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Antibiotics Flashcards

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1
Q

Which Abx interfere cell wall synthesis?

A

Betalactams (penicillin, cephalosporins, carbapenems)

Glycopeptides (Van, Teicoplanin)

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2
Q

Which Abx interfere with folic acid metabolism?

A

Trmethoprim and Sulfonamides

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3
Q

Which abx inhibit protein 30S synthesis?

A

Tetracyclines
Tigecyclines
Aminoglycasides

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4
Q

Which abx interfere with protein 50S synthesis?

A

Macroldies
Lincosamides
Stretogrammin

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5
Q

Which Abx interfere with DNA dependent polymerase?

A

Rifampacin

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6
Q

Which abx interfere with DNA replication (DNA gyrase)?

A

Quinalones

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7
Q

What is the MOA of betalactams?

A

block transpeptidase activity of PBPs in bacterial cell wall causing cell death by osmosis or autolysis

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8
Q

What are the betalactams?

A

Penicillins
Cephalosporins
Carbapenems (mero, imi, erta)
Monobactams

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9
Q

Which abx have effective cover against ESBLs and ESCAPMs?

Carbapenems

A

Carbapenems (mero, imi, erta)

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10
Q

Does Ertapenem have activity against Pseudomonas and Acinetobacter?

A

No

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11
Q

What is the MOA of aminoglycosides?

A

Combine 30S and 50S ribosomal subnunits to inhibit protein synthesis
Bacteriocidal

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12
Q

Do aminoglycosides have activity against anaerobes?

A

No

Poor tissue and intracellular activity

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13
Q

What are the indications for amioglycsides?

A

Gram +ve septicaemia (with betalactam)
Febrile neutropenia
Combined with penicillin or Vanc in streptococcal ot enterococcal endocarditis

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14
Q

What are the suggested trough levels for gent/tobra and amikacin?

A

Gent/Tobra

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15
Q

What are the major toxicities with aminoglycosides?

A

Nephorox
Ototox
Neurosmuscular blockade
Rash drug fever

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16
Q

List the macrolides

A

Erythromicin (many drug intercations)
Roxithromycin
Clarithromycin
Azithromicin

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17
Q

What is the MOA of macrolides?

A

Bind to 50S ribosomal subunit inhibiting protein synthesis
Bacteriostatic
Good tissue and intracellular activity

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18
Q

What is the MOA of clindamycin (lincosamide)?

A

Related to macrolides.

Binds to 50S ribosomal subunit inhibiting protein synthesis

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19
Q

When is Clindamycin indicated?

A

Gram +ves and anaerobes
Some parasites
Non-multiresistance community MRSA (oxacillin resistant)

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20
Q

Does Clindamycin have a high association with C. diff?

A

Yes

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21
Q

List the quinolones.

A

Norflox
Ciproflox
Ofloxaxin
Moxifloxacin

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22
Q

What is the MOA of quinolones?

A

Block bacterial DNA gyrase
Bacteriocidal
Good tissue and intracellular activity
Good gram –ve cover

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23
Q

What are the AE of quinolones?

A

GIT
CNS
Rare- rash, cytopenia, arthralgias/Achilles tendonitis
QTc interval prolongation

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24
Q

What is the MOA of Linezolid (Oxazolidone)?

A

Interacts with 50S ribosome to inhibit protein synthesis inititation
Oral = 100% bioavailability
Good CNS vitreous activity

