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Background The rabbit infectivity test (RIT) was previously described as a highly-sensitive method for clinically detecting Treponema pallidum . But our primary study indicated this result may have changed in current antibiotics era. Methods By inoculating rabbits testis with cerebrospinal fluid (CSF) (n = 63) and exudate from hard chancre lesions (n = 13), we re-evaluated the sensitivity of RIT in modern era. All isolated T. pallidum strains from the RIT were performed for the strain type based on “CDC subtype/ tp0548 ” method. Chi-square and Fisher's exact tests were used to determine the statistical significance of differences across data sets. Results Result indicated that 2 of 63 CSF (2/63, 3.17%) and 5 of 13 lesion exudate samples (5/13, 38.47%) were positive in the RIT, with a much longer time to detection for CSF samples. Only 1 of 28 samples from patients who admitted treatment with antibiotics prior to clinical exam was positive in the RIT; while 6 of 48 patients, who admitted no recent exposure to antibiotics or was unclear about the medical history, were positive in RIT. DNA sequence analysis revealed 6 strains of 14d/f subtype and one strain of 14a/f subtype. Conclusions In conclusions, RIT is no longer a highly sensitive method for detecting T. pallidum in clinical samples as before, and is not inadequately considered to be a reference method for measuring the sensitivity of other new methods, such as the PCR. These data represent the first reexamination of the sensitivity of RIT in the post-antibiotic era with a large clinical sample. [ABSTRACT FROM AUTHOR]

Background Neurosyphilis (NS) is difficult to diagnose, especially in syphilis patients with negative cerebrospinal fluid (CSF) rapid plasma reagin (RPR) or Venereal Disease Research Laboratory (VDRL) tests. Methods We conducted a cross-sectional study and an analysis of macrophage migration inhibitory factor (MIF) in syphilitic patients to identify a novel marker for the diagnosis of NS, with a focus on probable NS (NS with negative VDRL/RPR tests). For this purpose, CSF and serum MIF concentrations were determined in 43 NS and 43 syphilis/non-NS (N-NS) patients at the Zhongshan Hospital of the Medical College of Xiamen University from July 2014 to June 2015. Sixty-three blood donors were used as healthy controls. Results NS patients had higher CSF (median [IQR]: 8.77 ng/ml [4.76–19.13]) and serum (52.58 ng/ml [28.31–95.94]) MIF concentrations than N-NS patients did (4.08 [2.21–9.68] and 34.30 [19.77–59.75], respectively). Using a cut-off point of 6.63 ng/ml, CSF MIF had a sensitivity of 74.42% and a specificity of 67.74% for the diagnosis of NS. The sensitivity was higher than that of CSF RPR (39.53%) and increased protein (48.84%) tests and similar to that of CSF pleocytosis (67.44%). Additionally, the sensitivity of CSF MIF, which was 92.31% for the diagnosis of probable NS, was higher than that of CSF pleocytosis (65.38%) and increased protein (53.85%) tests. By integrating all CSF parameters (pleocytosis, increased protein and MIF), the sensitivity would be improved to 100% by parallel testing, which would avoid missed diagnoses. Moreover, the specificity would be improved to 100% by the serial testing algorithm, which would again avoid misdiagnosis. Conclusions CSF MIF concentrations can be used as a novel CSF marker to establish or exclude a diagnosis of NS. [ABSTRACT FROM AUTHOR]