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Journal of Clinical Microbiology, December 1998, p. 3741-3742, Vol. 36, No. 12
0095-1137/98/$00.00+0
LETTERS TO THE EDITOR
Bartonella henselae-Based Indirect Fluorescence
Assays Are Useful for Diagnosis of Cat Scratch Disease
 |
LETTER |
In a recent article, Bergmans et al. evaluated a Bartonella
henselae-based indirect fluorescence assay (IFA) for the diagnosis of cat scratch disease (CSD). This IFA for immunoglobulin G (IgG), with
a cutoff of 1:512, revealed a very low sensitivity of only 31.8%
if B. henselae was cocultivated with Vero cells for a few hours and used as antigen (1). However, Regnery et al.
previously described an IFA based on cocultivation of B. henselae with Vero cells that detected IgG titers of 1:512 or
greater in 24 of 41 (58%) patients with clinically diagnosed CSD,
whereas the prevalence of such titers was low (3%) in healthy controls
(4). B. henselae cocultivated with Vero cells for
2 days locates intracellularly, as we have shown by transmission
electron microscopy; in that study, we used monolayers of Vero cells
with intracellular B. henselae for detection of specific IgG
by IFA (5). This in-house IFA revealed IgG titers of 1:256
or higher in 11 patients with B. henselae infections (proven
by PCR or characteristic histopathological findings) (2) and
IgG titers of 1:512 or higher in 17 of 20 patients with clinically
diagnosed CSD (3). These data sustain the speculation of
Bergmans et al. that the sensitivity of IFA based on B. henselae associated with Vero cells would be improved by
cocultivation for a few days instead of a few hours (1). In
the meantime, we have replaced our in-house test system with commercial
slides with Vero cell-associated B. henselae
(Bartonella IgG substrate slides; MRL Diagnostics, Cypress
Calif.) and using a cutoff of 1:256, have obtained a sensitivity of
84.6% and a specificity of 93.4% in our mixed urban-rural population
(6).
Since we recently showed that our in-house Vero cell-associated IFA was
not useful to detect IgM specific to B. henselae because of
false-positive results with blood donors and with patients with
lymphadenopathy not due to B. henselae, we now use
commercial slides with agar-derived B. henselae (MRL) that
yield a sensitivity of 70% for the detection of IgM in patients with
CSD (7). Furthermore, we could demonstrate by Western blot
that sera from patients with IgM to Epstein-Barr virus capsid antigen
showed strong reactions against B. henselae cocultivated
with Vero cells but weaker reactions against agar-derived B. henselae (7). Despite those pitfalls, detection of IgG
and IgM specific to B. henselae could replace traditional
diagnostic criteria for the diagnosis of CSD in patients with
lymphadenitis and prevent them from unnecessary surgery, but histology
and PCR may still be necessary in atypical clinical situations.
| |
REFERENCES |
| 1.
|
Bergmans, A. M. C.,
M. F. Peeters,
J. F. P. Schellekens,
M. C. Vos,
L. J. M. Saabe,
J. M. Ossewaarde,
H. Verbakel,
H. J. Hooft, and L. M. Schouls.
1997.
Pitfalls and fallacies of cat scratch disease serology: evaluation of Bartonella henselae-based indirect fluorescence assay and enzyme-linked immunoassay.
J. Clin. Microbiol.
35:1931-1937[Abstract].
|
| 2.
|
Goldenberger, D.,
R. Zbinden,
I. Perschil, and M. Altwegg.
1996.
Nachweis von Bartonella (Rochalimaea)/B. quintana mittels Polymerase-Kettenreaktion (PCR).
Schweiz. Med. Wochenschr.
126:207-213[Medline].
|
| 3.
|
Nadal, D., and R. Zbinden.
1995.
Serology to Bartonella (Rochalimaea) henselae may replace traditional diagnostic criteria for cat-scratch disease.
Eur. J. Pediatr.
154:906-908[Medline].
|
| 4.
|
Regnery, R. L.,
J. G. Olson,
B. A. Perkins, and W. Bibb.
1992.
Serological response to "Rochalimaea henselae" antigen in suspected cat-scratch disease.
Lancet
339:1443-1445[Medline].
|
| 5.
|
Zbinden, R.,
M. Höchli, and D. Nadal.
1995.
Intracellular location of Bartonella henselae cocultivated with Vero cells and used for an indirect fluorescent-antibody test.
Clin. Diagn. Lab. Immunol.
