Prevalence, multidrug resistance, and biofilm formation of Vibrio parahaemolyticus isolated from fish mariculture environments in Cat Ba Island, Vietnam.

BACKGROUND: Vibrio parahaemolyticus is a major foodborne pathogen in aquatic animals and a threat to human health worldwide. This study investigated the prevalence, antimicrobial resistance, antimicrobial resistance genes (ARGs), and biofilm formation of V. parahaemolyticus strains isolated from fish mariculture environments in Cat Ba Island, Vietnam. METHODS: In total, 150 rearing water samples were collected from 10 fish mariculture farms in winter and summer. A polymerase chain reaction assay was used to identify V. parahaemolyticus, its virulence factors, and ARGs. The antimicrobial resistance patterns and biofilm formation ability of V. parahaemolyticus strains were investigated using the disk diffusion test and a microtiter plate-based crystal violet method, respectively. RESULTS: Thirty-seven V. parahaemolyticus isolates were recovered from 150 samples. The frequencies of the tdh and trh genes among V. parahaemolyticus isolates were 8.1% and 21.6%, respectively. More than 90% of isolates were susceptible to ceftazidime, cefotaxime, and chloramphenicol, but over 72% were resistant to ampicillin, tetracycline, and erythromycin. Furthermore, 67.57% of isolates exhibited multidrug resistance. The presence of ARGs related to gentamicin (aac(3)-IV), tetracycline (tetA) and ciprofloxacin (qnrA) in V. parahaemolyticus isolates was identified. Conversely, no ARGs related to ampicillin or erythromycin resistance were detected. Biofilm formation capacity was detected in significantly more multidrug-resistant isolates (64.9%) than non-multidrug-resistant isolates (18.9%). CONCLUSION: Mariculture environments are a potential source of antibiotic-resistant V. parahaemolyticus and a hotspot for virulence genes and ARGs diffusing to aquatic environments. Thus, the prevention of antibiotic-resistant foodborne vibriosis in aquatic animals and humans requires continuous monitoring.

First study on capsular serotypes and virulence factors of Pasteurella multocida isolates from Phan Rang sheep in Vietnam.

Background and Aim: Pasteurella multocida is considered as a main factor mediating pneumonic pasteurellosis in ruminants, including sheep. It is also a current threat to Phan Rang sheep in Vietnam. This study aimed to characterize P. multocida isolated from Phan Rang sheep, their antibiotic resistance profile, and the prevalence of some virulence-associated genes of these strains. Materials and Methods: Bacteria were isolated on brain heart infusion, 10% sheep blood agar plates, and screened by biochemical tests. The polymerase chain reaction technique was used with specific primers to identify P. multocida, the presence of virulence-associated genes, and serotypes of isolates. Antimicrobial susceptibility and biofilm formation of isolates were examined using the disk diffusion method and crystal violet-based method, respectively. Results: A total of 41 P. multocida strains were isolated from 485 samples from clinically sick and healthy sheep. Of the isolates, 58.53% were serotype A, 9.75% were serotype B, and 31.71% were serotype D. Healthy animals were infected with serotype D only. All 15 virulence genes were identified in all strains isolated from clinically sick sheep, while strains isolated from healthy sheep carried 11/15 virulence genes tested. Among virulence-associated genes exbB, exbD, tonB, ompA, oma87, fimA, hgbA, and nanB were detected in over 90% of isolates, whereas hgbB, nanH, tbpA and pfhA were less frequent. Interestingly, pmHAS and tadD were highly prevalent in capsular type A strains, whereas the toxA gene was detected in capsular type D strains only. All of the isolated strains were fully susceptible to enrofloxacin, ciprofloxacin, neomycin, and ofloxacin. About 92.68% were susceptible to chloramphenicol and 90.24% to amikacin, but there was high resistance to erythromycin, tetracycline, and amoxicillin. Our results reveal that 53.65% of 41 isolates could produce biofilm, whereas 46.34% could not. Conclusion: Pasteurella multocida from Phan Rang sheep possess many virulence genes and resistance to several common antibiotics such as erythromycin, tetracycline, and amoxicillin. The results are an important warning regarding antibiotic resistance of P. multocida.

Heavy Metal Tolerance of Novel Papiliotrema Yeast Isolated from Vietnamese Mangosteen.

Three yeast strains (Hue-1, Hue-8, and Hue-19) with strong heavy metal tolerance were isolated from mangosteen from Hue city, Vietnam. They exhibited identical phenotype and phylogeny. Sequence analysis of the D1/D2 region of the LSU rRNA gene and the internal transcribed spacer (ITS) region demonstrated that the closest relative of these strains is Papiliotrema sp. with 2.12% and 3.55-3.7% divergence in the D1/D2 domain, and ITS domain, respectively. Based on the physiological, biochemical, and molecular data, the three strains belong to a novel species of Papiliotrema genus, for which the name Papiliotrema huenov sp. nov. is proposed. These strains are highly tolerant of heavy metals compared to other yeasts, being able to grow in the presence of 2 mM Pb (II), 2 mM Cd (II), and up to 5 mM Ni (II), but no growth was observed in the presence of 1 mM As (III).

Versatile Functions of Caveolin-1 in Aging-related Diseases.

