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Antimicrobial Agents and Chemotherapy, September 2000, p. 2382-2388, Vol. 44, No. 9
Hospital Infections Program, National Center
for Infectious Diseases, Centers for Disease Control and Prevention,
Atlanta, Georgia 303331; The R. W. Johnson Pharmaceutical Research Institute, Raritan, New Jersey
088692; Área de
Microbiología, Departamento de Biología, Universidad de
las Islas Baleares, Palma de Mallorca,
Spain3; Microbiology Laboratory,
Massachusetts General Hospital, Boston, Massachusetts
021144; Edith Nourse Rogers Memorial
Veterans Hospital, Bedford, Massachusetts
017305; and Lahey Clinic, Burlington,
Massachusetts 018056
Received 24 August 1999/Returned for modification 13 December
1999/Accepted 30 May 2000
Klebsiella pneumoniae K6 (ATCC 700603), a clinical
isolate, is resistant to ceftazidime and other oxyimino-
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Characterization of the Extended-Spectrum
-Lactamase Reference Strain, Klebsiella pneumoniae K6
(ATCC 700603), Which Produces the Novel Enzyme SHV-18
-lactams. A
consistent reduction in the MICs of oxyimino-
-lactams by at least 3 twofold dilutions in the presence of clavulanic acid confirmed the
utility of K. pneumoniae K6 as a quality control strain for
extended-spectrum
-lactamase (ESBL) detection. Isoelectric-focusing
analysis of crude lysates of K6 demonstrated a single
-lactamase
with a pI of 7.8 and a substrate profile showing preferential
hydrolysis of cefotaxime compared to ceftazidime. PCR analysis of total
bacterial DNA from K6 identified the presence of a
blaSHV gene. K6 contained two large plasmids
with molecular sizes of approximately 160 and 80 kb. Hybridization of
plasmid DNA with a blaSHV-specific probe indicated that a blaSHV gene was encoded on the
80-kb plasmid, which was shown to transfer resistance to ceftazidime in
conjugal mating experiments with Escherichia coli HB101.
DNA sequencing of this blaSHV-related gene
revealed that it differs from blaSHV-1 at nine
nucleotides, five of which resulted in amino acid substitutions: Ile to
Phe at position 8, Arg to Ser at position 43, Gly to Ala at position
238, and Glu to Lys at position 240. In addition to the production of
this novel ESBL, designated SHV-18, analysis of the outer membrane
proteins of K6 revealed the loss of the OmpK35 and OmpK37 porins.
*
Corresponding author. Mailing address: Nosocomial
Pathogens Laboratory Branch (G08), Centers for Disease Control and
Prevention, 1600 Clifton Rd. N.E., Atlanta, GA 30333. Phone: (404)
639-3247. Fax: (404) 639-1381. E-mail: Jkr1{at}cdc.gov.
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