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what is augmentin?
- amoxycillin trihydrate (B lactam antibiotic) -
- potassium clavulanate (B lactamase inhibitor)
- -> abx w inc spectrum of action and restored efficacy against amocxicillin-resistant bacteria that produce B-lactamase
how do b-lactam antibiotics work?
- attack cell walls of bacteria (inhibit the synthesis of the peptidoglycan layer of bacterial cell walls). - bacteria develop resistance by synthesizing beta-lactamase (attacks b-lactam ring)
- used in prophylaxis and rx of bacterial infections caused by susceptible organisms.
- mainly active against gram-positive bacteria.
- broad spectrum b-lactam abx is active against various gram-neg organisms.
what are some common b-lactam abx?
- penicillins: flucloxacillin (narrow s), amoxicillin/ampicillin (mod s), co-amoxiclav (broad s)
- cephalosporins: cephalexin(mod s), cefaclor (mod s), ceftriaxone (broad spectrum)
- carbapenems and penems: imipenem
- monobactams: nocardicin
- b-lactamase inhibitors: clavulanic acid
what colour do gram-positive bacteria stain?
- stained dark blue or violet by gram staining - able to retain crystal violet stain bcoz of high amount of peptidoglycan in the cell wall.
- gram-pos cell walls typically lack outer membrane of gram-neg bacteria.
what is the structure of gram positive bacteria?
- cytoplasmic lipid membrane
- thick peptidoglycan layer
- capsule polysaccarides (only in some species)
- flagellum (only in some species)
what is the hierarchy of gram positive bacteria?
- gram positive:
- non spores = corynebacterium, listeria,
- spore-forming = clostridium- obligate anaerobe, bacillus - facultative anaerobe
- staphy (catalase +)
- -S. aureus (coagulase +)
- - (coag -) S. epidermis, S. saprophyticus
- strep (catalase -)
- - b-haemolytic (clear) - pyogenes or agalactiae
- - y-haemolytic - enterococcus, E. faecalis, E. faecium
- - a-haemolytic (green) - pneumonia, viridans mutans, sanguis
what is rifampicin used for?
- treats mycobacterium infections incl. tb and leprosy
- used for tb for 6-12/12 w isoniazid, ethambutol, pyrazinamide
- stop etham and pyra after 2/12
- also used for
- rx of MRSA w fusidic acid
- prophylactically for neisseria meningitidis
- listeria species, neisseria gonor, haem inf, legion. pneumophilia (test sensitivity 1st)
- enterobacteriaceae, acinetobacter and pseudomonas resistant
what is amoxycillin?
- mod. spectrum bacteriolytic
- b-lactam penicillin (mainly gram pos, a little gram neg)
- better absorbed following oral adminnthan other b-lactams
- rx for cystic acne
- s/e (as for other b-lactams):
- n and v, rashes, abx assoc colitis, diarrhea
what is penicillin?
- derived from penicillium fungi
- 1st drugs effective against syph and staph
- many bacteria are now resistant
- all pens are b-lactams - used usually for gram-pos
what are gram neg bacteria?
and what is their heirarchy?
- counterstains red (safranin)
- have lipopolysaccharide outer membrane
- gram neg
- B. pertussis
- F. tularensis
- P. multocida
- L. pneumophila
- cocci: neisseria
- N. meningitidis
- N. gonorrhoeae
- lactose + = klebsiella, e.coli, enterobacter
- lactose - =
- -oxidase + (V. cholerae, P.aeruginosa),
- -oxidase - (P. mirabilis, H. Plori, S dysenteriae, Salmonella, Y. pestis, Y. enterolitica)
- -strict anaerobe (B fragilis)