BRIEF REPORT • CID 2003:36 (1 February) • e55
B R I E F R E P O R T
due to Pseudomonas aeruginosa
Christopher J. Crnich, Barbara Gordon, and David Andes
Department of Medicine and Section of Infectious Diseases,
University of Wisconsin Hospital and Clinics, Madison
We describe a case of severe necrotizing pneumonia due to
community-acquired Pseudomonas aeruginosa. Cultures of
fluid obtained from the filter of the patient’s hot tub grew
the same P. aeruginosa strain as that grown from culture of
the patient’s sputum. Centers for Disease Control and Pre-
vention guidelines should be strictly followed for hot tub
maintenance to prevent P. aeruginosa overgrowth: the range
of free chlorine levels in the water should be kept at 1–3 mg/
L, and the pH should be kept at 7.2–7.8.
Pseudomonas aeruginosa is a common cause of nosocomial res-
piratory tract, urinary tract, and bloodstream infections but re-
mains a rare cause of community-acquired infection despite its
environmental ubiquity. Herein we report a case of severe nec-
rotizing pneumonia due to community-acquired P. aeruginosa.
A 40-year-old man with a history of tobacco
use presented to the emergency room after experiencingseveral
days of fevers, chills, and a cough producing blood and rust-
colored sputum. Physical examination revealed a temperature
of 37.3?C and tachypnea (respiratory rate, 24 breaths/min).
Chest examination revealed decreased breath sounds in the
upper lung fields bilaterally that were especially notable at the
right apex. There were no rales noted, and there was no evi-
dence of egophony or increased tactile fremitus. The findings
of the physical examination were otherwise unremarkable.Lab-
oratory abnormalities included leukocytosis (WBC count,
17,900 cells/mL) with a left shift (83% neutrophils), a platelet
count of 623,000 cells/mL, and a serum sodium level of 127
mM. Chest radiographs revealed a right upper-lobe cavitary
Received 13 May 2002; accepted 22 October 2002; electronically published 20 January
Reprints or correspondence: Dr. David Andes, Department of Medicine and Section of
Infectious Diseases, University of Wisconsin Hospital and Clinics, 600 N. Highland Ave.,
Madison, WI 53792 (firstname.lastname@example.org.)
Clinical Infectious Diseases2003;36:e55–7
? 2003 by the Infectious Diseases Society of America. All rights reserved.
lesion with left apical scarring (figure 1), and a subsequent
chest CT scan revealed bullous emphysema and consolidation
with multiple cystic lesions in the right upper and middle lobes
consistent with necrotizing pneumonia. There were no radio-
graphic findings to imply bronchiectasis.
The patient was admitted to the hospital and placed in an
airborne isolation room because of concerns he was infected
with Mycobacterium tuberculosis. He was empirically treated
with ampicillin-sulbactam to include coverage for aspiration
pneumonia. Staining of sputum samples for an acid-fast ba-
cillus was negative 3 times, and the result of HIV serologic
testing was negative. The initial Gram stain of an expectorated
sputum sample revealed 125 polymorphonuclear cells per low-
power field and !10 epithelial cells per low-power field with
of hospitalization, results of sputum culture performed by the
microbiology laboratory confirmed the predominant growthof
P. aeruginosa, with a lesser growth of Escherichia coli. Both
organisms were sensitive to ciprofloxacin, ceftazidime, and an-
tipseudomonal penicillins, and, although the P. aeruginosa iso-
late was intermediately resistant to gentamicin, it was sensitive
to tobramycin. On the basis of these results, the patient’s an-
timicrobial regimen was changed to ticarcillin-clavulanate and
Additional questioning revealed that the patient owned a hot
tub and that he had been using it almost daily for the past
several weeks. Furthermore, the patient reported drinking al-
coholic beverageswhilein thehottubandrememberedchoking
on water from the hot tub. He had not received any antimi-
crobials during the past year and had last been hospitalized
when he was a child. He denied having any skin rash or ear
pain suggestive of folliculitis or otitis externa.
The patient improved clinically and was discharged home
12 days after admission receiving oral ciprofloxacin therapy.
The patient completed a 6-week total course of antibiotics,and
an outpatient follow-up visit 1 month after discharge revealed
that the patient was healthy. A chest radiograph obtained 6
weeks after discharge revealed right apical scarring of the lung
but otherwise complete resolution of parenchymal infiltrates.
The patient has since remained healthy more than a year after
his admission to the hospital.
The patient’s family brought us the hot tub filter because
they were concerned that others would become ill. Cultures of
fluid from the filter were positive for a P. aeruginosa species
with the same antimicrobial susceptibility as that of the species
grown from culture of the patient’s sputum, and restriction
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e56 • CID 2003:36 (1 February) • BRIEF REPORT
revealing a right apical cavitary lesion and left upper-lobe scarring.
