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Antimicrobial Agents and Chemotherapy, August 1998, p. 2074-2083, Vol. 42, No. 8
Service de Bactériologie-Virologie,
Received 3 December 1997/Returned for modification 3 March
1998/Accepted 10 June 1998
The Pseudomonas aeruginosa Mus clinical isolate
produces OXA-18, a pI 5.5 class D extended-spectrum
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Molecular Characterization of OXA-20, a Novel Class
D
-Lactamase, and Its Integron from Pseudomonas
aeruginosa
-lactamase
totally inhibited by clavulanic acid (L. N. Philippon, T. Naas,
A.-T. Bouthors, V. Barakett, and P. Nordmann, Antimicrob. Agents
Chemother. 41:2188-2195, 1997). A second
-lactamase was cloned, and
the recombinant Escherichia coli clone pPL10 expressed a pI
7.4
-lactamase which conferred high levels of amoxicillin and
ticarcillin resistance and which was partially inhibited by clavulanic
acid. The 2.5-kb insert from pPL10 was sequenced, and a 266-amino-acid
protein (OXA-20) was deduced; this protein has low amino acid identity
with most of the class D
-lactamases except OXA-2, OXA-15, and OXA-3
(75% amino acid identity with each). OXA-20 is a restricted-spectrum oxacillinase and is unusually inhibited by clavulanic acid. OXA-20 is a
peculiar
-lactamase because its translation initiates with a TTG
(leucine) codon, which is rarely used as a translational origin in
bacteria. Exploration of the genetic environment of oxa20
revealed the presence of the following integron features: (i) a second
antibiotic resistance gene, aacA4; (ii) an
intI1 gene; and (iii) two 59-base elements, each associated
with either oxa20 or aacA4. This integron is
peculiar because it lacks the 3' conserved region, and therefore is not
a sul1-associated integron like most of them, and because
its 3' end is located within tnpR, a gene involved in the
transposition of Tn5393, a gram-negative transposon.
P. aeruginosa Mus produces two novel and unrelated oxacillinases, OXA-18 and OXA-20, both of which are inhibited by
clavulanic acid.
*
Corresponding author. Mailing address: Service de
Bactériologie-Virologie, Hôpital Antoine
Béclère, 157 rue de-la-Porte de-Trivaux, 92141 Clamart
Cedex, France. Phone: 33-1-45-37-42-98. Fax: 33-1-46-32-67-96. E-mail:
Thierry.Naas{at}kb.u-psud.fr.
Antimicrobial Agents and Chemotherapy, August 1998, p. 2074-2083, Vol. 42, No. 8
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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