Pseudomonas (page 4)
© Kenneth Todar, PhD
Table 2. Diseases caused by
Endocarditis. Pseudomonas aeruginosa infects
of IV drug users and prosthetic heart valves. The organism establishes
itself on the endocardium by direct invasion from the blood stream.
Respiratory infections. Respiratory infections caused by Pseudomonas
aeruginosa occur almost exclusively in individuals with a
lower respiratory tract or a compromised systemic defense mechanism.
pneumonia occurs in patients with chronic lung disease and congestive
failure. Bacteremic pneumonia commonly occurs in neutropenic cancer
undergoing chemotherapy. Lower respiratory tract colonization of cystic
fibrosis patients by mucoid strains of Pseudomonas aeruginosa
common and difficult, if not impossible, to eradicate.
Bacteremia and septicemia. Pseudomonas aeruginosa causes
bacteremia primarily in immunocompromised patients. Predisposing
include hematologic malignancies, immunodeficiency relating to AIDS,
diabetes mellitus, and severe burns. Most Pseudomonas
is acquired in hospitals and nursing homes. Pseudomonas
for about 25 percent of all hospital acquired Gram-negative bacteremias.
Central nervous system infections. Pseudomonas aeruginosa
causes meningitis and brain abscesses. The organism invades the CNS
a contiguous structure such as the inner ear or paranasal sinus, or is
inoculated directly by means of head trauma, surgery or invasive
procedures, or spreads from a distant site of infection such as the
Ear infections including external otitis. Pseudomonas
is the predominant bacterial pathogen in some cases of external otitis,
including "swimmer's ear". The bacterium is infrequently found in the
ear, but often inhabits the external auditory canal in association with
injury, maceration, inflammation, or simply wet and humid conditions.
Eye infections. Pseudomonas aeruginosa can cause
infections in the human eye. It is one of the most common causes of
keratitis, and has been isolated as the etiologic agent of neonatal
colonize the ocular epithelium by means of a fimbrial attachment to
acid receptors. If the defenses of the environment are compromised in
way, the bacterium can proliferate rapidly through the production of
enzymes such as elastase, alkaline protease and exotoxin A, and cause a
destructive infection that can lead to loss of the entire eye.
Bone and joint infections. Pseudomonas infections of
and joints result from direct inoculation of the bacteria or the
spread of the bacteria from other primary sites of infection.
infections are most often seen in IV drug users and in conjunction with
urinary tract or pelvic infections. Pseudomonas aeruginosa has
particular tropism for fibrocartilagenous joints of the axial skeleton.
Pseudomonas aeruginosa causes chronic contiguous osteomyelitis,
from direct inoculation of bone and is the most common pathogen
in osteochondritis after puncture wounds of the foot.
Urinary tract infections. Urinary tract infections (UTI) caused
by Pseudomonas aeruginosa are usually hospital-acquired and
to urinary tract catheterization, instrumentation or surgery.
Pseudomonas aeruginosa is the third leading cause of
for about 12 percent of all infections of this type. The bacterium
to be among the most adherent of common urinary pathogens to the
uroepithelium. As in the case of E. coli, urinary tract
can occur via an ascending or descending route. In addition,
can invade the bloodstream from the urinary tract, and this is the
of nearly 40 percent of Pseudomonas bacteremias.
Gastrointestinal infections. Pseudomonas aeruginosa can
produce disease in any part of the gastrointestinal tract from the
to the rectum. As in other forms of Pseudomonas disease, those
the GI tract occur primarily in immunocompromised individuals. The
has been implicated in perirectal infections, pediatric diarrhea,
gastroenteritis, and necrotizing enterocolitis. The GI tract is also an
important portal of entry in Pseudomonas septicemia and
Skin and soft tissue infections, including wound infections,
and dermatitis. Pseudomonas aeruginosa can cause a variety
skin infections, both localized and diffuse. The common predisposing
are breakdown of the integument which may result from burns, trauma or
dermatitis; high moisture conditions such as those found in the ear of
swimmers and the toe webs of athletes, hikers and combat troops, in the
region and under diapers of infants, and on the skin of whirlpool and
tub users. Individuals with AIDS are easily infected. Pseudomonas
also been implicated in folliculitis and unmanageable forms of acne
Most strains of P. aeruginosaare resistant to killing
in serum alone, but the addition of polymorphonuclear leukocytes
in bacterial killing. Killing is most efficient in the presence of
opsonizing antibodies, directed primarily at the antigenic determinants
of LPS. This suggests that phagocytosis is an important defense and
opsonizing antibody is the principal functional antibody in protecting
from P. aeruginosa infections. Once P. aeruginosa infection is established, other antibodies,
such as antitoxin, may be important in controlling disease.
that patients with diminished antibody responses (caused by underlying
disease or associated therapy) have more frequent and more serious P.
aeruginosa infections underscores the importance of
immunity in controlling Pseudomonas
infections. unfortunately, cystic fibrosis is the exception. Most
cystic fibrosis patients have high levels of circulating antibodies to
bacterial antigens, but are unable to clear P. aeruginosa
from their lungs. Cell-mediated immunity does not seem to play a major
role in resistance or defense against Pseudomonas infections.
Epidemiology and Control of Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common inhabitant of soil,
and vegetation. It is found on the skin of some healthy persons and has
been isolated from the throat (5 percent) and stool (3 percent) of
patients. In some studies, gastrointestinal carriage rates
increased in hospitalized
patients to 20 percent within 72 hours of admission.
Within the hospital, P. aeruginosa finds numerous reservoirs:
disinfectants, respiratory equipment, food, sinks, taps, toilets,
showers and mops. Furthermore,
it is constantly reintroduced into the hospital environment on fruits,
plants, vegetables, as well by visitors and patients transferred from
facilities. Spread occurs from patient to patient on the hands of
personnel, by direct patient contact with contaminated reservoirs, and
by the ingestion of contaminated foods and water.
The spread of P. aeruginosa can best be controlled by observing
proper isolation procedures, aseptic technique, and careful cleaning
monitoring of respirators, catheters, and other instruments. Topical
of burn wounds with antibacterial agents such as silver sulfadiazine,
with surgical debridement, dramatically reduces the incidence of P.
aeruginosa sepsis in burn patients.
Pseudomonas aeruginosa is frequently resistant to many commonly
used antibiotics. Although many strains are susceptible to gentamicin,
tobramycin, colistin, and fluoroquinolins, resistant forms have
developed. The combination of gentamicin and carbenicillin is
frequently used to treat
severe Pseudomonas infections. Several types of vaccines are
tested, but none is currently available for general use.
END OF CHAPTER
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