Hemolysin Activity Research Articles

Phenotypic, Molecular Identification and Virulence Assessment of Cronobacter spp Isolated from Clinical Samples of Children Under Two Years in Mosul City/Iraq

Cronobacter spp. is known to be a foodborne causative agent for a variety of diseases in both humans and animals. This study focused on isolating Cronobacter species from 150 clinical samples of children under two years (60 from blood and stool samples, 30 from CSF samples) collected from Ibn al Atheer and Al Khanssa Hospitals. The phenotypic identification of bacterial isolates were performed through culture, microscopic, and biochemical examinations and vitek-2 system. The results revealed a mixture of bacteria in 6.5% of the clinical specimens. The identity of isolates was 99% using the vitek-2 system for identifying Cronobacter sakazakii, Cronobacter malonaticus, Cronobacter muytjensii, and Cronobacter pulveris. Out of 150 specimens there were 8 (5.33 %) of specimens gave positive for Cronobacter spp which included: C. sakazaki 2/60 blood specimens (3.3%), C. sakazaki 2/60 stool specimens (3.3%), C. malonaticus 2/60 stool specimens (3.3%), 1/60 C. muytjensii and C. pulveris 1/60 (3.3%). The eight isolates phenotypically identified as Cronobacter were confirmed at the molecular level through 16S rRNA sequencing and submitted to NCBI under the accession numbers (OR825874, OR825875, PP126443, PP126444, PP126445, PP126455). The virulence profile of these isolates showed that 7/8 (87.5%) of Cronobacter strains exhibited haemolysin activity, 5/8 strains (62.5%) were able to produce the protease enzyme and 2/8 (25%) of Cronobacter strains were positive for lipase and lecithinase. All strains lacked the ability to produce a slime layer. The results also showed the ability of Cronobacter strains to produce biofilm by using the tube method and microtiter plate method but with different levels.

Comparing the frequency, antifungal susceptibility, and enzymatic profiles of the oral fungal composition in patients with and without Alzheimer's disease admitted to a neurology clinic.

Studies have shown that changes in the frequency of oral microorganisms may play a key role in the development of Alzheimer's disease (AD). However, no research has been conducted on the oral fungal composition in AD-patients. The present study aimed to investigate the changes in the frequency of oral fungal composition, the antifungal susceptibility, and the enzymatic profiles of oral fungal composition in patients suffering from AD compared to non-AD individuals. In the present analytical cross-sectional study during 12 months, 76 hospitalized patients with AD were matched with 76 individuals without AD. A sterile serum physiology-moistened cotton-tipped swab was used to sample the mouth area. All swabs were cultured on Sabouraud Chloramphenicol Agar. Fungal identified were confirmed through the PCR-sequencing techniques. Enzyme activity index (EAI) for important pathogenic factors including proteinase, esterase and hemolysin was measured using relevant protocols. The susceptibility to 8 antifungal agents (nystatin, voriconazole, itraconazole, fluconazole, posaconazole, amphotericin B, 5-fluorocytosine, and caspofungin) against fungal strains obtained from AD-patients was evaluated according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, document M38-A2 for filamentous fungi, and document M27-A4 for yeasts. The results showed that compared to the non-AD individuals, the prevalence of oral fungal composition in AD group was 1.6 times higher. Candida albicans was the most common fungal species isolated from oral swab samples of AD group (n=53, 80%) and non-AD group (n=28, 40%), and the diversity of the oral fungal composition in AD-patients were lower than non-AD individuals. Among the 3 investigated virulence factors, a statistically significant difference was shown in terms of hemolysin activity level between the two studied groups (p<0.05) and the activity level of esterase and proteinase enzymes did not show a significant difference in the two studied groups (p>0.05). The results showed that almost all of the tested isolates were susceptible to nystatin, the most widely prescribed antifungal to treat superficial infections, and only 1.69 % (2/118) of the Candida isolates were resistant to this antifungal drug. Understanding the changes in the frequency of oral fungal composition the antifungal susceptibility, and the enzymatic profiles of oral fungal composition in patients suffering from AD compared to non-AD individuals makes it possible to better understand the etiology of this disease.

