Lecture 7 - Antibiotics And Resistance Flashcards
What are categories of antimicrobials?
Anti-bacterials
Anti-fungal
Anti-viral
Anti-protozoals
What does it mean if an Antibacterial is Bactericidal?
Completely kills bacteria
What does it mean if an antibiotic is Bacteriostatic?
Prevents bacterial replication
What is meant by a broad spectrum antibiotic?
Targets lots of different types of bacteria
What are some examples of broad categories that a broad spectrum antibiotic might act on?
Gram +
Gram -
Anaerobic
How can antibiotics sensitivity/effectiveness be measured?
Paper disc soaked in antibiotic
Disc placed in agar culture of bacteria
Area of clearance measured (diameter)
Larger diameter = more effective
What is MIC (Minimum Inhibitory Concentration)?
The minimum concentration of antimicrobial agent which visibly inhibits growth
What are the 4 main mechanisms of action of anti bacterial?
Cell wall synthesis Inhibitors
Proteins synthesis inhibitors
Nucleic acid synthesis Inhibitors
Cell membrane function Inhibitors
What type of mechanism of antibacterial action does Penicillin have?
Cell wall synthesis inhibitor
How does Penicllin actually act as a cell wall synthesis inhibitor?
Prevents formation of cross linkages in cell wall
It binds to the penicillin binding protein which prevents the binding protein forming cross linkages
What are the 2 types of antibiotic resistance?
Intrinsic
Acquired
What is intrinsic antibiotic resistance?
When a species is naturally resistant to an antibiotic
Why do some bacteria have intrinsic antibiotic resistance?
The specific characteristics that the antibiotic targets not on bacteria
Doesn’t have target protein on bacteria surface
What is acquired antibiotic resistance?
When new genetic material is acquired or mutation occurs
How does a bacteria get acquired immunity from acquiring new genetic material?
Horizontal gene transfer (Plasmid)
What is the process of horizontal gene transfer?
Pili between donor and recipient bacteria extend and conjugate with each other
Donor plasmid replicates
Single stranded DNA from plasmid enters into recipient
What is adaptive antibiotic resistance?
When the bacteria responds to a stress (like low levels of antibiotic)
What are the mechanisms for antibiotic resistance (acquired)?
-Enzyme modification to destroy antibiotics
-Enzyme modification to change the target for antibiotic (cant bind)
-Target for antibiotic mutates and changes (cant bind)
What mechanism of action do Beta-lactams have?
Cell wall synthesis inhibition
What antibiotics are in the Beta-lactam family?
-Penicillins
-Cephalosporins
-Carbapenems
-Glycopeptides
What are the penicillins?
(Order is most narrow spectrum at the top, most broad spectrum at the bottom)
Benzylpenicillin
Penicillin V
Amoxicillin
Flucloxacillin
What is an example of a Cephalosporin?
Ceftriaxone
What are some Carbapenems?
Meropenem
Imipenem
What IV antibiotic is commonly given as a first line defence to sepsis?
Ceftriaxone
What bacteria does penicillin usually work on?
Streptococci
(Gram +)
What bacteria does Amoxicillin work on?
Gram + and some Gram -
What does Flucloxacillin work against?
Staphylococci and Streptococci
(Both gram +)
Why do you typically pair cephalosporins with another antibiotic?
They have no anaerobe activity
What type of infections are Carbapenems used for?
What group of people to you have to be careful using carbapenems like meropenem and imipenem with?
Gram negative infections
Normally safe with penicillin allergy but safer to avoid
Very broad spectrum (inc anaerobes)
What are 2 glycopeptides?
-Vancomycin
-Teicoplanin
What bacteria does Vancomycin and Teicoplanin act against?
Gram +
How is vancomycin usually administered and why?
IV antibiotic
Not absorbed into the body in the gut
When is Vancomycin delivered orally?
What infection is it used for and why?
With C.difficile
Stays in the lumen of the gut since it can’t be absorbed
What are the major side effects/concerns with cephalosporins?
