Lecture 10 - Hospital-acquired and community acquired infections
HA-BSI's are generally due to poor _______ technique or when bacteria form biofilms on ________. During catheter insertion, bacteria are directly _________ into the blood or contaminated ___________ are infused through the lines. Alternatively, the bacteria form _________ around the skin, and then undergo retrograde ____________ through a skin wound.
aseptic, catheters, inoculated, substances, biofilms, migration
SSI's can be __________, from the patient's own microbiota, or ________, from the environment, medical devices, health care workers.
endogenous, exogenous
Most SSI infections are due to organisms that colonise during a ___________ and due to error in __________ technique.
surgery, surgical
What is pneumonia?
Infection of lower respiratory tract (generally in alveoli of lungs) where inflammation causes exudate and fluid in alveoli
What are the risk factors of UTI's? - -
- urinary catheter - pathogenic bacteria in periurethral area
What are the most common HAI's? - - - -
- urinary tract infections (UTI's) - surgical site infections (SSI's) - lower respiratory tract infections (LRTI's) - blood stream infections (BSI's)
What are the aetiological agents that cause UTI's by order of prevalence of infection? - - - - - -
- E. coli (50% of cases) - Proteus, Klebsiella, Enterobacter (10%) - Enterococci (10-20%) - Staphylococcus epidermidis (10-20%) - Pseudomonas (10%) - Candida (5%)
What are the risk factors associated with HA-LRTI's? - - - - -
- Intubation (ventilator-associated pneumonia) - Intensive care units - Chronic lung disease and/or smoking - old age - immunosuppression
What are the most common aetiological agents of HA-BSI's? - - - - -
- Staphylococcus epidermidis (produces biofilms) - Staphylococcus aureus (MRSA) - Enterococci (VRE)(also produce biofilms) - Candida (biofilms) - E. coli, Klebsiella, Pseudomonas
How are HAI's generally transmitted? - - - -
- airborne - direct/indirect contact - droplet - common vehicle
Why are the elderly more susceptible disease? - -
- comorbidities that increase susceptibility - immunosenescence
What are some factors that can increase the rates of HAI's? - - - -
- crowded hospital conditions - increased number of people at risk - new organisms - increased antimicrobial resistance
What are the aetiological agents of HA-SSI's? - - -
- gram + bacteria such as MRSA, Staph. epidermidis (forms biofilms), Enterococcus (also produces biofilms) - gram -, Pseudomonas, E. coli, Klebsiella, Enterobacter - Obligate anaerobes, such as Bacteroides, Clostridium, FUsobacterium (common during abdominal pelvic surgery)
What are the risk factors/factors that contribute to HA-SSI's? - -
- host/patient susceptibility level - contamination level of the wound (wound clean, 3% risk [clean as in non-traumatic, non infected], clean yet contaminated [10% risk], contaminated and dirty [16-30% risk, where the is open, fresh wounds, trauma, gross spillage from GIT, infected tissues or body fluids])
What are some aetiological agents of HA-LRTI's? - - - - -
- often polymicrobial, but most commonly gram - faecal microbiota (Enterobacteriaceae [Klebsiella, E. coli]) or Pseudomonas - Staphylococcus aureus (20%) - Streptococcus pneumoniae (10%) - Haemophilus (5%) - Legoinella/Acinetobacter - Candida
What are the treatments/preventative measures for HA-UTI's? - - - -
- removal of catheter - antimicrobials - aseptic technique during insertion of catheter - infection resistant catheters, antimicrobial catheters (e.g. catheters made of silver)
Why are patients more likely to develop infections in hospitals? - - - -
- susceptibility of host is increased (natural reason of being at hospital is due to some kind of unwell) - organisms at hospital relatively virulent due to antimicrobial resistance (presence in 70% of cases in US) - people in hospitals have more portals of entry due to hospital treatment (e.g. wound, catheters, surgical incision, IV lines, ET tubes) - crowded conditions, integration of many diseases in hospital
Why do BSI's have a high rate of mortality? What is the rate of mortality of BSI's?
20-40%, often leads to sepsis
Outline the risk and cumulative risk of ventilated/intubated patients with pneumonia.
25% of intubated patients develop pneumonia, of the infected cases, there is a 30-50% chance of mortality. 1-3% cumulative risk per day intubated. NB: Those intubated are already likely to be ill and/or immunocompromised, so susceptibility is increased even more.
