Microbiology and Antibiotics Flashcards
What colour do Gram positive bacteria stain and why?
Purple/ blue
due to the presence of peptidoglycan in the cell wall
What kind of infections do gram positive bacteria typically cause?
Chest and skin infections
Examples of gram positive bacteria?
Gram positive cocci include:
- Staphylococci (are bunched and include S. aureus which is coagulase positive)
- Streptococci (form chains and include alpha haemolytic (pneumonia) beta haemolytic (pyogenes) and delta haemolytic forms (enterococci))
Gram positive rods include:
- Listeria
- Clostridium
What colour do gram negative bacteria stain?
Red/ pink
What kind of infections do gram negative bacteria cause?
GI infections and UTI’s
Examples of gram negative bacteria?
Gram negative cocci:
- Nisseria
Gram negative rods:
are mainly found as gut flora or lead to bowel infections.
- Enterobacteria including E. coli, proteus and klebsiella
Examples of Beta-Lactam antibiotics?
Penicillins
Cephalosporins
Carbopenems
How likely is someone to have an allergic reaction to cephalosporins/ carbopenems if they have had a reaction to penicillin?
about 10% chance
What do Beta-Lactam antibiotics act against?
Both gram positive and negative.
so they are considered broad spectrum.
Give examples of penicillins in order of increasing spectrum.
- Penicillin V
- Benzylpenicillin
- Amoxicillin
- Flucloxacillin
- Co-amoxiclav (augmentin - amoxicillin and clavulanic acid)
- Tazocin (pipperacillin/ tazobactem)
What can you use in conjunction with Penicillin to overcome bacterial resistance through B-lacatamase release?
B-lactamase inhibitor
Give examples of Cephalosporins in order of increasing spectrum
- Cefuroxime
- Ceftriaxone
- Cefalexin
How many generations of cephalosporins have been developed? and which are better for gram positive vs gram negative?
4 generations
Earlier classes better for gram positives
Later classes for gram negative
Give examples of Carbapenems in order of increasing spectrum
- Meropenem
- Etrapenem
When are Macrolides used?
When there is penicillin hypersensitivity.
They are broad spectrum but generally less effective than penicillins and so are second line
Give examples of Macrolides in order of increasing spectrum
- Erythromycin
- Clarithromycin
- Clindamycin
Which antibiotics have a high risk of causing c. diff?
Clindamycin = highest risk but others include Meropenem
Give the two most common Quinolones and what they are used for
Ciprofloxacin
- effective against gram negative
- used in gastroenteritis and pyelonephritis
Levofloxacin
- effective against gram positive
- used for chest infections
Give two examples of Tetracyclines and what they are used for
Doxycycline
- most commonly used for atypical chest infections e.g COPD exacerbation
Tetracycline
- used for oral infections
Who can’t you give Tetracyclines to and why?
Children
because it can penetrate into bone and teeth, blackening them
Aminoglycosides are used against what type of bacteria?
Gram negative
Aminogyclosides are given by what route and why?
IV
due to their narrow therapeutic window (nephrotoxic and ototoxic)
Give an example of an Aminoglycoside
Gentamycin
Glycopeptides should never be used with which other class of antibiotic and why?
Aminoglycosides
because they are both nephrotoxic
