11.1: Hospital acquired infections Flashcards
Define a hospital acquired infection
Infection occurring in a patient during process of care in a health care facility which wasn’t present/incubating at the time of admission
Name three other terms used for hospital acquired infections
Nosocomial, iatrogenic, health care associated infections (HCAI)
What is the most common mode of acquisition for HCAIs?
Endogenous/self-infection (50%): the infectious agent is present at the time of admission but signs of infection occur during stay in the hospital
Define an exogenous acquisition of HCAIs, what sources can they be from?
Patient contracts new infective agents in the hospital and develops symptoms of infection (i.e another patient, hospital worker 35%, instruments 10%, air 5%)
Why is it important to differentiate between sources of HCAI?
To understand the epidemiology and for prevention
Define direct and indirect contact spread
Direct: person to person (i.e touching, contact with oral secretions or body lesions)
Indirect: via contaminated hands or equipment
Name five common HCAIs from most-least common
- Respiratory infections: Pneumonia (i/e Ventilator associated (VAP)) and hospital acquired pneumonia (HAP)
- UTIs
- surgical site infections (SSIs)
- GI infections
- Bloodstream infections (BSI)
What are the three most common bacteria pathogens causing HCAIs and two on the rise?
What are prevalent HCAI conditions that can be caused by viruses?
Coagulase negative staphylococci, Staph aureus, enterococci
Although with the rise of broad spectrum antibiotics incidents of infections caused by MRSA and ESBLs have increased
Flu, norovirus
What are (ESBLs) extended spectrum beta lactamase producers?
Resistant to beta lactames (a class of antibiotics)
What is the impact of HCAIs?
- Patient safety (i.e long-term disability)
- Can take antibiotic resistant bugs out of hospital
- Ward closures and bed blockages - health service disruption
- High mortality especially in frail and elderly
- Economic impact - 1 million NHS/year
How do you differentiate between hospital and community acquired pneumonia, and why is it important to make the differentiation? How does an HAP present and how are they diagnosed?
If the infection presents >48 hours of being admitted it is hospital acquired, but if it presents <48 hours it is community acquired.
Important to differentiate as there are different pathogens associated with each that will affect treatment/antibiotic choices
How is HAP diagnosed and what signs might be seen? What is important to know when managing a patient with an HAP?
Diagnosed primarily by blood culture, symptoms and infiltrations on CXR may be observed
In HAP: want to know their previous antibiotic history so you can start treating them
What determines treatment for HAPs?
Depends on the organism involved but if unknown cover the two most common HAP bugs; Pseudomonas, staph. aureus
Which type of pneumonia is pseudomonas most associated?
VAP
Who is most commonly affected by UTIs in hospital? How can they be prevented?
Elderly, they are most commonly caused by indwelling urethral catheters - so catheters should not be given unless absolutely necessary
What is the risk of CA UTIs? (Catheter associated UTIs)
Patient discomfort and safety, sepsis if progresses to a blood stream infection, increased hospital stay
Name two bugs that commonly cause UTIs, resp infections, wounds and skin sepsis and GI infections
UTIs: Klebsiella, E.coli
Resp infections: hemophilis influenza and staph aureus (and staph pneumonia)
Wounds and skin sepsis: staph. Aureus and E.coli
GI infections: salmonella, C. Difficile
What are the complications of SSIs? What has helped contribute to the significant reduction in rates of SSIs in hospitals?
Can double the length of post-operative stay - significant increases the cost of care. SSI surveillance systems in the UK have significantly reduced rates of SSIs
Name three major actions in place to help control HCAIs?
- Care quality commission (CQC): overviews safe care and treatment. Assesses every NHS hospitals and focuses on improving staff education and accountability, every health care provider has to comply to these regulations
- Public health England (PHE) runs a national surveillance programme and monitors trends
- Patients and cares should report and control HCAI
Describe how evidence based interventions combat HCAIs
They relate to key clinical procedures or care processes that can reduce the risk of infection if performed appropriately, i.e; catheters, care bundles for every type of line care
Highlights the critical elements of the care process and the key actions needed to prove reliability
Name five examples of PHE surveillance programmes over the years
Surveillances of SSI in orthopaedic surgery, MRSA bacteremia, C. Difficile infections for NHS acute trusts, have to report e.coli bacteremia and pseudomonas
How can HCAIs be classified? (4 ways)
- Community acquired; contracted/ developing outside hospital and requires an admission
- Infection contracted and developed within hospital
- Infection contracted in hospital but becomes clinically apparent after discharge
- Infections contracted by healthcare staff as a consequence of their work
Define primary and secondary bacteraemia and an example of each
Primary: due to direct introduction of organism into blood (i.e IV fluids)
Secondary: due to an infection already within the body (i.e UTI)
Name three airborne transmission routes
- Resin tract (coughing, sneezing, talking)
- Skin scales often spread visa the air
- Equipment that creates aerosols
Name the four overall routes of spread
- Airborne
- Fecal-oral/food-borne spread
- Contact
- Blood borne spread
Define self-infection and cross infection
Self-infection: infection caused by the movement of a microorganism from one part of the patient’s flora in its normal site to different site on the patient’s body’s (i.e wound)
Cross-infection: infection caused by microorganism from other patient or healthy staff carrier
Name five factors that will influence the ability of a microorganism to cause disease
- General health status: smoking, weight, underlying diseases
- Age: young and old
- Disease treatment: cytotoxic drugs and steroids increase risks of infection
- Undergoing invasive treatments or surgery (including length of procedure, introduction of foreign objects)
- Wounds or trauma
When do symptoms of norovirus begin after being exposures to the virus and what is the most common complication? How is recovery?
