P. aeruginosa causes a variety of nosocomial infections, including
pneumonia, urinary tract infections, infected burn wounds, and bacteremia.
Infections with this pathogen are frequent in patients with immune deficiency
or diabetes. It is the primary pathogen in approximately a quarter of all patients
who die of sepsis (1). P. aeruginosa is the most common hospital-acquired
infection and has mortality rates ranging from 18% to 61% (2).
It is particularly notorious for introduction into
patients in intensive care units through contamination of catheters and ventilators.
P. aeruginosa is the most common respiratory infection in the genetic disorder
cystic fibrosis (3). Infections tend to become chronic as the infecting strain
converts to a mode of colonization including production of a biofilm. Once
infections reach this chronic status, they are nearly impossible to clear with
antibiotic treatment. Eighty percent of cystic fibrosis patients are infected
by P. aeruginosa by adulthood, and mortality is essentially tripled in
chronically infected patients.
P. aeruginosa produces a variety of virulence factors,
including enzymes that promote tissue invasion and extracellular polymers that
form the biofilm (4). The latter impedes attack by antibodies and host
phagocytes, and impedes access by some antibiotics. Biofilm formation appears
to be particularly relevant in lung infections, as well as in the colonization of
catheters. Biofilm formation permits the bacteria to
persist in the face of antibiotic treatment and promotes
development of resistant variants (5) The pathogen may then gain access to the
bloodstream causing death with a combination of endo- and exotoxins. In
addition to their intrinsic resilience towards antibiotic treatment, P.
aeruginosa infections are increasingly found to contain multidrug-resistant
plasmids. Patients in intensive care units are often treated with combinations
of antibiotics including aminoglycosides to ward off resistance. This practice is
accompanied by nephrotoxicity with up to a fourfold increase in mortality from
renal failure (6). Antibiotics also destroy normal flora and have other side
effects.Recent expert reviews suggest that deaths due to antimicrobial
resistant infections will cause more deaths than cancer in coming decades (7)
and are a dire warning to the world that we must increase our capacity to produce
new classes of antimicrobial therapies there
is an urgent need for changes to current practice to protect patients from and
eradicate antibiotic resistant bacteria, which have been identified in
hospitals around the world (8)Hence, bacteriophages have been explored as a biological
alternative or supplement to antibiotic therapy for pseudomonas infection, both
because of the mounting problems with antibiotic therapy for this infection and
because phages encode mechanisms to break down biofilms.
The objective of the study was to screen various
kinds of samples for Pseudomonas specific phages using an enrichment procedure
with a single host strain or P. aeruginosa, and to isolate and partially
characterize bacteriophages with broad activity spectra.