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Introduction to Antimicrobials > Intro to ID Lecture > Flashcards

Intro to ID Lecture Flashcards

1
Q

What are the 5 basic steps of ID assessment

A

■Establish presence of infection
■Fever ≠ Infection
■Determine site(s) of infection
■Determine likely pathogen(s)
■Select appropriate antimicrobial regimen

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2
Q

Review the case in the notes - what does this patient likely have?
RG, a 63-year-old 70 kg male, underwent emergency resection of his small intestine.
■
On day 20 of his hospital stay he becomes confused, his BP drops to 70/30 mmHg, with a HR of 130 bpm
■
His extremities are cold to the touch, he has a fever of 40°C, and his RR rate is 24 bpm.
■
He coughing up sputum and with decreased breath sounds on auscultation.
■
Chest x-ray indicates bilateral lower lobe infiltrates

A

Likely HAP

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3
Q

Is the patient in the case infected? What are 4 things we need to consider?

A

Careful history and physical

Signs and symptoms

Predisposing factors

Monitor for an adequate response

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4
Q

What are potential causes of fever?

A

Other causes:
■Malignancy (especially CNS)
■Autoimmune disease
■Physiologic stress (MI, surgery, etc…)
■Drugs (most common cause of unknown etiology)
Anticonvulsants
Sulfa containing compounds (diuretics, abx, hypoglycemics)
Antiarrhythmics (procainamide)
Antipsychotics (most common)
Beta-lactams

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5
Q

What might indicate a bacterial or fungal infection - an increase in neutrophils or increased lymphocytes?

A

Increased neutrophils may indicate bacterial or fungal infection
■ Left shift (increased bands – immature cells)

Increased Lymphocytes indicates viral infection

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6
Q

What does a left shift mean in terms of neutrophils?

A

Typically in the blood neutrophils are mature (segmented neutrophils, or PMNs). However during infection (typically bacterial or fungal), more neutrophils are created to fight it, which results in a left shift towards more immature neutrophils or “band neutrophils” which is the name of the immature neutraphils

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7
Q

What are other potential causes of increased WBC?

A

Inflammatory disorders
–Physiologic stress
–Malignancy
–Drugs
■e.g. corticosteroids, epinephrine, lithium

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8
Q

What acute phase reactants would be increased in infection?

A

ESR, CRP and procalcitonin

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9
Q

Which of the three acute phase reactants is more specific than CRP in terms of infection?

A

Procalcitonin (used to predict mortality) is more specific than CRPc in diagnosing bacterial infections and has a wider role in the management of complex infections. All are influenced by other inflammatory states.
ESR - is more useful for determining chronic inflammatory states.

https://www.youtube.com/watch?v=IIvtH5fl1UU

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10
Q

What are other S&S of infection?

A

Sometimes S&S are mild
- Sore throat
- Small sore on skin

Sometimes S&S may be more severe
- Painful cough, gross production of sputum
- Increased HR, decreased RR, and Decrease BP - caused by increased sympathetic drive and release of inflammatory mediators

ARe the signs local (Skin) or deep seated (meningitis, pneumonia)
- Swelling, erythema, tenderness, and purulent drainage
- These are only visible if the infection is superficial or in a bone/joint.
- DEEP seated infections must be determined from tissue or fluid samples.

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11
Q

How can one figure out the source of the infection?

A

The source of the infection we help determine the cause and can guide therapy (ie. cough - maybe lung infection)
https://www.youtube.com/watch?v=IIvtH5fl1UU

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12
Q

What are examples of hown the site can help determine therapy?

A

Most clinicians will look for a “focus”
–Cough…. probably lungs
–Leg is sore…. probably an ulcer just above
–Child is pulling on ear…. probably infection of inner ear canal
THEN look for the most common organism in that area.

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13
Q

Where do pathogens come from?

A

–patient to patient,
–vector to patient (animals, insects, etc…)
–environment to patient (e.g. hospital)
–derived from the patient’s own flora.

