Extended spectrum B-lactamases - further mutations and the active site (B-lactam ring) means they can also inactivate: a. celphalosporins b. combination antibiotics (co-amoxiclav)

Antibiotics Flashcards by Kate Ledgard

5 methods of antibiotic resistance are:

Target site mutation - change in molecular configuration of antimicrobial binding site
Destruction of antimicrobial - e.g. B-lacatamase enzyme
Prevention of antimicrobial entry - modification to membrane porin channel size
Removal of anti-microbial from bacterium

How well did you know this?

Not at all

Perfectly

MRSA resistance mechanism

Methicillin Resistant Staphylococcus Aureus.

mecA gene encodes for penicillin binding protein 2a (PBP2a) - a mutation to this means penicillin can’t bind

How well did you know this?

Not at all

Perfectly

VRE resistance mechanism

Vancomycin resistant Enterococci

- plasmid mediated gene for altered a.a. on peptide chain prevents vancomycin form binding

How well did you know this?

Not at all

Perfectly

Gram negative B-lactamases resistance mechanism

The bacterium produce b-lactamase which hydrolyse the b-lactam ring of penicillin and cephalosporins
NB// typically remain sensitive to B-lactamase inhibitors

How well did you know this?

Not at all

Perfectly

ESBL resistance

Extended spectrum B-lactamases

further mutations and the active site (B-lactam ring) means they can also inactivate:
a. celphalosporins
b. combination antibiotics (co-amoxiclav)

How well did you know this?

Not at all

Perfectly

Antibiotic classes specific to GRAM -ve bacteria

aminoglycosides (streptomycin/gentamycin; inhibit protein synthesis)
trimethoprim (inhibit folate synthesis)

How well did you know this?

Not at all

Perfectly

Antibiotic classes specific to GRAM +ve bacteria

penicillins (amoxicillin) - disrupt peptidoglycan synthesis
macrolides (clarithromycin, erythromycin) - inhibit protein synthesis
lincosamide (clindamycin) - inhibits protein synthesis
glycopeptides (vancomysin/teicoplasin)

How well did you know this?

Not at all

Perfectly

Common uses of Macrolides

P - pneumonia
U - URI
S - STD
(clarithromycin/erythromycin)

How well did you know this?

Not at all

Perfectly

Common uses of ceftriazone

a cephalosporin (generational classes,, higher generation = broader)

-> gonococcus
-> meningococcus

How well did you know this?

Not at all

Perfectly

Common uses of vancomycin

a glycopeptide (target cell wall - monitor nephrotoxicity)
–>MRSA
–>enterococci
(some resistance e.g. VRE)

How well did you know this?

Not at all

Perfectly

Common uses of doxycycline

Lyme disease, Rickessetia, malaria prophylaxis, exacerbation of COPD, chlamydia
- broad spectrum tetracycline

How well did you know this?

Not at all

Perfectly

Treatment of TB

R - rifampicin
I - isoniazide
P - pyrazinamide
E - ethambutol

How well did you know this?

Not at all

Perfectly

Use of metronidaozole

anaerobic infections - INTRA-ABDOMINAL, pelvic, oral, soft tissue
inhibits nucleic acid synthesis
- gram +/- ve

How well did you know this?

Not at all

Perfectly

Mechanism of Penicillins

B-lactam rings. Inhibition of peptidoglycan cross linking -> disruption of gram +ve cell wall synthesis

How well did you know this?

Not at all

Perfectly

Indications for Benzylpenecillin

Streptococcal infection, clostridial infection, meningococcal infection.

How well did you know this?

Not at all

Perfectly

Contraindications and interactions to benzylpenecillin

Penicillin Allergy; interaction with methotrexate - excretion impaired -> toxicity

How well did you know this?

Not at all

Perfectly

What it the mechanism for flucloxacillin resistance

Penicillinase-resistant: side chain protects from B-lactamase

How well did you know this?

Not at all

Perfectly

Indications for flucloxacillin

Staphlococcal infection, osteomyelitis, septic arthritis

How well did you know this?

Not at all

Perfectly

Indications for amoxicillin

Empirical treatment of pneumonia, UTI

How well did you know this?

Not at all

Perfectly

Contraindications against flucloxacillin

penicillin allergy, previous liver toxicity

How well did you know this?

Not at all

Perfectly

Contraindications against amoxicillin

Penicillin allergy, severe renal impairment

How well did you know this?

Not at all

Perfectly

What forms co-amoxiclav?

amoxicillin & clavulanic acid

How well did you know this?

Not at all

Perfectly

Why is co-amoxiclav used, instead of other penicillins.

its broad-spectrum, clavulanic acid is a B-lactamase inhibitor

How well did you know this?

Not at all

Perfectly

Indications for co-amoxiclav.

Hospital acquired infections, intra-abdominal sepsis. H.pylori

How well did you know this?

