Colonization by multidrug-resistant bacteria in hematological patients undergoing hematopoietic stem cell transplantation and clinical outcomes: A single-center retrospective cohort study.

BACKGROUND: Bloodstream infections are a leading cause of death in patients who undergo hematopoietic stem cell transplantation (HSCT) and are more severe when caused by multidrug-resistant (MDR) bacteria. This study proposed to investigate if colonization by MDR bacteria negatively affects the clinical outcomes in hematological patients after HSCT, as well as to evaluate possible risk factors for death due to bacteremia by the same colonizing agent. METHODS: A single-center retrospective cohort study was conducted with 405 hematological patients submitted to a single HSCT procedure between 2015 and 2021. Patients were classified as colonized (n = 132) or noncolonized (n = 273) based on the surveillance cultures from D-30 to D+30 of transplantation, and their relevant clinical and laboratory data were collected until D+100. RESULTS: Colonization by MDR bacteria increased blood culture positivity by all micro-organisms and also specifically by MDR bacteria, with a more pronounced effect when caused by carbapenemase-producing Klebsiella pneumoniae. Patients colonized with carbapenem-resistant K. pneumoniae had increased overall mortality (HR = 4.07, 95% CI 1.85-8.91, P = .0005) and had prolonged hospital length of stay in the context of autologous transplantation. Risk factors for death due to bacteremia by the same colonizing agent were neutropenia, colonization by carbapenem-resistant K. pneumoniae and use of high-dose total body irradiation in conditioning. CONCLUSION: Hematological patients colonized by MDR bacteria presented a higher incidence of bloodstream infections, and colonization by carbapenemase-producing K. pneumoniae was associated with reduced overall survival.

Emergence of Thymidine-Dependent Staphylococcus aureus Small-Colony Variants in Cystic Fibrosis Patients in Southern Brazil.

We characterized Staphylococcus aureus small-colony variant (SCV) strains isolated from cystic fibrosis (CF) patients in southern Brazil. Smaller colonies of S. aureus were isolated from respiratory samples collected consecutively from 225 CF patients from July 2013 to November 2016. Two phenotypic methods-the auxotrophic classification and a modified method of antimicrobial susceptibility testing-were employed. PCR was conducted to detect the mecA, ermA, ermB, ermC, msrA, and msrB resistance genes. Furthermore, DNA sequencing was performed to determine the mutations in the thyA gene, and multilocus sequence typing was used to identify the genetic relatedness. S. aureus strains were isolated from 186 patients (82%); suggestive colonies of SCVs were obtained in 16 patients (8.6%). The clones CC1 (ST1, ST188, and ST2383), CC5 (ST5 and ST221), and ST398 were identified. Among SCVs, antimicrobial susceptibility testing showed that 77.7% of the isolates were resistant to multiple drugs, and all of them were susceptible to vancomycin. mecA (2), ermA (1), ermB (1), ermC (3), and msrB (18) were distributed among the isolates. Phenotypically thymidine-dependent isolates had different mutations in the thyA gene, and frameshift mutations were frequently observed. Of note, revertants showed nonconservative or conservative missense mutations. SCVs are rarely identified in routine laboratory tests. IMPORTANCE Similar findings have not yet been reported in Brazil, emphasizing the importance of monitoring small-colony variants (SCVs). Altogether, our results highlight the need to improve detection methods and review antimicrobial therapy protocols in cystic fibrosis (CF) patients.

The Xpert® MTB/RIF diagnostic test for pulmonary and extrapulmonary tuberculosis in immunocompetent and immunocompromised patients: Benefits and experiences over 2 years in different clinical contexts.

Xpert® MTB/RIF has been widely used for tuberculosis (TB) diagnosis in Brazil, since 2014. This prospective observational study aimed to evaluate the performance of Xpert in different contexts during a two-year period: (i) laboratory and clinical/epidemiological diagnosis; (ii) HIV-positive and -negative populations; (iii) type of specimens: pulmonary and extrapulmonary. Overall, 924 specimens from 743 patients were evaluated. The performance of the assays was evaluated considering culture (Lowenstein Jensen or LJ medium) results and composite reference standard (CRS) classification as gold standard. According to CRS evaluation, 219 cases (29.5%) were classified as positive cases, 157 (21.1%) as 'possible TB', and 367 (49.3%) as 'not TB'. Based on culture, Xpert and AFB smear achieved a sensitivity of 96% and 62%, respectively, while based on CRS, the sensitivities of Xpert, AFB smear, and culture were 40.7%, 20%, and 25%, respectively. The pooled sensitivity and specificity of Xpert were 96% and 94%, respectively. Metric evaluations were similar between pulmonary and extrapulmonary samples against culture, whereas compared to CRS, the sensitivities were 44.6% and 29.3% for the pulmonary and extrapulmonary cases, respectively. The Xpert detected 42/69 (60.9%) patients with confirmed TB and negative culture on LJ medium, and 52/69 (75.4%) patients with negative AFB smear results. There was no significant difference in the diagnostic accuracy based on the types of specimens and population (positive- and negative-HIV). Molecular testing detected 13 cases of TB in culture-negative patients with severe immunosuppression. Resistance to rifampicin was detected in seven samples. Herein, Xpert showed improved detection of pulmonary and extrapulmonary TB cases, both among HIV-positive and -negative patients, even in cases with advanced immunosuppression, thereby performing better than multiple other diagnostic parameters.