Intro into ID

Question 1

what is a fever and what can cause false negative and positive results

Answer 1

Fever over 100.4 (always check patients medication profile to check if they are on anything that could present a false negative like acetaminophen, NSAIDs, or aspirin AND anything that could show a false positive like beta-lactam antibiotics, sulfonamides, and anticonvulsants

Question 2

Systemic signs of infection

Answer 2

Vital signs - SBP <90mmHg
HR >90bpm
RR >20rpm
Fever >100.4
Increased OR decreased WBC count (>12000 or <4000)

Question 3

what is the criteria for systemic inflammatory response syndrome (SIRS) and how may criteria must a patient meet to have a positive SIRS

Answer 3

4 criteria heart rate, respiratory rate, fever, and abnormal white blood cell count.
Patient must meet 2 of the following criteria

HR >90bpm
RR >20rpm
Fever >100.4
Increased OR decreased WBC count (>12000 or <4000)

Question 4

what are the systemic symptoms

Answer 4

Chills
Rigors - shivering and sweating
Malaise - faintness
Mental status changes

Question 5

Local signs and symptoms

Answer 5

Any type of pain, swelling, tenderness, purulent type symptoms that are at the site of the infection

these would be specific to where the patients infection is

Question 6

what are the laboratory tests and radiologic findings that may identify infection

Answer 6

WBC (normal is 4,500-11,000)
white blood cells include neutrophils,lymphocytes, monocytes, eosinophils, and basophils

NOTE - WBC can be elevated due to non infectious problems like steroids or leukemia (always check patient profile)

Question 7

What are mature neutrophils

Answer 7

Most common of the WBC and they attack infections

Question 8

What are immature neutrophils

Answer 8

also known as bands these are just immature neutrophils and they increase during infection (this increase of bands is also called a left shift)

Question 9

Eosinophils

Answer 9

these are invovled in immune reactions to parasites and also allergic reactions

Question 10

Basophils

Answer 10

These are associated with hypersensitivity reactions

Question 11

Lymphocytes

Answer 11

B cells and T cells

Question 12

Monocytes

Answer 12

these mature into macrophages
they are the scavengers for foreign substances

Question 13

WBC testing - Leukocytosis

Answer 13

Increased neutrophils with or without bands
represents bacterial infection

If left shift/bands present it tells us increased bone marrow response to infection

Leukopenia (Low WBC) can represent overwhelming infection

Question 14

WBC testing - lymphocytosis

Answer 14

increased number of lymphocytes (t cells and b cells) in the body

associated with viral, fungal, or tuberculosis infection

Question 15

ANC

Answer 15

Absolute neutrophil count which is important in neutropenia

neutropenia is ANC <500 or <100

The risk of infection is drastically increased as the ANC count lowers

Question 16

Acute phase reactants -ESR and CRP what are they and what do they tell us

Answer 16

ESR is erythocyte sedimentation rate and CRP is C-reactive protein

these are elevated in presence of inflammatory process but it does not confirm infection

Normal ESR 0-15 and Normal CRP 0-0.5

Question 17

Acute phase reactants - Procalcitonin

Answer 17

This is a test that should be used ever 1-2 days to assess how a patient is responding to therapy and when to D/C therapy

PCT - more specific for bacterial infections than ESR or CRP

Normal level is <0.05
low risk infection <0.25
antibiotics should be continues if a patient has a PCT of >0.5mcg/L

Question 18

Radiographic test options

Answer 18

X-rays
Computed tomography
Magnetic resonance imaging (MRI)
Nuclear imaging (for bone scans)
Echocradiography

Question 19

HPI: JH is a 65 YOM who is admitted with shortness of breath x 4 days
VS: Temp: 101F, HR: 98 BPM, RR: 21RPM, O2 saturation: 80% on room air, BP: 120/80
PE: unilateral rales, crackles,
ROS: Difficulty breathing, chills
Labs: WBC: 14,000; PCT: 0.8 mcg/mL; CRP: 12
Imaging: Xray: Consolidation present

a) What signs/symptoms indicate the presence of an infection

b) Which of the SIRS criteria, if any, does the patient have?

