Antibiotics 2 Flashcards by Deepu pras

What is amoxycillin good for?

Gram negative bacteria

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What is the problem with using amoxycillin?

It is susceptible to beta lactamases

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How is amoxycillin’s weakness to beta lactamases countered?

By combining it with clavulanic acid in augmentin

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Why is cephalexin prescribed for S. aureus?

Because it is good against gram positive

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Can cephalexin function adequately in gram negatives?

Yes, unless they produce beta lactamases cephalosporinases

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What is nitrofuran?

An antibiotic used against UTIs.

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Why is nitrofuran only used for UTIs?

It has almost no tissue penetration but passes through urine if renal function is normal

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Why is nitrofurantoin avoided in elderly?

Their kidneys are often not good at concentrating the antibiotic enough.

If people are on it it can cause pulmonary fibrosis

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When is trimethoprim used alone?

Only in the cause of treating UTIs

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What is trimethoprim commonly used with?

Sulphamethoxazole

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What are the only oral antibiotics that can treat pseudomonas aeruginosa?

Norfloxacin and ciprofloxacin

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What is norflaxacin?

A quinolone antibiotic

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Why is norfloxacin not used to treat the UTI in the old lady’s case study?

It is of the few drugs that can treat pseudomonas so it would be a waste if it was used against E.coli

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How is pseudomonas aeruginosa so good at resisting antibiotics?

It has active efflux mechanisms for beta lactams

It has reduced ingress of antibiotics like imipenem and aminoglycosides

It destroys antibiotic beta lactamases

PBPs and DNA gyrases with low affinity for beta lactams and quinolones

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Which beta lactam antibiotic is effective against pseudomonas?

Piperacillin (Found and used as tazocin)

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What cephalosporins are used to treat pseudomonas aeruginosa infections?

Cefepime

Ceftazidime

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What carbapenems are used against pseudomonas aeruginosa and when?

They are last resort drugs. The ones typically used for pseudomonas are:

imipenem

meropenem

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What carbapenems are commonly used but not effective against pseudomonas aeruginosa?

Ertepenem (No activity against pseudomonas aeruginosa)

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Which monobactams work against pseudomonas?

Aztreonam

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Which aminoglycosides work against pseudomonas aeruginosa?

Gentamicin

Tobramicin

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Which quinolones work against pseudomonas bacteria?

Norfloxacin

Ciprofloxacin

Moxifloxacin

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Why must damage be taken when using aminoglycosides?

They can damage kidneys

Can damage hearing

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Will anti-pseudomonas drugs always be effective?

No some strains develop resistance

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What are common causes of pneumonia?

Streptococcus pneumonia

Staph aureus

Enterobacteriaceae

Pseudomonas aeruginosa

Acinetobacter

Stenotrophomonas

What are the generations of cephalosoprins based on?

How long they've been around and spectrum + activity

What are some the 1st generation cephalosporins?

Cephalexin Cefazolin

What are the 2nd generation cephalosporins?

cefaclor cefamandole Cefuroxime

What are the 3rd generation cephalosporins?

Cefotaxime Ceftriaxone Ceftaziidime

What is the 4th generation cephalosporin?

Cefepime

What is the newest cephalosporin?

Ceftaroline

What is the spectrum of 1st gen cephalosporins?

S. aureus streptococci Strep (some Enterobacteriaceae)

What is the spectrum of 2nd gen cephalosporins?

S. aureus Strep E. bacteriaceae H. influenzae

What is the spectrum of 3rd gen cephalosporins?

E'bacteriaceae strep H.influenzae P. aeruginosa (ceftazidime)

What is the spectrum of 4th gen cephalosporins?

``` E'bacteriaceae S.aureus Strep H.influenzae P.aeruginosa ```

What is the spectrum of 5th gen cephalosporins?

S. aureus (inc. MRSA) strep H.influenzae E'bacteriaceae

What are enterococci always resistant to?

cephalosporins

What are the 2 types of beta-lactamase mediated resistance?

ampC beta-lactamase production Extended spectrum beta-lactamase (ESBL) production

Where is the gene for ampC beta-lactamase located?

On a chromosome; it is normally repressed but inducers can result in its in production.

Which generation is most commonly destroyed by ampC beta-lactamase production?

3rd generation

What are inducers in the case of ampC?

Other antibiotics which may or may not be susceptible to destruction by ampC cephalosporinase.

What can a mutation in the ampC beta-lactamase gene result in?

It can cause the ampC beta-lactamase to be de-repressed stably.

Why is ampC beta-lactamase a problem if it is repressed?

These cephalosporinases destroy 3rd generation cephalosporins and so the mutation is selected for

Which bacteria are capable of ampC beta-lactamase production?

``` Enterobacter Serratia Citrobacter freundii Acinetobacter Proteus vulgaris and providencia Pseudomonas aeruginosa Morganella ```

What is ESBL production?

Production of Extended Spectrum beta-lactamases which are capable of destroying cephalosporins

Where were ESBL originally found?

Klebsiella E.coli Proteus mirabilis Enterobacter Citrobacter

What are ESBLs active against?

Older penicillins and cephalosporins 3rd gen cephalosporins aztreonam piperacillin May carry unrelated genes conferring resistance to aminoglycosides and fluoroquinolones

How are gram negative rods that produce ampC beta-lactamase and ESBL treated?

ampC beta lactamase: Carbapenems (meropenem) 4th gen cephalosporins Aztreonam Aminoglycosides Quinolones ESBL: Carbapenems 4th gen cephalosporins beta lactamase inhibitor combos Aminoglycosides Quinolones

What is happening to carbapenem effectiveness?

Carbapenemases are starting to show up nowadays in some bacteria making them resistant to them

What aminoglycosides are commonly used?

Gentamicin Tobramycin (less commonly)

What are the main features of aminoglycosides?

They are older Gentamicin is cheap They are potent against enterobacteriaceae and P.aeruginosa Also have activity against staphs and streps but not used as a first line therapy They are very toxic Often used with another agent

When is gentamicin used synergistically for strep infections?

In endocarditis it is used with peniciliin

What must be noted about aminoglycoside toxicity?

They are toxic to the ear (ototoxic) Nephrotoxic (use very cautiously in renal failure) Dose must be very calculated Blood levels must be monitored at all times

What do petechial lesions on conjunctivae and legs indicate?

Neisseria meningitidis

What is the empirical antibiotic response for bacterial meningitidis?

Ceftriaxone (to cover neisseria meningitidis, streptococcus pneumoniae, and haemophilus influenzae)

Which gram positive meningitis causing bacteria is high in resistance often to ceftriaxone?

Strep pneumoniae

Can N.meningitidis be transmitted without showing symtpoms?

Yes

What drugs are used for prophylaxes for families of people who have recently recovered from neisseria meningitidis?

One dose of ciprofloxacin (adults) 2 doses of rifampicin (children) ceftriaxone single IM injection in pregnant women

Does penicillin eradicate carrier state?