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Journal of Clinical Microbiology, December 1999, p. 4163-4166, Vol. 37, No. 12
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Posttreatment Follow-Up of Brucellosis by PCR
Assay
Pilar
Morata,1
María Isabel
Queipo-Ortuño,1
José
María
Reguera,2
Miguel
Angel
García-Ordoñez,2
Cristina
Pichardo,3 and
Juan de Dios
Colmenero2,*
Department of Biochemistry and Molecular
Biology, Faculty of Medicine, University of
Malaga,1 and Infectious Diseases Unit,
Department of Internal Medicine, "Carlos Haya"
Hospital,2 Malaga, and Infectious
Diseases Service, "Virgen del Rocío" University Hospital,
Seville,3 Spain
Received 14 May 1999/Returned for modification 3 July 1999/Accepted 21 August 1999
 |
ABSTRACT |
In order to evaluate the usefulness of a peripheral blood PCR assay
in the posttreatment follow-up of brucellosis, a cohort of 30 patients
was studied by means of blood cultures, rose Bengal, seroagglutination,
Coombs' antibrucella tests, and PCR assay at the time of diagnosis, at
the end of treatment, and 2, 4, and 6 months later. Of the 29 patients
whose PCR assays were initially positive, 28 (96.5%) were negative at
the conclusion of the treatment. PCR was positive for the two patients
who had relapses and negative for another four who had suspected but
unconfirmed relapses. PCR was negative for 98.3% of the follow-up
samples from those patients who had a favorable evolution. In
conclusion, PCR appears to be a very useful technique, not only for the
initial diagnosis of the disease, but also for posttreatment follow-up
and the early detection of relapses.
 |
TEXT |
Brucellosis is a world-wide zoonosis
transmittable to humans, in whom it has a high degree of morbidity
(14, 26). Brucella organisms are able to survive
and even multiply within cells of the mononuclear-phagocytic system,
thus explaining the tendency of the disease to have a prolonged
clinical course and relapses (9, 18, 20). Even with the
correct treatment, the incidence of relapses in brucellosis remains
high, ranging from 4 to 41% of patients in the largest series reported
to date (3, 7, 17).
The clinical picture of brucellosis is very heterogeneous and
nonspecific (8), and the clinical manifestations of relapsed brucellosis are milder, overlapping, and nonspecific, the hematological and biochemical changes being even more subtle than in the initial infection. Diagnosis of brucellosis relapses is therefore generally difficult, and microbiological techniques are often required for confirmation. However, the yield of blood cultures in relapses is no
higher than 60 to 70% (2, 23), and the value of serological diagnosis in this situation is limited (20).
PCR has been shown to be a more sensitive technique than blood cultures
and more specific than conventional serological tests for the diagnosis
of infection with Brucella melitensis (21). We
therefore evaluated the usefulness of a PCR-based assay in the
posttreatment follow-up and the early diagnosis of relapses in patients
with brucellosis.
Patient population.
From January 1997 to March 1998, we
studied a cohort of 30 patients with brucellosis. Twenty-eight were
diagnosed and treated in the Infectious Diseases Unit of "Carlos
Haya" Hospital in Malaga, Spain, and the other 2 were treated in the
Infectious Diseases Service of "Virgen del Rocío"
University Hospital in Seville, Spain. The diagnosis of brucellosis was
established according to one of the following criteria: (i) isolation
of Brucella spp. in blood or any other body fluid or tissue
sample or (ii) the presence of a compatible clinical picture together
with the demonstration of specific antibodies at significant titers or
seroconversion. Significant titers were considered to be a Wright's
seroagglutination titer of
1/160 or a Coombs' antibrucella test
titer of
1/320.
Of the 30 patients included, 16 (53.3%) were men and 14 (46.7%) were
women. The mean age of the group was 40.1 ± 14.5 years (range, 17 to 71 years). In 26 patients (86.6%), the brucellosis was the first
episode of infection, in 2 (6.6%) it was a reinfection, and in the
other 4 (13.3%) it was a relapse. The duration of the symptoms prior
to diagnosis was 11.7 ± 22.7 weeks (range, 1 to 102 weeks). In 9 patients (30%), the duration of the symptoms was less than 2 weeks; in
eight (26.6%), it was between 2 weeks and 1 month; in another 8 (26.6%), it was between 1 and 3 months; and in the other five
(16.6%), it was longer than 3 months. All of the patients had fever
during the evolutionary course of the disease. The clinical picture in
17 (56.6%) patients was a nonfocal febrile syndrome, and the other 13 (43.3%) had one or more focal forms (3 with spondylitis, 2 with liver
abscess, and 1 each with sacroiliitis, knee arthritis, wrist arthritis,
oligoarthritis, hepatitis, splenic abscess, pneumonia, infected ovarian
teratoma, or infected renal cyst).