12-48 hours after exposure, dehydration is the most common complication. Recovery usually occurs after symptoms finish (24-72 hours) and there are no serious long term problems
How can norovirus spread?
Contact spread, fecal-oral route, touching contaminated surfaces and objects
What are the two main lab tests available for norovirus?
- EIA (enzyme immunosorbent assays) to detect norovirus antigens
- PCR: detects norovirus nucleic acid
Name six general factors that must be monitored as part of outbreak control measures
- Ward: closing affected areas, signs, informing visitors, etc
- Health care workers: education, try to allocate staff to either the affected or non-affected area of the ward (not both)
- Personal protective equipment
- Hang hygiene
- Equipment: user single-patient use equipment wherever possible and decontaminate all other equipment immediately after use
- Spillages: wearing PPE remove spillages with paper towels and then decontaminate are with an agent
Where is pseudomonas found and what kind of bacteria is it? What kind of pathogen is it and which groups of people are particularly at risk of contracting an infection of this bacteria in the lung?
Gram -ve rod bacteria found in soil, grown water, plants and animals.
Opportunistic pathogen, especially in those who are immunocompromised, have severe burns, diabetes or CF
Where odes pseudomonas particularly contaminate in hospitals?
Wet reservoirs such as respiratory equipment and indwelling catheters
How would MRSA look under a microscope with gram-staining?
Gram positive coccus
What is the Centor criteria and how is it used?
Developed to predict bacterial infection in people with an acute sore throat: must score 3/4 of the clinical signs to suggest the person has a bacterial infection and will benefit from antibiotics
- Tonsillar exudate
- Tender anterior cervical lymphadenopathy or lymphadenitis (inflammation)
- History of fever
- Absence of cough
How could the risk of an infection caused by a central venous line be reduced?
Silver coated central line has a lower risk of infection
How can anemia be linked with inflammation?
Inflammation can prevent the body from using stored iron to make enough healthy RBCs, leading to anemia
What congenital disorder is linked to an increased risk of endocarditis?
Bicuspid aortic valve
What type of bacteria is C.difficile?
Obligate anaerobe, gram +ve spore-forming rods, produces toxins
Why are catheters so associated with the development of bacteriuria?
Bacteria may enter the bladder during insertion, manipulation and drainage of the catheter and its presence promotes colonization by providing a surface for bacterial adhesion
Which organisms are most commonly associated with biofilm growth on catheters?
Pseudomonas and proteus
What can be observed in all patients with a catheter for more than a few days that isn’t synonymous with a UTI?
Polyuria - pus in the urine, elevated bacterial colony counts
What symptoms might patients with catheter-associated infections present with?
nonspecific symptoms such as fever and leucocytosis
How might the risk of infection when handling a catheter be reduced?
- Aseptic technique
- Using a closed drainage system and ensure unobstructed urine flow
- Good handwashing before and after catheter care
How does infective endocarditis commonly present? What do most affected patients have that predisposes them to the disease?
Pyrexia with unknown origin (PUO), Most patients have a pre-existing heart defect (congenital or acquired - i.e rheumatic fever) or an artificial heart valve
Which two organisms most commonly cause native valve endocarditis? Which organism is a common cause of early prosthetic valve endocarditis and is likely acquired at the time of surgery?
Native valve endocarditis: Species of oral streptococci and Staph. aureus (entering the bloodstream)
Early prosthetic valve endocarditis: coagulase-negative staphylococci
What can cause streptococci from the oral flora to enter the bloodstream how would they cause endocarditis?
Why is there a delay between initial bacteremia and symptom onset?
Dental procedures, vigorous teeth cleaning or flossing can allow bacteria into the blood where they then adhere to damaged heart valves which may have fibrin-platelet vegetation on their surface.
Organisms can produce dextran, adhesins and fibronectin-biding proteins which allow them to adhere to the vegetation. Once they’ve implanted on the valve, the organism multiplies attracting further deposition of fibrin and platelets, shielding itself from host defences.
The process of the continual vegetation growth and organism multiplying takes time and accounts for the delay between initial bacteremia and symptom onset
Name the signs and symptoms for endocarditis that correlate with the causes listed below:
- An infectious process on the valve
- Local intracardiac complications
- Septic embolization
- Circulating immune complexes
- bacteremia causing the focus of the infection in other sites
1: fever, malaise, anorexia, weight loss, nausea and vomiting
2. heart murmur
3. splinter hemorrhages and Janeway lesions
4. Immune complex disposition in kidney causing microscopic hematuria, Roth spots (retina), ossler’s nodes (painful, red, raised lesions found on the hands and feet)
5. signs of infection in other sites
What is the most important lab test when investigating possible endocarditis?
Blood culture: should obtain 3 separate ones taken at different times, ideally before antibiotics are administered to allow you to identify the causative organism
What determines the treatment of infective endocarditis? Why is prognosis still so poor?
The antibiotic chosen depends on the organism causing the infection.
Despite even being on the correct antibiotic, the prognosis is still poor as it can take weeks to fully eradicate and the patient still has a significant risk of relapse (likely due to the organism being protected from host defences and antibiotic therapy in the vegetation)
