Comparison of virulence factors and capsular types of Streptococcus agalactiae isolated from human and bovine infections

Genotype Distribution and High-Risk Factors Analysis of Group B Streptococcus in Late-Stage Pregnant Women in the Linyi Region

Objective: To understand the colonization status of Group B Streptococcus (GBS) in the reproductive tract of pregnant women in the Linyi region, the drug resistance, genotype distribution, and molecular epidemiological characteristics of GBS, and to explore the high-risk factors for GBS infection in late-stage pregnant women. Methods: A total of 3269 pregnant women at 35-37 weeks of gestation who visited the Obstetrics Department of Linyi Maternal and Child Health Hospital from January 2019 to December 2021 were selected as the study subjects. Vaginal and rectal swabs were collected for GBS culture. Based on the culture results, they were divided into positive and negative groups. The high-risk factors such as age, BMI index, education level, pregnancy vomiting, and liver function indicators of the two groups were analyzed. Drug sensitivity test, multilocus sequence typing (MLST) gene typing, and virulence factor detection were performed on GBS (+) strains. Results: The infection rate of GBS in the reproductive tract of pregnant women in late pregnancy in the Linyi region was 7.07% (231/3269). The analysis of high-risk factors showed that having a college degree or above and absence of pregnancy vomiting; elevated levels of alanine aminotransferase, albumin, globulin, direct bilirubin, glutamyl transferase, and total bile acids; and decreased levels of alkaline phosphatase and lactate dehydrogenase were high-risk factors for GBS infection (p < 0.05). The MLST results showed that a total of 189 GBS strains were identified with 20 genotypes, the top four being ST10 type (25.40%), ST19 type (17.99%), ST529 type (13.76%), and ST862 type (12.70%). The 20 ST came from 8 CCs, with the main CC groups being CC12 (29.11%), CC19 (24.87%), CC103 (18.00%), and CC327 (13.76%). GBS strains showed high sensitivity to vancomycin, penicillin, and levofloxacin, all being 100%; sensitivity to erythromycin, clindamycin, compound novobiocin, and tetracycline was relatively low; there were statistically significant differences in resistance to erythromycin, clindamycin, and levofloxacin among different genotypes of GBS (p < 0.05). The detection rates of GBS virulence factors hylB (81.46%) and scpB (80.98%) were the highest. In ST10 type, > 90% of strains carried bac, bca, hylB, and scpB; in ST19 and ST529, > 90% of strains carried hylB and scpB; and in ST862, > 90% of strains carried CPSIII. Conclusion: The colonization rate of GBS in the reproductive tract of pregnant women in late pregnancy in the Linyi region is 7.07%. Having a college degree or above, absence of pregnancy vomiting, elevated levels of albumin, globulin, direct bilirubin, glutamyl transferase, and total bile acids, and decreased levels of alkaline phosphatase and lactate dehydrogenase are high-risk factors for GBS infection; ST10, ST19, ST529, and ST862 are the main genotypes prevalent in this region; there are regional differences in the distribution of GBS genotypes and CC groups; there are statistically significant differences in the distribution of virulence factors among GBS strains with different MLST genotypes (p < 0.05); GBS shows high sensitivity to penicillin drugs and can still be used as the preferred medication for the prevention and treatment of GBS infection.

Molecular characterization, antimicrobial resistance and invasion of epithelial cells by Streptococcus agalactiae strains isolated from colonized pregnant women and newborns in Rio de Janeiro, Brazil

AIMS

To evaluate the prevalence, molecular characteristics, antimicrobial susceptibility, and epithelial invasion of Streptococcus agalactiae strains isolated from pregnant women and newborns in Rio de Janeiro, Brazil.

METHODS AND RESULTS

A total of 67 S. agalactiae isolates, 48 isolates from pregnant women and 19 from neonates, were analyzed. Capsular type Ia and V were predominant (35.8%/each). The multilocus sequence typing analysis revealed the presence of 19 STs grouped into 6 clonal complexes with prevalence of CC17/40.3% and CC23/34.3%. The lmb and iag virulence genes were found in 100% of isolates. Four S. agalactiae strains, belonging to CC17/ST1249 and CC23/ST23, were able to adhere to A549 respiratory epithelial cells. Antimicrobial resistance was verified mainly to tetracycline (85%), erythromycin (70.8%), and clindamycin (58.3%). Four S. agalactiae isolates were multidrug resistant. The resistance genes tested were found in 92.5% of isolates for tetM, 58.2% for ermB, 28.4% for mefAE, and 10.4% for tetO.

CONCLUSION

The study showed a high prevalence of virulence and antimicrobial genes in S. agalactiae strains isolated from pregnant women and newborns, supporting the idea that continued surveillance is necessary to identify risk factors and perform long-term follow-up in pregnant women and neonates in Rio de Janeiro.