Pathogenicity of Citrobacter freundii Causing Mass Mortalities of Macrobrachium rosenbergii and Its Induced Host Immune Response.

Citrobacter freundii is an opportunistic pathogen of freshwater aquatic animals, which severely restricts the sustainable development of the aquaculture industry. In this study, a dominant strain, named FSNM-1, was isolated from the hepatopancreas of diseased Macrobrachium rosenbergii. This strain was identified as C. freundii based on a comprehensive analysis of its morphological, physiological, and biochemical features and molecular identification. Challenge experiments were conducted to assess the pathogenicity of C. freundii to M. rosenbergii. The results showed that the FSNM-1 strain had high virulence to M. rosenbergii with a median lethal dose (LD50) of 1.1 × 106 CFU/mL. Histopathological analysis revealed that C. freundii infection caused different degrees of inflammation in the hepatopancreas, gills, and intestines of M. rosenbergii. The detection of virulence-related genes revealed that the FSNM-1 strain carried colonization factor antigen (cfa1, cfa2), ureases (ureG, ureF, ureD, ureE), and outer membrane protein (ompX), and virulence factor detection showed that the FSNM-1 strain had lecithinase, amylase, lipase, gelatinase, and hemolysin activities but did not produce protease and DNase activities. To investigate the immune response of M. rosenbergii to C. freundii, the expression levels of ALF3, MyD88, SOD, proPO, TRAF6, and TNF immune-related genes were monitored at different points of time in the hepatopancreas, gills, intestines, and hemocytes of M. rosenbergii after infection. The results demonstrated a significant upregulation in the expression levels of the ALF3, MyD88, SOD, proPO, TRAF6, and TNF genes in M. rosenbergii at the early stage of C. freundii infection. This study highlights C. freundii as a major pathogen causing mass mortality in M. rosenbergii and provides valuable insights into its virulence mechanisms and the host's immune response.

Discovery of β-nitrostyrene derivatives as potential quorum sensing inhibitors for biofilm inhibition and antivirulence factor therapeutics against Serratia marcescens.

Quorum sensing (QS) inhibition has emerged as a promising target for directed drug design, providing an appealing strategy for developing antimicrobials, particularly against infections caused by drug-resistant pathogens. In this study, we designed and synthesized a total of 33 β-nitrostyrene derivatives using 1-nitro-2-phenylethane (NPe) as the lead compound, to target the facultative anaerobic bacterial pathogen Serratia marcescens. The QS-inhibitory effects of these compounds were evaluated using S. marcescens NJ01 and the reporter strain Chromobacterium violaceum CV026. Among the 33 new β-nitrostyrene derivatives, (E)-1-methyl-4-(2-nitrovinyl)benzene (m-NPe, compound 28) was proven to be a potent inhibitor that reduced biofilm formation of S. marcescens NJ01 by 79%. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) results revealed that treatment with m-NPe (50 μg/ml) not only enhanced the susceptibility of the formed biofilms but also disrupted the architecture of biofilms by 84%. m-NPe (50 μg/ml) decreased virulence factors in S. marcescens NJ01, reducing the activity of protease, prodigiosin, and extracellular polysaccharide (EPS) by 36%, 72%, and 52%, respectively. In S. marcescens 4547, the activities of hemolysin and EPS were reduced by 28% and 40%, respectively, outperforming the positive control, vanillic acid (VAN). The study also found that the expression levels of QS- and biofilm-related genes (flhD, fimA, fimC, sodB, bsmB, pigA, pigC, and shlA) were downregulated by 1.21- to 2.32-fold. Molecular dynamics analysis showed that m-NPe could bind stably to SmaR, RhlI, RhlR, LasR, and CviR proteins in a 0.1 M sodium chloride solution. Importantly, a microscale thermophoresis (MST) test revealed that SmaR could be a target protein for the screening of a quorum sensing inhibitor (QSI) against S. marcescens. Overall, this study highlights the efficacy of m-NPe in suppressing the virulence factors of S. marcescens, identifying it as a new potential QSI and antibiofilm agent capable of restoring or improving antimicrobial drug sensitivity.

