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PHRM 865 - exam 1 > Intro to ID part 2 > Flashcards

Intro to ID part 2 Flashcards

1
Q

Gram positive - gram stain testing

A

gram positive bacteria have a large peptidoglycan cell wall and appear purple in a gram stain test result

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2
Q

Gram negative - gram stain testing

A

Gram negative have a line cell wall and appear as a pink or red color on a gram stain test result

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3
Q

What are the two groups of gram positive

A

Cocci and Bacilli

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4
Q

Gram Positive Cocci Anaerobic

A

Peptococcus
peptostreptococcus

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5
Q

Gram Positive Cocci aerobic Catalase + and Coagulase +

A

Straphylococcus aureus

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6
Q

Gram Positive Cocci aerobic Catalase + and Coagulase -

A

All other straphylococcus species

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7
Q

Gram Positive Cocci aerobic catalase - alpha-hemolysis (partial)

A

Streptococcus pneumoniae
Viridans streptococci

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8
Q

Gram Positive Cocci aerobic catalase - beta-hemolysis (full)

A

Streptococcus Pyogenes
Streptococcus agalactiae

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9
Q

Gram Positive Cocci aerobic catalase - Gamma-hemolysis (none)

A

Enterococcus Faecium
Enterococcus faecalis

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10
Q

Gram Positive Bacilli Anaerobic Spore forming

A

Clostridium Species
Clostridioides difficile

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11
Q

Gram Positive Bacilli Anaerobic non-spore forming

A

cutibacterium
actinomyces

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12
Q

Gram Positive Bacilli Aerobic spore forming

A

Bacillus species

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13
Q

Gram positive Bacilli Aerobic non-spore forming

A

Corynebacterium
Lactobacillus species
Listeria
Monocytogenes

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14
Q

Biochemistry testing

A

Catalase test will tell us if it is staphylococci (catalase positive) or Streptococci (catalase - )

Coagulase test will tell us if its staphylococcus aureus (coagulase +) or staphylococcus coagulase negative

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15
Q

Agar appearance for hemolytic testing

A

This is done on cocci catalase negative aerobic species

alpha- hemolytic is a partial result and tells us its oral flora

Beta- hemolytic is a full result and tells us its skin pharynx and genitourinary

Gamma-hemolytic has no result and tells us it is gastrointestinal

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16
Q

You receive a call from the microbiology lab informing you that patient JR has Gram-
positive cocci growing in the blood. They don’t have a full identification but tell you the
organism is catalase positive, coagulase positive. Which of the following organisms could
be growing in JR’s blood?
a) Staphylococcus aureus
b) Staphylococcus epidermidis
c) Streptococcus pyogenes
d) Enterococcus faecalis

A

A
Since the result is catalase positive it means it is staphylococcus aureus and with a positive coagulase testing it further confirms straphylococcus aureus

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17
Q

Gram negative aerobic Cocci

A

Neisseria species
Moraxella catarrhalis

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18
Q

Gram negative aerobic Coccobacilli

A

Haemophilus species

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19
Q

Gram negative anaerobic cocci

A

Veillonella species

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20
Q

Gram negative anaerobic bacilli

A

bacteroides species
fusobacterium speices
Prevotella species

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21
Q

gram negative aerobic bacilli Enterobacterales Lactose fermenters - IMPORTANT

A

Means they are oxidase negative
CEEK
Citrobacter
Enterobacter
E. Coli
Klebsiella

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22
Q

gram negative aerobic bacilli Enterobacterales non-lactose fermenters - IMPROTANT

A

Means they are oxidase positive

Morganella morganii
Proteus
Providencia
salmonella
Serratia marcescens
Shigella

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23
Q

gram negative aerobic bacilli lactose fermenters

A

means they are oxidase positive
Aeromonas hydrophila
pasteurella multocida
vibrio cholerae

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24
Q

gram negative aerobic bacilli non-lactose fermenters

A

oxidase negative

pseudomonas
acinetobacter
alcaligenes
burkholderia cepacia
stenotrophomonas maltophilia

