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In low‑MRSA ICUs, switching from universal to targeted decolonization reduced MRSE bloodstream infections without raising overall bloodstream infection rates.

In intensive care units (ICUs) with low incidence of meticillin-resistant Staphylococcus aureus (MRSA), de-escalation from universal to targeted skin and nasal decolonization was associated with reduced rates of meticillin-resistant Staphylococcus epidermidis bloodstream infections (MRSE-BSI) and did not increase the incidence density of all bacterial and fungal bloodstream infections, according to findings published in The Lancet Microbe.

According to the research team, the widespread use of universal chlorhexidine–mupirocin bathing in ICUs has raised concerns about the potential for fostering multidrug-resistant Staphylococcus epidermidis (MRSE). Their before–and–after–control–impact analysis, spanning 13 years across two Scottish tertiary ICUs, provides data for critical care physicians to recalibrate the risk–benefit equation.

“We found that de‑escalation in the intervention site reduced multidrug‑resistant S epidermidis sequence types, particularly ST2,” wrote corresponding author Karolin Hijazi, PhD, of the University of Aberdeen, and study coauthors.

Methods in Brief

The research team reported that, between July 2009 and February 2022, ICU-1 treated all admissions with daily universal skin and nasal decolonization until February 1, 2019, when the practice shifted to targeting only proven MRSA carriers. ICU‑2 employed targeted decolonization throughout and served as the control.

The authors extracted incidence densities for all bloodstream infections (BSI), S. epidermidis BSI (SE-BSI), and MRSE-BSI per 1,000 occupied bed-days (OBDs) and coupled these with multilocus sequence typing, whole-genome sequencing, and phenotypic biocide-resistance profiling.

In the intervention ICU, S. epidermidis was identified in 334 (45%) of 735 bloodstream infections; 197 of these infections occurred before the implementation of the de-escalation intervention. In the control ICU, S. epidermidis was identified in 60% of 278 bloodstream infections, according to the authors.

De-escalation Reduces Proportion of SE-BSI

Results showed that universal de‑escalation in ICU‑1 did not increase aggregate BSI incidence but reduced MRSE‑BSI from 10.4 to 4.3 cases/1,000 OBDs. The probability that an SE‑BSI was meticillin‑resistant fell from 89.2% (95% credible interval 77.8–96.5) to 56.7% (34.3–77.5). No parallel change emerged in ICU‑2. MRSE-BSI density correlated positively with chlorhexidine consumption but not with mupirocin exposure, suggesting that antiseptic rather than nasal biocide pressure is involved in the selection of high-risk clones, according to the authors. Whole-genome analysis confirmed the contraction of mobile genetic elements encoding multidrug resistance and biofilm pathways after de-escalation.

“De‑escalation was associated with a reduced proportion of SE‑BSI due to multidrug‑resistant sequence types and reduced carriage of mobile genetic elements and genes for multidrug resistance and biofilm production, as observed by multilocus sequence typing and whole genome sequencing,” the researchers reported.

Call to Appraise Risks & Benefits

For ICUs operating in low-MRSA prevalence settings, these findings suggest that targeted, carrier-based decolonization can deliver meaningful reductions in MRSA-BSI without exposing patients to a broader BSI hazard. Regulation of biocide use may prevent unintended harms, the authors advised.

“We call on ICUs practicing universal skin and nasal decolonization to appraise risks and benefits of this practice in the context of their effect on the emergence and spread of MRSE,” researchers wrote.