# Emergence of Multidrug-Resistant Escherichia coli Harbouring the CS31A Virulence Factor in Neonatal Calf Diarrhoea in Central France

## TL;DR

A study in central France found that multidrug-resistant Escherichia coli strains with the CS31A virulence factor are common in neonatal calf diarrhea, raising public health concerns.

## Contribution

This is the first large-scale study to report the correlation between multidrug resistance and virulence factors in E. coli from neonatal calf diarrhea.

## Key findings

- 84.9% of E. coli strains carrying adhesins were multidrug-resistant.
- CS31A-producing E. coli was the most prevalent virulence factor.
- Calf production may serve as a reservoir for multidrug-resistant E. coli, regardless of virulence factor presence.

## Abstract

Enterotoxigenic Escherichia coli (ETEC) exhibits a high prevalence in Neonatal Calf Diarrhoea, leading to significant economic losses in the animal production sector. This study aimed to correlate the presence of virulence factor-producing multidrug-resistant E. coli in central France, specifically in the departments of Cantal, Haute-Loire, Loire, and Puy-de-Dôme. A large number of diarrhoeal stool samples from calves were analysed at TERANA Laboratories (France), revealing a high rate of multidrug-resistant E. coli, which harbour different virulence factors, namely fimbrial and non-fimbrial adhesins. Among E. coli strains carrying adhesins, a high prevalence of multidrug-resistance was observed, averaging 84.9%, with a predominance of CS31A-producing strains. These findings underscore the importance of monitoring the co-occurence of adhesins and multidrug-resistant profiles in E. coli from Neonatal Calf Diarrhoea, as they could serve as a reservoir for strains harbouring both determinants, thereby posing a significant public health risk. To our knowledge, this study represents the first large-scale report on the correlation between multidrug resistance profiles and virulence factors-producing E. coli isolated from cases of Neonatal Calf Diarrhoea.

Escherichia coli is a significant cause of Neonatal Calf Diarrhoea (NCD). Its extensive antigenic diversity, coupled with the ability to acquire antimicrobial resistance determinants, hampers treatment effectiveness and compromises the control measures. This study investigated the link between the presence of multidrug-resistant (MDR) E. coli and virulence factors (VFs) in NCD from central France (Departments of Cantal, Haute-Loire, Loire, and Puy-de-Dôme), between 2016 and 2022. E. coli was identified at TERANA Laboratories, France, using API 20E (BioMérieux®) and MALDI-TOF Mass Spectrometry. Virulence factors, namely adhesins, were assessed with the slide agglutination method, and antimicrobial susceptibility testing was conducted across various antimicrobial classes. Out of 2367 E. coli strains isolated from cases of NCD, a high percentage were resistant to aminopenicillins (88.8%), aminoglycosides (89.1%), tetracyclines (79.7%), quinolones (48.4%), and sulphonamides (42.4%). More than half (58.6%) carried VFs, and 84.9% exhibited MDR profile, of which 61.34% (1233/2010) also harboured VFs. The adhesin CS31A-producing E. coli was the most prevalent, followed by the fimbrial adhesins F5 and F17 (60.8%, 20.0%, and 8.3%, respectively), all of which were associated with a high prevalence of MDR strains (79.1–93.9%). The highest occurrence of MDR profiles was observed in E. coli strains carrying CS31A and in those lacking VFs, both groups showing co-resistance to aminopenicillins, aminoglycosides, and tetracyclines or sulphonamides. The calf production sector may act as a reservoir for MDR E. coli strains, regardless of the presence of VFs, posing a major threat to public health and safety.