Streptococcus uberis is one of the primary causative agents of mastitis, a clinically and economically significant disease that affects dairy cattle worldwide. In this study, we analyzed 140 S. uberis strains isolated from mastitis milk samples collected from 74 cow herds in the Czech Republic. We employed whole-genome sequencing to screen for the presence of antimicrobial resistance (AMR) genes and genes encoding virulence factors, and to assess their genetic relationships. Our analysis revealed the presence of 88 different sequence types (STs), with 41% of the isolates assigned to global clonal complexes (GCCs), the majority of which were affiliated with GCC5. The STs identified were distributed across the major phylogenetic branches of all currently known STs. We identified fifty-one putative virulence factor genes, and the majority of isolates carried between 27 and 29 of these genes. A tendency of virulence factors and AMR genes to cluster with specific STs was observed, although such clustering was not evident within GCCs. Principal component analysis did not reveal significant diversity among isolates when grouped by GCC or ST prevalence. The substantial genomic diversity and the wide array of virulence factors found in S. uberis strains present a challenge for the implementation of effective anti-mastitis measures.

• Klíčová slova
• MLST, antimicrobial resistance genes, intramammary infection, mastitis, phylogenetic tree, sequence type, virulence genes,
• Publikační typ
• časopisecké články MeSH

Streptococcus uberis is one of the most important causative agents of mastitis and is a common reason for the use of antimicrobials in dairy cows. In this study, we assessed the antimicrobial susceptibility of 667 S. uberis isolates originating from 216 Czech dairy farms collected between 2019 and 2023 using the broth microdilution method. We tested 140 of the isolates for the presence of antimicrobial genes using whole-genome sequencing and evaluated their relationship with phenotypic resistance. Streptococcus uberis isolates showed high levels of resistance to tetracycline (59%), followed by streptomycin (38%) and clindamycin (29%). Although all of the isolates were susceptible to beta-lactams, a relatively high percentage of intermediately susceptible isolates was recorded for ampicillin (44%) and penicillin (18%). The isolates were mainly resistant to tetracycline alone (31.3%); the second most frequent occurrence of the phenotypic profile was simultaneous resistance to tetracycline, streptomycin, and clindamycin (16.6%). The occurrence of antibiotic resistance genes did not always match the phenotypic results; in total, 36.8% of isolates that possessed the ant(6)-Ia gene did not show phenotypic resistance to streptomycin. To a lesser extent, silent genes were also detected in clindamycin and tetracycline. This study confirmed the high susceptibility of S. uberis to penicillins used as first-line antimicrobials for S. uberis mastitis treatment.

• Klíčová slova
• Streptococcus uberis, antimicrobial resistance gene, antimicrobial resistence, bovine mastitis, intramammary infection, whole-genome sequencing,
• Publikační typ
• časopisecké články MeSH

In this study, we focused analyzing γδ T cells during bovine mammary gland inflammation induced by Streptococcus uberis. A mammary gland cell suspension was obtained using lavage 24, 48, 72, and 168 h after intramammary-induced infection. The proportion of lymphocytes increased during the entire week in which inflammation was present. The γδ T cells were also elevated during inflammation, reaching their peak at 72 h following induced inflammation. The percentage of apoptotic lymphocytes continually increased, with the highest proportion occurring 168 h after S. uberis infection. The results show that γδ T cells may be involved in the resolution of inflammation in bovine mammary glands, with the apoptosis of those cells potentially playing an important role.

• Klíčová slova
• Streptococcus uberis, T cell, apoptosis, lymphocyte, mammary gland, mastitis,
• Publikační typ
• časopisecké články MeSH

Farmers should focus on milk quality over quantity because milk that contains unsuitable components and/or antibiotic residues, or has a high somatic cell count, cannot be used in food production and thereby results in reduced milk yield. One of the main problems affecting the ultimate milk yield of dairy cows is mastitis. This disease is the most serious economic and health problem associated with dairy cow herds and is a major reason for excessive culling. Therefore, many studies have addressed this problem to further our understanding of the agents causing mastitis and their classification and virulence factors. This review summarizes the current knowledge regarding mastitis prevalence, the characteristics of its main causative agents, and the effects of mastitis on dairy production. The review also intends to provide guidance for future studies by examining external effects influencing dairy production in cows under field conditions.

• Klíčová slova
• causative agent, dairy production, mastitis, milk, somatic cell count,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

The aim of this study was to evaluate whether apoptosis of lymphocytes is modulated by stimulation by lipopolysaccharide (LPS) of Escherichia coli or muramyl dipeptide (MDP). Cell populations were obtained by lavaging of the mammary glands 24, 48, 72, and 168 hours following intramammary induced inflammation. The portion of apoptotic lymphocytes peaked at 48 hours after treatment with LPS or MDP. The analysis of CD44 expression of the same cell populations showed a higher percentage of CD44-positive lymphocytes 24- and 48-hours following induction of inflammation by LPS or MDP. The results demonstrate that during both experimental infection of bovine mammary glands with LPS or MDP, apoptosis of lymphocytes was induced in the initial phase of the inflammatory response and CD44 was also overexpressed at the beginning of inflammation. These data suggest a connection of lymphocyte apoptosis with the expression of CD44 receptors.

• Klíčová slova
• CD44, Escherichia coli, apoptosis, lipopolysaccharide, lymphocyte, mammary gland, mastitis, muramyl dipeptide,
• Publikační typ
• časopisecké články MeSH