ANTIBIOTICS Flashcards
what two types of antibiotics inhibit cell wall synthesis?
beta lactams= penicillin, cephalosporin, carbapenams and monobactams
glycopeptides= vancomycin and teicolpanin
what 4 types of antibiotics are protein synthesis inhibitors?
aminoglycosides= gentamicin
macrolides= erythromycin, clarithromycin and azithromycin
tetracyclines= doxy
oxazolidinones
what 3 types of antibiotic are DNA synthesis inhibitors?
trimethoprim/sulphonamides
quinolone= nalidixic acid
fluroquinolones= ciprofloxacin, levofloxcain
what type of antibiotic is an RNA synthesis inhibitor?
rifampicin
give 2 types of antibiotics that are plasma membrane agents
daptomycin
polymycin
give 2 other types of antibiotics
nitrofurantoin
metronidazole (anaerobic)
what antibiotic group are penicillins?
beta lactams that contain B lactam ring= gives antimicrobial properties
are penicillins broad or narrow spectrum?
broad
how do penicillins work?
It inhibits enzyme cell wall synthesis by - preventing cross linking between peptidoglycan chains. Causing uncontrolled entry of water into bacteria causes cell swelling, lysis and death
what type of bacteria are targeted by penicillins?
gram +ve and -ve
when is the only instance that penicillins are taken well into the CNS?
inflammation of meninges
what other drugs should be used in caution if there is hypersensitivity to penicillin?
cephalosporins
other b lactams
how can bacteria inactive penicillins?
produce beta lactamases
name a serious GI side effect of penicillins
antibiotic associated colitis
how can penicillins interact with the COCP?
reduce effectveness
how can probenecid interact with penicillins?
reduce excretion - anti gout drug
give an example of a first generation cephalosporin
cephradine
give an example of a second generation cephalosporin
cefuroxime
give an example of a 3rd generation cephalosporin
cefotaxime
ceftazidime
ceftiaxone
how do cephalosporins work?
same as penicillin
cell wall synthesis inhibitor (prevent peptidoglycan cross linking)
which type of bacteria are second generation cephalosporins more active against?
They are less susceptible to B lactamase and effective against gram +ve
which type of bacteria are third generation cephalosporins more active against?
gram -ve
what cephalosporin is used in pneumocci and H.infleunzae meningitis?
cefotaxime
what kind of spectrum do cephalosporins have? What type of infections it is used for?
very broad
Second and third line treatment for urinary tract infection and respiratory tract infections
what respiratory condition can reduce the effectiveness of cephalosporins?
COPD
what drug can reduce excretion of cephalosporins?
probenecid
how do cephalosporins interact with warfarin?
increase anticoagulant effect
give an example of a glycopeptide
vancomycin
teicoplanin
how do glycopeptides work?
cell wall synthesis inhibitors
bind to cell wall and competitively inhibit cross linking
what types of bacteria are glycopeptides effective against?
gram +ve as they cannot degrade the cell wall of grame -ve
aerobic &anaerobic
MRSA TOO!
which glycopeptides would be used in endocarditis and c.diff, and the other in endocarditis, cellulitis peritonitis and diabetic foot infection?
a) vancomycin
b) teicoplanin
a) endocarditis, c. diff = vancomycin
b) endocarditis peritonitis, cellulitis and diabetic foot infection = teicoplanin
why should glycopeptides be used IV in systemic infections?
Poorly absorbed orally in systemic infections
glycopeptide should be avoided in the elderly in which circumstance?
history of deafness
Renal impairment
IV Glycopeptides can lead to which blood disorder?
neutropenia and thrombocytopenia
Name a serious side effect of giving infusing IV glycopeptide rapidly
Red man syndrome = generalised erythema +/- hypotension and bronchospasm
Name an ENT side effect of IV glycopeptides?
