The Effect of Pasteurized Milk Extracellular vesicles on Bacterial Growth : [poster]

Milk-derived extracellular vesicles (mEVs) have gained attention for their potential biological activities, including antibacterial properties and they can carry bioactive molecules. The mEVs can survive high temperatures and digestion processes while retaining their biological activity. Studies of mammalian EVs are increasingly attracting the interest of researchers; however, there are only a few studies of mEVs’ antimicrobial effect.Poster of the Conference COMBIVET & OH-BOOST 2023, Tartu, Estonia, 8-9 th of September, 2023.This research was partially supported by the Estonian Research Council grant PRG 1441.This research was partially supported by the Estonian Research Council grant PRG 1441

A simple, rapid typing method for Streptococcus agalactiae based on ribosomal subunit proteins by MALDI-TOF MS

Streptococcus agalactiae (Group B Streptococcus, GBS), is a frequent human colonizer and a leading cause of neonatal meningitis as well as an emerging pathogen in non-pregnant adults. GBS possesses a broad animal host spectrum, and recent studies proved atypical GBS genotypes can cause human invasive diseases through animal sources as food-borne zoonotic infections. We applied a MALDI-TOF MS typing method, based on molecular weight variations of predefined 28 ribosomal subunit proteins (rsp) to classify GBS strains of varying serotypes into major phylogenetic lineages. A total of 249 GBS isolates of representative and varying capsular serotypes from patients and animal food sources (fish and pig) collected during 2016-2018 in Hong Kong were analysed. Over 84% (143/171) noninvasive carriage GBS strains from patients were readily typed into 5 globally dominant rsp-profiles. Among GBS strains from food animals, over 90% (57/63) of fish and 13% (2/15) of pig GBS matched with existing rsp-profiles, while the remainder were classified into two novel rsp-profiles and we failed to assign a fish strain into any cluster. MALDI-TOF MS allowed for high-throughput screening and simultaneous detection of novel, so far not well described GBS genotypes. The method shown here is rapid, simple, readily transferable and adapted for use in a diagnostic microbiology laboratory with potential for the surveillance of emerging GBS genotypes with zoonotic potential

The effect of pasteurized milk extracellular vesicles on bacterial growth

Extracellular vesicles (EVs) are released by cells and have a lipid bilayer structure. EVs harbor various molecules, including proteins, RNAs, and DNAs. Studies of mammalian EVs are increasingly attracting the interest of researchers; however, there are only few studies of nanoparticles in food. Milk-derived EVs can survive high temperatures and digestion process, while retaining their biological activity. This study investigated the effect of pasteurized cows’ milk derived EVs on growth of five different bacteria. Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 53868, Bacillus subtilis, Bacillus cereus and Pseudomonas aeruginosa with a concentration of 1x107 CFU/ml were separately co-cultured with pasteurized milk derived EVs (1x109 EVs/μl) in Muller Hinton broth. The bacterial growth was monitored as absorbance at 620 nm over 24 hours. Bacteria treated with phosphate buffer solution (PBS) were considered negative control throughout the experiment. The percentage bacterial growth difference was COMBIVET & OH-BOOST JOINT CONFERENCE 2023 55 determined with respect to negative control and results expressed as mean ± standard error of mean. All analyses were performed in three biological triplicates and each biological replicate consisted of three technical replicates. Co-culture of bacteria with milk EVs demonstrated that EVs could decrease the growth of S. aureus, B. subtilis, B. cereus and P. aeruginosa. Highest growth inhibition was observed for B. subtilis (33.9% ± 2.4) followed by B. cereus (18.1% ± 3.7) at 6 hours of incubation. S. aureus and P. aeruginosa growth were inhibited by 12.9% ± 1.3 and 9.9% ± 3.5 respectively after 9 hours incubation. Only the S. aureus growth inhibition at 9 hours was statistically significant (P=0.022) according to T-test. However, E. coli growth was not affected by milk EVs compared to the control. In conclusion, the dietary EVs can be absorbed by bacteria and pasteurized milk derived EVs has a selective inhibitory activity on the growth of some bacteria

Correction: Li et al. Multidrug-Resistant Streptococcus agalactiae Strains Found in Human and Fish with High Penicillin and Cefotaxime Non-Susceptibilities. Microorganisms 2020, 8, 1055

The authors would like to make the following correction to the published paper [...

Prevalence and Characteristics of <i>Streptococcus agalactiae</i> from Freshwater Fish and Pork in Hong Kong Wet Markets

We report the antimicrobial resistance of 191 fish and 61 pork Group B Streptococcus (GBS) procured from Hong Kong wet markets. Two-hundred-and-fifty-two GBS strains were isolated from 992 freshwater fish and 361 pig offal during 2016–2019. The strains were isolated from homogenised samples and plated on selective media, followed by identification through MALDI-TOF-MS. Molecular characterisation, an antibiotic susceptibility test, and biofilm formation were performed on the strains. The isolation rates of the fish GBS and pig GBS were 19.3% (191 strains from 992 freshwater fish) and 16.9% (61 strains from 361 pig organs), respectively. The fish GBS was predominantly serotype Ia, ST7, while pig GBS was serotype III, ST651 (45 strains). An antibiotic susceptibility test revealed that the fish GBS were mostly antibiotic-sensitive, while the pig GBS were multidrug-resistant. A biofilm formation experiment showed that over 71% of fish GBS and all pig GBS had moderate biofilm formation ability. In general, the prevalence rate of GBS in animals and the multidrug resistance phenotype presented in the strains raise concerns about its zoonotic potential and effects on public health

Colonization of Group B Streptococcus in Pregnant Women and Their Neonates from a Sri Lankan Hospital

We investigated the molecular epidemiology of Streptococcus agalactiae (Group B Streptococcus, GBS) from carriage in a cohort of pregnant mothers and their respective newborns in a Teaching Hospital in Sri Lanka. GBS vaginal carriage was assessed on pregnant mothers at pre-delivery (n = 250), post-delivery (n = 130), and from peri-rectal swabs of neonates (n = 159) in a prospective study. All colonizing, non-duplicate GBS isolates (n = 60) were analyzed for antimicrobial susceptibilities, capsular serotyping, and whole-genome sequencing (WGS). The percentage of GBS carriage in mothers in the pre-delivery and post-delivery cohorts were 11.2% (n = 28) and 19.2% (n = 25), respectively, and 4.4% (n = 7) in neonates. GBS isolates predominantly belonged to serotype VI (17/60, 28.3%). The isolates spanned across 12 sequence types (STs), with ST1 (24/60, 40%) being the most predominant ST. Concomitant resistance to erythromycin, tetracyclines, and gentamicin was observed in eight strains (13.3%). WGS revealed the presence of antimicrobial resistance genes including ermA (5/60), mefA (1/60), msrD (1/60), and tetLMO (2/60, 28/60, and 1/60, respectively) among 60 strains. The study provides insight into the diversity of vaccine targets of GBS since serotype VI is yet to be covered in the vaccine development program