Subpopulations of stressed yersinia pseudotuberculosis preferentially survive doxycycline treatment within host tissues

Jasmine Ramirez Raneses, Alysha L. Ellison, Bessie Liu, Kimberly M. Davis

Research output: Contribution to journalArticle

Abstract

Severe systemic bacterial infections result in colonization of deep tis-sues, which can be very difficult to eliminate with antibiotics. It remains unclear if this is because antibiotics are not reaching inhibitory concentrations within tissues, if subsets of bacteria are less susceptible to antibiotics, or if both contribute to limited treatment efficacy. To detect exposure to doxycycline (Dox) present in deep tissues following treatment, we generated a fluorescent transcriptional reporter derived from the tet operon to specifically detect intracellular tetracycline exposure at the single bacterial cell level. Dox exposure was detected in the spleen 2 h after intraperitoneal injec-tion, and by 4 h postinjection, this treatment resulted in a significant decrease in viable Yersinia pseudotuberculosis bacteria in the spleen. Nitric oxide-stressed bacteria preferentially survived treatment, suggesting that stress was sufficient to alter Dox susceptibility. Many bacteria (~10%) survived a single dose of Dox, and the antibiotic accumulated at the periphery of microcolonies to growth in-hibitory concentrations until 48 h posttreatment. After this time point, antibiotic concentrations decreased and bacterial growth resumed. Dox-treated mice even-tually succumbed to the infection, albeit with significantly prolonged survival rel-ative to that of untreated mice. These results indicate that Dox delivery by intra-peritoneal injection results in rapid diffusion of inhibitory concentrations of antibiotic into the spleen, but stressed cells preferentially survive drug treat-ment, and bacterial growth resumes once drug concentrations decrease. This flu-orescent reporter strategy for antibiotic detection could easily be modified to detect the concentration of additional antimicrobial compounds within host tissues following drug administration. IMPORTANCE Bacterial infections are very difficult to treat when bacteria spread into the bloodstream and begin to replicate within deep tissues, such as the spleen. Subsets of bacteria can survive antibiotic treatment, but it remains unclear if this survival is because of limited drug diffusion into tissues, or if there are changes within the bacteria, promoting survival of some bacterial cells. Here, we have devel-oped a fluorescent reporter to detect doxycycline (Dox) diffusion into host tissues, and we show that Dox impacts the bacterial population within hours of administration and inhibits bacterial growth for 48 h. However, bacterial growth resumes when antibiotic concentrations decrease. Subsets of bacteria, stressed by the host response to infection, survive Dox treatment at a higher rate. These results provide critical information about the dynamics that occur within deep tissues following antibiotic administration and suggest that subsets of bacteria are predisposed to survive inhibitory concentrations of antibiotic before exposure.

Original languageEnglish (US)
Article numbere00901-20
Pages (from-to)1-14
Number of pages14
JournalmBio
Volume11
Issue number4
DOIs
StatePublished - Jul 1 2020

Keywords

  • Antibiotic diffusion
  • Doxycycline
  • Fluorescent reporter
  • Systemic infection
  • Tetracycline derivatives
  • Yersinia

ASJC Scopus subject areas

  • Microbiology
  • Virology

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