Intro into ID Flashcards
what is a fever and what can cause false negative and positive results
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
Systemic signs of infection
Vital signs - SBP <90mmHg
HR >90bpm
RR >20rpm
Fever >100.4
Increased OR decreased WBC count (>12000 or <4000)
what is the criteria for systemic inflammatory response syndrome (SIRS) and how may criteria must a patient meet to have a positive SIRS
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)
what are the systemic symptoms
Chills
Rigors - shivering and sweating
Malaise - faintness
Mental status changes
Local signs and symptoms
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
what are the laboratory tests and radiologic findings that may identify infection
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)
What are mature neutrophils
Most common of the WBC and they attack infections
What are immature neutrophils
also known as bands these are just immature neutrophils and they increase during infection (this increase of bands is also called a left shift)
Eosinophils
these are invovled in immune reactions to parasites and also allergic reactions
Basophils
These are associated with hypersensitivity reactions
Lymphocytes
B cells and T cells
Monocytes
these mature into macrophages
they are the scavengers for foreign substances
WBC testing - Leukocytosis
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
WBC testing - lymphocytosis
increased number of lymphocytes (t cells and b cells) in the body
associated with viral, fungal, or tuberculosis infection
ANC
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
Acute phase reactants -ESR and CRP what are they and what do they tell us
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
Acute phase reactants - Procalcitonin
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
Radiographic test options
X-rays
Computed tomography
Magnetic resonance imaging (MRI)
Nuclear imaging (for bone scans)
Echocradiography
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?
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
What is the difference between Colonization and Infection
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
Identifying a pathogen
ALWAYS sample infected body materials before treatment if possible
Must avoid contamination
Identifying a pathogen: Microbiological studies
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)
Identifying a pathogen: susceptibility testing
MIC
MIC or Minimum inhibitory concentration is the lowest antimicrobial concentration that prevents visible growth
Identifying a pathogen
Breakpoint
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
Broth Dilution what is it used for
This testing is to identify the MIC and is the gold standard
MIC is the lowest concentration without visible growth
Identifying a pathogen: susceptibility testing (Disk diffusion assay)
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
Identifying a pathogen: Gradient strip tests
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)
Identifying a pathogen
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
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?
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
What is the difference of empiric therapy and Directed (Targeted therapy)
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
Antibiogram
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)
Factors to consider when choosing antibiotic
Patient history
Allergies
Age and weight
pregnancy
metabolic/genetic variations
organ dysfunction/renal or hepatic dysfunction
Monitoring therapeutic response
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
Goals of antimicrobial stewardship
Optimize clinical outcomes while minimizing unintended consequences
Second goal: reduce healthcare cost without adversely impacting quality of care