Genome analysis of Streptococcus spp. isolates from animals in pre-antibiotic era with respect to antibiotic susceptibility and virulence gene profiles

Lyophilized Streptococcus spp. isolates (n = 50) from animal samples submitted to the diagnostic laboratory at the University of Connecticut in the 1940s were revivified to investigate the genetic characteristics using whole-genome sequencing (WGS). The Streptococcus spp. isolates were identified as follows; S. agalactiae (n = 14), S. dysgalactiae subsp. dysgalactiae (n = 10), S. dysgalactiae subsp. equisimils (n = 5), S. uberis (n = 8), S. pyogenes (n = 7), S. equi subsp. zooepidemicus (n = 4), S. oralis (n = 1), and S. pseudoporcinus (n = 1). We identified sequence types (ST) of S. agalactiae, S. dysgalactiae, S. uberis, S. pyogenes, and S. equi subsp. zooepidemicus and reported ten novel sequence types of those species. WGS analysis revealed that none of Streptococcus spp. carried antibiotic resistance genes. However, tetracycline resistance was observed in four out of 15 S. dysgalactiae isolates and in one out of four S. equi subsp. zooepidemicus isolate. This data highlights that antimicrobial resistance is pre-existed in nature before the use of antibiotics. The draft genome sequences of isolates from this study and 426 complete genome sequences of Streptococcus spp. downloaded from BV-BRC and NCBI GenBank database were analyzed for virulence gene profiles and phylogenetic relationships. Different Streptococcus species demonstrated distinct virulence gene profiles, with no time-related variations observed. Phylogenetic analysis revealed high genetic diversity of Streptococcus spp. isolates from the 1940s, and no clear spatio-temporal clustering patterns were observed among Streptococcus spp. analyzed in this study. This study provides an invaluable resource for studying the evolutionary aspects of antibiotic resistance acquisition and virulence in Streptococcus spp.

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.

Genotypic and antimicrobial susceptibility of Streptococcus agalactiae causing bovine mastitis in the central region of Thailand

Introduction

Streptococcus agalactiae is a highly contagious pathogen that causes bovine mastitis, leading to significant economic losses. This study aimed to (1) identify and characterize S. agalactiae strains responsible for bovine mastitis by examining their phenotypic and genotypic characteristics in Thai dairy-intensive farming areas and (2) determine their susceptibility profiles to antimicrobial agents.

Material and methods

In total, 100 S. agalactiae isolates obtained from clinical and subclinical mastitis cases from 13 dairy herds located in the central region of Thailand were examined. To confirm the identity of the bacterial pathogens, conventional microbiological procedures recommended by the National Mastitis Council (NMC) and the VITEK® 2 system were employed.

Results

All 100 isolates were successfully identified as S. agalactiae using the NMC procedure, whereas 94 isolates were identified as S. agalactiae using the VITEK® 2 system. Finally, the S. agalactiae-specific gene dlt S was identified in all the examined isolates using polymerase chain reaction. Capsular polysaccharide (CPS) typing revealed that all strains belonged to CPS type Ia. Multilocus sequence typing identified 33 selected isolates as sequence type 103. Random amplified polymorphic DNA (RAPD) typing yielded 43 RAPD types, with 6 RAPD clusters identified. These results demonstrated a high level of genetic diversity among S. agalactiae within the studied herds. RAPD analysis suggested that specific S. agalactiae strains could persist in dairy farms for 2-12 months. Furthermore, antimicrobial susceptibility testing was performed using the broth microdilution method. Most strains demonstrated susceptibility to ampicillin, penicillin, penicillin/novobiocin, cephalothin, oxacillin, ceftiofur, and erythromycin.

Discussion

This study revealed the phenotypic and genotypic characteristics of S. agalactiae isolates responsible for bovine mastitis in the central region of Thailand. The rapid identification of S. agalactiae and application of molecular typing methods can provide valuable epidemiological information regarding S. agalactiae causing mastitis in dairy farms. The antimicrobial susceptibility of S. agalactiae indicates that antimicrobial treatment for control and eradication could be a successful protocol. Our findings revealed that a single clonal strain of S. agalactiae affected the 13 studied farms. Further research is needed to explore the feasibility of vaccine development and application.

