Health Care Associated Infections Flashcards
(39 cards)
What are included in HCAIs?
- Acquired in the health care setting
- Result of interventions, can become apparent after discharged
- Includes infections among staff
What is the difference between prevalence and incidence?
- Prevalence: number that have HCAI at any given time
- Incidence: Risk of acquiring an HCAI within a time period
What kind of risk factors influences HCAI?
• Latrogenic
o Medical interventions cause
o Lack of removal of pathogens (hands)
o Invasive procedures
o Antibiotic use
• Organisational
o Contaminated air conditioning
o Contaminated water
o Contaminated food
o Staffing issues (patient/nurse ratio)
o Physical layout
• Patient
o Illness severity
o Underlying immunocompromised
o Length of stay
What links up to form the chain of infection?
- Pathogen 2. Source 3. Transmission 4. Entry 5. Host
What can be sources of HCAI?
• Humans (staff, visitors, patients)
o Acute disease
o Incubation period
o Colonised/chronic carriers
• Inanimate objects
What can make people at risk of HCAI?
- Underlying medical conditions (compromise immune system)
- Accident trauma
- Surgical procedures
- Anaesthesia
- Invasive devices
- Therapeutic and diagnostic procedures
How can HCAIs be transmitted?
- Direct contact
- Indirect contact
o Surgical instruments
o Needles
o Blood transfusion
o Fomites
o Airborne
• Vehicle transmission
o Contaminated food, water, drugs, bodily fluids, blood
- Vector transmission
- Self
o Endogenous
o Admitted and colonised with hospital strains of bacteria (lots of resistance)
Skin
Respiratory tract (gram – in URT)
GI tract
What are the properties of HCAI pathogens? What are some common ones?
- UTI, surgical wound, LRT, skin, blood
- Often resistant to many antimicrobials
- Often opportunistic
- Viral common
- Antibiotic resistance common and significant
- Examples: staphylococcus aureus/epidermidis, Pseudomonas, Enterobacteria, Clostridium Difficile, Candida, Aspergillum
What are the features of Clostridium difficile? How does it cause illness?
- Antibiotic associated diarrhoea
- Spore forming
- Anaerobic
- Gram Positive Rod
- Shed in faeces
- Spores survive on surfaces (need bleach, need soap and water for hands, resistant to alcohol hand rub)
- Transfer via hands (health workers)
- Broad spectrum antibiotic treatment
o Disruption of normal gut flora, C. difficile overgrowth, mild diarrhoea, pseudo-membranous colitis
• Exotoxins
o A: enterotoxin – fluid production and mucosal damage
o B: cytopathic – ulceration
What can increase the risk of Clostridium diffiile infection? How can it be treated?
- ICU, age, antibiotics, disease, naso-gastric tube, long time in hospital, surgery, antacids, sharing room
- Remove antibiotics, if possible
- Metronidazole (treats anaerobes)
What are the features of Staphylococcus aureus?
- Superbug
- Gram positive cocci
- Facultative anaerobe
- Non motile
- Normal in URT, skin, nose, vagina, intestine
- Adhesins for colonisation
- Produce slime layer/biofilm
- Infection can be serious
How can staphylococcus aureus cause disease? What virulence factors does it have?
- Multiply, spread rapidly – disease
- Survives drying, environment
- Virulence factors
o Exfoliative toxins
o Enterotoxins
o Haemolysins
o Lipases
o Proteases
o DNAses
o Protein A
o Beta-lactamases
• Can cause infection of blood, heart, bone
What are the features of antibiotic resistance in Staphylococcus aureus? Why is it such an issue?
- Penicillin
- Methicillin (MSRA)
o Hard to treat
o Poor outcome
o Use vancomycin
- Macrolides, tetracycline, quinolones
- Colonises many people (25-50%)
- Can escalate to severe illness
What are the features of enterococci? Which types can cause HCAI?
- Gram positive cocci
- Commensal, in GI tract
- Can infect abdomen, urinary tract, blood (septicaemia)
- HCAI infections: E. faecium
- HCAI infections: E. faecalis
Why is E. faecium hard to treat? How can VREs be spread?
- Hard to treat, lots of antimicrobial resistance
- Intrinsic resistance
o Penicillin
o Cephalosporin
o Aminoglycosides
• Acquired resistance
o Glycopeptides/vancomycin
- Survive well in environment
- VRE Spread
o Faecal contamination
o Equipment
o Oral
o Hand contamination
o Fomites (handles, sinks, toilets, bed rails, surfaces)
What is phylogenetics? How can it be used with HCAI?
- Infer phylogeny from set of taxa
- Shows evolutionary relationships
- In HCAI:
o Link to possible sources of infection
o Show evolution of new traits
o Show population dynamics
What are the features of VRE? What are VSE and what relationship do they have with VRE?
- First isolate, UK, 1986
- Austin health 1994
- Lead to outbreaks or colonisation (important if immunocompromised)
- VSE = vancomycin sensitive enterococci
- VSE can become VRE
o Acquire transposon with vancomycin resistant vanA/B locus (TN1549, 7 genes)
What does vanB encode?
• enzyme/ligase that modifies bacterial peptidoglycan cell wall so vancomycin can’t bind
What is the size of the VSE chromosome and vanB transposon?
- VSE chromosome: 3000kbp
- vanB transposon: 30kbp
How might VRE be transmitted according to transmission model A?
• Patient arrives with VRE, spreads to surrounding environment
How might VRE be controlled under transmission model A?
- Screen patients for VRE on arrival
- Isolate carriers to single rooms
- Ensure good hand hygiene, protective clothing, cleaning
- Expect eventual elimination of VRE from hospital
What effect did hand hygiene have on Austin Health?
- MRSA decrease, but VRE increase (model A not only one)
- vanB in many anaerobic gut commensals
- Make your own VRE from the commensals
How does the alternative transmission model explain vanB VRE epidemiology?
- Transfer vancomycin resistant genes to VSE from anaerobic bacteria in bowel flora when patient is exposed to vancomycin
- Lateral gene transfer (vanB to VSE)
- Environment contaminated
- Lots of patients will carry VSE in bowel flora initial
- VRE can emerge from de novo mutation when patient treated with broad spectrum antibiotics which select for HGT from bowel anaerobes to VSE
What is aseptic technique?
• Specific practices and procedures performed under carefully controlled conditions with goal of minimising transfer of and contamination by potential pathogens
