Potential impact of a microarray-based nucleic acid assay for rapid detection of gram-negative bacteria and resistance markers in positive blood cultures

We evaluated the Verigene Gram-negative blood culture (BC-GN) test, a microarray that detects Gram-negative bacteria and several resistance genes. A total of 102 positive blood cultures were tested, and the BC-GN test correctly identified 97.9% of the isolates within its panel. Resistance genes (CTX-M, KPC, VIM, and OXA genes) were detected in 29.8% of the isolates, with positive predictive values of 95.8% (95% confidence interval [CI], 87.7% to 98.9%) in Enterobacteriaceae and 100% (95% CI, 75.9% to 100%) in Pseudomonas aeruginosa and negative predictive values of 100% (95% CI, 93.9% to 100%) and 78.6% (95% CI, 51.0% to 93.6%), respectively

Early molecular diagnosis of aspergillosis in a patient with acute myeloid leukaemia

Diagnosis of invasive fungal infection remains challenging. Here we report a case of early diagnosis of invasive aspergillosis in a neutropenic patient affected by acute myeloid leukaemia, achieved through the detection of Aspergillus fumigatus species-specific ribonucleic acid sequences by a sensitive multiplex real-time polymerase chain reaction-based molecular assay. Thanks to the early diagnosis, targeted therapy was promptly established and the severe fungal infection controlled, allowing the patient to subsequently receive allogeneic hematopoietic stem cell transplantation from a haploidentical donor, her only curative option. Also in this instance, targeted secondary antifungal prophylaxis with voriconazole avoided any other fungal infection afterwards. This report suggests how the implementation of molecular assays in combination with routine diagnostic procedures, can improve microbiological diagnosis in sepsis, particularly in case of fungal infection, difficult to detect with standard microbiological culture methods

The era of molecular and other non-culture based methods in the diagnosis of sepsis

Sepsis, a leading cause of morbidity and mortality throughout the world, is a clinical syndrome with signs and symptoms relating to an infectious event and the consequent important inflammatory response. From a clinical point of view, sepsis is a continuous process ranging from systemic inflammatory response syndrome (SIRS) to multiple-organ-dysfunction syndrome (MODS). Blood cultures are the current “gold standard” for diagnosis, and they are based on the detection of viable microorganisms present in blood. However, on some occasions, blood cultures have intrinsic limitations in terms of sensitivity and rapidity, and it is not expected that these drawbacks will be overcome by significant improvements in the near future. For these principal reasons, other approaches are therefore needed in association with blood culture to improve the overall diagnostic yield for septic patients. These considerations have represented the rationale for the development of highly sensitive and fast laboratory methods. This review addresses non-culture-based techniques for the diagnosis of sepsis, including molecular and other non-culture-based methods. In particular, the potential clinical role for the sensitive and rapid detection of bacterial and fungal DNA in the development of new diagnostic algorithms is discussed

Potential role of the detection of enterobacterial DNA in blood for the management of neonatal necrotizing enterocolitis

We present three cases of pre-term low-weight infants with suspected necrotizing enterocolitis (NEC) [one eventually recognized as a connatal cytomegalovirus (CMV) infection], microbiologically monitored using a molecular assay detecting bacterial and fungal DNA in blood. The detection of DNA from enteric pathogens in blood was interpreted as a sign of ongoing perforation, and represented a useful complement in the management of the presented cases. Moreover, these cases suggest the opportunity for larger future studies to assess the possible role of a molecular approach in the close monitoring of infants with suspected NEC or with other conditions at-risk for intestinal perforation

Hepatitis C virus (HCV)-driven stimulation of subfamily-restricted natural IgM antibodies in mixed cryoglobulinemia

