Journal of Clinical Microbiology, June 2001, p. 2072-2078, Vol. 39, No. 6
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.6.2072-2078.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
-Lactam Resistance
Laboratoire de Microbiologie, Faculté de Pharmacie, Université de Bordeaux 2, Bordeaux,1 and Laboratoire de Microbiologie et Service de Réanimation, Hôpital de Pau, Pau,2 France
Received 4 December 2000/Returned for modification 8 January 2001/Accepted 20 March 2001
Over a 3-year period, 67 patients of the Hospital of Pau (Pau,
France), including 64 patients hospitalized in the adult intensive care
unit (ICU), were colonized and/or infected by strains of Pseudomonas aeruginosa P12, resistant to all potentially
active antibiotics except colistin. Most patients were mechanically
ventilated and presented respiratory tract infections. Since cefepime
and amikacin were the least inactive antibiotics by MIC determination, all ICU patients were treated with this combination, and most of them
benefited. Cefepime-amikacin was found highly synergistic in vitro.
Ribotyping and arbitrary primer-PCR analysis confirmed the presence of
a single clonal isolate. Isoelectrofocusing revealed that the epidemic
strain produced large amounts of the chromosomal cephalosporinase and
an additional enzyme with a pI of 5.7, corresponding to PSE-1, as
demonstrated by PCR and sequencing. Outer membrane protein profiles on
sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed the
absence of a ca. 46-kDa protein, likely to be OprD, and increased
production of two ca. 49- and 50-kDa proteins, consistent with the
outer membrane components of the efflux systems, MexAB-OprM and
MexEF-OprN. Thus, we report here a nosocomial outbreak due to
multiresistant P. aeruginosa P12 exhibiting at least four
mechanisms of
-lactam resistance, i.e., production of the
penicillinase PSE-1, overproduction of the chromosomal cephalosporinase, loss of OprD, and overexpression of efflux systems, associated with a better activity of cefepime than ceftazidime.
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