C.difficile infection
When is Teicoplanin usually given instead of Vancomycin?
When patient no longer in hospital (IV is more difficult)
When is a Tetracycline e.g Doxycycline used?
Penicillin allergy
Gram + bacteria But is Broad spectrum
How are tetracyclines (doxycycline) always given?
Oral
Who should never receive tetracyclines like doxycycline and why?
Children younger than 12yrs
Pregnant or Breastfeeding women
Causes staining of developing bones and teeth
What mechanism of action do tetracyclines act by?
Protein synthesis inhibition
What are 3 groups of antibiotics that act via the protein synthesis inhibition mechanism?
-Aminoglycosides
-Tetracyclines
-Macrolides
ATM
Go to the ATM because protein is expensive AF
What is the most common Aminoglycoside?
What is the mechanism of action of this antibiotic?
Gentamicin
Protein synthesis inhibition
When are Amino-glycosides mainly used/reserved for?
Severe Gram negative sepsis
Good against gram negative bacteria
Why are Aminoglycosides like gentamicin reserved for severe gram negative sepsis?
Potentially nephrotoxic so requires constant monitoring since its easy to reach toxic levels
What is an example of a Macrolides?
What is the mechanism of action of this antibiotic?
Erythromycin
Protein synthesis inhibition
What ribosome subunit do tetracyclines and Aminoglycosides target?
30s
What subunit do Macrolides and Linezolids target?
50s
What are 3 groups of Nucleic acid synthesis inhibitors (DNA or RNA)?
-Quinolones
-Trimethoprim
-Rifampicin
What is the most common Quinolone?
What is this antibiotics method of action?
Ciprofloxacin
Nucleic acid synthesis inhibition
What are the risks surrounding use of Quinolones like Ciprofloxacin?
Risk of Tendinitis and rupture (Achilles tendon)
Aortic dissection (tearing of aorta)
C.difficile
How do Trimethoprim and sulphonamides inhibit DNA synthesis in a bacteria?
Inhibits folic acid synthesis
What is Co-trimoxazole?
Trimethoprim + sulphamethoxazole
What microorganism is Co-trimoxazole used to treat?
What disease does this microbe usually cause?
When is this infection commonly seen?
Pneumocystis jirovecii (PJP)
A fungal pneumonia
Causes Pneumocystis pneumonia
Pneumocystis pneumonia commonly seen in patients with HIV infection (immunocompromised)
What disease does the organism Pneumocystis jirovecii cause?
PCP (Pneumocystis pneumonia)
What is PCP and who are more prone to developing it?
A fungal pneumonia caused by the fungus Pneumocytis jirovecii
People with HIV/AIDS
What are the 2 categories of Antifungals?
-Azoles
-Polyenes
What is the mechanism of action of Azoles?
What category of anti-microbial are they?
Inhibit cell-membrane synthesis
Anti-fungal
What are the most common Azoles?
Fluconazole
Itra/Vori/posaconazole
What does Fluconazole treat?
Candida (thrush)
What Itra/vori/posaconazole used to treat?
Aspergillus
What are 2 polyenes?
What broad category of anti-microbial are these a part of?
Nystatin
Amphotericin
Anti-fungal
What is nystatin used for?
Topical treatment of Candida
What is Amphotericin used to treat?
What category of anti-microbial is it?
Systemic fungal infections (Aspergillus) via IV
Anti-fungal
What are 2 Antivirals?
Acyclovir
Oseltamivir
What does Acyclovir treat?
Herpes simplex (genital herpes + encephalitis)
Varicella zoster - chicken pox and shingles
What does Oseltamivir treat?
Influenza A and B
What microbes does Metronidazole work against?
Its an:
Antibacterial (anaerobic)
Antiprotozoal
What Protozoa is Metronidazole effective against?
Amoebae (dysentery and systemic)
Giardia (diarrhoea)
Trichomonas vaginalis (vaginitis)
