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Infect. Immun., 09 1997, 3672-3679, Vol 65, No. 9
JG Kusters, MM Gerrits, JA Van Strijp and CM Vandenbroucke-Grauls
Helicobacter pylori can transform from its normal helical bacillary
morphology to a coccoid morphology. Since this coccoid form cannot be
cultured in vitro, it has been speculated that it is a dormant form
potentially involved in the transmission of H. pylori and in a patient's
relapse after antibiotic therapy. In this study we determined the effects
of aging, temperature, aerobiosis, starvation, and antibiotics on the
morphologic conversion rate and culturability of H. pylori. Aerobiosis and
the addition of a bactericidal antibiotic to the culture medium resulted in
the highest conversion rate. During the conversion to coccoid forms, the
cultures always lost culturability at the stage where 50% of the organisms
were still in bacillary form; this result indicated that culturability and
coccoid morphology are two separate but related entities. Independent of
the conditions used to induce the conversion into coccoids, the
morphological conversion was accompanied by several marked antigenic and
ultrastructural changes. Also, both the total amounts and the integrity of
RNA and DNA were significantly reduced in coccoid forms. With the
potential-sensitive probe diOC(5)-3, a clear loss of membrane potential in
coccoid forms was observed. Inhibition of protein or RNA synthesis by the
addition of bacteriostatic antibiotics did not prevent the conversion to
coccoid forms but resulted in an increased conversion rate. Hence, we
conclude that conversion of H. pylori from the bacillary to the coccoid
form is a passive process that does not require protein synthesis. Our data
suggest that the coccoid form of H. pylori is the morphologic manifestation
of bacterial cell death.
Copyright © 1997, American Society for Microbiology
Coccoid forms of Helicobacter pylori are the morphologic manifestation of cell death
Department of Medical Microbiology, School of Medicine, Vrije Universiteit, Amsterdam, The Netherlands. JG.Kusters.MM@Med.VU.nl
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