# Potential Convergence to Accommodate Pathogenicity Determinants and Antibiotic Resistance Revealed in Salmonella Mbandaka

## TL;DR

This study investigates the genetic factors behind drug resistance and virulence in Salmonella Mbandaka, a multidrug-resistant strain linked to human infections.

## Contribution

The study identifies genetic determinants and plasmid roles in S. Mbandaka's antimicrobial resistance and pathogenicity.

## Key findings

- S. Mbandaka strain SMEH showed resistance to four antibiotics including chloramphenicol and tetracycline.
- SMEH exhibited higher macrophage infection and HeLa cell invasion compared to S. Typhimurium.
- Genetic elements like SPI-1, SPI-2, and SPI-6 were linked to pathogenicity and resistance in S. Mbandaka.

## Abstract

Salmonella species are causal pathogens instrumental in human food-borne diseases. The pandemic survey related to multidrug resistant (MDR) Salmonella genomics enables the prevention and control of their dissemination. Currently, serotype Mbandaka is notorious as a multiple host-adapted non-typhoid Salmonella. However, its epidemic and MDR properties are still obscure, especially its genetic determinants accounting for virulence and MD resistance. Here, we aim to characterize the genetic features of a strain SMEH pertaining to Salmonella Mbandaka (S. Mbandaka), isolated from the patient’s hydropericardium, using cell infections, a mouse model, antibiotic susceptibility test and comparative genomics. The antibiotic susceptibility testing showed that it could tolerate four antibiotics, including chloramphenicol, tetracycline, fisiopen and doxycycline by Kirby–Bauer (K-B) testing interpreted according to the Clinical and Laboratory Standards Institute (CLSI). Both the reproducibility in RAW 264.7 macrophages and invasion ability to infect HeLa cells with strain SMEH were higher than those of S. Typhimurium strain 14028S. In contrast, its attenuated virulence was determined in the survival assay using a mouse model. As a result, the candidate genetic determinants responsible for antimicrobial resistance, colonization/adaptability and their transferability were comparatively investigated, such as bacterial secretion systems and pathogenicity islands (SPI-1, SPI-2 and SPI-6). Moreover, collective efforts were made to reveal a potential role of the plasmid architectures in S. Mbandaka as the genetic reservoir to transfer or accommodate drug-resistance genes. Our findings highlight the essentiality of antibiotic resistance and risk assessment in S. Mbandaka. In addition, genomic surveillance is an efficient method to detect pathogens and monitor drug resistance. The genetic determinants accounting for virulence and antimicrobial resistance underscore the increasing clinical challenge of emerging MDR Mbandaka isolates, and provide insights into their prevention and treatment.