Antibiotics Flashcards
Which type of bacteria have a thick cell wall?
Gram positive
What separates the outer membrane from the cell wall of gram negative bacteria?
Periplasm
How do bactericidal agents achieve sterilisation?
By directly killing bacteria
How do bacteriostatic act?
Suppress growth but do not directly sterilise the infected site
What is the issue with the lysis of bacteria by bactericidal agents?
This can lead to the release of toxins and inflammatory material
What is meant by the ‘spectrum’ of an antibiotic?
This refers to the range of bacterial species which are effectively treated by the antibiotic
All antibiotics within an antibiotic class will have a similar spectrum. T/F?
False
What is the difference between broad and narrow spectrum antibiotics?
Broad spectrum antibiotics are active against a wide range of bacteria
Narrow spectrum antibiotics are active against a limited range of bacteria
Describe the guided therapy strategy for the use of antibiotics?
This depends on identifying the cause of infection, an agent is then selected for use based on sensitivity testing
What spectrum of antibiotics are used for guided therapy?
Narrow spectrum
In guided therapy there is as little impact on colonisation and resistance as possible. What is the pay off for this?
The antibiotic often has limited action on the bacteria causing the infection
In empirical therapy there is extensive action against the bacteria which might be causing the infection. What is the pay off for this?
There is a large impact on colonisation and resistance
What spectrum of antibiotics are used for empirical therapy?
Broad spectrum
Describe the empirical therapy strategy for the use of antibiotics?
Used when the initiation of therapy cannot wait for culture results. A best guess therapy is used based on clinical and epidemiological acumen.
What is prophylactic therapy?
Used to prevent infection before it begins
What is the result of overgrowth of yeasts which can occur with the use of antibiotics?
Thrush
What is the result of overgrowth of the bowel which can occur with the use of antibiotics?
Diarrhoea
Which antibiotics are particularly associated with the development of c.difficile?
Clindamycin
Co-amoxiclav
Cephalosporins
Ciprofloxacin
C.difficile forms spores which can be difficult to eradicate from hospitals. T/F?
True
C.difficile can be difficult to treat as it has developed resistance to common antibiotic classes. T/F?
True
How is an uncomplicated UTI defined?
A common condition where there are lower urinary tract symptoms without sepsis of evidence of upper tract involvement
In uncomplicated UTI, you need to use an antibiotic with systemic activity. T/F?
False - the antibiotic only needs to sterilise the urine so there is no need for systemic activity
What is the first line agent used to treat uncomplicated UTI?
Trimethoprim
Why is trimethoprim a good choice of antibiotic for uncomplicated UTI in men?
It penetrates well into the prostate
Nitrofuratoin is an excellent broad spectrum antibiotic which is concentrated in the urine so has no effect on other tissues. In what cases should it not be used?
In renal failure nitrofurantoin will fail to concentrate in the urine so should not be used in this case
Nitrofuratoin is relatively non-toxic in short courses. What can be caused with long term use?
Pulmonary fibrosis
What bacteria commonly cause uncomplicated UTIs?
E.coli Other coliforms Pseudeomonas Staphylococcus Enterococcus
If there is a complicated UTI what is the best choice of antibiotic?
Ciprofloxacin
If a patient is severely unwell with a UTI then what antibiotics should be used?
Amoxicillin
Gentamicin
Beta lactase are safe for use in pregnancy. However, what is the risk of the use of broad spectrum beta-lactam agents in pregnancy?
These are associated with necrotising enterocolitis in premature infants
Why should tetracyclines should not be used in pregnancy?
These can cause bone and tooth abnormalities
Why should trimethoprim not be used in pregnancy?
Can cause neural tube defects in the first trimester
Why should nitrofurantoin not be used in pregnancy?
Can cause haemolytic anaemia in the third trimester of pregnancy
Why should aminoglycosides not be used in pregnancy?
Can cause ototoxicity in the second and third trimesters
Why should quinolones not be used in pregnancy?
