M26: Nosocomial Infections Flashcards
What are healthcare-associated infections?
Healthcare-associated infections (HAIs) are infections that patients acquire during _.
This differentiates them from _-acquired infections (that is, infections acquired outside of hospital).
the course of receiving healthcare treatment for other conditions
community
How do healthcare-associated infections occur?
Nosocomial infections are frequently spread from _ to _. This is relatively easy to achieve in a setting, such as a hospital, where people are _. There are five important ways by which nosocomial infections are spread from person to person:
(i) Via the hands of _
(ii) Via contact of the patient with a _ environment
(iii) Via use of a _ (such as a )
(iv) _ transmission (such as with (4))
(v) Via _ administered in the hospital ( or _)
person to person
crowded together
i) doctors, nurses and other healthcare workers
ii) contaminated hospital
iii) poorly cleaned piece of equipment in the hospital (such as a bronchoscope or thermometer)
iv) Airborne
influenza, Aspergillus, varicella zoster virus or Mycobacterium tuberculosis
v) blood
hepatitis B or HIV
Which infections are the most common healthcare-associated infections?
The most common nosocomial infections are:
(a) _, particularly in patients who are undergoing mechanical ventilation
(b) _, such as when a patient has an indwelling urinary catheter
(c) _ infections
(d) _ infections, such as occurring when intravenous lines become infected
a) Pneumonia
b) Urinary tract infections
c) Surgical wound
d) Bloodstream
What are the problems caused by hospital-acquired Clostridium difficile infection?
Clostridium difficile is an (aerobic / anaerobic), ((non-)spore-forming), ((non-)toxin-producing) Gram-(positive / negative) _.
Because of “the unusual difficulty which was encountered in its isolation and study” it was originally named Bacillus difficilis!
However, _ have now been developed which are highly selective for C. difficile.
It is the most common cause of hospital-acquired infectious _.
anaerobic spore-forming toxin-producing gram-positive rod
media
diarrhea
What are the problems caused by hospital-acquired Clostridium difficile infection?
Why is it a problem in hospital?
C. difficile _ can inhabit multiple inanimate environmental sources in the hospital and the hands of healthcare workers. Thus, the organism can be readily ingested inadvertently in the hospital setting. The viability (up to 5 months!) of the _ allows C. difficile to persist in the hospital environment.
In addition to wearing gloves and gown it is imperative to wash hands before and after entering the room, in this case only with _ and _ (NOT _) to remove the spores.
Use of antibiotics is a prerequisite to development of C. difficile associated _. Not surprisingly, antibiotic use is common in hospitals!
Pathogenesis
(i) The use of antibiotics alters the flora in the _.
(ii) Alteration of _ flora allows C. difficile to multiply in the _.
(iii) Toxin production by C. difficile leads to _
spores
spores
water and soap
alcohol
diarrhea
i) gut
ii) bowel
gut
iii) diarrhea
What are the problems caused by hospital-acquired Clostridium difficile infection?
The toxins of C. difficile
Toxin A
- An _
- Causes disruption of _ pathways and leads to interference with the _ of intestinal epithelial cells, thereby rendering them nonfunctional and “leaky”
- Can provoke intense _ through its ability to act as a chemoattractant for neutrophils and by stimulating the release of endogenous mediators of _ (such as tumor necrosis factor)
Toxin B
- Also interferes with the _ of intestinal epithelial cells and provokes _ by the same mechanisms as Toxin A
- Induces significant _ in tissue culture cell lines, thereby enabling the diagnosis
Binary toxin
- Found in (many / some) isolates
- Also _-specific but by adding _ onto actin, thereby causing cytoskeletal effects
- enterotoxin
- signal transduction, actin cytoskeleton
- inflammation, inflammation
- actin cytoskeletons, inflammation
- cytopathic effect
- some
- actin, ADP-ribose
What are the problems caused by hospital-acquired Clostridium difficile infection?
Clinical manifestations:
Spectrum from _ carriage to _ to toxic _ and death. Relapse may occur after apparently successful treatment.
Detection:
- On microscopy of stool, elevated numbers of _ (via pro-inflammatory effects of toxin _ and _ as noted above), but this is a nonspecific finding
- On sigmoidoscopy may see characteristic _ (hence the alternative name, “_”)
- The gold standard is detection of organism by culture and testing isolates for _. Culture-free detection of toxin can also be achieve by using a cell culture cytotoxicity assay, by a toxin _ or detection of the toxin gene by _
asymptomatic
diarrhea
megacolon
fecal leukocytes
A and B
pseudomembranes
pseudomembranous colitis
toxigenicity
ELISA
PCR
What are the problems caused by hospital-acquired Clostridium difficile infection?
Treatment:
_ (oral or IV) or oral _ (but NOT IV).
Prevention:
Patients found to have C. difficile are placed into _ and handwashing with water and soap (not _ antiseptics) is required after contact with C. difficile infected patients.
Metronidazole
vancomycin
isolation
alcohol
What are the problems caused by hospital-acquired Enterococcus faecium infections?
Enterococcus is a Gram (positive / negative) _ that occurs _, in _, and in _.
The enterococci are (obligate / facultative) (aerobes / anaerobic). As the names of the two most common species (Enterococcus faecalis and Enterococcus faecium) suggests, the usual habitat of organisms of this genus is the _.
