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
Science IndicatorsSM from
Scientific, Professor Ito’s work is in
the top 1% in the fields of Clinical Medicine and
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 ScienceWatch.com about her
Please tell us a little about your research and
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: 4289-94, November 2002). Would you talk a
little bit about this study and its significance to the
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
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: 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
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
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
Department of Bacteriology
School of Medicine
Ito's most-cited paper with 534 cites
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
See also a
Fast Breaking Paper comment by
Professor Teruyo Ito from October 2005.