Researchers at the University of Melbourne uncovered three multidrug-resistant lineages of Staphylococcus epidermidis that have evolved within the hospital environment and spread globally.

The Gram-positive, catalase-negative, and coagulase-negative S. epidermidis is part of the human skin and mucosal flora – accounting for 60–70% of all coagulase-negative Staphylococci on the skin and present in 93% of nares samples.^1,2 However, the emergence of S. epidermidis as one of the major nosocomial pathogens has been on the rise due to invasive medical procedures; S. epidermidis accounts for the leading cause of surgical site infections, foreign body-related infections, and bloodstream infections.^3,4

Initial genomic studies of multidrug-resistant S. epidermidis (MDRSE) isolates from Austin Health (an 800-bed tertiary hospital in Melbourne, Australia) revealed three variants – two ST2 and one ST23 –endemic within the institution, resulting in repeated nosocomial infections in the recent decade.⁴ A further investigation to determine the broader distribution of these three MDRSE lineages uncovered the previously unrecognised global spread of this pathogen across Australia and at least 10 other countries.⁴

These three genetically distinct MDRSE lineages were found to have common dual D471E and I527M RpoB substitutions – generating rifampicin resistance and vancomycin heteroresistance in S. epidermidis that are undetectable by standard diagnostic methods.⁴ These near pan-drug resistant lineages were demonstrated to be endemic within multiple institutions globally, suggesting their unrecognised presence in other institutions – thus the urgency for further research into the clinical impact of these lineages and clinical data on treatment outcomes.⁴

This study suggests that co-prescription of vancomycin and rifampicin may have promoted the generation of resistance to both agents, although additional investigations are required for clinical recommendations.⁴ The high use of antibiotics in intensive care units are also thought to have cause the spread of MDRSE.⁵ This study emphasises the exhausting pool of antibiotics available for treatment caused by these MDRSE isolates and the importance of appropriate use of remaining antibiotics options.

The researchers concluded that the current findings indicate the need to review clinical guidelines to avoid further generation of near untreatable pathogens.

References

1. John JF, et al. Staphylococcus epidermidis and other coagulase-negative staphylococci. Available at: http://www.antimicrobe.org/b234.asp. Accessed October 2018.
2. Human Microbiome Project Consortium. Nature 2012;486:207-214.
3. Becker K, et al. Clin Microbiol Rev 2014;27:870-926.
4. Lee JYH, et al. Nat Microbiol 2018;3:1175-1185.
5. The Straits Times. Drug-resistant superbug spreading in hospitals: Study. Available at: https://www.straitstimes.com/world/europe/drug-resistant-superbug-spreading-in-hospitals-study. Accessed October 2018.