Ototoxicity leading to tinnitus and deafness
give an example of a tetracycline
doxycycline
how do tetracyclines work
Bacterial protein synthesis inhibitors
Binds to ribosome 30s sub unit specific to bacteria and prevents RNA translation
what is the spectrum of tetracyclines?
broad spectrum
Are tetracyclines bactericidal or bacteriostatic?
bacteriostatic
name 2 systems that tetracyclines are used to treat infections in
Respiratory= LRTI including infective exacerbation of COPD (h.influenzae), pneumonia and atypical pneumonia Genital= chlamydia and pelvic inflammatory disorders
name 2 skin conditions that tetracyclines are used in
acne rosacea
acne vulgaris
Name an infectious disease that tetracyclines are used to treat
Typhoid, anthrax, malaria and lyme
why shouldn’t tetracyclines be used in myasthenia gravis patients?
can increase muscle weakness
why shouldn’t tetracyclines be used in patients with SLE?
can exacerbate
why shouldn’t tetracyclines be used in children under 12?
deposits in growing bone and teeth - staining and hypoplasia
why shouldn’t tetracyclines be used in pregnancy and breastfeeding?
deposits in growing bone and teeth - staining and hypoplasia
what severe acute disease can be triggered by tetracyclines?
acute porphyria
name 2 neurological side effects of tetracyclines
photosensitivity
benign intracranial hypertension causing headache and blurred vision
how do tetracyclines interact with anticonvulsants?
increase doxycycline metabolism
how do tetracycline interact with methotrexate?
increase risk of toxicity
give an example of an aminoglycoside
gentamicin
streptomycin
amikacin
Tobramycin
how do aminoglycosides work?
protein synthesis inhibitors
They bind to ribosomal 30s subunit
They are bactericidal
What is infections are aminoglycosides generally used against?
1) Severe sepsis even when organism is unknown
2) pyelonephritis and complicated urinary tract infections
3) Biliary and other intra abdominal sepsis infections
why are aminoglycosides often used with beta lactams or metronidazole?
Lack activity against streptococci or anaerobes and therefore used in combination when the organism is unknown
what kind of bacteria are aminoglycosides effective against?
Mainly gram negative aerobic bacteria
Also pseudomonas aeruginosa
Some gram +ve (e.g staph)
which of these aminoglycosides would you use against p aeruginosa, then m tuberculosis
a) gentamicin
b) streptomycin
a) gent = p aeruginosa
b) strep = m tuberculosis
why should’t aminoglycosides be used in myasthenia gravis?
impair neuromuscular junction transmission
why shouldn’t aminoglycosides be used in 2nd or 3rd trimester of pregnancy?
Cross the placenta causing damage to the auditory and vestibular nerve
Streptomycin greatest risk
What renal side effect can you get with aminoglycosides?
Nephrotoxicity= reduced urine output and increase serum creatinine levels
Give a ENT side effect of aminoglycosides
ototoxicity= tinnitus and deafness
Aminoglycoside in combination with what drugs can potentiate nephrotoxicity?
Platinum Chemotherapy Cyclosporine Vancomycin Cephalosporin
Aminoglycoside in combination with what drugs can potentiate ototoxicity?
Loop diuretics and vancomycin
why shouldn’t aminoglycosides be used for more than 7 days?
toxicity risk
How is the dose of aminoglycoside calculated and how is it administrated?
Based on weight and renal function
IV
give an example of a macrolid
erythromycin
clarithromycin
azithromycin
Are macrolides bactericidal or bacteriostatic?
bacteriostatic
how do macrolides work?
protein synthesis inhibitors
They bind to ribosomal 50s subunit preventing translocation occurring
Inhibit protein elongation by blocking exit tunnel of ribosome
when are macrolides used?
Alternative to penicillin
Respiratory infection
Skin and soft tissue infection
Serious pneumonia with penicillin and atypical pneumonia (Legionella pneumophila and Mycoplasma pneumoniae)
Non-gonococcal urethritis= erythromycin
Uncomplicated chlamydia infection
Macrolides should be used with caution for patients with what ECG abnormality?
prolonged QT interval and arrhythmias
how should dosing change for a patient with a reduced eGFR?
half dose
What are the common abdominal side effects of oral macrolides?
Nausea and vomiting
Abdominal pain
Diarrohea
What is a cardiac side effect of macrolides?
