MICROBIOLOGY AND INFECTIOUS DISEASE
Original Article
Infections With Roseomonas gilardii and Review of
Characteristics Used for Biochemical Identification and
Molecular Typing
LINDA LEWIS, MD, 1 FRIDA STOCK,2 DENISE WILLIAMS, MT(ASCP)M, SM, 2 SUSAN WEIR, PhD, 2 AND VEE J. GILL, PhD 2
Roseomonas is a recently described genus of gram-negative coccobacilli formerly designated as "pink-coccoid" groups I through
IV by the Centers for Disease Control and Prevention (Atlanta,
Ga) because of the organism's characteristic pink colonies. Since
1991 we have isolated Roseomonas from eight patients; in seven
from blood cultures and in one from a skin lesion. The seven
blood isolates were from patients with clinically significant
underlying diseases who had central venous catheters in place;
the majority were associated with polymicrobial catheter infections. Additional characteristics of their infections are described.
The eight isolates had originally been identified by us as Centers
for Disease Control (CDC) pink-coccoid group III. These organisms were re-identified using the criteria of Rihs et al, and all isolates fit most closely with Roseomonas gilardii. Antibiotic profiles were fairly homogeneous showing susceptibility to many
antibiotics, but uniform resistance to cefoxitin, ceftazidime, and
piperacillin. Attempts to determine whether the isolates were the
same strain by pulsed-field gel electrophoresis suggested that 3
of the isolates were similar. Random amplified polymorphic
DNA analysis, however, demonstrated that each of the eight isolates was a unique strain. (Key words: Roseomonas, infections;
Characteristics; Typing) Am J Clin Pathol 1997;108:210-216.
Roseomonas is a recently described genus of gram-negative coccobacilli1 that had previously been designated
as "pink-coccoid" groups I through IV2 by the Special
Bacteriology Reference Laboratory of the Centers for
Disease Control and Prevention (CDC, Atlanta, Ga).
On the basis of biochemical reactions and DNA relatedness of 42 pink coccoid isolates, Rihs et al1 proposed
that the genus Roseomonas should contain six new
species: Roseomonas gilardii, Roseomonas cervicalis,
Roseomonas fauriae, and unnamed genomospecies 4, 5,
and 6. The strains they examined included 6 strains
each of CDC-designated pink-coccoid groups I, II, III,
and IV, along with a variety of other isolates. In this
collection of 42 strains R gilardii turned out to be the
most common isolate (23 of the 42).
In January 1991, we isolated our first pink-coccoid
o r g a n i s m from a blood culture obtained from a
patient at the Warren Grant M a g n u s o n Clinical
Center Hospital of the National Institutes of Health
(NIH, Bethesda, Md). Since that time we have identified seven isolates from blood cultures and one from
a skin lesion. Until 1993, we used the criteria of
Wallace et al 2 to identify these strains, all of which
were identified as pink-coccoid group III. We reevaluated these strains using the more recent criteria of
Rihs et al 1 and found that our eight isolates were all
most consistent with R gilardii, the most common
Roseomonas species reported in their series.
For the current report, we studied the clinical characteristics of infection with this organism, and the
pertinent findings are summarized. The biochemical
identification, antibiotic susceptibility, and strain
identification of R gilardii are discussed.
From the ^Pediatric Branch, National Cancer Institute, Bethesda,
Maryland, and the 2Microbiology
Service, Clinical
Pathology
Department, Warren Grant Magnuson Clinical Center, National
Institutes of Health, Bethesda, Maryland.
MATERIALS AND METHODS
Patients
M a n u s c r i p t received October 23, 1996; revision accepted
December 19,1996.
Address reprint requests to Dr Gill: Microbiology Service, Bldg
10, Rm 2C-385, NIH, Bethesda, MD 20892.
Dr Lewis is currently with the Pediatric Infectious Diseases
Section, A. I. duPont Institute, Wilmington, Delaware.
All patients from whom a pink coccoid organism
was isolated from any source were included for
study, resulting in eight isolates, seven from blood
210
211
LEWIS ET AL
Roseomonas
and one from a leg wound. The medical records of the
seven patients with positive blood cultures were
reviewed to obtain clinical data.
Organism
Identification
The pink-coccoid isolates were identified by the special bacteriology section of the NIH Microbiology
Service, using the criteria of Wallace et al.2 All eight isolates were most consistent with pink-coccoid group III.
