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Objectives Vancomycin-intermediate Staphylococcus aureus (VISA) is associated with genetic changes that may also impact upon pathogenicity. In the current study, we compared the virulence of clinical VISA strains with their isogenic vancomycin-susceptible progenitors (VSSA). Methods Production of the critical virulence protein, α toxin, was assessed using Western blot analysis and was correlated to agr activity using a bioluminescent agr -reporter. Cytotoxicity and intracellular persistence were compared ex vivo for VSSA and VISA within non-professional phagocytes (NPP). Virulence and host immune responses were further explored in vivo using a murine model of bacteraemia. Results VISA isolates produced up to 20-fold less α toxin compared with VSSA, and this was corroborated by either loss of agr activity due to agr mutation, or altered agr activity in the absence of mutation. VISA were less cytotoxic towards NPP and were associated with enhanced intracellular persistence, suggesting that NPP may act as a reservoir for VISA. Infection with VSSA strains produced higher mortality in a murine bacteraemia model (≥90% 7-day mortality) compared with infection with VISA isolates (20% to 50%, p <0.001). Mice infected with VISA produced a dampened immune response (4.6-fold reduction in interleukin-6, p <0.001) and persistent organ bacterial growth was observed for VISA strains out to 7 days. Conclusions These findings highlight the remarkable adaptability of S. aureus , whereby, in addition to having reduced antibiotic susceptibility, VISA alter the expression of pathogenic factors to circumvent the host immune response to favour persistent infection over acute virulence. [ABSTRACT FROM AUTHOR]

Objectives To define standardized endpoints to aid the design of trials that compare antibiotic therapies for bloodstream infections (BSI). Methods Prospective studies, randomized trials or registered protocols comparing antibiotic therapies for BSI, published from 2005 to 2016, were reviewed. Consensus endpoints for BSI studies were defined using a modified Delphi process. Results Different primary and secondary endpoints were defined for pilot (small-scale studies designed to evaluate protocol design, feasibility and implementation) and definitive trials (larger-scale studies designed to test hypotheses and influence clinical practice), as well as for Staphylococcus aureus and Gram-negative BSI. For pilot studies of S. aureus BSI, a primary outcome of success at day 7 was defined by: survival, resolution of fever, stable/improved Sequential Organ Failure Assessment (SOFA) score and clearance of blood cultures, with no microbiologically confirmed failure up to 90 days. For definitive S. aureus BSI studies, a primary outcome of success at 90 days was defined by survival and no microbiologically confirmed failure. For pilot studies of Gram-negative BSI, a primary outcome of success at day 7 was defined by: survival, resolution of fever and symptoms related to BSI source, stable or improved SOFA score and negative blood cultures. For definitive Gram-negative BSI studies, a primary outcome of survival at 90 days supported by a secondary outcome of success at day 7 (as previously defined) was agreed. Conclusions These endpoints provide a framework to aid future trial design. Further work will be required to validate these endpoints with respect to patient-centred clinical outcomes. [ABSTRACT FROM AUTHOR]

Predicting which lung transplant recipients (LTR) will develop CMV infection remains challenging. We previously explored the Quantiferon®-CMV (QF-CMV) assay and found that R+ patients were mostly QF-CMV positive, with many developing CMV infection despite this result. The aim of this retrospective cohort study was to explore two biomarkers of global immunity, the absolute lymphocyte count (ALC) and the mitogen component of the QF-CMV assay, as predictors of CMV infection in R+ LTR. R+ LTR who received 5 months of valganciclovir prophylaxis and had QF-CMV testing performed at the time of discontinuation were included. Cox models were used to evaluate ALC and mitogen values as predictors of CMV infection >150 IU/mL in blood and/or bronchoalveolar lavage fluid (BAL). Optimal cutoffs were calculated with receiver-operating characteristic curves. Our cohort included 150 LTR (92 D+/R+, 58 D-/R+). Median prophylaxis duration was 5.3 months (IQR 5.1-5.6). QF-CMV results were mostly positive (137/150, 91%) with 8 (5%) testing negative and 5 (3%) indeterminate. Overall, CMV infection occurred in 97 (65%), including 37 (25%) in blood and 90 (60%) in BAL. Patients with a CMV seropositive donor (D+) were more likely to develop CMV infection (HR 2.26, 95% CI 1.45-3.53, p<0.001). Median ALC values amongst patients who did and did not subsequently develop CMV infection were 1.12 cells/μL (IQR 0.56-1.79) and 1.41 cells/μL (IQR 1.09-1.70) respectively (p=0.05). Mitogen values were lower in patients who had CMV infection (median 6.22 IU/mL, IQR 1.8-10.0 vs. 3.12 IU/mL, 0.89-8.91, p=0.02). After adjusting for serostatus, patients with an ALC ≤1.0 × 1000 cells/μL (HR 2.10, 95% CI 1.38-3.18, p<0.001) and a mitogen value ≤3.64 IU/mL (HR 1.66, 95% CI 1.11-2.48, p=0.014) were more likely to experience CMV infection. Within R+ LTR the ALC and the mitogen component of the QF-CMV assay were able to predict post-prophylaxis CMV infection. D+ patients were also higher risk. These values could be used to risk-stratify patients and inform decision making regarding duration of antiviral prophylaxis and frequency of virologic monitoring. Additional studies are needed to further explore the role of immune biomarkers in the prediction of CMV and other opportunistic infections in LTR. [ABSTRACT FROM AUTHOR]