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25
When is Linezolid indicated?
Vanc resistance, reduced susceptibility | Vanc AEz
26
Is Linezolid affective against gram –ves?
No
27
Does Linezolid have activity against mycobacteria/nocardia?
Yes
28
What is the spectrum of activity for Linezolid?
Staph, Enterococci and Streptococci MRSA, VRE, VISA infections MDRTB in combination Nocardia (Gram +ve rod)
29
What are the AE of Linezolid?
GIT Headache Bone marrow suppression ->Thrombocytopenia Peripheral, optic neuropathy, >28 d of therapy (TB therapy) Lactic acidosis Serotonin syndrome,
30
MOA of Daptomycin (lipopeptide)?
Binds to cell membrane -> inhibitiio of synthesis of DNA, RNA and protein. Bactericidal against MRSA and VRE
31
When is Daptomycin indicated?
VRE if other options not feasible | hVisa/VISA if daptomycin susceptible
32
Is Daptomycin useful in pneumonia?
No, inactivated by surfactant
33
AE of Daptomycin?
Myositis
34
MOA of Tigecycline (Glycycline, related to tetracyclines)?
Binds to 30S ribosomal unit blocking tRNA function -> protein synthesis inhibitor Bacteriostatic
35
What is Tigecycline active against?
Staph, MRSA, MSSA Strep Enterococci Including MRSA, VISA and VRE
36
What is the resistance of Tigecycline due to?
Efflux pumps
37
Is Tigecylcine effective against PsA and Burkholderia?
No, resistant
38
AE of Tigecycline?
GIT, dose depenendent | CI in pregnancy and children
39
How do you treat heterogenous Vanc intermediate Staph aureus infection?
Linezolid (Oxazolidone)
40
In which populations are Vanc Intermediate Staph aureus infections seen in?
Dialysis pts- dialysis graft fistulas | Infected foreign bodies that are non-removable e.g. LVAD
41
What are the signs of VISA infection?
Ongoing positive cultures despite Tx Usually MRSA Retained foreign bodies e.g. dialysis graft fistulas Persistent infection but usually not severe infection
42
What is the MOA of VRSA?
Van genes that encode vancomycin resistance
43
MOA of VRE?
Change D-ala D-ala to D –ala D –lac -> Vanc unable to bind Contains van genes A , B and others E. faecalis and E. faecium
44
How do you Tx VRE?
``` Linezolid Tigecycline Daptomycin What is the MOA of Penicillin resistant Strep pneumonia? How do you Tx? Altered PBPs Vancomycin ```
45
How do you Tx ESBL?
Meropenem
46
MOA of Ceftaroline?
Betalactam -> bacteriocidal Activity against MRSA, hVISA, VISA High affinity for PBP2a
47
When is Ceftaroline indicated?
Pneumonia | Soft/skin tissue infections
48
What is the MOA of colisitin?
Binds liposachharides and phospholipids in outer cell membrane -> disruption of the outer cell membrane, leakage and cell death (like detergent).
49
What organism is Colistin effective against?
``` Gram -ve bacilli: Pseudomonas Acinetobacter E. coli Some Enterobacter Klebsiella Salmonella Stenotrophomonas ```
50
Which organism does Colistin not work against?
``` Burkholderia cepacia (gram -ve) Serratia Proteus Providencia Morganella ```
51
What are the main adverse effects of colistin?
Nephrotoxicty | Neurotoxicity
52
Is Ertapenem effective against pseudomonas?
no
53
Is Doripenem effective against pseudomonas?
Yes, broad spectrum of activity
54
``` MOA of resistance in S. aureus: MSSA MRSA VISA VRSA ```
MSSA (resistant to penicillin) - b-lactamase-stable penicillins or b-lactamse inhibitor MRSA (resistant to methicillin, fluclox, oxacillin) - mecA gene encodes altered PBP (PBP2a) with lower affinity for binding B-lactam VISA - Increased bacteria wall thickness with reduced access of antibiotic to site of activity VRSA - VanA gene results in synthesis of modified peptidoglycan precursors with markedly reduced affinity for glycopeptides
55
Which abx are effective against carbapenemase producing enterbacteriacae?
Colistin 100% | Tigecycline 78%
56
The following penicillins will have cross reactivity to cephalosporins with identical side chains. Which antibiotics will be less likely tolerated in pts with allergies to the following: Ampicillin Amoxicillin
Ampicillin will have cross reactivity with: Cephalexin Cefaclor Amoxicillin will have cross reactivity with: Cefadroxil Cefprozil Cefatrizine
57
HIV. When do you start PJP prophylaxis to prevent OI?
CD4 200 but
58
HIV. When do you start MAC prophylaxis?
CD4
59
What is the most common presentation of scabies? Tx?
