Susceptibility to Nisin, Bactofencin, Pediocin and Reuterin of Multidrug Resistant Staphylococcus aureus, Streptococcus dysgalactiae and Streptococcus uberis Causing Bovine Mastitis

Antibiotics are the most effective strategy to prevent and treat intramammary infections. However, their misuse has led to the dissemination of multidrug resistant bacteria (MDR) for both animals and humans. Efforts to develop new alternative strategies to control bacterial infections related to MDR are continuously on the rise. The objective of this study was to evaluate the antimicrobial activity of different bacteriocins and reuterin against MDR Staphylococcus and Streptococcus clinical isolates involved in bovine mastitis. A bacterial collection including S. aureus (n = 19), S. dysgalactiae (n = 17) and S. uberis (n = 19) was assembled for this study. Antibiotic resistance profiles were determined by the disk diffusion method. In addition, sensitivity to bacteriocins and reuterin was evaluated by determining minimum inhibitory concentrations (MIC). A total of 21 strains (37.5%) were MDR. MICs ranged from ≤1.0 μg/mL to ≥100 μg/mL for nisin and 2.0 to ≥250 μg/mL for bactofencin. Reuterin was active against all tested bacteria, and MICs vary between 70 and 560 μg/mL. Interestingly, 20 MDR strains were inhibited by bactofencin at a concentration of ≤250 μg/mL, while 14 were inhibited by nisin at an MIC of ≤100 μg/mL. Pediocin did not show an inhibitory effect.

Effect on Intermediary Metabolism and Digestive Parameters of the High Substitution of Fishmeal with Insect Meal in Sparus aurata Feed

Hermetia illucens and Tenebrio molitor were tested on account of their potential to replace fish protein in feed. Two levels of replacement for H. illucens, 30% and 50% (H30 and H50), and one for T. molitor, 50% (T50), as well as an additional diet with a modified fatty acid fraction (H50M), were investigated in relation to juvenile Sparus aurata growth indices, enzyme activities and gut microbiome. A T50 diet showed similar results to a control (C) diet, with no significant differences regarding morphological indices and minor differences for nutritional indices. Regarding the gut microbiome, H50M was the diet which showed the more similar prokaryotic community to C, which suggests that fatty acid fractions might influence the composition of the gut microbiome. Nevertheless, differences appeared to be related to a redistribution of dominant species, while changes in species affiliation were limited to minoritary species. The positive correlation between some of these minoritary species (Peptostreptococcus russellii, Streptococcus dysgalactiae and Weisella confusa) and several fish growth parameters might explain differences between control and insect diets. Deciphering such uncertainty and revealing the potential role these unusual species may play on fish performance should be addressed in future investigations.

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

Streptococcus dysgalactiae subsp. dysgalactiae (SDSD) is one of the most prevalent pathogens causing bovine mastitis worldwide. However, there is a lack of comprehensive information regarding genetic diversity, complete profiles of virulence factors (VFs), and antimicrobial resistance (AMR) genes for SDSD associated with bovine mastitis in China. In this study, a total of 674 milk samples, including samples from 509 clinical and 165 subclinical mastitis cases, were collected from 17 herds in 7 provinces in China from November 2016 to June 2019. All SDSD isolates were included in phylogenetic analysis based on 16S rRNA and multi-locus sequence typing (MLST). In addition, whole genome sequencing was performed on 12 representative SDSD isolates to screen for VFs and AMR genes and to define pan-, core and accessory genomes. The prevalence of SDSD from mastitis milk samples was 7.57% (51/674). According to phylogenetic analysis based on 16S rRNA, 51 SDSD isolates were divided into 4 clusters, whereas based on MLST, 51 SDSD isolates were identified as 11 sequence types, including 6 registered STs and 5 novel STs (ST521, ST523, ST526, ST527, ST529) that belonged to 2 distinct clonal complexes (CCs) and 4 singletons. Based on WGS information, 108 VFs genes in 12 isolates were determined in 11 categories. In addition, 23 AMR genes were identified in 11 categories. Pan-, core and accessory genomes were composed of 2,663, 1,633 and 699 genes, respectively. These results provided a comprehensive profiles of SDSD virulence and resistance genes as well as phylogenetic relationships among mastitis associated SDSD in North China.

