Archive ScienceWatch



Ito Professor Teruyo Ito
From the Special Topic of Methicillin-Resistant Staphylococcus aureus (MRSA)

According to our March 2008 Special Topic on MRSA research in the past decade, the scientist ranking at #3 is Professor Teruyo Ito, with 28 papers cited a total of 2,197 times. In Essential Science IndicatorsSM  from Thomson Scientific, Professor Ito’s work is in the top 1% in the fields of Clinical Medicine and Microbiology.

Professor Ito is an Associate Professor in the Department of Bacteriology at the School of Medicine and in the Department of Infection Control Science at the Graduate School of Medicine, Juntendo University.

In the interview below, Professor Ito talks with about her MRSA-related research.

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

I graduated from the Faculty of Pharmaceutical Science at Tokyo University. Since I wished to work in the field of basic medicine, I started to work as a research associate in the Department of Bacteriology at Juntendo University. Since ex-professor Takeshi Yokota was interested in bacteria that cause gastrointestinal disorders, I studied mainly about enterotoxins produced by enterotoxigenic E. coli and the characterization of antigenic determinants of V. cholerae. Although the research on MRSA had been one of the big projects in our lab, I only started to work on staphylococci once Dr. Keiichi Hiramatsu was inaugurated as professor.

  A great deal of your most-cited papers deal with genetic elements of MRSA—would you say this is an accurate representation of the main focus of your MRSA research?

Yes. I started studying MRSA at the beginning of the 1990s. By that time, the mecA gene was cloned as the key gene that causes methicillin resistance, and it was suggested that the mecA gene might be encoded by some mobile genetic element, since the gene was disseminated among many staphylococcal species.

My first work on the staphylococci was to clarify the characteristics of the genetic element carrying methicillin resistance. For that purpose, we cloned the regions around the mecA gene and determined their nucleotide sequence. It took more than five years to elucidate the structure of the genetic element—now known as staphylococcal cassette chromosome mec (SCCmec)—and characterize it. Furthermore, we identified structurally different SCCmec elements and classified them as types I-V.

  One of your most-cited original papers in our database is the 2002 Journal of Clinical Microbiology article, "Dissemination of new methicillin-resistant Staphylococcus aureus clones in the community," (Okuma K, et al., 40[11]: 4289-94, November 2002). Would you talk a little bit about this study and its significance to the field?

Appearance of community-acquired MRSA (CA-MRSA) has become a great concern, especially after the report of four pediatric deaths in the USA. This study was based on the work of our lab, e.g., identification of types I –IV SCCmec elements and establishment of PCR strategy to identify these types of SCCmec elements. The paper should be regarded as one of the initial papers describing that CA-MRSA strains belonged to different MRSA clones by investigating the types of SCCmec elements and their genotypes using well-defined CA-MRSA strains identified in the USA and Australia.

This study presented a concept that is now well known: that CA-MRSA clones carry mostly types-IV and V SCCmec elements, whereas, healthcare-acquired MRSA (HA-MRSA) clones carry mostly types I-III SCCmec elements. The strain carrying type-V SCCmec element was first identified in this study as a novel element.

  One of your more recent papers deals with the methods used to detect drug susceptibility in S. aureus strains (Tajima Y, et al., "Rapid detection of Staphylococcus aureus strains having reduced susceptibility to vancomycin using a chemoluminescence-based drug-susceptibility test," Journal of Microbiological Methods, September 2007). Would you talk a little about this new method and its advantages over other techniques?

This work was mostly done by Dr. Tajima. This is a chemiluminescence-based technique that measures bacterial metabolic activity. This method is able to discriminate S. aureus strains having reduced susceptibilities to vancomycin from vancomycin-susceptible S. aureus with a sensitivity and specificity of > 95%. This is a rapid and reliable method that appears to be promising for detection of vancomycin-intermediate S. aureus strains.

  Another of your more recent papers deals with the methods use to detect different types of SCCmec elements by multiplex PCR (Kondo Y, et al., "Combination of multiplex PCRs for staphylococcal cassette chromosome mec type assignment: Rapid identification system for mec, ccr, and major differences in junkyard regions," Antimicrobial Agents and Chemotherapy 51[1]: 264-74, January 2007). Would you talk a little about this particular method and its advantages over other techniques?

To examine the types of SCCmec elements became essential for epidemiological studies. Since types of SCCmec elements are defined by the combination of the class of the mec gene complex and the type of ccr gene complex, rapid and convenient methods to identify them are required.

The manuscript reported multiplex PCRs to identify five ccr genes at a reaction (M-PCR1) and three mec gene complexes at a reaction (M-PCR2). While other M-PCRs were mostly based on the identification of J-regions (the region other than mec gene complex and ccr gene complex), I think this is the most appropriate way for determining types of SCCmec elements by PCR.

  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?

In the past decade, genetic analysis of MRSA has advanced very much. Genome sequences of many staphylococcal strains have been reported. Based on those data, many study tools—e.g., microarray—have been developed and the numbers of studies of staphylococcal species has increased. In the epidemiological field, the concept that that MRSA clones should be defined by the combination of SCCmec type and their genotype, e.g., MLST, was established. We now can identify and analyze MRSA clones easily and precisely.

I think that the more our knowledge has increased, the more we see problems that should be considered. The number of isolates of CA-MRSA has increased greatly during the 2000s. Most of the CA-MRSA clones were different from extant MRSA clones disseminated in hospitals. How to cope with CA-MRSA—in other words, how to prevent the appearance of CA-MRSA and how to destroy CA-MRSA—is the important problem. Multiple-drug-resistant S. aureus strains represented by VRSA appeared. Infection control and usage of drugs, including development of novel antibiotics, might be the important problems to be considered.

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

Bacteria are small organisms that cannot be seen by the naked eye. There are many bacteria around us. To control or prevent infection from those organisms, I think it is necessary to know where the bacteria are. If you study bacteria, you will be able to behave as if you can see them and will be able to succeed in controlling infection. As a scientist working at the Department of Infection Control Science, I am very happy if my research will be able to help you to understand the nature of pathogens, especially about MRSA.

Teruyo Ito
Department of Bacteriology
School of Medicine
Juntendo University
Tokyo, Japan

Professor Teruyo Ito's most-cited paper with 534 cites to date:
Kuroda M, et al., “Whole-genome sequencing of meticillin-resistant Staphylococcus aureus,” Lancet 357(9264): 1225-40, 21 April 2001. Source: Essential Science Indicators from Thomson Scientific.
Related Information:
  See also a Fast Breaking Paper comment by Professor Teruyo Ito from October 2005.

Special Topics : Methicillin-Resistant Staphylococcus aureus (MRSA) : Professor Teruyo Ito - Special Topic of MRSA