Impact of mupirocin resistance on the transmission and control of healthcare-associated MRSA

Journal article

Objectives: The objectives of this study were to estimate the relative transmissibility of mupirocin-resistant (MupR) and mupirocin-susceptible (MupS) MRSA strains and evaluate the long-term impact of MupR on MRSA control policies.

Methods: Parameters describing MupR and MupS strains were estimated using Markov chain Monte Carlo methods applied to data from two London teaching hospitals. These estimates parameterized a model used to evaluate the long-term impact of MupR on three mupirocin usage policies: 'clinical cases', 'screen and treat' and 'universal'. Strategies were assessed in terms of colonized and infected patient days and scenario and sensitivity analyses were performed.

Results: The transmission probability of a MupS strain was 2.16 (95% CI 1.38–2.94) times that of a MupR strain in the absence of mupirocin usage. The total prevalence of MupR in colonized and infected MRSA patients after 5 years of simulation was 9.1% (95% CI 8.7%–9.6%) with the 'screen and treat' mupirocin policy, increasing to 21.3% (95% CI 20.9%–21.7%) with 'universal' mupirocin use. The prevalence of MupR increased in 50%–75% of simulations with 'universal' usage and .10% of simulations with 'screen and treat' usage in scenarios where MupS had a higher transmission probability than MupR.

Conclusions: Our results provide evidence from a clinical setting of a fitness cost associated with MupR in MRSA strains. This provides a plausible explanation for the low levels of mupirocin resistance seen following 'screen and treat' mupirocin usage. From our simulations, even under conservative estimates of relative transmissibility, we see long-term increases in the prevalence of MupR given 'universal' use.

Authors: Deeny, SR; Worby, C; Tosas Auguet, O; Cooper, B; Edgeworth, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Journal of Antimicrobial Chemotherapy
• Volume: 70
• Issue: 12
• Pages: 3366–3378
• Publication date: 2015-09-03
• DOI: 10.1093/jac/dkv249
• EISSN: 1460-2091
• ISSN: 0305-7453