Xpert MTB/RIF Ultra CT value provides a rapid measure of sputum bacillary burden and predicts smear status in patients with pulmonary tuberculosis.

Traditionally, smear microscopy has been used to estimate bacillary burden in order to assess infectiousness in tuberculosis (TB) patients. Since Xpert MTB assays might replace smear microscopy as the first-line diagnostic test for pulmonary tuberculosis, an alternative measure of bacillary load that correlates with smear positivity is needed. This study assessed the correlation between CT (with and without normalization), smear status, culture time-to-positivity (TTP), and clinical factors in patients with Xpert ultra positive sputum during a four-year period. A cut-off CT value for smear positivity was also estimated. 204 samples were included. Strong correlation between both Xpert Ultra CT values (raw and normalized) and smear status was obtained (r = 0.78 and - 0.79, respectively). The association between Raw-CT and TTP was weaker than normalized-CT (N-CT) and TTP (r = 0.50 and r = - 0.70, respectively). A Raw-CT cut-off value of 21.4 was identified with 85.7% (95% CI 65.4-95) sensitivity and 92.9% (95% CI 84.3-96.9) specificity. A N-CT cut-off value of 5.2 yielded a sensitivity of 94.3% (95% CI 86.2-97.8) and specificity of 85.7% (95% CI 65.4-95). Our study demonstrates that Xpert Ultra CT value correlates well with other measures of bacillary load such as smear status or TTP. The correlation with TTP is stronger when the CT value is normalized using the internal control. The proposed N-CT cut-off value of 5.2 shows a better sensitivity than the Raw-CT when predicting smear positive status.

Role of molecular diagnostics in the clinical management of SARS-CoV-2 infection: advantages and drawbacks.

The diagnosis of SARS-CoV-2 is based on the use of nucleic acid amplification tests (NAAT), especially rRT-PCR. The latter also allows us to quickly identify variants of concern. However, its use in follow-up of patients and the correlation between Ct value and the viability of the virus is controversial.

Staphylococcus aureus native arthritis over 10 years.

OBJECTIVES: Septic arthritis is associated with significant case fatality and morbidity. Staphylococcus aureus is the most common cause of arthritis. We aimed to analyze the microbiological features of S. aureus causing native arthritis and to investigate their influence on the clinical outcome of the infection. PATIENTS AND METHODS: We conducted a retrospective study including all episodes of S. aureus native arthritis between 2005-2015. Phenotypic (antimicrobial susceptibility, ß-hemolysis, agr functionality, biofilm formation) and genotypic characteristics (pulsed-field gel electrophoresis, DNA microarrays) were investigated. The primary endpoint was microbiological failure of treatment, including infection relapse, persistence, or attributable death. RESULTS: Twenty-nine patients were included (65.5% of men, mean age: 59): seven (24.1%) patients presenting with methicillin-resistant S. aureus (MRSA) native arthritis and 19 with methicillin-susceptible S. aureus (MSSA) native arthritis. Treatment failure occurred in seven (26.9%) patients (4/7 patients [57.1%] among MRSA infections vs. 3/19 [15.8%] among MSSA infections). The persistence rate was similar in MRSA and MSSA infections (1/7 vs. 3/19). However, the case fatality was significantly higher in patients with MRSA infection (3/7 vs. 0/19). The most frequent clonal complex (CC) was CC5 (38.1%). MSSA showed higher genetic variability (nine CCs) versus MRSA (3 CCs). CONCLUSIONS: Beyond methicillin resistance, we did not find phenotypic or genotypic factors associated with the poor outcome of S. aureus native arthritis. CC5 was the major CC, showing the higher genetic variability of MSSA versus MRSA.