Elisabeth Holden

Staphylococcus aureus bacteraemia in a UK tertiary referral centre: a ‘transoesophageal echocardiogram for all’ policy

OBJECTIVES Infective endocarditis (IE) is a feared complication in up to 38% of cases of Staphylococcus aureus bacteraemia (SAB). BSAC guidelines recommend echocardiography in all cases of SAB. The aim of this study was to determine the incidence of IE in SAB using transoesophageal echocardiography (TOE) as the first step in diagnostic imaging. This study also sought to identify clinical predictors that could improve stratification of those with and without IE. METHODS A guideline was implemented that any SAB resulted in the microbiology department (i) recommending that the patient be referred for TOE and (ii) notifying the echocardiography department, resulting in streamlined listing of the patient for TOE. All cases of SAB were then assessed prospectively at University Hospitals Birmingham NHS Foundation Trust between September 2011 and October 2012. Previously identified risk factors for complicated S. aureus bacteraemia were recorded. RESULTS There were 98 SAB episodes in total. TOE was performed in 58 (59%) with a further 22 episodes imaged by transthoracic echocardiography alone. IE was diagnosed overall in 13 (16%) cases investigated with echocardiography. No risk factor for IE other than presence of a cardiac device was detected in this group (P = 0.013). CONCLUSIONS The rate of IE found in SAB is high when TOE is performed first line. There are no clear risk factors to improve yield or the type of echocardiography to be performed. Echocardiography should be performed in all cases and TOE should be considered where it is expected to influence management, as long as local resources allow.

Engineering waterborne Pseudomonas aeruginosa out of a critical care unit

OBJECTIVE To describe engineering and holistic interventions on water outlets contaminated with Pseudomonas aeruginosa and the observed impact on clinical P. aeruginosa patient isolates in a large Intensive Care Unit (ICU). DESIGN Descriptive study. SETTING Queen Elizabeth Hospital Birmingham (QEHB), part of University Hospitals Birmingham (UHB) NHS Foundation Trust is a tertiary referral teaching hospital in Birmingham, UK and provides clinical services to nearly 1 million patients every year. METHODS Breakpoint models were used to detect any significant changes in the cumulative yearly rates of clinical P. aeruginosa patient isolates from August 2013-December 2016 across QEHB. RESULTS Water sampling undertaken on the ICU indicated 30% of the outlets were positive for P. aeruginosa at any one time. Molecular typing of patient and water isolates via Pulsed Field Gel Electrophoresis suggested there was a 30% transmission rate of P. aeruginosa from the water to patients on the ICU. From, February 2014, QEHB implemented engineering interventions, consisting of new tap outlets and PALL point-of-use filters; as well as holistic measures, from February 2016 including a revised tap cleaning method and appropriate disposal of patient waste water. Breakpoint models indicated the engineering and holistic interventions resulted in a significant (p<0.001) 50% reduction in the number of P. aeruginosa clinical patient isolates over a year. CONCLUSION Here we demonstrate that the role of waterborne transmission of P. aeruginosa in an ICU cannot be overlooked. We suggest both holistic and environmental factors are important in reducing transmission.

Waterborne Pseudomonas aeruginosa transmission in a hematology unit

Background: Pseudomonas aeruginosa is an important nosocomial pathogen that commonly colonizes hospital water supplies, including in taps and sinks. We report the transmission of P. aeruginosa from water to patients in a clinical hematology setting. Methods: P. aeruginosa from water samples were compared to clinical isolates from hematology ward patients, via molecular typing (pulsed field gel electrophoresis). Results: P. aeruginosa cultured from blood cultures from 3 patients was indistinguishable from water strains, by molecular typing. Based on infection control inspections, the transmission event was surmised to be due to cleaning of equipment, specifically an infusion therapy procedure tray used to transport intravenous drugs to patients, with water from an outlet colonized by P. aeruginosa. Conclusion: We show the importance of holistic factors, such as disposal of patient waste water, cleaning of tap outlets, and cleaning of medical equipment, in the transmission of P. aeruginosa, and demonstrate that the role of waterborne transmission of this organism in a hematology setting cannot be overlooked. We suggest that appropriate management of water, including both holistic and engineering interventions, is needed to stop transmission of P. aeruginosa from water to patients.

Decontamination of an Extracorporeal Membrane Oxygenator Contaminated With Mycobacterium chimaera

Water samples taken from extracorporeal membrane oxygenator (ECMO) devices used at University Hospitals Birmingham yielded high total viable counts (TVCs) containing a variety of microorganisms, including M. chimaera. Disinfection resulted in the reduction of TVCs and eradication of Mycobacterium chimaera. Weekly disinfection and water sampling are required to manage the water quality in these devices. Infect Control Hosp Epidemiol 2017;38:1244-1246.

Unmasking leading to a healthcare worker Mycobacterium tuberculosis transmission

BACKGROUND Mycobacterium tuberculosis is a major health burden worldwide. The disease may present as an individual case, community outbreak, or more rarely as a nosocomial outbreak. Even in countries with a low prevalence such as the UK, tuberculosis (TB) presents a risk to healthcare workers (HCWs). AIM To report an outbreak which manifested 12 months after a patient with pulmonary tuberculosis was admitted to Queen Elizabeth Hospital Birmingham. METHODS We present the epidemiological and outbreak investigations; the role of whole genome sequencing (WGS) in identifying the outbreak and control measures to prevent further outbreaks. FINDINGS Subsequent to a diagnosis of open TB in a patient, transmission was confirmed in one HCW who had active TB; HCWs with latent TB infection (LTBI) were also identified among seven HCW contacts of the index patient. Of note, all the LBTI patients had other risk factors for TB. Routine use of WGS identified the outbreak link between the index patient and the HCW with active TB disease, and informed our investigations. CONCLUSION Exposure most likely occurred during an aerosol-generating procedure (AGP) which was done in accordance with national guidance at that time without using respiratory protection. Enhanced control measures were implemented following the outbreak.

Can a toxin gene NAAT be used to predict toxin EIA and the severity of Clostridium difficile infection

BackgroundDiagnosis of C. difficile infection (CDI) is controversial because of the many laboratory methods available and their lack of ability to distinguish between carriage, mild or severe disease. Here we describe whether a low C. difficile toxin B nucleic acid amplification test (NAAT) cycle threshold (CT) can predict toxin EIA, CDI severity and mortality.MethodsA three-stage algorithm was employed for CDI testing, comprising a screening test for glutamate dehydrogenase (GDH), followed by a NAAT, then a toxin enzyme immunoassay (EIA). All diarrhoeal samples positive for GDH and NAAT between 2012 and 2016 were analysed. The performance of the NAAT CT value as a classifier of toxin EIA outcome was analysed using a ROC curve; patient mortality was compared to CTs and toxin EIA via linear regression models.ResultsA CT value ≤26 was associated with ≥72% toxin EIA positivity; applying a logistic regression model we demonstrated an association between low CT values and toxin EIA positivity. A CT value of ≤26 was significantly associated (p = 0.0262) with increased one month mortality, severe cases of CDI or failure of first line treatment. The ROC curve probabilities demonstrated a CT cut off value of 26.6.DiscussionsHere we demonstrate that a CT ≤26 indicates more severe CDI and is associated with higher mortality. Samples with a low CT value are often toxin EIA positive, questioning the need for this additional EIA test.ConclusionsA CT ≤26 could be used to assess the potential for severity of CDI and guide patient treatment.