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Beta-Lactams Questions Flashcards

1
Q

What classes of drugs make up beta-lactams?

A
  • penicillins
  • cephalosporins
  • carbapenems
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2
Q

How are monobactams different than beta-lactams?

A
  • structurally similar but lack one of the two rings that other beta-lactams have
  • have little to no cross-allergenicity with other beta-lactams
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3
Q

What do all beta-lactams have in common?

A
  • can cause hypersensitivity reactions
  • seizures can result from very high doses of any beta-lactam (and some cause other neurologic effects)
  • share a mechanism of action
  • lack activity against atypical organisms
  • all (except one cephalosporin) lack activity against MRSA
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4
Q

Describe a beta-lactam hypersensitivity reaction.

A

Ranges from:

  • mild rashes
  • drug fever
  • acute interstitial nephritis (AIN)
  • anaphylaxis
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5
Q

What is responsible for cross-sensitivity between classes of beta-lactams?

A

Similarities between side chains

  • likelihood of allergic reactions can be predicted by side chains
  • cross-sensitivity seems to be lower than previously thought
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6
Q

Do beta-lactams need to be adjusted for a patient’s renal function?

A

Yes

-if dose not adjusted, accumulation to toxic levels can occur (seizures)

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7
Q

Describe the MOA of beta-lactams.

A

Inhibition of transpeptidases (penicillin-binding proteins) in the bacterial cell wall

Inhibit cross-linking of peptidoglycan in the cell wall (leading to autolysis and cell death)

-giving two beta-lactams in combination for the same infection is generally not useful (but also not antagonistic)

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8
Q

What class of organisms do beta-lactams lack activity against?

A

Atypical organisms (such as):

  • Mycoplasma pneumoniae
  • Chlamydophila pneumoniae

-add another drug to the regimen if these organisms suspected (as in community-acquired pneumonia)

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9
Q

What specific organism do beta-lactams lack activity against?

A

MRSA

  • add vancomycin or another drug if this organism suspected
  • only exception is ceftaroline (cephalosporin)
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10
Q

What is the half life of penicillins?

A

Very short half lives (<2 hours)

  • must be dosed multiple times per day
  • half lives of most penicillins are prolonged in renal dysfunction
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11
Q

What is a severe reaction of penicillins?

A

Hypersensitivity reactions

  • if a patient has a true IgE-mediated hypersensitivity reaction, avoid other penicillins
  • if reaction not severe, may use cephalosporins or carbapenems
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12
Q

Describe the absorption of of penicillins.

A

Many are relatively poorly absorbed

  • this can lead to diarrhea when oral therapy is needed
  • often a conversion from IV to PO means there will be a substantial decrease in the amount of act or drug in the body
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13
Q

Describe penicillin research development.

A

Development focused on either:

  • improved activity against staphylococci (MSSA)
  • or GNRs

Then beta-lactamase inhibitors were discovered

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14
Q

Name the natural penicillins.

A
  • penicillin G

- penicillin V

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15
Q

What organisms do natural penicillins have GOOD activity against?

A
  • Treponema pallidum

- most streptococci (including S. pneumoniae)

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16
Q

What organisms do natural penicillins have MODERATE activity against?

A

-enterococci

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17
Q

What organisms do natural penicillins have POOR activity against?

A

-almost everything else

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18
Q

How do the adverse effects of natural penicillins compare to other beta-lactams?

A

Similar to those of other beta-lactams

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19
Q

What is the half life of natural penicillins?

A

Very short half life

  • must be dosed frequently or given by continuous infusion
  • other more conveniently dosed narrow spectrum beta-lactams are available for most organisms treatable with penicillin
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20
Q

Describe long acting depot formulations of natural penicillin.

A

Procaine / Benzathine

  • given IM
  • doses vary considerably
  • giving them IV can be fatal
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21
Q

What are the dosage forms of natural penicillins?

A
  • penicillin V is the oral form

- penicillin G is the IV form

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22
Q

What is the drug of choice for syphilis?

