SME-type carbapenem-hydrolyzing class A beta-lactamases from geographically diverse Serratia marcescens strains.
Three sets of carbapenem-resistant Serratia marcescens isolates have been identified in the United States: 1 isolate in Minnesota in 1985 (before approval of carbapenems for clinical use), 5 isolates in Los Angeles (University of California at Los Angeles [UCLA]) in 1992, and 19 isolates in Boston from 1994 to 1999. All isolates tested produced two beta-lactamases, an AmpC-type enzyme with pI values of 8.6 to 9.0 and one with a pI value of approximately 9.5. The enzyme with the higher pI in each strain hydrolyzed carbapenems and was not inhibited by EDTA, similar to the chromosomal class A SME-1 beta-lactamase isolated from the 1982 London strain S. marcescens S6. The genes encoding the carbapenem-hydrolyzing enzymes were cloned in Escherichia coli and sequenced. The enzyme from the Minnesota isolate had an amino acid sequence identical to that of SME-1. The isolates from Boston and UCLA produced SME-2, an enzyme with a single amino acid change relative to SME-1, a substitution from valine to glutamine at position 207. Purified SME enzymes from the U. S. isolates had beta-lactam hydrolysis profiles similar to that of the London SME-1 enzyme. Pulsed-field gel electrophoresis analysis revealed that the isolates showed some similarity but differed by at least three genetic events. In conclusion, a family of rare class A carbapenem-hydrolyzing beta-lactamases first described in London has now been identified in S. marcescens isolates across the United States.
Queenan
A M
AM
The R. W. Johnson Pharmaceutical Research Institute, Raritan, New Jersey 08869, USA. aqueenan@prius.jnj.com
Torres-Viera
C
C
Gold
H S
HS
Carmeli
Y
Y
Eliopoulos
G M
GM
Moellering
R C
RC
Quinn
J P
JP
Hindler
J
J
Medeiros
A A
AA
Bush
K
K
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015780:Carbapenems / Q000378:metabolism*; D006868:Hydrolysis; D008826:Microbial Sensitivity Tests; D017421:Sequence Analysis; D012706:Serratia marcescens / Q000145:classification / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D006113:United Kingdom; D014481:United States; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D015780:Carbapenems; C094219:beta-lactamase Sme-1; D001618:beta-Lactamases