Novel Isolate of Halobacteriovorax Capable of Killing Multi-Drug-Resistant Escherichia coli and Salmonella

TL;DR

A new strain of predatory bacteria, HE7, was found to kill antibiotic-resistant E. coli and Salmonella in the lab.

Contribution

A novel Halobacteriovorax strain (HE7) was isolated and shown to effectively kill multi-drug-resistant bacteria.

Findings

HE7 reduced MDR E. coli and Salmonella by about 6 logs within 6 hours in lab tests.

The predatory effect of HE7 lasted up to 24 hours against resistant bacteria.

Halobacteriovorax could serve as an alternative to antibiotics in combating AMR.

Abstract

Background/Objectives: Due to the rising problem of antimicrobial resistance, there is increasing attention in the scientific community towards alternative approaches to combat Antimicrobial-Resistant (AMR) pathogens that do not involve the use of antibiotics. In this regard, the European Medicines Agency (EMA) and the European Food Safety Authority (EFSA) have promoted experimentation with predatory bacteria to fight antibiotic resistance. With the aim of identifying predatory bacteria suitable for the control of antibiotic-resistant bacteria, in this work we isolated a strain of Halobacteriovorax from an estuarine aquatic environment using a CTX-M-producing E. coli strain as prey and characterized it with respect to optimal physico-chemical parameters for growth and predation. Furthermore, we studied its predatory capacity against other E. coli strains and Multi-Drug-Resistant (MDR) Salmonella. Finally, we conducted challenge experiments to evaluate the growth of predator and prey over time. Methods: The Halobacteriovorax strain, designated HE7, was identified by 16S rRNA analysis. To isolate Halobacteriovorax and to evaluate its predatory ability towards different preys, the double-layer agar plating technique was applied. Results: HE7 showed in vitro predatory activity against all MDR strains of E. coli and Salmonella tested. In the 107 predator/103 prey and 107 predator/107 prey challenges, HE7 after 6 h achieved the total killing and a reduction of about 6 logs in the prey, respectively, maintaining this effect for up to 24 h. Conclusions: The results of this study highlight that HE7, but more generally Halobacteriovorax, could find application both alone and in an integrated context of antimicrobial strategies as an alternative to antibiotics.

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