Identification of histidine kinase inhibitors through screening of natural compounds to combat mastitis caused by Streptococcus agalactiae in dairy cattle

BACKGROUND

Mastitis poses a major threat to dairy farms globally; it results in reduced milk production, increased treatment costs, untimely compromised genetic potential, animal deaths, and economic losses. Streptococcus agalactiae is a highly virulent bacteria that cause mastitis. The administration of antibiotics for the treatment of this infection is not advised due to concerns about the emergence of antibiotic resistance and potential adverse effects on human health. Thus, there is a critical need to identify new therapeutic approaches to combat mastitis. One promising target for the development of antibacterial therapies is the transmembrane histidine kinase of bacteria, which plays a key role in signal transduction pathways, secretion systems, virulence, and antibiotic resistance.

RESULTS

In this study, we aimed to identify novel natural compounds that can inhibit transmembrane histidine kinase. To achieve this goal, we conducted a virtual screening of 224,205 natural compounds, selecting the top ten based on their lowest binding energy and favorable protein-ligand interactions. Furthermore, molecular docking of eight selected antibiotics and five histidine kinase inhibitors with transmembrane histidine kinase was performed to evaluate the binding energy with respect to top-screened natural compounds. We also analyzed the ADMET properties of these compounds to assess their drug-likeness. The top two compounds (ZINC000085569031 and ZINC000257435291) and top-screened antibiotics (Tetracycline) that demonstrated a strong binding affinity were subjected to molecular dynamics simulations (100 ns), free energy landscape, and binding free energy calculations using the MM-PBSA method.

CONCLUSION

Our results suggest that the selected natural compounds have the potential to serve as effective inhibitors of transmembrane histidine kinase and can be utilized for the development of novel antibacterial veterinary medicine for mastitis after further validation through clinical studies.

Molecular epidemiology, drug resistance, and virulence gene analysis of Streptococcus agalactiae isolates from dairy goats in backyard farms in China

Streptococcus agalactiae infections may lead to clinical or subclinical mastitis in dairy animals when it invades the mammary gland. In this study, 51 S. agalactiae strains were isolated from 305 milk samples that were collected from goats with mastitis in 13 provinces of China. The antimicrobial resistance of S. agalactiae was determined by disk diffusion methods against 18 antibiotics from six classes. In addition, multilocus sequence typing (MLST), and the presence of resistance and virulence genes was determined by PCR analysis. Seven sequence types in five clonal complexes were identified according to MLST; CC103 and CC67 strains were predominant, with rates of 45.1% and 39.2%, respectively. All isolates (100%) were multiresistant to three or more antimicrobial agents. S. agalactiae isolates had a 100% resistance rate to penicillin, oxacillin, and amoxicillin, followed by doxycycline (82.4%), tetracycline (76.5%), and amikacin (74.5%). The lowest resistance was observed for ciprofloxacin (29.4%), which varied in five different regions. The detection rates of six classes of antimicrobial-related genes were calculated as follows: 33 (64.7%) for β-lactam-related resistance gene, 12 (23.5%) for tetracyclines, 11 (21.6%) for quinolone-related resistance genes, 10 (19.6%) for aminoglycosides, 7 (13.7%) for macrolides (ermA, ermB, and mefA), and 3 (5.9%) for lincosamide (lnu(B)). Regarding virulence genes, profile 1 (bca cfb-cspA-cylE-hylB-bibA-pavA-fbsA-fbsB) was the most prevalent, with a detection rate of 54.9%. This work provides a primary source related to the molecular epidemiology of S. agalactiae in dairy goat herds in China and will aid in the clinical treatment, prevention, and control of mastitis.

Antimicrobial Resistance and Virulence Genes of Streptococcus Agalactiae Isolated from Mastitis Milk Samples in China

Introduction

Streptococcus agalactiae is an important zoonotic pathogen that affects milk production and quality and poses a threat to public health. Treatment of infections with this bacterium exploits antimicrobials, to which the resistance of S. agalactiae is a growing problem. Addressing the possibility of a correlation between this pathogen's genetic factors for antimicrobial resistance and virulence, this study attempted to identify the relevant genes.

Material and Methods

Antimicrobial resistance of S. agalactiae isolated from 497 Chinese bovine mastitic milk samples was detected by the broth microdilution method. Eight drug resistance genes and eleven virulence genes were detected using PCR.

Results

Streptococcus agalactiae was 100% susceptible to rifampicin and vancomycin, 93.33% susceptible to sulfisoxazole and sulfamethoxazole, but 100% resistant to ≥3 of the 16 antimicrobial agents, thereby being multidrug resistant, with resistance to oxacillin, tetracycline, erythromycin, clindamycin, and gentamicin being common. The ermB, ermA and lnuA genes were carried by 73.33%, 66.67% and 60.00% of the strains, respectively. The carriage rates of the glnA, clyE, hylB, bibA, iagA, and fbsA virulence genes were greater than 40%, lmb and bac were not observed in any strain, and glnA+hylB+bibA+iagA+fbsA+clyE combined virulence gene patterns were the most commonly detected.