To classify these organisms according to the criteria of
Rihs et al, 1 additional biochemical testing was performed. The most pertinent biochemical tests to establish the Roseomonas species identification were as follows: esculin hydrolysis; acid production from glycerol,
mannose, arabinose, fructose, glucose, and xylose;
growth on MacConkey agar; motility; nitrate reduction;
and Simmon's citrate utilization. All eight isolates were
biochemically most consistent with R gilardii.
Antibiotic
Susceptibility
Testing was performed on the eight isolates using
an N I H custom break-point microdilution panel
p r e p a r e d by S e n s i t i t r e ( R a d i o m e t e r A m e r i c a ,
Westlake, Ohio). 3
Pulsed-field Gel Electrophoresis (PFGE)
Strain identification by PFGE was done using the
GenePath system (Bio-Rad Laboratories, Hercules,
Calif). The G e n e P a t h g r o u p 3 R e a g e n t Kit for
Pseudomonas and Enterobacter species was used; it uses
Spel as the restriction enzyme. In addition to Spel,
restriction enzymes Smal and Xbal were also studied.
The gels w e r e run u s i n g the Psu p r o g r a m for
Pseudomonas and the Enb program for Enterobacter to
determine the optimal program for Roseomonas. Gels
were stained with ethidium bromide and viewed with
a UV transilluminator. To achieve an optimal number
of bands for analysis, we found it necessary to restrict
first with Spel and then to perform a second restriction with Xbal using the Psu program.
Random Amplified
Polymorphic
DNA (RAPD) Analysis
Analysis by RAPD 4,5 is a polymerase chain reaction
(PCR)-based method for differentiating between
related strains. Short oligonucleotide primers (8 to 12
bases) of an arbitrarily chosen sequence are used to
amplify DNA extracted from an unknown organism.
Vol.:
lardii Infections
These primers will bind to many regions of the genome
resulting in the amplification of many fragments. The
PCR is performed under nonstringent conditions to
promote amplification of all possible regions. The
resulting PCR product pattern is visualized on an
ethidium bromide-stained agarose gel. The RAPD patterns are rapidly obtained, stable, and strain-specific.
For RAPD analysis of Roseomonas species, strains
were grown 48 hours on horse blood agar (Remel,
Lenexa, Kan). A single colony was removed using a
sterile swab and suspended in 1.0 mL 0.85% sterile
saline. Cell suspensions were centrifuged, and the
pellets were resuspended in 0.5 mL DNA Extraction
Reagent (Perkin Elmer, Branchburg, NJ). Samples
were placed in a heat block at 99°C for 15 minutes and
then cooled to room temperature. The conditions for
the PCR were as follows: 10 mmol/L (Tris)-HCl, pH
8.3; 50 m m o l / L KC1; 10 m m o l / L each deoxyadenosine t r i p h o s p h a t e , d e o x y c y t i d i n e t r i p h o s p h a t e ,
deoxyguanosine triphosphate, and deoxythymidine
triphosphate (Perkin Elmer); 0.4 u m o l / L primer; 3
umol/L MgCl 2 . 3 umol/L DNA extract; and 2.5 U Taq
DNA polymerase (Perkin Elmer) in 50-uL volume
overlaid with sterile mineral oil. Amplification was
performed in a Perkin Elmer GeneAmp PCR System
9600 programmed for 2 minutes at 95°C followed by
45 cycles of 1 minute at 95°C, 1 minute at 35°C, 2 minutes at 72°C, and, finally, 10 minutes at 72°C at the
end to allow extension to complete. Four different
primers were initially tried, ranging from 44% to 50%
guanine plus cytosine content. The primer found to
work best with this group of organisms was 5'-AGGATG-CTA-3', s y n t h e s i z e d at Research Genetics
(Huntsville, Ala). Amplification products were analyzed by electrophoresis in 1.4% agarose gels and
detected by staining with ethidium bromide.
RESULTS
Case Reports
Case 1—A 55-year-old woman with ovarian cancer
diagnosed in 1989 that recurred in 1990 was admitted
to the hospital in 1991 with fever and neutropenia
after treatment with paclitaxel. The only signs of focal
infection were perineal skin breakdown and vulvar
ulceration, and empiric treatment with imipenemcilastatin was started. Admission blood cultures
drawn through the central venous catheter and by
peripheral venipuncture grew R gilardii along with
Stenotrophomonas maltophilia, Chryseomonas luteola, and
Micrococcus species. Cultures on the following day
•No. 2
MICROBIOLOGY AND INFECTIOUS DISEASE
212
Original Article
were also positive with the same organisms, but thereafter were negative. No source of infection was documented, although the patient had used the same bottle
of saline solution to flush her catheter for several
weeks. She was treated with imipenem-cilastatin, vancomycin, gentamicin and trimethoprim-sulfamethoxazole for 10 days and recovered uneventfully.
