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Enright Prof. Mark Enright
From the Special Topic of Methicillin-Resistant Staphylococcus aureus (MRSA)

According to our March 2008 Special Topic on MRSA research over the past decade, the work of Professor Mark Enright ranks at #6, with 32 papers cited a total of 1,787 times. Two of these papers are featured in the list of the top 20 papers from the past decade.

Prof. Enright is part of the Faculty of Medicine at Imperial College London, where he is Professor and Chair of Molecular Epidemiology in the Division of Epidemiology, Public Health, and Primary Care.

In Essential Science IndicatorsSM from Clarivate Analytics, Prof. Enright's citation record includes 50 papers cited a total of 3,316 times between January 1, 1997 and December 31, 2007. These papers include 23 papers cited a total of 1,586 times in the field of Clinical Medicine and 20 papers cited a total of 1,428 times in the field of Microbiology.

In the interview below, he talks with about his work with MRSA.

  Please tell us a little about your research and educational background.

My Ph.D. research at the Medical School of Aberdeen University in Scotland was in Medical Microbiology, which, along with a Bachelor's degree in Biological Sciences (Stirling University) and a Master's in Biochemistry (Dundee University), gave me a good appreciation of the diseases that bacteria can cause but also an insight into how they do it. My postdoctoral research with Professor Brian Spratt at Sussex and Oxford Universities gave me the chance to examine how the mechanisms by which bacteria evolve, mutate, and exchange DNA with other strains of bacteria, impact on human health in terms of increased resistance to antibiotics and heightened virulence.

"We know much more about the global dissemination of particular types of MRSA than we used to 10 years ago following the development of MLST, and important strains can now rapidly be identified as such and tracked to help minimize their spread."

At this time Professor Spratt and I were beginning to trace the genetic history of bacterial pathogens using multiple DNA sequences [1] and in early work we demonstrated the power of this approach with the respiratory pathogen Streptococcus pneumoniae This work formed the basis for the technique called multilocus sequence typing—MLST [2, 3]—which is now commonly used for characterizing and tracking the spread of many human bacterial pathogens.

  What interested you in studying MRSA?

At the end of the last decade methicillin-resistant Staphylococcus aureus (MRSA) had become a major problem in hospitals worldwide and things were (and still are) particularly bad in the UK. In 1999 two clinical colleagues in Oxford, Dr. Nick Day and Dr. Sharon Peacock approached Professor Spratt and myself with a view to developing MLST for a study of serious S. aureus disease in Oxford, and although I was working on several other projects on different organisms, I figured I could fit in one more study as it was on such a significant cause of disease.

  Your most-cited original paper in our database is the 2000 Journal of Clinical Microbiology article, "Multilocus sequence typing for characterization of methicillin-resistant and methicillin-susceptible clones of Staphylococcus aureus." Would you talk a little bit about this study and its significance to the field?

Prior to our development of an MLST scheme for S. aureus it was difficult to compare the strains of bacteria that cause disease to those in other hospitals, or to those that live harmlessly in the nose of approximately a third of the human population, or to the first MRSA strains from the 1960s. MLST uses DNA sequencing of parts of seven genes in the bacterial chromosome and these sequences allow us to give each sample of bacteria a "sequence type" (ST) based on these sequences that is defined as the combination of alleles at each of the seven genes. For example ST1 S. aureus have allele 1 at all seven genes—written thus 1-1-1-1-1-1-1. ST22 isolates, the major cause of MRSA disease in the UK, have the profile 7-6-1-5-8-8-6.

These data and information on the patient and other information on the strain, such as antibiotic resistance profile, are stored in a database that can be added to and interrogated at This website holds similar databases for many bacterial pathogens of humans and animals and is a rich resource for researchers and clinicians.

  Several of your papers deal with the evolutionary history of MRSA—would you talk about this aspect of your work?

