Virulence Factor Genes and Cytotoxicity of Streptococcus agalactiae Isolated from Bovine Mastitis in Poland

Genomic Diversity, Virulome, and Resistome of Streptococcus agalactiae in Northeastern Brazil: Are Multi-Host Adapted Strains Rising?

Streptococcus agalactiae, known as group B streptococci (GBS), colonizes the digestive and genitourinary tracts and causes neonatal diseases and infections in immunocompromised and elderly individuals. GBS neonatal disease prevention includes intrapartum antibiotic prophylaxis. We characterized 101 GBS isolates obtained from patients in João Pessoa, northeastern Brazil, owing to the need to develop and implement vaccines to prevent GBS infections. Capsular types were determined using multiplex-PCR, and antibiotic susceptibility profiles were determined using disc diffusion or the gradient strip method. Clonal diversity was evaluated using pulsed-field gel electrophoresis. Fourteen selected isolates had the genome sequenced and evaluated for virulence and resistance genes. The GBS population had high clonal diversity, with serotype Ia and V prevalence. Among the sequenced isolates, we detected antibiotic resistance genes (ant(6)-Ia, catA8, ermA, ermB, lsaE, lsnuB, mefA/msrD, tetM, tetO, and tetS), several virulence genes, and mobile genetic elements integrated into the chromosome. The most frequent Sequence Type (ST) was ST144, followed by ST196, ST28, ST19, ST12, ST23, ST103, and the new ST1983 (CC103). Phylogenetically, ST103 and ST1983 were distant from the other STs. Our data revealed highly virulent GBS strains in this population and a new ST that could be related to a zoonotic origin.

Capsular Typing and Molecular Characterization of Streptococcus agalactiae Strains Isolated From Bovine Mastitis in Iran

Streptococcus agalactiae infections may cause clinical or subclinical mastitis in dairy cows by invading the mammary gland. This research included the isolation of 29 strains of S. agalactiae from 425 milk samples obtained from cows affected by clinical mastitis in Chaharmahal and Bakhtiari province, Iran. The antimicrobial sensitivity of S. agalactiae strains was determined using 16 antibiotics from seven different classes. The epidemiological spread of S. agalactiae was determined by identifying the serotypes of isolates using multiplex PCR. In addition, the presence of antibiotic-resistance genes and virulence genes were investigated to infer the pathogenicity and antibiotic resistance of S. agalactiae using the multiplex PCR method. A total of 29 strains of S. agalactiae, which constitute 6.82% of the samples, were identified based on phenotypic traits, biochemical properties and dltR gene amplification. Multiplex serotype polymerase chain reaction study showed that most of the isolates belonged to Type III serotype. Phenotypically, 100% of the isolated strains were resistant to tetracycline and penicillin. The frequency of resistance to beta-lactams (penicillin and amoxicillin) was 100% and 82.75%. tetM, tetO and tetT genes, responsible for resistance to tetracyclines, were found in all samples, corresponding to the drug-resistant phenotype. Among the genes related to the virulence factor, 100% of the isolates had the dlts gene. The examination of virulence genes revealed that the majority of isolates included the cfb, pavA and scPb genes. This data has the potential to assist in the prevention and management of mastitis and enhance our comprehension of epidemiological patterns in dairy cows affected by S. agalactiae in Chaharmahal and Bakhtiari province.

Current research update on group B streptococcal infection related to obstetrics and gynecology

Group B streptococcal (GBS) is a Gram-positive bacterium that is commonly found in the gastrointestinal tract and urogenital tract. GBS infestation during pregnancy is a significant contributor to maternal and neonatal morbidity and mortality globally. This article aims to discuss the infectious diseases caused by GBS in the field of obstetrics and gynecology, as well as the challenges associated with the detection, treatment, and prevention of GBS.

