Lecture 23 - Health Care Associated Infection Flashcards
What are some common places where these infections can be gotten?
Nursing home
Hospital
Child care centre
What is another word for HCAI?
Nosocomial
What is a nosocomial infection?
Infection from a health care associated setting
May have delayed onset
We don’t count infections that are already present when first entering the setting
How many deaths are there each year due to HCAI?
7000 in Australia annually
How much do HCAI cost Australia each year?
180 millions
How many people at any one time in a health care setting have an infection?
3-25%
How can infection rates be stemmed?
Implementation of infection control programmes
1/3rd
What are infections that result from a medical intervention?
Give some examples
Iatrogenic
• The bacteria get a ‘free ride’ into the body, past protective defences
For example: • urine catheterisation • hands of medical personnel • intubation • ventilation • IVs (indwelling vascular lines)
What do invasive procedures sometimes cause?
Iatrogenic infections
How are iatrogenic infections treated?
Antibiotics
Can also be used for prophylaxis
What can antibiotic use in the hospital lead to?
- Resistance
* Antimicrobial associated diarrhoea
What are organisational associated factors?
Name some examples
To do with the way that the hospital is organised For example: • air conditioning • contaminated water systems • staffing issues • physical layout of facility
Which organisms are commonly in the water system?
Are these a problem?
- Pseudomonas aeruginosa
- Serratia
For healthy people, it doesn’t cause disease
People with burns are, however at risk
Which organisms are present in contaminated in the air?
• Aspergillus mould
Which organisms are present in contaminated food?
- Salmonella
* Campylobacter
Describe the links in the chain of infection
Pathogen Source Transmission Entry Host
What are patient associated factors?
- Severity of illness
- Underlying immunocompromisation
- Length of stay
What are some common sources of infection?
People: • other patients • staff • visitors • own normal flora Environmental
Describe how other patients often spread disease
• acute disease
- person still in incubation period
- chronic carriers excreting
- person’s own endogenous flora
- fomites contaminated with others’ bacteria
Why is anaesthesia a predisposing factor for infection?
How can this be prevented?
Because the cilia are immobile
It is important to get the patient moving and coughing to get the cilia working again
What factors predispose someone to infection?
- Trauma (arm out window –> bacteria from road)
- underlying immunosupression (age, disease)
- co-morbidity (smoking, influenza)
- procedures (anaesthesia)
What are someways that the pathogen is transmitted?
Direct: person to person
Indirect: surgical instruments, fomites
Airborne: droplets
Vehicle: food, water, drugs, blood transfusion
Vector: mosquitoes, flies, rats
What are patients colonised with soon after admittance to hospital?
Describe the common locations and pathogens
Hospital strains of bacteria
These tend to be more resistant
Colonisation of:
• skin
• GIT; VRE
• respiratory tract; Klebsiella
Which hospital strains colonise the GIT?
VRE
Which hospital strains colonise the respiratory tract?
Klebsiella
Which outbreaks are commonly seen in children’s wards?
When?
How is it spread?
1\ Rotavirus outbreaks
In winter
Person to person
2\ Varicella Zoster
Spread by aerosols
What other pathogens often cause outbreaks in hospital?
1\ Norovirus
Aerosols, surfaces
2\Influenza
Aerosol spread
Which infections are most common?
Which are serious?
- UTI 30-45%
- Surgical wound 15-30%
- LRT 10-25%
- Skin 5-10%
- Blood 5-10%
Serious:
septicaemia, burn infection, LRT infection
Not so serious:
UTI
Surgical wound
Which bacteria commonly cause infection in hospitals?
- Staph. aureus
- Staph. epidermidis
- Pseudomonas aeruginosa
- Enterobacteria (Klebsiella, E. coli)
- Acinetobacter
• Clostridium difficile
Which yeast is commonly seen in hospital infection?
Why is it often seen in hospitals?
• Candida albicans
Overgrowth due to antibiotics use
The antibiotics clear the bacteria, giving the yeast a chance to grow
Describe the main features of C. difficile
Spore forming
Gram positive rod
Anaerobic
Which mould is commonly seen in hospital infections?