S. aureus replicates by binary fission so that each bacterial cell gives rise to two near-identical copies. Using MLST we can compare the genetic identity of isolates separated by decades of evolution—a huge number of generations given the fact that the generation time can be a matter of minutes in this species. To more precisely define how the first MRSA compare to modern strains, we used MLST and analysis of the mobile genetic element conferring methicillin resistance in a large international collection of MRSA and MSSA (methicillin-sensitive S. aureus). We found that hospital MRSA evolved within only five lineages of the species, and we pieced together the genetic events that led to the first MRSA strain back in 1961 following the acquisition of methicillin resistance by an epidemic MSSA strain common in the 1950s[4].

MRSA are now commonly found outside of hospitals in many countries. These community-MRSA commonly cause infections in children and young adults and they usually produce a toxin called PVL that is uncommon in hospital strains. In work with Vandenesch and colleagues [5] we showed the genetic distinction between hospital- and community-acquired lineages of MRSA, and in a later study [6] showed how once successful MSSA strains carrying genes for the PVL toxin have returned as community-acquired MRSA following a "rearming" with resistance to many antibiotics.

  How has our knowledge of MRSA advanced in the past decade? How much more do you expect we will learn in the next 10 years?

"Using MLST we can compare the genetic identity of isolates separated by decades of evolution..."

We know much more about the global dissemination of particular types of MRSA than we used to 10 years ago following the development of MLST, and important strains can now rapidly be identified as such and tracked to help minimize their spread. However, other important advances, such as the complete sequencing of the genomes of several MRSA strains and advances in microarray technology, have revealed the genetic flexibility of the organism with redundancy in many areas such as binding to host tissues, host evasion and toxin production.

  What would you like to tell the general public about your research?

My research is geared towards understanding how organisms such as MRSA evolve to become aggressive pathogens while developing resistance to human interventions such as antibiotic resistance and host immunity. Only by understanding the biology of such threats can we counter their threat to human health with the aid of better diagnostics and therapies.


[1] Coffey TJ, Enright MC, Daniels M, Wilkinson P, Berron S, Fenoll A, et al., "Serotype 19A variants of the Spanish serotype 23F multiresistant clone of Streptococcus pneumoniae," Microb. Drug Resist.4(1):51-5, Spring 1998.

[2] Enright MC, Spratt BG, "A multilocus sequence typing scheme for Streptococcus pneumoniae: identification of clones associated with serious invasive disease," Microbiology 144 (Pt 11): 3049-60, November 1998.

[3] Enright MC, Spratt BG, "Multilocus sequence typing," Trends Microbiol. 7(12): 482-7, December 1999.

[4] Enright MC, Robinson DA, Randle G, Feil EJ, Grundmann H, Spratt BG, "The evolutionary history of methicillin-resistant Staphylococcus aureus (MRSA)," Proc. Natl. Acad. Sci. USA. 99(11): 7687-92, 28 May 2002.

[5] Vandenesch F, Naimi T, Enright MC, Lina G, Nimmo GR, Heffernan H, et al., "Community-acquired methicillin-resistant Staphylococcus aureus carrying Panton-Valentine leukocidin genes: worldwide emergence," Emerg. Infect. Dis. 9(8): 978-84, August 2003.

[6] Robinson DA, Kearns AM, Holmes A, Morrison D, Grundmann H, Edwards G, et al., "Re-emergence of early pandemic Staphylococcus aureus as a community-acquired meticillin-resistant clone," Lancet 365(9466): 1256-8, 2-8 April 2005.

Prof. Mark C. Enright
Division of Epidemiology, Public Health, and Primary Care
Faculty of Medicine
Imperial College London
London, UK

Prof. Mark Enright's most-cited paper with 387 cites to date:
Enright MC, et al., "Multilocus sequence typing for characterization of methicillin-resistant and methicillin-susceptible clones of Staphylococcus aureus," J. Clin. Microbiol. 38(3): 1008-15, March 2000. Source: Essential Science Indicators from Clarivate Analytics.

Keywords: MRSA, methicillin-sensitive Staphylococcus aureus, multilocus sequence typing (MLST), genetic identity.


Special Topics : Methicillin-Resistant Staphylococcus aureus (MRSA) : Prof. Mark Enright - Special Topic of MRSA