QT interval prolonged which can lead to arrhythmias
What action does clarithromycin and erythromycin have on cytochrome p450?
Inhibit cytochrome p450
give an example of a fluoroquinolone
ciprofloxacin
Levofloxacin
Mexifloxacin
What type of organisms are quinolones most effective against?
Aerobic gram -ve bacteria
are fluoroquinolones bactericidal or bacteriostatic?
bactericidal
Are quinolones effective against gram +ve?
Ciprofloxacin has limited effect against +ve
Levofloxacin and mexifloxacin increased activity against +ve and therefore can be used in LRTI
what antibiotic might you use to treat campylobacter and neusseria?
fluroquinolones
how do fluoroquinolones work?
Inhibit DNA replication by interacting with bacteria specific enzyme that is invovled with DNA replication
which type of fluoroquinolone would be better to treat CAP and why?
a) levofloxacin
b) ciprofloxacin
a) levofloxacin (greater against pneumococcal activity)
What is quinolones used to treat?
UTI and acute pyelenophritis (cipro) Severe GI tract infections= e.g. shigella and campylobacter LRTI= Levofloxacin and mexifloxacin Joint and bone infection Gonorrhea and septicaemia
what systemic infection are fluoroquinolones used to treat?
septicaemia
why shouldn’t fluoroquinolones be taken by patients with epilepsy or previous history of seizures?
lowers seizure threshold
why shouldn’t fluoroquinolones be used with cyclosporin?
increases nephrotoxicity
What is the effect of quinolones on cytochrome p450?
Inhibit the enzyme
why shouldn’t fluoroquinolones be used with
a) warfarin
b) theophylline?
a) increases anticoagulation
b) increase risk of convulsion and toxicity
What organisms are trimethoprim active against?
Broad spectrum Gram +ve and Gram -ve particullarly enterobacteria
how does trimethoprim work?
inhibit DNA synthesis by inhibiting folate synthesis (folic acid essential for making purines).
Leads to bacteriostatic
How is Co-trimoxazole made and what is it used for?
Trimethoprim and sulfamethoxazole (sulfonamide)
Used to treat pneumocystis pneumonia in immunosuppressed patients.
Also treat acute exacerbations of chronic bronchitis, UTI and otitis media in children = if their is bacterial sensitivity
Travellers diarrohea
when is trimethoprim normally used?
First line for UTI
Also used for respiratory tract infections, shigellosis, invasive salmonella infection
why shouldn’t trimethoprim be used in 1st trimester of pregnancy?
teratogenic causing cardiovascular defect and oral cleft due to folate antagonist
which blood disorders contraindicate use of trimethoprim?
anaemia
thrombocytopenia
Name an immunological side effect of trimethoprim
bone marrow suppression
give a severe two severe derm side effects of trimethoprim and especially co-trimoxazole
toxic epidermal necrolysis (TEN) and Steven’s Johnson Syndrome
why shouldn’t trimethoprim be used with cyclosporin?
increase nephrotoxicity
why shouldn’t trimethoprim be used with methotrexate (folate antagonist) and phenytoin (^ folate metabolism)?
Increases the risk of adverse haematological effects such as bone marrow suppression
give an example of an anaerobic antimicrobial
metronidazole and tinidazole
how does metronidazole work?
Passive diffusion into the anaerobic bacteria where it is reduced into free radical.
It damages the DNA synthesis causing DNA degradation and cell death
Bactericidal
What is the spectrum of activity for metronidazole?
Anaerobic bacteria and protozoa
What infections are metronidazole used to treat?
1) Abx assoicated collitis caused by C.diff ( anaerobic)
2) Oral infections including dental abscess and aspirated pneumonia caused by -VE anarebes
3) Surgical and gynaecological infections from -ve anaerobes from the colon
4) H.pylori eradication with PPI and clarithromycin
5) protozoa infections
what physiological state is metronidazole contraindicated in?
pregnancy, breastfeeding
What can high doses of prolonged treatment of metronidazole cause?
Peripheral and optic neuropathy, sieuzures and encalopathy
why shouldn’t metronidazole be taken with alcohol?