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14
Q

What are possible causes of elevated BG aside from diabetes?

A

Medications such as corticosteroids, thiazide diuretics, beta-blockers, and antipsychotics.
Certain conditions that affect the pancreas, which produces insulin.
Medical conditions that can cause insulin resistance, such as Cushing’s syndrome and acromegaly.
Pregnancy.
Stress.

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15
Q

When might blood cultures be drawn?

A

If patient appears to be experiences signs of sepsis (infection has entered the blood stream).

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16
Q

List common Gram Positive Cocci (3) and Gram Positive Bacilli?(2)

A
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17
Q

List common gram negative cocci (2), and common gram negative Bacilli

A
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18
Q

What are common anaerobes?

A
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19
Q

What are the common organisms in the following tissues:
Oral cavity and saliva
Respiratory mucosia
Lower GI
Bladder
Blood and CSF
Skin
Female lower genital tract
Joint fluid

A
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20
Q

What is the typical suspected organisms for pharyngitis?

A

Group A streptococcus

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21
Q

What are the typical organisms for bronchitis, and otitis media and sinusitis?

A

H.Influenzae, S. Pneumonia, M. Catarrhallis

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22
Q

What are the organisms commonly associated with Chronic sinusitis?

A

Anaeobes, S. aureus, and organisms associated with acute sinusisits.

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23
Q

What is the most common organism for epiglottis?

A

H. INfluenzae.

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24
Q

What organisms are found in CAP in:
Normal host
Aspiration
pediatrics
COPD
Alcoholic

A

Normal host - S. pneumonia, viral, mycoplasma Chlamydia (possibly gram -ve - H. Influenzae, M. Catarrhallis)

Aspiration - normal aerobic and anaerobic mouth flora
Pediatrics - S. pneumonia, H.Influenzae
COPD - S. pneumonia, H.s. influenza
Alcoholic - S. Pneumonia, Klebsiella

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25
Q

What are the most common organisms for HAP for:
1. Early onset (<4 days after hospital)
2. Late onset (>5 days after hosp)
3. Aspiration
4. Neutropenic
5. Aids

A
  1. Early onset (<4 days after hospital) - S. Pneumonia, H. Influenzae, S. aureus
  2. Late onset (>5 days after hosp) - Gram -ve rods (enteric) S. aureus, P. aeruginosa
  3. Aspiration - Mouth anaerobes, gram -ve aerobic rods, s. aureus
  4. Neutropenic -Funi, gram =ve aerobic rods, s. aureus
  5. Aids - fungi, penumocystis, legionella, norcardia, S. Pneumonia.
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26
Q

What organisms for UTIs are found for:
Community acquired
Hospital Acquired

A

CAUTI - E.Coli, staph aureus, S. Epidermidus, enterococci
HAUTI - Resistant gram -ve rods, enterococci

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27
Q

What are the common organisms for:
1. Cellulitis
2. Iv Catheter site
3. Surgical wound
4. Diabetic ulcer
5. Furuncle

A
  1. Cellulitis - Group A strep, S. Aureus
  2. IV Catheter site - S. Aureus, S. Epidermidis
  3. Surgical would - S. Aureus, gram -ve rods
  4. Diabetis ulcer - S. Aureus, gram -ve aerobic anaerobes and aerobic
  5. Furuncle - S. Aureus
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28
Q

What are common intra-abdominal organisms

A

Bacteriodes fragillis, E.Coli, Enterococci

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29
Q

What are common organism causes of Gastroenteritis?

A

Salmonella, shigella, helicobacter, campylobacter, C. Difficule, amoeba, giardia, viral, enterotoxigenic hemoffhagic, e.coli

30
Q

What are common organisms for Endocarditis
Subacute
Acute
a. IV drug user

A

Endo carditis/subacute - Streptococcus viridans
Acute
IV drug abuser - S. Aureus, enterococci, fungi, S. epidermidis

31
Q

What are common organisms for osteomylitis/septic arthritis

A

S. Aureus

31
Q
A
32
Q

What are common Meningitis organisms?
<2 months
2-12 years
Adults
HA
postneurosurgery

A

<2 months - E.Coli, Group B strep, listeria
2-12 years - Strep. pneumonia, N. meningitis, H. Influenzae
Adults - S. Pneumonia, N. Meningitidis
HA - S. Pneumonia, N. Meningitidis, Gram -ve rods
postneurosurgery- S. Aureus, gram -ve rods

33
Q

What are the drugs of choice for MSSA?