Not at all

Perfectly

Contraindications and interactions of amoxicillin,

CI: penicillin, severe renal impairment; Interactions: methotrexate, excretion impaired -> toxicity

Indications for piperacillin + tazobactam (tazocin)

severe broad spectrum infection, Pseudomonas, immunocompromised

Indications for Cefotaxime

urinary and respiratory tract infections

Contraindications and interactions of cefotaxime

CI: penicillin allergy; Interactions: increases warfarin action, increases nephrotoxicity in aminoglycosides

Mechanism of Macrolides

Macrolides inhibit bacterial protein synthesis

2 examples of macrolides

Erythromycin, and clarithromycin. Oral & IV

Indications for macrolides

Resp & skin (if penicillin allergy), severe pneumonia, peptic ulcer (eradicate H.pylori)

Contraindications, and interactions and adverse effects for macrolides.

CI: macrolide hypersensitivity Interactions: drugs metabilised by CYTP450; Adverse effects: irritant (nausea)

MOA of quinolones

Inhibits DNA synthesis

Example of quinolones

ciprofloxacin or moxifloxacin

Formation of resistance of quinolones

bacteria rapidly develop resistance (2nd or 3rd line)

Indications for quinolones

UTI, severe GI infection (shigella, campylobacter), lower UTI, malaria.

Contraindication, interactions and adverse effects for quinolones

CI: seizures, growing, cardiac disease; Interactions: theophylline; AE: GI upset, C.difficile colitus

Mechanism of action of metronidazole

inhibits bacterail DNA synthesis, anaerobic bacteria activate it. IV, oral, PR

Indications for metronidazole

protozoal infection, anaerobes, H. pylori (with macrolide), C. difficile

Contraindications of metronidazole

liver disease | don't use with alcohol

Metronidazole interactions and adverse effects

Interactions: warfarin, phenytoin, cytochrome P450; | no significant adverse effects

MOA of antifungals

Binds to fungal membrane protein ergosterol

Examples of antifungals and route of administration

Nystin, clotrimazole, fluconazole; | oral or topical

Indication & Contraindications for fluconazole

Indications - fungal infection | Contraindications - liver disease

Drug interactions for fluconazole

drugs metabolised by cytochrome P450

Mechanism of action of nitrofurantoin

Activated in bacterial cells, damages DNA.

Indication for use of nitofurantoin

Uncomplicated LUTI (concentrates in urine)

MOA of aminoglycosides

inhibits 30s ribosomal unit --> no bacterial protein synthesis

3 examples of aminoglycosides

- gentamycin - neomycin - streptomycin

Indications for aminoglycosides

serious GRAM -VEs. Pseudomonas, severe sepsis, pylonephritis, endocarditis, NOT anaerobes

Contraindications for gentamycin

Myasthenia gravis

Aminoglycoside interactions and adverse effects

Interactions: furisemide | Adverse effects: ototxicity, nephrotoxicity

Vancomycin mechanism of action

inhibits peptidoglycan cross linking --> disruption of gram +ve cell wall synthesis

Is Vancomycin 1st or 2nd line treatment?

Vancomycin is 2nd line following resistance.

indications for vancomycin

severe c.diff, MRSA, Gram +ve aerobic an anaerobic e.g. endocarditis

vancomycin interactions and adverse effects

I's: aminoglycosides and loop diuretics | AE: ototxicity, nephrotoxicity

MOA of tetracyclines

Inhibits 30s ribosomal unit -> no bacterial protein synthosis

2 examples of tetracyclines

- doxycycline | - lymecycline

Indications for tetracyclines

Acne vulgaris, lower resp tract infection -> H. influenzae, pneumonia

Contraindications for tetracyclines

Preg, breastfeeding, children <12, renal impairment

Interactions for tetracyclines

Ca2+, Fe2+, antacids, bind to tetracyclines --> not absorbed. increase the effect of warfarin (kill Vit K secreting bacteria)

Adverse effects of tetracyclines

nausea, vomiting, diarrhoea.

2 examples of trimethoprims

- trimethoprim | - co-trimoxazole

MOA of trimethoprim

inhibits bacterial folate synthesis. Bacteriostatic

MOA of co-trimoxazole

Inhibits bacterial folate synthesis, combines with sulfamethoxazole for bactericidal activity. Bactericidial.

Indications for trimethoprim

uncomplicated UTI, first line.

Indications for co-trimoxazole

Pneumocycstis pneumonia in the immunosuppressed

Contraindications of trimethoprim

Folate deficiency

Trimethoprim interactions and adverse effects

Interactions: Potassium elevating drugs | Adverse effects: rash

Mechanism of action of quinines

Reduces excitability of motor end plate; unknown function in relation to malaria

Examples of quinines

quinine sulphate

Indications for quinines

- noctural leg cramps | - no longer 1st line for Malaria

Contraindications for quinines

hearing loss

Interactions of quinines

Arrythmia medication.

Adverse effects of quinine

Tinnitus, deafness, blindness.