Phenotypic and genomic analysis of the hypervirulent methicillin-resistant Staphylococcus aureus ST630 clone in China.

Methicillin-resistant Staphylococcus aureus (MRSA) sequence type 630 (ST630) is a rarely reported lineage worldwide. This study aimed to trace the dissemination of the emerging MRSA ST630 clones in China and investigate their virulence potential. We collected 22 ST630-MRSA isolates from across China and performed whole-genome sequencing analysis and virulence characterization on these isolates. Epidemiological results showed that MRSA ST630 isolates were primarily isolated from pus/wound secretions, mainly originating from Jiangxi province, and carried diverse virulence and drug resistance genes. Staphylococcal cassette chromosome mec type V (SCCmec V) predominated (11/22, 50.0%) among the MRSA ST630 isolates. Interestingly, nearly half (45.5%) of the 22 ST630-MRSA isolates tested lacked intact SCCmec elements. Phylogenetic analysis demonstrated that ST630-MRSA could be divided into two distinct clades, with widespread dissemination mainly in Chinese regions. Five representative isolates were selected for phenotypic assays, including hemolysin activity, real-time fluorescence quantitative PCR, western blot analysis, hydrogen peroxide killing assay, blood killing assay, cell adhesion and invasion assay, and mouse skin abscess model. The results showed that, compared to the USA300-LAC strain, ST630 isolates exhibited particularly strong invasiveness and virulence in the aforementioned phenotypic assays. This study described the emergence of a highly virulent ST630-MRSA lineage and improved our insight into the molecular epidemiology of ST630 clones in China.IMPORTANCEMethicillin-resistant Staphylococcus aureus (MRSA) sequence type 630 (ST630) is an emerging clone with an increasing isolation rate in China. This study raises awareness of the hypervirulent MRSA ST630 clones in China and alerts people to their widespread dissemination. ST630-staphylococcal cassette chromosome mec V is a noteworthy clone in China, and we present the first comprehensive genetic and phenotypic analysis of this lineage. Our findings provide valuable insights for the prevention and control of infections caused by this emerging MRSA clone.

In vitro determination of antifungal susceptibility and virulence factors in Candida species causing candidemia in North India Region

Candidiasis is the most incessant fungal disease affecting human population worldwide. In this research work, we explored the characteristics contributing to pathogenicity of Candida infections, from serious bloodstream conditions like candidemia. Candida spp. were isolated from the blood of 120 suspected patients and assessed their susceptibility to antifungal treatments via MIC measurements. Enzyme activities (phospholipase, proteinase, hemolysin, and esterase) were examined alongside biofilm formation, with surface analysis conducted via SEM. Statistical analysis, facilitated by GraphPad Prism 8.4.2, identified correlations among data points. Results reveal that non-albicans spp. like Candida auris heightened resistance to antifungal treatments compared to Candida albicans. Candida tropicalis exhibited no phospholipase activity but shows activity to proteinase and esterase. Conversely, C. albicans show a case of elevated hemolysin activity. Non-albicans Candida i.e. C. tropicalis and Candida krusei were isolated as high biofilm formers in comparison to C. albicans. Statistical analysis yielded a highly significant p-value (< 0.001), affirming the robustness of our results. In conclusion, non-albicans species exhibit a broader spectrum of resistance mechanisms compared to C. albicans in pathogenicity. This investigation sheds light on diverse virulence strategies employed by different Candida species, informing future treatment approaches.

Enterococcus faecalis-derived adenine enhances enterohaemorrhagic Escherichia coli Type 3 Secretion System-dependent virulence.

