Clonal variation in high- and low-level phenotypic and genotypic mupirocin resistance of MRSA isolates in south-east London

Abstract

Mupirocin resistance was identified in <10% of patients and varied significantly by clone, implying that changes in clonal epidemiology may have an important role in determining the prevalence of resistance in conjunction with selection due to mupirocin use.

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

“…Examining each MRSA ST separately would represent an important next step. Molecular analysis of MRSA isolates in this dataset 33 showed that mupirocin resistance was predominant in only a limited number of STs (ST36, ST8 and ST239/241), but rare in the dominant UK MRSA clone (ST22) or sporadic MLSTs. This suggests that changes in MRSA clonal epidemiology may also play a role in determining the long-term prevalence of mupirocin resistance.…”

“… 29 , 31 , 32 , 46 We did not consider the influence of the de novo development of resistance in patients after treatment or the influence of patient transfers from settings of high mupirocin resistance prevalence, which may play a role in determining the higher mupirocin prevalence evident in our dataset compared with the larger south London sample. 33 There has been evidence of mupirocin resistance in community-acquired strains 47 – 49 and in settings with high community mupirocin usage and MRSA transmission; these may be important factors in driving the spread of MupR strains. We also were not able to consider the impact of readmission and ward transfer in the parameter estimation model.…”

“…An epidemiological description of the full dataset and details of microbiological techniques used has been reported elsewhere. 33 MRSA isolates were submitted to the Centre for Clinical Infection and Diagnostics Research (CIDR) at GSTT. Isolates confirmed as MRSA by culture on chromogenic agar (Oxoid Brilliance) and rapid latex agglutination test (Staphaurex, Remel) were included in the study.…”

“…Isolates in the dataset were screened for mupirocin resistance (low level and high level) using a modified susceptible disc breakpoint method, described in detail by Hughes et al . 33 The ‘susceptible’ breakpoint was later validated by determining MICs with Etest as described. 33 …”

Looking Forward‐Infection Prevention in 2016

“…As with any antimicrobial, development of resistance is a concern. Studies have demonstrated that mupirocin resistance can develop in up to 10% of the staphylococcal isolates in these patient populations over any given period of use 7‐9 . The resistance may be either low or high level, yet either could negatively affect efficacy and put the patient at risk for recolonization with the resistant strain 10 …”