Intro to ID pt2 Flashcards
what color do gram-pos bacteria appear as
purple
what color do gram-neg bacteria appear as
red/pink
which one has thick cell wall
gram positive
what is the bacteria called when it does not stain using normal methods
atypical bacteria
what is it called when the bacteria is resistant to acids/ethanol based decolorization procedures
acid-fast bacilli (AFB)
2 most important morphologies for gram-positive bacteria
COCCI and Bacilli
Cocci: categorized into clusters and chains
A. Anaerobic
B. Aerobic
B
aerobic cocci:
strep A and strep B belong to this categorization:
A. clusters
B. pairs/chains
B
aerobic cocci:
coagulase tests are done in which categorization:
A. Clusters
B. Pairs/chains
A
Enterococcus faecium and Enterococcus faecalis fall under what categorization?
A. anaerobic bacilli
B. Aerobic bacilli
C. Aerobic cocci clusters
D. Aerobic cocci pairs/chains
D, these are also nonhemolytic
T or F: Most medically important pathogens are cocci rather than bacilli
true
T or F:
Staphylococcus form pairs or chains and Streptococci & Enterococci appear in clusters
false, other way around
what biochemistry testing do you use for staphylococci from streptococci
catalase test
what biochemistry test do you use for staphylococcus aureus from coagulase-negative staphylococcus (CoNS)
coagulase test
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, pretty much choose that if you see coagulase positive i think
what categorization does enterobacterales fall under?
gram-negative aerobic bacilli
how do you remember the enterobacteriales lactose-fermenters?
CEEK out lactose
Citrobacter
Enterobacter
E.Coli
Klebsiella
(THESE ARE OXIDASE-NEGATIVE)
do lactose-fermenters fall under anaerobic or aerobic bacilli
aerobic
T or F:
Non-lactose fermenters tend to be more drug resistant than their friends the lactose fermenters
true
try to think of things for slide 15
okay will do buddy
what is one common bacteria that falls under atypical (at least on slide 16 it does)
chlamydia
for gram-negative morphology, what is the predominant pathogen type?
bacilli
what kind of test helps distinguish between enteric vs. non-enteric lactose fermenters
oxidase, thats why some are oxidase positive and some are oxidase negative duh
what organisms are “slow growers” that require special supplemental media
fastidious organisms
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, he said to know this for the exam
whats another way to say non-enteric lactose fermenter
oxidase-positive lactose-fermenter
what type of protein are transpeptidases, carboxypeptidases, and endopeptidases
penicillin-binding proteins (PBPs)
of the 3 PBPs, which one is most important and why?
transpeptidase, catalyzes the final cross linking in the peptidoglycan structure
where are penicillin-binding proteins located?
in bacteria
what significant thing binds to penicillin-binding proteins
Beta lactams!!!*
what are PBPs most essential for?
cell-wall synthesis
what are the hydrophilic channels that permit diffusion of essential nutrients and small hydrophilic compounds called
porins
what is the compartment between cell membrane and cell wall (or outer membrane if GN) called?
periplasmic space
which of the following is vital for bacterial protein secretion, folding, quality control and acts as a reservoir for virulence factors?
A. Cytoplasmic membrane
B. Peptidoglycan layer (cell wall)
C. Outer membrane (GN)
D. Periplasmic space
D
what are the two mechanisms by which intrinsic resistance occurs?
absence of target site
bacterial cell impermeability (cant get through)
what is the definition of acquired resistance
initially susceptible but develop resistance due to a mechanism
what are the two mechanisms by which acquired resistance occurs (general ass answers)
mutation in bacterial DNA
acquisition of new DNA
cephalosporins vs. enterococci
A. intrinsic
B. Acquired
A
Stable derepression of AmpC
A. intrinsic
B. Acquired
B
Acquisition of KPC gene in GNRs
A. intrinsic
B. Acquired
B
B-lactams vs. mycoplasma
A. intrinsic
B. Acquired
A
plasmid, transposons, and conjugation all relate to which type of resistance?
acquired
transferable between organisms
A. Plasmid
B. Conjugation
C. Transposons
A
move from plasmid to chromosome or vice versa
A. Plasmid
B. Conjugation
C. Transposons
C
most common and referred to as “mating bridge”
A. Plasmid
B. Conjugation
C. Transposons
B
referred to as “jumping genes”
A. Plasmid
B. Conjugation
C. Transposons
C
what is the MOA of beta-lactamase?
hydrolyze beta-lactam ring by splitting amide bond -> inactivating drugs
what are the two classification systems of beta-lactamase?