All patients with suspected brucellosis had two or more blood cultures
and a serological battery of tests, including the rose Bengal plate
agglutination test, Wright's seroagglutination, and Coombs'
antibrucella test. A 3.5-ml peripheral blood sample was also taken for
PCR analysis.
The blood cultures were processed in a BACTEC 9240 (Becton Dickinson
Diagnostic Instrument Systems, Towson, Md.) according
to the usual
techniques. For those cases in which the system failed
to detect any
growth, the incubation was maintained for 30 days,
with blind
subcultures performed after 10, 20, and 30 days. Identification
of
Brucella spp. was made according to standard microbiological
techniques (
11). All of the strains isolated were sent to
the
National Brucellosis Reference Laboratory in Valladolid, Spain,
for
definitive identification and biotyping. The serological tests
were
performed according to previously described techniques (
1,
12,
16).
The diagnosis of brucellosis was established by isolation of
Brucella spp. in 22 patients (73.3%), for 21 of whom the
isolation
was made by blood culture (66.7%) and for 1 (6.7%) of whom
the
isolation was made with synovial fluid. Diagnosis in the remaining
eight (26.7%) patients was clinical and serological. All of the
strains isolated were identified as
B. melitensis: 18 were
biovar
1 (81.8%), 3 were biovar 2 (13.6%), and 1 was biovar 3 (4.5%).
After diagnosis of the brucellosis, 26 (86.7%) patients were treated
with doxycycline plus streptomycin sulfate, and 3 (10%)
were treated
with doxycycline plus rifampin according to internationally
accepted
treatment regimens (
3). The remaining patient was
a woman
who was 4 weeks pregnant and who was treated with rifampin
alone for 3 months. The patients were examined at the end of treatment
and after 2, 4, and 6 months, as well as at any intermediate time
if relapse was
suspected, and at each evaluation, the following
tests were performed:
blood cultures, rose Bengal, Wright's seroagglutination,
Coombs'
test, and the PCR
assay.
Therapeutic failure was considered to be the persistence or worsening
of the symptoms or signs of the disease after 15 days
of treatment in
those patients with nonfocal forms of the disease
and after 1 month of
treatment in patients with focal forms. The
criteria for the definition
of the different focal forms have
been published previously by our
group (
8). Relapse was considered
to be either (i) the
existence of a new positive blood culture,
(ii) the reappearance of a
compatible symptomatology not otherwise
explained together with a new
increase in the previous serological
titers, or (iii) the appearance of
a new focal form highly suggestive
of brucellosis (e.g., peripheral
arthritis, sacroiliitis, orchiepididymitis,
lymphocytic meningitis,
endocarditis, etc.) with persistently
high serological
titers.
PCR assay.
Peripheral blood for PCR was collected in sodium
citrate and stored at
20°C until processing. PCR was carried out by
our previously reported technique (15, 21). Briefly, this
consists of amplification of a 223-bp fragment from the gene coding for the synthesis of an immunogenic protein on the external membrane of
Brucella abortus (BCSP31). This protein, with a molecular
mass of 31 kDa, is specific to the genus Brucella and is
present in all of its biovars. The amplification was performed with the
primers B4 (5'-TGG CTC GGT TGC CAA TAT CAA-3') and B5 (5'-CGC GCT TGC CTT TCA GGT CTG-3') (5). All tests included positive
controls of B. melitensis Rev-1 DNA and negative controls
containing all of the reaction components except DNA. To detect any
possible contamination during the extraction stage of the DNA, all of
the PCR assays included control samples from a healthy person.
Moreover, to ensure the reliability of the results, all of the samples
were processed in duplicate. The test was considered positive if the signal from the amplified product was clearly visible in both samples.
Results.
