Lactococcosis in fish has been associated with Lactococcus garvieae and the recently described L. petauri. However, the relevance of these emerging fish pathogens to Nile tilapia still requires ...thorough understanding. This study investigated lactococcosis outbreaks in Nile tilapia on Brazilian farms and characterized the isolates through multilocus sequence typing (MLST), virulence to Nile tilapia, and antimicrobial susceptibility. Lactococcosis outbreaks were monitored from 2019 to 2022 throughout Brazil. The outbreaks occurred mainly during warmer months, and co-infections were observed in four farms, whereas concurrent bacterial infections were identified in all farms. Since the sequence of the 16S rRNA was not capable of differentiating between L. petauri and L. garvieae, Lactococcus spp. isolates were identified at the species level using the gyrB gene sequence. In total, 30 isolates were classified as L. petauri and two as L. garvieae. According to the MLST, all L. petauri isolates were grouped in the sequence type (ST) 24, except for one isolate which belonged to the newly described ST47. A new ST was also described for the L. garvieae isolates identified, ST46. The L. petauri ST24 and ST47 were characterized as singletons, whereas L. garvieae ST46 was grouped with ST16 and ST17 and formed CC17. For the challenge trial, an L. petauri ST24 isolate was chosen considering that this MLST lineage was the most frequently observed. Fish were challenged by intraperitoneal injection and different bacterial doses were used (106 to 102 CFU per fish). The infection in the challenged fish progressed very rapidly, and within 48 h post-challenge clinical signs and the first mortalities were observed. The pathogenicity of L. petauri to Nile tilapia was confirmed. The estimated LD50 was 5.74 × 103 CFU 15 days post-challenge. Provisional epidemiological cutoff values were determined for L. petauri for six antimicrobial agents from different drug classes. All isolates were characterized as wild type (WT) for neomycin and oxytetracycline, whereas 96.67% of the isolates were characterized as WT for amoxicillin, erythromycin, and florfenicol, and 83.33% were WT for norfloxacin. The L. petauri ST24 was observed in different regions of the country, illustrating a rapid expansion of this bacterial lineage.
•Lactococcus petauri is pathogenic to Nile tilapia.•L. petauri was implicated in most lactococcosis outbreaks in tilapia in Brazil.•The most frequent and spread MLST lineage was L. petauri ST24.•The gyrB sequence allowed for the differentiation of L. petauri and L. garvieae.
Based on beneficial effects of Lactococcus spp. and their extracellular polysaccharides on common carp (Cyprinus carpio L.) in previous studies, the main purpose of this paper was to investigate the ...functions of single or multi-strains of Lactococcus spp. on the growth performance, glucose absorption and metabolism of common carp. The results showed that when the fish consumed diets containing single (Lactococcus lactis Q-8, L. lactis Q-9, L. lactis Z-2) or multi-strains of Lactococcus spp. (5 × 108 CFU g−1 of feed) for 60 days, the final weight, weight gain (WG), specific growth rate (SGR) and condition factor (CF) had significantly (P < .05) increased, especially in the multi-strains addition groups. While the feed conversion ratio (FCR) of all Lactococcus spp. addition groups was significantly lower than that in the control group (P < .05). Viscera-somatic index (VSI) and survival rate in each experimental group was no significant difference during the feeding period (P > .05). For the glucose absorption, Lactococcus spp. addition groups significantly increased the blood glucose concentration and up-regulated the expression of Sglt1 and Gult2 in intestine compared with the control group (P < .05). In addition, the contents of hepatopancreas glycogen were also significantly increased in the Lactococcus spp. addition groups (P < .05). For the glucose metabolism in hepatopancreatic, the Lactococcus spp. addition groups significantly decreased the expression of GK and PK in glycolysis (P < .05), while increased the G6Pase and PEPCK expression in gluconeogenesis (P < .05). Furthermore, with the prolongation of feeding time, the synergistic effects on the expression levels of absorption and metabolism related genes, and the glycogen content were better in the multi-strains addition groups. Overall, these results suggested that the Lactococcus spp. improved the growth performance, and exerted glucose absorption and metabolism effects in common carp, which provide a theoretical basis for the rational use of potential probiotics and carbohydrate in aquaculture.
•Common carps were fed diets containing single or multi-strains of Lactococcus spp.•Fish fed with Lactococcus spp. had enhanced glucose absorption and glycogen content.•Lactococcus spp. significantly improved the growth performance of common carp.•Lactococcus spp. regulated the glucose absorption and metabolism of common carp.•Multi-strains of Lactococcus spp. have synergistic effect on glucose metabolism.
