Actin Dynamics as a Multiscale Integrator of Cellular Guidance Cues

Migrating cells must integrate multiple, competing external guidance cues. However, it is not well understood how cells prioritize among these cues. We investigate external cue integration by monitoring the response of wave-like, actin-polymerization dynamics, the driver of cell motility, to combinations of nanotopographies and electric fields in neutrophil-like cells. The electric fields provide a global guidance cue, and approximate conditions at wound sites in vivo. The nanotopographies have dimensions similar to those of collagen fibers, and act as a local esotactic guidance cue. We find that cells prioritize guidance cues, with electric fields dominating long-term motility by introducing a unidirectional bias in the locations at which actin waves nucleate. That bias competes successfully with the wave guidance provided by the bidirectional nanotopographies.

Cortical waves mediate the cellular response to electric fields

Electrotaxis, the directional migration of cells in a constant electric field, is important in regeneration, development, and wound healing. Electrotaxis has a slower response and a smaller dynamic range than guidance by other cues, suggesting that the mechanism of electrotaxis shares both similarities and differences with chemical-gradient-sensing pathways. We examine a mechanism centered on the excitable system consisting of cortical waves of biochemical signals coupled to cytoskeletal reorganization, which has been implicated in random cell motility. We use electro-fused giant Dictyostelium discoideum cells to decouple waves from cell motion and employ nanotopographic surfaces to limit wave dimensions and lifetimes. We demonstrate that wave propagation in these cells is guided by electric fields. The wave area and lifetime gradually increase in the first 10 min after an electric field is turned on, leading to more abundant and wider protrusions in the cell region nearest the cathode. The wave directions display 'U-turn' behavior upon field reversal, and this switch occurs more quickly on nanotopography. Our results suggest that electric fields guide cells by controlling waves of signal transduction and cytoskeletal activity, which underlie cellular protrusions. Whereas surface receptor occupancy triggers both rapid activation and slower polarization of signaling pathways, electric fields appear to act primarily on polarization, explaining why cells respond to electric fields more slowly than to other guidance cues.

Infection prevention quality indicators in aged care: ready for a national approach

Accreditation standards for Australian aged care homes include the requirement for programs to ensure infections are controlled. Effective infection prevention programs are supported by surveillance data providing the impetus for quality improvement and facilitating evaluation of interventions at the facility level. In 2016, infection control professionals employed in Victorian public-sector residential aged care services were surveyed to examine the nature and resourcing of local infection prevention programs and monitoring activities. Overall, 164 services participated (90% response rate). A high proportion (84%) reported executive support for infection surveillance, with mean allocation of 12h per fortnight per facility for infection prevention activities. Current surveillance activities included monitoring of infections and antimicrobial use (90%), influenza vaccination compliance for staff (96%) and residents (76%) and monitoring of infection due to significant organisms (84%). A successful statewide program including eight quality indicators has subsequently been implemented in Victoria. We suggest that a national focus could strengthen this framework, ensuring a uniform strategy with enhanced benchmarking capacity. Stakeholder engagement and refinement of appropriate indicators for monitoring quality improvement in public, not-for-profit and private sectors within aged care is required.

Central and peripheral line-associated bloodstream infections in Australian neonatal and paediatric intensive care units: findings from a comprehensive Victorian surveillance network, 2008-2016

BACKGROUND

Healthcare-associated infections in neonatal and paediatric populations are associated with poorer outcomes and healthcare costs, and surveillance is a necessary component of prevention programmes.

AIM

To evaluate burden of illness, aetiology, and time-trends for central and peripheral line-associated bloodstream infection (CLABSI and PLABSI) in Australian neonatal and paediatric intensive care units (ICUs) between July 1^st, 2008 and December 31^st, 2016.

METHODS

Using National Healthcare Safety Network methods, surveillance in neonatal and paediatric units was performed by hospitals participating in the Victorian Healthcare Associated Infection Surveillance System. Mixed effects Poisson regression was used to model infections over time.

FINDINGS

Overall, 82 paediatric CLABSI events were reported during 37,125 CVC-days (2.21 per 1000 CVC-days), 203 neonatal CLABSI events were reported during 92,169 CVC-days (2.20 per 1000 CVC-days), and 95 neonatal PLABSI events were reported during 142,240 peripheral line-days (0.67 per 1000 peripheral line-days). Over time, a significant decrease in quarterly risk for neonatal CLABSI events was observed (risk ratio (RR): 0.98; 95% confidence interval: 0.97-0.99; P = 0.023) and this reduction was significant for the 751-1000 g birth weight cohort (RR: 0.97; P = 0.015). Most frequently, coagulase-negative Staphylococcus spp. (24.2%) and Staphylococcus aureus (16.1%) were responsible for CLABSI events. A significant reduction in Gram-negative neonatal infections was observed (annual RR: 0.85; P < 0.001).

CONCLUSION

CLABSI rates in neonatal and paediatric ICUs in our region are low, and neonatal infections have significantly diminished over time. Evaluation of infection prevention programmes is required to determine whether specific strategies can be implemented to further reduce infection risk.

Validation of healthcare-associated infection surveillance in smaller Australian hospitals

A validation study was conducted in smaller (<100 acute beds) Victorian hospitals to evaluate case detection for Staphylococcus aureus bloodstream (SAB), meticillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE) infections. Overall, 142 infections were identified in 20 hospitals. For routine surveillance of SAB events, sensitivity was 74.4% and specificity was 100.0%. For MRSA infections, sensitivity was 47.5% and specificity was 90.9%. All confirmed VRE infections were reported correctly. Of unreported SAB and MRSA infections, 80% (N = 16) and 83.9% (N = 26) were community-associated infections, respectively. Future programme refinements include targeted education to ensure appropriate application of case definitions, particularly those including community onset.

