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Antimicrobial Agents and Chemotherapy, November 1999, p. 2702-2709, Vol. 43, No. 11
Division of Biomedical Sciences, University
of California, Riverside, Riverside, California 92521
Received 15 January 1999/Returned for modification 3 May
1999/Accepted 31 August 1999
The penicillin-binding proteins (PBPs) of helical (log-phase)
Helicobacter pylori ATCC 43579 were identified by using
biotinylated ampicillin. The major PBPs had apparent molecular masses
of 47, 60, 63, and 66 kDa; an additional minor PBP of 95 to 100 kDa was also detected. The relative affinities of various
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Competition of Various
-Lactam Antibiotics for
the Major Penicillin-Binding Proteins of Helicobacter
pylori: Antibacterial Activity and Effects on Bacterial
Morphology
-lactams for these
PBPs were tested by competitive-binding assays. Only PBP63 appeared to
be significantly bound to each of the competing antibiotics, whereas
PBP66 strongly bound mezlocillin, oxacillin, amoxicillin, and
ceftriaxone. Whereas most of the
-lactams significantly bound two or
more PBPs, aztreonam specifically targeted PBP63. The influence of
sub-MICs of these
-lactams on the morphologies of log-phase H. pylori was observed at both the phase-contrast and transmission electron microscopy levels. Each of the eight
-lactams examined induced blebbing and sphere formation, whereas aztreonam was the only
antibiotic studied which induced pronounced filamentation in H. pylori. Finally, studies comparing the PBPs of helical
(log-phase) cultures with those of coccoid (7-, 14-, and 21-day-old)
cultures of H. pylori revealed that the major PBPs at 60 and 63 kDa seen in the helical form were almost undetectable in the
coccoid forms, whereas PBP66 remained the major PBP in the coccoid
forms, although somewhat reduced in level compared to the helical form.
PBP47 was present in both forms at approximately equal concentrations. These studies thus identified the major PBPs in both helical and coccoid forms of H. pylori and compared the relative
affinities of seven different
-lactams for the PBPs in the helical
forms and their effects on bacterial morphology.
*
Corresponding author. Mailing address: Division of
Biomedical Sciences, University of California, Riverside, Riverside, CA 92521. Phone: (909) 787-4569. Fax: (909) 787-5504. E-mail:
neal.schiller{at}ucr.edu.
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