Introduction: Authentic kefir originates from the Caucasus mountains of Eastern Europe and is a fermented milk product made from kefir grains. Authentic kefir contains lactic acid bacteria, acetic ...acid bacteria and yeasts which provides kefir with numerous health benefits such as anticarcinogenic, antimutagenic and anti-allergic properties. Nigella sativa is a plant known by many regional names such as black cumin and black carraway. Seeds from the plant are processed to produce black seed oil. Black seed oil has many potential health benefits such as antibacterial and antifungal capabilities. In countries including Turkey and India, black seed oil is commonly added to kefir or yogurt. The purpose of this study was to determine if different concentrations of black seed oil would negatively impact beneficial kefir microorganisms when consumers mix black seed oil into kefir. Results: Black seed oil concentrations of 0%, 0.1%, 1% and 5% were added to milk with kefir grains and incubated. Each mixture was tested for pH, Lactobacillus spp., Lactococcus spp., yeast, and coliform microbial counts. Results indicated that the pH and microbial counts of the control (0%) and 0.1% black seed oil samples were not significantly different (P > 0.05). The pH and microbial count results of 1% black seed oil in kefir indicated slight although not significant inhibition (P > 0.05) as compared to the control and 0.1% black seed oil. The pH and microbial counts of 5% black seed oil were significantly different (P < 0.05) from the other samples indicating inhibition of the kefir microorganisms.Conclusion:Black seed oil inhibited kefir microorganism when added at the rate of 5%.Keywords: Kefir, Black Seed Oil, Lactobacillus spp., Lactococcus spp., Yeast, Probiotic
Lactococcus lactis ssp. lactis isolated from raw milk was used for titanium dioxide (TiO2) nanoparticles biosynthesis. Biosynthesized TiO2 nanoparticles were characterized using UV-vis spectroscopy, ...Atomic Force Microscopy (AFM) (1.97 nm), X-ray diffraction (XRD) appa-ratus, Field Emission Scanning Electron Microscopy (FE-SEM), Energy dispersive X-ray anal-ysis (EDX) spectra and Fourier Transform Infrared Spectroscopy (FTIR). Result was 408.21 cm-1 that belong to anatase Titania. L. lactis ssp. Lactis isolates had the ability to synthesize TiO2 nanoparticles, the characterization results presented that the biosynthesized nanoparti-cles were at wavelength (344-347) nm; approving the formation of anatase phase of TiO2 NPs; spherical crystals, with particles, average diameter of 47.22 nm.
Karish cheese is one of the most popular, oldest cheese varieties in Egypt and Arab countries. As a low fat cheese; it is a promising food in particularly for old people and whom suffering from ...obesity related diseases. The objective of this work was to isolate, identify and select Lactococcus lactic acid bacteria (LAB) from traditional Karish cheese to conserve and enhance the characteristics of conventional Karish cheese made of pasteurized milk to meet the new regulations for dairy production. Two Lactococcus strains were selected out of 11 Lactococcus LAB isolates from 15 Karish cheese samples, phenotypically and technologically characterized then identified using genotypic 16S rRNA approach. The two unique strains; L. lactis subsp cremoris (KM746) and the exopolysaccharide (EPS) producing strain L. lactis subsp lactis (KM721) were applied as single starter cultures in comparison with commercial starter culture used in Karish cheese making. Selected LAB showed decent growth throughout processing and storage at 4 °C for 10 days preventing growth of coliform and staphylococci. Chemical composition of tested cheese samples was similar to the conventional Karish cheese, whilst rheological and sensorial properties were enhanced which encourage recommending these strains as starter cultures conserving and enhancing this type of traditional cheese.
•Isolation of new Lactococcus LAB from traditional Egyptian Karish cheese.•Technological characterization nominated selection of two Lactococci strains.•Molecular identification of the strains using 16srRNA approach.•Remarkable impact on organolyptic and texture properties was shown.•The Lactococci strains are recommended for conventional Karish conservation.
The prevalence of lactic acid bacteria (LAB) and the effects of their antimicrobial peptides on H2 production in anaerobic fluidized bed reactors (AFBRs) operated with cheese whey (AFBR1 and AFBR2) ...were verified in this study. The AFBR1 received 5 g COD L−1 of cheese whey with decreasing hydraulic retention times (HRT) of 14 to 8 h. The AFBR2 was operated with 3–10 g COD L−1 of cheese whey with an HRT of 6 h. Next, 152 colonies were selected from de Man, Rogosa and Sharpe MRS agar plates, and 45 strains were classified as LAB. The counts oscillated between 6.6 and 8.1 log CFU mL−1, indicating that the LAB survived and persisted in the AFBRs. Pure cultures were identified using 16S rRNA gene sequencing, and Lactococcus lactis was the prevalent LAB (70%) in both reactors. The highest H2 yields (1.9 and 2.3 mol H2 mol lactose−1) were obtained during the first operational phase in both reactors when a low organic loading rate (OLR) was applied, and when the growth of Lactococcus spp. was associated with Leuconostoc pseudomesenteroides. The bacteriocin-producing LAB (mostly Lactobacillus spp.) found on the specific phases of reactors AFBR1 and AFBR2 exerted a remarkable influence on H2 yield.
