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Flashcards in M26: Nosocomial Infections Deck (20)
1

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

2

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

3

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

4

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

5

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

6

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

7

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

8

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

9

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

10

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

11

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

12

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

13

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

14

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

15

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

16

How can nosocomial infections be prevented?

(i) _ before and after each patient contact

(ii) Enhanced _ precautions for patients with transmissible diseases

(iii) _ of hospital rooms

(iv) Adequate _ of equipment used in invasive testing

(v) Use of _

(vi) Rational use of _

(vii) Screening of the _ for bloodborne pathogens

(viii) Vaccination of susceptible healthcare workers against _, _, and _

i) Hand hygiene

ii) isolation

iii) Cleaning

iv) disinfection

v) perioperative antibiotic prophylaxis

vi) antibiotics

vii) blood supply

viii) Influenza, hepatitis B and varicella zoster virus (VZV)

17

Universal Precautions or Standard Precautions

These guidelines apply to all patients and stipulate that:

1) Gloves should be worn to touch any of the following: (4).

2) Hands should be washed immediately after _ and between _.

3) For procedures that are likely to generate splashes or sprays of body fluid, a _ and a _ should be worn.

4) _ should not be recapped, bent, or broken but disposed of in puncture resistant containers.

1) body fluids, secretions (except sweat), nonintact skin and mucous membranes

2) gloves are removed
patients

3) mask with eye protection or a face shield
gown

4) Needles

18

Transmission-based Precautions:

_ precautions are designed to prevent transmission of diseases by _ nuclei (

Airborne
droplet
dust
fomites

negative

N-95

tuberculosis, measles and disseminated varicella

19

Transmission-based Precautions:

Droplet precautions are designed to prevent transmission of diseases by (large / small)-particle (droplet) _.

These droplets are produced when the infected patient talks, sneezes, coughs and undergoes certain procedures (_ and _).

Measures:
Private room
All visitors must wear a surgical mask

For suspected or proven (5).

large
aerosols

suctioning and bronchoscopy

meningococcus, influenza, pertussis, mumps and rubella

20

Transmission-based Precautions:

Contact precautions are designed to prevent transmission of epidemiologically important organisms from the infected or colonized patient through direct (_) or indirect (_) contact.

Measures:
Private room (or cohorting of patients with the same species of organism into the same semiprivate room)
Gloves, gowns, patient-dedicated _.

For (9)

patient
patient’s environment

stethoscopes

MRSA, VRE, C. difficile, any diarrhea, rotavirus, hepatitis A, RSV, lice and scabies