A

Penicillin G

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23
Q

Is penicillin a GOOD empiric choice for most infections?

A

No, it is a POOR empiric choice because of resistance

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24
Q

The IV penicillin breakpoints for S. pneumoniae were redefined in 2008 by CLSI (lowered the percentage of S. pneumoniae isolates considered resistant to penicillin considerably. What are the caveats?

A
  • only applies to IV penicillin
  • does not apply to CNS infections (old breakpoints remain in effect)
  • breakpoints are useful predictors of treatment success (but are not always set correctly)
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25
What are natural penicillins good for?
- syphilis (particularly neurosyphilis) | - also used in susceptible streptococcal infections (ex: pharyngitis, endocarditis)
26
Name the antistaphylococcal penicillins?
- Nafcillin - Oxacillin - Dicloxacillin - methicillin - cloxacillin
27
Antistaphylococcal penicillins are resistant to penicillinases. However, like natural penicillins, what organisms are they not effective against?
Have poor gram negative activity like natural penicillins
28
What organisms do antistaphylococcal penicillins have GOOD activity against?
- MSSA | - streptococci
29
What organisms do antistaphylococcal penicillins have POOR activity against?
- GNRs - enterococci - anaerobes - MRSA
30
How do the adverse effects of antistaphylococcal penicillins compare to other beta-lactams?
Similar -possibly higher incidence of AIN
31
What is the half life of antistaphylococcal penicillins?
- short half life - must be dosed frequently - cause phlebitis
32
Why may a first generation cephalosporin be a better option than an antistaphylococcal penicillin in most patients?
- less risk of phlebitis - easier to administer - better tolerated - good choice for most patients
33
How are antistaphylococcal penicillins eliminated?
Eliminated from the body in large part by the LIVER -do NOT need to be adjusted in cases of renal dysfunction
34
Are antistaphylococcal penicillins interchangeable with each other?
YES
35
What drugs are the standard tests for antistaphylococcal penicillin susceptibility usually done with?
- oxacillin | - cefoxitin
36
What are antistaphylococcal penicillins good for?
Infections caused by MSSA; ex: - endocarditis - skin and soft tissue infections
37
Do beta-lactams or vancomycin kill staphylococci more quickly?
Beta-lactams - patients with an MSSA infection who lack a serious beta-lactam allergy should be switched to a beta-lactam - has been shown to be an important difference in serious infections
38
Name the aminopenicillins.
- amoxicillin | - ampicillin
39
Why do aminopenicillins have better gram negative coverage compared to previous classes of penicillins?
More water-soluble (pass through porin channels in the cell wall of some gram negative organisms)
40
Are aminopenicillins active against staphylococci?
Rarely; they almost always produce penicillinases
41
What organisms do aminopenicillins have GOOD activity against?
- streptococci | - enterococci
42
What organisms do aminopenicillins have MODERATE activity against?
- enteric GNRs | - Haemophilus
43
What organisms do aminopenicillins have POOR activity against?
- staphylococci - anaerobes - Pseudomonas
44
How do the adverse effects of aminopenicillins compare to other beta-lactams?
Similar -have high incidence of diarrhea when given orally
45
Which aminopenicillin is a better choice for oral therapy?
Amoxicillin - more bioavailable - better tolerated - administered less frequently Use ampicillin for IV therapy
46
What is a drug of choice for susceptible enterococci?
Ampicillin
47
Which species of enterococci is almost always susceptible to ampicillin?
Enterococcus faecalis
48
Which species of enterococci is almost often resistant to ampicillin?
Enterococcus faecium
49
Why are aminopenicillins often listed as alternative regimens for UTIs in pregnant women?
- pregnancy category B | - eliminated renally
50
What are some precautions when using aminopenicillins in pregnant women for UTIs?
- resistance to Escherichia coli is very high | - susceptibility testing should be performed
51
Why should follow-up cultures always be performed in pregnant women with UTIs?
Even asymptomatic bacteruria is dangerous for them
52
What are aminopenicillins good for?
Infections caused by susceptible: - GNRs - enterococci - streptococci
53
Why are aminopenicillins used only infrequently in complicated nosocomial infections?
