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Board Review 2020 > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

Define MIC

A

the lowest concentration of an antimicrobial (like an antifungal, antibiotic or bacteriostatic) drug that will inhibit the visible growth of a microorganism after overnight incubation

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2
Q

Define MBC

A

is the lowest concentration of an antibacterial agent required to kill a particular bacterium as the lowest concentration of antimicrobial that will prevent the growth of an organism after subculture on to antibiotic-free media

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3
Q

What determines if an antimicrobial drug is classified as bactericidal or bacteriostatic (there is a specific definition relating to the MIC)?

A

Bactericidal antibiotics kill bacteria; bacteriostatic antibiotics inhibit their growth or reproduction- which means that the host’s immune system does the killing. Cidial- MBC 4 times or less the MIC of that drugStatic if the MBC is more than 4 times MIC of that drugSpecific to the bacteria and the drug

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4
Q

Discuss the concepts of synergistic antimicrobial combinations, antagonistic antimicrobial combinations, indifferent antimicrobial combinations

A

Additive: the combined effect is equal to the sum of the independent effectsSynergistic: the combined effect is greater than the sum of the independent effects; example beta lacatam/aminoglycoside; amoxi/clav; tms;Indifferent if the combined effect is similar to the greatest effect produced by either drug alone

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5
Q

Describe how to interpret and use susceptibility testing

A

Susceptibiltiy testing: in general, the peak serum concentration of a drug should be 4-10 times greater than the MIC in order for a pathogen to be susceptible to a drug. Pathogens with intermediate sensitivity may respond to treatment with maximal doses of an abx

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6
Q

Cell Wall Inhibitiors

A

Penicillins, cephalosporins, vancomycin, bactiracin, carbapenem, imipenem

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7
Q

DNA Gyrase inhibitors

A

quinolones, fluoroquinolones

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8
Q

Folate synthesis inhibitors

A

sulfonamides, trimethoprim

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9
Q

RNA polymerase inhibitor

A

rifampin

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10
Q

Cell Membrane inhibitors

A

amophotericin, polymixin

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11
Q

Protein Synthesis

A

aminoglycosides, chloramphenociol, clindamycin, macrolides, mupirocin, tetracyclines, stretogramins

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12
Q

What is a CLSI breakpoint

A

Clinical and laboratory standards institute specific for each of the following: animal species, target tissue, target organism, antibmicrobal drug, route administration

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13
Q

Broth dilution test

A

Tubes that contain a nutrient broth are inoculated with equal numbers of bacteria and serially diluted concentrations of an antibiotic. After incubation the MIC is identified as the lowest antibiotic concentration that prevents visible growth of bacteria

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14
Q

Disk diffusion- Kirby Bauer

A

each disk used is impregnated with a different antibiotic. The discs are palced on augar plates seeded with the test organism. During the incubation period the antibiotic diffuses from the disk and inhibits bacterial growth. The zone inhibitied by each antibiotic is measured. The zone diameter for each is comparted with standard values for that antibiotic

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15
Q

E-Test Strip

A

uses a diffusion method to determine the MIC. The device is a plastic strip that is impregnated with a gradient of antibiotic concentrations. After the strip is placed on an agar culutre of the organism the culture is incubated. A tear shaped zone of inhibition is formed. The scale displaced on the strip is the MIC- able to get MBC/MIC

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16
Q

Episolon test

A

Card with wells, color change of the wells- MBC/MIC

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17
Q

Natural resistance to enterococcus

A

Cephalsporins

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18
Q

Promote resistance by pressure to express Mech A for Staph

A

Cephalsporins and fluoroquinolones

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19
Q

Beta Lacatams

A

Bind to a group of bacterial enxymes BPBs which are anchored on the cytoplasmic membrane and extend into the periplasmic space. They form a covalent bond with PBPs and thereby inhibit the catalytic activity of these enzymes. All are bacterialcidial

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20
Q

Penicillin ADME

A

Acid stable- PO; Acid liable IV; Widely distributed exceot to CNS; readily penitrates CSF when meninges are inflammed. Active renal tubular secretion; Ampicillin is primarly excreted in bile

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21
Q

Penicillin Antibacterial Activity

A

Grame +, anaerobic

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22
Q

Cephalosporins ADME

A

Oral or parental (cefuroxime is both); mostly renal tubular excretion; ceftriaxone is bile- longer half life

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23
Q

Cephalosporins Antibacterial Activity

A

1st: Gram + Cocci (limited G- baccili;) 2:G+ better G- bacilli; 3rd: better G- bacilli, anaerobes and psuedomonas

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24
Q

Beta lactase inhibitors ADME

A

Binds to active site of pencillinase rendering the enzyme inactive; Time dependent; side effect hemolytic anemia

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25
Q

Carbapenams ADME

A

Admin- IV, Eliminated via Renal tubular secretion

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26
Q

Carbamenams Antibacterial Activity

A

G+, G-, anaerobic and aerobic

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27
Q

Monobactams ADME

A

Administered IV, Extensively metabolized, renal excretion

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28
Q

Monobactams Antibacterial Activity

A

Aerobic G- Bacilli

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29
Q

Monobactams advantages

A

Can be used with B-lactam allergies; used with MDR; can cause thrombophelbitis in people