Interactions between microbiota and enteric pathogens can promote colonization resistance or enhance pathogenesis. The pathobiont Enterococcus faecalis increases enterohaemorrhagic E. coli (EHEC) virulence by upregulating Type 3 Secretion System (T3SS) expression, effector translocation, and attaching and effacing (AE) lesion formation on enterocytes, but the mechanisms underlying this remain unknown. Using co-infection of organoids, metabolomics, supplementation experiments and bacterial genetics, here we show that co-culture of EHEC with E. faecalis increases the xanthine-hypoxanthine pathway activity and adenine biosynthesis. Adenine or E. faecalis promoted T3SS gene expression, while transcriptomics showed upregulation of adeP expression, which encodes an adenine importer. Mechanistically, adenine relieved High hemolysin activity (Hha)-dependent repression of T3SS gene expression in EHEC and promoted AE lesion formation in an AdeP-dependent manner. Microbiota-derived purines, such as adenine, support multiple beneficial host responses; however, our data show that this metabolite also increases EHEC virulence, highlighting the complexity of pathogen-microbiota-host interactions in the gut.

Comparative analysis of enzymatic profiles and biofilm formation in clinical and environmental Candida kefyr isolates

AbstractThe global landscape of Candida infections has seen a significant shift. Previously, Candida albicans was the predominant species. However, there has been an emergence of non‐albicans Candida species, which are often less susceptible to antifungal treatment. Candida kefyr, in particular, has been increasingly associated with infections. This study aimed to investigate the profiles of enzymatic activity and biofilm formation in both clinical and non‐clinical isolates of C. kefyr. A total of 66 C. kefyr isolates were analysed. The activities of proteinase and phospholipase were assessed using bovine serum albumin and egg yolk agar, respectively. Haemolysin, caseinolytic and esterase activities were evaluated using specific methods. Biofilm formation was investigated using crystal violet staining. The findings indicated that biofilm and proteinase activity were detected in 81.8% and 93.9% of all the isolates, respectively. Haemolysin activity was observed with the highest occurrence (95.5%) among normal microbiota isolates. Esterase activity was predominantly identified in dairy samples and was absent in hospital samples. Caseinase production was found with the highest occurrence (18.2%) in normal microbiota and hospital samples. Phospholipase activity was limited, found in only 3% of all the isolates. These findings reveal variations in enzyme activity between clinical and non‐clinical C. kefyr isolates. This sheds light on their pathogenic potential and has implications for therapeutic strategies.

Marine Pediococcus pentosaceus E3 Probiotic Properties, Whole-Genome Sequence Analysis, and Safety Assessment

Probiotics play a significant role in enhancing health, and they are well known for bacteriocins production. Evaluating probiotics’ whole-genome sequence provides insights into their consumption outcomes. Thus, genomic studies have a significant role in assessing the safety of probiotics more in-depth and offer valuable information regarding probiotics’ functional diversity, metabolic pathways, and health-promoting mechanisms. Marine Pediococcus pentosaceus E3, isolated from shrimp gut, exhibited beneficial properties, indicating its potential as a probiotic candidate. Phenotypically, E3 strain was susceptible to most antibiotics assessed, tolerant to low pH and high bile salt conditions, and revealed no hemolysin activity. Interestingly, E3-neutralized CFS revealed significant antibacterial activity against pathogens under investigation. Therefore, the concentrated CFS was prepared and evaluated as a natural biopreservative and showed outstanding antimicrobial activity. Furthermore, integrated-based genome assessment has provided insight into probiotic characteristics at the genomic level. Whole-genome sequencing analysis revealed that the E3 genome possesses 1805 protein-coding genes, and the genome size was about 1.8 Mb with a G + C content of 37.28%. Moreover, the genome revealed the absence of virulence factors and clinically related antibiotic genes. Moreover, several genes consistent with probiotic microorganisms’ features were estimated in the genome, including stress response, carbohydrate metabolism, and vitamin biosynthesis. In addition, several genes associated with survival and colonization within the gastrointestinal tract were also detected across the E3 genome. Therefore, the findings suggest that insights into the genetic characteristics of E3 guarantee the safety of the strain and facilitate future development of E3 isolate as a health-promoting probiotic and source of biopreservative.