Case 2—A 56-year-old man with advanced acquired
immunodeficiency syndrome was admitted to the
h o s p i t a l in 1991 b e c a u s e of refractory pain a n d
increased confusion. Admission blood cultures drawn
from the central venous catheter grew R gilardii,
although the peripheral venipuncture blood cultures
were sterile. Because of the do-not-resuscitate status
of the patient, no antibiotics were administered, but a
subsequent blood culture drawn through the catheter
was sterile. The patient died on the 11th hospital day
with no evidence of bacterial infection.
Case 3—A 5 1 - y e a r - o l d w o m a n w i t h m u l t i p l e
myeloma diagnosed in 1990 was referred to the NIH
in 1992 for b o n e m a r r o w t r a n s p l a n t a t i o n . She
received high-dose cyclophosphamide before transplantation, and, the following day, a temperature of
39°C developed with no other signs or symptoms.
Blood cultures d r a w n through the central venous
catheter initially grew R gilardii and Corynebacterium
species, CDC group F-2. Peripherally drawn blood
cultures on day 2 grew only the Corynebacterium
s p e c i e s , b u t b l o o d c u l t u r e s d r a w n t h r o u g h the
catheter 2 d a y s later g r e w b o t h o r g a n i s m s . The
catheter was removed, and a culture of the tip grew
both organisms. Her initial treatment regimen of vancomycin and gentamicin was changed to ceftriaxone
after susceptibility test results were k n o w n . She
recovered with no sequelae.
Case 4—A 53-year-old man with previously diagnosed non-Hodgkin's lymphoma was hospitalized
for a relapse involving the central nervous system,
requiring placement of an O m m a y a reservoir. In
1993, shortly after discharge from the hospital, fever
developed with no other symptoms. Blood cultures
d r a w n through the central v e n o u s catheter grew
Staphylococcus epidermidis, and he was admitted for
antibiotic therapy. Blood cultures obtained at time of
admission again grew S epidermidis, but also R gilardii.
He received a 10-day course of antibiotics and recovered uneventfully.
Case 5—A 29-year-old woman with ovarian cancer
diagnosed in 1992 was admitted to the hospital in
1993 w h e n she developed shaking chills without
fever, and tenderness around the exit site of the central venous catheter. Therapy with vancomycin and
ceftriaxone was started empirically. Admission blood
cultures grew multiple organisms, including
Acinetobacter Iwoffi, Corynebacterium
aquaticum,
Moraxella osloensis, Agrobacterium radiobacter, and
Micrococcus species, w h i l e the exit site g r e w
Staphylococcus aureus. On the second hospital day, cultures were still positive for A Iwoffi; on the fourth hospital day, the exit site was still positive for S aureus,
and additional blood cultures grew R gilardii and
Rhodotorula rubra. The catheter was removed, the
patient completed a 9-day course of antibiotics, and
subsequent blood cultures remained sterile.
Case 6—A 33-year-old w o m a n with breast cancer
diagnosed in 1993 developed a temperature of 39°C,
rigors, and back pain during a blood transfusion after
chemotherapy. She was admitted and treatment with
ceftriaxone was started. Blood cultures drawn both by
peripheral v e n i p u n c t u r e and t h r o u g h the central
TABLE 1. SUMMARY OF CLINICAL FEATURES OF PATIENTS WITH ROSEOMONAS
Case No.
1
2
3
4
5
6
7
Age (y)/Sex
Underlying Factors or Conditions
55/F
56/M
51 / F
53/M
29/F
33/F
50/F
Ovarian cancer, fever, neutropenia
Advanced acquired immunodeficiency syndrome, pain, confusion
Multiple myeloma, fever
Non-Hodgkins lymphoma, fever
Ovarian cancer, chills, tenderness at the catheter exit site
Breast cancer, fever, rigors during blood transfusion
Ovarian cancer, postsurgical fever
+ = positive; - = negative.
'Blood drawn through peripheral venipuncture.
Blood drawn through central venous catheter.
*Blood culture positive for two or more organisms.
