Capsular Type, Sequence Type and Microbial Resistance Factors Impact on DNase Activity of Streptococcus agalactiae Strains from Human and Bovine Origin

Abstract

Extracellular deoxyribonucleases (DNases) contribute to the spread of pathogenic bacteria through the evasion from host innate immunity. Our main objective was to evaluate the production of extracellular DNases by human and bovine Streptococcus agalactiae clinical strains and perform a correlation of genetic lineages and DNase activity with capsular type, genetic determinants, clinical origin (colonization and infection), and host (human or bovine). DNase activity was evaluated by qualitative and quantitative assays for a collection of 406 human (n = 285) and bovine (n = 121) strains. All (121/121) bovine were isolated from mastitis and revealed to be DNase (+), indicating a putative pathogenic role in this clinical scenario. From the human S. agalactiae strains, 86% (245/285) showed DNase activity, among which all strains belonging to capsular types, namely, Ia, Ib, III-2, and IV. All CC17 strains (n = 58) and 56/96 (58.3%) of the CC19 displayed DNase activity. DNase (–) strains belonged to the CC19 group. However, the subcharacterization of CC19 S. agalactiae strains through multiple-locus variable number tandem repeat analysis (MLVA), antibiotic resistance, mobile elements, and surface proteins did not provide any distinction among DNase producers and non-producers.The production of DNases by all human CC17 strains, about two-fifths of human CC19, and all bovine strains, suggest an important contribution of DNases to hypervirulence.

Comparative Genomic Analysis of Streptococcus dysgalactiae subspecies dysgalactiae Isolated From Bovine Mastitis in China

“…), immune reactive antigen (sip), iron and manganese uptake (shp, htsA to C), protease (htrA, clp), and peptidase (lspA) genes were widely distributed among all SDSD. These genes enable S. dysgalactiae to colonize (Roy et al, 2019;Diaz-Dinamarca et al, 2020), spread (Florindo et al, 2018) and survive in host tissues (De et al, 2017;Roy et al, 2019) and cause infection (Calonzi et al, 2020). HylB was the most abundant enzyme-related gene, and this high prevalence was consistent with previous studies (Ding et al, 2016;Calonzi et al, 2020;Lin et al, 2021).…”

The Role of Streptococcus spp. in Bovine Mastitis

“…The enzyme is capable of degrading the antimicrobial system induced by the neutrophils. It was shown in a study by Florindo that all of the S. agalactiae strains associated with subclinical or clinical mastitis in 121 clinical samples were capable of synthesizing DNAses [ 66 ]. This could imply that DNAse synthesis could be important for the development of bovine mastitis.…”

Global gene expression analysis ofStreptococcus agalactiaeat exponential growth phase

“…Indeed, as NETs (also composed by granule proteins and histones) [36, 40-41] are released by neutrophils to degrade virulence factors and to kill bacteria, this nuclease-mediated mechanism could play an important role in S. agalactiae virulence. Since then, although important knowledge has been acquired about S. agalactiae nucleases [4, 36, 42-43] very little is known about the complex molecular pathways and stimuli triggering the release of DNase’s in vitro and in vivo. Here, we conducted preliminary RNA-seq assays to understand whether direct DNA exposure could affect gene expression during the exponential growth phase of the DNase producer reference strain NEM316.…”