Answer 19

A. Fever, elevated WBC, HR>90, RR>20 crackles, chills, PCT>0.8 CRP elevated

B. HR>90, RR >20, BP SBP<90, WBC elevated

Question 20

What is the difference between Colonization and Infection

Answer 20

Colonization is organism that is present in the patient but not causing any signs or symptoms

Infection is when the organism is present at the body site and is damaging host tissue and the patient has signs and symptoms of infection

Question 21

Identifying a pathogen

Answer 21

ALWAYS sample infected body materials before treatment if possible

Must avoid contamination

Question 22

Identifying a pathogen: Microbiological studies

Answer 22

Type of culture collected depends on site of infection Osteomyelitis = bone biopsy
meningitis = CS fluid
endocarditis = blood cultures, heart valve tissues

Blood cultures need to get 1 aerobic and 1 anerobic bottle (these two are called a set) from both right and left arm (2 sets or 4 bottles total)

Question 23

Identifying a pathogen: susceptibility testing
MIC

Answer 23

MIC or Minimum inhibitory concentration is the lowest antimicrobial concentration that prevents visible growth

Question 24

Identifying a pathogen
Breakpoint

Answer 24

MIC or zone diameter value used to categorize an organism as susceptible, susceptible-dose dependent, intermediate, resistant, or non- susceptible, intermediate, resistant, or non-susceptible

you want to pick options that are susceptible and never resistant

Question 25

Broth Dilution what is it used for

Answer 25

This testing is to identify the MIC and is the gold standard
MIC is the lowest concentration without visible growth

Question 26

Identifying a pathogen: susceptibility testing (Disk diffusion assay)

Answer 26

This test is used to identify the breakpoint of different antibiotics on the pathogen
we cannot derive a MIC from the zone of inhibition - EXAM Q

Question 27

Identifying a pathogen: Gradient strip tests

Answer 27

Also called E-Test
you place a plastic strip that has antibiotic concentration on the agar with known bacteria and we can get MIC (MIC is represented by the line above the last line of growth) (picture on slide 35 if confused)

Question 28

Identifying a pathogen

Answer 28

VItek-2 system
Microscan walkaway
BD phoenix microbiology system

all of these can be used to test for the MIC concentration and are fast and efficient

Question 29

A 62 YOM is diagnosed with ventilator-associated pneumonia (VAP).
Piperacillin/tazobactam is started initially and cultures result for E.coli. Below is the
susceptibility report:

Cefepime ≥64 mcg/mL (Resistant)
Ceftazidime ≤1mcg/mL (Susceptible)
Ciprofloxacin ≤0.5 mcg/mL (Intermediate)
Levofloxacin 1 mcg/mL(Intermediate)
Meropenem ≤ 0.25 mcg/mL (Susceptible)
Piperacillin/tazobactam ≥ 64 mcg/mL(Resistant)

a) What adjustments, if any, do you want to make to your antimicrobial plan?
b) Would meropenem be the best option since it has the lowest MIC?

Answer 29

A. We would want to D/C the Piperacillin/tazobactam as the culture is resistant to the antibiotic and we should start Ceftazidime or Meropenem as these are the two susceptible antibiotics

B. NO! We can never compare MIC values between antibiotics as they are unique values for each - EXAM Q

Question 30

What is the difference of empiric therapy and Directed (Targeted therapy)

Answer 30

Empiric therapy is the first antibiotic regimen picked before identification and susceptibility results are known. It should be broad spectrum and cover most common pathogens

Targeted is therapy selected after identification and/or susceptibility is known

De-escalation: selecting an antibiotic that has a narrow spectrum of activity can be stepwise or all at once

Question 31

Antibiogram

Answer 31

annual summary of anti-infective susceptibility
The isolates tested are specific to what is most common at the hospital one is at

emperic options only and can be tested from urine and non-urine: want to pick an antibiotic that has 80% susceptibility or more (Picture of testing on 49)

Question 32

Factors to consider when choosing antibiotic

Answer 32

Patient history
Allergies
Age and weight
pregnancy
metabolic/genetic variations
organ dysfunction/renal or hepatic dysfunction

Question 33

Monitoring therapeutic response

Answer 33

Culture and sensitivity test
WBC, temperature, physical complaints
TDM
if patient is on IV we want to get them on PO as soon as possible when safest
Antimicrobial failure

Question 34

Goals of antimicrobial stewardship

Answer 34

Optimize clinical outcomes while minimizing unintended consequences

Second goal: reduce healthcare cost without adversely impacting quality of care