Because resistance among GNRs is prevalent
54
What is amoxicillin frequently prescribed for?
Infections of the upper respiratory tract; ex: - streptococcal pharyngitis (strep throat) - otitis media (ear infection)
55
How is bactericidal activity achieved against enterococci?
Combining ampicillin (or any other beta-lactam) with an aminoglycoside
56
When should a bactericidal antibiotic regimen be considered against enterococci?
Serious infections; ex: -endocarditis
57
Name the antipseudomonal penicillins.
- piperacillin - ticarcillin Commonly used now with a beta-lactamase inhibitor
58
Are the antipseudomonal penicillins active against staphylococci?
NO - just as susceptible to beta-lactamases as amoxicillin and ampicillin - strains of GNRs that produce beta-lactamases are also resistant
59
What organisms do antipseudomonal penicillins have GOOD activity against?
- P. aeruginosa - streptococci - enterococci
60
What organisms do antipseudomonal penicillins have MODERATE activity against?
- enteric GNRs | - Haemophilus
61
What organisms do antipseudomonal penicillins have POOR activity against?
- staphylococci | - anaerobes
62
How do the adverse effects of antipseudomonal penicillins compare to other beta-lactams?
Similar
63
Name the penicillin/beta-lactamase inhibitor combinations.
- ampicillin/sulbactam - amoxicillin/clavulanate - piperacillin/tazobactam
64
What is the MOA of beta-lactamase inhibitors?
- counter beta-lactamases - mimic the structure of beta-lactams - have little antimicrobial activity on their own - bind to beta-lactamases IRREVERSIBLY (preventing the beta-lactamase from destroying any beta-lactams that are co-administered - beta-lactamase inhibitors structurally resemble beta-lactams and bind to many beta-lactamases (rendering them unable to inactivate the coadministered beta-lactam)
65
Do beta-lactamase inhibitors enhance the activity of beta-lactams?
No - they only free up the beta-lactam to kill the organism that it has intrinsic activity against - they restore activity; not add to it
66
What organisms do penicillin/beta-lactamase inhibitor combinations have GOOD activity against?
- MSSA - streptococci - enterococci - many anaerobes - enteric GNRs - P. aeruginosa (only piperacillin/tazobactam)
67
What organisms do penicillin/beta-lactamase inhibitor combinations have MODERATE activity against?
-GNRs with advanced beta-lactamases
68
What organisms do penicillin/beta-lactamase inhibitor combinations have POOR activity against?
- MRSA | - ESBL (extended-spectrum beta-lactamase) producing GNRs
69
How do the adverse effects of penicillin/beta-lactamase inhibitor combinations compare to other beta-lactams?
Similar
70
Which beta-lactamase inhibitor combination is available orally?
Amoxicillin/clavulanate -higher doses associated with more diarrhea
71
Dose the dose of clavulanate change for different doses of oral amoxicillin?
NO Fixed dose of 125mg
72
Are beta-lactamase inhibitors effective against all beta-lactamases?
NO -new beta-lactamases are continually being discovered and are becoming more prevalent
73
Are beta-lactamase inhibitors available outside of the combination products?
No -except for study purposes
74
What beta-lactamase inhibitor has useful antimicrobial activity?
Sulbactam - against Acinetobacter baumannii (highly drug resistant GNR that causes nosocomial infections) - high doses of ampicillin/sulbactam can be used for treatment
75
Which beta-lactamase inhibitor is more potent at inhibiting beta-lactamases?
Clavulanate -higher doses of sulbactam are given to account for this
76
How do the spectra of amoxicillin/clavulanate and ampicillin/sulbactam compare?
Nearly identical -differences in susceptibility testing may be due to the low concentrations of sulbactam used in tests
77
What are penicillin/beta-lactamase inhibitor combinations good for?
-empiric therapy of nosocomial infections, particularly nosocomial pneumonia (not aminopenicillin based combinations) Good empiric choice for mixed infections (have activity against aerobes and anaerobes); ex: - intra-abdominal infections - diabetic ulcers - aspiration pneumonia
78
When is amoxicillin/clavulanate used?
Upper and lower respiratory tract infections -when beta-lactamase producing organisms are found/suspected Can also be used for UTIs when resistance to other drugs is seen -should not be given for a short 3 day course (such as FQ or TMP/SMX)
79
Are penicillin/beta-lactamase inhibitor combinations good for empiric or definitive therapy?
