Exam 1 Intro to ID Lec 1 Flashcards by TheOneandOnly Ash

Before prescribing antibiotics we must first do what?

Determine if there is an infection present

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What is the hallmark of infection?

Fever

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What temperature indicates a fever?

> 38C (100.4F)

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What is a normal body temperature?

36-37C (98-98.6F)

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What are some of the non-infectious causes of fever?

Drug-induced
Malignancy
Blood transfusion
Auto-immune disorder

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What drugs can cause drug-induced fever?

Beta-lactam antibiotics
Sulfonamides
Anticonvulsants

*fever coincides with administration and disappears when the agent is stopped

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What can cause a fever to be detected falsely as negative?

*Antipyretics (acetaminophen, NSAIDs, aspirin)

Corticosteroids

Overwhelming infection (can cause hypothermia)

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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)

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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)

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What is the systemic inflammatory response syndrome (SIRS) criteria used to determine?

If a patient is septic or not

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What are the systemic symptoms of infection?

Chills
Rigors
Malaise
Mental status changes

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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

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What are the non-infectious causes of elevated WBC counts?

Steroids
Leukemia
Stress
Rheumatoid Arthritis
Pregnancy

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What are mature neutrophils?

The most common WBC

-Fight infections

AKA: PMNs, polys, segs

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What are immature neutrophils?

Immature neutrophils released by the bone marrow into the blood

Increase during an infection= “left shift”

AKA: bands

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What are eosinophils?

Involved in allergic reactions and immune responses to parasites

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What are basophils?

Associated with hypersensitivity reactions

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What are lymphocytes?

Humoral (B cell) immunity
+
Cell-mediated (T cell) immunity

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What are monocytes?

Mature into macrophages

-serve as scavengers for foreign substances

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What is leukocytosis?

Elevated neutrophils + bands

ASSOCIATED WITH BACTERIAL INFECTIONS

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What is lymphocytosis?

Increase in B and T lymphocytes

Associated with: viral, fungal, or tuberculosis infections

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What is the role of B-lymphocytes?

Proliferate into plasma cells and produce antibodies + memory B cells

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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

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What is the role of T-suppressor (CD8) cells?

Bind and kill tumor cells directly

Help regulate humoral and cell-mediated immunity

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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