Nosocomial Infections Flashcards
What are nosocomial infections?
Healthcare-associated infections (HCAI)
Infections acquired in hospitals or as a result of a healthcare intervention
Why do patients get HCAIs?
Already unwell so more susceptible
Mixing with other unwell individuals with infections so greater opportunity for spread
Antibiotic exposure makes colonisation with antibiotic resistant organisms more likely
Invasive treatments that breach the body’s defences e.g. surgery, catheters, iv lines, ventilation
Treatments that predispose to infection by damaging the immune system e.g. chemo, immunosuppressants
Describe the costs of HCAIs
£1 billion per year in UK; $7 billion in Europe
Extra days spent in hospital meaning 16 million extra bed days in Europe = blocked beds, decreased admissions, increased waiting lists, loss or earnings for the patient
Increased expenditure on drugs, investigations, equipment, etc.
Increased expenditure on staff
Describe the cost of C.diff infection
Length of stay increased by 21 days
Significantly higher death rate
Cost drugs = £47
Cost of investigations = £210
Total cost = £4107
This study was done in 1996 so the current costs are much higher than proposed above
Describe UTIs
Catheter associated as the catheter is a portal for bacteria to ascend the urethra to the bladder
Organisms either come from the patient’s own flora or the hands of staff handling the catheter
May be introduced at the time of insertion (rare) but usually later
All patients with longterm indwelling catheters will develop bacteriuria
Some may develop infection including bacteraemia
How are UTIs normally prevented?
By unidirectional flow of urine and flushing effect
Describe hospital acquired pneumonia (HAP)
Commonly post-operative
Lying in bed post-op with risk of aspiration of bacteria in oro-pharynx
May be unable to cough due to pain
Analgesia may inhibit coughing
May have some lung damage from anaesthetic
Often caused by GI tract organism (gram negatives) but can be difficult to diagnose accurately
Describe ventilator-associated pneumonia (VAP)
Endotracheal tube or tracheostomy tube allows free passage of bacteria into the lung
Bacteria form oro-pharynx or tracheostomy site or from hands or staff touching the equipment
Lying flat (should not be)
Not coughing
Atelectasis - partial collapse or complete inflation of the lung
Describe how surgical site infection (SSI) occurs
Surgery opens up sterile sites with risk of inoculation microbes e.g. joint surgery
Surgery may allow contamination of normally sterile sites with bacterial from sites with normal flora e.g. bowel surgery
Wounds may become infected post-op with pathogens from the patient or from hands of staff or contaminated equipment
Describe how intravenous catheter associated infection is obtained
The skin is a barrier to infection
The line allows direct access to the bloodstream
Can happen with peripheral or central lines
Infection may arise at time of insertion
Infection may develop later from patient’s own bacteria or from hands of staff touching the line
Infection may be at exit site and then extraluminal spread
Infection may develop intraluminally - more common in long term dwelling IV catheters
Infusion may already be contaminated (rare)
What are sharps injuries?
Wound from sharp objects, e.g. needle, scalpel, that exposes the blood to other bodily fluids
Can result in exposure to blood borne viruses such as HBV, HCV and HIV
What does the risk of transmission of sharps injuries depend on?
Type of injury
Viral load of the source patient
Immune status of the recipient
Risk reduction strategies in place
What microbes cause HCAIs?
Some infections result from patient’s own microbial flora - endogenous infection e.g. peritonitis following bowel surgery
Other infections result from microbe acquired from outside source - exogenous infection e.g. HCV following blood transfusion with infected blood or bacteria on hands of staff carried from other patients
A patient’s normal flora may change in hospital
How can a patient’s own flora change in hospital?
Exposure to other organisms
Antibiotics destroy own normal flor and allow colonisation with more resistant organisms e.g. MRSA or antibiotic resistant gram negatives like Pseudomonas aeruginosa
What are common bacteria causing UTIs?
Gram negatives that are often antibiotic resistant
e.g. Pseudomonas aeruginosa, Klebsiella, Enterobacter
What are common bacteria causing HAP?