Empiric -poor choice for definitive therapy if alternatives available
80
What do all cephalosporins have in common?
- have some cross-allergenicity with penicillins | - generally more resistant to beta-lactamases than penicillins are
81
What is the likelihood of cross-reactivity between penicillin and cephalosporin allergies?
- oft-quoted 10% - reasonable estimate is no more than 3-5% - some publications support even lower numbers (particularly for later-generation agents) - evidence suggests that similar side chains are the reason for cross-reactivity - be skeptical of nausea; take hives and any signs of anaphylaxis very seriously
82
What are penicillinases?
Beta-lactamases that are: - active against penicillins - inactive against cephalosporins
83
What are cephalosporinases?
Beta-lactamases that inactivate cephalosporins -increasing in prevalence
84
Name the 1st generation cephalosporins?
- Cefazolin - Cephalexin - cefadroxil - cephalothin
85
What is cefazolin?
1st generation cephalosporin -parenteral
86
What is cephalexin?
1st generation cephalosporin -oral
87
What is cefadroxil?
1st generation cephalosporin -oral
88
What is cephalothin?
1st generation cephalosporin -parenteral
89
What is the most commonly used class of antibiotics in the hospital?
1st generation cephalosporins -used immediately prior to surgery to prevent surgical site infections
90
Why are 1st generation cephalosporins ideal for prophylaxis of surgical site infections and treating skin and skin structure infections?
- spectrum of activity - inexpensive cost - low incidence of adverse effects
91
What organisms do 1st generation cephalosporins have GOOD activity against?
- MSSA | - streptococci
92
What organisms do 1st generation cephalosporins have MODERATE activity against?
-some enteric GNRs
93
What organisms do 1st generation cephalosporins have POOR activity against?
- enterococci - anaerobes - MRSA - Pseudomonas
94
How do the adverse effects of 1st generation cephalosporins compare to other beta-lactams?
Similar
95
Why are 1st generation cephalosporins a good alternative to antistaphylococcal penicillins?
- cause less phlebitis | - infused less frequently
96
How do 1st generation cephalosporins differ from antistaphylococcal penicillins?
May not cross the blood-brain barrier -should not be used in CNS infections
97
Which 1st generation cephalosporins are available orally?
- cephalexin | - cefadroxil
98
Which 1st generation cephalosporins are available parenterally?
- cefazolin | - cephalothin
99
What are 1st generation cephalosporins good for?
- skin and skin structure infections - surgical prophylaxis - staphylococcal bloodstream infections - osteomyelitis - endocarditis (MSSA)
100
How are 1st generation cephalosporins used for surgical prophylaxis in the hospital?
- limit the duration of use - administering more than one dose should be the exception - giving more than 24 hours worth is rarely justified - extended use does not lower infection rates/can select for more resistant organisms later in the hospital stay
101
Name the 2nd generation cephalosporins.
- Cefuroxime - Cefoxitin - Cefotetan - Cefprozil - loracarbef - cefmetazole - cefonicid - cefamandole - cefaclor
102
What is cefuroxime?
2nd generation cephalosporin -IV/PO
103
What is cefoxitin?
2nd generation cephalosporin -IV
104
What is cefotetan?
2nd generation cephalosporin -IV
105
What is Cefprozil?
2nd generation cephalosporin -oral
106
What is loracarbef?
2nd generation cephalosporin -oral
107
What is cefmetazole?
2nd generation cephalosporin -IV
108
What is cefonicid?
2nd generation cephalosporin -IV
109
What is cefamandole?
2nd generation cephalosporin -IV
110
What is cefaclor?
2nd generation cephalosporin -oral
111
How are 2nd generation cephalosporins different than 1st generation?
- have better gram-negative activity - somewhat weaker gram-positive activity - more stable against gram-negative beta-lactamases
112
What organisms are 2nd generation cephalosporins particularly active against?
- H. influenzae | - N. gonorrhoeae
113
What organisms do 2nd generation cephalosporins have GOOD activity against?
- some enteric GNRs - Haemophilus - Neisseria
114
What organisms do 2nd generation cephalosporins have MODERATE activity against?
- streptococci - staphylococci - anaerobes (only cefmetazole, cefotetan, cefoxitin)
115
What organisms do 2nd generation cephalosporins have POOR activity against?
- enterococci - MRSA - Pseudomonas
116
