Previous Article | Next Article 
Clinical and Diagnostic Laboratory Immunology, May 2001, p. 632-636, Vol. 8, No. 3
1071-412X/01/$04.00+0 DOI: 10.1128/CDLI.8.3.632-636.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Elastase Deficiency Phenotype of Pseudomonas
aeruginosa Canine Otitis Externa Isolates
Shana R.
Petermann,1
Curt
Doetkott,2 and
Lynn
Rust1,*
Department of Veterinary and Microbiological
Sciences1 and Information Technology
Services,2 North Dakota State University,
Fargo, North Dakota 58105
Received 28 August 2000/Returned for modification 25 January
2001/Accepted 14 February 2001
 |
ABSTRACT |
Pseudomonas aeruginosa veterinary isolates were assayed
for elastase and total matrix protease activity. The elastase activity of canine ear isolates was much less than that of strain PAO1 and that
of all other veterinary isolates (P < 0.0001). The
results indicate that canine ear isolates have a distinct elastase phenotype.
| |
TEXT |
Pseudomonas aeruginosa
secretes several toxins and enzymes that enhance its virulence. Among
the enzymes are three well-characterized proteases: two elastases (LasA
and LasB) and an alkaline protease (AprA) (for reviews, see references
18 and 23). Two additional proteases have been reported:
LasD (21) and protease IV (6). Each of these
proteases has broad substrate specificity; in addition, the
proteases often act synergistically to cleave connective tissues and
immune system components. Connective tissues degraded by P. aeruginosa proteases include elastin, mediated by LasA and
LasB, and collagen, mediated by alkaline protease and elastases
(18, 23). Proteases, either individually or
synergistically, mediate Hageman factor activation (11),
immunoglobulin and complement degradation (5, 9, 13, 25),
cytokine inactivation (22), and host protease activation
(32).
The contribution of P. aeruginosa proteases to the
pathogenesis of acute infections is well documented (for a review, see reference 19). In particular, Tang et al.
(31) found that a genetically defined, protease-deficient
strain was virtually avirulent compared to the parental strain in a
mouse model of acute pneumonia. Interestingly, the protease-deficient
strain and the parental strain colonized similar numbers of mice in
this study (31).
The contribution of proteases to chronic infection is more
controversial. The role of P. aeruginosa proteases in
chronic infection is best studied in cystic fibrosis (for reviews, see
references 3, 4, 10, 16, and 30). P. aeruginosa
proteases and lasB and lasA mRNA have been
detected in cystic fibrosis lung sputa (14, 27); however,
other studies implicate host neutrophil elastase over bacterial
elastases in cystic fibrosis lung pathology (2, 33).
Reflecting the relative contribution of proteases to virulence,
P. aeruginosa strains express levels of proteases that vary with isolation site and disease (34). The mucoid strains
that characterize cystic fibrosis isolates are known to secrete less elastase than nonmucoid strains (20, 34). Woods et al.
(34) found that the frequency of protease production from
cystic fibrosis isolates was significantly lower than that from
isolates from other sites. In contrast, the levels of protease activity
from blood isolates and elastase from acute pneumonia sputum isolates were significantly higher than levels from other infection sites (34).
Most of the research regarding P. aeruginosa virulence
factor production in disease has focused on human serology, isolates, or samples. In contrast, little is known about the virulence phenotypes of animal isolates. In this study, we surveyed animal intestinal and
fecal P. aeruginosa isolates for protease activity. In
addition, we sought to determine if P. aeruginosa associated
with acute or chronic animal diseases displayed protease phenotypes
comparable to those displayed by P. aeruginosa
associated with acute or chronic human diseases. We used colorimetric
assays to detect in vitro elastase and total matrix protease activities
semiquantitatively and included well-characterized human wound isolate
PAO1 (12) as an internal control. Interestingly,
while total matrix protease activity among animal isolates was
comparable to that of P. aeruginosa PAO1, we found that
P. aeruginosa isolates from canine ear infections exhibited significantly lower elastase activity when cultured in
vitro than strain PAO1 or isolates from all other animal sources.