Epidemiology of Clostridium difficile infections in Australia: enhanced surveillance to evaluate time trends and severity of illness in Victoria, 2010-2014

BACKGROUND

With epidemic strains of Clostridium difficile posing a substantial healthcare burden internationally, there is a need for longitudinal evaluation of Clostridium difficile infection (CDI) events in Australia.

AIM

To evaluate time trends and severity of illness for CDI events in Australian healthcare facilities.

METHODS

All CDI events in patients admitted to Victorian public hospitals between 1(st) October 2010 and 31(st) December 2014 were reported to the Victorian Healthcare Associated Infection Surveillance System. CDI was defined as the isolation of a toxin-producing C. difficile organism in a diarrhoeal specimen, and classified as community-associated (CA-CDI) or healthcare-associated (HA-CDI). Severe disease was defined as admission to an intensive care unit, requirement for surgery and/or death due to infection. Time trends were examined using a mixed-effects Poisson regression model, and the Walter and Edward test of seasonality was applied to evaluate potential cyclical patterns.

FINDINGS

In total, 6736 CDI events were reported across 89 healthcare facilities. Of these, 4826 (71.6%) were HA-CDI, corresponding to a rate of 2.49/10,000 occupied bed days (OBDs). The incidence of HA-CDI was highest in the fifth quarter of surveillance (3.6/10,000 OBDs), followed by a reduction. Severe disease was reported in 1.66% of events, with the proportion being significantly higher for CA-CDI compared with HA-CDI (2.21 vs 1.45%, P = 0.03). The highest and lowest incidence of HA-CDI occurred in March and October, respectively.

CONCLUSIONS

A low incidence of HA-CDI was reported in Victoria compared with US/European surveillance reports. Seasonality was evident, together with diminishing HA-CDI rates in 2012-2014. Severe infections were more common in CA-CDI, supporting future enhanced surveillance in community settings.

Reporting Surgical Site Infections Following Primary and Revision Hip Arthroplasty— One Size Does Not Fit All

The risk of surgical site infection (SSI) is greater after revision hip arthroplasty than after primary procedures. While this is accepted as a clinical phenomenon, standardized surveillance strategies for healthcare-associated infections, including SSIs, do not currently take this into consideration. Most notably, the National Nosocomial Infections Surveillance (NNIS) risk index for stratification does not differentiate between primary and revision surgeries. Using data from a single US center, Leekha et al. recently demonstrated that the risk for SSI was almost twice as high after revision total hip arthroplasty when compared to primary total hip arthroplasty and that risk was even greater when deep incisional or organ/space infections were analyzed. The objective of this study was to compare SSI rates following primary and revision hip arthroplasty in a much larger Australian population to determine whether differences are accounted for by current risk indexing.

Interhospital Comparisons of Coronary Artery Bypass Graft Surgical Site Infection Rates Differ if Donor Sites Are Excluded

The advent of public reporting of hospital-acquired infection rates has sparked ongoing discussion about the most appropriate surveillance data to present. When we used different numerators to calculate rates of surgical site infection following coronary artery bypass graft surgery, we found that some hospitals' rates and their rankings were notably affected.

Implementation of standardised surveillance for Clostridium difficile infections in Australia: initial report from the Victorian Healthcare Associated Infection Surveillance System

Detection of a hypervirulent strain of Clostridium difficile in Victoria led to commencement of targeted surveillance for C. difficile infection in 2010. Cases were reported through the Victorian Healthcare Associated Infection Surveillance System. Between 1 October 2010 and 31 March 2011, 477 cases of C. difficile infection were identified; 11 (2.3%) secondary to a hypervirulent strain. Three hundred and seventy (1.7 per 10,000 occupied bed days) were healthcare associated. Data reflect successful implementation of continuous surveillance for C. difficile infection. With hypervirulent C. difficile infection now reported in other Australian states, development of a national data repository for C. difficile infection is necessary.

Compliance with surgical antibiotic prophylaxis--reporting from a statewide surveillance programme in Victoria, Australia

A statewide assessment of the compliance of surgical antibiotic prophylaxis (SAP) with guidelines was undertaken for large public hospitals in Victoria, Australia. This was carried out using data collected as part of a surveillance system for hospital-acquired infections. The study population comprised patients in Victorian public hospitals with >100 beds (N=27) undergoing cardiac surgical procedures, hip or knee arthroplasty, cholecystectomy, appendectomy, colon surgery or hysterectomy over a 21-month period. Australian guidelines recommend SAP for all 10 643 surgical procedures included in this study. Combining all procedures, 87% received SAP, the choice of antibiotic was concordant with guidelines for 53.3% of procedures, and the choice of antibiotic was considered to be 'adequate but not concordant' for 23.9% of procedures. SAP was considered to be inadequate for 18.9% of procedures. A large number of antibiotic regimens were utilized for cardiac and orthopaedic surgery. Documentation of timing of administration was not submitted for more than half of all procedures. Timing was concordant with guidelines for 76.4% of procedures when documented. Prophylactic antibiotic choice was generally more concordant with guidelines for cardiac and orthopaedic procedures than for other types of surgery. However, even for these procedures, where infections carry high morbidity, SAP was sometimes inadequate. Regular reporting on SAP compliance from data collected during surveillance for hospital-acquired infections is achievable. This should lead to improvements in both compliance and documentation.