How do the adverse effects of 2nd generation cephalosporins compare to other beta-lactams?
Similar
117
What cephalosporins have the MTT side chain?
- cefmetazole - cefotetan - cefamandole
118
What does MTT stand for?
N-methylthiotetrazole
119
What side effects do cephalosporins with the MTT side chain have?
- can inhibit vitamin K production (prolong bleeding) | - cause a disulfiram-like reaction when coadministered with ethanol
120
What are cephamycins?
A sub-group of second generation cephalosporins that have anaerobic activity - have activity against many anaerobes in the GI tract - good intrinsic anaerobic activity (resistance is increasing in Bacteroides fragilis group infections) - cefmetazole - cefotetan - cefoxitin
121
Which cephalosporins are often used for surgical prophylaxis in abdominal surgery?
- cefoxitin | - cefotetan
122
Which cephalosporin is a carbacephem?
Loracarbef
123
Do 2nd generation cephalosporins cross the blood-brain barrier well?
No -do not use them to treat CNS infections
124
What are 2nd generation cephalosporins good for?
- upper respiratory tract infections - community-acquired pneumonia - gonorrhea - surgical prophylaxis (cephamycins)
125
How should cephamycins be used for surgical prophylaxis?
-limit duration of antibiotic exposure after surgery If infection develops, use alternative agents: - beta-lactamase inhibitor combinations - another gram-negative agent + metronidazole
126
Name the 3rd generation cephalosporins.
- Ceftriaxone - Cefotaxime - Ceftazidime - Cefdinir - cefpodoxime - cefixime - ceftibuten
127
What is ceftriaxone?
3rd generation cephalosporin
128
What is cefotaxime?
3rd generation cephalosporin
129
What is ceftazidime?
3rd generation cephalosporin
130
What is cefdinir?
3rd generation cephalosporin
131
What is cefpodoxime?
3rd generation cephalosporin
132
What is cefixime?
3rd generation cephalosporin
133
What is ceftibuten?
3rd generation cephalosporin
134
How do 3rd generation cephalosporins compare to previous generations?
- greater gram-negative activity - most have good streptococcal activity (generally lesser staphylococcal activity) - considered broad-spectrum agents
135
What organisms do 3rd generation cephalosporins have GOOD activity against?
- streptococci (except ceftazidime: poor) - enteric GNRs - Pseudomonas (ceftazidime)
136
What organisms do 3rd generation cephalosporins have MODERATE activity against?
-MSSA (except ceftazidime: poor)
137
What organisms do 3rd generation cephalosporins have POOR activity against?
- enterococci - anaerobes - MRSA - Pseudomonas (except ceftazidime)
138
How do the adverse effects of 3rd generation cephalosporins compare to other beta-lactams?
Similar
139
What class of antibiotics has been shown to be one of the classes with the strongest association with Clostridium difficile-associated diarrhea?
3rd generation cephalosporins
140
Which 3rd generation cephalosporin has the MTT side chain?
Cefpodoxime
141
How is ceftazidime the exception among 3rd generation cephalosporins?
- antipseudomonal | - lacks clinically useful activity against gram-positive organisms
142
Which 3rd generation cephalosporins cross the blood-brain barrier effectively to treat CNS infections?
- ceftriaxone - cefotaxime - ceftazidime Ceftazidime is a poor choice for community-acquired meningitis (in which S. pneumoniae predominates)
143
Which generation of cephalosporins is notorious for inducing resistance among GNRs?
3rd generation cephalosporins -can be useful in nosocomial infections but too much broad spectrum utilization can result in harder to treat organisms
144
What cephalosporin is a drug of choice for gonorrhea?
One time dose of ceftriaxone IM - 125mg (old dose) - 250mg (current dose) due to increasing resistance
145
What drug should be added to a patient being treated for gonnorhea?
Azithromycin - adds empiric therapy for chlamydida - may reduce emergence of ceftriaxone resistance
147
Does ceftriaxone need to be adjusted for renal dysfunction?
No -however, does effectively treat UTIs
148
Which 3rd generation cephalosporin is safer in neonates: ceftriaxone or cefotaxime?
Cefotaxime
149
Why is ceftriaxone use in neonates problematic?
- interacts with calcium-containing medications to form crystals (can precipitate in the lungs and kidneys; has led to fatalities) - can lead to biliary sludging (with resultant hyperbilirubinemia)
150
How is ceftriaxone dosed for MSSA infections?
2-4 grams per day (particularly invasive infections) -less activity against this organism means higher doses are recommended
