# Reprogrammed SimCells for antimicrobial therapy

## TL;DR

Scientists created tiny engineered cells that can target and kill antibiotic-resistant bacteria with high precision and efficiency.

## Contribution

A modular platform using engineered SimCells and mini-SimCells for targeted elimination of multidrug-resistant bacteria is introduced.

## Key findings

- Reprogrammed mini-SimCells eliminated over 97% of a targeted AMR E. coli strain within 48 hours.
- Multiple-dose treatment achieved a 103-fold reduction of targeted E. coli in mixed microbial communities.
- The platform uses T6SS and hydrogen peroxide generation to selectively kill bacteria with minimal impact on non-target species.

## Abstract

Antimicrobial-resistant (AMR) bacteria cause millions of deaths worldwide annually, representing a critical global health challenge. In this study, we developed a therapeutic platform using two types of chromosome-free, nonreplicating engineered bacterial cells: SimCells (1 to 2 µm) and mini-SimCells (100 to 400 nm). These SimCells were engineered to selectively bind to targeted Escherichia coli, facilitating precise delivery of toxic proteins via a Type VI secretion system (T6SS) and localized generation of hydrogen peroxide from aspirin. We demonstrate that mini-SimCells eliminated over 97% of a targeted AMR strain within 48 h. Moreover, multiple-dose administration achieved a selective 103-fold reduction of targeted E. coli in mixed microbial communities. This modular “plug-and-play” platform offers an adaptable solution against diverse multidrug-resistant pathogens.

Antimicrobial resistance (AMR) is a critical global health challenge. In this study, we developed a platform based on chromosome-free and nonreplicating simple cells (SimCells, size 1 to 2 µm) and mini-SimCells (size 100 to 400 nm) for targeted pathogen elimination. Engineered with surface-displayed nanobodies, SimCells and mini-SimCells selectively bind bacteria expressing specific antigens (e.g., OmpA in Escherichia coli). The selective interactions facilitate close SimCell-pathogen proximity, enabling two antimicrobial mechanisms: direct injection of toxic effectors into bacterial cytoplasm via a heterologous expression of type VI secretion system (T6SS), and enzymatic conversion of aspirin into catechol by engineered salicylate hydroxylase, leading to sustained local production of hydrogen peroxide (H2O2). Our results demonstrate that both reprogrammed SimCells and mini-SimCells can eliminate target E. coli with high specificity and efficiency. Multidose reprogrammed mini-SimCell treatment led to a 103-fold selective reduction of targeted bacteria in mixed microbial communities, with minimal disruption to nontarget bacteria. We demonstrate that reprogrammed mini-SimCells, engineered with nanobody targeting outer membrane protein OmpA of the clinically relevant multidrug-resistant pathogen E. coli ST131, achieved elimination efficiencies over 97% at 24 and 48 h. This modularized “plug-and-play” antimicrobial platform provides a highly specific, efficient, and adaptable solution for combating diverse AMR pathogens.