A
  • Cloxacillin, cefazolin, cephalexin
34
Q

HA-MRSA drugs of choice

A
  • Vancomycin, daptomycin, linezolid
    NOTE: HA organisms are Slower growing and trickier to treat.
35
Q

What are drugs of choice for CA-MRSA?

A
  • Clindamycin, trimethoprim-Sulfamethoxazole, doxycycline
36
Q

Best drugs for S. Pneumoniae (pen-susceptible)

A
  • Penicillin, or ampicillin
37
Q

Best drugs for S. pneumoniae (pen resistant)

A
  • 3rd gen cephalosporins (not ceftazidime), quinolones (not ciprofloxacin) vancomycin
38
Q

What are best drugs for enterococcus

A
  • Ampicillin or vancomycin
39
Q

What drugs are best used for easly to kill gram-negative cocci/bacilli? H.influenza, m. catarrhalis, Proteus spp. (some of them), E.coli (worry about ESBL-producers), Salmonella, Shigella

A
  • Amox, amox/clav, macrolides (2nd gen), cephalosporins for milder infections
  • May need bigger guns for more severe infections.
40
Q

What are the drugs of choice for the HARD to kill organisms (AKA Space organisms) - Serratia, pseudomonas, acinetobacter, citrbacter, enterobacter

A
  • Pip/Taz, 3rd/4th gen cephalosporins, carbapenems
  • Pseudomonas and acinetobacter are often very tricky

**regardless of this, always check susceptabilities.

41
Q

What other information regarding colonization, contamination and infection is good to have?

A

■
Colonization
–
The presence of organisms without an inflammatory response
■
Contamination
–
The presence of organisms usually acquired during specimen sampling without evidence of host inflammatory response
■
Infection
–
The presence of one or more organisms that initiate a host inflammatory response

42
Q

When to do blood cultures?

A

Blood cultures should be completed in acutely ill febrile patients (T = 38.5

should be done before antibiotics are initiated

43
Q

What about blood, sputum, urine, wound or sinus drainage?

A

Blood, sputum, urine, wound, or sinus drainage should also be evaluated
■
caution not all samples will yield useful results!!

44
Q

Why should infection sites be drained before antibiotics?

A

The AB may not be able to get to the site. If big enough to drain, then drain!

45
Q

Why is collecting samples from skin, oropharynx, nose, ears, eyes, throat and perinum problematic?

A

These areas are heavily colonized with a wide variety of bacteria, some of which can be pathogenic in certain settings
–
e.g. coagulase-negative staphylococci are found in cultures of all the aforementioned sites, yet are seldom regarded as pathogens unless recovered from blood, venous access catheters, or prosthetic devices

46
Q

What is the MIC?

A

The minimum inhibitory concentration (MIC) is defined as the lowest antimicrobial concentration that prevents visible growth of an organism after approximately 24 hours of incubation in a specified growth medium.
–
The MIC represents the amount of drug achievable in serum that can inhibit the growth of the bacteria
–
MIC data often are reported to the clinician qualitatively by deeming an organism “susceptible” reported as (“S”), “intermediate or indeterminate” reported as (“I”), or “resistant” reported as (“R”) to a given antimicrobial agent

47
Q

What factors should be considered if emperic therapy is needed before cultures come back?

A
  • Patient history (e.g. Allergies, renal function, interactions)
  • Severity and acuity of the disease
  • Host factors
  • Factors related to the drugs used and the necessity for using multiple agents
  • generally accepeted drugs of choice for the treatment of most pathogens
47
Q

How are pathogens classified in regards to the MIC?