P. aeruginosa isolates were collected at the North Dakota
Veterinary Diagnostic Laboratories over the course of 4 years. Isolates were presumptively identified as P. aeruginosa based on
colony morphology, odor, and reactions (k/k) on triple sugar iron agar slants. Suspect colonies were inoculated onto King B agar and grown
overnight at 37°C. Isolates displaying the typical fluorescence of
P. aeruginosa were positively identified using Sensititre
technology (Accumed International, Inc., Westlake, Ohio) with AP80-VET
Gram-ID plates (Trek Diagnostic Systems, Inc., Westlake, Ohio). All
isolates were typed as P. aeruginosa with 98% or greater probability.
Forty-four isolates were assayed for protease and elastase activity; of
these, 16 were from canine chronic ear infections. The hosts and tissue
sources of the noncanine isolates are given in Table
1. About 30% (13 of 44) were
characterized as normal flora of the gastrointestinal tract unrelated
to the diagnosis, 27% (12 of 44) were characterized as causative
agents or secondary pathogens of acute infection, and 43% (19 of 44)
were characterized as causative agents or secondary pathogens of
chronic infection. Of the isolates from chronic infections, 84% (16 of
19) were from canine ear infections of otherwise healthy pets.
Total matrix protease activity.
P. aeruginosa PAO1
and veterinary isolates were cultured in 10 ml of Luria-Bertani broth
at 37°C overnight and subcultured by inoculating fresh, prewarmed
broth to an optical density at 640 nm of 0.001. Culture densities from
early-stationary-phase secondary cultures were read at 640 nm to ensure
comparable levels of growth between isolates and P. aeruginosa PAO1. The culture was harvested, and the supernatant
was clarified by centrifugation at 20,800 × g for 5 min. Two microliters of culture supernatant was added to triplicate
tubes of 20 mg of hide powder azure (Sigma Chemical Co., St. Louis,
Mo.) suspended in 2 ml of 10 mM sodium-HEPES (pH 7.5)-0.5 mM
CaCl2 and rotated for 2 h at 37°C. An assay tube without
culture supernatant was rotated to subtract background absorbance.
Insoluble substrate was pelleted by centrifugation at 150 × g for 15 min. Absorbance of the assay supernatant was read at 595 nm. The average and sample standard deviation were calculated and
expressed as a fraction of the triplicate assay average of the internal
control, P. aeruginosa PAO1. Strains exhibiting low levels
or an absence of matrix protease activity were typically cultured for
activity twice (six or more replicate assays).
The results of matrix protease activity assays of canine otitis externa
isolates are shown in Fig.
1. An
absorbance of less
than half that of
P. aeruginosa PAO1 in
the hide powder azure
assay corresponds to less than 10% of the
activity of strain PAO1,
based on assays of a serial dilution of PAO1
supernatant. In all,
25% (4 of 16) of the canine ear isolates
exhibited less than half
the assay absorbance of
P. aeruginosa PAO1 in the hide powder
azure assay, compared to only
3.5% (1 of 29) of isolates from
other sources showing low matrix
protease activity. Fisher's exact
test (
1) yields a
two-sided
P value of 0.0468, leading us to
marginally reject
the null hypothesis of equal proportions of
isolates with low matrix
protease activity at the 95% confidence
level. Thus, a higher
proportion of canine ear isolates than of
isolates from other sources
may have low matrix protease activity,
but this difference in
proportions was not significant.
View larger version (10K):
[in this window]
[in a new window]
|
FIG. 1.
Distributions of total matrix protease activity from
canine ear isolates and from all other animal isolates. Activity is
hide powder azure absorbance at 595 nm relative to hide powder azure
absorbance of strain PAO1 (defined as 1). (A) Box plots of the
distributions. Top, internal, and bottom lines of the boxes, 75th,
50th, and 25th percentiles, respectively; dot in each box, mean of the
distribution. (B) Scatter plots of the distributions. Open circles,
values for individual isolates.
|
|
The distributions of matrix protease activity for canine ear isolates
and isolates from other sources are represented by box
plots (Fig.
1A)
and scatter plots (Fig.
1B). This figure suggests
that the matrix
protease activity for isolates from canine sources
is more variable
than that for isolates from other sources but
that the average activity
levels for isolates from the two sources
are equivalent. We compared
mean matrix protease activity between
isolates from canine sources and
from other sources using Student's
t tests
(
26). Hypothesis tests confirm these impressions, as
we
reject the null hypothesis of equal variances between isolates
from the
two sources (
F' = 5.32;
P < 0.0001) but we do not
reject
the null hypothesis of equal means (
t = 0.32;
P = 0.7538).
Elastase activity.
