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Micro - Important Resistant organisms (ii) (ESBL-Producing gram -ve…
Micro - Important Resistant organisms (ii)
ESBL-Producing gram -ve bacteria
E Coli, K pneumoniae. P mirbalis, E Cloacae (all bowel organisms - enterobacteriaceae - patients may be indefinitely colonised, their normal flora)
common in Mediterranean + East Europe but worldwide
significant cause of morbidity + mortality
on MacConkey
some non-lactose fermenters (P mirabilis)
some lactose fermenters (E Coli, K pneumoniae)
common cause of UTIs (also associated with intra-ab infections + SSIs)
resistance genes encoding ESBLs on plasmids
these plasmids may carry additional resistance genes to aminoglycosides + fluoroquinolones
enzyme hydrolyses the beta-lactam ring (inactivating the drug)
Tx
carbapenems (meropenem)
only on advice from specialist
if patient has severe infection/is critically ill (more favourable outcome + better clearance)
nitrofurantoin in uncomplicated cystitis
aminoglycosides (gentamicin/amikacin) + fluoroquinolones (ciprofloxacin) used if suitable (MIC testing)
Last resort antibiotics
carbapenems
meropenem
for UTIs, meningitis + intrab infections
imipenem
for UTIs + intra-ab infections
not for meningitis CNS toxicity
requires co-admin with cilastatin to prevent renal tubule inactivation
resistant to cleavage by b-lactamases (incl ESBL)
v broad (gram +ve, gram -ve, anaerobes)
resistance emerging :cry:
Colistin
narrow (gram -ve only)
bactericidal - binds to LPS + phospholipids in outer membrane
a few cases of resistance have emerged :cry:
polymyxin
for hosp-acquired infections (e.g. acinetobacter) + lung infections in CF patients
IM/nebulised admin
SEs = neurotoxicity, nephrotoxicity, drug interactions (e.g. with 1GCs)
CPE/CPE
bowel organisms
v similar to ESBLs
produce carbapenemase
resistant to 1st+2nd+3rd gen cephalosporins, aminoglycosides, fluoroquinolones, carbapenems
v limited tx options
consult micro + pharmacy
colistin, tigecycline, fosfomycin
cause healthcare-associated infections (SSIs, BSIs, pneumonia)
Glycopeptide-resistant S Aureus
e.g. VRSA
uncommon, mostly in US
due to transfer of van genes from VRE to MRSA
determine degree of resistance using MIC (some are intermediately susceptible, e.g. VISA + just require a higher dose)
Tx = linezolid
cause BSIs, SSIs, VAP, central line infections
Meningitis Tx
empiric = IV cefotaxime (3GC with good CNS penetration across BB) + vancomycin (covers beta-lactase producers)
don't change until susceptibility results available
if penicillin-suscpeitible switch to IV benzylpenicillin (good CNS penetration + cheap)
S pneumoniae = gram +ve optochin susceptible
N meningitis = gram -ve
infuse patient with vancomycin too quick - red man syndrome