Strep pneumoniae
Haemophilus influenzae
Gram negatives - Klebsiella, Enterobacter
What are common bacteria causing VAP?
Gram negatives that are often antibiotic resistant
e.g. Pseudomonas aeruginosa, Klebsiella, Enterobacter
What are common bacteria causing surgical site infection?
Depends on site of surgery and pathogensis
GI surgery - gram negatives and anaerobes
Prosthetic joint surgery - coagulase negative staphylococci
Wound infections - Staph aureus (MRSA or MSSA)
Infections from unsterile instruments is rare
What are common bacteria causing IV catheter associated infections?
Coagulase negative staphylococci - usually in central lines
Staph aureus (MSSA and MRSA) - peripheral and central lines often exit site infection
Gram negative bacteria (Pseudomonas aeruginosa, Klebsiella, Enterobacter) - usually in central lines
Describe how multidrug resistant gram negatives can cause infection
Hospital - community transfer to patients, staff and equipment
Colonisation of travellers
Via antibiotics, urinary catheters and hand was sinks
What is the best defence against multidrug resistant gram negatives?
Infection control
What is C. diff the most common cause of?
Antibiotic associated diarrhoea
What is norovirus a common cause of?
Large outbreaks of vomiting and diarrhoea in hospitals and other institutions
How does C. diff cause disease?
Produces toxins that can damage cells lining the inside of intestines
If small number of C. diff organisms in the gut then insufficient toxins to cause damage so large numbers are needed in the gut to cause damage
How does C. diff cause disease for patients with small numbers already in the gut?
Numbers are kept in check by normal flora
If the normal flora are diminished then C. diff numbers can increase - antibiotics can cause this
Antibiotics kill the normal flora as well as disease-causing bacteria
C. diff is resistant to many antibiotics so likely not to be killed along with the others
How is norovirus transmitted?
Faecal oral route
Vomiting - aerosol dissemination
Contaminated environments leading to airborne/oral/mucous membrane spread
What are some other HCAIs?
Tuberculosis
Influenza
Measles
Chickenpox
Legionella
What are some prevention and control measures against HCAIs?
Hand hygiene
Sterilisation and disinfection of instruments and equipment
Disposable single use of items if possible
Safe disposal of sharps
Environmental cleanliness
Ventilation
Water safety
Isolation of infectious or potentially infectious patients
PPE
Good antibiotic control and use (stewardship)
What are some specific measures against HCAIs?
IV line insertion and use
Catheter insertion and care
Prevention of VAP
Prevention of SSIs
What are some other measures that can be taken against HCAIs?
Screening
Surveillance
Mandatory reporting
Where can bacteria and viruses be found?
In immediate patient environment
What can harbour bacteria and viruses?
Vomit
Blood
Urine
Faeces
Bacteria shed on skin scales from patients
What are various levels of cleaning that can prevent transmission of bacteria and viruses?
Deep clean
Use of detergents or disinfectants
Hydrogen peroxide, UV light
What are some important water-borne pathogens?
Legionella
Pseudomonas
How can legionella be controlled?
Correct water temp
Prevention of stagnation (blocked drains/water flow etc.)
Chlorination
UV light
Filters
What is the primary goal of antimicrobial stewardship?
To optimise clinical outcomes while minimising unintended consequences of antimicrobial use including toxicity, selection of pathogenic organisms such as C. diff, and emergence of resistance
What are other interventions that can be done?
Screening and decolonisation of:
- MRSA
- MDR gram negatives
- Identified by swabbing
- Given topical antibiotics to decolonise MRSA
CPE - carbapenam resistant enterbacteriacea
Immunisation of staff - MMR, chickenpox, BCG
What must all trusts report to the Department of Health in England?
MRSA bacteraemias
Glycopeptide-resistant enterococci bacteraemias
C. diff infections
Escherichia coli, Klebsiella, Pseudomonas bacteriaemias
Specific SSIs