+
A J C P " August 1997
GILARDII
CVCf
+
+
+
+
+
+
+
+
+
+
Mixed*
+
+
+
+
_
LEWIS ET AL
213
Roseomonas gi lardii Infections
v e n o u s c a t h e t e r grew R gilardii. Blood c u l t u r e s
obtained through the catheter remained positive for
Roseomonas species on the second and third hospital
d a y s . The fever a b a t e d p r o m p t l y , the c u l t u r e s
remained sterile, and she completed a 10-day course
of ceftriaxone.
Case 7—A 50-year-old woman with ovarian cancer
diagnosed in 1993 was admitted for surgical debulking of the tumor that year. After surgery, aphasia,
right-sided hemiparesis, and fever developed, and an
examination showed a cerebral infarction. Blood cultures obtained by peripheral venipuncture and from
the central v e n o u s catheter grew R gilardii. She
received intravenous ampicillin-sulbactam and gentamicin for 14 days, recovered, and was discharged.
Clinical Features
A brief summary of the patient characteristics is
given in Table 1. All seven patients with Roseomonas
species isolated from the bloodstream had clinically
significant underlying diseases; patients were predominantly female (5/7) and had solid tumors (5/7).
Five of seven had fever as the primary basis for
obtaining blood cultures, while another had chills
along with tenderness at the catheter exit site. All
patients had central venous catheters (Hickman or
Groshong catheters) and had positive blood cultures
d r a w n through the catheters. Only three of seven,
however, had concomitant positive blood cultures
w h e n blood w a s o b t a i n e d t h r o u g h p e r i p h e r a l
venipuncture. Four patients had polymicrobic positive blood cultures with a variety of different organisms. In two instances, the catheter was removed
because of concerns of continuing positive blood cultures despite antibiotic treatment. With the exception
of the patient with acquired immunodeficiency syndrome who was not treated with antibiotics, all other
patients cleared their bloodstream, and the patients
were considered successfully treated. The organisms
showed susceptibility to many antibiotics by in vitro
testing, so that a variety of different antibiotic regimens were used, including ceftriaxone, imipenem,
gentamicin, and ampicillin-sulbactam.
Organism
Identification
Original identification of the eight isolates as CDC
pink-coccoid group III was based on the following key
reactions, which helped distinguish these strains from
Methylobacterium extorquens and pink-coccoid groups I,
II, and IV2: acid production from glucose and mannitol, growth on Simmon's citrate agar, and lack of
motility. Pink-coccoid group III was the most common
group in CDC's collection of strains (79/156, or 51%).
The eight strains were subsequently reidentified
using the newer criteria of Rihs et al,1 who proposed
three new species (R gilardii, R cervicalis, and R faunae)
in addition to three unnamed genomospecies (4, 5, and
6). It was not clear from their article whether each of the
previously designated pink-coccoid group classifications corresponded to a particular species or genomospecies, although the biochemical patterns of groups II
and III were closest to the characteristics provided for R
gilardii. Our eight strains all had virtually identical biochemical reactions that were most consistent with R
gilardii. The isolates differed from M extorquens because
they were nonmotile, produced acid from mannitol,
and grew on Simmon's citrate agar. They likewise differed from the other species of Roseomonas described by
Rihs et al primarily on the basis of acid production from
glycerol and mannitol and lack of motility and esculin
hydrolysis. A summary of the biochemical reactions for
pink-coccoid group III, R gilardii, and our eight isolates
are given in Table 2.
Antibiotic
Susceptibilities
The eight s t r a i n s were h o m o g e n e o u s in their
antibiotic susceptibilities with a few exceptions. All
isolates were susceptible to ceftriaxone, imipenem,
amikacin, gentamicin, tobramycin, ciprofloxacin, and
tetracycline, while all were resistant to cefoxitin, ceftazidime, and piperacillin. Our results agreed with
those done on the CDC isolates, 1 except for susceptibility to ceftriaxone; only 4% of those R gilardii isolates were susceptible, while 100% of ours were susceptible. The minimum inhibitory concentrations of
our isolates for ceftriaxone were less than 8 ug/mL,
despite minimum inhibitory concentrations of more
than 32 u g / m L for ceftazidime. This unusual discrepancy between ceftriaxone and ceftazidime susceptibility may suggest that these results should be interpreted with caution, although several of our patients
were, in fact, treated successfully with ceftriaxone
Other antibiotics that showed variable susceptibilities
and how they compared with CDC results are shown
in Table 3.