Miconazole and phenothiazine hinder the quorum sensing regulated virulence in Pseudomonas aeruginosa

Antibiotic resistance is a major health problem worldwide. Pseudomonas aeruginosa is a Gram-negative pathogen with an arsenal of virulence factors and elevated antimicrobial resistance. It is a leading cause of nosocomial infections with high morbidity and mortality. The significant time and effort required to develop new antibiotics can be circumvented using alternative therapeutic strategies, including anti-virulence targets. This study aimed to investigate the anti-virulence activity of the FDA-approved drugs miconazole and phenothiazine against P. aeruginosa. The phenotypic effect of sub-inhibitory concentrations of miconazole and phenothiazine on biofilm, pyocyanin, protease, rhamnolipid and hemolysin activities in PAO1 strain was examined. qRT-PCR was used to assess the effect of drugs on quorum-sensing genes that regulate virulence. Further, the anti-virulence potential of miconazole and phenothiazine was evaluated in silico and in vivo. Miconazole showed significant inhibition of Pseudomonas virulence by reducing biofilm-formation approximately 45–48%, hemolytic-activity by 59%, pyocyanin-production by 47–49%, rhamnolipid-activity by approximately 42–47% and protease activity by 36–40%. While, phenothiazine showed lower anti-virulence activity, it inhibited biofilm (31–35%), pyocyanin (37–39%), protease (32–40%), rhamnolipid (35–40%) and hemolytic activity (47–56%). Similarly, there was significantly reduced expression of RhlR, PqsR, LasI and LasR following treatment with miconazole, but less so with phenothiazine. In-silico analysis revealed that miconazole had higher binding affinity than phenothiazine to LasR, RhlR, and PqsR QS-proteins. Furthermore, there was 100% survival in mice injected with PAO1 treated with miconazole. In conclusion, miconazole and phenothiazine are promising anti-virulence agents for P. aeruginosa.

Assessment of species distribution and virulence factors of oral fungal carriage among hospitalized patients with COVID-19: a case-control study.

The COVID-19 pandemic highlighted the need to study oral fungal carriage and its potential impact. In oral fungal environments, factors like changes in respiratory epithelium, increased pathogen attachment, local inflammation, and virulence factors could influence COVID-19 severity. The authors conducted a study to explore oral fungal carriage in COVID-19 patients and compare it to a healthy control group. The authors executed a case-control investigation including 144 COVID-19 patients and an equivalent number of 144 healthy controls. The matching criteria encompassed age, sex, body mass index, and the history of antibiotic and antiviral medication intake. This research was performed over a span of 12 months from May 2021 to May 2022. The mouth area was sampled with a cotton-tipped swab. Subsequently, all the samples underwent fungal culture and PCR-sequencing procedures. In COVID-19 patients, oral fungal carriage was three times higher compared to healthy controls. Candida was the exclusive genus found in both groups, with Candida albicans being the most frequently isolated species (90.79%). Among COVID-19 patients, Candida species showed significantly higher esterase, proteinase, and hemolysin activity compared to healthy individuals. Both groups exhibited elevated levels of C. albicans virulence factors compared to non-albicans species. It is crucial to understand the way that virulence factors of oral fungal carriage act in COVID-19 patients in order to come up with novel antifungal medications, identify the contributing factors to drug resistance, and manage clinical outcomes.

Bacillus velezensis iturins inhibit the hemolytic activity of Staphylococcus aureus

Bovine mastitis caused by S. aureus has a major economic impact on the dairy sector. With the crucial need for new therapies, anti-virulence strategies have gained attention as alternatives to antibiotics. Here we aimed to identify novel compounds that inhibit the production/activity of hemolysins, a virulence factor of S. aureus associated with mastitis severity. We screened Bacillus strains obtained from diverse sources for compounds showing anti-hemolytic activity. Our results demonstrate that lipopeptides produced by Bacillus spp. completely prevented the hemolytic activity of S. aureus at certain concentrations. Following purification, both iturins, fengycins, and surfactins were able to reduce hemolysis caused by S. aureus, with iturins showing the highest anti-hemolytic activity (up to 76% reduction). The lipopeptides showed an effect at the post-translational level. Molecular docking simulations demonstrated that these compounds can bind to hemolysin, possibly interfering with enzyme action. Lastly, molecular dynamics analysis indicated general stability of important residues for hemolysin activity as well as the presence of hydrogen bonds between iturins and these residues, with longevous interactions. Our data reveals, for the first time, an anti-hemolytic activity of lipopeptides and highlights the potential application of iturins as an anti-virulence therapy to control bovine mastitis caused by S. aureus.