A

–Pathogens classified as susceptible to an antibiotic are those that fall below a breakpoint MIC, which take in account clinically achievable serum concentrations in a patient (within appropriate safety profiles) and killing activity of the antimicrobial agent

48
Q

What important aspects of the patients history can help guide emperic therapy?

A

■Patient history
–Where was the infection acquired (community vs. hospital vs. nursing home)
–Has this person had previous infections or colonization
–Previous antibiotic use
–Site of infection and most likely organism

49
Q

What host factors are important to consider when choosing AB therapy?

A
  • AB allergy
  • Age - Elderly and neonates (elderly patients dont clear drugs well)
  • Pregnancy
  • Metabolic or genetic problems (G6PD deficiency)
  • Organ dysfunction - Kidney and liver
  • Concomitant drugs - drug interactions
  • Concomitant diseases - diabetes, PVD, HIV and cancer
50
Q

What are drug factors to consider when choosing ABs?

A

Drug factors
- Pharmacodynamic (what the drug does to the body/organism) and pharmacokinetic (what the body does to the drug)
- Time dependant killing
a. The time-dependent antibiotics exert optimal bactericidal effect when drug concentrations are maintained above the minimum inhibitory concentration (MIC).

B. Typically, concentrations are maintained at 2 to 4 times the MIC throughout the dosing interval.

C. For these agents, higher concentrations do not result in greater kill of organisms. Furthermore, they tend to have minimal to no post antibiotic effect (PAE)
d. Post-Antibiotic Effects (The post antibiotic effect (PAE) refers to the persistent suppression of bacterial growth that occurs after the drug has been removed in vitro or cleared by drug metabolism and excretion in vivo.)
- Most often used in Aminoglycosides

E.Bactericidal vs. Bacteriostatic antibiotics
■
Bacteriostatic antibiotics inhibit bacterial growth
■
Killing of the organism depends on host defense mechanisms

51
Q

What situations are most important for bactericidal antibiotics?

A

-Bactericidal antibiotics depend less on host factors, and are preferred in immunocompromised patients (neutropenic or immunosuppressed patients)
–
In severe, life-threatening infections (e.g. bacteremia in leukopenicpatients, patients with endocarditis or meningitis) bactericidal agents are necessary

52
Q

Which AB are bacteriocidal?

A

Betalactams, Vancomycin, Fluoroquin, aminoglycosides, metronidazole and daptomycin

53
Q

Which ABs are bacteriostatic?

A

Macrolides, tetracyclines and linezolid

54
Q

Describe examples of situations where tissue penetration matters?

A

If the drug does not get to the site of infection there is not much use for it.
■Abscess: concentrated with WBC products, various enzymes and pH can all inactivate drugs. Large collections need drainage!!
■Meningitis: cefazolin works against many bacteria causing meningitis, but it does not penetrate the CNS.
■Moxifloxacin: low renal clearance. Do not use for UTI.
■Nitrofurantoin: metabolized before reaching the urinary tract in poor renal function
■Pneumonia: daptomycin is inactivated by lung surfactant.
■Severely ill: oral absorption from the stomach is possibly affected even if that is not the site of infection.

55
Q

How does route of administration affect the antibiotic choice?

A

–
The proper route of administration for an antimicrobial depends on:
■ambulatory vs. hospital
■patient factors
■severity of infection
■site of infection

–
Pharmacy interventions:
■home IV programs
■IV-PO stepdown

56
Q

When is combination drug therapy used?

A

Combinations of antimicrobials generally are used to broaden the spectrum of coverage for empirical therapy, achieve synergistic activity against the infecting organism, and prevent the emergence of resistance. (although this is controversial)

57
Q

What is synergistic effect of AB?

A

Synergy is when two agents are used the produced effect of the two is greater than the combination of the two (e.g. Gram-positive endocarditis).
■
1+1=3

Ie. Using a betalactam with an aminoglycoside - Betalactam disrupts cell wall, so aminoglycoside can get in!