P. aeruginosa PAO1 and veterinary
isolates were cultured and supernatant was clarified as described
above. Two microliters of culture supernatant was added to triplicate
tubes of 20 mg of elastin-Congo red (Elastin Products, Inc.,
Owensville, Mo.) suspended in 2 ml of 10 mM sodium phosphate buffer, pH
7.0, and rotating the mixture overnight at 37°C (24).
The absorbance of the assay supernatant was read at 495 nm after
subtracting background absorbance. Due to the prolonged incubation of
this assay mixture, the comparisons with P. aeruginosa PAO1
elastase activity are not intended to reflect a linear relationship but merely relative absorbance readings of the assay. Canine ear isolates were assayed twice or more in independent experiments. The highest absorbance reading of each isolate relative to P. aeruginosa
PAO1 was used for statistical analysis.
In all, 75% (12 of 16) of the canine ear isolates
exhibited less than half the assay absorbance of
P. aeruginosa PAO1, compared
to only 10.3% (3 of 29) of the isolates
from other sources showing
low elastase activity (Fig.
2). We used Fisher's exact test
(
1)
to test the null hypothesis of equal proportions of
canine isolates
versus other isolates having low elastase activity
(where low
elastase activity is defined as less than one-half the assay
absorbance
of
P. aeruginosa PAO1). Fisher's exact test
yields a two-sided
P value of 0.00002, leading us to
strongly reject the null hypothesis
of equal proportions of isolates
with low elastase activity at
the 95% confidence level.
View larger version (10K):
[in this window]
[in a new window]
|
FIG. 2.
Distributions of elastase activity from canine ear
isolates and from all other animal isolates. Activity is elastin-Congo
red absorbance at 495 nm relative to elastin-Congo red absorbance of
strain PAO1 (defined as 1). (A) Box plots of the distributions. Top,
internal, and bottom lines of the boxes, 75th, 50th, and 25th
percentiles, respectively; dot in each box, mean of the distribution.
(B) Scatter plots of the distributions. Open circles, values for
individual isolates.
|
|
The distributions of elastase activity for isolates from canine and
other sources are represented by box plots (Fig.
2A) and
scatter plots
(Fig.
2B). In contrast to the total matrix protease
results, the
elastase activities for isolates from canine and
other sources show
approximately the same amounts of variability
but the average activity
levels for isolates from the canine source
appear to be somewhat lower
than those for isolates from other
sources. We compared mean elastase
activities between isolates
from canine and other sources using
Student's
t tests (
26).
Hypothesis tests
confirm these observations as we do not reject
the null hypothesis of
equal variances between the two sources
(
F' = 1.10;
P = 0.8029) but we do reject the null hypothesis of
equal means
(
t = 5.68;
P < 0.0001). In addition to having a
lower
mean than isolates from other sources, canine ear isolates
cluster
at high and low levels in a bimodal fashion (Fig.
2B). This
clustering
indicates that a subpopulation of canine ear isolates has
typical
levels of elastase activity, while the majority of isolates
exhibit
low activity levels and lower the mean for canine ear isolates
as a
population.
Twelve isolates that gave elastin-Congo red readings of <0.1
absorbance units at 495 nm were further characterized for an
elastase-negative phenotype. Isolates were inoculated onto elastin
nutrient agar, a more sensitive but qualitative assay for elastase
activity (
24). The zones of elastolysis were compared to
those
for strain PAO1 and strain PAO-R1 (an elastase-negative strain
[
7]). Lack of zones indicated an elastase-negative
phenotype.
Only 3 of the 12 isolates, 2 of them canine ear isolates,
were
elastase negative (data not shown). One canine ear isolate was
elastase negative yet exhibited low levels of matrix protease
activity,
while the other two elastase-negative isolates were
also negative for
matrix protease
activity.
The elastase-negative isolates may have null mutations in the
structural coding region or promoter or in regulatory or processing
genes. Alternatively, the elastases may be produced but not active
on
the elastin-Congo red substrate. Likewise, several possibilities
for
low elastase activity exist. These isolates may produce or
secrete
elastase at suboptimal levels due to an alteration in
one of the
elastase regulatory or secretion pathways. An alteration
in an elastase
pathway as opposed to an alkaline protease pathway
may account for the
phenotypic difference between canine ear isolates
and other animal
isolates. Alternatively, the elastase-deficient
isolates may produce a
less active elastase enzyme(s). While mucoidy
has been inversely
correlated with protease production (
17,
20), it is worth
noting that none of the canine ear isolates
exhibited a mucoid
phenotype in
vitro.
