Overview antimicrobials

Question 1

Difference between cocci and bacilli

Answer 1

Cocci: spherical

Bacilli: rod-shaped

Question 2

Difference between staph and strept

Answer 2

Staph: clusters

Strept: chains

Question 3

Differential diagnosis examples of staphylococci based on coagulase

Answer 3

Positive: S. aureus

Negative: S. epidermis

Question 4

Differential diagnosis examples of streptococci based on haemolysis

Answer 4

A-haemolytic: Pneumococcus

B-haemolytic: Group A strep

Non-haemolytic: enterococcus

Question 5

Staphylococci and streptococci are gram…

Answer 5

Positive cocci

Question 6

Listeria, Cornynebacterium and Clostridium (AnO2) are gram…

Answer 6

Positive Bacilli

Question 7

Examples of gram negative cocci

Answer 7

• N. meningitidis
• N. gonorrhoea

Question 8

Examples of gram negative bacilli

Answer 8

• Bacteroides
• Pseudomona
• Haemophilus
• Enterobacteriaceae

Question 9

Examples of enterobacteriaceae

Answer 9

• E.coli
• Kebsiella
• Enterobacter
• Proteus

Question 10

Examples of atypical bacteria

Answer 10

Mycoplasma

Chlamydia

Question 11

Plasmodium spp. can be stained with

Answer 11

aniline dyes

Question 12

Arsphenamine killed…

Answer 12

spirochaetes

Question 13

Antibiotics that inhibit cell wall synthesis

Answer 13

Beta lactams (penicillins, cephalosporin, carbapenems) Glycopeptides (e.g. vancomycin, Teicoplanin)

Bacitracin, fosfomycin, isoniazid)

Question 14

Antibiotics that inhibit protein synthesis

Answer 14

Macrolides (e.g. erythromycin & clarithromycin) Aminoglycosides (e.g. gentamicin, amikacin)

Tetracyclines (Doxycycline, tigecycline)

(Lincosamides, rifamycins, mupirocin, linezolid)

Question 15

Antibiotics that interfer with DNA synthesis and replication

Answer 15

Nucleotide synth:

• Sulphanoamides (e.g. suplamethoxazole)
• Diaminopyrimidines (e.g. trimethoprim)

DNA gyrase inhibition:

• Quinolones (e.g. ciprofloxacin)
• Nitroimidazoles (e.g. metronidazole)

Question 16

Antibiotics that disrupt cell membrane

Answer 16

Polymixins (e.g. colistin)

Lipopeptides (e.g. daptomycin)

Question 17

Penicillin structure

Answer 17

Ring of: 3C, 1N, 1S

ONE modifiable residue.

Pen V better oral absorption than Pen G

• Flucloxacillin - better agains Staphyolococci

Question 18

Cephalosporin structure

Answer 18

A beta-lactam Ring of: 4C, 1N, 1S

TWO modifiable residues

Cefalexin: absorbed orally

Ceftazidime: active against pseudomonas

Question 19

Carbapenems

Answer 19

A beta-lactam Ring of: 4C, 1N

THREE modifiable residues

Ertapenem: long halflife

Meropenem: very broad spectrum

Question 20

Beta lactams, mode of action:

Answer 20

β-lactam antibiotics are bacteriocidal, and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls. The peptidoglycan layer is important for cell wall structural integrity, especially in Gram-positive organisms,

Question 21

Function and examples of Beta lactamase inhibitors

Answer 21

B-lactamase produced by many bacteria Hydrolysis of B-lactam ring results in inactivation. inhibitors like cavulanic acid have a B-lactam ring; binds lactamases andstops destruction of AB. Co-amoxiclav

Question 22

Glycopeptides, mode of action:

Answer 22

Vancomycin (IV) and teicoplanin (IV/IM) are most commonly used

Broad gram positive spectrum:

• MRSA, Coagulase negative Staphylococci
• Penicillin resistant Enterococci and Streptococci -

Clostridium difficile (PO Vanc.)

Question 23

Macrolides structure and example

Answer 23

Protein synthesis

Large ring forms core e.g. clarithromycin: CA-pneumonia, Legionalle, Mycoplasma

Question 24

Tetracycline structure and example

Answer 24

Four ringed structure, avoid in pregnancy and children(teeth) Doxycycline: oral and longacting

TIgecycline: glycylcycline with very broad spectrum

Question 25

Aminoglycosides structure and example

Answer 25

Inhibit protein synthesis * Three rings linked via oxygen residues * Narrow therapeutic window (toxicity) Gentamicin – single doses for sepsis Tobramycin – anti-pseudomonal in Cystic Fibrosis

Question 26

Locations at which protein synthesis is inhibited

Answer 26

Question 27

Macrolides function and example

Answer 27

Protein synthesis inhibitors (early) Sulphamethoxazole: combined with Trimethoprim to form ‘Co-trimoxazole’. * Toxicity a concern. * Used to treat/prevent PCP.

Question 28

Diaminopyrimidines function and example

Answer 28

Folate synthesis inhibitors (late) Avoid in first trimester of pregnancy Trimethoprim * Commonly used to treat urinary tract infections. Considered to be ‘bacteriostatic’.

Question 29

Quinolones function and example

Answer 29

Addition of fluorine atom * fluoroquinolones Stops DNA unwinding before replication Ciprofloxacin * versatile antibiotic * Concerns: MRSA and C. difficile CNS and musculoskeletal

Question 30

Considerations in treating fungal infections

Answer 30

Fungi are eukaryotes – fungal cells share more in common with human cells than bacteria Grouped as yeasts, molds and dimorphic Lead to mycosis

Question 31

Exxamples of antifungal drugs

Answer 31

**Azoles:** - triazoles (fluconazole) **Imidazoles** (clotrimazole) **Polyenes** - amphotericin B - nystatin **Echinocandins** - Caspofungin - Micafungin

Question 31

Exxamples of antifungal drugs

Answer 31

**Azoles:** - triazoles (fluconazole) **Imidazoles** (clotrimazole) **Polyenes -** amphotericin B - nystatin **Echinocandins-** Caspofungin Micafungin

Question 32

Triazole structure, function and example

Answer 32

Inhibit ergosterol synthesis, essential for fungal cell membranes Triazole rings have 3 nitrogens, 2 carbons **Fluconazole**: Broad spectrum including dermatophytes, Candida spp. and Cryptococcus spp.

Question 33

Polyenes structure, function and example

Answer 33

Binds ergosterol in fungal cell membranes Macrocyclic with C to C double bonds **Amphotericin B** – Given IV will treat most systemic mycoses. AmBisome is liposomal form to reduce toxicity.

Question 34

Echinocandins structure, function and example

Answer 34

Inhibit glucan synthesis in fungal cell wall Macrocyclic with carbon tail **Caspofungin** – Effective for systemic mycoses but less toxic than Amph. B. Only given intravenously.

Question 35

Sites of antifungal action

Answer 35

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