Conclusion

Antimicrobial resistance of S. agalactiae is still a great concern for cattle health in China, and multidrug resistance coupled with the high positive rates of this bacterium's strains for virulence genes indicates the importance of S. agalactiae surveillance and susceptibility tests.

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

Streptococcus agalactiae can produce a wide variety of virulence factors, including toxins and proteins which facilitate adhesion to and colonization and invasion of the host cells. There are few reports on the characteristics of field isolates from bovine mastitis in Poland. Thus, the aim of this study was to determine the occurrence of types of hemolysis on blood agar, virulence factor genes, and cytotoxicity of S. agalactiae isolates derived from cows with mastitis across Poland. The study included 68 isolates. Virulence genes were tested using standard PCR, and cytotoxicity was determined using methylthiazol tetrazolium (MTT) and lactate dehydrogenase (LDH) tests. Among the tested isolates, 89.7% were β-hemolytic, 8.8% γ-hemolytic, and 1.5% alpha-hemolytic. The only genes detected in all isolates were the cfb, cspA, hylB, and sip genes. Cytotoxicity assessment based on the LDH test revealed that isolates were cytotoxic only to Vero cells. However, according to the results obtained from the MTT test, more than half of the isolates exhibited low cytotoxicity to both SK and Vero cells, whereas the other isolates showed moderate or no cytotoxicity to both cell lines. Our research confirms the prevalence of various virulence genes in S. agalactiae isolated from Polish dairy herds, which have previously been found in isolates recovered from human and animal infections. For the first time, the presence of bac- and scpB-positive isolates of S. agalactiae was determined in Polish dairy cattle, and the cytotoxicity of bovine isolates was assessed. IMPORTANCE We believe that this manuscript is one of the few reports on the characteristics of field S. agalactiae isolates derived from cases of bovine mastitis in cows in Poland in terms of the occurrence of virulence genes and cytotoxicity. For the first time, the presence of bac- and scpB-positive isolates of S. agalactiae was determined in Polish dairy cattle, and the cytotoxicity of bovine isolates was assessed.

Molecular typing and prevalence of antibiotic resistance and virulence genes in Streptococcus agalactiae isolated from Chinese dairy cows with clinical mastitis

Bovine mastitis is a common disease occurring in dairy farms and can be caused by more than 150 species of pathogenic bacteria. One of the most common causative organisms is Streptococcus agalactiae, which is also potentially harmful to humans and aquatic animals. At present, research on S. agalactiae in China is mostly concentrated in the northern region, with limited research in the southeastern and southwestern regions. In this study, a total of 313 clinical mastitis samples from large-scale dairy farms in five regions of Sichuan were collected for isolation of S. agalactiae. The epidemiological distribution of S. agalactiae was inferred by serotyping isolates with multiplex polymerase chain reaction. Susceptibility testing and drug resistance genes were detected to guide the clinical use of antibiotics. Virulence genes were also detected to deduce the pathogenicity of S. agalactiae in Sichuan Province. One hundred and five strains of S. agalactiae (33.6%) were isolated according to phenotypic features, biochemical characteristics, and 16S rRNA sequencing. Serotype multiplex polymerase chain reaction analysis showed that all isolates were of type Ia. The isolates were up to 100% sensitive to aminoglycosides (kanamycin, gentamicin, neomycin, and tobramycin), and the resistance rate to β-lactams (penicillin, amoxicillin, ceftazidime, and piperacillin) was up to 98.1%. The TEM gene (β-lactam-resistant) was detected in all isolates, which was in accordance with a drug-resistant phenotype. Analysis of virulence genes showed that all isolates harbored the cfb, cylE, fbsA, fbsB, hylB, and α-enolase genes and none harbored bac or lmb. These data could aid in the prevention and control of mastitis and improve our understanding of epidemiological trends in dairy cows infected with S. agalactiae in Sichuan Province.

The Role of Streptococcal Cell-Envelope Proteases in Bacterial Evasion of the Innate Immune System

Bacteria possess the ability to evolve varied and ingenious strategies to outwit the host immune system, instigating an evolutionary arms race. Proteases are amongst the many weapons employed by bacteria, which specifically cleave and neutralize key signalling molecules required for a coordinated immune response. In this article, we focus on a family of S8 subtilisin-like serine proteases expressed as cell-envelope proteases (CEPs) by group A and group B streptococci. Two of these proteases known as Streptococcus pyogenes CEP (SpyCEP) and C5a peptidase cleave the chemokine CXCL8 and the complement fragment C5a, respectively. Both CXCL8 and C5a are potent neutrophil-recruiting chemokines, and by neutralizing their activity, streptococci evade a key defence mechanism of innate immunity. We review the mechanisms by which CXCL8 and C5a recruit neutrophils and the characterization of SpyCEP and C5a peptidase, including both in vitro and in vivo studies. Recently described structural insights into the function of this CEP family are also discussed. We conclude by examining the progress of prototypic vaccines incorporating SpyCEP and C5a peptidase in their preparation. Since streptococci-producing SpyCEP and C5a peptidase are responsible for a considerable global disease burden, targeting these proteases by vaccination strategies or by small-molecule antagonists should provide protection from and promote the resolution of streptococcal infections.

