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Antibiotics Flashcards

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
Q

When is Linezolid indicated?

A

Vanc resistance, reduced susceptibility

Vanc AEz

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26
Q

Is Linezolid affective against gram –ves?

A

No

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27
Q

Does Linezolid have activity against mycobacteria/nocardia?

A

Yes

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28
Q

What is the spectrum of activity for Linezolid?

A

Staph, Enterococci and Streptococci
MRSA, VRE, VISA infections
MDRTB in combination
Nocardia (Gram +ve rod)

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29
Q

What are the AE of Linezolid?

A

GIT
Headache
Bone marrow suppression ->Thrombocytopenia
Peripheral, optic neuropathy, >28 d of therapy (TB therapy)
Lactic acidosis
Serotonin syndrome,

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30
Q

MOA of Daptomycin (lipopeptide)?

A

Binds to cell membrane -> inhibitiio of synthesis of DNA, RNA and protein.
Bactericidal against MRSA and VRE

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31
Q

When is Daptomycin indicated?

A

VRE if other options not feasible

hVisa/VISA if daptomycin susceptible

32
Q

Is Daptomycin useful in pneumonia?

A

No, inactivated by surfactant

33
Q

AE of Daptomycin?

34
Q

MOA of Tigecycline (Glycycline, related to tetracyclines)?

A

Binds to 30S ribosomal unit blocking tRNA function -> protein synthesis inhibitor
Bacteriostatic

35
Q

What is Tigecycline active against?

A

Staph, MRSA, MSSA
Strep
Enterococci
Including MRSA, VISA and VRE

36
Q

What is the resistance of Tigecycline due to?

A

Efflux pumps

37
Q

Is Tigecylcine effective against PsA and Burkholderia?

A

No, resistant

38
Q

AE of Tigecycline?

A

GIT, dose depenendent

CI in pregnancy and children

39
Q

How do you treat heterogenous Vanc intermediate Staph aureus infection?

A

Linezolid (Oxazolidone)

40
Q

In which populations are Vanc Intermediate Staph aureus infections seen in?

A

Dialysis pts- dialysis graft fistulas

Infected foreign bodies that are non-removable e.g. LVAD

41
Q

What are the signs of VISA infection?

A

Ongoing positive cultures despite Tx
Usually MRSA
Retained foreign bodies e.g. dialysis graft fistulas
Persistent infection but usually not severe infection

42
Q

What is the MOA of VRSA?

A

Van genes that encode vancomycin resistance

43
Q

MOA of VRE?

A

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
Q

How do you Tx VRE?

A 
Linezolid
Tigecycline
Daptomycin 
What is the MOA of Penicillin resistant Strep pneumonia? How do you Tx?
Altered PBPs
Vancomycin
45
Q

How do you Tx ESBL?

46
Q

MOA of Ceftaroline?

A

Betalactam -> bacteriocidal
Activity against MRSA, hVISA, VISA
High affinity for PBP2a

47
Q

When is Ceftaroline indicated?

A

Pneumonia

Soft/skin tissue infections

48
Q

What is the MOA of colisitin?

A

Binds liposachharides and phospholipids in outer cell membrane -> disruption of the outer cell membrane, leakage and cell death (like detergent).

49
Q

What organism is Colistin effective against?

A 
Gram -ve bacilli:
Pseudomonas
Acinetobacter
E. coli
Some Enterobacter 
Klebsiella
Salmonella
Stenotrophomonas
50
Q

Which organism does Colistin not work against?

A 
Burkholderia cepacia (gram -ve)
Serratia
Proteus
Providencia
Morganella
51
Q

What are the main adverse effects of colistin?

A

Nephrotoxicty

Neurotoxicity

52
Q

Is Ertapenem effective against pseudomonas?

53
Q

Is Doripenem effective against pseudomonas?

A

Yes, broad spectrum of activity

54
Q 
MOA of resistance in S. aureus:
MSSA
MRSA
VISA
VRSA
A

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
Q

Which abx are effective against carbapenemase producing enterbacteriacae?

A

Colistin 100%

Tigecycline 78%

56
Q

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

A

Ampicillin will have cross reactivity with:
Cephalexin
Cefaclor

Amoxicillin will have cross reactivity with:
Cefadroxil
Cefprozil
Cefatrizine

57
Q

HIV. When do you start PJP prophylaxis to prevent OI?

A

CD4 200 but

58
Q

HIV. When do you start MAC prophylaxis?

59
Q

What is the most common presentation of scabies? Tx?

A

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
Q

What confers the highest risk to invasive pneumococcal infection?

A

Asplenism- RR 50-500
Alcohol abuse RR 11.4
Age > 65y - RR 2-10

61
Q

In Tb infection, culture of which specimen is the most sensitive for Dx?

A

Pleural Bx 40-80%
BAL 20-50%
Sputum 20-50% (less if no infiltrate)
Pleural fluid 20-30%

62
Q

Pleural effusion. Dx of exudate?

A

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
Q

Pt has hx of HF and bilateral pleural effusion. Tx with diuresis and effusion persist. Next step?

A

Thoracentesis to Ix transudate vs. exudate

64
Q

Amoebic liver abscess. Ix to confirm Dx?

A

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
Q

Amoebic liver abscess. Cause, presentation, Tx?

A

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
Q

Which is not associated with an increased risk of mortality in S. aureus bacteraemia?

A

Central line associated S. aureus in comparison with endocarditis, Chronic liver disease, ongoing +ve BC after 3 d and Tx with vancomycin

67
Q

MOA Teicoplanin?

A

Semi synthetic glycopeptide, inhibit bacterial cell wall synthesis.
Effective aganst gram +ve bacteria, MRSA and enterococcus faecalis.

Ineffective against VRE expressing vanA gene.

68
Q

HIV- refer to evernote

69
Q

Antifungal and antivirals. Refer to USMLE p140 onwards.

70
Q

What method is used to determine clonal spread of VRE in the hospital?

A

Pulse field gel electrophoresis.
Banding patterns produced by each organism is matched.

Other methods include pcr testing, multilocus enzyme elctrophoresis and ribotyping.

71
Q

Antibiotics with anaerobic cover?

A

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
Q

Chloramphenicol. MOA. Indications. AE

A

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
Q 
What is the mechanism of resistance to penicillin in:
pneumococcal infections (strep pneumoniae)
gram +ve
A 
pneumococcal infections (strep pneumoniae)
- decreased affinity of penicillin binding sites.

gram +ve
- betalactamase production

74
Q

Which antibiotics are bacteriostatic?

A

Chloramphenicol
Macrolides
Sulphonamides and Trimethroprim
Tetracyclines - doxy, mino

Linezolid have both actions

75
Q

Splenectomy. What infections are these pts at risk of?

Prophylaxis?

A

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
Q

Staph aureus secreting panton valentine leucocidin (PVL) toxin most likely causes?

A

Pyogenic skin infections

MK (28 decks)

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