A total of 137 PCR assays were done, with a mean of
4.5 ± 1.07 assays per patient. At the moment of diagnosis, the
PCR was positive for 29 of the 30 patients (96.6%). One patient with
pneumonia still had fever 15 days after starting treatment, at which
point an empyema developed. A new set of blood cultures were negative, whereas the PCR remained positive.
The PCR was negative on conclusion of the treatment for 28 of the 29 patients (96.5%) whose PCR was initially positive. The
only patient
for whom the PCR remained positive at the end of
treatment was
asymptomatic, and the blood cultures were negative.
The patient
received no additional treatment and remained asymptomatic,
the PCR
becoming negative in the following revision and remaining
so in all
subsequent controls during the follow-up
period.
Six patients (20%) had symptoms suggestive of relapse during the
follow-up period. Of these, two (6.6%) had a confirmed relapse
2 and 5 months after concluding treatment, and in the other four
(13.3%),
relapse was eventually ruled out: three because of an
alternative
diagnosis (one infection with
Rickettsia conorii,
one with
sinusitis, and one with a urinary tract infection with
hydrocele) and
the fourth due to self-limitation of all the symptoms
after 5 days with
no reappearance during the clinical, serological,
and bacteriological
12-month follow-up. Table
1 shows the
results
of the bacteriological, serological, and PCR tests for the
patients
with suspected relapse. Both patients with relapses had a
positive
PCR, but only one had positive blood cultures again, and
neither
had seroconversion of previous titers. Figure
1 shows the evolution
of the PCR in the
patient who relapsed and whose blood cultures
were negative. The PCR in
the two patients with relapses became
negative again after concluding
the treatment of the relapse and,
as with 27 of the remaining 28 patients (96.4%), remained persistently
negative during the whole
follow-up period.

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FIG. 1.
Agarose gel electrophoresis and ethidium bromide
staining. Lanes: MW, molecular size DNA ladder (223 bp); 1, positive
control (B. melitensis Rev-1); 2, no DNA added; 3 to 8, sequential samples from one of the patients with a relapse; 3, DNA from
the patient at the time of diagnosis when the blood cultures were
positive; 4, DNA at the conclusion of treatment; 5, DNA at the time of
relapse when the blood cultures were negative; 6 to 8, DNA from the
patient at the end of treatment of the relapse and 2 and 4 months
later; 9, DNA from a healthy control. The photocomposition of the
figure was obtained from the original Polaroid films with a ScanJed
IIcx scanner (Hewlett-Packard, Corvallis, Oreg.). After the initial
image was scanned and saved as a TIFF file, the file was opened in
Adobe Photoshop, version 3.0 (Adobe Systems, Inc., Seattle, Wash.).
|
|
Just one patient in the group with no relapses (3.6%) had a positive
PCR at the 6-month control test. He was a 60-year-old
farmer with
long-term insulin-dependent diabetes mellitus who
had had brucellosis
complicated by lumbar spondylitis 9 months
previously, requiring
surgery and treatment with streptomycin
sulfate (1 g intramuscularly
per day for 21 days and 100 mg of
doxycycline per os twice per day for
3 months). When the PCR became
positive again, the patient was
asymptomatic and had returned
to his usual activities with cattle. He
presented no biological
signs of active infection, the blood cultures
were negative, the
serological titers continued to fall compared to
those in the
prior study, and another examination of the lumbar spine
by magnetic
resonance imaging showed a favorable evolution of the
spondylitis.
Discussion.
One of the main characteristics of brucellosis is
its marked tendency to relapse after conclusion of the treatment
(2, 26). This problem is related to the ability of
Brucella spp. to elude some of the basic mechanisms of the
host's immune system, so that the hallmark of the efficacy of any
antibrucella treatment is its capacity to reduce the rate of relapse.
Since almost 90% of relapses occur during the 6 months following
conclusion of the treatment, strict follow-up is necessary during this
period in order to detect any relapse as soon as possible and to
provide adequate therapy (3, 7, 13, 22, 24). However, a high proportion of brucellosis patients report nonspecific symptoms after
the conclusion of their treatment, and because there are no
well-defined criteria for complete recovery from brucellosis, it is
often difficult to decide whether these patients are really cured.
