Monic acid A: a biomarker in clinical intra-nasal mupirocin medication for MRSA decolonisation

Abstract

Context: Mupirocin (Bactroban^R) is widely prescribed for intra-nasal decolonisation of MRSA for in-patients awaiting surgery or self-medicated for out-patients although adherence for the latter is not monitored. Non-adherence is a widespread pharmaceutical problem but could encourage selection of antibiotic resistance. Mupirocin is only a topical antibiotic because it decomposes in stomach acidity to monic acid A, but this has not previously been exploited as a biomarker for clinical intra-nasal medication.

Materials and methods: Urine from three catheterised patients in two London hospitals during and after mupirocin medication, was passed through Waters Oasis cartridges to isolate organic acids. Sensitive LC-MS-MS analysis for monic acid A in methanolic eluate has been developed to identify ∼10 pg.

Results: Monic acid A was quantified in all samples from one patient, translating into 6–46 ng from 12 mg mupirocin, assuming 1 L daily urine output. However, no urinary monic acid A was detected for two other patients.

Discussion and conclusions: Consistent occurrence of monic acid A in urine of one mupirocin patient shows for the first time that antibiotic distribution across nasal mucous membranes had generally been maintained during medication. In contrast, consistent absence in the two other patients requires wider study in hospital.

Keywords:

• Mupirocin
• Bactroban
• pseudomonic acid A
• biomarker
• monic acid A
• MRSA decolonisation
• antibiotic resistance
• LC-MS-MS

Acknowledgments

Urines were obtained under Provision of Tissue Samples by the Imperial College Healthcare NHS Trust Tissue Bank funded by the National Institute for Health Research (NIHR) Biomedical Research Centre based at Imperial College Healthcare NHS Trust and Imperial College London. The Research Tissue Bank is approved by the REC3 of Wales (REC approval reference number 17/WA/0161). Gift of Oasis HLB cartridges from Waters UK, Elstree is acknowledged, as also is exceptional cooperation from hospital clinical staff.

Disclosure statement

No potential conflict of interest was reported by the authors.