Antibiotics Flashcards
Bactericidal meaning
Kills bacteria
Bacteriostatic meaning
Prevents bacterial growth
What do antibiotics work on?
The bacterial cell wall, the bacterial DNA and the bacterial ribosome
What antibiotics work on the cell wall?
Penicillins, cephalosporins and glycopeptides
Name the penicillins
Penicillin, flucloxacillin, amoxicillin, temocillin, co-amoxiclav and piperacillin
Name a cephalosporin
Ceftriaxone
Name 2 glycopeptides
Vancomycin, Teicoplanin
What are the majority of gram positive cell walls made of?
Peptidoglycan
How do the penicillins work?
Inhibit cell wall synthesis by preventing cross linking of the peptidoglycan subunits
How are penicillins excreted
By the kidneys, rapidly
What are the 3 forms of penicillin?
Benzylpenicillin (penicillin G), Phenoxymethyl penicillin (penicillin V), Benzathine penicillin
Tell me more about Benzylpenicillin (penicillin G)
Original form, narrow spectrum, can be destroyed by stomach acid, still useful against anaerobes
Tell me more about Phenoxymethyl penicillin (penicillin V)
Newer, resistant to stomach acid
Tell me more about Benzathine penicillin
Long acting, IM
Tell me about flucloxacillin
Gram positive, very narrow spectrum, staph and strep, IV or oral
What is fluclox ineffective against?
MRSA
Tell me about amoxicillin
Gram positive and negative, IV or oral, broad spectrum
Amoxicillin can be used along side clarithromycin to treat what?
H pylori stomach ulcers
Tell me about Co - amoxiclav
IV or oral, gram positive and negative, very broad spectrum
Tell me about Tazocin/ Piperacillin
Huge spectrum, nearly all, not MRSA
Tell me about Temocillin
Gram negative, only active against coliforms, E. Coli
Active against extended spectrum beta lactamase producing organisms
Tell me about the cephalosporins
Broad spectrum, excreted via kidneys, kill off normal flora and can lead to C dif - limited use
How do cephalosporins act on the bacterial cell wall?
They disrupt the synthesis of the peptidoglycan layer of bacterial cells walls, which causes the wall to break down
Tell me about the glycopeptides
Excreted via the kidneys, active against gram positive cocci.
Name a glycopeptide
Vancomycin
How do glycopeptides work
They bind to the end of the growing pentapeptide chain during peptidoglycan synthesis. Preventing cross linking and weakening the bacterial cell wall
What antibiotics inhibit protein synthesis - act on the bacterial ribosome
Macrolides, tetracyclines, aminoglycosides, clindamycin and chloramphenicol
Name the macrolides
Erythromycin, Clarythromycin, azithromycin - bacteriostatic
Name a tetracyclines
Doxycycline - bacteriostatic
Name an amino glycoside and tell me about it
Gentamicin - binding to the ribosome is lethal - not absorbed from the gut, acts mainly against gram negative aerobic organisms - excreted via kidneys
Tell me about macrolides
Excreted via liver, lipophilic (can pass through cell membranes easily)
Tell me about aminoglycosides
Bactericidal, active against gram negative aerobic organisms (coliforms and pseudomonas)
Excreted via kidneys
Can damage kidneys and CN 8 (deafness and dizziness)
What antibiotics act on bacterial DNA
Metronidazole, Trimethoprim, Fluoroquinolones
Tell me about metronidazole
Oral or IV, causes bacterial DNA strand breakage, used to treat anaerobic and some protozoal infections
Tell me about Trimethoprim
Oral, inhibits bacterial folic acid synthesis
Can be given with sulphamethoxazole as co-trimoxazole (Septrin)
Used against some gram positive and gram negative
Excreted via kidneys
What are the fluoroquinolones and tell me about them
Ciprofloxacin (IV or oral) Levofloxacin (IV)
They are bactericidal
Restricted use in Tayside –> C dif
Excreted in urine
What are the side effects of antibiotics?
Nausea, vomiting, diarrhoea
Many affect the absorption of oral contraceptives
Ciprofloxacin –> Tendonitis
Metronidazole - interacts with alcohol
What antibiotics are avoided?
Cephalosporins, Co - amoxiclav, ciprofloxacin, clindamycin
What organisms are Gram positive
Clostridium Spp, Streptococus Sp, Enterococcus spp, Staph aureus, MRSA
What organisms are gram negative?
Bacteroides Spp, Haemophilus Influenzae, Neisseria spp, E coli (coliforms)
How do we classify strep
Haemolysis
Alpha - partial
Beta - complete
Gamma - none
What does strep pnuemoniae cause?
Pneumonia and meningitis
What does strep viridians cause?
Endocarditis
Beta strep - group A strep causes what?
Tonsilitis, scarlet fever, necrotising fasciitis
Non haemolytic strep is what?
Enterococci
What test is used to distinguish between staph
Coagulase test
In infection what happens to the blood volume?
It decreases as more fluid leaks into the tissues, the heart then has to work harder
What is released from gram negative bacterial cell walls when they die?
Lipopolysaccharides
What is the first line antibiotic for anaerobic infections
Metronidazole
Describe Spirochaetes
Spiral shaped, dont stain
What are the mechanisms of bacterial resistance
Production of enzymes to destroy the antibiotics
Altered antibiotic binding sites
Alteration of cell wall porins
Up regulation of efflux pumps (antibiotic being removed from the cell before it has time to act)
Exotoxin is mainly produced by what?
Gram positive organisms
Endotoxin is mainly produced by what?
Gram negatives
What structure does candida have?
Large gram positive oval structures
What is the most common cause of gastroenteritis in infants?
Rotavirus
What are the coliforms?
E.Coli, Klebsiella, enterobacter, proteus
Staph, strep, entero and MRSA are sensitive to what?
Vancomycin