These possibilities raise the question of why canine ear isolates would
harbor an elastase phenotype distinct from that of
most other isolates.
First, host factors may provide the stimuli
to induce or repress
expression of the various virulence factors
from a population of
diverse, pluripotent
P. aeruginosa strains.
Adaptation to
the infection site may affect virulence factor production
from early in
vitro cultures. In particular, Hamood et al. (
8)
found
that elevated exoenzyme S production from wound and urinary
tract
infection isolates was subsequently reduced by continuous
in vitro
subculturing. Second, as suggested by Sundström et al.
(
29), a subset of
P. aeruginosa strains may
colonize particular
infection sites: strains isolated from human
external otitis exhibited
distinctive biochemical profiles and
pigmentation compared to
those isolated from varicose ulcers and
urinary tract infections.
In addition, Sundström et al.
(
28) found that the adhesion
of
P. aeruginosa
external otitis isolates to guinea pig epithelial
cells was
significantly increased compared to that of isolates
from leg ulcers or
urinary tract infections. The authors conclude
that
P. aeruginosa strains causing human external otitis can be
considered
as having a particular phenotype. Third, strain selection
may be at the
level of the
P. aeruginosa reservoir, i.e., strain
adaptation to a water environment, as suggested by Sundström
et
al. (
29). In contrast to our results for canine ear
isolates,
however, Sundström et al. (
28) found no
apparent difference
in elastolysis between human external otitis, leg
ulcer, and urinary
tract infection isolates. Human external otitis and
canine external
otitis would likely arise from contact with similar
freshwater
reservoirs, and the apparent difference in elastolysis
between
isolates of the two hosts makes the possibility of a common,
reservoir-adapted
phenotype less likely. Finally, a phenotype that
includes suboptimal
elastase production may be better adapted to the
canine ear and
able to compete with other
P. aeruginosa
strains and normal flora
for colonization. In this case, the elastase
deficiency is likely
secondary to the adaptive characteristic or
possibly reflects
an intracellular role of elastase (
15).
Ongoing research is
aimed at discriminating among these
possibilities.
| |
ACKNOWLEDGMENTS |
We thank the North Dakota Veterinary Diagnostic Laboratory,
especially Darlene Krogh, Ronda DeVold, and Lynn Schaan, for
P. aeruginosa isolation and preliminary identification
and for instruction on the use of the Sensititre. We also thank Heather
Hertz, Rusty Rybolt, Karen Lone Fight, and Troy Wegman for protease
assays and record retrieval.
This work was funded by the North Dakota Agricultural Experiment
Station and NIH grant 1 R15 AI46506-01.
| |
FOOTNOTES |
*
Corresponding author. Mailing address: Department of
Veterinary and Microbiological Sciences, North Dakota State University, P.O. Box 5406, Fargo, ND 58105. Phone: (701) 231-7848. Fax: (701) 231-7514. E-mail: Lynn_Rust{at}ndsu.nodak.edu.
| |
REFERENCES |
| 1.
|
Daniel, W. W.
1978.
Applied nonparametric statistics.
Houghton Mifflin Company, Boston, Mass.
|
| 2.
|
Delacourt, C.,
M. Le Bourgeois,
M. P. D'Ortho,
C. Doit,
P. Scheinmann,
J. Navarro,
A. Harf,
D. J. Hartmann, and C. Lafuma.
1995.
Imbalance between 95 kDa type IV collagenase and tissue inhibitor of metalloproteinases in sputum of patients with cystic fibrosis.
Am. J. Respir. Crit. Care Med.
152:765-774[Abstract].
|
| 3.
|
Döring, G.
1987.
Significance of Pseudomonas aeruginosa virulence factors in acute and chronic Pseudomonas aeruginosa infections.
Infection.
15:47-50[CrossRef][Medline].
|
| 4.
|
Döring, G.
1997.
Cystic fibrosis respiratory infections: interactions between bacteria and host defence.
Monaldi Arch. Chest Dis.
52:363-366[Medline].
|
| 5.
|
Döring, G.,
H.-J. Obernesser, and K. Botzenhart.
1981.
Extracellular toxins of Pseudomonas aeruginosa. II. Effect of two proteases on human immunoglobulins IgG, IgA and secretory IgA.
