Microbiology 1 Flashcards
What infections are associated with broad antibiotic spectrum use?
Candida
C.diff
What antibiotic has activity against gram positive and gram negative bacteria?
Meropenem
What does Benzyl-penicillin have activity against?
Streptococci
Neisseria
What are the three different types of antibiotic therapy?
Guided therapy
Empirical therapy
Prophylactic therapy
Beta-lactam antibiotics can be separated into four groups. What are they?
- Penicillin
- Cephalosporins
- Carbapenems
- Monobactams
Give three examples of penicillins
- Benzylpenicillin
- Flucloxacillin
- Amoxicillin
Give an example of a cephalosporin antibiotic
Ceftriaxone
Give an example of a cabapenem antibiotic
Meropenem
Give an example of a monobactem antibiotic
Aztreonam
What makes up Augmentin?
Amoxicillin + clavulanic acid
What makes up Tazocin?
Piperacillin + tazobactam
What is the MoA of beta-lactam antibiotics?
inhibit cross-linking of the cell wall peptidoglycan
Causes lysis of the bacteria
Bactericidal
Describe beta-lactamases
Enzymes that lyse and inactivate the beta-lactam drugs by lysis of the beta-lactam ring
What bacteria commonly secrete beta-lactamases?
Gram negatives
S.aureus
How are beta-lactam antibiotics excreted?
Unchanged in urine and bile
Why do beta-lactam antibiotics often need to be given IV?
Poorly absorbed via GI tract
Can cause vomiting which limits dose
What GI toxicity is associated with beta-lactam antibiotics?
Nausea and vomiting
Diarrhoea
Cholestasis - abnormal LFTs
What hypersensitivity reactions can occur following beta-lactam antibiotic use?
Stage 1 - urticaria, anaphylaxis
Stage 4 - Stephen-Johnson syndrome and toxic epidermal necrolysis
What infections are associated with beta-lactam antibiotic use?
Candidiasis - oral, vulvovaginal
C.diff
What are rare reactions associated with beta-lactam antibiotics?
Seizures
Haemolysis
Leukopenia
What is the first choice Abx for a serious streptococci infection such as erysipelas?
Benzylpenicillin
How should Benzylpenicillin be administered?
IV
What does amoxicillin have activity against?
Gram negative bacteria (streptococcus, enterococcus, Neisseria, haemophilus, clostidium)
What does flucloxacillin have activity against?
Staphylococcus aureus (not MRSA) Streptococci
Beta-lactamase inhibitors greatly broaden the activity of penicillins against which bacteria?
Gram negative
S.aureus
What bacteria do Cephalosporins have good activity against?
Gram positive
Gram negative
When is Ceftriaxone prescribed?
Bacterial meningitis
What type of beta-lactam antibiotics can be given to patients with a penicillin allergy?
Monobactems
How should monobactem antibiotics be administered?
IV - no oral absorption
What is the MoA of Vancomycin?
Inhibits cell wall formation in gram positive bacteria
For what type of infection is Vancomycin first line, and why?
MRSA
Not dependent upon penicillin binding proteins (PBP)
When should Vancomycin be given orally?
For treatment of C.diff
What toxicity is associated with Vancomycin?
Nephrotoxicity
Red Man Syndrome (give over 2-3 hours)
Ototoxicity
What 3 classes of antibiotics target the 50S subunit of bacterial ribosomes?
- Macrolides
- Clindamycin
- Chloramphenicol
What are three examples of macrolide antibiotics?
- Erythromycin
- Chlarithromycin
- Azithromycin
What 2 classes of antibiotics target the 30S subunit of bacterial ribosomes?
- Aminoglycosides
2. Tetracycline
Give an example of an aminioglycoside
Gentamicin
Give an example of a tetracylcine
Doxycycline
What activity do macrolides have?
Gram positive
Respiratory gram negatives
Atypicals (chlamdyia, legionella, mycoplasma)
How should macrolides be administered?
Orally (unless patient is severely unwell - vomiting or poorly perfused GIT)
What can clarithromycin be used against?
Streptococcus Staphylococcus Neisseria Haemophilus Enterococcus Atypicals
For what specific type of infection is clarithromycin useful for?
Respiratory tract infections
What are the adverse effects of macrolides?