The Role of Streptococcus spp. in Bovine Mastitis

The Streptococcus genus belongs to one of the major pathogen groups inducing bovine mastitis. In the dairy industry, mastitis is the most common and costly disease. It not only negatively impacts economic profit due to milk losses and therapy costs, but it is an important animal health and welfare issue as well. This review describes a classification, reservoirs, and frequencies of the most relevant Streptococcus species inducing bovine mastitis (S. agalactiae, S. dysgalactiae and S. uberis). Host and environmental factors influencing mastitis susceptibility and infection rates will be discussed, because it has been indicated that Streptococcus herd prevalence is much higher than mastitis rates. After infection, we report the sequence of cow immune reactions and differences in virulence factors of the main Streptococcus species. Different mastitis detection techniques together with possible conventional and alternative therapies are described. The standard approach treating streptococcal mastitis is the application of ß-lactam antibiotics. In streptococci, increased antimicrobial resistance rates were identified against enrofloxacin, tetracycline, and erythromycin. At the end, control and prevention measures will be considered, including vaccination, hygiene plan, and further interventions. It is the aim of this review to estimate the contribution and to provide detailed knowledge about the role of the Streptococcus genus in bovine mastitis.

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

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.

Multidrug Resistance and Molecular Characterization of Streptococcus agalactiae Isolates From Dairy Cattle With Mastitis

Streptococcus agalactiae is a pathogen-associated to bovine mastitis, a health disorder responsible for significant economic losses in the dairy industry. Antimicrobial therapy remains the main strategy for the control of this bacterium in dairy herds and human In order to get insight on molecular characteristics of S. agalactiae strains circulating among Argentinean cattle with mastitis, we received 1500 samples from 56 dairy farms between 2016 and 2019. We recovered 56 S. agalactiae isolates and characterized them in relation to serotypes, virulence genes, and antimicrobial susceptibility. Serotypes III and II were the most prevalent ones (46% and 41%, respectively), followed by Ia (7%). In relation to the 13 virulence genes screened in this study, the genes spb1, hylB, cylE, and PI-2b were present in all the isolates, meanwhile, bca, cpsA, and rib were detected in different frequencies, 36%, 96%, and 59%, respectively. On the other hand, bac, hvgA, lmb, PI-1, PI-2a, and scpB genes could not be detected in any of the isolates. Disk diffusion method against a panel of eight antimicrobial agents showed an important number of strains resistant simultaneously to five antibiotics. We also detected several resistance-encoding genes, tet(M), tet(O), ermB, aphA3, and lnu(B) (9%, 50%, 32%, 32%, and 5%, respectively). The results here presented are the first molecular data on S. agalactiae isolates causing bovine mastitis in Argentina and provide a foundation for the development of diagnostic, prophylactic, and therapeutic methods, including the perspective of a vaccine.

Molecular epidemiology, antimicrobial activity, and virulence gene clustering of Streptococcus agalactiae isolated from dairy cattle with mastitis in China

Streptococcus agalactiae is a contagious pathogen that causes bovine mastitis worldwide, resulting in considerable economic losses. In this study, we isolated 42 S. agalactiae strains in 379 milk samples from cows with subclinical mastitis on 15 dairy farms in 12 Chinese provinces. Analysis based on capsular typing and multilocus sequence typing, combined with patterns of virulence gene scanning and antimicrobial resistance, identified the lineages and populations of the isolates. We grouped the 42 isolates into 7 sequence types belonging to 6 clonal complexes, mainly CC103 (31/42 isolates; 73.8%). We identified an ST-23 strain named Sa 129 for the first time on Chinese dairy farms-this strain is usually associated with human isolates. Capsular types Ia and II were predominant in capsular typing. The prevalence of virulence profile 1 (bibA, cfb, cspA, cylE, fbsA, fbsB, hylB, and pavA) was 64.3%, and represented the main trend in China. With respect to antimicrobial resistance, most isolates were susceptible to β-lactams, rifamycin, glycopeptides, and oxazolidone; resistance to several antimicrobial agents, including lincomycin, clindamycin, and doxycycline, varied in 4 different regions. Our research provides a profile for the molecular epidemiology, multilocus sequence typing, antimicrobial resistance, and virulence gene clustering of S. agalactiae, and may be beneficial for the clinical monitoring, prevention, and control of mastitis in dairy cattle.