In general clinical practice, the posttreatment follow-up of patients
with brucellosis includes the appropriate clinical examination
together
with blood cultures and serological tests. To date, however,
the very
few studies that have examined the clinical and microbiological
profiles of relapses in brucellosis have shown the most effective
test
for the diagnosis of relapses to be blood cultures, since
besides being
an irrefutable test of active infection, the blood
culture may also be
positive in asymptomatic patients. However,
the sensitivity of blood
cultures in the diagnosis of relapses
is not very high, ranging from 50 to 65% in the largest series
(
2,
13,
23).
Serological methods, although faster and easier to perform, lack
specificity, with many studies demonstrating that for a long
time after
conclusion of treatment, serological titers can remain
high or even
increase in patients with repeatedly negative blood
cultures and no
evidence of clinical relapse after a considerable
follow-up period
(
4,
10,
20). Some authors have reported
a high
seroconversion rate with different serological tests for
detecting
immunoglobulin G antibodies in relapsed patients (
4,
6,
25).
Nevertheless, at the time of symptom presentation,
only 40% of
patients show a significant increase in previous serological
titers. In
the remaining patients, seroconversion takes place
within 3 months
after onset of the symptoms of relapse, at which
time, these data lose
virtually all clinical interest (
4,
20).
In this study, 96.4% of the patients had a negative PCR on concluding
treatment, a fact which would seem very useful for later
control. The
PCR for the only patient who remained positive at
the end of treatment
became negative 1 month later, with no evidence
of relapse. This may
indicate that due to the extremely high detection
capacity of the
technique, the PCR might, in a very few cases,
amplify the DNA of
nonviable bacteria or the remains of DNA present
in the circulating
mononuclear cells of patients who have concluded
successful
treatment.
As happens with the first episode of infection, the usefulness of PCR
in the diagnosis of relapses appears greater than that
of blood
cultures. However, it must be taken into account that
the number of
patients included in a study of these characteristics
cannot be very
high, and since the therapeutic regimens employed
are highly effective,
the number of expected relapses was low,
necessitating caution when
evaluating the results. Nevertheless,
it is important to note that four
of the patients were included
in the study due to relapse of
brucellosis which had been treated
elsewhere, and all of them had a
positive PCR at the time of admission.
This agrees with previous
results reported by our group in another
study (
21). Thus,
if we include the two episodes of relapse
in this study, we have had
the opportunity to perform PCR analysis
for 14 episodes of relapse so
far. Of these, the blood cultures
were positive in 10 (71.4%) episodes
compared to the 13 (92.8%)
positive PCR results (
15,
21).
As well as correctly identifying the two relapsed patients, the PCR was
negative in all patients in whom a suspected relapse
was ruled out.
This seems to provide the test with a high negative
predictive value, a
very important fact if we consider that in
two of these four patients
with unconfirmed suspected relapse,
the titers of the Coombs' test had
increased significantly. Similar
serological findings have been
reported by others (
4,
13,
20). Finally, only 1 of the 77 PCRs performed between the second
and sixth months of follow-up in the
patients who had no relapse
was false positive (1.3%). In this case,
the patient had returned
to work with his cattle, suggesting that he
may have had a subclinical
reinfection not detected by the other
microbiological
techniques.
Finally, although a few patients may have a positive PCR at conclusion
of treatment, and it is necessary to be prudent in
interpreting the
results in patients who are permanently exposed,
PCR appears to be a
more sensitive technique than conventional
microbiological methods, not
just for the diagnosis of a first
episode of infection, but also for
posttherapy follow-up of the
disease and the early detection of
relapses.
 |
ACKNOWLEDGMENTS |
This work received financial support from the Inter-Ministerial
Commission for Science and Technology (CICYT) and the European Commission (grant IFD97-0539), F.I.S. (grant 97/0713), and P.A.I. (54/97) Consejería de Salud, Junta de Andalucía, Spain.
We thank Ian Johnstone for help with the English language version of
the manuscript.
 |
FOOTNOTES |
*
Corresponding author. Mailing address: Unidad de
Enfermedades Infecciosas, Dpto de Medicina Interna, Complejo
Hospitalario Carlos Haya, Camino de Antequera s/n, 29010 Malaga, Spain.
Phone: 34 5 2645809. Fax: 34 5 2645755. E-mail:
colmene{at}interbook.net.
 |
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Journal of Clinical Microbiology, December 1999, p. 4163-4166, Vol. 37, No. 12
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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