ambler class
Bush-Jacoby-Medeiros
classified according to AA structure (A-D)
A. ambler class
B. Bush-Jacoby-Medeiros
A
classified according to functional characteristics
A. ambler class
B. Bush-Jacoby-Medeiros
B
serine beta-lactamases contain a _____ residue at active site
serine no shit
metallo beta-lactamases contain _____ residue at active site
zinc, easy to remember bc its a metal
uses acylation and deacylation in mechanism
A. serine beta-lactamase
B. zinc beta-lactamase
A
skips intermediate step and just opens ring as part of its mechanism
A. serine beta-lactamase
B. zinc beta-lactamase
B, think metal can force through things and shit idk
Ambler classification:
what do narrow-spectrum B-lactamases hydrolyze?
penicillin
Ambler classification:
Narrow-spectrum B-lactamases are produced primarily by what bacteria?
enterobacterales
Ambler classification:
what do Extended-spectrum B-lactamases hydrolyze?
narrow & extended spectrum B-lactam (3rd gen cephalosporins)
Ambler classification:
bolded enzyme example for extended-spectrum B-lactamases (ESBL)
CTX-M-15 **
Ambler classification:
bolded enzyme(s) example for serine carbapenemases **
KPC-1, KPC-2, KPC-3
ambler classification:
what do serine carbapenemases hydrolyze?
carbapenems (WOAH)
Ambler classification:
what do metallo-B-lactamases hydrolyze?
carbapenems
T or F:
Serine carbapenems are more broad than metallo ones
false, other way around
Ambler classification:
bolded enzyme(s) example for metallo-B-lactamases
NDM-1 **
cephalosporinases didnt have any hydrolysis mechanisms listed, what was the one word characteristic used in that slot instead?
inducible
Ambler classification:
bolded enzyme(s) example for cephalosporinases
Amp-C*
Ambler classification:
bolded enzyme(s) example for OXA-type
OXA-48 (no way)
ambler classification:
what does OXA-type hydrolyze (3)
oxacillin, oxyimino B-lactams, and carbapenems
which resistant-related enzyme is most prevalent in Escherichia coli, Klebsiella pneumoniae/oxytoca, and Proteus mirabilis? What ambler class is it?
CTX-M, ESBLs
which of the following is not a beta-lactam agent?
A. Penicillin
B. Ciprofloxacin
C. Monobactams
D. Cephalosporins
B, thats a quinolone
what is the treatment of choice when dealing with ESBL-based resistance?
carbapenems
in ESBL-based resistance, piperacillin/tazobactam is an option for ______ source only
urinary
what enzyme is responsible for the most frequent cause of carbapenem-resistant enterobacterales (CRE)?
carbapenemase
T or F:
CRE leads to resistance of the whole beta-lactam class
true
look at the tx options on slide 34 again that looks wrong somehow
okay
T or F:
Metallo-B-lactamases confer resistance to all B-lactams
false, the exception is monobactams (aztreonam)
Cefiderocol; aztreonam + ceftazidime/avibactam are the only treatment option for what ambler class type?
metallo-B-lactamases
which ambler class and type is primarily found in acinetobacter baumannii and pseudomonas aeruginosa?
Class D, OXA-type
2 tx options for OXA-type resistance
cefiderocol
sulbactam/durlobactam
T or F:
carbapenem-resistant enterobacterales means that carbapenemases are present
false (slide 37)
Efflux pumps and porin mutations
A. CP(carbapenem producing)-CRE
B. Non-CP-CRE
B
AmpC and ESBLs
A. CP (carbapenem producing)-CRE
B. Non-CP-CRE
B
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.
What type of antibiotic resistance is present?
A. Non-CP CRE
B. ESBL
C. NDM
D. KPC
B, CTX-M = ESBL
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.
What is the recommended treatment option?
A. Meropenem
B. Meropenem/vaborbactam
C. Aztreonam + Ceftazidime/avibactam
D. Piperacillin/tazobactam
A, treatment of choice for ESBL is carbapenems, dont know what the combo one is though
mechanisms of AmpC beta-lactamases:
- inducible via ____________ ________ AmpC genes
- Non-inducible chromosomal resistance via __________
- ________-mediated resistance
- chromosomally encoded
- mutations
- plasmid
what does “inducible via chromosomally encoded AmpC genes mean in english?
some bacteria produce AmpC enzymes when exposed to certain antibiotics, making them resistant
T or F:
Non-inducible chromosomal resistance via mutations can happen without exposure to antibiotics
true actually
what does plasmid-mediated resistance mean in english?
resistance genes can be carried on plasmids which are small DNA fragments that can transfer between bacteria which spreads resistance
which of the following choices would inhibit AmpC?