• Aspergillus
How is C. difficile transmitted?
- Shed from infected people
- Spores survive on surfaces
- Hands of health care workers transmit the spores to patients
How can we kill spores and remove them from surfaces?
How about from hands?
• Bleach
(Resistant to normal methods)
• soap and water
(alcohol gel not enough)
What predisposes someone to C. difficile infection?
- Broad spectrum Antibiotics –> disruption of normal flora
- prolonged hospital stay
- antacid use
- sharing room with infected person
- NG tube
What does infection of C. difficile result in?
Ranges from:
• Mild diarrhoea
• Pseudo-membranous colitis (sometimes fatal)
What are the symptoms of C. difficile infection?
- Cramping abdominal pain
* Watery diarrhoea (can be bloody)
How do we treat C. difficile infection?
• Removal of antibiotics
Metronidazole
What is the hypervirulent strain of C. difficile?
- High rates of nosocomial infection
* Increased production of toxin
What is the superbug?
Why is it so called?
Staphylococcus aureus
Because it causes wound infections, food poisoning and is quite extensively resistant to antibiotics
How does C. difficile cause damage?
2 exotoxins:
- Toxin A- enterotoxin – fluid production, mucosal damage
- Toxin B- extremely cytopathic – ulceration
Describe the features of S. aureus
Where does it colonise?
Gram positive cocci
Facultative anaerobe
Colonises: • URT • nose • skin • vagina • intestine
How does S. aureus colonise?
Adhesins
What are the virulence factors of S. aureus?
- Exfoliative toxins
- Enterotoxins
- Haemolysins
- Lipases
- Proteases
- DNAases
- Leukocidins
- Protein A
- Beta lactamase
Discuss antibiotic resistance with S. Aureus
This is a big problem because so many people are infected.
1/ Penicillin resistance quickly
- has beta lactamase
2/ MRSA
3/ Starting to see vancomycin resistance
Is S. aureus hardy?
Why?
Yes, survives well in the environment
Able to form biofilms
Where does S. aureus cause disease?
- Endocarditis
- Osteomyelitis
Many, many more
Describe the genome of S. aureus
Core genome
Accessory Genome
Plasmids
Pathogenicity island:
• enterotoxins
• superantigens
Describe the features of enterococci
Where does it colonise?
Gram positive cocci
Commensal in gastrointestinal tract
What is VRE?
How did it come about?
Vancomycin resistance enterococci
Years of vancomycin use in hospitals
Describe resistance of enterococci
Multiple antibiotic resistance: • penicillins • cephalosporins • aminoglycosides • vancomycin --> VRE
What infection is associated with bone marrow transplants?
Aspergillus mould
What is MRSA?
How is it overcome?
Methicillin resistant S. aureus
Big problem for HCAI
MRSA now treated with vancomycin
What is MRSA?
How is it overcome?
Methicillin resistant S. aureus
Now use Vancomycin
Which enterococci cause nosocomial infection?
E. faecium
E. faecalis
What sort of infections are caused by enterococci?
- Abdominal infections
- Urinary tract infection
- Septicaemia
What are glycopeptides?
Antibiotics
eg. Vancomycin
Give an example of transmission via a vehicle
- Blood transfusion
- Food
- Water
Why are people of poor health more susceptible to Klebsiella?
In respiratory tract
Poor health:
• decreased fibronectin in RT
• predisposition to Klebsiella colonisation
What is the most important feature of Clostridium difficile for its transmission?
Spore formation
Describe how broad spectrum antibiotics predisposes someone to C. difficile infection
- BS antibiotics kill many bacteria in the GIT
- C. difficile now has the opportunity to overgrow
- Toxin production
- Mild diarrhoea / P.M.C.
What is haematogenous spread?
Spread via circulating blood
What is osteomyelitis?
Infection & inflammation of the bone or bone marrow
Why should we worry about S. aureus antibiotic resistance?
Because bacteraemia due to S. aureus is common in Australia.
This is a serious infection.