Strain Identification
by PFGE and RAPD
It was difficult to obtain good patterns for analysis
by PFGE, probably because of interference from the
Vol. 108 • No. 2
[-
214
M I C R O B I O L O G Y A N D I N F E C T I O U S DISEASE
Original Article
TABLE 2. IDENTIFICATION CHARACTERISTICS OF ROSEOMONAS
GILARDII AND CDC PINK COCCOID GROUP III
Biochemical Test
Pink Coccoid III" (n = 79)
R gilardii^ (n = 23)
National Institutes
Oxidase
MacConkey agar
Nitrate reduction
Esculin hydrolysis
Simmon's citrate
Motility
Acid from
Arabinose
Fructose
Galactose
Glucose
Glycerol
Mannitol
Mannose
Xylose
51*
82
23
0
93
11
V
91
4
0
+§
35
100
12
0
0
88
0
NA
99
NA
89
NA
100
NA
74
65
+
70
V
100
56
4
V
100
100
100
100
75
100
0
100
of Health (n = 8)
CDC = Centers for Disease Control and Prevention (Atlanta, Ga); + = positive; NA = data not available; V = variable reactions.
'Data from Wallace et al. 2
•Data from Rihs et al. 1
iData are given as percentage of cultures that were positive.
^Specific number not given.
mucoid slime produced by the organisms. Our best
results were obtained by growing the organisms in
liquid media for 2 days and allowing most of the
mucoid material to settle out to the bottom of the
tube. Two milliliters of broth culture from the upper
half of the tube was then used for DNA extraction.
Five of the eight isolates were distinctly different
from each other in number and size of bands (Fig 1).
Three isolates, C, E, and G, seemed to have identical
PFGE patterns, although there was no traditional epidemiologic evidence of patient-to-patient spread or
contamination from a common hospital source. Of the
three similar strains, one was a blood isolate recovered
in 1991, while the other two isolates were recovered in
1993. These three strains also had similar antibiotic
susceptibilities, so that neither their biochemical profile nor antibiograms were sufficient to suggest that
these were different strains. Analysis of these strains
by RAPD, however, showed very different patterns for
each of the isolates, including isolates C, E, and G that
had seemed identical by PFGE (Fig 2).
DISCUSSION
The natural reservoir of Roseomonas species remains
undocumented. Although the type strain of R gilardii
was isolated from potable water, most of the CDC collection of group III strains were from blood (42/79, or
53%), as were seven of our eight isolates. The various
species of Roseomonas, including R gilardii, have been
isolated from a wide variety of human sources, raising
the likelihood that some species may be a part of the
normal skin or gastrointestinal flora of humans.
The earlier literature reveals only rare reports of
the pink-coccoid bacteria causing clinically significant
infection in humans. The first series, by Gilardi and
Faur, 6 described 21 strains of pink pigment-producing colonies of gram-negative rods, seven of which
were designated "an unnamed taxon" and distinct
from p r e v i o u s l y d e s c r i b e d species. In 1988,
Odugbesni et al 7 reported isolation of an unidentified
pink-pigmented bacterium from the blood of a 9month-old Nigerian boy with fever and cough. In
1989, two cases of bacteremia with similar organisms
were described in patients with clinically significant
TABLE 3. ANTIMICROBIAL AGENTS WITH VARIABLE
SUSCEPTIBILITY RESULTS
Antimicrobial
Agent
Ampicillin
Ticarcillin
Ampicillin/sulbactam
Cephalothin
Aztreonam
Trimethoprim/sulfamethoxazole
National
Institutes
of Health'
Rihs et allf
1/8(12.5)
4 / 8 (50)
3/8 (37.5)
1/8(12.5)
4 / 8 (50)
4 / 8 (50)
17.4
30.4
65.2
0
0
8.7
'Data are given as number positive/number tested (percentage susceptible).
f
Data are given as percentage susceptible.
AJCP • August 1997
LEWIS ET AL
215
Roseomonas gilardii Infections
underlying diseases. 8 One of these patients, a 60-yearold man hospitalized because of a pancreatic abscess,
died during the bacteremic episode before the organism w a s isolated and identified. Most recently,
Barzaga et al 9 reported recovering a pink-pigmented
bacterium from the blood of a patient with end-stage
renal disease who became hypotensive during
hemodialysis and died the following day.