Zentbl. Bakteriol. Hyg. 1. Abt. Orig. A
249:89-98.
|
| 6.
|
Engel, L. S.,
J. M. Hill,
A. R. Caballero,
L. C. Green, and R. J. O'Callaghan.
1998.
Protease IV, a unique extracellular protease and virulence factor from Pseudomonas aeruginosa.
J. Biol. Chem.
273:16792-16797[Abstract/Free Full Text].
|
| 7.
|
Gambello, M. J., and B. H. Iglewski.
1991.
Cloning and characterization of the Pseudomonas aeruginosa lasR gene, a transcriptional activator of elastase expression.
J. Bacteriol.
173:3000-3009[Abstract/Free Full Text].
|
| 8.
|
Hamood, A. N.,
J. A. Griswold, and C. M. Duhan.
1996.
Production of extracellular virulence factors by Pseudomonas aeruginosa isolates obtained from tracheal, urinary tract, and wound infections.
J. Surg. Res.
61:425-432[CrossRef][Medline].
|
| 9.
|
Heck, L. W.,
P. G. Alarcon,
R. M. Kulhavy,
K. Morihara,
M. W. Russell, and J. F. Mestechky.
1990.
Degradation of IgA proteins by Pseudomonas aeruginosa elastase.
J. Immunol.
144:2253-2257[Abstract].
|
| 10.
|
Hoiby, N.,
S. S. Pedersen,
E. T. Jensen,
T. Pressler,
G. H. Shand,
A. Kharazmi, and G. Döring.
1990.
Immunology of Pseudomonas aeruginosa infection in cystic fibrosis.
Acta Univ. Carol. Med.
36:16-21.
|
| 11.
|
Holder, I. A., and A. N. Neely.
1989.
Pseudomonas elastase acts as a virulence factor in burned hosts by Hageman factor-dependent activation of the host kinin cascade.
Infect. Immun.
57:3345-3348[Abstract/Free Full Text].
|
| 12.
|
Holloway, B. W.
1955.
Genetic recombination in Pseudomonas aeruginosa.
J. Gen. Microbiol.
13:572-581[Abstract/Free Full Text].
|
| 13.
|
Hong, Y., and B. Ghebrehiwet.
1992.
Effect of Pseudomonas aeruginosa elastase and alkaline protease on serum complement and isolated components C1q and C3.
Clin. Immunol. Immunopathol.
62:133-138[CrossRef][Medline].
|
| 14.
|
Jaffar-Bandjee, M. C.,
A. Lazdunski,
M. Bally,
J. Carrère,
J.-P. Chazaletter, and C. Galabert.
1995.
Production of elastase, exotoxin A, and alkaline protease in sputa during pulmonary exacerbation of cystic fibrosis in patients chronically infected by Pseudomonas aeruginosa.
J. Clin. Microbiol.
33:924-929[Abstract].
|
| 15.
|
Kamath, S.,
V. Sapatral, and A. M. Chakrabarty.
1998.
Cellular function of elastase in Pseudomonas aeruginosa: role in the cleavage of nucleoside diphosphate kinase and in alginate synthesis.
Mol. Microbiol.
30:933-941[CrossRef][Medline].
|
| 16.
|
Kharazmi, A.
1991.
Mechanisms involved in the evasion of the host defence by Pseudomonas aeruginosa.
Immunol. Lett.
30:201-205[CrossRef][Medline].
|
| 17.
|
Mohr, C. D.,
L. Rust,
A. M. Albus,
B. H. Iglewski, and V. Deretic.
1990.
Expression patterns of genes encoding elastase and controlling mucoidy: coordinate regulation of two virulence factors in Pseudomonas aeruginosa isolates from cystic fibrosis.
Mol. Microbiol.
4:2103-2110[CrossRef][Medline].
|
| 18.
|
Morihara, K., and J. Y. Homma.
1985.
Pseudomonas proteases, p. 41-79.
In
I. A. Holder (ed.), Bacterial enzymes and virulence. CRC Press, Boca Raton, Fla.
|
| 19.
|
Nicas, T. I., and B. H. Iglewski.
1985.
The contribution of exoproducts to virulence of Pseudomonas aeruginosa.
Can. J. Microbiol.
31:387-392[Medline].
|
| 20.
|
Ohman, D. E., and A. M. Chakrabarty.