2:693-695[Abstract].
|
| 6.
|
Zbinden, R.,
N. Michael,
M. Sekulovski,
A. von Graevenitz, and D. Nadal.
1997.
Evaluation of commercial slides for detection of immunoglobulin G against Bartonella henselae by indirect immunofluorescence.
Eur. J. Clin. Microbiol. Infect. Dis.
16:648-652[Medline].
|
| 7.
|
Zbinden, R.,
A. Ströhle, and D. Nadal.
1998.
IgM to Bartonella henselae in cat-scratch disease and during acute Epstein-Barr virus infection.
Med. Microbiol. Immunol.
186:167-170[Medline].
|
| | | | |
Reinhard Zbinden
Department of Medical Microbiology
University of Zurich
Gloriastrasse 32
8028 Zurich, Switzerland
|
| |
AUTHOR'S REPLY |
In his letter, Dr. Zbinden presents some of his own data on
Bartonella serology but does not really criticize any major
points in our study. However, he does suggest that the low sensitivity of IgG serology found in our study may be incorrect. Therefore, we
would like to present some comments on some of Dr. Zbinden's statements.
In their own studies, Dr. Zbinden and colleagues found elevated IgG
titers in healthy cat owners and in healthy blood donors from a mixed
urban-rural area. They found that 9.2% of 120 donors were positive
when a cutoff titer of 1:256 was used, resulting in a 90.8%
specificity (2). We, however, used a different approach and
chose our cutoff value as the titer at which 95% of all healthy donors
were negative. As a result, the sensitivity of our assay dropped to
31.8% (with cocultivation) or 40.9% (without cocultivation). If this
approach were used in the study of Dr. Zbinden and colleagues, the
sensitivity of their serologic test would be 61.5%, with a cutoff of
1:512 and a specificity of 99.6%. This sensitivity is higher than the
sensitivities we found, but too low to be used as the only diagnostic
test for CSD.
Furthermore, their results were obtained by using one-point IgG
serology, and we have shown that one-point IgG serology is not highly
diagnostic for B. henselae infection. If only an IgG IFA is
performed, two-point serology is necessary to detect ongoing B. henselae infections.
From our study, we concluded that IgM serology was superior to IgG
serology, yielding a sensitivity of 71.4% in an IgM enzyme immunoassay. Zbinden et al. also found a sensitivity of 70% with the
MRL IgM IFA, which corroborates our finding (1). In
addition, IgM serology does not require two-point serology as IgG
serology does.
We agree with Dr. Zbinden that B. henselae serology is
better than the traditional diagnostic criteria for the diagnosis of CSD, such as the skin test and histology. However, in our opinion, PCR
is still necessary to diagnose patients suspected of having CSD.
Reliable Bartonella diagnosis is important because CSD has a
broad clinical spectrum and is often not recognized by clinical manifestations and serology alone. Furthermore, diagnosis of
Bartonella-induced disease is often very important in
differential diagnosis for patients with lymphadenitis. For
this reason, we would suggest using IgM serology as a screening test,
and if no IgM antibodies against Bartonella are found, PCR
should be performed.
| |
REFERENCES |
| 1.
|
Bergmans, A. M. C.,
M. F. Peeters,
J. F. P. Schellekens,
M. C. Vos,
L. J. M. Sabbe,
J. M. Ossewaarde,
H. Verbakel,
H. J. Hooft, and L. M. Schouls.
1997.
Pitfalls and fallacies of cat scratch disease serology: evaluation of Bartonella henselae-based indirect fluorescence assay and enzyme-linked immunoassay.
J. Clin. Microbiol.
35:1931-1937.
|
| 2.
|
Zbinden, R.,
N. Michael,
M. Sekulovki,
A. von Graevenitz, and D. Nadal.
1997.
Evaluation of commercial slides for detection of immunoglobulin G against Bartonella henselae by indirect immunofluorescence.
Eur. J. Clin. Microbiol. Infect. Dis.
16:648-652.
|
| | | | |
A. M. C. Bergmans
M. F. Peeters
Laboratory of Molecular Microbiology
St. Elisabeth Hospital Tilburg
5022 GC Tilburg, The Netherlands
|
| | | | |
L. M. Schouls
Research Laboratory for Infectious Diseases
National Institute of Public Health and the Environment
3720 BA Bilthoven, The Netherlands
|
Journal of Clinical Microbiology, December 1998, p. 3741-3742, Vol. 36, No. 12
0095-1137/98/$00.00+0
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