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

Intro to ID part 2 Flashcards

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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
gram negative aerobic bacilli Fastidious
Campylobacter Helicobacter Bartonella HACEK* organisms
26
Atypical
These will not stain on a gram test Chlamydia trachomatis Legionella pneumophila Mycoplasma pneumonia
27
Spirochetes
treponema pallidum Borrelia burgdorferi
28
What does lactose fermentation tell us
helps us identify and distinguish between enteric vs non-enteric lactose fermenters
29
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 B is a Enteric coded lactose fermenter C is a enteric coded non-lactose fermenter D is non-enteric coded lactose fermenter
30
what are Penicillin Binding proteins
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
Intrinsic Resistance
when the species is always been resistant to the given antibiotic due to absence of a target site or the bacterial cell impermeability
32
Acquired resistance
when species is initally susceptible but develop resistance due to some mechanism due to mutation in bacterial DNA or Acquisition of new DNA
33
Aquired resistance examples
Plasmid - transferable between organisms Transposons - move from plasmid to chromosome or vice versa Conjugation - most common
34
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
B
35
what are the 4 mechanisms of antibiotic resistance
1. Altered cell wall protein/ decreased porin production 2. Increased efflux pumps 3. increased drug inactivating enzymes 4. modified drug target
36
mechanism of resistance drug inactivating enzymes Beta - lactamase
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
Ambler classification of beta lactamase Class 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
Ambler classification of beta lactamase Class B
Metallo B lactamases - enzyme example NDM-1
39
Ambler classification of beta lactamase Class C
Cephalosporinases - enzyme example AMP- C
40
Ambler classification of beta lactamase Class D
OXA-type - enzyme example OXA-48
41
Ambler class A : ESBLs
Plasmid mediated Treatment choice: Meropenem, Imipenem, Doripenem, Ertapenem can also use piperacillin/tazobactam for Urinary source ONLY
42
Ambler class A: Carbapenemase
Treatment options: B lactam: ceftazidime/avibactam, Meropenem/Vaborbactam, impienem/cilastatin/relebactam non-B-lactam: plazomicin, eravacycline, omadacycline
43
Ambler class B: Metallo B lactamases
confer resistance to all B-lactams except monobactams Treatment is limited but option is Cefiderocol
44
Ambler Class D: OXA type
Primairly found in Ainetobacter baumannii and Pseudomonas aeruginosa Treatment options: Cefiderocol or Sulbactam/durlobactam
45
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
B - ESBL
46
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
ESBL resistance present and patient should be started on A
47
Ambler Class C: AmpC
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
AmpC induction mechanism
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
AmpC inducers High susceptibility to AmpC hydrolysis
Strong inducers - penicillin and ampicillin Weak inducers - ceftriaxone
50
AmpC inducers low susceptibility to AmpC hydrolysis
Strong inducers - carbapenems (imipenem, Meropenem, ertapenem) Weak inducers - Cefepime
51
Treatment of stably derepressed mutants
First line cefepime
52
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
Q1 C Q2 B
53
Enzymatic inactivation: amino-glycoside- Modifying Enzyme
3 mechanisms acetylation, nucleotidylation, Phosphorylation Modify aminoglycoside structure by transferring the indicated chemical group to specific side chain
54
Altered target site: Cell wall precursor Mechanism of Vancomycin resistance in enterococci Species What is resistance mediated by and what is the treatment
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
Altered Target site: Penicillin Binding Proteins
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
Other altered target sites Ribosomal target
Responsible for macrolide resistance in S. Pneumoniae ermB gene causes resistance with clindamycin aminoglycoside resistance in gram negatives
57
Other altered target sites DNA gyrase/Topoisomerase IV
Responsible for fluoroquinolone (ciprofloxacin, levofloxacin) resistance in Gram-negative and S. Pneumonia
58
Efflux pumps and porin channels
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
What is the mechanism of Staphylococcus aureus resistance to beta-lactams? a) mecA gene b) VanA gene c) ermB gene d) KPC gene
A. MecA
60
Bactericidal definition
killing of the organism by acting on areas such as the cell wall, cell membrane, bacterial DNA
61
Bacteriostatic Definition
Inhibit bacterial replication without killing the organism by inhibiting protein synthesis
62
Concentration Dependent
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
Time dependent
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
Beta- lactam Dosing Optimization
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
AUC/MIC Dependent (Vancomycin)
◦ 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
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
Meropenem is a carbapenem meaning it is a time dependent drug so the correct answer is A
67
Summary PK/PD aminoglycosides
Concentration dependent C Max/MIC; AUC/MIC Cidal
68
Summary PK/PD B-lactams
Time dependent FT>MIC Cidal
69
Summary PK/PD Vancomycin
Time Dependent AUC (0-24)/MIC Cidal (Slowly)

PHRM 865 - exam 1 (11 decks)

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