Carbapenem Resitant Enterobacteriaceae Flashcards
Targets of Antibiotics
- cell wall synthesis
- nucleic acid synthesis
- protein synthesis
Main classes of B lactams
- penicillins
- cephalosporins
- carbapenems
- monobactams
2 naturally occuring penicillins
G and V
Structures in cephalosporins
- B lactam ring
- dihydrothiazine ring
For whom are cephalosporins particularly useful?
People who are allergic to penicillin
Generations of Cephalosporins
1 - Cefazolin 2 - Cefoxitin 3 - Ceftriaxone 4 - Cefepime 5 - Cephamycin
Components of augmentin
Amoxicillin and clavulanic acid
3 main clinical carbapenems
- Imipenem
- Meropenem
- Ertapenem
For whom what organisms should carbapenems be used?
- gram neg including ESBL producers
- gram pos cocci including MSSA
- anaerobes
Indications for carbapenems
- intra-abdo sepsis
- pneumonia
- meningitis
- UTI
- skin/soft tissue infections
For what type of organisms is monobactams for?
- aerobic Gram neg (Neisseria, Haemophilus, Pseudomonas)
Last resort drugs
- Colistin
- Tigecycline
Mechanism of action of carbapenems
- B-lactams inhibit cell wall cross-linking by irreversibly binding to PBPs
- destablizes the cell wall leading to lysis
Resistance mechanisms
- decreased permeabiltiy of cell
- enzyme inactivation
- alteration of target site
- active transport out of cell
Action of B-lactamases
- hydrolyse B-lactam ring
- no longer recognized by PBPs
Classes of carbapenemases
A,B,D
Clinical management of enterobacteriaceae infection
- antibiotic therapy
- source control
Infection, prevention and control of enterobacteriaceae infections
- contact precautions
- isolation/ cohorting
How to identify patients at high risk of enterobacteriaceae infections
- antibiotic exposure
- prolonged hospital exposure
- invasive devices
Phenotypic detection of carbapenem resistance
- reduced susceptibility to carbapenems
- phenotypic tests that suggest carbapenemase production
Disadvantages of phenotypic detection of carbapenem resistance
- technically demanding
- long TAT
- not always definitive
Advantages of genotypic detection of carbapenem resistance
- rapid TAT
- definitive results
- high sensitivity and specificity
Methods for bacterial typing
- multilocus variant analysis (MLVA)
- multilocus sequence typing (MLST)
- pulsed-field gel electrophoresis (PFGE)
- whole genome sequencing (WGS)
Describe MLVA
- looks at variations in regions between genes
- PCR amplify a section of loci
- generate genetic fingerprint
- ascertain diversity level
Describe MLST
- genes are sequenced
- sequences compared to database and assigned to a ST
Why is MLST more discriminatory that MLVA?
- indicates SNPs
- variation in house-keeping genes rare
- indicates possible evolution
