Genomics reveals global emergence of near pan-drug resistant S. epidermidis

Dr Jean Lee1

1Monash Health, Victoria, Australia


Staphylococcus epidermidis is an important member of the human microbiome, widely present on healthy skin, and is a well-recognised cause of hospital-associated device related infections. We noted an increase in multi-drug resistant S. epidermidis infections at our institution, and undertook a combined genomic-phenotypic analysis of a global collection of drug-resistant isolates. Using genomics we reveal that three multidrug resistant, hospital-adapted lineages of S. epidermidis (two ST2 and one ST23) have emerged in recent decades and spread globally. Resistant to multiple classes of antibiotics (beta-lactams, aminoglycosides, quinolones, macrolides, and fusidanes), these multidrug resistant clades are also resistant to rifampicin through acquisition of a specific rpoB mutation that has become fixed in these populations. Analysis of 419 isolates collected from 96 institutions in 24 countries identified a dual RpoB substitution (D471E/I527M) to be the most common cause of rifampicin resistance in S. epidermidis, accounting for 86.6% of mutations.

Furthermore, we reveal that the D471E/I527M dual substitution occurs almost exclusively in isolates from the ST2 and ST23 lineages. By breaching lineage-specific DNA restriction modification barriers and then performing site-directed mutagenesis, we show that this rpoB mutation not only confers rifampicin resistance, but also reduced susceptibility to the last-line glycopeptide antibiotics, vancomycin and teicoplainin. Our study has uncovered the previously unrecognised international spread of a near pan-drug resistant opportunistic pathogen. It is possible that hospital practices, such as antibiotic monotherapy utilising rifampicin-impregnated medical devices, have driven the evolution of this organism, towards potentially incurable infections.

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The ACIPC is the peak body for Infection Prevention and Control professionals in the Australasian region. Our stated vision is the prevention and control of infection in our communities. We commenced in January 2012 bringing together the various State and Territory infection control associations formerly in AICA (The Australian Infection Control Association) to support and encourage collaboration across Australasia.

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