Can cause bone and joint abnormalities
What are the four subclassifications of beta lactase antibiotics?
Penicillins
Cephalosporins
Carbapenems
monobactans
What is the brand name for the combination of amoxicillin and clavulanic acid?
Augmentin
What is the brand name for the combination of piperacillin and tazobactam
Tazocin
What is the mechanism of action of beta lactam antibiotics?
Inhibit the cross linking of cell wall peptidoglycan to cause lysis of the bacteria
Beta lactams are bacteriostatic antibiotics. T/F?
False - these are bactericidal
What kind of organisms typically secrete beta lactamases?
Gram negative organisms
S.aureus
Total antibiotic failure is likely with beta lactamases. T/F?
True
By which route are beta lactams usually given?
IV
When beta lactam antibiotics are given orally, what usually limits the dose?
Vomiting
What are the possible adverse effects of beta lactams?
Nausea and vomiting Diarrhoea Cholestasis Type 1 hypersensitivity Type 4 hypersensitivity Interstitial nephritis Candidiasis (oral or vulvovaginal) C.difficile infection Selection of resistance bacteria Seizure Haemolysis Leukopaenia
What is the most common presentation of type one hypersensitivity in patients on beta lactams?
Urticarial rash
Patients who are allergic to a penicillin will usually be allergic to other penicillins. T/F?
True
What organisms is Benzylpenicillin effective against?
Streptococcus
Clostridium
Neisseria
What organisms is amoxicillin effective against?
Streptococcus Enterococcus Neisseria Haemophilus Clostridium
What organisms is flucloxacillin effective against?
Streptococcus
Staphylococcus (not MRSA)
How is Benzylpenicillin administered?
IV
Flucloxacillin can be given orally. T/F?
True
What organisms are cephalosporins effective against?
Streptococcus Staphylococcus (not MRSA) E.coli Neisseria Haemophilus Bacterioles Clostridium Other coliform
How does the spectrum of cephalosporins change with each generation?
With each generation of cephalosporins the gram negative spectrum increases with some loss of gram positive activity
Give an example of a cephalosporin antibiotic?
Ceftriaxone
What organisms are carbapenems active against?
Ultra-broad spectrum antibiotics active against most bacteria expect MRSA
Carbapenems are resistant to beta lactamases. T/F?
True
Give an example of carbapenem.
Meropenem
What is the only monobactam currently in use?
Aztreonam
Aztreonams can be given to those with a penicillin allergy. T/F?
True
How is aztreonam administered?
IV
What class of bacteria is vancomycin active against?
Gram positive organisms
How is vancomycin administered?
IV
Why is vancomycin effective against resistant organisms such as MRSA?
It is not dependent on penicillin binding proteins
A loading dose of vancomycin is usually given. T/F?
True
Drug monitoring is required for vancomycin. T/F?
True - it has a narrow TI
What are the possible toxicities of vancomycin?
Nephrotoxicity
Ototoxicity
What happens when vancomycin is injected too rapidly?
red man syndrome - anaphylactoid reaction
What classes of protein synthesis inhibitors target the 50S ribosomes?
Macrolides
Clindamycin
Chloramphenicol
What classes of protein synthesis inhibitors target the 30S ribosomes?
Aminoglycosides
Tetracyclines
What ‘atypical’ organisms is clarithromycin effective against?
Legionella Mycoplasma Coxiella Chlamydia Chlamydophila
What is the spectrum of action of calrithromycin?
Active against gram positive and respiratory gram negative bacteria as well as ‘atypical’ bacteria
Macrolides can be given orally even in severe infection T/F?
True
Give examples of macrolides?
Erythromycin
Clarithromycin
Azithromycin
What are the possible adverse effects of macrolides?
Diarrhoea and vomiting QT prolongation Hearing loss (in long term use)
Give examples of drugs which macrolides interact with?
Statins
Warfarin
Resistance to macrolides is common among ‘atypical’ pathogens’ but uncommon among ‘typical’ pathogens. T/F?
