Competition of Various β-Lactam Antibiotics for the Major Penicillin-Binding Proteins of Helicobacter pylori : Antibacterial Activity and Effects on Bacterial Morphology

Abstract

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 β-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 β-lactams significantly bound two or more PBPs, aztreonam specifically targeted PBP63. The influence of sub-MICs of these β-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 β-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 β-lactams for the PBPs in the helical forms and their effects on bacterial morphology.

Antibacterial activity of highly negative charged polyoxotungstates, K27[KAs4W40O140] and K18[KSb9W21O86], and Keggin-structural polyoxotungstates against Helicobacter pylori

“…The form of the bacterial cell depends on the polyoxotungstate-concentration. In this respect, the exposure to AMX at concentration of more than MIC induced both the coccoid cells and the membrane blebbing (data not shown), as reported by other investigators [36,37]. On the other hand, no morphological change was seen when exposed to CLR and MTZ at concentration more than MIC (data not shown).…”

Rol de las formas cocoides de Helicobacter pylori en la infección y la recrudescencia

“…Esto demuestra la presencia de importantes factores adicionales e independientes de la resistencia bacteriana que se relacionan con el éxito del uso de este antibiótico 49 , en especial si tomamos en cuenta que no parece posible que las formas cocoides sean sensibles a los antibióticos ␤-lactámicos porque tienen diferentes perfiles de proteínas de unión a penicilina en comparación con las formas bacilares 50 . Es probable, entonces, que no todos los organismos de H. pylori se eliminen completamente luego del tratamiento de erradicación, sino que algunos de ellos pueden transformarse en formas cocoides y volverse resistentes a los fármacos antibacterianos, lo que tal vez contribuya al fracaso del tratamiento y a la recrudescencia 13,34,45 .…”

Analysis of Aztreonam-Inducing Proteome Changes in Nondividing Filamentous Helicobacter pylori

“…DeLoney and Schiller have reported that PBP63 encoded by FtsI in H. pylori has 30.6 % identity with PBP3 of E. coli and b-lactam antibiotic can specifically bind to this protein [4,8]. Thus in this study, we induced the nondividing filamentous model of H. pylori using aztreonam.…”

“…The PBPs are a set of enzymes involved in polymerization and modification of peptidoglycan and they are integral components in the determination and maintenance of cellular morphology [12]. DeLoney and Schiller [4] have reported that Hp1556 encoded by FtsI has 30.6 % identity to PBP3 of E. coli. Our study proved that aztreonam can also induce morphological change in H. pylori.…”

“…During the life span of H. pylori, either in the stomach or cultured in vitro, this bacteria exists in several forms such as rod-like, spiral, U-shaped, and spherical coccoid forms, which are its morphological features [2,3]. Previous studies found that H. pylori changes into filamentous form in a high-salt level medium at an early stationary phase; aztreonam, a b-lactam antibiotic, can also induce pronounced filamentation in H. pylori [2,4].…”