The progress of type II persisters of Escherichia coli O157:H7 to a non-culturable state during prolonged exposure to antibiotic stress with revival being aided through acid-shock treatment and provision of methyl pyruvate.

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From: Canadian Journal of Microbiology(Vol. 67, Issue 7)
Publisher: NRC Research Press
Document Type: Article
Length: 7,138 words
Lexile Measure: 1400L

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Abstract :

Persisters are a form of dormancy in bacteria that provide temporary resistance to antibiotics. The following reports on the formation of Escherichia coli O157:H7 E318 type II persisters from a protracted (8 days) challenge with ampicillin. Escherichia coli O157:H7 followed a multiphasic die-off pattern with an initial rapid decline (Phase I) of susceptible cells that transitioned to a slower rate representing tolerant cells (Phase II). After 24 h post-antibiotic challenge, the E. coli O157:H7 levels remained relatively constant at 2 log CFU/mL (Phase III), but became non-culturable within 8-days (Phase IV). The revival of persisters in Phase III could be achieved by the removal of antibiotic stress, although those in Phase IV required an extended incubation period or application of acid-shock. The carbon utilization profile of persister cells was less diverse compared with non-persisters, with only methyl pyruvate being utilized from the range tested. Inclusion of methyl pyruvate in tryptic soy agar revived non-cultural persisters, presumably by stimulating metabolism. The results suggest that persisters could be subdivided into culturable or non-culturable cells, with the former representing a transition state to the latter. The study provided insights into how to revive cells from dormancy to aid enumeration and control. Key words: persisters, ampicillin, antibiotic resistance, Escherichia coli O157H7, methyl pyruvate ester, acid shock. Les persisters sont associes a une forme de dormance chez les bacteries qui confere une resistance temporaire aux antibiotiques. Cet article rapporte la formation de persisters d'Escherichia coli O157:H7 E318 Type II a la suite d'une provocation prolongee (8 jours) a l'ampicilline. E. coli O157:H7 suivait un schema de mort multiphasique avec un declin initial rapide (phase I) des cellules sensibles qui passait a un taux plus lent representant les cellules tolerantes (phase II). Apres 24 h post-provocation antibiotique, les niveaux d'E. coli O157:H7 demeuraient relativement constants a 2 log UFC/mL (phase III), mais devenaient non cultivables en moins de 8 jours (phase IV). Le retablissement des souches de persisters en phase III pouvait etre obtenu par le retrait du stress antibiotique, bien que celles de la phase IV aient necessite une periode d'incubation prolongee ou l'application d'un choc acide. Le profil d'utilisation du carbone des persisters etait moins diversifie que celui des non-persisters, seul le pyruvate de methyle etant utilise dans la gamme testee. L'inclusion de pyruvate de methyle a la gelose trypticase soja permettait de raviver les persisters non cultivables, probablement en stimulant leur metabolisme. Les resultats suggerent que les persisters pourraient etre subdivises en cellules cultivables ou non cultivables, les premieres representant un etat de transition vers les secondes. L'etude a fourni des indications sur la facon de raviver les cellules en dormance pour faciliter la numeration et le controle. [Traduit par la Redaction] Mots-cles : persisters, ampicilline, resistance aux antibiotiques, Escherichia coli O157H7, ester de pyruvate de methyle, choc acide.

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Gale Document Number: GALE|A668735842