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25
Q

gram negative aerobic bacilli Fastidious

A

Campylobacter
Helicobacter
Bartonella
HACEK* organisms

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26
Q

Atypical

A

These will not stain on a gram test

Chlamydia trachomatis
Legionella pneumophila
Mycoplasma pneumonia

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27
Q

Spirochetes

A

treponema pallidum
Borrelia burgdorferi

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28
Q

What does lactose fermentation tell us

A

helps us identify and distinguish between enteric vs non-enteric lactose fermenters

29
Q

You receive a call from the microbiology lab informing you that patient ZE has Gram
negative rods growing in the blood. They don’t have a full identification but tell you the
organism is a non-enteric non-lactose fermenter. Which of the following organisms could
be growing in JR’s blood?

a) Pseudomonas aeruginosa
b) Citrobacter freundii
c) Morganella morganii
d) Aeromonas hydrophila

A

A

B is a Enteric coded lactose fermenter
C is a enteric coded non-lactose fermenter
D is non-enteric coded lactose fermenter

30
Q

what are Penicillin Binding proteins

A

Also known as PBPs
These play a role in cell wall synthesis, cell shape, and structural integrity

Binding to PBPs 1A, 1B, 2, and 3 result in bacterial effect

Transpeptidase is the most important PBP as it catalyzes the final cross linking in the peptidoglycan structure

31
Q

Intrinsic Resistance

A

when the species is always been resistant to the given antibiotic due to absence of a target site or the bacterial cell impermeability

32
Q

Acquired resistance

A

when species is initally susceptible but develop resistance due to some mechanism due to mutation in bacterial DNA or Acquisition of new DNA

33
Q

Aquired resistance examples

A

Plasmid - transferable between organisms

Transposons - move from plasmid to chromosome or vice versa

Conjugation - most common

34
Q

Which of the following describes the difference between Gram-positive and Gram-negative bacteria?

a) Gram-positive have a thin cell wall; Gram-negative have a thick cell wall
b) Gram-positive have a thick cell wall; Gram-negative have a thin cell wall
c) Gram-positive have porin channels; Gram-negative lack porin channels
d) Gram-positive have PBP; Gram-negative lack PBPs
Mechanisms

A

B

35
Q

what are the 4 mechanisms of antibiotic resistance

A
  1. Altered cell wall protein/ decreased porin production
  2. Increased efflux pumps
  3. increased drug inactivating enzymes
  4. modified drug target
36
Q

mechanism of resistance
drug inactivating enzymes
Beta - lactamase

A

this enzyme will split an amide bond on a beta lactam ring resulting in hydrolyzing the drug and making it inactive

Two classes: Amber and Bush

there are two types Serine beta lactamases and Metallo beta lactamases

37
Q

Ambler classification of beta lactamase
Class A

A

Narrow spectrum B lactamases - produced primarily by enterobacterales

Extended spectrum B lactamases (ESBL) - Enzyme example CTX-M-15

Serine carbapenemases - Enzyme example KPC-1, KPC-2, KPC-3

38
Q

Ambler classification of beta lactamase
Class B

A

Metallo B lactamases - enzyme example NDM-1

39
Q

Ambler classification of beta lactamase
Class C

A

Cephalosporinases - enzyme example AMP- C

40
Q

Ambler classification of beta lactamase
Class D

A

OXA-type - enzyme example OXA-48

41
Q

Ambler class A : ESBLs

A

Plasmid mediated
Treatment choice: Meropenem, Imipenem, Doripenem, Ertapenem

can also use piperacillin/tazobactam for Urinary source ONLY

42
Q

Ambler class A: Carbapenemase

A

Treatment options:
B lactam: ceftazidime/avibactam, Meropenem/Vaborbactam, impienem/cilastatin/relebactam
non-B-lactam: plazomicin, eravacycline, omadacycline

43
Q

Ambler class B: Metallo B lactamases

A

confer resistance to all B-lactams except monobactams

Treatment is limited but option is Cefiderocol

44
Q

Ambler Class D: OXA type

A

Primairly found in Ainetobacter baumannii and Pseudomonas aeruginosa

Treatment options: Cefiderocol or Sulbactam/durlobactam

45
Q

JM is a 45 YOM admitted with fever, chills, urinary frequency and urgency. Blood cultures are collected and 12
hour after admission rapid diagnostic testing identifies E.coli, CTX-M (+) in 4/4 bottles.