Chest radiograph of the patient at admission to thehospital,
2 and 3, isolates from the patient’s hot tub filter; lanes 4–6, isolates
from the patient’s sputum; lanes 1 and 8, l ladder; lane 7, control strain
of P. aeruginosa.
PFGE patterns of Pseudomonas aeruginosa isolates: Lanes
fragment–length polymorphism analysis of both the patient’s
sputum isolate and the hot tub filter isolate was subsequently
performed to determine whether they were the same strain. P.
aeruginosa strains were classified as epidemiologically distinct
if a difference of 13 bands was observed . PFGE results
demonstrated the presence of 2 distinct P. aeruginosa strains in
the hot tub water (figure 2, lanes 2 and 3), one of which (lane
3) has a PFGE pattern identical to that of the P. aeruginosa
strain isolated from the patient’s sputum (lanes 4–6).
P. aeruginosa is an aerobic gram-negativebac-
terium that can be isolated from a broad spectrum of sources
in the environment, including water, soil, plants, and animals
(including humans). It has minimal nutritional requirements,
which allow it to multiply even in distilled water. This char-
acteristic explains why P. aeruginosa can be isolated from such
varied environmental sources as respiratory equipment, clean-
ing solutions, disinfectants, sinks, loofah sponges, swimming
pools, hydrotherapy tanks, whirlpools, hot tubs, and contact-
lens solution .
P. aeruginosa is rarely isolatedfromhealthypersons,although
it can sometimes be cultured from moist areas of the body,
such as the axilla, perineum, and the intestinal tract, where it
is considered a saprophyte. P. aeruginosa is more commonly
isolated from the sputum of patients with underlying immu-
nosuppression, such as HIV infection , and chronic lung
disease, such as bronchiectasis and cystic fibrosis .
A few types of community-acquiredpseudomonalinfections,
ranging from minor to serious, have been well described in the
literature, including green nail syndrome, toe-web infection,
hot tub-associated folliculitis, whirlpool-associated urinary
tract infection, otitis externa, pedal osteomyelitisafterpuncture
wounds, and right-side endocarditis in injection drug users.
In contrast, community-acquired pneumonia due to P. aeru-
ginosa is rare.
Community-acquired P. aeruginosa pneumonia in patients
without characteristic risk factors has been the subject of only
a few case reports published since the 1970s [4–14]. Although
some of these cases were attributable to an identifiable source,
such as a home humidifier  or a home whirlpool spa ,
most cases had no identifiable environmental source of infec-
tion [4–7, 10–14]. Our case adds to this small list of com-
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BRIEF REPORT • CID 2003:36 (1 February) • e57
munity-acquired cases of P. aeruginosa pneumonia and is, we
believe, the first in which molecular subtyping techniques were
used to definitively confirm that a patient’s infection derived
from an environmental source.
By use of molecular subtyping techniques, we were able to
show conclusively that our patient had acquired the P. aeru-
ginosa strain that caused his infection from his hot tub. Several
factors put the patient at risk for pneumonia, most notably
alcoholism and underlying structural lung disease. One recent
prospective trial reported that P. aeruginosa was recoveredfrom
5% of patients presenting with severe community-acquired
pneumonia, and that alcoholism was anindependentriskfactor
for severe pneumonia .
Review of the CT scan performed for our patient at admis-
sion to the hospital confirmed the presence of underlying bul-
lous emphysema, although there was no evidence of bronchi-
ectasis in any of the images. Although the latter form of
structural lung disease has clearly been associated with a risk
for colonization or infection with P. aeruginosa, we are not
aware of literature demonstrating a similar association with
emphysema or chronic bronchitis.
Studies performed in the 1980s, amid rapidly increasing re-
ports of whirlpool-associated folliculitis,documentedtheheavy
growth of P. aeruginosa in health spa and personal-use hot tubs
. On the basis of these reports, the Centers for Disease
Control and Prevention published guidelines that specifically
recommended that free chlorine levels in the water of public
hot tubs be kept at 1–3 mg/L and the pH be kept at 7.2–7.8
to prevent P. aeruginosa overgrowth .
Most studies of whirlpool-associated folliculitis have shown
inadequate free chlorine levels (!1.0 mg/L) in the water that was
the source of infection. Free chlorine levels dissipate rapidly in
and it has been shown that an elevated water pH (17.6) is as-
sociated with a reduced antibacterial effect of halogens .
Studies suggest that P. aeruginosa can multiply to levels of 104
to 106organisms/mL if the free chlorine level is allowed to drop
to !1 mg/L or if the pH is allowed to rise to 17.8 for even as
short a time as 24 h . Therefore, it is necessary to monitor
these levels on a frequent basis, in order to maketheadjustments
necessary to maintain the appropriate level of disinfection, and
to change the water regularly, especially after heavy use.
Despite the severity of P. aeruginosa pneumonia, empirical
therapy for community-acquired infections cannot be recom-
mended because of its rarity. However, this case demonstrates
that recognition of potential environmental exposures is im-
portant for early diagnosis of and therapy for pneumonia of
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