Dataset Information

Biofilms facilitate cheating and social exploitation of ?-lactam resistance in Escherichia coli.

ABSTRACT: Gram-negative bacteria such as Escherichia coli commonly resist ?-lactam antibiotics using plasmid-encoded ?-lactamase enzymes. Bacterial strains that express ?-lactamases have been found to detoxify liquid cultures and thus to protect genetically susceptible strains, constituting a clear laboratory example of social protection. These results are not necessarily general; on solid media, for instance, the rapid bactericidal action of ?-lactams largely prevents social protection. Here, we tested the hypothesis that the greater tolerance of biofilm bacteria for ?-lactams would facilitate social interactions. We used a recently isolated E. coli strain, capable of strong biofilm formation, to compare how cooperation and exploitation in colony biofilms and broth culture drives the dynamics of a non-conjugative plasmid encoding a clinically important ?-lactamase. Susceptible cells in biofilms were tolerant of ampicillin-high doses and several days of exposure were required to kill them. In support of our hypothesis, we found robust social protection of susceptible E. coli in biofilms, despite fine-scale physical separation of resistant and susceptible cells and lower rates of production of extracellular ?-lactamase. In contrast, social interactions in broth were restricted to a relatively narrow range of ampicillin doses. Our results show that ?-lactam selection pressure on Gram-negative biofilms leads to cooperative resistance characterized by a low equilibrium frequency of resistance plasmids, sufficient to protect all cells.

SUBMITTER: Amanatidou E

PROVIDER: S-EPMC6884583 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Biofilms facilitate cheating and social exploitation of β-lactam resistance in <i>Escherichia coli</i>.

Amanatidou Elli E Matthews Andrew C AC Kuhlicke Ute U Neu Thomas R TR McEvoy James P JP Raymond Ben B

NPJ biofilms and microbiomes 20191129 1

Gram-negative bacteria such as <i>Escherichia coli</i> commonly resist β-lactam antibiotics using plasmid-encoded β-lactamase enzymes. Bacterial strains that express β-lactamases have been found to detoxify liquid cultures and thus to protect genetically susceptible strains, constituting a clear laboratory example of social protection. These results are not necessarily general; on solid media, for instance, the rapid bactericidal action of β-lactams largely prevents social protection. Here, we t ...[more]

PMID: 31814991

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Project description:Cell wall deficient bacterial L-forms are induced by exposure to cell wall-targeting antibiotics and immune effectors such as lysozyme. L-forms of different bacteria (including Escherichia coli) have been reported in human infections, but whether this is a normal adaptive strategy or simply an artifact of antibiotic treatment in certain bacterial species remains unclear. Here we show that members of a representative, diverse set of pathogenic E. coli readily proliferate as L-forms in supratherapeutic concentrations of the broad-spectrum antibiotic meropenem. We report that they are completely resistant to antibiotics targeting any penicillin-binding proteins in this state, including PBP1A/1B, PBP2, PBP3, PBP4, and PBP5/6. Importantly, we observed that reversion to the cell-walled state occurs efficiently, less than 20 h after antibiotic cessation, with few or no changes in DNA sequence. We defined for the first time a logarithmic L-form growth phase with a doubling time of 80 to 190 min, followed by a stationary phase in late cultures. We further demonstrated that L-forms are metabolically active and remain normally susceptible to antibiotics that affect DNA torsion and ribosomal function. Our findings provide insights into the biology of L-forms and help us understand the risk of β-lactam failure in persistent infections in which L-forms may be common. IMPORTANCE Bacterial L-forms require specialized culture techniques and are neither widely reported nor well understood in human infections. To date, most of the studies have been conducted on Gram-positive and stable L-form bacteria, which usually require mutagenesis or long-term passages for their generation. Here, using an adapted osmoprotective growth media, we provide evidence that pathogenic E. coli can efficiently switch to L-forms and back to a cell-walled state, proliferating aerobically in supratherapeutic concentrations of antibiotics targeting cell walls with few or no changes in their DNA sequences. Our work demonstrates that L-form switching is an effective adaptive strategy in stressful environments and can be expected to limit the efficacy of β-lactam for many important infections.

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Dataset Information

Biofilms facilitate cheating and social exploitation of ?-lactam resistance in Escherichia coli.

Publications

Biofilms facilitate cheating and social exploitation of β-lactam resistance in <i>Escherichia coli</i>.

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