Staphylococcus aureus bacteraemia (SAB) is the second most common source of positive blood cultures after Escherichia coli (E. coli) reported within NHS Scotland. Laboratory surveillance has been mandatory in Scotland for SAB since 2001 | Journal of Hospital Infection
Aim: To gain an understanding of the epidemiology of SAB cases and associated risk factors for healthcare and true community onset. Identifying these factors and patient populations most at risk allows focused improvement plans to be developed.
Methods: All NHS Boards within NHS Scotland take part in the mandatory enhanced surveillance collecting data by trained data collectors using nationally agreed definitions.
Findings: Between 1st October 2014 and 31st March 2016, 2256 episodes of SAB in adults were identified. The blood cultures were taken in 58 hospitals and across all 15 Scottish health boards. The data demonstrated that approximately one third of all SAB cases are true community cases. Vascular access devices (VAD) continue to be the most reported entry point (25.7%) in persons who receive healthcare, whereas, skin and soft tissue risk factors are present in all origins. A significant risk factor unique to community cases are in people who inject drugs (PWID).
Conclusion: Improvement plans for reduction of SAB should be more widely targeted than solely in hospital care settings.
Price, J.R. et al. (2017) The Lancet Infectious Diseases. 17(2) pp. 207–214
Background: Health-care workers have been implicated in nosocomial outbreaks of Staphylococcus aureus, but the dearth of evidence from non-outbreak situations means that routine health-care worker screening and S aureus eradication are controversial. We aimed to determine how often S aureus is transmitted from health-care workers or the environment to patients in an intensive care unit (ICU) and a high-dependency unit (HDU) where standard infection control measures were in place.
Interpretation: In the presence of standard infection control measures, health-care workers were infrequently sources of transmission to patients. S aureus epidemiology in the ICU and HDU is characterised by continuous ingress of distinct subtypes rather than transmission of genetically related strains.
Murphy, C.M. et al. Journal of Hospital Infection. Published online: 20 January 2017
Staphylococcus aureus cultures from name badge lanyards were phenotypically and genotypically indistinguishable from the wearer’s nasal carrier strains by pulsed field gel electrophoresis and antibiogram. Lanyards had a mean age of 22 months and hygiene was poor with only 9 % ever having been laundered. Molecular analysis showed that 26% of S. aureus nasal carriers shared an indistinguishable strain on their lanyard. Lanyards should not be recommended for staff in frontline clinical care.
Humphreys, H. et al. Journal of Hospital Infection. Published online: 18 June 2016
Image shows Staphylococcus aureus on ChromID CPS chromogenic agar. Isolate from a urine sample from a 45 year old catheterised male awaiting surgery for a bladder stone.
Surgical site infections (SSIs) are amongst the most common healthcare-associated infections and significantly contribute to patient morbidity and healthcare costs. Staphylococcus aureus is the most common microbial cause.
The epidemiology of S. aureus is changing, with the dissemination of newer clones and the emergence of mupirocin resistance. The prevention and control of SSIs is multi-modal and we have reviewed the evidence for the value of screening for nasal carriage of S. aureus and the subsequent decolonization of patients pre-operatively who are positive. Pre-operative screening, using culture- or molecular-based methods and the subsequent decolonization of patients positive for methicillin-susceptible S. aureus and methicillin resistant S. aureus (MRSA) reduces SSI and hospital stay. This applies especially to major clean surgery, such as cardiothoracic and orthopaedic, involving the insertion of implanted devices.
However, it requires a multi-disciplinary approach coupled with patient education. Universal decolonization pre-operatively without screening for S. aureus potentially compromises the capacity to monitor for the emergence of new clones of S. aureus, contributes to mupirocin resistance, and prevents the adjustment of surgical prophylaxis for MRSA, i.e. the replacement of a beta-lactam agent with a glycopeptides or alternative.
Almatroudi, A. et al. Journal of Hospital Infection. Published online: 12 April 2016
Image shows Staphylococcus aureus – macro photo x 10 of culture, characteristic gold/yellow colonies.
Background: Dry hospital environments are contaminated with pathogenic bacteria in biofilms, which suggests that current cleaning practices and disinfectants are failing.
Aim: To test the efficacy of sodium hypochlorite solution against Staphylococcus aureus dry-surface biofilms.
Methods: The Centers for Disease Control and Prevention Biofilm Reactor was adapted to create a dry-surface biofilm, containing 1.36×107S. aureus/coupon, by alternating cycles of growth and dehydration over 12 days. Biofilm was detected qualitatively using live/dead stain confocal laser scanning microscopy (CLSM), and quantitatively with sonicated viable plate counts and crystal violet assay. Sodium hypochlorite (1000 to 20,000 parts per million) was applied to the dry-surface biofilm for 10 min, coupons were rinsed three times, and residual biofilm viability was determined by CLSM, plate counts and prolonged culture up to 16 days. Isolates before and after exposure underwent minimum inhibitory concentration (MIC) and minimum eradication concentration (MEC) testing, and one pair underwent whole-genome sequencing.
Findings: Hypochlorite exposure reduced plate counts by a factor of 7 log10, and reduced biofilm biomass by a factor of 100; however, staining of residual biofilm showed that live S. aureus cells remained. On prolonged incubation, S. aureus regrew and formed biofilms. Post-exposure S. aureus isolates had MICs and MECs that were not significantly different from the parent strains. Whole-genome sequencing of one pre- and post-exposure pair found that they were virtually identical.
Conclusions: Hypochlorite exposure led to a 7-log kill but the organisms regrew. No resistance mutations occurred, implying that hypochlorite resistance is an intrinsic property of S. aureus biofilms. The clinical significance of this warrants further study.