After how many days of catheter use will a person have a 100% chance of developing bacteriuria? What percentage of these people will develop bacteremia?
30 days after catheter use; 3% of which develop bacteremia
What is cumulative risk of catheter use for UTI's per day?
5% a day
Why is it difficult to treat HA-LRTI's?
70% of HA-LRTI's are polymicrobial, therefore, it is hard to treat and find antimicrobials that work against all aetiological agents.
Define community-acquired infection.
An infection contracted outside a healthcare setting OR An infection present on admission of a healthcare setting.
What is the main virulence factor of VRE's?
Biofilm production
What is the fourth most common HAI?
Blood stream infections (BSI's)
Compare and contrast CA-MRSA to HA-MRSA.
Both strains of MRSA are resistant to many drugs, however, HA-MRSA strains are generally more resistant to antibiotics, but less virulent (PVL -ve), on the other hand, CA-MRSA strains are less resistant, but more virulent (PVL +ve).
What is the general cause of most urinary tract infections of HAI's?
Catheter use (80% of all cases assocaited)
What type of medical insertion/device is most commonly associated with HA-BSI's?
Central venous catheters
How can we diagnose an ESBL-producing bacteria infection?
Difficult to diagnose, generally only way is if the treatment given does not improve patient condition.
What does ESBL stand for, hence, what are ESBL-producing bacteria? Include reference to what types of antibiotics they may be resistant to and what species of bacteria they may be.
ESBL stands for extended spectrum beta-lactamase, ESBL producing bacteria are highly resistant to many types of antibiotics including all penicillin and third generation cephalosporins. ESBL-producing bacteria are mostly gram -ve bacteria, such as E. coli and Klebsiella.
How are ESBL-producing bacteria treated? Outline all antibiotics that can be used.
ESBL-producing bacterial infections are treated with imipenem, however, resistance to imipenem is emerging, therefore, if the strain is resistant to imipenem, treatment is with carbepenem, however, some gram -ve ESBL-producing bacteria are also carbepenem resistant, and we therefore treat with colistin. However, in 2017, a case of colistin-resistant strain of ESBL-producing bacteria was identified, and no treatment was thus available.
HAI's can arise from ___________ microbes, where they were originally part of the patient's microbiota, or ____________ microbes, form health care workers, visitors, other patients, or hospital environment.
Endogenous, exogenous
What is the source of uropathogens? How do they infect the urinary tract?
Generally of faecal origin that is endogenous and colonises periurethral tissue, upon insertion of catheter, bacteria are pushed into bladder or uropathogens produce biofilms on the catheter and slowly progress up the catheter until they reach the bladder
Define hospital acquired infection.
Infections that were not present and without evidence of incubation at the time of admission to a healthcare setting. OR Infections acquired from the hospital that onset 48 hours after admission or within 30 days of discharge
Which HAI is the leading cause of death of HAI's?
LRTI
What is the standard antibiotic used to treat VRE's?
Linezolid; however, linezoli resistant VRE strains emerging.
What is the third most common HAI?
Lower respiratory tract infection
Why are VRE's difficult to treat?
Multi-resistant to antibiotics (e.g. vancomycin)
What is the other name for hospital acquired infection?
Nosocomial infection (nosocomail hospital-associated)
Is bacteriuria dangerous? What complications are associated?
Not necessarily, it is often asymptomatic, but can become bacteremia and then sepsis, additionally, can act as a reservoir for antimicrobial resistant gram -ve bacteria.
HA-BSI's can be caused by primary or secondary infections, what are primary/secondary infections? Note the type of bacteria that cause them as well. Primary: Secondary:
Primary: Caused by central lines such as IV access devices that directly associate with the blood stream; caused by gram + bacteria that produce biofilms on medical equipment such as catheters, IV lines; bits of biofilm may break off leading to infection. Secondary: Caused by bacteria that are from a distant site of the body and don't generally colonise catheters, IV lines, etc.; can be gram - bacteria, but generally HAI BSI's are due to gram +ve's.
What is the second most common HAI?
Surgical site infectino (SSI)
What is the most common form of HAI?
UTI's (40% of all HAI's)
Are VRE's more common in HAI's or CAI?
Usually only HAI's, but may move to CAI's.