D&V
QT prolongation
What drug interactions are associated with macrolides?
Simvastatin
Atorvastatin
Warfarin
What is the principle action of clindamycin?
Gram positives
What is clindamycin particularly good at doing?
Stopping exotoxin production
In what infections should clindamycin be given?
Toxic Shock Syndrome
Necrotizing fasciitis
Why should clindamycin not be given to patients who are more vulnerable at developing C.diff infections?
Very broad anaerobe activity
Disrupt gut flora
Increase risk of C.diff
How long can it take for the gut flora to recover its diversity following antibiotic use?
6-9 months
What are the 4 c.differgic antibiotics?
- Clindamycin
- Co-amoxiclav
- Cephalosporins
- Ciprofloxacin
What is the MoA of chloramphenicol?
Inhibits 50S ribosomal subunit
What are the toxic effects of chloramphenicol?
Bone marrow suppression
Aplastic anaemia
Optic neuritis
What are the uses of chloramphenicol?
Topic therapy to eyes
Bacterial meningitis with beta-lactam allergy
Aminoglycosides have activity against what type of bacteria?
Gram negative
What are the bacteriostatic and bactericidal effects of aminoglycosides?
Bacteriostatic - reversibly binds to 30S subunit
Bactericidal - affects cell membrane at high concentrations
What toxicity is associated with aminoglycosides?
Nephrotoxicity
Ototoxicity
Neuromuscular blockade - myasthenia gravis
Describe the dosing that should be used for aminoglycosides?
High initial dose - rapid killing
Long dosing interval (24-48h) - minimise toxicity
Measure trough level
3 days only
Tetracyclines have activity against what type of bacteria?
Streptococcus Staphylococcus Neisseria Haemophilus Enterococcus
Who should not be given tetracyclines and why?
Pregnant women
Children
Bone abnormalities
Tooth discolouration
What are the types of antibiotics which target DNA repair and replication?
Quinolones
Rifampicin
Give two examples of quinolones
Ciprofloxacin
Levofloxacin
Which quinolone has stronger activity against gram negative bacteria?
Ciprofloxacin
Which quinolone has stronger activity against gram positive bacteria?
Levofloxacin
For what type of infections is ciprofloxacin commonly used for?
UTI
Abdominal infection
What type of infection is levofloxacin commonly used for?
Respiratory tract infections
What toxicity is associated with quinolones?
GI toxicity
QT prolongation
Tendonitis
What is rifampicin particulary useful against?
Biofilms
What are the interactions associated with rifampicin?
Potent CYP450 inducer
Most drugs that undergo hepatic metabolism
OCP is ineffective
What is the mechanism of action of trimethoprim?
Inhibits folate synthesis
When should trimethoprim be used?
Uncomplicated UTI
What toxicity is associated with trimethoprim?
Elevation of serum creatinine (action on PCT)
Elevation of serum K (potassium sparing diuretic)
Rash and GI disturbances - uncommon
What toxicity is associated with co-trimoxazole?
Bone marrow suppression
Steven Johnson syndrome
What antibiotic causes an unpleasant reaction with alcohol?
Metrondiazole
What is the mechanism of action of metrondiazole?
Enters the bacteria by passive diffusion
Produces free radicals
What is metrondiazole effective against?
Anaerobic bacteria
What is associated with long term use of metrondiazole?
Peripheral neuropathy
In 80% of young women with cystitis, what is the causative bacteria?
E.coli
What is the first line antibiotic for uncomplicated UTI?
Trimethoprim
Apart from trimethoprim, what other antibiotic is useful for UTI infections?
Nitrofuratoin
When should nitrofuratoin be avoided?
In renal failure
What antibiotic should be used in complicated UTI (fever, flank pain but no sepsis)?
Ciprofloxacin (oral)
What antibiotic should be used in UTI with sepsis?
Gentamicin (lots of activity against E.coli but requires monitoring) IV
What antibiotics are not safe for use during pregnancy?
- Tetracyclines - bone/tooth abnormalities
- Trimethoprim - neural tube defect (1st trimester)
- Nitrofurantoin - haemolytic anaemia (3rd trimester)
- Aminoglycosides - ototoxicity (2/3rd trimester)
- Quinolones - bone/joint abnormalities
