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Using Staphylococcus aureus bacteraemia surveillance to develop targeted prevention programs
Staphylococcus aureus bacteraemia (SAB) is associated with significant mortality and is frequently regarded as preventable in settings where onset of infection is associated with delivery of healthcare. As such, mandatory reporting of SAB has occurred in Scotland since 2001. In the setting of apparent inability to reduce the number of SAB episodes in Scotland, enhanced surveillance was instituted in 2009. Morris AK and Russell CD (J Hosp Infect 2016; 93:169-174) report the value of enhanced surveillance to suitably inform infection prevention programs in a single health region in Scotland (Fife).
Prospective surveillance was performed in Fife between 2009 and 2014. The region contains one acute hospital with a single diagnostic laboratory. A clinical microbiologist reviewed all SAB events at the bedside to determine the origin and source of infection, collect demographic data, and formulate a management plan. Each episode of SAB was classified as hospital-acquired infection, healthcare-associated infection, community-acquired infection or non-hospital-acquired.
In total, 556 SAB episodes occurred during the studied period. Seventy-two (12.9%) were due to methicillin-resistant S. aureus. The 30-day all-cause mortality was 22.7%. Most SAB episodes were hospital-acquired (46.9%) or healthcare-associated (37.6%), with only 14.4% acquired in the community. Community-acquired events had 30-day mortality of 8.7%, whereas mortality rates in healthcare-associated and hospital-acquired groups were 16.3% and 31.4%, respectively. The source of SAB was identified in 88.1% of events. SAB related to intravenous drug use was the most frequent cause of community-acquired events, and episodes related to respiratory tract and skeletal/joint infections were more likely in community-acquired events. For hospital-acquired infections, the most frequent source was a vascular access device (46.4%), and peripheral venous cannulae accounted for most of these (43.9%).
Healthcare-associated infections were most frequently associated with medical devices other than venous access devices.
Enhanced surveillance to determine SAB origin of infection and source of bacteraemia effectively provides data to directly inform prevention activities. Methods employed in this study would be of benefit in Australian facilities currently performing SAB surveillance, to enable development of targeted quality improvement programs.
Is Pneumocystis jirovecii a transmissible organism in healthcare settings?
Pneumocystis jirovecii pneumonia (PCP) results in morbidity and mortality in immunocompromised patients. A range of predisposing conditions has been associated with infection, including malnutrition, HIV infection, renal transplantation, haematological malignancy and connective tissue disorders. Some reports of individual outbreaks have suggested a common-source with confirmation by molecular typing. Yiannakis EP and Boswell TC (J Hosp Infect 2016; 93:1-8) sought to identify and evaluate all published clusters and outbreaks of PCP, to determine the evidence for different modes of transmission (including inter-human transmission).
A systematic review of literature published between 1980 and 2015 was performed. Studies were eligible for inclusion if they described the occurrence of PCP in excess of what would normally be expected in the defined adult or paediatric population. Standardised data were collected from eligible studies, including features of the outbreak, the outbreak setting, application of molecular typing methods, and results of environmental sampling (if performed).
Of 177 articles initially identified, 22 were found to fulfil inclusion criteria, and a further 7 articles were found by secondary search methods (total of 29 studies included). These described a total of 30 outbreaks. Twenty-one (70%) occurred in Europe, and the median number of patients affected in outbreaks was 12.5. Predominantly, adult patients were affected, with only 3 outbreaks reported in paediatric populations. In the majority, patients had undergone solid organ transplantation, predominantly renal transplantation. Genotyping was performed in 16 (57%) of studies, and a single/predominant strain was identified in 13/16 (81%). Environmental sampling was conducted in only 5 outbreaks, with Pneumocystis isolated from the environment in 3 instances. In all outbreaks, patients had received either no or suboptimal PCP prophylaxis. Outbreaks were managed by initiation of
chemoprophylaxis in the affected patient cohort. In only 2 instances, isolation of symptomatic patients was also performed.
Overall, findings suggest the existence of healthcare-associated Pneumocystis jirovecii infections. However, potential limitations of this systematic review must be acknowledged, including publication bias and lack of population studies to determine relative prevalence of Pneumocystis subtypes in community and non-hospitalised settings. Notwithstanding these limitations, current guidelines of the Centers for Disease Control and Prevention appear to be justified, at least for renal transplant units. These include the avoidance of placement of a patient with PCP in the same room as an immunocompromised patient. Future studies must focus upon the role of asymptomatic carriers, and the potential role of environmental sources of infection.
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