Cytomegalovirus (CMV) infection contributes to morbidity and mortality in heart transplant recipients (HTR). Donor positive, recipient negative (D+/R-) patients are high risk and generally receive antiviral prophylaxis. The burden of CMV infection in recipient seropositive (R+) HTR is less clear, with preventative recommendations mostly extrapolated from other solid organ transplant groups. The aim of this retrospective cohort study was to define the incidence, severity of & risk factors for CMV infection in R+ HTR. CMV seropositive HTR were included (2010-2019). Antiviral prophylaxis was not routinely used, with clinical monitoring the local standard of care. Data were collected from medical records, & patients followed for a year post-transplant. The incidence of CMV infection, including tissue invasive disease, was quantified, & predisposing/mitigating factors identified. We also assessed the association of CMV with adverse outcomes including prolongation of hospitalization & death. Our cohort included 155 R+ HTR (median age 53yrs, 72% male, 56% D+/R+, 68% basiliximab & 8% thymoglobulin induction). Valganciclovir prophylaxis was used in 35 (23%) for a median of 103 days (IQR 78-222). CMV infection occurred in 27 (17%) patients at a median onset of 67 days (41-124), median peak viral load was 1250 IU/mL (221-6539) & 18/27 (67%) required readmission. End-organ disease occurred in 22 (82%) & was most commonly gastrointestinal (52%). CMV infection was associated with a longer length of stay (27 vs. 20 days, HR 1.02, 95% CI 1.00-1.03, p=0.02), higher rate of intensive care readmission (26% vs. 9%, 4.57, 1.76-11.88, p=0.002), & increased mortality (33% vs. 8%, HR 9.11, 3.49-23.8, p<0.001). Valganciclovir prophylaxis was protective for CMV (4% vs. 27%, 0.094, 0.012-0.75, p=0.025), even though patients receiving it were more likely to have had thymoglobulin induction (31% vs. 2%, OR 27.04, 5.63-129.88, p<0.001). CMV infection occurred in 17% of R+ HTR & was associated with a high burden of disease, worse post-transplant outcomes & increased mortality. Patients who received valganciclovir prophylaxis were less likely to develop CMV infection. These findings support the routine use of CMV preventative strategies such as antiviral prophylaxis following heart transplantation in all CMV R+ patients. [ABSTRACT FROM AUTHOR]

Infections remain important contributors to mortality in hematopoietic stem cell transplantation ( HSCT). Method We studied the evolving epidemiology and trends in susceptibility of bacterial and Candida isolates at an Australian HSCT center. A total of 528 HSCTs in 508 patients were performed from April 2001 to May 2010. A total of 605 isolates were eligible for study inclusion; 318 (53%) were gram-positive, 268 (44%) were gram-negative, and 19 (3%) were Candida species. Results The most common site for isolates was blood (380 isolates, 63%). Staphylococcus aureus was the most common gram-positive organism ( n = 107, 34%), but trends to increasing coagulase-negative staphylococci ( P = 0.002) and vancomycin-resistant Enterococcus ( P < 0.001) were observed. Escherichia coli was the most common gram-negative isolate ( n = 74, 28%). Fluoroquinolone resistance increased with widespread use of protocol fluoroquinolone prophylaxis ( P = 0.001). Carbapenem resistance was found in 44% of Pseudomonas or Acinetobacter isolates. Bloodstream infection with a multidrug-resistant organism (odds ratio 3.61, 95% confidence interval: 1.40-9.32, P = 0.008) was an independent predictor of mortality at 7 days after a positive blood culture. Conclusions Antimicrobial resistance is an increasing problem in this vulnerable patient population, and not only has an impact on choice of empiric therapy for febrile neutropenia but also on mortality. [ABSTRACT FROM AUTHOR]