•LAB survived and influenced H2 production in AFBRs fed with cheese whey.•Lactococcus spp. was the prevalent LAB in both AFBRs.•H2 yields of 1.9–2.3 mol/mol lactose were obtained in the absence of lactobacilli.•Bacteriocinogenic LAB strains were mainly found in phases with low H2 yield.
We investigated the distribution of pathogenic non-agalactiae gram-positive, catalase-negative cocci (GPCN) in a convenience sample of New York State dairy farms. Our primary objective with the ...clinical mastitis (CM) GPCN samples was to evaluate somatic cell count (SCC) resolution and bacteriological cure of Streptococcus dysgalactiae or Streptococcus uberis versus Lactococcus lactis or Lactococcus garvieae in cows that received an approved intramammary treatment. In phase I, we assessed the distribution of the GPCN and SCC resolution. In phase II, we evaluated the SCC resolution and bacteriological cure in CM samples from the 4 farms with the highest prevalence of L. lactis or L. garvieae in phase I. In phase I, 8,868 CM and subclinical mastitis (SCM) milk samples were received from 143 farms. The GPCN samples identified by culture were confirmed with MALDI-TOF. From the 473 MALDI-TOF-confirmed GPCN samples, 155 were S. dysgalactiae (33%); 150, S. uberis (32%); 112, L. lactis (24%); 16, L. garvieae (3%); and 40, other GPCN (8%). From these, 277 were CM samples and 127 were eligible for the evaluation of SCC resolution, which was defined as SCC ≤200,000 cells/mL in a composite sample 15 to 60 d post-diagnosis. The odds of SCC resolution in CM samples was evaluated with multivariable logistic regression, and the odds were 6.1 95% confidence interval (CI):2.7–13.9 times higher for S. dysgalactiae or S. uberis compared with L. lactis or L. garvieae. In phase II, a total of 1,662 CM and SCM samples were evaluated with microbiological methods as in phase I, of which 211 samples were confirmed by MALDI-TOF: 39% were S. dysgalactiae (n = 61) and S. uberis (n = 21); 55%, L. lactis (n = 114) and L. garvieae (n = 2); and 6%, other GPCN (n = 13). In total, 168 CM samples were eligible for analysis and 118 were included in the final SCC resolution model. Similar statistical methods as in phase I were performed, and the odds of SCC resolution were 2.4 (95% CI: 1.1–5.5) times higher for S. dysgalactiae or S. uberis compared with L. lactis or L. garvieae. Bacteriological cure was defined as having a different or negative culture on a quarter sample taken 14 to 28 d after initial diagnosis. The odds of bacteriological cure (n = 121) were 8.0 (95% CI: 2.5–25.6) times higher for S. dysgalactiae or S. uberis compared with L. lactis or L. garvieae. Differences in SCC resolution and bacteriological cure between these groups may dictate a different management approach.
Probiotics have been used for over a century to prevent and treat diseases. They can reduce the effects of gastroenteritis and are now used to treat acute diarrhea. This study aimed to evaluate the ...co-aggregative effects of probiotics bacteria against diarrheal causative bacteria. For this purpose, 11 isolates of probiotic bacteria were used in the current study, including three
, one
, two
, three
, and two
isolates. All isolates were tested for antibiotic susceptibility, autoaggregation ability, adhesion ability, antibacterial activity, acid tolerance, and bile salts tolerance. The results showed that most of them had the ability to autoaggregate after 4 h, with the highest percentage of 57.14% for
. For the antibiotic susceptibility test, all the isolates showed resistance against trimethoprim/sulfamethoxazole, except one isolate. Moreover, all the isolates, except one, were susceptible to both vancomycin and tetracycline. All tested isolates had adhesion ability with different survival rates, which reached 34.57% for
in acidic conditions. Besides, the highest survival rate was 85.17%, which belonged to
, for bile salt tolerance. Probiotic isolates had an antibacterial effect against diarrhea-causative bacteria with an inhibition diameter of 17-49 mm for different
spp. and
spp. isolates. Furthermore, the co-aggregation ability of probiotic isolates against diarrhea-causative bacteria was studied, and results showed that probiotic isolates had a co-aggregative effect against diarrhea-causative bacteria,
,
, and
, after 24 h of incubation. The highest co-aggregative effect of probiotics isolates belonged to
and
against
with a co-aggregation percentage of 100%, while the lowest co-aggregation rate was 14.29% against
. The findings revealed the probiotic properties and co-aggregative effects of probiotic bacteria against diarrhea-causative bacteria.
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