False - the opposite is true
Clindamycin is given IV. T/F?
False - its has excellent oral absorption
What organisms is clindamycin effective against?
Bacterioles
Clostridium
Staphylococcus
Streptococcus
Why is clindamycin notorious for causing c.difficile?
Its effective on anaerobes means that is is particularly effective at disrupting colonic flora
Clindamycin is highly effective at stopping exotoxin production. As such, what conditions is it used to treat?
Toxic shock syndrome
Necrotising fascitis
Other gram positive toxin mediated disease
What are the possible toxic effects of chloramphenicol?
Bone marrow suppression
Aplastic anemia
Optic neuritis
In what situations is chloramphenicol used?
Topical therapy to the eye
Bacterial meningitis with beta lactam allergy
What are the possible toxic effects of amnioglycosides?
Hearing loss, loss of balance and oscillopsia
Neuromuscular blockade in patients with myasthenia gravis
Nephrotoxicity
For how long is it appropriate to give a course of gentamicin?
3 days
Describe the rationale behind the dosing regimen for gentamicin?
A high initial dose is given to take advantage of the rapid killing seen at high doses
A long dosing interval of 24-48 hours is left in order to minimise toxicity
In this time there is a prolonged post-antibiotic bacteriostatic effect
What organisms are tetracyclines effective against?
Streptococcus Staphylococcus Neisseria Haemophilus Enterococcus Mycoplasma Coxiella Chlamydia Chlamydophila Rickettsia
Give examples of quinolones
Ciprofloxacin
Levofloxacin
Quinolones are always given by IV. T/F?
False - oral dosing can be used even in severe infection
What organisms is levofloxacin affective against?
Streptococcus
Staphylococcus
Also some activity against gram negative
What organisms is ciprofloxacin affective against?
Gram negative bacteria
Some action against streptococcus and staphylococcus
What type of infections is ciprofloxacin used to treat?
UTI
Abdominal infections
What type of infections is levofloxacin used to treat?
Respiratory tract infections
What are the possible toxicities associated with quinolones?
GI toxicity
QT prolongation
Tendonitis
C.difficile infection
In what situations is rifampicin used?
Tuberculosis
Serious gram positive (especially S.aureus) infection
Why are drug interactions very important to consider when prescribing rifampicin?
Rifampicin is a potent CYP450 enzyme inducer
What four antibiotics are used in standard short course therapy against TB?
Isoniazid
Rifampicin
Pyrazamide
Ethambutol
What is the mechanism of action fo quinolones and rifampicin?
DNA and RNA biosynthesis inhibitors
Trimethoprim causes an elevation inc creatine which doe not reflect a fall in GFR. T/F?
True
What are some of the problems associated with the use of trimethoprim?
Causes an elevation in serum potassium (problematic in patients with chronic renal impairment)
Rash
GO disturbance
Co-trimoxazole (a combination of trimethoprim and sulphamethoxazole) is commonly used. T/F?
False. - it is only used in specialist care due to its significant additional toxicity
What type of bacteria is emtronidazole effective against?
Most anaerobic bacteria
What type of infection is metronidazole used to treat?
Intra-adominal infections
Metronidazole causes an unpleasant reaction with alcohol. T/F?
True
Why folate synthesis inhibitor can cause peripheral neuropathy?
Metronidazole
Which antibiotic is used to treat mild c.difficile infection?
Oral metronidazole
Which antibiotic is used to treat severe c.difficile infection?
Oral vancomycin
What is sepsis six?
A range of medical therapies used in the investigation/treatment of possible sepsis. This includes:
Titrate oxygen to sats >94%
Administer IV empiric antibiotics
Start IV fluid resuscitation
Take blood cultures to investigate source of infection
Measure serial serum lactases
Urine output measurement
Lactate dehydrogenase is used as a generally marker of injury to cells. T/F?
True
What is the benefit of lactase blood tests?
Helps to assess levels of hypoxia and lactic acidosis