It inhibits the excretion of alcohol leading to symptoms of flushing, nausea and vomiting and headache
why shouldn’t metronidazole be used with phenytoin?
Causes phentyoin toxicity and can cause impaired cerebellar function
What effect does metronidazole have on P450?
It is metabolised by p450 and inhibits the enzyme
How does nitrofurantoin work?
It is metabolised and reduced by bacteria using nitrofuran reductase.
Forming the active metabolite that damages the bacterial DNA and causes cell death.
What two organisms is nitrofurantoin effective against?
Gram -ve E.coli and Gram +ve Staphylococcus saprophyticus. Two most common causes of UTI
when is nitrofurantoin mainly used?
Lower UTI = acute cystitis
What side effect does nitrofurantoin have on urine?
Cause it to go dark yellow or brown
when in the day should nitrofurantoin be taken?
With food or milk
what organ impairments contraindicate use of nitrofurantoin?
renal
hepatic
why is nitrofurantoin contraindicated in pregnancy and neonates?
increases risk of haemolytic anaemia
why is nitrofurantoin contraindicated for use with magnesium-containing antacids?
reduce absorption
What is the potential side effect of prolonged used for nitrofurantoin?
Chronic pulmonary reaction (fibrosis), hepatitis and peripheral neuropathy
What are the 4 different types of penicillin?
Give example for each
Broad spectrum penicillin = Co amoxiclav and amoxicillin
Benzylpenicillin
Antipseudomonal penicillin’s= Piperacillin with tazobactam
Penicillinase resistant penicillin = Flucloxacillin
Impairment of what organ would be contradictory to give penicillin?
Renal impairment
What is the side effect of high doses of penicillin or when given to patient with renal impairment ?
- Central nervous system toxicity (including convulsions and coma)
what is the interaction between penicillin and methotrexate?
- Penicillins reduce renal excretion of methotrexate, increasing the risk of toxicity.
Are cephalosporins and carbapenems more or less resistant to beta lactamase produced by bacteria?
More resistant to beta lactemase due to fusion of their beta lactam rings
What antibiotics are linked to the development of C.difficile?
Cephalosporins
Ciprofloxacin (and other quinolones)
Clindamycin
Co-amoxiclav
IV carbapenems and cephalosporins are used in what situations?
To tackle very severe and complicated infections caused by antibiotic resistant organisms
What effect does cephalosporin have on aminoglycoside?
Increase the nephrotoxicity effects of aminoglycoside
What is the effect of cephalosporin on valproate?
It reduces the plasma level and efficancy of valproate
What route is vancomycin given for abx associated colitis caused by c.diff?
Oral
What renal side effect is caused by IV glycopeptide?
Nephrotoxicity ( less in teicoplanin)
What is the most common side effect of IV glycopeptide?
Thrombophlebitis at sight of IV
Vancomycin Interaction with what drugs increases the risk of ototoxicity and/or nephrotoxicity?
Aminoglycoside
Cyclosporin
Loop diuretics
What are the 2 general uses of penicllin?
LRTI
Urinary tract infection
What is broad spectrum penicillin used for?
Empirical treatment for pneumonia either gram +ve (Pneumoccocus pneumonia) or Gram -ve (H.influenzae)
and Urinary tract infection ( caused by E.coli)
Also in combination therapy for H pyolri peptic ulcer disease
What is Co-amoxiclav?
Amoxicillin and clavulanic acid
What is the benefit or Co-amoxiclav over amoxicillin?
Great range of activity
What combination therapy is Co-amoxiclav used in?
Hospital acquired infections and intra abdominal sepsis
What does Strep pneumonia and E.coli produce to be resistant to broad spectrum penicillin?
Penicillinase
What is the range of use of benzylpenicillin?
Streptococcal infections= Tonsillitis, pneumonia and endocarditis
Clostridium infections= tetanus
Meningococcal infections = Meningitis and septicaemia
Benzylpenicillin is given for skin and soft tissue infection in what situations and in combination with what drug?
In severe infections and combination with flucloxacillin
What is benzylpenicillin limitation?
It is inactivated by B lactamase
What is tazocin?