Pruritis - develops within 24 h - mainly sexually acquired in adults Tx - Permethrin cream, washed off after 8-14 h OR - Ivermectin 200 ug/kg PO and repeated in 2 weeks
60
What confers the highest risk to invasive pneumococcal infection?
Asplenism- RR 50-500 Alcohol abuse RR 11.4 Age > 65y - RR 2-10
61
In Tb infection, culture of which specimen is the most sensitive for Dx?
Pleural Bx 40-80% BAL 20-50% Sputum 20-50% (less if no infiltrate) Pleural fluid 20-30%
62
Pleural effusion. Dx of exudate?
Pleural fluid protein to serum protein >0.5 OR ratio of pleural fluid LDH to serum LDH > 0.6 OR pleural fluid LDH > 2/3 ULN If any above present test for cell diff, glucose, cytologic analysis and cultures. If effusion is lymphocytic test for Tb. If no cause established then rule out PE.
63
Pt has hx of HF and bilateral pleural effusion. Tx with diuresis and effusion persist. Next step?
Thoracentesis to Ix transudate vs. exudate
64
Amoebic liver abscess. Ix to confirm Dx?
Serology for Entamoeba histolytica is the most sensitive, 92-97% +ve at presentation Stool microscopy - fresh smear of 3 specimens detect 85-95% Aspirate of liver lesion (not necessary)- macroscopic appearance is anchovy paste, parasite only seen in
65
Amoebic liver abscess. Cause, presentation, Tx?
Infection with trophozite amoebiasis. Endemic to tropical areas. Presentation: Fever Night sweats RUQ pain Cyst migrate to liver after invasion of the colonic wall. Interval between exposure and symptom onset is 2-4 months. Dx: Liver US Serology most sensitive Stool next step Tx: Metronidazole Risk of rupture with no Tx Tinidazole another option
66
Which is not associated with an increased risk of mortality in S. aureus bacteraemia?
Central line associated S. aureus in comparison with endocarditis, Chronic liver disease, ongoing +ve BC after 3 d and Tx with vancomycin
67
MOA Teicoplanin?
Semi synthetic glycopeptide, inhibit bacterial cell wall synthesis. Effective aganst gram +ve bacteria, MRSA and enterococcus faecalis. Ineffective against VRE expressing vanA gene.
68
HIV- refer to evernote
evernote
69
Antifungal and antivirals. Refer to USMLE p140 onwards.
USMLE
70
What method is used to determine clonal spread of VRE in the hospital?
Pulse field gel electrophoresis. Banding patterns produced by each organism is matched. Other methods include pcr testing, multilocus enzyme elctrophoresis and ribotyping.
71
Antibiotics with anaerobic cover?
Metronidazole - lack activity against propionibacterium acnes, actinomyces and lactobacillus. Classically better for infections BELOW the diaphram. Do not use as monotherapy above diaphram, combine with other. Clindamycin Combined PCN/betalactamse e.g. Augmentin, Timentin Carbapenems - imi, mero, erta, dori 2nd generation cephalosporins - Cefoxitin, Cefotetan - beware of increasing resistance Moxiflox - increasing resistence among bacteriodes (up to 40%) Tigecycline Note: For intraabdominal infections, avoid Clindamycin, Moxifloxacin, and Cefotetan/Cefoxitin due to increasing resistance amongst Bacteroides
72
Chloramphenicol. MOA. Indications. AE
MOA: Reversible binds to 50S sunbunit inhibitign protien synthesis. ``` Indication: Severe typhoid, paratyphoid Meningitis Eye infections Bacteriodes (anaerobic gram -ve bacilli) H. influenza (gram -ve bacilli) N. meningitis (gram -ve cocci) Salmonella (gram -ve bacilli) Rickettsia VRE (gram +ve cocci) ``` ``` AE: N/V headache reversible bone marrow suppression C. diff infection ``` Grey baby syndrome
73
``` What is the mechanism of resistance to penicillin in: pneumococcal infections (strep pneumoniae) gram +ve ```
``` pneumococcal infections (strep pneumoniae) - decreased affinity of penicillin binding sites. ``` gram +ve - betalactamase production
74
Which antibiotics are bacteriostatic?
Chloramphenicol Macrolides Sulphonamides and Trimethroprim Tetracyclines - doxy, mino Linezolid have both actions
75
Splenectomy. What infections are these pts at risk of? | Prophylaxis?
Encapsulated bacteria with polysachharide antigens: Strep pneum Neisseria H. influenza serogroup B (Hib) ``` Vaccinations: 3 weeks prior to splenectomy - pneumococcal vaccine, - H. influenza and - PPV -23 quadrivalent meningococcal if > 2yo ```
76
Staph aureus secreting panton valentine leucocidin (PVL) toxin most likely causes?
Pyogenic skin infections

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