Caveolin-1 (Cav-1) is a trans-membrane protein that is a major component of the caveolae structure on the plasma membrane. Cav-1 is involved in the regulation of various cellular processes, including cell growth, differentiation, endocytosis, and in particular it has been implied in cellular senescence. Here we review current knowledge about Cav-1 in cellular signaling and discuss the role of Cav-1 in aging-related diseases.

The role of TLR9 in stress-dependent autophagy formation.

Autophagy is a self-degradation process that is important for balancing energy sources at critical times in development and in response to nutrient stress. Recently, it was report that autophagy is controlled by recognizing conserved pattern recognition receptors (PRRs), including toll-like receptors (TLRs). However, the molecular mechanism of TLRs in autophagy is not well understood. In this study, we found that serum starvation-dependent autophagy was associated with TLR9 activation in the absence of CpG-ODN, which is a specific TLR9 ligand. TLR9 was not only elevated but also colocalized with LC3 during autophagy by serum starvation or CPG-ODN treatment; however, these events did not occur simultaneously during autophagosome accumulation. Autophagy was even induced upon TLR9 activation after inhibiting recruitment of initial autophagy components by 3-MA, a specific inhibitor of class III PI3-kinase. Our data suggested that TLR9 may be promptly induced and recruit autophagy components from the endosome to autophagosome in response to stress.

Direct Regulation of TLR5 Expression by Caveolin-1.

Toll-like receptor 5 (TLR5) is a specific receptor for microbial flagellin and is one of the most well-known receptors in the TLR family. We reported previously that TLR5 signaling is well maintained during aging and that caveolin-1 may be involved in TLR5 signaling in aged macrophages through direct interactions. Therefore, it is important to clarify whether caveolin-1/TLR5 interactions affect TLR5 expression during aging. To assess the effect of caveolin-1 on TLR5, we analyzed TLR5 expression in senescent fibroblasts and aged tissues expressing high levels of caveolin-1. As expected, TLR5 mRNA and protein expression was well maintained in senescent fibroblasts and aged tissues, whereas TLR4 mRNA and protein were diminished in those cells and tissues. To determine the mechanism of caveolin-1-dependent TLR5 expression, we examined TLR5 expression in caveolin-1 deficient mice. Interestingly, TLR5 mRNA and protein levels were decreased dramatically in tissues from caveolin-1 knockout mice. Moreover, overexpressed caveolin-1 in vitro enhanced TLR5 mRNA through the MAPK pathway and prolonged TLR5 protein half-life through direct interaction. These results suggest that caveolin-1 may play a crucial role in maintaining of TLR5 by regulating transcription systems and increasing protein half-life.

Flagellin-dependent TLR5/caveolin-1 as a promising immune activator in immunosenescence.

The age-associated decline of immune responses causes high susceptibility to infections and reduced vaccine efficacy in the elderly. However, the mechanisms underlying age-related deficits are unclear. Here, we found that the expression and signaling of flagellin (FlaB)-dependent Toll-like receptor 5 (TLR5), unlike the other TLRs, were well maintained in old macrophages, similar to young macrophages. The expression and activation of TLR5/MyD88, but not TLR4, were sensitively regulated by the upregulation of caveolin-1 in old macrophages through direct interaction. This interaction was also confirmed using macrophages from caveolin-1 or MyD88 knockout mice. Because TLR5 and caveolin-1 were well expressed in major old tissues including lung, skin, intestine, and spleen, we analyzed in vivo immune responses via a vaccine platform with FlaB as a mucosal adjuvant for the pneumococcal surface protein A (PspA) against Streptococcus pneumoniae infection in young and aged mice. The FlaB-PspA fusion protein induced a significantly higher level of PspA-specific IgG and IgA responses and demonstrated a high protective efficacy against a lethal challenge with live S. pneumoniae in aged mice. These results suggest that caveolin-1/TLR5 signaling plays a key role in age-associated innate immune responses and that FlaB-PspA stimulation of TLR5 may be a new strategy for a mucosal vaccine adjuvant against pneumococcal infection in the elderly.

Selective transfection with osmotically active sorbitol modified PEI nanoparticles for enhanced anti-cancer gene therapy.

Polysorbitol-mediated transporter (PSMT) has been previously shown to achieve high transfection efficiency with minimal cytotoxicity. Polysorbitol backbone possesses osmotic properties and leads to enhanced cellular uptake. The PSMT/pDNA nanoparticles were prepared and the particle size, surface charge of the nanoparticles was determined for the study. PSMT delivers genes into cells by the caveolae mediated endocytic pathway. Caveolae expression is usually altered in transformed cancer cells. Transfection through the caveolae may help PSMT to selectively transfect cancer cells rather than normal cells. Transfection of the luciferase gene by PSMT was tested in various cell types including cancer cell lines, primary cells, and immortalized cells. Luciferase transgene expression mediated by PSMT was remarkably increased in HeLa cells compared to expression using the control carrier Lipofectamine. Moreover, the toxicity of PSMT was comparable to the control carrier (Lipofectamine) in the same cells. Selective transfection of cancer cells using PSMT was further confirmed by co-culture of cancer and normal cells, which showed that transgene expression was pre-dominantly achieved in cancer cells. A functional p53 gene was also delivered into HeLa cells using PSMT and the selective transgene expression of p53 protein in cancer cells was analyzed through western blotting and confocal microscopy. HeLa cells transfected with PSMT/p53 plasmid nanoparticles showed cellular damage and apoptosis, which was confirmed through propidium iodide staining.