A. avibactam
B. clavulanic acid
C. sulbactam
D. tazobactam
A, this is a “newer” B-lactamase inhibitor meaning that it is actually able to inhibit AmpC
what is the easy way to remember common bacteria producing AmpC beta-lactamases
HECK-YES:
Hafnia alvei
Enterobacter cloacae
Citrobacter freundii
Klebsiella aerogenes
Yersinia enterocolitica
if something is called an “AmpC inducer”, what does this mean?
it means it is a bacteria that produces AmpC when exposed to certain antibiotics
if you were to add “ma’am” to the end of HECK YES, what bacteria would you be talking about?
Morganella morganii
Aeromonas hydrophila
what in the fuck is slide 42 trying to say
no idea
is Ceftriaxone a strong or weak AmpC inducer?
weak
what is the significance of ceftriaxone being a weak inducer?
it doesnt stimulate production of ampc as much as other options, making it less likely to cause resistance
go look at slide 44
yes sir
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.
What could explain his sudden decompensation?
A. cloacae harbors an ESBL gene and this was induced with ceftriaxone treatment
B. cloacae harbors a KPC gene and this was induced with ceftriaxone treatment
C. cloacae harbors an AmpC gene and this was induced with ceftriaxone treatment
D. cloacae harbors a NDM gene and this was induced with ceftriaxone treatment
C, because ceftriaxone is a weak inducer of AmpC
do carbapenems have a high or low susceptibility to AmpC hydrolysis?
low, this makes them a good treatment option
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. Ceftriaxone caused resistance through inducing ampC.
What antibiotic change do you recommend?
Switch to
A. Piperacillin/tazobactam
B. Switch to Cefepime
C. Switch to Ceftazidime
D. Switch to Aztreonam
B
what is the most common method of aminoglycoside resistance?
enzymatic inactivation
what are the 3 mechanisms involved in enzymatic inactivation for aminoglycosides?
acetylation
nucleotidylation
phosphorylation
what is the mechanism of vancomycin resistance in enterococci species?
altered target sites
vancomycin MOA
a glycopeptide antibiotic that inhibits bacterial cell wall synthesis by binding to D-Ala-D-Ala terminal of peptidoglycan precursors
T or F:
Vanco spec of activity is limited to gram-negative bacteria only
false, GP only
most common resistance mech for vanco
VanA or VanB mediated resistance by altering any formation of D-Ala whatever
two treatment options for VRE
daptomycin
linezolid
T or F:
Alterations in PBPs (penicillin binding proteins) leads to B-lactam resistance
true
where do we most commonly see alterations in PBPs?
methicillin-resistant Staphylococcus aureus (MRSA)**
MRSA related resistance is due to expression of what very important gene?
mecA
so if you see mecA what two things do you think about and vice versa
MRSA
Staph aureus
do porin channels help antibiotics into bacteria or pump them out?
helps perfuse into bacteria
Important resistance mechanism for P. aeruginosa against carbapenems
A. efflux pumps
B. Porin channels
A
Important resistance mechanism for S. pneumoniae against macrolide antiobiotics
A. efflux pumps
B. Porin channels
A
Important resistance mechanism for Enterobacterales and carbapenem-resistant P. aeruginosa
A. efflux pumps
B. Porin channels
B
What is the mechanism of Staphylococcus aureus resistance to beta-lactams?
A. mecA gene
B. VanA gene
C. ermB gene
D. KPC gene
A, always associate with mecA
Based on ADME
A. PK
B. PD
A
PK/PD terminology:
conc dependent
max conc at binding site
PK/PD terminology:
time dependent
optimize duration of exposure at binding site
PK/PD terminology:
Bactericidal
kills organism
PK/PD terminology:
Bacteriostatic
inhibit bacterial replication WITHOUT killing organism
PK/PD terminology:
AUC
overall drug exposure over a certain time
T or F:
Time that free drug conc remains above MIC correlates with clinical and microbiological outcomes (fT>MIC)
true, basically just saying that the longer the drug is above MIC and the has a high concentration correlates with how well the drug kills bacteria
Penicillin
A. fT>MIC 50%
B. fT>MIC 60-70%
C. fT>MIC 40%
A
Cephalosporin
A. fT>MIC 50%
B. fT>MIC 60-70%
C. fT>MIC 40%
B
Carbapenem
A. fT>MIC 50%
B. fT>MIC 60-70%
C. fT>MIC 40%
C
4 ways to maximize fT>MIC
- inc dose, same interval
- same dose shorter interval
- cont. infusion
- prolonged infusions
Goal AUC0-24/MIC for vanco
400-600
prolonged or elevated AUC0-24/MIC for vanco has a risk for what and at what range?
nephrotox
600-700
fluoroquinolones
A. time dependent
B. conc dependent
B**
aminoglycosides
A. time dependent
B. conc dependent
B*****
B-lactams (penicillin, cephalosporin, carbapenem, monobactam)
A. time dependent
B. conc dependent
A
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 (40% for carbapenems)
vancomycin
A. time dependent
B. conc dependent
A