58
Q

When might combination therapy be used in a non-synergistic situation?

A
  1. When the risk of failure is catastrophic!
    e.g. respiratory infections in an ICU patient with a SPACE organism
59
Q

What can you do to drug therapy once you get more info? ie. susceptibilities are back, now more stable, started multiple drug therapies?

A

–
If you chose empirically, pick the best drug when susceptibilities are back
–
If they started on IV but are now stable, consider stepping down to oral therapy with good bioavailability
–
You started on a four-drug regimen to get through a critical phase and now can step down to 2 drugs in more of a maintenance stage

60
Q

How do you know the therapy you chose is working?

A

–Fever, WBC should start to resolve in 24-48 hours. If they do not, you must rethink therapy. Failure could be due to any of the reasons that have been previously mentioned.
–Physical complaints from the patient also should diminish (i.e., decreased pain, shortness of breath, cough, or sputum production)
- Symptoms like an x-ray in a pneumonia may takes weeks to improve, while the cough should with a pneumonia should start improving within a couple of days and continue to improve as therapy is prolonged.

61
Q

What criteria should be present to justify a switch to oral therapy?

A
  1. overall clinical improvement
  2. Lack of Fever for 25 hrs or more
  3. Decreased WBC count
  4. a functioning GI tract
    - Drugs that exhibit excellent oral biovailability when compared with intravenous formulations include ciprofloxacin, clindamycin, doxycycline, levofloxacin, metronidazole, moxifloxacin, linezolid and TMPSMX
62
Q

How long should you treat for?

A

SHORTEST TIME NEEDED

63
Q

How long do to treated Ucomplicated cystitis for with:
1. Nitrofurantoin
2. TMP-SMX
3. Fosfomycin

A
  1. 5 days
  2. 3 days
  3. 1 day
64
Q

How long do we treat for:
1. Complicated cystitis
2. Febrile UTI
3. Pylenephritis and urosepsis

A
  1. 7 days
  2. 7-14 days
  3. 7 days min
65
Q

How long to treat for:
1. Strep pharyngitis
2. Acute otitis media - 6mo to 2 y then >2 years
3. Acute sinusitis
4. CAP
5. HAP
6. Acute bacterial COPD exacerbations

A
  1. 10 days
  2. 6 mo to 2 y - 10 days >2 yr - 5 days
  3. 5 to 7 days
  4. 5-7 days
  5. <7 days
  6. 5 to 7 days
66
Q

How long to treat for:
1. Uncomplicated appendicitis
2. Traumatic bowel perforation
3. Gastroduodenal perforation
4. Intra-abdominal infection/abcess

A
  1. Pre-operative antibiotics ONLY - unless gangrenous appendicitis, or perforated appendcitis with out evidence of abcess should be treated by an additional 24-48 hr after appendectopmy.
  2. No more than 24 h post-operatively
  3. No more than 24 hours post-operatively
  4. <7 days after source control (no additional therapy if adequate drainage is in place)
67
Q

How long to treat acute osteoarticular infections in children?

A

3 to 4 weeks - should be transitioned to oral therapy once clinically able to use limb and CRP decreasing. Complicated infection, MRSA or other pathogens may require longer therapy.

68
Q

How long do we treat acute vertebral osteomyelitis?

A

6 weeks
Not associated with implantable device. Assumes S. Aureus but could be longer for salmonella or brucella infections

69
Q

How long to treat for acute native joint osteoarticular infections?

A

2 weeks for small joints after drainage
4 weeks for large joints after drainage

70
Q

How long do we treat for Bacteremia if:
1. Gram-negative enterobacterales (E.coli)
2. S. Aureus (uncomplicated)
3. S. Aureus (complicated)

A
  1. 7 days
  2. 14 d IV if uncomplicated
  3. 4-6 weeks IV - endocarditis, metastatic foci of infection, prolonged bacteremia >72 hours while on appropriate therapy. ID consult recommended.

Introduction to Antimicrobials (10 decks)

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