Comparative Genome Analysis and Characterization of the Probiotic Properties of Lactic Acid Bacteria Isolated from the Gastrointestinal Tract of Wild Boars in the Czech Republic.

Probiotics are crucial components for maintaining a healthy gut microbiota in pigs, especially during the weaning period. Lactic acid bacteria (LAB) derived from the gastrointestinal tract of wild boars can serve as an abundant source of beneficial probiotic strains with suitable properties for use in pig husbandry. In this study, we analyzed and characterized 15strains of Limosilactobacillusmucosae obtained from the gut contents of wild boars to assess their safety and suitability as probiotic candidates. The strains were compared using pan-genomic analysis with 49 L.mucosae strains obtained from the NCBI database. All isolated strains demonstrated their safety by showing an absence of transferrable antimicrobial resistance genes and hemolysin activity. Based on the presence of beneficial genes, five candidates with probiotic properties were selected and subjected to phenotypic profiling. These five selected isolates exhibited the ability to survive conditions mimicking passage through the host's digestive tract, such as low pH and the presence of bile salts. Furthermore, five selected strains demonstrated the presence of corresponding carbohydrate-active enzymes and the ability to utilize various carbohydrate substrates. These strains can enhance the digestibility of oligosaccharide or polysaccharide substrates found in food or feed, specifically resistant starch, α-galactosides, cellobiose, gentiobiose, and arabinoxylans. Based on the results obtained, the L.mucosae isolates tested in this study appear to be promising candidates for use as probiotics in pigs.

Exploring the anti-biofilm activity and Suppression of virulence genes expression by thanatin in Listeria monocytogenes

Listeria monocytogenes is a common foodborne pathogen causing severe listeriosis, with a mortality rate of 20–30%. This pathogen spreads through biofilm formation in the food industry. Antimicrobial peptides are widely used in food preservation to combat harmful pathogens. Thanatin, a 21-amino acid peptide from Podisus maculiventris, combats various pathogens effectively. This study aimed to evaluate the antimicrobial efficacy of thanatin peptide against L. monocytogenes ATCC 19115. The minimum inhibitory concentration (MIC) of thanatin against L. monocytogenes was determined to be 17 μg/mL. Analysis using a scanning electron microscope (SEM) confirmed its antibacterial efficacy. Thanatin treatment inhibited swimming motility, biofilm formation, auto-aggregation, cytotoxicity, hemolysin activity, adhesion, and host cell invasion by L. monocytogenes. Concentrations ranging from 1/16MIC (27%) to MIC (92%) effectively prevented biofilm formation, and existing biofilms experienced significant reduction (9.41%–80.66%) after thanatin treatment. Moreover, the thanatin peptide exhibited significant cytotoxic effects on Caco-2 cancer cells (IC50 = 27.04 μg/mL) and decreased the hemolytic activity of L. monocytogenes (2.66%–7.33%). Additionally, thanatin effectively suppressed the expression of virulence genes in L. monocytogenes, decreasing its pathogenicity. In summary, thanatin peptide exhibits beneficial antibacterial effects, suggesting its potential as a natural bacteriostatic agent for further research and practical implementation.

Antivirulence Effects of Trans-Resveratrol and Curcumin on Methicillin-Resistant Staphylococcus aureus (MRSA) from Saudi Arabia.

