Comparative evaluation of Xpert MTB/RIF and the new Xpert MTB/RIF ultra with respiratory and extra-pulmonary specimens for tuberculosis case detection in a low incidence setting

Background: The Xpert MTB/RIF assay (Xpert) is an automated molecular test for the detection of tuberculosis and rifampin resistance (RIF-R), but it lacks sensitivity in smear-negative samples and some limitations in determination of RIF-R have also been reported. The new Xpert MTB/RIF Ultra (Ultra) was developed to overcome these limitations. We aimed to compare Ultra and Xpert diagnostic accuracy setting culture and drug susceptibility testing as reference standards. Methods: A retrospective analysis was performed on 359 consecutive, respiratory (269) and extrapulmonary (90) specimens collected from 340 patients investigated for TB along a two-year period. Patients presenting at primary health-care centres and hospitals were recruited on the basis of symptoms and abnormal X-ray imaging. One-hundred seventy-four subjects were identified to have active tuberculosis by culture and 2 were MDR. Findings: Sensitivities of Ultra and Xpert were 87% and 75% for the 48 individuals with smear-negative and culture-positive respiratory TB (difference of 12%, 95% CI 3 to 21); 95% and 72% for the 40 individuals with smear-negative and culture-positive extrapulmonary disease (22%, 95% CI 10 to 34); and 95% and 86%, respectively, across all 174 individuals with culture-positive samples (8.5%, 95% CI 4.5 to 12.5). Specificities of Ultra and Xpert for tuberculosis case detection were 98% and 100% (–2.0%, 95% CI –4.3 to +0.3). Ultra and Xpert performed equal in detecting RIF-R. Interpretation: Sensitivity of Ultra was superior to that of Xpert in all categories of clinical samples. However, improved sensitivity was associated with a modest reduction in specificity. Keywords: Tuberculosis, Case detection, Nucleic acid amplification, Xpert MTB/RIF Ultra, Sensitivity, Specificit

Unreliable Detection of Mycobacterium xenopi by the Nonradiometric Bactec MGIT 960 Culture System▿

From June 2006 to December 2007, 3,648 clinical specimens consecutively received for mycobacterial culture were investigated. Each processed sample was inoculated into Bactec MGIT 960 liquid medium and a Löwenstein-Jensen slant. Tubes that were flagged as positive by the instrument as well as those determined to be negative after 42 days of incubation were removed, visually inspected for growth, and checked for the presence of acid-fast bacilli. Three hundred sixty-nine mycobacterial strains were recovered; of the 44 Mycobacterium xenopi isolates recovered by MGIT medium, only 13 were detected by the instrument (P < 0.0001). Most tubes yielding M. xenopi exhibited a peculiar pattern of growth characterized by a scant number of round, yellow-pigmented granules instead of the fine, evenly dispersed clumps usually observed for mycobacteria. It is suggested to check all individual tubes discarded by the MGIT 960 system at the end of the incubation period to prevent a significant amount of previously undetected growth from being missed

Ricerca di anticorpi IgA anti-Chlamydia trachomatis nel liquido seminale mediante un test ELISA sperimentalmente modificato

Chlamydia trachomatis (Ct) is a relevant agent of male genital tract infections and some correlated complications, such as epididymitis. The diagnosis of infection by the highly sensitive nucleic amplification test is hampered on semen specimen because of many inhibitory factors. Instead, a reliable serologic test able to demontrate the involvement of the upper genital tract should be of clinical utility. Two group of a total of 505 male patients, suspected for infertility and/or genital infections were examined for detecting direct and serologic markers of chlamydia on urethral swabs, semen and serum specimen, respectively. By the amplified nucleic DNA-Chlamydia trachomatis LCR test (“gold standard”), a total of 16 patients resulted as positives. On the semen specimen a positive detection of specific Ct-IgA antibodies was obtained by the ELISA and the referenced MIF test in 15 patients, thus demonstrating a local immune response to Chlamydia infection.Neverthless, a few of these Ct-IgA positive patients resulted with negative DNA-Ct detection and with Ct-IgA negative results in serum. The significance of the study point out on the previous demonstrated local immune response, often without detection of circulating specific IgG and/or IgA anti-Ct antibodies. Furthermore, is emphasized that the presence of Ct-IgA on semen may not correlate with the amplified direct test results, due to the fact that the infection can already has ascended to the epididymis, and thus escapes from peripheric direct detection. On the basis of the above experienced results, the local specific Ct-IgA antibodies detection seems to be a precious marker of a especially silent ongoing Chlamydia infection

CYBERKNIFE ROBOTIC IMAGE-GUIDED STEREOTACTIC RADIOTHERAPY FOR ISOLATED RECURRENT PRIMARY, LYMPH NODE OR METASTATIC PROSTATE CANCER

N/