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30
Q

Polymyxins MOA

A

Cationic detergents that interact and interfere with phospholipid of the bacterial cell membrane resulting in increase permeability: Bacterialcidial

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31
Q

Polymyxins ADME

A

Weak bases and are not orally bioavailable. Renal elimination primary site (toxicity as well); Used primarily topically

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32
Q

Polymyxins Antibacterial Activity

A

Most G- exceptions include proteus and serratia

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33
Q

Polymyxins Complications

A

Glomerular and tubular epithealial damage, respiratory paralysis (not reported in cats). CNS dysfunction, fever and anorexia

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34
Q

Glycopeptides/Vancomycin MOA

A

Cell wall inhibitor. Used to targe MRSA, Enterococcus (designed for)

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35
Q

Glycopeptides/Vancomycin ADME

A

Only IV; Not absorbed from the gut- therefore used orally for C-diff

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36
Q

Glycopeptides/Vancomycin Antibacterial Activity: Cidal/static; Time vs Conc?

A

Gram +; Bactericidal; Time dependent

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37
Q

Glycopeptides/Vancomycin advantages

A

Can be used with allergies to beta lactam

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38
Q

Glycopeptides/Vancomycin complications

A

Bad pheblitis and horrible sloughing of the SQ

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39
Q

Bacitracin MOA

A

Inhibits cell wall peptidoglycan synthesis by blocking the regeneration of bactopernol lipid carrier molecule

40
Q

Bacitracin Antibacterial Activity

A

Gram + Cocci

41
Q

Bacitracin Contraindications

A

Nephrotoxic so don’t use systemically

42
Q

Fosamycin MOA

A

Cell wall inhibitor

43
Q

Fosamycin ADME

A

Phosphoric acid; Low pH useful for bacteria express MDR

44
Q

Fosamycin Antibacterial Activity: Cidal/static; Time vs concentration?

A

E-Coli and Gram +/-; Bacterialcidal; Concentration dependent

45
Q

Clindamycin/Lincosamides MOA

A

50s Subunit at a site distinct from macrolides and chloramphenicol; peptidyl transferase is inhibitied

46
Q

Clindamycin/Lincosamides ADME

A

Highly protein bound, Food impairs absorption; good for skin and bones; eliminated primarily for biliary excretion; Crosses BBB

47
Q

Clindamycin/Lincosamides Antibacterial Activity

A

G+, aerobic cocci, anaerobic and cell wall deficient organismis; mycoplasma; Static; Time dependent

48
Q

Clindamycin additional notes

A

Accumulates in white blood cells up to forty fold or more- increases the probability of reaching bactericidal concentrations at some sites of infection. Penetrates pus in pyothorax; In people may lead to C-Diff

49
Q

Pleuromutilins MOA

A

50s Subunit- Static; Occasionall used in SA

50
Q

Macrolides/ Azythromycin MOA

A

50s subunit and impair the translocation step of protein synthesis

51
Q

Macrolides/ Azythromycin ADME

A

Lipid soluble and accumulates in phagocytic WBCs; Urine secretion is not significant and conentration is often less than in plasma. Pentrates the lung very well

52
Q

Macrolides/ Azythromycin Antibacterial Activity

A

G+/-; bordetella; Static in vitro- scidial against susceptible organisms; time and concentration dependent- exhibits post antibiotic effect

53
Q

Macrolides/ Azythromycin complications

A

GI side effects

54
Q

Streptogramins/ quinupristin MOA

A

50s subunit

55
Q

Streptogramins/ quinupristin Antibiotic Activity

A

Vancomycin resitant enterococcus; Static

56
Q

Ketolides

A

Are semisynthetic modificaions of erythromycin designed to minimize barriers to pentration in gram negative organisms

57
Q

Aminoglycosides/Amikacin/Gentomycin MOA

A

30s ribosome; enters through porins; efficacy is dependent on active transprt- which is reduced to absent in anaerobic environments

58
Q

Aminoglycosides/Amikacin/Gentomycin ADME

A

Synovia, pleural and peritonel fluid better in bronchial secretions; Actively accumulated in renal tubular cells; Reduce efficacy in acidic environments. Eliminated through glomerular filtration; Not absorbed through the gut- good for shunt dogs

59
Q

Aminoglycosides/Amikacin/Gentomycin Antibacterial activity

A

Aerobic G-; Static; concentration

60
Q

Aminoglycosides/Amikacin/Gentomycin side effects

A

Dose reduce for obesity; Nephrotoxicity- tubular and glomerular- which is reversible

61
Q

Tetracyclines MOA

A

Bind to the 16s portion of the 30s ribosomal subunit preventing access to the amino-acryl tRNA to the acceptor site on the mRNA ribosome complex. Enters through porins or active transport pumps

62
Q

Tetracyclines ADME

A

Doxy- 100% bioavailable, lipid soluble; decreased with divalent and trivalent cations such as milk or antacids; widely absorbed through body tissues. Biliary and renal excretion

