Yoshichika Arakawa

In the 1980s, I found that the chromosomal β‐lactamase of Klebsiella pneumoniae

LEN‐1 showed a very high similarity to the R‐plasmid‐mediated penicillinase

TEM‐1 on the amino acid sequence level, and this strongly suggested the origination

of TEM‐1 from the chromosomal penicillinases of K. pneumoniae or related

bacteria. Moreover, the chromosomal K1 β‐lactamase (KOXY) of Klebsiella oxytoca

was found to belong to the class A β‐lactamases that include LEN‐1 and TEM‐1,

although KOXY can hydrolyze cefoperazone (CPZ) like the chromosomal AmpC type

cephalosporinases of various Enterobacteriaceae that can hydrolyze several

cephalosporins including CPZ. Furthermore, my collaborators and I found plural

novel serine‐type β‐lactamases, such as MOX‐1, SHV‐24, TEM‐91, CTX‐M‐64,

CMY‐9, CMY‐19, GES‐3, GES‐4, and TLA‐3, mediated by plasmids. Besides these

serine‐type β‐lactamases, we also first identified exogenously acquired metallo‐

β‐lactamases (MBLs), IMP‐1 and SMB‐1, in imipenem‐resistant Serratia marcescens,

and the IMP‐1‐producing S. marcescens TN9106 became the index case for

carbapenemase‐producing Enterobacteriaceae. I developed the sodium mercaptoacetic

acid (SMA)‐disk test for the simple identification of MBL‐producing

bacteria. We were also the first to identify a variety of plasmid‐mediated 16S

ribosomal RNA methyltransferases, RmtA, RmtB, RmtC, and NpmA, from various

Gram‐negative bacteria that showed very high levels of resistance to a wide

range of aminoglycosides. Furthermore, we first found plasmid‐mediated quinolone

efflux pump (QepA) and fosfomycin‐inactivating enzymes (FosA3 and FosK).

We also first characterized penicillin reduced susceptible Streptococcus agalactiae (PRGBS),

macrolide‐resistant Mycoplasma pneumoniae, as well as Campylobacter jejuni, and

Helicobacter pylori, together with carbapenem‐resistant Haemophilus influenzae.