Q1) What type of antibiotic resistance is present?
a) Non-CP CRE
b) ESBL
c) NDM
d) KPC

A

B - ESBL

46
Q

JM is a 45 YOM admitted with fever, chills, urinary frequency and urgency. Blood cultures are collected and 12
hour after admission rapid diagnostic testing identifies E.coli, CTX-M (+) in 4/4 bottles.

Q2) What is the recommended treatment option?
a) Meropenem
b) Meropenem/vaborbactam
c) Aztreonam + Ceftazidime/avibactam
d) Piperacillin/tazobactam

A

ESBL resistance present and patient should be started on A

47
Q

Ambler Class C: AmpC

A

has 3 mechanisms but main focus is inducible via chromosomal encoded AmpC genes

Found in Hafina alvei, Enterobacter cloacae, Citrobacter freundii, Klebsiella aerogenes, Yersinia Enterocilitica (HECK-YES)

48
Q

AmpC induction mechanism

A

Genetic mutation causes gene derepressed and eventually keeps this derepression stable meaning there is high levels of beta-lactamase production continuously and it is inactivating the drug

49
Q

AmpC inducers
High susceptibility to AmpC hydrolysis

A

Strong inducers - penicillin and ampicillin

Weak inducers - ceftriaxone

50
Q

AmpC inducers low susceptibility to AmpC hydrolysis

A

Strong inducers - carbapenems (imipenem, Meropenem, ertapenem)
Weak inducers - Cefepime

51
Q

Treatment of stably derepressed mutants

A

First line cefepime

52
Q

JH is a 65 YOM admitted with pyelonephritis (infection in the kidney) and started on IV ceftriaxone. However, he soon develops a fever and becomes hypotensive. Blood cultures are taken and result for E. cloacae.

Q1)What could explain his sudden decompensation?
a) E. cloacae harbors an ESBL gene and this was induced with ceftriaxone treatment
b) E. cloacae harbors a KPC gene and this was induced with ceftriaxone treatment
c) E. cloacae harbors an AmpC gene and this was induced with ceftriaxone treatment
d) E. cloacae harbors a NDM gene and this was induced with ceftriaxone treatment

2) What antibiotic change do you recommend?
a) Switch to Piperacillin/tazobactam
b) Switch to Cefepime
c) Switch to Ceftazidime
d) Switch to Aztreonam

A

Q1 C
Q2 B

53
Q

Enzymatic inactivation: amino-glycoside- Modifying Enzyme

A

3 mechanisms
acetylation, nucleotidylation, Phosphorylation

Modify aminoglycoside structure by transferring the indicated chemical group to specific side chain

54
Q

Altered target site: Cell wall precursor
Mechanism of Vancomycin resistance in enterococci Species

What is resistance mediated by and what is the treatment

A

normal action of vancomycin binds to D-alanine-D-alanine terminus of peptidoglycan precursors

Resistance alters this D-alanine- D-alanine to D-ala-D-lac or D-ser
Mediated by VanA or VanB (EXAM-Q)

Treatment of resistance is Daptomycin or linezolid

55
Q

Altered Target site: Penicillin Binding Proteins

A

Leads to B lactam resistance
Due to decreased affinity of PBPs for antibiotic or change in amount of POP produced by bacteria

Methicillin-resistant staphylococcus aureus (MRSA) resistant due to expression of mecA gene
treatment is Ceftaroline, ceftobiprole

56
Q

Other altered target sites
Ribosomal target

A

Responsible for macrolide resistance in S. Pneumoniae
ermB gene causes resistance with clindamycin
aminoglycoside resistance in gram negatives

57
Q

Other altered target sites
DNA gyrase/Topoisomerase IV

A

Responsible for fluoroquinolone (ciprofloxacin, levofloxacin) resistance in Gram-negative and S. Pneumonia