Methicillin-resistant Staphylococcus aureus (MRSA) is a common resistant bacterium, whose resistance has expanded to commonly used antibiotics. It is crucial to create novel treatments to tackle bacterial resistance. Trans-resveratrol and curcumin are naturally occurring phenolic compounds, whose effects on MRSA virulence are the subject of this investigation. Sub-MICs of trans-resveratrol and curcumin were tested on the virulence factors of 50 MRSA clinical isolates (CIs), including biofilm, hemolysin, hemagglutination, protease, and lecithinase. The distribution of the virulence factors of the CIs was as follows: hemolysin: 98%, hemagglutination: 70%, protease: 62%, biofilm: 56%, and lecithinase: 52%. The sub-MIC that could reduce the effect of the tested virulence factors by 50% or more (IC50) was observed in the strains that showed susceptibility to the individual administration of trans-resveratrol at 50 µg/mL and curcumin at 20 µg/mL. Hemagglutination and hemolysin activity were inhibited by at least 50% in the majority of CIs (57-94%). Meanwhile, the IC50 for protease and biofilm was observed in 6.5-17.8% of the CIs. A few of the CIs were susceptible to lecithinase inhibition, but all showed a full inhibition. This research supports the possibility of the use of these compounds to reduce the bacterial virulence that can reduce antibiotic utilization, and eventually, they can become a potential alternative treatment in combating bacterial resistance.

An Investigation of Quorum Sensing Inhibitors against Bacillus cereus in The Endophytic Fungus Pithomyces sacchari of the Laurencia sp.

Bacillus cereus, a common food-borne pathogen, forms biofilms and generates virulence factors through a quorum sensing (QS) mechanism. In this study, six compounds (dankasterone A, demethylincisterol A3, zinnimidine, cyclo-(L-Val-L-Pro), cyclo-(L-Ile-L-Pro), and cyclo-(L-Leu-L-Pro)) were isolated from the endophytic fungus Pithomyces sacchari of the Laurencia sp. in the South China Sea. Among them, demethylincisterol A3, a sterol derivative, exhibited strong QS inhibitory activity against B. cereus. The QS inhibitory activity of demethylincisterol A3 was evaluated through experiments. The minimum inhibitory concentration (MIC) of demethylincisterol A3 against B. cereus was 6.25 μg/mL. At sub-MIC concentrations, it significantly decreased biofilm formation, hindered mobility, and diminished the production of protease and hemolysin activity. Moreover, RT-qPCR results demonstrated that demethylincisterol A3 markedly inhibited the expression of QS-related genes (plcR and papR) in B. cereus. The exposure to demethylincisterol A3 resulted in the downregulation of genes (comER, tasA, rpoN, sinR, codY, nheA, hblD, and cytK) associated with biofilm formation, mobility, and virulence factors. Hence, demethylincisterol A3 is a potentially effective compound in the pipeline of innovative antimicrobial therapies.

First Report of the Emerging Pathogen Kodamaea ohmeri in Honduras.

Kodamaea ohmeri is an environmental yeast considered a rare emerging pathogen. In clinical settings, the correct identification of this yeast is relevant because some isolates are associated with resistance to antifungals. There is a lack of available data regarding the geographical distribution, virulence, and drug resistance profile of K. ohmeri. To contribute to the knowledge of this yeast, this study aimed to describe in depth three isolates of K. ohmeri associated with fungemia in Honduras. The identification of the isolates was carried out by sequencing the ribosomal ITS region. In addition, the susceptibility profile to antifungals was determined, and some properties associated with virulence were evaluated (exoenzyme production, biofilm formation, cell adhesion, and invasion). The isolates showed strong protease, phospholipase, and hemolysin activity, in addition to being biofilm producers. Adherence and invasion capacity were evident in the HeLa and Raw 264.7 cell lines, respectively. This study expands the understanding of the underlying biological traits associated with virulence in K. ohmeri, and it is the first report of the detection and identification of K. ohmeri in Honduras as a cause of human infection.

Biotechnological Potential and Safety Evaluation of Dextran- and Riboflavin-Producing Weisella cibaria Strains for Gluten-Free Baking.

