Host response signature trends in persistent bacteraemia and metastatic infection due to Staphylococcus aureus and Gram-negative bacilli: a prospective multicentre observational study.

BACKGROUND: A prompt diagnosis of bacteraemia and sepsis is essential. Markers to predict the risk of persistent bacteraemia and metastatic infection are lacking. SeptiCyte RAPID is a host response assay stratifying patients according to the risk of infectious vs sterile inflammation through a scoring system (SeptiScore). In this study we explore the association between SeptiScore and persistent bacteraemia as well as metastatic and persistent infection in the context of a proven bacteraemia episode. METHODS: This is a prospective multicentre observational 14-month study on patients with proven bacteraemia caused by Staphylococcus aureus or Gram-negative bacilli. Samples for assessment by SeptiCyte were collected with paired blood cultures for 4 consecutive days after the index blood culture. RESULTS: We included 86 patients in the study, 40 with S. aureus and 46 with Gram-negative bacilli bacteraemia. SeptiScores over the follow-up were higher in patients with Gram-negative compared to S. aureus bacteraemia (median 6.4, IQR 5.5-7.4 vs 5.6 IQR 5.1-6.2, p = 0.002). Higher SeptiScores were found to be associated with positive blood cultures at follow-up (AUC = 0.86, 95%CI 0.68-1.00) and with a diagnosis of metastatic infection at day 1 and 2 of follow-up (AUC = 0.79, 95%CI 0.57-1.00 and AUC = 0.82, 95%CI 0.63-1.00 respectively) in the context of Gram-negative bacteraemia while no association between SeptiScore and the outcomes of interest was observed in S. aureus bacteraemia. Mixed models confirmed the association of SeptiScore with positive blood cultures at follow-up (p = 0.04) and metastatic infection (p = 0.03) in the context of Gram-negative bacteraemia but not S. aureus bacteraemia after adjusting for confounders. CONCLUSIONS: SeptiScores differ in the follow-up of S. aureus and Gram-negative bacteraemia. In the setting of Gram-negative bacteraemia SeptiScore demonstrated a good negative predictive value for the outcomes of interest and might help rule out the persistence of infection defined as metastatic spread, lack of source control or persistent bacteraemia.

Persistence of Detectable Pathogens by Culture-Independent Systems (T2 Magnetic Resonance) in Patients With Bloodstream Infection: Prognostic Role and Possible Clinical Implications.

BACKGROUND: Persistent Staphylococcus aureus bacteremia is associated with metastatic infection and adverse outcomes, whereas gram-negative bacteremia is normally transient and shorter course therapy is increasingly advocated for affected patients. Whether the prolonged detection of pathogen DNA in blood by culture-independent systems could have prognostic value and guide management decisions is unknown. METHODS: We performed a multicenter, prospective, observational study on 102 patients with bloodstream infection (BSI) to compare time to bloodstream clearance according to T2 magnetic resonance and blood cultures over a 4-day follow-up. We also explored the association between duration of detectable pathogens according to T2 magnetic resonance (magnetic resonance-DNAemia [MR-DNAemia]) and clinical outcomes. RESULTS: Time to bloodstream clearance according to T2 magnetic resonance was significantly longer than blood culture clearance (HR, .54; 95% CI, .39-.75) and did not differ according to the causative pathogen (P = .5). Each additional day of MR-DNAemia increased the odds of persistent infection (defined as metastatic infection or delayed source control) both in the overall population (OR, 1.98; 95% CI, 1.45-2.70) and in S. aureus (OR, 1.92; 95% CI, 1.12-3.29) and gram-negative bacteremia (OR, 2.21; 95% CI, 1.35-3.60). MR-DNAemia duration was also associated with no improvement in Sequential Organ Failure Assessment score at day 7 from infection onset (OR, 1.76; 95% CI, 1.21-2.56). CONCLUSIONS: T2 magnetic resonance may help diagnose BSI in patients on antimicrobials with negative blood cultures as well as to identify patients with metastatic infection, source control failure, or adverse short-term outcome. Future studies may inform its usefulness within the setting of antimicrobial stewardship programs.

Assessing the performance of the Cepheid Xpert in identifying and differentiating methicillin-susceptible Staphylococcus aureus and methicillin-resistant Staphylococcus aureus from blood culture bottles.

Staphylococcus aureus bacteraemia is associated with a high morbidity and mortality. Time to effective antibiotics is key to reducing mortality. Current practices yield preliminary susceptibilities approximately 16-18 h after blood culture positivity. Molecular diagnostics could reduce the time from blood culture positivity to organism identification as MRSA or MSSA. The objective was to assess the performance of the GeneXpert in identifying MRSA/MSSA from blood culture bottles in the BACT/ALERT VIRTUO system. Eighty-eight blood culture bottles with Gram-positive cocci resembling staphylococci were analysed at Pathology Queensland using the Cepheid Xpert MRSA/SA BC system. The identification and susceptibilities from standard operating procedures were compared with the results from the Xpert MRSA/SA Blood Culture assay and routine laboratory practice. The overall positive percent agreement between the GeneXpert and standard laboratory practice was 94.1% (95% CI 85.6-98.37%) and the negative percent agreement was 100% (95% CI 83.16-100%). The Cepheid Xpert accurately identifies MRSA, MSSA and coagulase-negative staphylococci. The discordant results were from rarely occurring clinical isolates and were expected limitations of the assay. This kit has the potential to reduce the time to effective antibiotics and minimise the use of unnecessary antibiotics and associated costs.

Varicella zoster virus: an under-recognised cause of central nervous system infections?

BACKGROUND: Varicella zoster virus (VZV) causes infections of the central nervous system (CNS) manifesting as meningitis or encephalitis. It is not commonly tested in CNS infections when compared with enterovirus (EV) and herpes simplex virus 1 (HSV-1) and 2 (HSV-2). Cerebrospinal fluid (CSF) findings of viral CNS infections are thought to be comparable. AIMS: To describe the manifestations of VZV CNS infections and ascertain if there is a predominant syndrome. To compare CSF parameters of VZV with EV, HSV-1 and HSV-2. METHODS: Retrospective study at two hospitals in Brisbane, reviewing medical notes and laboratory information system for results between January 2001 and 2019. The following parameters were recorded - disease classification, presence of rash, duration of symptoms prior to hospitalisation, length of admission, duration of antiviral treatment and 30-day mortality. CSF biochemistry, cell count (differential), PCR for VZV, EV, HSV-1 and HSV-2 were recorded. Statistical analysis of CSF parameters included Student's t-test and linear regression. RESULTS: Incidence of meningitis was comparable to encephalitis (44 vs 39%) in 52 cases. CSF protein in VZV was significantly elevated compared with EV (median 1121 vs 569 mg/L; P < 0.001) as was CSF monocytosis (96% vs 61%; P < 0.001). CSF parameters between VZV, HSV-1 and HSV-2 were similar. VZV had a higher incidence than HSV-1 or 2, while it was tested one-third as often. CONCLUSIONS: VZV CNS infection cannot be predicted by syndrome. CSF findings are markedly different from EV but like HSV-1 and 2. VZV should be routinely tested with HSV-1 and 2 when viral CNS infection is suspected.

Case report: a fatal case of Aspergillus felis infection in an immunocompetent host.

We report a fatal case of Aspergillus felis invasive rhinosinusitis with secondary cerebral abscesses in an immunocompetent host despite aggressive surgical debridement and combination antifungals. Whilst this organism is known to cause fatalities in cats, only a few cases in humans have been documented, all of which had significant immunosuppression. This is the first human death due to A. felis described in an immunocompetent host.