151
What are 3rd generation cephalosporins good for?
- lower respiratory tract infections - pyelonephritis - nosocomial infections and febrile neutropenia (ceftazidime) - Lyme disease (ceftriaxone) - meningitis - gonorrhea - skin and skin structure infections
152
How is ceftriaxone dosed for most infections?
Once daily -except meningitis (2g IV q12h); also use vancomycin and ampicillin (if indicated)
153
What is the only 4th generation cephalosporin?
Cefepime
154
What is the broadest spectrum cephalosporin?
Cefepime -has activity against gram positive and gram negative organisms (including Pseudomonas)
155
What organisms does cefepime have GOOD activity against?
- MSSA - streptococci - Pseudomonas - enteric GNRs
156
What organisms does cefepime have MODERATE activity against?
-Acinetobacter
157
What organisms does cefepime have POOR activity against?
- enterococci - anaerobes - MRSA
158
How do the adverse effects of cefepime compare to other beta-lactams?
Generally similar -cefepime may be associated with more neurotoxicity than other agents
159
How should cefepime be used empirically?
It is a broad spectrum agent - good empiric choice for many nosocomial infections - overkill for most community-acquired infections - de-escalate therapy whenever possible when treating empirically with cefepime
160
Why is cefepime a better choice than ceftazidime for monotherapy of febrile neutropenia?
- better gram positive activity - may induce less resistance in GNRs than 3rd generation cephalosporins - still not a good drug to overuse
161
Why did cefepime previously have a bad reputation?
A meta-analysis showed increased mortality with its use compared with other drugs -more thorough FDA analysis exonerated cefepime
162
How does neurotoxicity occur with cefepime?
Can occur at any dose (dose adjustment with renal dysfunction is important) -may manifest as nonconvulsive status epilepticus
163
What is cefepime good for?
- febrile neutropenia - nosocomial pneumonia - postneurosurgical meningitis - other nosocomial infections
164
What types of infections is cefepime primarily used for?
Nosocomial infections -indicated for UTIs and lower respiratory tract infections (but is overkill for most community acquired sources of these infections)
165
How is ceftriaxone eliminated?
Dual modes of elimination: - renal - biliary excretion
166
What is the only anti-MRSA cephalosporin currently on the market?
Ceftaroline
167
What anti-MRSA cephalosporin was removed from the market?
Ceftobiprole
168
What organism (besides MRSA) does ceftaroline have activity against that no other cephalosporin has?
Modest activity against E. faecalis (not E. faecium)
169
How does the gram negative potency of ceftaroline compare to previous cephalosporins?
Similar to that of ceftriaxone -lost some of the gram negative potency of cefepime
170
Which characteristic of ceftaroline is responsible for its anti-MRSA activity?
- can bind to penicillin-binding protein 2a (a type that is expressed by MRSA) - its structure has been engineered to bind to the penicillin-binding protein 2a of MRSA that has low affinity for other beta-lactams
171
What organisms does ceftaroline have GOOD activity against?
- MSSA - MRSA - streptococci - enteric GNRs
172
What organisms does ceftaroline have MODERATE activity against?
-E. faecalis
173
What organisms does ceftaroline have POOR activity against?
- P. aeruginosa - E. faecium - Acinetobacter - anaerobes
174
How do the adverse effects of ceftaroline compare to other beta-lactams?
Similar
175
What are the initial indications for ceftaroline?
"Low hanging fruit" (which is typical for new antimicrobials coming to the market: - skin and skin structure infections - community acquired pneumonia Many great agents are already available for these infections already -challenge will be to determine its role in hospital acquired pneumonia and other severe diseases caused by drug resistant pathogens
176
How did ceftaroline do against ceftriaxone in community acquired pneumonia?
Outperformed ceftriaxone in two of three studies
177
What infections has ceftaroline been described to successfully treat in case series and retrospective studies?
- bloodstream infections - endocarditis - meningitis - osteomyelitis - hospital-acquired pneumonia
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What is ceftaroline good for?
Approved (in the US) for treatment of: - complicated skin and soft tissue infections - community acquired pneumonia Less rigorous data for other uses
