Hospital Acquired Infection Flashcards
Define antimicrobial & antibacterial
Antimicrobial
• Inteferes with growth & reproduction of a ‘microbe’
Antibacterial
• Commonly used to describe agents to reduce or eliminate harmful bacteria
• ABs are a type of antimicrobial
Causes of HAIs?
(1) Interventions
• catheters, intubation, chemotherapy, prosthetics, lines, prophylactic, ABs, inappropriate prescribing
(2) Dissemination
• carriers of the infection from person to person
(3) Concentration
Mnemonic for the main pathogens that are an issue?
Used to be ESKAPE
BUT NOW
ESCAPE
What are the ‘ESCAPE’ pathogens?
o Enterococcus faecium. E F
• +ve
• Vancomycin resistant
o Staph. aureus. S A
• +ve
• MRSA
o Clostridium difficile. C D
• +ve
• Can infect due to previous AB treatment
o Acinetobacter baumanii A B
• -ve
• Highly drug resistant
o Pseudomonas aeruginosa. P A
• -ve
• MDR
o Enterobacteriaceae. E (E)
• -ve
• MDR – all the sub-types.
Pathogenic e coli, Klebsiella pneumoniae, Enterobacter species
Facts about pathogenic E-coli?
Most frequent cause of bacteraemia by gram -VE
• most frequent cause of community & HAI UTIs
How does resistance arise in E-coli?
Increase in MDR-strains of E-coli
Resistances include
• 3rdGen CEPHALOSPORIN resistance - most resistance mediated by the ESBLs
• Still sensitive to CARBAPENEMS
What are Cephalosporins & Carbapenems?
Class of BETA-LACTAM ABs
Target Pathway:
• Inhibit Peptidoglycan synthesis
Target Protein:
• Inhibit the activity of penicillin binding proteins (PBPs)
How does resistance to Cephalosporins arise?
Extended spectrum BETA-lactamase (ESBL)
• encoded on a plasmid
• mobile
• ESBL enzyme cleaves cephalosporin
How does resistance to Carbapenems arise?
Carbapenemase enzyme
• encoded on a tranposon
• mobile genetic element
• enzyme cleaves carbapenem
Klebsiella Pneumoniae:
Causes
Risk groups
Resistances
Causes:
• UTIs
• Respiratory tract infection
Risk groups:
• immunocompromised
Resistances:
• 3rdGen Cephalosporin, fluoroquinolones & aminoglycosides
• CRKP (carbapenem-resistant KP) - species of CRE most commonly encountered in US
(used to part of ‘ESKAPE’)
Pseudomonas Aeruginosa:
Risk group
Resistance
Risk group:
• immunocompromised
Resistances:
• high proportions of strains are resistant to several antimicrobials
• Carbapenem resistance is above 10% in half EU countries
What is MRSA and why so dangerous?
Methicillin resistance S.aureus
• most important cause of antimicrobial resistant infection worldwide
It expresses and additional penicillin binding protein (PBP2A)
• this has a LOW AFFINITY for methicillin and can therefore function
• MRSA strains can therefore still synthesise peptidoglycans
What is methicillin?
Class of BETA-LACTAM ABs
Target Pathway:
• Inhibit Peptidoglycan synthesis
Target Protein:
• Inhibit the activity of penicillin binding proteins (PBPs)
How does resistance to methicillin arise?
Expression of additional penicillin binding protein
• PBP2A
(look at MRSA dangerous reason for rest!)
What is VRE and why is it dangerous?
Vancomycin resistance Enterococcus faecium
• 3rd most identifies cause of nosocomial blood stream infections (BSI)
Resistance to Vancomycin
