The diagnostic value of the detection of immunoglobulin G (IgG) and IgM by Bartonella henselae-based indirect fluorescence assay (IFA) and enzyme-linked immunoassay (EIA) for the diagnosis of cat scratch disease (CSD) was evaluated. The IFA was performed either with B. henselae that was cocultivated for a few hours with Vero cells or with noncocultivated B. henselae as the antigen. Additionally, the performance of a Bartonella PCR hybridization assay based on the 16S rRNA gene was determined and compared with those of the serologic assays. The study group consisted of 45 patients suspected of suffering from CSD by fulfilling one or more of the classical criteria. The specificities of the immunoassays were set at >95% by analysis of sera from 60 healthy blood donors. It is shown that the sensitivities of the IgG assays are very low (40.9% for the IFA with noncocultivated B. henselae as antigen) and that those of the IgM assays are higher (71.4% for the EIA) for patients who fulfilled two or more criteria for CSD. The IgM EIA showed the highest sensitivity: 71.4% in patients with two or more criteria for CSD and 80.6% for patients with a positive Bartonella PCR result. The results indicate that the specificities of both IFA and EIA IgG serologies and the sensitivity of the IFA IgM serology need to be improved. The PCR hybridization assay showed a sensitivity of 86.4% for patients who fulfilled two or more criteria for CSD and 100% for seven patients who fulfilled three or more criteria. The kinetics of IgG and IgM antibody production were studied in 18 patients with CSD on the basis of a positive B. henselae IFA IgM serology. The results indicate that there is no standard course of anti-B. henselae IgG and IgM production in patients with CSD, because some patients produced high levels of both IgG and IgM, others produced only high levels of IgM, and a few patients produced only low levels of antibodies.

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Cat-scratch disease (CSD), caused by Bartonella henselae infection, can mimic malignancy and can manifest atypically. Reliable serological testing is therefore of great clinical importance. The diagnostic performance of immunofluorescence assay (IFA) and ELISA was evaluated in a group of Dutch patients with proven CSD (clinical diagnosis confirmed by PCR). Sera of 51 CSD patients and 56 controls (patients with similar symptoms, but who were B. henselae PCR-negative and had an alternative confirmed diagnosis) were tested for anti-B. henselae IgM and IgG by IFA and ELISA. A commercially available IFA test for IgM had a sensitivity of 6%. In-house assays for IgM showed specificities of 93% (IFA) and 91% (ELISA), but with low sensitivities (53% and 65%, respectively). With a specificity of 82% (IFA) and 91% (ELISA), in-house IgG testing showed a significantly higher sensitivity in IFA (67%) than in ELISA (28%, p <0.01). Sensitivity was higher for genotype I (38-75%) than for genotype II (7-67%) infections, but this was only statistically significant for IgG ELISA (p <0.05). In conclusion, detection of IgM against B. henselae by in-house ELISA and IFA was highly specific for the diagnosis of CSD. The high seroprevalence in healthy individuals limits the clinical value of IgG detection for diagnosing CSD. Given the low sensitivity of the serological assays, negative serology does not rule out CSD and warrants further investigation, including PCR. Adding locally isolated (e.g., genotype II) B. henselae strains to future tests might improve the sensitivity.

Bordetella holmesii is a Gram-negative bacterium first identified in 1995. It can cause pertussis-like symptoms in humans. B. holmesii contains insertion sequences IS481 and IS1001, two frequently used targets in the PCR diagnosis of Bordetella pertussis and Bordetella parapertussis infections.

Repetitive sequence-based (Rep)-PCR genotyping as described here is based on the presence of homologues of Mycoplasma pneumoniae repeat-like elements in Staphylococcus. In this study we comparatively evaluated the usefulness of rep-PCR typing with two sets of well-defined collections of Staphylococcus aureus strains. Rep-PCR analysis of the first collection ofS. aureus strains (n = 59) and oneStaphylococcus intermedius strain showed 14 different rep-PCR patterns, with each pattern harboring 6 to 15 DNA fragments. The discriminatory power of rep-PCR typing compared well to those of arbitrarily primed PCR (average of 20 types) and pulsed-field gel electrophoresis (11 types). S. aureus strain collection I comprised four outbreak-related groups of isolates. The isolates in only one group were found to have identical rep-PCR profiles. However, in an analysis of isolates from three additional independent local outbreaks (n for outbreaks 1 and 2 = 5, nfor outbreak 3 = 12), identical rep-PCR types were found among strains isolated during each outbreak. Therefore, we conclude that rep-PCR genotyping may be an easy and fast method for monitoring of the epidemiology of nosocomial Staphylococcus infections. Rep-PCR analysis of strain collection II, which consisted of epidemic and nonepidemic methicillin-resistant S. aureus (MRSA) strains, revealed that a cluster of similar rep-PCR profiles was found among MRSA isolates which were more frequently isolated and which were most often associated with outbreaks.