179
In which three key organisms is carbapenem resistance mostly seen?
- Klebsiella pneumoniae - P. aeruginosa - A. baumannii
180
What is avibactam?
New type of beta-lactamase inhibitor MOA is different from other beta-lactamase inhibitors -does not resemble a beta-lactam, but also binds beta-lactamases and renders them inert
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What beta-lactamases does avibactam work against?
- K. pneumoniae | - P. aeruginosa
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What cephalosporin is avibactam combined with?
Ceftazidime
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What is ceftolozane?
3rd generation cephalosporin -evades many resistance mechanisms of P. aeruginosa
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What cephalosporin is tazobactam combined with?
Ceftolozane Tazobactam is a beta-lactamase inhibitor that structurally resembles beta-lactams and binds to many beta-lactamases (rendering them unable to inactivate the co-administered beta-lactam)
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What organisms do cephalosporin/beta-lactamase inhibitor combinations have GOOD activity against?
- Pseudomonas | - enteric GNRs (ceftazidime/avibactam > ceftolozane/tazobactam)
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What organisms do cephalosporin/beta-lactamase inhibitor combinations have MODERATE activity against?
-some streptococci (ceftolozane/tazobactam)
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What organisms do cephalosporin/beta-lactamase inhibitor combinations have POOR activity against?
- most anaerobes - MRSA - MSSA - Acinetobacter
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What resistant organism do cephalosporin/beta-lactamase inhibitor combinations NOT have good activity against?
Acinetobacter
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What resistant organism DO cephalosporin/beta-lactamase inhibitor combinations have good activity against?
Most multidrug-resistant Pseudomonas -possible to see isolates of Pseudomonas that are resistant to one of these drugs and susceptible to the other
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Which cephalosporin/beta-lactamase inhibitor combination is active against carbapenem-resistant Klebsiella and other enteric GNRs?
Ceftazidime/avibactam
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How does ceftolozane evade Pseudomonas resistance?
It is minimally affected by many Pseudomonas resistance mechanisms (including its beta-lactamase) -tazobactam adds little for this organism
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How does ceftazidime evade Pseudomonas resistance?
Relies on avibactam to inactivate Pseudomonas beta-lactamases
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Are cephalosporin/beta-lactamase inhibitor combinations effective against gut anaerobes?
No (due to substantial resistance) -add metronidazole if anaerobic involvement suspected This is unlike penicillin/beta-lactamase inhibitor combination
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What are BOTH cephalosporin/beta-lactamase inhibitor combinations good for?
- multidrug-resistant Pseudomonas infections - mixed aerobic/anaerobic infections - intra-abdominal infections - infections caused by ESBL-producing organisms
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What is ceftazidime/avibactam good for?
-carbapenem-resistant Enterobacteriaceae infections
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Name the carbapenems.
- Imipenem/cilastatin - Meropenem - Ertapenem - doripenem
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What are carbapenems?
Broadest spectrum antibacterial drugs -possess a beta-lactam ring and share the same MOA of beta-lactams (but are structurally unique and different from penicillins/cephalosporins) Ertapenem has important differences in its spectrum (it is the EXCEPTION)
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What organisms do carbapenems have GOOD activity against?
- MSSA - streptococci - anaerobes - enteric GNRs - Pseudomonas (not ertapenem) - Acinetobacter (not ertapenem) - ESBL-producing GNRs
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What organisms do carbapenems have MODERATE activity against?
-enterococci (not ertapenem)
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What organisms do carbapenems have POOR activity against?
- MRSA | - penicillin-resistant streptococci