Isolation and characterization of bacteriophages from wastewater sources on Enterococcus spp. isolated from clinical samples

Background and Objectives: In recent decades, enterococcal resistance to antimicrobials has greatly increased. Further- more, these chemicals include several side effects on the patients. Since no reports are available of the bacteriophages' effects on eukaryotic cells, they can be good solutions for multidrug-resistant bacterial problems. Therefore, the major aim of this study was to isolate bacteriophages from wastewaters on clinical antibiotic-resistant enterococci. Materials and Methods: Clinical bacteria were isolated, then enterococcal isolates were identified using different methods. The antibiotic resistance scheme of the enterococcal isolates was assessed. The bacterial isolates were exposed to wastewa- ter samples containing potential bacteriophages. Technically, isolated bacteriophages were studied by electron microscopy. Results: Isolated bacteria were verified as Enterococcus faecium. Results showed that bacteriophages could easily be isolat- ed from wastewater sources. The isolated bacteriophages were effective on E. faecium as well as Streptococcus dysgalactiae. Furthermore, these bacteriophages were challenged with five other bacteria (ATCC) with no visible effects. In general, the isolated bacteriophages belonged to the Myoviridae, Siphoviridae, and Inoviridae families. Conclusion: Further studies on bacteriophages and their efficacy on enterococcal strains could increase the treatment possi- bility of enterococcal infections. Due to these bacteriophages' effects on Streptococcus strains, bacteriophages may be used to treat streptococcal infections as well.

Comprehensive comparative genomics analysis for the emerging human pathogen Streptococcus dysgalactiae subsp. equisimilis (SDSE): A case study and Pan-subspecies genomic analysis

Background: Streptococcus dysgalactiae subsp. equisimilis (SDSE) is the causal agent of various diseases that include wound infection, erysipelas, cellulitis, life-threatening necrotizing fasciitis, and streptococcal toxic shock syndrome. It is capable of infecting both humans and animals. In this investigation, we present a comprehensive genomic analysis for the SDSE strain SCDR1 that belongs to Lancefield group G, emm type (stG6) and (MLST) sequence type (ST44) that is the first time to be documented in Saudi Arabia and the middle east. Besides, we present the most comprehensive comparative genomics analysis for the emerging human pathogen SDSE. Methodology: We utilized next-generation sequencing techniques (NGS), bioinformatics, phylogenetic analysis, and comparative pathogenomics to characterize SCDR1 and all publicly available SDES genomes. Results: We found that SCDR1 consisted of a circular genome of 2179136 bp. Comparative analyses among bacterial genomes indicated that SCDR1 was most closely related to AC-2713 and GGS_124. Genome annotation of SCDR-1 strain showed that it contains many genes with homology to known virulence factors, including genes involved in cellular invasion, Antiphagocytosis, immune evasion, invasion of skin and soft tissue, host mortality and tissue damage, toxins, pore-forming proteins, cytotoxins, beta-hemolysis agents. Two CRISPR arrays were identified in SCDR1 that are consist of 35 CRISPR repeats and 33 CRISPR spacers. Two CAS systems were observed in the SCDR-1 genome, namely, CAS-TypeIIA and CAS-TypeIC. SDSE core Resistome is consisting of 22 genes, including folA, gyrA, gyrB, and FabK. SDSE core Virulome consisting of 38 genes including, fba, fbp54, gidA, and lsp. Conclusion: Our study confirmed that the SDSE strains possess different characteristics in producing virulence factors for pathogenicity to humans and based on its genome sequence and close relationship with GAS. Our study shed light on the proposed pathogenic mechanisms of SDSE and may form the basis of molecular epidemiological research on these highly virulent bacteria.

Rare complication of ceftriaxone therapy: drug-induced thrombocytopenia (DITP)

A 62-year-old woman with a history of end-stage renal disease on haemodialysis, essential hypertension and type 2 diabetes mellitus was diagnosed with sepsis and placed on 600 mg oral linezolid every 12 hours and 1 g intravenous ceftriaxone every 24 hours. Blood cultures grew Streptococcus dysgalactiae, and she was switched to intravenous ceftriaxone 2 g daily. Platelet counts slowly trended down after starting ceftriaxone reaching 5 K/μL on day 12 of treatment. Ceftriaxone was discontinued and heparin-induced thrombocytopaenia was ruled out. She was switched to vancomycin and her platelet count improved. Given the temporal relationship between changing platelet counts and starting and discontinuing ceftriaxone, a diagnosis of drug-induced thrombocytopaenia was made.