58
Q

Efflux pumps and porin channels

A

Efflux pumps if overexpressed can build resistance
Important resistance mechanism for P. aeruginosa against carbapenems & S. pneumoniae against
macrolide antibiotics

Porin channels can cause resistance because the rate of antibiotic diffusion depends on porin channels
Most commonly seen with Enterobacterales and carbapenem-resistant P. aeruginos

59
Q

What is the mechanism of Staphylococcus aureus resistance to beta-lactams?

a) mecA gene
b) VanA gene
c) ermB gene
d) KPC gene

A

A. MecA

60
Q

Bactericidal definition

A

killing of the organism by acting on areas such as the cell wall, cell membrane, bacterial DNA

61
Q

Bacteriostatic Definition

A

Inhibit bacterial replication without killing the organism by inhibiting protein synthesis

62
Q

Concentration Dependent

A

Optimize killing with high doses
Exert effect when concentrations well above organism MIC

Fluoroquinolones (Levofloxacin, Ciprofloxacin)
-Concentration-dependent bactericidal activity fAUC 0-24/MIC

Aminoglycosides (Gentamicin, Tobramycin, Amikacin)
- Concentration-dependent bactericidal activity
C max/MIC

  • Optimal dosing achieved through Therapeutic drug monitoring and use of high dose extended interval
63
Q

Time dependent

A

optimize duration of exposure to binding site

All β-lactam antibiotics (penicillin, cephalosporin, carbapenem, monobactam)

Time that free drug concentration remains above MIC correlates with clinical and microbiological outcomes

fT>MIC Penicillin: 50% - if its Q12h we want at least 6 hours free time is over MIC
fT>MIC Cephalosporin: 60-70%
◦ fT>MIC Carbapenem: 40%
◦ Antibacterial properties
◦ Not rapidly bactericidal
◦ Time-dependent bactericidal activity
◦ Little to no PAE

64
Q

Beta- lactam Dosing Optimization

A

Maximize fT>MIC (as a % of dosing interval )
◦ Gram-negatives:
◦ Carbapenems: ≥40%; Penicillins: ≥50%; Cephalosporins: ≥ 60%
◦ Gram-positive: ≥40-50%

Strategies to maximize fT>MIC
◦ Increase dose, same interval (1g Q8h vs. 2g q8h)
◦ Same dose, shorter interval (1g Q12h vs. 1g Q6h)
◦ Continuous infusion
◦ Stability issues; need dedicated IV line
◦ Prolonged infusions
◦ Infuse dose over 3-4 hours
◦ Provides longer T>MIC than traditional infusions

65
Q

AUC/MIC Dependent (Vancomycin)

A

◦ Time-dependent bactericidal activity; very long PAE for Gram-positive organisms

◦ PD Target: AUC0-24 /MIC

◦ Goal AUC0-24/MIC ≅ 400-600
- assumes organism AUC of 1 mcg/mL

◦ Prolonged, elevated AUC0-24/MIC ≥ 600-700 mg*h/L is a risk factor for nephrotoxicity

◦ Dosing is patient-specific and achieved through TDM using Bayesian programs

66
Q

Which of the following describes the PK/PD parameters of meropenem?

a) Time-dependent antibiotic; fT>MIC 40% of the dosing interval
b) Concentration dependent antibiotic; fAUC/MIC
c) Time-dependent antibiotic; fT>MIC 80% of the dosing interval
d) Concentration dependent antibiotic; Cmax/MIC

A

Meropenem is a carbapenem meaning it is a time dependent drug so the correct answer is A

67
Q

Summary PK/PD aminoglycosides

A

Concentration dependent
C Max/MIC; AUC/MIC
Cidal

68
Q

Summary PK/PD B-lactams

A

Time dependent
FT>MIC
Cidal

69
Q

Summary PK/PD Vancomycin

A

Time Dependent
AUC (0-24)/MIC
Cidal (Slowly)

PHRM 865 - exam 1 (11 decks)

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