Gluten consumption causes several immunological and non-immunological intolerances in susceptible individuals. In this study, the dextran-producing Weissella cibaria BAL3C-5 and its derivative, the riboflavin-overproducing strain BAL3C-5 C120T, together with a commercial bakery yeast, were used to ferment gluten-free (GF)-doughs obtained from corn and rice flours at two different concentrations and supplemented with either quinoa, buckwheat, or chickpea to obtain laboratory-scale GF bread. The levels of dextran, riboflavin, and total flavins were determined in the fermented and breads. Both strains grew in fermented doughs and contributed dextran, especially to those made with corn plus quinoa (~1 g/100 g). The highest riboflavin (350-150 µg/100 g) and total flavin (2.3-1.75 mg/100 g) levels were observed with BAL3C-5 C120T, though some differences were detected between the various doughs or breads, suggesting an impact of the type of flour used. The safety assessment confirmed the lack of pathogenic factors in the bacterial strains, such as hemolysin and gelatinase activity, as well as the genetic determinants for biogenic amine production. Some intrinsic resistance to antibiotics, including vancomycin and kanamycin, was found. These results indicated the microbiological safety of both W. cibaria strains and indicated their potential application in baking to produce GF bread.

Investigating the effect of Lactiplantibacillus plantarum TW57-4 in preventing biofilm formation and expression of virulence genes in Listeria monocytogenes ATCC 19115

Listeria monocytogenes is a common foodborne pathogen associated with listeriosis, a severe illness with a mortality rate of 20–30%. This study aimed to assess the antimicrobial properties of Lactiplantibacillus plantarum TW57-4 cell-free supernatant (CFS) against L. monocytogenes ATCC 19115. The CFS exhibited a minimum inhibitory concentration (MIC) of 31.24 mg/mL against L. monocytogenes. Scanning electron microscopy confirmed its anti-biofilm effects. The impact of CFS on various aspects of L. monocytogenes, such as biofilm formation, auto-aggregation, cytotoxicity, hemolysin activity, adhesion, and invasion, was also investigated. CFS treatment effectively inhibited biofilm formation at concentrations ranging from 1/16MIC (9.67%) to MIC (80%). It also reduced preexisting biofilms by 4.2%–70.91%. The CFS demonstrated cytotoxic effects on Caco-2 cancer cells (IC50, 44.64 mg/mL) and diminished hemolytic activity of L. monocytogenes at concentrations from MIC to 1/4 MIC, with reduction percentages of 50.66% and 28.66% respectively. Moreover, CFS treatment suppressed the expression of virulence genes, inhibiting the pathogenicity of L. monocytogenes. In conclusion, Lpb. plantarum TW57-4 exhibits favorable probiotic properties, antibacterial effects, and holds potential as a natural bacteriostatic agent. Further research and practical applications are warranted. It also shows promise as a bio-intervention for controlling L. monocytogenes biofilm in the food industry.

Evaluation of exoenzyme profiles of Candida albicans species isolated from females with vaginal candidiasis.

The three most common causes of vaginitis are bacteria, yeast, and Protozoa. Candida albicans is one of the most common causes of vaginitis and commonly affects millions of females with different signs and symptoms. Secretion of exoenzymes from Candida species plays an important role in virulence and pathogenesis. Increasing our knowledge about the pathogenesis of candidiasis could help to design new anti-Candida drugs. This study aimed to evaluate the phospholipase, esterase, and hemolysin activities of the vaginal Candida isolates and their correlation with the presence of vulvovaginal candidiasis. In total, 119 Candida albicans isolates from vaginal candidiasis were enrolled in the study. Egg yolk agar, Tween 80 opacity medium, and blood agar plate assays were used for the determination of phospholipase, esterase, and hemolytic activities, respectively. Based on the findings, 110 (92.44%) isolates showed phospholipase activity, 93 (78.2%) isolates were esterase producers, and 90 (75.6%) species had hemolytic activity. This study showed that most of the tested isolates had different enzymatic patterns. Discrimination of variations in the production of these exoenzymes among different Candida isolates may depend on Candida spp. pathogenicity and could be responsible for the severity of symptoms among the patients.