Piperacillin with tazobactam
What bacteria is tazocin specifically used against?
pseudomonal infections
Tazocin are preserved for use in what situations?
Severe infection with a range of pathogens
Hospital acquired infection such as HAP
Patient is immunocompromised (neutropenic)
What are the infections in which tazocin are used for?
HAP
Complicated Urinary tract infection
Intraabdominal sepsis
Complicated Skin and soft tissue infection
What is Flucloxacillin specifically used for?
Penicillin resistant staphylococci infection
Why is Flucloxacillin used for staphylococci infections instead of benzylpenicillin?
Staphylococci produce penicillinase which is resistant to benzylpenicillin
What infections are flucloxacillin commonly used in?
Impetigo and cellulitis
Osteomyelitis and septic arthritis
Endocarditis
What % of patients have a penicillin allergy?
1-10%
What is the common presentation of penicillin allergy?
Get a skin rash (urticarial) 7-10 days after treatment
1-3 days after treatment if repeated dose s
(Delayed IgE mediated reaction)
What happens in anaphylactic reaction to penicillin?
Angioedema
Bronchospasm
Hypotension
Which antibiotics increase warfarin’s anticoagulation effects?
Tetracycline, Cephalosporin, Broad Penicillin and tazocin
Example of 5th generation cephalosporin?
Ceftaroline fosamil
What bacteria does ceftazidime have good activity against?
Pseudomonas
What infection is telavancin used for?
HAP
What is the most common used aminoglycoside?
Gentamicin
What infections are gentamicin solely used for?
Bacterial endocarditis ( with other abx) Iisteria Meningitis and other CNS infection Pseudomonas aeruginosa
What is streptomycin used for?
Treatment of mycobacterium tuberculosis
Why are gram +ve and anaerobics resistant to aminoglycoside
Do not contain the oxygen transporting system
What effect do macrolides have on
a) warfarin
b) statin
a) can lead to bleeding
b) can lead to myopathy
What effect do erythromycin and clarithromycin have on drugs that are metabolised by cytochrome p450?
Increase their plasma concentration as cytochrome p450 metabolism is being blocked
What MSK side effect does clarithromycin have?
Myalgia and arthralgia
What drugs should macrolides and quinolones not be used with in risk of further prolongation of the QT interval?
SSRI’s, antipsychotics, amiodaron, quninine and each other
Give example of gram -ve bacteria in which quinolones are effective against?
Campylobacter Pseudomonas Shigella Salmonella NEISSERIA
What is oral ciprofloxacin used for?
Pseudomonas aeruginosa
What is the interaction of quinolones and NSAIDS?
Increase risk of seizures
What is the interaction of quinolones and prednisolone?
Increase risk of tendon rupture
What drugs reduce the absorption of quinolones?
Drugs that contain divalent cations such as calcium and antacids
Why should quinolones be avoided in children and young adolescents?
Causes arthropathy
Why is quinolones usually second and third line treatment?
Due to the rapid development of resistance to them and their association with C.diff infection
What is a MSK side effect of quinolones?
Inflammation and rupture of muscle tendons
What cardiac side effect of quinolones?
Increase QT interval
What is a severe side effect of trimethoprim?
It can cause haematological disorders= should be avoided in the elderly
Trimethoprim can cause hyperkalemia. Therefore what drugs should be avoided?
Aldosterone antagonist, ACH inhibitor and angiotensin receptor blocker
What is the common side effects of trimethoprim?
Nausea and vomiting
Sore throat
Rash
What are the three abx of choice for UTI?
Trimethoprim
Amoxicillin
Nitrofurantoin
What abx are involved in the eradication of H.pylori?
PPI + clarithromycin + either amoxicillin or metronidazole
Who are particularly susceptible to adverse affects of TRIMETHOPRIM?
Neonates, elderly and HIV patients
What respiratory tract infections are moxifloxacin and levofloxacin used in? When are they used?
CAP
Sinusitis
Chronic bronchitis
2nd or 3rd line treatment
What 4 abx are contradictive in patients with myasanthia gravis?
Tetracylcine
Aminoglycoside
quinolones
marcolides