1982.
Utilization of human respiratory secretions by mucoid Pseudomonas aeruginosa of cystic fibrosis origin.
Infect. Immun.
37:662-669[Abstract/Free Full Text].
|
| 21.
|
Park, S., and D. R. Galloway.
1995.
Purification and characterization of LasD: a second staphylolytic proteinase produced by Pseudomonas aeruginosa.
Mol. Microbiol.
16:263-270[CrossRef][Medline].
|
| 22.
|
Parmely, M.,
A. Gale,
M. Clabaugh,
R. Horvat, and W. W. Zhou.
1990.
Proteolytic inactivation of cytokines by Pseudomonas aeruginosa.
Infect. Immun.
58:3009-3014[Abstract/Free Full Text].
|
| 23.
|
Parmely, M. J.
1993.
Pseudomonas metalloproteases and the host-microbe relationship, p. 79-94.
In
R. Fick (ed.), Pseudomonas aeruginosa the opportunist: pathogenesis and disease. CRC Press, Boca Raton, Fla.
|
| 24.
|
Rust, L.,
C. M. Messing, and B. H. Iglewski.
1994.
Elastase assays.
Methods Enzymol.
235:554-562[Medline].
|
| 25.
|
Schultz, D. R., and K. D. Miller.
1974.
Elastase of Pseudomonas aeruginosa: inactivation of complement components and complement-derived chemotactic and phagocytic factors.
Infect. Immun.
10:128-135[Abstract/Free Full Text].
|
| 26.
|
Steel, R. G. D., and J. H. Torrie.
1980.
Principles and procedures of statistics, 2nd edition
McGraw-Hill Book Company, New York, N.Y.
|
| 27.
|
Storey, D. G.,
E. E. Ugack,
I. Mitchell, and H. R. Rabin.
1997.
Positive correlation of algD transcription to lasB and lasA transcription by populations of Pseudomonas aeruginosa in the lungs of patients with cystic fibrosis.
Infect. Immun.
65:4061-4067[Abstract].
|
| 28.
|
Sundström, J.,
C. Agrup,
G. Kronvall, and B. Wretlind.
1997.
Pseudomonas aeruginosa adherence to external auditory canal epithelium.
Arch. Otolaryngol. Head Neck Surg.
123:1287-1292.
|
| 29.
|
Sundström, J.,
K. Jacobson,
E. Munck-Wikland, and S. Ringertz.
1996.
Pseudomonas aeruginosa in otitis externa: a particular variety of bacteria?
Arch. Otolaryngol. Head Neck Surg.
122:833-836.
|
| 30.
|
Suter, S.
1994.
The role of bacterial proteases in the pathogenesis of cystic fibrosis.
Am. J. Respir. Crit. Care Med.
150:S118-S122.
|
| 31.
|
Tang, H. B.,
E. DiMango,
R. Bryan,
M. Gambello,
B. H. Iglewski,
J. B. Goldberg, and A. Prince.
1996.
Contribution of specific Pseudomonas aeruginosa virulence factors to pathogenesis of pneumonia in a neonatal mouse model of infection.
Infect. Immun.
64:37-43[Abstract].
|
| 32.
|
Twining, S. S.,
S. E. Kirschner,
L. A. Mahnke, and D. W. Frank.
1993.
Effect of Pseudomonas aeruginosa elastase, alkaline protease, and exotoxin A on corneal proteinases and proteins.
Investig. Ophthalmol. Vis. Sci.
34:2699-2712[Abstract/Free Full Text].
|
| 33.
|
Venaille, T. J.,
G. Ryan, and B. W. Robinson.
1998.
Epithelial cell damage is induced by neutrophil-derived, not pseudomonas-derived, proteases in cystic fibrosis sputum.
Respir. Med.
92:233-240[CrossRef][Medline].
|
| 34.
|
Woods, D. E.,
M. S. Schaffer,
H. R. Rabin,
G. D. Campbell, and P. A. Sokol.
1986.
Phenotypic comparison of Pseudomonas aeruginosa strains isolated from a variety of clinical sites.
J. Clin. Microbiol.
24:260-264[Abstract/Free Full Text].
|
Clinical and Diagnostic Laboratory Immunology, May 2001, p. 632-636, Vol. 8, No. 3
1071-412X/01/$04.00+0 DOI: 10.1128/CDLI.8.3.632-636.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Top
Abstract
Text