63
Q

Tetracyclines Antibacterial Activity

A

Gram +/-; anaerobic, rickettsial, and cell wall deficient; Static

64
Q

Tetracyclines Adverse effects

A

Caution in immunocompromised patients; GI upset; rarely hepatotoxicity; Rapid IV infusion results in collapse/shock; tooth discoloration esophageal stricture in cats

65
Q

Chloramphenicol MOA

A

50s subunit with inhibition of peptidyl transferase

66
Q

Chloramphenicol ADME

A

Liquid is not well absorbed; excellent tissue distribution and relatively long half life

67
Q

Chloramphenicol Antibacterial activity

A

G+/- anaerobic; static

68
Q

Chloramphenicol Use (what not to do)

A

Don’t use with macrolides as compete with for same binding site

69
Q

Chloramphenicol Adverse effects

A

People: bone marrow suppression- aplasial of all lines- both dose dependent and independent; Dogs and cats may get dose dependent suppression; Decreased rate of digoxin elimination

70
Q

Sulfonamides MOA

A

Folate acid inhibitors; Structurally similar to PABA and act as competitive substrates (antimetabolites) for the synthetase enxyme. Potintiated acts at two steps which make it cidal

71
Q

Sulfonamides ADME

A

Good oral absorption; enterohepatic circulation and eliminated in urine; 70% metabolized by colonic bacteria. Some will have hepatic metabolisim. Good for prostate/CNS

72
Q

Sulfonamides Antibacterial Activity

A

G+/-; anaerobic; Static but if potinetiated cidal; Time dependent

73
Q

Sulfonamides Adverse effects

A

Immunological disease of the skin, kidney, liver and eye which are not dose dependeint. Incidence of 0.25%; thyroid suppression. Monitor STT and CBCs throughout treatment; Black/Tan delayed type 2 hypersensitivity

74
Q

Fluoroquinolones MOA

A

Disrupts DNA gyrase and DNA Topoisomerase activity

75
Q

Fluoroquinolones ADME

A

Renal elimination primarly with some fecal and hepatic; Not good CSF; Good tissue penetration because is lipid soluble and accumulates in phagocytic WBC; Oral bioavability is drug dependent.

76
Q

Fluoroquinolones Antibacterial Activity

A

G- and some G+; Cidial, Concentration dependent

77
Q

Fluoroquinolones Adverse effects

A

GI, cartilage deformities and ligament and tedon repair; Seizures and other CNS; dose dependent retinal degeneration. Induction of bacteriophage supergenes

78
Q

Ionophores (monincyn, improlium) MOA

A

Allow ions to cross cell membranes tag along through the channels

79
Q

Ionophores (monincyn, improlium) ADME

A

Feed additive for chicken and beef

80
Q

Ionophores (monincyn, improlium) activity

A

G+; Used to treat coccidia

81
Q

Nitrofurans MOA

A

Mechanism is unclear- may damage DNA

82
Q

Nitrofurans ADME

A

Reduced in liver, excreted by kidney, Reduced dose if renal compromised; Is not systemically distributed

83
Q

Nitrofurans what are they used for

A

Urinary pathogens; But not pseudomonas, klebsiella, proteus, serratia, acinetobactor

84
Q

Nitrofurans adervese effect

A

Neurological

85
Q

Nitroimidazoles Metronidazole MOA

A

Impairs microbal RNA and DNA synthesis but must first undergo nitrous reduction in the organism

86
Q

Nitroimidazoles Metronidazole ADME

A

Pirmarly liver elimination; distributes well to all tissues

87
Q

Nitroimidazoles Metronidazole Antibacterial activity

A

Anaerobic; Can be both time and concentration dependent

88
Q

Nitroimidazoles Metronidazole Adverse effects

A

Discolored urine (red-brown); GI upset; CNS adverse effects including seizures (not normal BBB more likely at small doses)

89
Q

Rifamycins MOA

A

Inihibits the B subunit of DNA-dependent RNA polymerase; suppressing RNA Synthesis

90
Q

Rifamycins ADME

A

Absorption may be higher in dogs with p-glycoprotein deficiency; Lipid soluble; excreted in bile

91
Q

Rifamycins Antibacterial Activity

A

G+, mycobacterium, neisseria, chlamydia, clostridium and bacteroides; static/cidial depending on tissue; concentration

92
Q

Rifamycins Adverse effects

A

Rapid resistance limits use to combination therapy; Red to orange colored excretions; Alk phos increase; MDR-1 dogs increased risk of adverse reactions

93
Q

Nitroimidazoles Metronidazole Reistance

A

Bacteria that lack necessary electron transport systems necessary to geneerate single electrons

94
Q

How do you treat metronidazole neurological sidefects

A

Give diazepam will help to recover faster

Oral dose as well

95
Q

Chloramphenicol benefits

A

Shown to inhibit production of beta-lactamases; potent inhibitor of drug metabolizing enzymes

96
Q

Macrolides GI motility

A

Improves for 2-3 doses then resitance to it in the gut; motilin mimitic

Board Review 2020 (37 decks)

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