Overview
Approximately 5 per cent of all patients
develop a nosocomial infection as a result of being hospitalized, with an
average resultant stay in-hospital of 13 days longer than controls. Costs
nationally are 5 billion dollars.
1.1. Nosocomial Infection:
An infection acquired in hospital
which was not present or incubating at admission.
Nosocomial infection (NI) incidence is
related to severity of underlying disease, i.e. patients with
a 50 per cent chance of death in 1 year have a 40 per cent chance of NI,
whereas a patient with a non-fatal illness have only a 3 per cent chance of
NI.
Sites of NI are found in the following frequency:
- Urinary Tract 40 %
- Surgical Wound 25 %
- Respiratory Tract 20%
- Bacteremia 3 %
- Other 12%
2. Agents
Organisms that cause nosocomial
infections are similar to community agents but there are
exceptions:MRSA (Methicillin Resistant S.
aureus), VRE (Vancomycin Resistant
Enterococci), and ESBL (Extended Spectrum Beta Lactamase
producing Klebsiella and E. Coli) have become more common.
3. Encounter
Organism transmission can occur from
direct contact from hands, or indirect through air, fomites
(environmental surfaces)!
Blood transfusions may be contaminated. Staff may be
carriers of organisms, such as S. aureus or group A B-hemolytic
streptococci.
Organisms in environment, like fungi, may be endemic,
but due to nature of immunosuppression cause disease in some hosts (like
BMT).
4. Entry
Organisms enter through barriers that
have been breached, such as intravenous catheters, or invasive
procedures.
4.3. Ingestion of C. difficile may lead to antibiotic associated diarrhea, or VRE may be ingested and lead to colonization which precedes invasive infection.
There are certain factors related to
hospitalization that carry an undue risk of a nosocomial
infection:Endotracheal Tube, Bladder
Catheter, Intravenous Catheter,
Non-Elective admission, age over 65
years, operative procedure during admission,
hyperalimentation (TPN),
immunosuppression.
5. Nosocomial Urinary Tract Infections
Usually related to GU manipulation and
Foley catheterization, closed- catheter drainage has decreased
the risk of bacteriuria but the risk is cumulative and is ~ 5% per day of
placement. Risk of bacteriuria related to skill of person inserting Foley, and
adequacy of Foley care (i.e. use of proper technique). Females > 50 have
highest risk of infection.
5.1. Pathophysiology of infection:
The collection bag may become contaminated or
organisms may traverse Foley-meatal interface, causative organisms are usually
host flora--E. coli Enterococci, Proteus, Klebsiella. Outbreaks
due to these and other organisms which are resistant to multiple antibiotics
have been reported. Systemic prophylactic antibiotics do not decrease risk and
may pre-dispose to superinfection; bladder irrigation with antibiotics not of
proven value.
Prevention includes removal of Foley catheter when
possible.
6. Nosocomial Wound Infection
Risk can be related to the type of
surgical procedure performed: Clean Wounds—sterile site
entered--risk 1-3%.
Clean-Contaminated--Respiratory, or GU tracts entered in
controlled circumstances--risk ~ 4% .
Contaminated Wounds--Open, Accidental Wounds, Gross
Spillage GI Tract, etc.--risk ~ 9%.
Dirty Wounds--infected site-risk ~ 13%.
Wounds can become infected at many times
during hospitalization: The OR may serve as a source through
contaminated instruments, personnel, etc.
As in urinary tract infections, patient's flora
may contaminate the wound, however hospital organisms usually predominate with
multiple antibiotic resistances.
When S. aureus or Group-A-beta-hemolytic
Streptococci cause several infections, one should worry about personnel as
carrier.
Prophylactic antibiotics administered at time of
surgery have been shown to be of benefit in preventing some types of
infections.
7. Nosocomial Respiratory Tract Infection
Coma, hypotension, tracheal intubation,
antimicrobics, renal failure, metabolic acidosis, leukocytosis or leukopenia
all are associated with colonization of the airway by Gram negative
bacilli. Age > 70, thoracic or abdominal surgery associated
with increased risk.
Colonization of airway does predispose to Nosocomial
Pneumonia--23 per cent colonized develop pneumonia versus 4 per cent not
colonized.
Decreased gastric acidity associated with increased risk
of colonization.
In 1960's, outbreaks of Nosocomial Pneumonia were
related to contaminated respiratory therapy equipment. With current usage of
disposable equipment, this is less of a hazard.
Gut decontamination regimens recently fashionable, do
not increase survival.
For some pathogens such as Pseudomonas or Acinetobacter
the risk of death increases 2 fold.
Prevention includes prone ventilation,
early extubation where feasible.
8. Primary Bacteremia
- Definition
- Primary bacteremia: not ascribable to another focus of infection, usually the result of a contaminated intravenous site or fluid (intra-arterial too!) or emanating from GI tract in neutropenic patient.
There are many different areas from
bottle to intravascular segment that can become contaminated during the course
of IV therapy.
Risk of IV infection related to type of cannula and
duration in site.
Usual pathogens are S. aureus, Klebsiella,
Pseudomonas, Enterococcus, Candida.
Antibiotic ointments at the site decrease bacterial
colonization rates, local infection rates and local phlebitis.
There have been nationwide outbreaks of IV fluid
infections related to contamination of IV bottle--unusual pathogens have been
involved-- Enterobacter agglomerans, a plant pathogen, has been
implicated in 3 epidemics, probably because of its ability to grow in D5W at
room temperature.
9. Preventability
It has been demonstrated that “Awareness
Programs” among Staff, Nurses, etc. can decrease the extent of
NI.
Handwashing, which has been
demonstrated to reduce transmission of organisms since 1600’s is not
performed frequently or properly. Studies in ICU show that about 25-35% of
patient encounters result in handwashing.
New alcohol based scrub – 10
second pump and distribute is superior to washing hands.
Prevention includes surveillance, education,
teaching. Each hospital mandated to have infection control committee.
Most have department with hospital epidemiologist, infection control
practitioners.
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