Our series of patients with blood cultures positive for
R gilardii, confirmed that this organism has the potential
to cause central venous catheter-associated bacteremia
in immunocompromised patients. Six of the seven
patients with bacteremia that we described were adult
oncology patients, while the remaining patient had endstage human immunodeficiency virus infection. In cases
2, 4, and 5, the Roseomonas organism was detected in
only one blood culture drawn through a central venous
catheter for each patient, while in case 3, although two
blood cultures on subsequent days were positive, they
were both drawn through the catheter. In cases 3, 4, and
5, although there were no positive peripherally drawn
blood cultures, the patients were febrile, and the physicians elected to treat in each instance. A noteworthy
aspect of these case histories was the frequency of
polymicrobic infection, possibly indicating significant
lapses in management of the sterile catheter. However,
only in Case 1 could a specific event be identified that
may have led to catheter contamination. The polymicrobic episodes showed a variety of unusual or low-virulence pathogens (Corynebacterium CDC Group F2, S epidermidis, A hvoffi, A radiobacter, C aquaticum, R rubra, C
luteola, S maltophilia, and Micrococcus species), which
A
B
C
D
E
F
G
H
suggests skin or contaminated water as possible sources
of infection. In the two instances in which removal of the
catheters was believed advisable because of persistent
positive blood cultures, polymicrobic cultures had
been obtained. In the other five cases, however, antibiotic therapy without catheter removal was used successfully. Case 2 may represent transient catheter colon i z a t i o n w i t h the o r g a n i s m b e c a u s e it w a s not
identified in subsequent cultures.
Identification of a mucoid pink pigmented organism as a Roseomonas o r g a n i s m r a t h e r than a
Methylobacterium organism can be made by testing for
the absorption of long-wave UV light. Colonies of
Methylobacterium mesophilicum show absorption of
l o n g - w a v e UV light, while those of Roseomonas
species do not. 1 To identify the individual species of
Roseomonas, however, is more difficult because the
acidification of different carbohydrates is needed to
differentiate the newly proposed species. In our experience, some of the strains take prolonged incubation
to determine their biochemical characteristics, and,
often, the reactions are weak and characteristically
borderline. In particular, determination of sugar patterns may vary depending on the type of medium
A
B
C
D
E
F
G
H
I
I
1356 bp —
603 bp 292Kb -
194 bp —
48.5 Kb -
FIG 1. Pulsed-field gel electrophoresis of Spel- plus Xbal-digested
g e n o m i c DNA from the eight Roseomonas isolates. Lane A,
Molecular size standard in kilobases (kbs; \ DNA ladder); lanes B
through I, patient isolates.
FIG 2. Profiles of the random amplified polymorphic DNA analyses
of the eight Roseomonas isolates. Lane A, Molecular size standards
in base pairs (bps; X/Hind III-oX174/Hae III marker); lanes B
through I, patient isolates.
Vol. 108 • No. 2
216
MICROBIOLOGY AND INFECTIOUS DISEASE
Original Article
used and the length of incubation. Acid production
from glycerol and mannitol and lack of motility were
the most useful tests for distinguishing R gilardii from
the other species.
Because most of our R gilardii isolates were from
blood and were often associated with intravenous
catheter colonization, we investigated the usefulness
of PFGE to determine whether our isolates could be a
single strain that had originated from a common
source, particularly because the organism is relatively
uncommon. The PFGE method that we used showed
us that five of our eight isolates had distinctly different PFGE patterns, while three looked identical. We
suspected that the use of PFGE with the restriction
enzymes that were tried (Spel, Xbal, and Smal) was
not robust enough to be used reliably for strain identification. When these eight isolates were tested as
described by a RAPD procedure, each strain seemed
to be distinctly different, including the three isolates
that seemed identical by PFGE. The RAPD is a PCRbased assay that may be performed using small
a m o u n t s of DNA p r e p a r e d from c r u d e bacterial
lysates 4 and is not affected by DNA modification systems that may hinder restriction-based DNA analyses
such as PFGE. For Roseomonas species, RAPD was
more discriminatory than PFGE, and its reliability
was supported by reproducible patterns when the isolates were retested 1 month later.
Although these organisms are unusual causes of
infection, they should not be disregarded when isolated
from an immunocompromised or debilitated host. The
infections in the patients treated in our series responded
well, and the patients recovered with no sequelae of
infection. Sophisticated molecular techniques were
required to identify our isolates as distinct and not a
single strain producing nosocomial infections.
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AJCP • August 1997