Hepatitis C virus (HCV) infection has been closely related to mixed cryoglobulinemia (MC). During HCV infection, cryoglobulins derive from the restricted expression of few germline genes as VH1-69, a subfamily highly represented in anti-HCV humoral response. Little is known about the self-reacting IgM component of the cryoprecipitate. In the present study, the IgM/K repertoire of an HCV-infected cryoglobulinemic patient was dissected by phage-display on well-characterized anti-HCV/E2 VH1-69-derived monoclonal IgG1/Κ Fab fragments cloned from the same patient. All selected IgM clones were shown to react with the anti-HCV/E2 antibodies belonging to VH1-69 subfamily. More than 60% of selected clones showed a bias in VH gene usage, restricted to two VH subfamilies frequently described in autoimmune manifestations (VH3-23; VH3-21). Moreover, all selected clones showed an high similarity (> 98.5%) to germline genes evidencing their natural origin. A possible hypothesis is that clones belonging to some subfamilies are naturally prone to react against other VH gene subfamilies, as VH 1-69. An antigen-driven stimulation of these subfamilies, and their overexpression as in HCV infection, could lead to a breaking of humoral homeostatic balance exposing the patients to the risk of developing autoimmune disorders

Molecular diagnosis of sepsis in neutropenic patients with haematological malignancies

The rapid diagnosis of an infectious cause in the course of fever of unknown origin plays a pivotal role in the correct management of neutropenic patients. In this study, blood samples from febrile oncolhaematological patients were tested using a novel commercial real-time PCR assay (LightCycler SeptiFast; Roche Molecular Systems) and blood culture (BacT/Alert 3D; bioMerieux). Twenty-one (20.4%) and 34 (33%) of the 103 samples under study tested positive by blood culture and PCR, respectively. The analysis of concordance evidenced a low correlation between the two approaches (83%), mainly due to samples that tested negative by culture but positive using the molecular approach. Among 14 discordant cases negative by culture but positive by PCR, 12 were observed in sequential samples of patients with initial concordant results on samples drawn before the administration of a specific antimicrobial therapy. Moreover, DNA of a fastidious organism, Aspergillus fumigatus, not easily detectable by the cultural approach was rapidly detected in the two remaining discordant cases. Overall, the characteristics featured by the molecular method could be of interest in the development of new algorithms for the diagnosis of sepsis in critical patients. RI Burioni, Roberto /F-2396-201

Cost-effectiveness of blood culture and a multiplex real-time PCR in hematological patients with suspected sepsis: an observational propensity score-matched study.

We evaluated the costs and clinical outcomes of episodes of suspected sepsis in hematological patients. A propensity score-matched study was planned, comparing a retrospective cohort managed with standard assays and a prospective cohort managed with the addition of a molecular assay. Diagnostic procedures and therapy were considered as costs variables. The primary clinical endpoint was sepsis-related mortality, whereas the length of each suspected sepsis episode was investigated as a secondary endpoint. A total of 137 and 138 episodes in the prospective and the retrospective cohorts were studied, respectively; 101 pairs of highly matched episodes were analyzed, evidencing a trend of higher mortality in the retrospective cohort. No difference in length of suspected sepsis episode was observed. Significant savings were observed in the prospective cohort, especially due to reduced costs in antifungal therapy. The apparently more expensive molecular assay favored a more rational use of economic resources without influencing, and probably improving, the clinical outcome

Cost-effectiveness of blood culture and a multiplex real-time PCR in hematological patients with suspected sepsis: an observational propensity score-matched study

We evaluated the costs and clinical outcomes of episodes of suspected sepsis in hematological patients. A propensity score-matched study was planned, comparing a retrospective cohort managed with standard assays and a prospective cohort managed with the addition of a molecular assay. Diagnostic procedures and therapy were considered as costs variables. The primary clinical endpoint was sepsis-related mortality, whereas the length of each suspected sepsis episode was investigated as a secondary endpoint. A total of 137 and 138 episodes in the prospective and the retrospective cohorts were studied, respectively; 101 pairs of highly matched episodes were analyzed, evidencing a trend of higher mortality in the retrospective cohort. No difference in length of suspected sepsis episode was observed. Significant savings were observed in the prospective cohort, especially due to reduced costs in antifungal therapy. The apparently more expensive molecular assay favored a more rational use of economic resources without influencing, and probably improving, the clinical outcome