Antibiofilm agents with therapeutic potential against enteroaggregative Escherichia coli
Abstract
Background
Enteroaggregative Escherichia coli (EAEC) is a predominant but neglected enteric pathogen implicated in infantile diarrhoea and nutrient malabsorption. There are no non-antibiotic approaches to dealing with persistent infection by these exceptional colonizers, which form copious biofilms. We screened the Medicines for Malaria Venture Pathogen Box for chemical entities that inhibit EAEC biofilm formation.
Methodology
We used two EAEC strains, 042 and MND005E, in a medium-throughput crystal violet-based antibiofilm screen. Hits were confirmed in concentration-dependence, growth kinetic and time course assays and activity spectra were determined against a panel of genome-sequenced EAEC. Antibiofilm activity against isogenic EAEC mutants, molecular docking simulations and comparative genomic analysis were used to identify the mechanism of action of one hit.
Principal findings
In all, five compounds (1.25%) reproducibly inhibited biofilm accumulation by at least one strain by 30-85% while inhibiting growth by under 10%. Hits exhibited at least 10-fold greater antibiofilm activity than nitazoxanide, the only known EAEC biofilm inhibitor. Reflective of known EAEC heterogeneity, only one hit was active against both screen isolates, but three hits showed broad antibiofilm activity against a larger panel of strains. Mechanism of action studies point to the EAEC anti-aggregation protein (Aap), dispersin, as the target of compound MMV687800.
Conclusions
This study identified five compounds not previously described as anti-adhesins or Gram-negative antibacterials with significant and specific EAEC antibiofilm activity. One molecule, MMV687800, targets the EAEC Aap. In vitro small-molecule inhibition of EAEC colonization opens a way to new therapeutic approaches to preventing and treating EAEC infection.
Author summary
Diarrhoea accounts for over half a million deaths in children under five annually. It additionally contributes to childhood malnutrition as well as growth and development deficiencies, particularly in low-income countries. Enteroaggregative Escherichia coli (EAEC) causes diarrhoea that is often persistent and can also contribute to growth deficiencies in young children. EAEC is a neglected pathogen that is often resistant to antimicrobial drugs. Small molecules that block EAEC colonization may hold the key to interfering with EAEC disease without promoting antimicrobial resistance. We screened the Medicines for Malaria Ventures Pathogen Box for chemicals that can interfere with EAEC biofilm formation, a key colonization indicator. Our screen identified five biofilm-inhibiting molecules that did not interfere with bacterial viability and therefore are unlikely to exert strong pressure for resistance. Molecular biology and computational investigations point to the EAEC anti-aggregative protein, also known as dispersin, as a possible target for one of these hit molecules. Optimizing EAEC antibiofilm hits will create templates that can be employed for resolving EAEC diarrhoea and related infections.
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