Purpose Determining the optimal level of immunosuppression in lung transplant (LT) recipients is challenging. The Quantiferon®-Monitor (QFM) is a novel immune function assay that measures interferon-γ after stimulation with ligands for the innate & adaptive immune system. The aim of this prospective cohort study was to assess the relationships between immunosuppression and QFM results, and the clinical utility of QFM as a predictor of infection/rejection in LT. Methods QFM was tested pre & at 2, 6, 12, 24 & 52 weeks post-LT. Standard immunosuppression included tacrolimus, azathioprine, prednisone & basiliximab in patients with limited renal reserve. Patients were assessed over 1yr for rejection & infection. Results 80 LT patients were recruited from 2015-17 (median age 61, 60% male, 86% bilateral LT and 50% received basiliximab). Pre-transplant QFM results were lower in patients receiving glucocorticoids (median 67 IU/mL, IQR 9-244 vs. 314, 67-499, p=0.01) and those testing cytomegalovirus (CMV) seronegative (71, 5-262 vs. 230, 58-499, p=0.01). QFM values decreased significantly post-transplant then progressively increased (Figure). Trough tacrolimus levels & prednisone doses were associated with post-transplant QFM levels (p<0.01). There was no difference in QFM values in patients who received basiliximab but those without prior immunity to CMV (n=29) consistently had lower post-transplant results (p<0.01). Overall, CMV viremia occurred in 44% (>1000 copies/mL in 15%), respiratory viral infections in 40% & positive BAL bacterial cultures in 64%. 9 patients (11%) experienced rejection, 4 within 30 days post-transplant. 76% were readmitted & 5 died within 1 yr. QFM results at 2 & 6 weeks were not associated with any of these outcomes. Conclusion Our study demonstrated an association between tacrolimus levels, prednisolone dose & QFM results but was underpowered to detect differences in clinical outcomes. CMV serostatus appeared to have an impact on QFM results both pre- & post-transplant. [ABSTRACT FROM AUTHOR]

Purpose Medihoney is routinely applied to the exit site of Ventricular Assist Device (VAD) drivelines in patients in many Australian hospitals to prevent driveline infections. Its effectiveness as a prophylactic measure remains unclear. We performed a comprehensive in vitro study using microbiological assays that closely mimic the in vivo environment of the driveline exit-site to assess the effectiveness of medihoney in preventing biofilm-related driveline infections. Methods Antimicrobial efficacy testing of medihoney was performed against 24 clinically-relevant bacterial and fungal strains grown as planktonic and biofilm cells. The minimum inhibitory concentration (MIC), minimum biofilm inhibitory concentration, minimum eradication concentration of medihoney, and the activity of individual components of medihoney were assessed. A colony biofilm assay and a drip-flow biofilm reactor assay that mimic chronic wounds and the driveline exit site were used to evaluate medihoney activity in inhibiting early adherent organism monolayers and mature biofilms. Results Medihoney demonstrated activity against planktonic organism cells in 5/6 S. aureus strains, 6/6 of S. epidermidis strains, 1/6 of P. aeruginosa strains and 4/6 of Candida strains using a qualitative disk diffusion susceptibility assay and a quantitative broth microdilution assay [MICs, 10% weight/volume (W/V) medihoney concentrations]. Higher concentrations of medihoney (30-50%, W/V) were required to inhibit the growth of biofilm cells. Eradication of biofilms could not be achieved by medihoney, even at the highest concentration studied. The antibiofilm properties of medihoney were multi-faceted, including sugar content, pH, osmolality and the proposed active ingredient, methylglyoxal (MGO). MGO actually played a less important role than other medihoney characteristics. The colony biofilm assay and the drip flow biofilm reactor showed that medihoney was unable to prevent the maturation of biofilms after early organism adherence, and only had a weak activity against established biofilms. Conclusion Our work suggests a suboptimal effectiveness of medihoney in preventing driveline exit site infections due to biofilm development, warranting further clinical trials before its widespread use can be justified. [ABSTRACT FROM AUTHOR]