Analysis of virulence factors and antibiotic resistance genes in group B streptococcus from clinical samples

BACKGROUND

Streptococcus agalacticae (Group B Streptococcus, GBS) is one of the most important causative agents of serious infections among neonates. This study was carried out to identify antibiotic resistance and virulence genes associated with GBS isolated from pregnant women.

METHODS

A total of 43 GBS isolates were obtained from 420 vaginal samples collected from HIV positive and negative women who were 13-35 weeks pregnant attending Antenatal Care at Chitungwiza and Harare Central Hospitals in Zimbabwe. Identification tests of GBS isolates was done using standard bacteriological methods and molecular identification testing. Antibiotic susceptibility testing was done using the modified Kirby-Bauer method and E-test strips. The boiling method was used to extract DNA and Polymerase Chain Reaction (PCR) was used to screen for 13 genes. Data was fed into SPSS 24.0.

RESULTS

Nine distinct virulence gene profiles were identified and hly-scpB-bca-rib 37.2% (16/43) was common. The virulence genes identified were namely hly 97.8% (42/43), scpB 90.1% (39/43), bca 86.0% (37/43), rib 69.8% (30/43) and bac 11.6% (5/43). High resistance to tetracycline 97.7% (42/43) was reported followed by 72.1% (31/43) cefazolin, 69.8% (30/43) penicillin G, 58.1% (25/43) ampicillin, 55.8% (24/43) clindamycin, 46.5% (20/43) ceftriaxone, 34.9% (15/43) chloramphenicol, and 30.2% (13/43) for both erythromycin and vancomycin using disk diffusion. Antibiotic resistance genes among the resistant and intermediate-resistant isolates showed high frequencies for tetM 97.6% (41/42) and low frequencies for ermB 34.5% (10/29), ermTR 10.3% (3/29), mefA 3.4% (1/29), tetO 2.4% (1/42) and linB 0% (0/35). The atr housekeeping gene yielded 100% (43/43) positive results, whilst the mobile genetic element IS1548 yielded 9.3% (4/43).

CONCLUSION

The study showed high prevalence of hly, scpB, bca and rib virulence genes in S. agalactiae strains isolated from pregnant women. Tetracycline resistance was predominantly caused by the tetM gene, whilst macrolide resistance was predominantly due to the presence of erm methylase, with the ermB gene being more prevalent. Multi-drug resistance coupled with the recovery of resistant isolates to antimicrobial agents such as penicillins indicates the importance of GBS surveillance and susceptibility tests. It was also observed that in vitro phenotypic resistance is not always accurately predicted by resistance genotypes.

Comparison of Streptococcus agalactiae Isolates from Humans and Companion Animals Reveals Genotypic and Phenotypic Differences

This study assessed whether Streptococcus agalactiae isolates from companion animals differed from those of human origin. Beta-hemolytic S. agalactiae was collected from a veterinary laboratory center and a university hospital. Strains were identified using 16S rRNA amplicon sequencing and amplification of the species-specific dltS gene. We conducted virulence gene profiling, capsular genotyping, determination of clonal complex (CC), and antimicrobial resistance (AMR) phenotyping or genotyping. The 20 non-invasive isolates obtained from animals and 15 non-invasive isolates from adult humans were comparatively analyzed in this study. We found significant differences in the virulence gene profiles of bca-rib-lmb-cylE (40.0% vs. 93.3%) and the possession of bac (30.0% vs. 0%) between animal-origin and human-origin non-invasive strains. We observed a significant difference in the distribution of CC1 between the two non-invasive populations. There were significant differences in the prevalence of tetracycline resistance genotypes (60.0% vs. 20.0%) and absence of AMR genotypes (30.0% vs. 80.0%), and AMR rates of tetracycline (35.0% vs. 0%) and fluoroquinolone (20.0% vs. 66.7%) between the two non-invasive populations. These observations suggest that there were different features, in terms of virulence gene profile, CC, and AMR genotype/phenotype in the non-invasive isolates of animal origin compared to those of human origin.

