancomycin
Aminoglycosides
Which of the following is an example of an antimicrobial stewardship strategy?
◦ a) Switch to broad spectrum antimicrobials to better treat infections
◦ b) Require ID pharmacist approval before ordering broad spectrum antibiotic
◦ c) Continuing empiric antibiotics for 96 hours prior to reassessment
◦ d) Developing polices aimed at increasing antimicrobial resistance
b) Require ID pharmacist approval before ordering broad spectrum antibiotic
