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editorial
. 1998 Dec;36(12):3741–3742. doi: 10.1128/jcm.36.12.3741-3742.1998

Bartonella henselae-Based Indirect Fluorescence Assays Are Useful for Diagnosis of Cat Scratch Disease

Reinhard Zbinden 1
PMCID: PMC105282  PMID: 9867494

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, Peeters M F, Schellekens J F P, Vos M C, Saabe L J M, Ossewaarde J M, Verbakel H, Hooft H J, Schouls L M. Pitfalls and fallacies of cat scratch disease serology: evaluation of Bartonella henselae-based indirect fluorescence assay and enzyme-linked immunoassay. J Clin Microbiol. 1997;35:1931–1937. doi: 10.1128/jcm.35.8.1931-1937.1997. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Goldenberger D, Zbinden R, Perschil I, Altwegg M. Nachweis von Bartonella (Rochalimaea)/B. quintanamittels Polymerase-Kettenreaktion (PCR) Schweiz Med Wochenschr. 1996;126:207–213. [PubMed] [Google Scholar]
  • 3.Nadal D, Zbinden R. Serology to Bartonella (Rochalimaea) henselaemay replace traditional diagnostic criteria for cat-scratch disease. Eur J Pediatr. 1995;154:906–908. doi: 10.1007/BF01957503. [DOI] [PubMed] [Google Scholar]
  • 4.Regnery R L, Olson J G, Perkins B A, Bibb W. Serological response to “Rochalimaea henselae” antigen in suspected cat-scratch disease. Lancet. 1992;339:1443–1445. doi: 10.1016/0140-6736(92)92032-b. [DOI] [PubMed] [Google Scholar]
  • 5.Zbinden R, Höchli M, Nadal D. Intracellular location of Bartonella henselaecocultivated with Vero cells and used for an indirect fluorescent-antibody test. Clin Diagn Lab Immunol. 1995;2:693–695. doi: 10.1128/cdli.2.6.693-695.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6.Zbinden R, Michael N, Sekulovski M, von Graevenitz A, Nadal D. Evaluation of commercial slides for detection of immunoglobulin G against Bartonella henselaeby indirect immunofluorescence. Eur J Clin Microbiol Infect Dis. 1997;16:648–652. doi: 10.1007/BF01708554. [DOI] [PubMed] [Google Scholar]
  • 7.Zbinden R, Ströhle A, Nadal D. IgM to Bartonella henselaein cat-scratch disease and during acute Epstein-Barr virus infection. Med Microbiol Immunol. 1998;186:167–170. doi: 10.1007/s004300050060. [DOI] [PubMed] [Google Scholar]
J Clin Microbiol. 1998 Dec;36(12):3741–3742.

AUTHOR’S REPLY

A M C Bergmans 1,2, M F Peeters 1,2, L M Schouls 1,2

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 (1-2). 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 (1-1). 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

  • 1-1.Bergmans A M C, Peeters M F, Schellekens J F P, Vos M C, Sabbe L J M, Ossewaarde J M, Verbakel H, Hooft H J, Schouls L M. Pitfalls and fallacies of cat scratch disease serology: evaluation of Bartonella henselae-based indirect fluorescence assay and enzyme-linked immunoassay. J Clin Microbiol. 1997;35:1931–1937. doi: 10.1128/jcm.35.8.1931-1937.1997. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 1-2.Zbinden R, Michael N, Sekulovki M, von Graevenitz A, Nadal D. Evaluation of commercial slides for detection of immunoglobulin G against Bartonella henselaeby indirect immunofluorescence. Eur J Clin Microbiol Infect Dis. 1997;16:648–652. doi: 10.1007/BF01708554. [DOI] [PubMed] [Google Scholar]

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