Multiomics analyses reveal that NOD-like signaling pathway plays an important role against Streptococcus agalactiae in the spleen of tilapia

Streptococcus aglactiae(GBS) infection in tilapia is a serious global disease that causes significant production loss. Here, we studied the role of GBS in the spleen and the spleen's response against the pathogen through dual RNA-seq and proteome technology. Animals were divided into three groups: control, virulent treated (HN016), and attenuated treated (YM001). Spleen samples were collected and analysis when a disease outbreak. Dual RNA-seq result showed the virulence factor genes of GBS, included CAMP factor, PGK, OCT, enolase, scpB, Sip, bca, were upregulation. downregulation of GapA, cylE, OCT, scpB, C5AP, rlmB, hly, FBP, in HN016 and YM001. But for proteomic, OCT and bca were downregulation, the others were upregulation. For host transcriptome KEGG analysis showed, the NOD-like receptor signaling pathway (NLRs) and TOLL-like receptor signaling pathway (TLRs) were upreguoation in HN016 infected fish than the control fish; But for proteome KEGG, only the NLRS was up, the TLRS was not change. Compared with YM001 infected fishes, for transcriptome, NLRs and TLRs in infected HN016 fishes were significance rise (p < 0.01); for proteome, the NLRs was up (p < 0.05), but TLRs was no change.Analysis of pathogen-host interaction showed that the peptidoglycan (PNG), CD2, LCK, and host's Zap70 were involved in the regulation of NLRs; PNG, LCK, and ZAP70 were involved in the regulation of TRLs. Conclusion: the virulent strain HN016 and attenuated strainYM001 differed in the quantity of virulence factors. In tilapia's innate immune system, NLRs was the main defense factors, but bacteria avoided the host defense through TLRs.

Phenotypic and genetic differences among group B Streptococcus recovered from neonates and pregnant women in Shenzhen, China: 8-year study

BACKGROUND

Group B Streptococcus (GBS) is a leading cause of early-onset disease (EOD) and late-onset disease (LOD) in infants. We sought to investigate the antibiotic susceptibility profiles, resistance genes, virulence-related genes, serotype distribution and genotypic characteristics of GBS recovered from infected or colonized neonates and pregnant women in a tertiary teaching hospital in Shenzhen, China, from 2008 to 2015.

RESULTS

High resistance rates of erythromycin (66.7-100%) were detected among early-onset GBS (EOGBS), late-onset GBS (LOGBS), neonatal colonizing GBS (NCGBS) and maternal colonizing GBS (MCGBS). 89.5-100% of four groups of GBS isolates showed resistance to tetracycline. More than 90 % of erythromycin resistant isolates of EOGBS (8/8, 100%), LOGBS (16/17, 94.1%) and NCGBS (10/11, 90.9%) harbored ermB, while only 9.1-17.6% harbored mefA/E. By contrast, 55.8% (24/43) and 62.8% (27/43) of erythromycin resistant MCGBS isolates carried ermB and mefA/E genes, respectively. The tetO gene was more common in tetracycline resistant EOGBS (10/11, 90.9%), LOGBS (17/17, 100%) and NCGBS (10/11, 90.9%), compared to tetracycline resistant MCGBS (12/51, 23.5%). Additionally, the tetM gene accounted for 90.9% (10/11), 76.5% (13/17), 45.5% (5/11) and 80.4% (41/51) of four groups of isolates, respectively. Serotype III was the most predominant in EOGBS (8/12, 66.7%) and LOGBS (15/17, 88.2%), while serotype Ib accounted for 50.0% (6/12) of NCGBS, and serotype Ia and III accounted for 45.6% (26/57) and 33.3% (19/57) of MCGBS, respectively. Sequence type 17 (ST17) was the most common in EOGBS (6/12, 50%) and LOGBS (12/17, 70.6%), while ST12 was predominant in NCGBS (5/12, 41.7%), and five STs (ST19, ST23, ST12, ST103 and ST485) accounted for 66.7% (38/57) of the MCGBS. All serotype III-ST17 isolates recovered from neonates were associated with invasive infections.

CONCLUSIONS

This study shows the meaningful differences in molecular mechanisms of resistance to erythromycin and tetracycline, and the prevalence of serotypes and STs among GBS recovered from neonates and pregnant women. ST17 is predominant in neonatal invasive GBS, but rare in NCGBS and MCGBS.

Phenotypic and genetic differences among group B Streptococcus recovered from neonates and pregnant women in Shenzhen, China: 8-year study

Background

Group B Streptococcus (GBS) is a leading cause of early-onset disease (EOD) and late-onset disease (LOD) in infants. We sought to investigate the antibiotic susceptibility profiles, resistance genes, virulence-related genes, serotype distribution and genotypic characteristics of GBS recovered from infected or colonized neonates and pregnant women in a tertiary teaching hospital in Shenzhen, China, from 2008 to 2015.

