Evidence of Common Isolates of Streptococcus agalactiae in Bovines and Humans in Emilia Romagna Region (Northern Italy).

Elena Carra,Matteo Ricchi,Chiara Garbarino,Federica Bergamini,Silvia Piva,Alessia Micheli,Roberta Schiavo,Simone Russo,Giuseppe Merialdi,Norma Arrigoni,Patrizia Bassi,Alice Prosperi,Andrea Serraino,Monica Cricca

doi:10.3389/fmicb.2021.673126

Abstract

Streptococcus agalactiae (group B Streptococcus, GBS) is one of the most important agents of bovine mastitis and causes remarkable direct and indirect economic losses to the livestock sector. Moreover, this species can cause severe human diseases in susceptible individuals. To investigate the zoonotic potential of S. agalactiae, 203 sympatric isolates from both humans and cattle, isolated in the same time frame (2018) and in the same geographic area (Emilia Romagna region, Northern Italy), were characterized by molecular capsular typing (MCT), pilus island typing (PI), and multi-locus sequence typing (MLST). In addition, antibiotic-resistant phenotypes were investigated. The distribution of the allelic profiles obtained by combining the three genotyping methods (MCT-PI-MLST) resulted in 64 possible genotypes, with greater genetic variability among the human compared to the bovine isolates. Although the combined methods had a high discriminatory power (>96,2%), five genotypes were observed in both species (20,9% of the total isolates). Furthermore, some of these strains shared the same antibiotic resistance profiles. The finding of human and bovine isolates with common genotypes and antibiotic resistance profiles supports the hypothesis of interspecies transmission of S. agalactiae between bovines and humans.

Highlights

Streptococcus agalactiae (Group B Streptococcus, GBS) is one of the etiological agents of bovine contagious mastitis
Our research aimed to investigate whether S. agalactiae isolates circulating in cattle and humans shared the same genotyping profiles and the same antibiotic-resistant phenotypes
All Selected Isolates Were Confirmed to Be S. agalactiae Using Species-Specific PCR The results of molecular capsular typing (MCT) on the selected cattle and human isolates are reported in Supplementary Tables 1, 2, respectively

Summary

Introduction

Streptococcus agalactiae (Group B Streptococcus, GBS) is one of the etiological agents of bovine contagious mastitis. During the 1950s, this bacterium was the leading cause of mastitis in Europe (Katholm et al, 2012; Mweu et al, 2012). After the Common S. agalactiae Isolates in Bovines and Humans application of control plans from 1960–2000, the prevalence of the infection gradually decreased, leading to disease eradication in some countries (Skoff et al, 2009; Lambertsen et al, 2010; Katholm et al, 2012). In the 21st century, due to major changes in dairy farm management in most European countries, such as reductions in the number of farms, increased herd sizes, introduction of robotic milking systems, and selective antibiotic treatments at drying off, the prevalence of S. agalactiae infection in cattle has increased, and is considered a re-emerging problem (Skoff et al, 2009; Lambertsen et al, 2010; Katholm et al, 2012).

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