ddt 16 Flashcards
an antibiotic that hasn’t been used in clinics beadier but belonging to class of antibiotics
new antibiotics
an antibiotics w mechanism of action never used against bacteria
novel antibiotics
infections are mostly associated w
invasive medical devices and surgical procedures
S.aureus produces
4 enzymes ( peniclin binding proteins PBP ) for cell wall biosynthesis
PBP 1-4 can be modified by
b-lactam antibiotics leading to their inhibition and bacterial death
MRSA produced —- which is not inhibited by— and can produce all functions of —-
- altered PBP. (PBP2a)
- b- lactam
- all 4 PBP of S aueures.
the production of altered PBP is considered to be
recent resistance mechanism in gram +ve compared to the b-lactamase is ancient evolutionary
Treatment of infection caused by MRSA
- antibiotics other than penicillin/ b- lactam
( almost 50% of mrsa strains r resistant to all but few antibiotics ) - vancomycin destroys mrsa and resistant bacteria
( first case was VRSA and there are 52 VRSA strains )
novel antibiotics for mrsa treatments
- linezoid ( oxazolidinone )
- synercid ( combination of streptograms, quinupristin, dalfopristin )
- daptomycin ( lipopeptide )
linezolid is a
oxazolidinone class of antibiotics
linezoilds works for —- by inhibiting —- in only gram — bacteria
mrsa and VRE , inhibition of protein synthesis , gram +ve only
intravenous treatment caused by VRE, staph. aureus, and strep. pyogen
Synercid by inhibiting protein synthesis both agents at same place in the ribosome
—– when administered individually and —- when in combination
bacteriostatic, synerically and becomes bactericidal
intravenous treatment of gram +ve infections by binding to cell membrane and causes depolarisation
daptomycin ( cubcin )
- it interrupts protein, dna and rna sythesis
- slow emerges of resistance in clinic
patient being hostiblized for prolonged period of times and receiving multible course of antibiotics results in
antibiotic resistance
enterococcus faecalis and enterococcus fascium are
more difficult to treat and higher incidence of resistance against vancomycin ( 15-20% of isolates )
32 before emerges requires — genes mutation for resistance against vancomycin but 2-3 years against penicillin requires — mutation
5 genes , 1 gene
vancomycin works by
inhibiting the cell wall beiosystheis and block the substrate while peciline blocks the enzyme
is a glycopeptide antibiotic
vancomycin
bacteria becomes resistant when
- loss of a single hydrogen bond = 1,000 folds drop in drug binding affinity ( from D-Ala to D- Lac )
Clostridium difficile associated diseases ( CDAD)
- gram +ve
- requires anaerobic bacterium
- spores forming
- toxigenic strains: toxins A + B causes extensive damage to colonic mucosa
—- causes major nosocomial diarrhoea
CDAD
more than — produced — and — antibiotic treatment
90% after and during
treatments of CDAD includes
1- medical therapy includes discontinuation of inciting antibiotic if possible
2- specific antibiotic treatment if persisent diarrhoea:
- metrazodiale at first line antibtioc agent
- vancomycin as alternate agent for 2nd line therapy
- both are taken orally
20-25% of the patients will get — of the symptoms once ——
recurrence, vancomycin. metronidazole withdrawal
metronidazole is a
nitroaryl compound and exact mechanism is unknwon,
how is the prodrug metronidazole is activated
activated by anaerobic organisms by reduction of nitro group to hydroxylamine group. During reduction it can damage bacterial cell components dna protein and mebrance
the advantages of metronidazole as a first line therapy
- reserves vancomycin for MRSA
- prevent selection if VRE
when is vancomycin is used instead of metronidazole
- failure to reposed to metronidazole after 3-5 days
- pregnancy , lactation
- intolerance to metronidazole
- critically ill patients
- metronidazole- resistant infecting organisms
gram — is responsible for — of HAI
gram -ve , 30%
gram — is responsible for — ICU ( intensive care unit)
gram -ve , 70%
the main HAI caused by gram -ve
- pneuminia: associated w mechanical ventilations
- bloodstream infections: associated mostly from central vascular catheter and initial infections in the lungs, abdomen, and genitourinary tract
- Urianry tract infections (UTI): associated mostly from urtheral cathetrization increased risk from 5-10%
best management is to remove the catheter instead of antibiotic treatment
many strains of gram -ve bacteria causing HAI are
-multi-drug resistant ( MDR , resist at least 3 different antibiotic classes )
- can have more than 1 resistance mechanism
- requires the use of older antibiotic not used before bc toxicity issues lead to polymyxin
some organisms resist all currently available antibiotic called
XDR : extreme drug resistance , including polymyxin ( acintobacter baemanni )
the antibiotic carbapenems resistance is
carbapanese
—- can inactivate all type of b lactam antibiotics and are not inhibited by inhibitors of b- lactamasse aka clavulenic acid which is a clinical challenge
carbapebenases
treatment of HAI caused by gram -ve drug resistant
- gram -ve expressing ESBLS ( extended spectrum b- lactamase) : carbapene as meropenum
- gram -ve expressibg carbapenemse : colistrin , trigcylin
is a carbapenum b lactam antibiotic
meropenum
meropenum structure similar to —-
penicillin
- bicyclic structure , 1 b lactam ring , 5 membered ring
- sulphur is not part of the 5-membered ring , its attached to a ring of functional side chain
- carbon- carbon double bond in the 5-membered ring
colistin ( polymyxin E)
- peptide antibiotic
-polymyxin antibiotic - mixture of 2 cyclic peptide ( colistin A and b) produced by the fermentation of bacillus polymyxa
- clinical use is perviously limited bc of nephrotoxity
- reserved as last resort antibiotic of MDR gram -ve bacteria
- binds to phosphate group in lipid on the cell cytoplasmic membrane and disturbs its integrity
reserved as last resort antibiotic of MDR gram -ve bacteria
colistin
tigecycline is
novel tetracycline class: glycylclines
characterised by additioal glyclyamido substients
tigecyclin and it inhitbis bacteria protein sythesis and is broad spectrum antibiotic
all novel antibiotics are effective against gram +ve but not -ve bc
gram -ve outer membrane is the main barrier
number of novel classes of antibiotics for gram -ve bacteria under development
NONE LOL