Results

High resistance rates of erythromycin (66.7–100%) were detected among early-onset GBS (EOGBS), late-onset GBS (LOGBS), neonatal colonizing GBS (NCGBS) and maternal colonizing GBS (MCGBS). 89.5–100% of four groups of GBS isolates showed resistance to tetracycline. More than 90 % of erythromycin resistant isolates of EOGBS (8/8, 100%), LOGBS (16/17, 94.1%) and NCGBS (10/11, 90.9%) harbored ermB, while only 9.1–17.6% harbored mefA/E. By contrast, 55.8% (24/43) and 62.8% (27/43) of erythromycin resistant MCGBS isolates carried ermB and mefA/E genes, respectively. The tetO gene was more common in tetracycline resistant EOGBS (10/11, 90.9%), LOGBS (17/17, 100%) and NCGBS (10/11, 90.9%), compared to tetracycline resistant MCGBS (12/51, 23.5%). Additionally, the tetM gene accounted for 90.9% (10/11), 76.5% (13/17), 45.5% (5/11) and 80.4% (41/51) of four groups of isolates, respectively. Serotype III was the most predominant in EOGBS (8/12, 66.7%) and LOGBS (15/17, 88.2%), while serotype Ib accounted for 50.0% (6/12) of NCGBS, and serotype Ia and III accounted for 45.6% (26/57) and 33.3% (19/57) of MCGBS, respectively. Sequence type 17 (ST17) was the most common in EOGBS (6/12, 50%) and LOGBS (12/17, 70.6%), while ST12 was predominant in NCGBS (5/12, 41.7%), and five STs (ST19, ST23, ST12, ST103 and ST485) accounted for 66.7% (38/57) of the MCGBS. All serotype III-ST17 isolates recovered from neonates were associated with invasive infections.

Conclusions

This study shows the meaningful differences in molecular mechanisms of resistance to erythromycin and tetracycline, and the prevalence of serotypes and STs among GBS recovered from neonates and pregnant women. ST17 is predominant in neonatal invasive GBS, but rare in NCGBS and MCGBS.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1551-2) contains supplementary material, which is available to authorized users.

Phylogenetic, comparative genomic and structural analyses of human Streptococcus agalactiae ST485 in China

Background

Streptococcus agalactiae (Group B Streptococcus, GBS) is a common bacteria species infecting both human and bovine. Previous studies have shown that the GBS isolated from human and bovine are mostly unrelated and belong to separate populations. However, recently, the bovine GBS CC103 has become the dominant epidemic strain and frequently isolated from human patients. In particular, the ST485 GBS, a member of CC103, has become the new dominant ST in China and exhibited very high pathogenicity. This phenomenon is not consistent with the established understanding about the relationship between bovine and human GBS, which needs to be re-investigated.

Results

The genome-based phylogenetic analysis showed that the human and bovine GBS CC103 strains had very close genetic relationship and they were alternately distributed on the evolutionary tree. CC103 strains evolved into several branches, including the ST485, which exhibited high pathogenicity and specifically infected human. Compared to other CC103 strains, the ST485 lacked Lac.2 gene structure and acquired the CadDX gene structure in their genomes.

Conclusions

Our results indicate that GBS CC103 could propagate across human and bovine, and GBS ST485 might evolve from the ST103 that could infect both human and bovine. Moreover, the recombination of Lac.2 and CadDX gene structures might play an important role in the formation of highly pathogenic ST485 in China.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5084-0) contains supplementary material, which is available to authorized users.

Characterization of virulence factors, antimicrobial resistance pattern and clonal complexes of group B streptococci isolated from neonates

Between January and December 2013, swab samples were taken for the throat and external ear canals of 1037 newborns for screening of Group B Streptococcus (GBS or S. agalactiae). Isolates were analyzed form Multilocus sequence typing (MLST), capsular type, virulence genes and antibiotic susceptibility. The MLST analysis of 19 GBS isolates showed 8 sequence types (STs). Overall the most common STs were ST19 and ST28. Other STs were ST1, ST4, ST8, ST12, ST335 and ST734 (a new ST). The most common clonal complexes (CCs) were CC19 (68.4%) and CC10 (21%). The scpB, hlyB and bca virulence genes were detected in all ST_S, while the bac gene was predominant in ST12 with capsular type (CT) Ib. The IS1548 and the rib genes were particularly prevalent in CTIII and were detected in isolates belong to ST19, ST335 and ST734 and were grouped in CC19. All isolates were susceptible to penicillin, vancomycin, linezolid and quinupristin-dalfopristin. Resistance to tetracycline was observed in all 19 (100%) strains and was correlated with presence of the tetM gene except for one isolate with ST12. All the ST8 and ST12 isolates were resistant to macrolide carrying two resistance genes; the ermTR and the ermB, respectively. The results of this study showed that the CC19 was a major clone in the neonatal intensive care unit (NICU) of Imam Khomeini hospital which can cause severe infections in susceptible neonates (particularly in premature infants). As a result, an intensive infection control policy is needed to prevent the spread of this clone.