Like Klebsiella spp., Enterococci will colonize the _ of hospitalized patients and can be transferred readily from patient to patient. They are a common problem in intensive care units and surgical units.
These organisms can produce _ infection (sometimes resulting in _) and _.
Many more patients are (infected / colonized) than are (infected / colonized) – this has important implications since colonized patients are still reservoirs of organisms that could potentially be transmitted from person to person.
positive
coccus
singly, in pairs and in short chains
facultative anaerobes
lower gastrointestinal tract
skin
bloodstream
endocarditis
urinary tract infection
colonized
infected
What are the problems caused by hospital-acquired Enterococcus faecium infections?
Treatment of Enterococcus faecium is difficult because of alterations in the _ leading to _ and _ resistance.
_ and _ are two antibiotics that are still active against vancomycin resistant Enterococci (VRE).
In many hospitals all patients are screened for fecal carriage (colonization) of _. When identified as carriers, patients are _ in a separate room and measures such as wearing gowns and gloves for health care workers room are implemented to limit the spread to other hospitalized patients. This in addition to standard precautions which include hand washing before and after entering the patient room.
cell wall
ampicillin and vancomycin
Linezolid and daptomycin
VRE
isolated
What are the problems caused by hospital-acquired Staphylococcus aureus infections?
Staphylococcus aureus is a Gram (positive / negative) _ that occurs in _ and is coagulase (positive / negative).
Many patients carry this organism in their _ or _ area. It is a very common cause of _ infections, _ and _ infections.
More than 50% of all nosocomial Staphylococcus aureus is now -resistant () and empiric antibiotic regiments for patients with a suspected nosocomial infection often include _.
In contrast, coagulase (positive / negative) Staphylococci (such as Staphylococcus epidermidis) are very common colonizers of the skin of healthy humans and only rarely cause nosocomial infections only when associated with _ or _ (hip prosthesis, pacemaker, prosthetic heart valve).
In many hospitals all patients are screened for carriage (colonization) of _ and if positive, they are _ and health care workers must wear gowns and gloves to limit the spread to other hospitalized patients. This in addition to standard precautions which include hand washing before and after entering the patient room.
positive
coccus
clusters
positive
nose or groin
wound infections, abcesses, and blood stream infections
methicillin (MRSA)
vancomycin
negative
intravascular lines or implanted foreign materials
MRSA
isolated
What are the problems caused by hospital-acquired Klebsiella infections?
Like other members of the family Enterobacteriaceae, Klebsiella is a Gram (positive / negative) _ that grows both aerobically and anaerobically but does not form _.
It is a normal inhabitant of the _. There are several species, the most important of which is Klebsiella _.
Why is it a problem in hospitals?
The _ of hospitalized patients becomes colonized with Klebsiella and other fecal flora. Contact of our hands with the patient’s skin results in colonization of our _. Although the hand colonization is (transient / long-lasting) (lasting 10-15 minutes), this is enough time to pass the organism on to another patient.
Where is it a problem?
It is a particular problem in intensive care units, especially _ intensive care units
By what means is the organism pathogenic?
Klebsiella is characteristically _ and this allows it to resist _.
negative
bacillus
spores
lower gastrointestinal tract
pneumoniae
skin
hands
transient
neonatal
mucoid
phagocytosis
What are the problems caused by hospital-acquired Klebsiella infections?
Clinical manifestations
Varied, but include _ infection, _ and _
Treatment
All Klebsiella pneumoniae isolates produce a chromosomally encoded _ which inactivates _.
The genes which encode this and other beta-lactamases can mutate resulting in structural changes that lead to a (narrower / broader) spectrum of antibiotic resistance. These strains are known as _ producers.
Treatment thus depends on the presence or absence of these _. In addition to standard precautions which include hand washing before and after entering the patient room some hospitals add contact _ procedures when these isolates are multi-drug resistant.
bloodstream
nosocomial pneumonia
urinary tract infection
beta-lactamase
ampicillin
broader
extended-spectrum beta-lactamase (ESBL)
beta-lactamases
isolation
What are the problems caused by hospital-acquired Acinetobacter infections?
Acinetobacter baumanii is a Gram (positive / negative), (aerobic / anaerobic) _ which inhabits the hospital environment. It (does / does not) form spores, and is quite resistant to _. Its genome is quite plastic and readily acquires various _ genes.
Why is it a problem in hospitals?
A. baumanii can survive on (wet / dry) surface for days to weeks. Contact of our hands with the skin of a colonized patient or contaminated surface results in colonization of our _ and subsequent spread to others.
negative aerobic rod does not dessication antibiotic resistance
dry
hands
What are the problems caused by hospital-acquired Acinetobacter infections?
Where is it a problem?
Like Klebsiella, _ are affected most. The ubiquitous use of antibiotics in these units helps select for organisms that are most intrinsically resistant.
Another common scenario of Acinetobacter infections is in severely _. Whether they acquire the organisms directly from wound exposure to the soil (explosions) or in first line field hospitals is unclear.
By what means is the organism pathogenic?
Like other Gram-(positive / negative) pathogens, it produces _. However, it is most often just a colonizer selected for in patients exposed to multiple antibiotics.
When the Acinetobacter does cause disease such as _, it may be virtually _ due to its inherent multi-drug resistance.
intensive care units
wounded soldiers from Afghanistan
negative
endotoxin
ventilator associated pneumonia (VAP)
untreatable