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How do the adverse effects of carbapenems compare to other beta-lactams?
Similar Imipenem has a higher propensity to induce seizures - calculate appropriate doses for patients with renal dysfunction - avoid use in meningitis (can cross the blood-brain barrier more easily)
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Why is cilastatin always coadministered with imipenem?
Imipenem is metabolized in the kidney to a nephrotoxic product -cilastatin blocks the renal dehydropeptidase that catalysts this reaction (prevents this metabolism from occurring
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What types of infections are carbapenems good for?
Are very broad-spectrum agents - should not be used empirically for most community-acquired infections - good choices for many types of nosocomial infections (particularly if patients received other classes of antibiotics during their hospital stay)
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What is a disadvantage of ertapenem?
Poor choice for nosocomial infections -particularly nosocomial pneumonia (where Pseudomonas and Acinetobacter are important pathogens)
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What is an advantage of ertapenem?
Administered only once a day -may be a better choice for home-infusion therapy for susceptible infections
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Describe carbapenem cross-allergenicity with penicillin.
- one study showed incidence of an allergic reaction in patients with a history of penicillin allergy to be as high as 47% with a proven penicillin allergy - recent better performed studies in patients with anaphylaxis to penicillin show this number to be closer to 1% - patients with a history of allergy to any drug are more likely to react to another one even if they are not related
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Do carbapenemases exist?
Yes; render carbapenems inert -most common in the northeast US; very common in other parts of the world
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What are ALL carbapenems good for?
- mixed aerobic/anaerobic infections - infections caused by ESBL producing organisms - intra-abdominal infections
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What are carbapenems EXCEPT ertapenem good for?
- nosocomial pneumonia - febrile neutropenia - other nosocomial infections
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What is the only monobactam?
Aztreonam
211
Describe the structure of aztreonam.
Contains only the four-membered ring of the basic beta-lactam structure
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Aztreonam is safe to administer to patients with allergies to other beta lactamases, except?
Specific allergy to ceftazidime (shares an identical side chain with aztreonam) -ceftolozane also shares this side chain
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What beta-lactam does aztreonam share the same spectrum of activity with?
Ceftazidime
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What organisms does aztreonam have GOOD activity against?
- Pseudomonas | - most GNRs
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What organisms does aztreonam have MODERATE activity against?
-Acinetobacter
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What organisms does aztreonam have POOR activity against?
- gram positive organisms | - anaerobes
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How do the adverse effects of aztreonam compare to other beta-lactams?
Similar -low incidence of hypersensitivity
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What class of drugs is aztreonam often confused with?
Aminoglycosides - is chemically unrelated and does not share their toxicities - shares MOA and pharmacodynamic profile with other beta-lactams
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When can aztreonam be administered via inhalation?
To patients with cystic fibrosis to prevent exacerbations of infection
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Should aztreonam be combined with other beta-lactams?
Not warranted against the same organism -add a non-beta-lactam to empiric regimen for serious nosocomial infections
221
What is aztreonam good for?
Gram negative infections -including Pseudomonas (particularly in patients with a history of beta-lactam allergy)

Antibiotics (63 decks)

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