Hospital infections Flashcards
What does antimicrobial mean?
Interferes with growth and reproduction of a microbe
What does antibacterial mean?
Commonly used to describe agent to reduce or eliminate harmful bacteria
What does antibiotic mean?
Type of microbial used as medicine for humans, animals and are originally developed from naturally occurring compounds
What are hospital associated infections (HAI)?
Infections that occur after exposure to healthcare, starting >48 hours after admission to hospital
What are the most frequent types of HAI?
Surgical site infections, urinary tract infections, pneumonia, bloodstream infections and gastrointestinal infections
What is the burden of HAIs?
Infection results in a large increase in length of stay in hospital and poses an extra cost of 1 billion pounds to the NHS every year
What are the sources of infection in hospital?
Intervention: Lines, chemotherapy, catheterisation, prophylactic or inappropriate prescription of antibiotics, intubation and prosthetic material
Dissemination via hospital staff
Concentration- high density of infection and patients within a hospital
What are the ESCAPE pathogens?
The major problems in hospital infections (first 3 gram+, last 3 gram -):
Enterococcus faecium (vancomycin resistance)
Staphylococcus aureus (MRSA)
Clostridium difficile
Acinetobacter baumanii (highly drug resistant)
Pseudomonas aeruginosa (multi-drug resistant
Enterobacteriaceae
What is the major problem that leads to hospital infection?
Clinicians are forced to use older, previously discarded drugs such as colistin that are associated with significant toxicity and for which there is a lack of robust data to guide selection of dosage regimen or duration of therapy
What is pathogenic e.coli the most frequent cause of?
Bacteraemia by a gram negative bacterium
Community and hospital acquired UTI
What is happening to E.coli resistant strains?
There is an increase in multi-drug resistant strains. Occurrence of resistance to 3rd generation cephalosporins as high as 20% in some countries
What do most isolates that are resistant to cephalosporin express?
Extended spectrum beta lactamase (ESBL)
How responsive are isolates that are resistant to cephalosporin to carbapenems?
They are still sensitive
What are cephalosporins?
They are a class of b-lactam antibiotic. They inhibit peptidoglycan synthesis by inhibiting the activity of penicillin binding proteins
What does the extended spectrum b-lactamase on resistant bacteria do?
They are encoded on a mobile plasmid and it cleaves the cephalosporin
What are carbapenems?
Class of b-lactam antibiotic that inhibits peptidoglycan synthesis by inhibiting the activity of penicillin binding proteins
What does the carbapenemase enzyme on resistant bacteria do?
It is encoded on a transposon mobile genetic element and it cleaves the antibiotic
What is klebsiella an important cause of?
UTI and respiratory tract infections
What is the risk group of klebsiella?
Immunocompromised
What is there a high proportion of resistant to in Klebsiella?
There is resistance to 3rd generation cephalosporins, fluroquinolones and aminoglycosides
Which species of CRE is most commonly encountered in US?
Carbapenem resistant Klebsiella pneumoniae
What is the risk group for pseudomonas aeruginosa?
Immunocompromised (high proportions of strains are resistant to antimicrobials)
What is the most important cause of antimicrobial resistant infection worldwide?
Methicillin resistant s. aureus
What sort of antibiotic is methicillin?
B-lactam antibiotic that inhibits peptidoglycan synthesis by inhibiting activity of penicillin binding proteins
How is resistance to methicillin achieved by staph aureus?
Expression of additional penicillin binding protein (PBP2A)- has a low affinity for methicillin and thus can still function in the presence of antibiotic. MRSA can still survive and synthesise peptidoglycan
What is vancomycin resistant enterococcus faecium the third most frequently identified cause of in the US?
Nosocomial bloodstream infections
What is vancomycin resistance like in VRE?
60%
What does vancomycin do?
Inhibits peptidoglycan synthesis by binding to precursor protein
How is resistance to vancomycin achieved in VRE?
Encoding multiple protein genes on plasmid/transposon. Results in synthesis of a different peptidoglycan precursor which isn’t functional
What is clostridium difficile?
A spore forming gram-positive bacterium which is a frequent complication following antibiotic therapy. However infections are now emerging in community and animals used for food
When are patient resistant to CDI?
Their normal gut flora is not disrupted by antibiotics
Why do people become vulnerable when antibiotic treatment starts to CDI?
Infection with a C. difficile strain that is resistant to antibiotic is more likely and when the treatment stops, levels of antibiotic in gut diminish rapidly but microflora remains disturbed for a variable period of time depending on antibiotic given. During this time patients can be infected with c. difficile. Finally after microflora recovers, colonisation resistance to C difficile is restored
What is the pathogenesis of C.difficile?
C.difficile colonises the intestine after disruption of normal intestinal flora. Toxigenic strains of the bacteria then produce toxin A and B. Toxin B binds to epithelial cell membrane and then toxin A causes cytoskeletal changes that result in disruption of tight junctions and loosening of the epithelial barrier in cell death and in the production of inflammatory mediators that attract neutrophils
Both toxins are cytotoxic and induce the release of various immunomodulatory mediators from epithelial cells, phagocytes and mast cells, resulting in inflammation and accusation of neutrophils
