Healthcare Associated Infections Flashcards
Describe HAI.
Healthcare associated infections (HAI) are infections that arise when patients are receiving treatment in a medical facility.
Describe endogenous and exogenous infections.
Endogenous infections originate from within the patient while exogenous infections arise from outside the body.
Describe skin, tissue and surgical site infections.
Skin, tissue and surgical site infections are commonly caused by S. aureus.
These infections are caused by unsterile dressings or surgical tools.
Surgeons and nurses may also be carriers of the pathogen.
Symptoms of this disease include red skin and pus around wounds.
Lab samples include swabs of the skin or surgical site, pus samples and tissue samples.
Describe urinary tract infections.
Urinary tract infections are caused by E. coli.
They can be caused by use of unsterile urinary catheters.
It is also caused by wiping incorrectly as E. coli is found on stools.
Urinary tract infections produce several symptoms, including frequent need to urinate, cloudy urine and pain while urinating.
Urine samples and the urinary catheters are taken as lab samples.
Describe bloodstream infections?
Bloodstream infections are commonly caused by E. coli and S. aureus.
It can be caused by the spread of urinary tract infections from the bladder to the kidneys to the blood.
Deep set skin and tissue infections can enter the blood and cause bloodstream infections.
It can also be caused by needle stick injuries, which is a risk for healthcare staff.
Bloodstream infections are characterised by the following symptoms: low body temperature; fast heartbeat; and fatigue.
Blood culture bottles are taken as lab samples.
Describe gastrointestinal tract infections.
Gastrointestinal tract infections are caused by C. difficile.
The infection is caused by contact of patients with carriers of C. difficile.
Gastrointestinal tract infections cause symptoms such as watery diarrhoea, stomach cramps and weight loss.
Faecal sample is taken as lab sample for gastrointestinal tract infections.
Describe the catalase test.
A colony of bacteria is grown on an agar plate and hydrogen peroxide is added on top.
If it contains catalase it will break down the hydrogen peroxide and form bubbles.
Describe the characteristics of S. aureus.
S. aureus are gram positive cocci that are facultative anaerobes.
They are catalase positive and beta haemolytic on blood agar.
S. aureus is a true pathogen as it is able to achieve all the requirements of true pathogens.
It colonises a host by using MSCRAMM’s (Microbial Surface Components Recognising Adhesive Matrix Molecules).
S. aureus is able to evade host defences by binding Protein A on its surface to IgG antibody upside down.
It also damages the host by producing invasins and exotoxins such as TSST-1 (Toxic Shock Syndrome Toxin 1).
Describe the general characteristics of E. coli.
E. coli are gram negative bacilli and facultative anaerobes.
They are catalase positive and beta haemolytic.
They also have peritrichous flagella.
E. coli are opportunistic pathogens, that cause urinary tract infections in immunocompromised or elderly patients, as well as patients on antibiotics.
E. coli normally causes food poisoning outside the hospital.
Describe the general characteristics of C. difficile.
C. difficile are gram positive bacillus and anaerobic.
They are non-haemolytic on blood agar and appear glossy or grey-coloured.
They also form spores.
C. difficile causes infections in patients with risk factors, although it can colonise healthy individuals without causing infection.
It produces several toxins, such as toxins A and B, which cause infections in humans.
Describe what a true pathogen is.
A true pathogen should be able to colonise the host and invade host tissues, while evading host defences.
Furthermore, it should be able to damage the host by producing exotoxins and invasins.
It should also be able to gain antibiotic resistance.
Explain how S. aureus became resistant to methicillin.
S. aureus contains SCCmec (Staphylococcal casette chromosome mec) which codes for PBP (penicillin binding protein).
This allows B-lactam antibiotics such as methicillin to bind.
MRSA (Methicillin resistant Staphylococcus aureus) incorporates MecA which codes for PBP2a.
This reduces affinity for B-lactam antibiotics and allows MRSA to gain resistance to B-lactam antibiotics.
Describe ways to break the chain of infection.
Identify organisms quickly and accurately.
Hand washing.
Wearing correct PPE.
Wearing gloves.
Prepare food correctly.
Monitor any changes in wounds.
Perform post-surgical swabs.
Sterilise equipment.
Reduce visitors.