Antibacterial activity and mechanism of chelerythrine against Streptococcus agalactiae

Streptococcus agalactiae (S.agalactiae), also known as group B Streptococcus (GBS), is a highly infectious pathogen. Prolonged antibiotic usage leads to significant issues of antibiotic residue and resistance. Chelerythrine (CHE) is a naturally occurring benzophenidine alkaloid and chelerythrine chloride (CHEC) is its hydrochloride form with diverse biological and pharmacological activities. However, the antibacterial mechanism of CHEC against GBS remains unclear. Thus, this study aims to investigate the in vitro antibacterial activity of CHEC on GBS and elucidate its underlying mechanism. The antibacterial effect of CHEC on GBS was assessed using inhibitory zone, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) assays, as well as by constructing a time-kill curve. The antibacterial mechanism of CHEC was investigated through techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM), measurement of alkaline phosphatase (AKP) activity, determination of Na+ K+, Ca2+ Mg2+-adenosine triphosphate (ATP) activity, observation of membrane permeability, and analysis of intracellular reactive oxygen species (ROS) and mRNA expression levels of key virulence genes. The results demonstrated that the inhibition zone diameters of CHEC against GBS were 14.32 mm, 12.67 mm, and 10.76 mm at concentrations of 2 mg/mL, 1 mg/mL, and 0.5 mg/mL, respectively. The MIC and MBC values were determined as 256 μg/mL and 512 μg/mL correspondingly. In the time-kill curve, 8 × MIC, 4 × MIC and 2 × MIC CHEC could completely kill GBS within 24 h. SEM and TEM analyses revealed significant morphological alterations in GBS cells treated with CHEC including shrinkage, collapse, and leakage of cellular fluids. Furthermore, the antibacterial mechanism underlying CHEC's efficacy against GBS was attributed to its disruption of cell wall integrity as well as membrane permeability resulting in extracellular release of intracellular ATP, AKP, Na+ K+, Ca2+ Mg2+. Additionally CHEC could increase the ROS production leading to oxidative damage and downregulating mRNA expression levels of key virulence genes in GBS cells. In conclusion, CHEC holds potential as an antimicrobial agent against GBS and further investigations are necessary to elucidate additional molecular mechanisms.

Characterization of Virulence Factors and Antimicrobial Susceptibility of Streptococcus agalactiae Associated with Bovine Mastitis Cases in Thailand

Streptococcus agalactiae is a contagious pathogen that causes bovine mastitis. The ability of S. agalactiae to cause widespread mastitis relies on bacterial virulence factors. In this study, we detected 10 virulence determinants associated with mastitis pathogenicity using conventional PCR. The antimicrobial susceptibility of 100 S. agalactiae isolates from 13 Thai dairy herds was assessed using the Kirby-Bauer disk diffusion susceptibility test. All strains had at least three virulence factors responsible for invasion, adhesion, and infection (fbsB, bibA, and cfb, respectively). The predominant virulent profile of S. agalactiae strains revealed the presence of fbsA, fbsB, bibA, cfb, and cyl (n = 96). Most strains were sensitive to penicillin, ampicillin, amoxicillin-clavulanic acid, cefotaxime, ceftiofur, erythromycin, sulfamethoxazole-trimethoprim, and vancomycin. However, all strains were resistant to aminoglycosides, including kanamycin and gentamicin attributed to the unnecessary antimicrobial use. Furthermore, we identified seven multidrug resistant (MDR) S. agalactiae strains among four dairy herds, of which, two were vancomycin resistant. Our study provides profiles for virulence factors and antimicrobial susceptibility, which are beneficial for the clinical monitoring, prevention, and control of bovine mastitis in dairy cattle in Thailand. Moreover, we emphasize the need for awareness regarding the judicious use of antimicrobials on dairy farms.

Evaluation of Streptococcus species isolated from subclinical sheep mastitis by molecular methods and determination of virulence factors and antimicrobial resistance genes

Streptococcus (S.) species are important pathogens that cause mastitis in sheep. The study aimed to examine Streptococcus species in sheep milk with subclinical mastitis, assessing their prevalence, antimicrobial resistance, and virulence genes. A total of 200 milk samples were collected from sheep farms in İzmir's five districts. Out of 32 (28.6%) Streptococcus isolates identified by phenotypic methods, 25 were genotypically identified as S. uberis, 5 as S. agalactiae, and 2 as S. dysgalactiae. Disk diffusion was used to determine the antimicrobial resistance of the isolates. PCR was employed to identify antimicrobial resistance and virulence genes in the isolates. The highest resistance was found for cloxacillin (100%), and the highest sensitivity was found for florfenicol (84%). The most common resistance gene combination was tetM+tetS (3/32) for S. uberis in 9.4%. A total of five virulence genes were detected. GapC+sua (56.2%) constituted the most common gene pattern. The highest virulence gene gapC was detected in 78.1% (25/32) of the isolates. The cylE gene was not detected (0%) in the isolates. Streptococcus species may play a role in mastitis in sheep, emphasising the need for meticulous hygienic milking practices.