Browsing by Author "Palmer JS"

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    Biofilm formation, sodium hypochlorite susceptibility and genetic diversity of Vibrio parahaemolyticus
    (Elsevier BV, 2023-01-16) Wang D; Fletcher GC; On SLW; Palmer JS; Gagic D; Flint SH
    Vibrio parahaemolyticus is a marine oriented pathogen; and biofilm formation enables its survival and persistence on seafood processing plant, complicating the hygienic practice. The objectives of this study are to assess the ability of V. parahaemolyticus isolated from seafood related environments to form biofilms, to determine the effective sodium hypochlorite concentrations required to inactivate planktonic and biofilm cells, and to evaluate the genetic diversity required for strong biofilm formation. Among nine isolates, PFR30J09 and PFR34B02 isolates were identified as strong biofilm forming strains, with biofilm cell counts of 7.20, 7.08 log10 CFU/cm2, respectively, on stainless steel coupons after incubation at 25 °C. Free available chlorine of 1176 mg/L and 4704 mg/L was required to eliminate biofilm cells of 1.74-2.28 log10 CFU/cm2 and > 7 log10 CFU/cm2, respectively, whereas 63 mg/L for planktonic cells, indicating the ineffectiveness of sodium hypochlorite in eliminating V. parahaemolyticus biofilm cells at recommended concentration in the food industry. These strong biofilm-forming isolates produced more polysaccharides and were less susceptible to sodium hypochlorite, implying a possible correlation between polysaccharide production and sodium hypochlorite susceptibility. Genetic diversity in mshA, mshC and mshD contributed to the observed variation in biofilm formation between isolates. This study identified strong biofilm-forming V. parahaemolyticus strains of new multilocus sequence typing (MLST) types, showed a relationship between polysaccharide production and sodium hypochlorite resistance.
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    Comparative genome identification of accessory genes associated with strong biofilm formation in Vibrio parahaemolyticus.
    (Elsevier B.V., 2023-04-01) Wang D; Fletcher GC; Gagic D; On SLW; Palmer JS; Flint SH
    Vibrio parahaemolyticus biofilms on the seafood processing plant surfaces are a potential source of seafood contamination and subsequent food poisoning. Strains differ in their ability to form biofilm, but little is known about the genetic characteristics responsible for biofilm development. In this study, pangenome and comparative genome analysis of V. parahaemolyticus strains reveals genetic attributes and gene repertoire that contribute to robust biofilm formation. The study identified 136 accessory genes that were exclusively present in strong biofilm forming strains and these were functionally assigned to the Gene Ontology (GO) pathways of cellulose biosynthesis, rhamnose metabolic and catabolic processes, UDP-glucose processes and O antigen biosynthesis (p < 0.05). Strategies of CRISPR-Cas defence and MSHA pilus-led attachment were implicated via Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation. Higher levels of horizontal gene transfer (HGT) were inferred to confer more putatively novel properties on biofilm-forming V. parahaemolyticus. Furthermore, cellulose biosynthesis, a neglected potential virulence factor, was identified as being acquired from within the order Vibrionales. The cellulose synthase operons in V. parahaemolyticus were examined for their prevalence (22/138, 15.94 %) and were found to consist of the genes bcsG, bcsE, bcsQ, bcsA, bcsB, bcsZ, bcsC. This study provides insights into robust biofilm formation of V. parahaemolyticus at the genomic level and facilitates: identification of key attributes for robust biofilm formation, elucidation of biofilm formation mechanisms and development of potential targets for novel control strategies of persistent V. parahaemolyticus.
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    Efficacy of commercial peroxyacetic acid on Vibrio parahaemolyticus planktonic cells and biofilms on stainless steel and Greenshell™ mussel (Perna canaliculus) surfaces.
    (Elsevier B.V., 2023-11-16) Wang D; Palmer JS; Fletcher GC; On SLW; Gagic D; Flint SH
    The potential of using commercial peroxyacetic acid (PAA) for Vibrio parahaemolyticus sanitization was evaluated. Commercial PAA of 0.005 % (v/v, PAA: 2.24 mg/L, hydrogen peroxide: 11.79 mg/L) resulted in a planktonic cell reduction of >7.00 log10 CFU/mL when initial V. parahaemolyticus cells averaged 7.64 log10 CFU/mL. For cells on stainless steel coupons, treatment of 0.02 % PAA (v/v, PAA: 8.96 mg/L, hydrogen peroxide: 47.16 mg/L) achieved >5.00 log10 CFU/cm2 reductions in biofilm cells for eight strains but not for the two strongest biofilm formers. PAA of 0.05 % (v/v, PAA: 22.39 mg/L, hydrogen peroxide: 117.91 mg/L) was required to inactivate >5.00 log10 CFU/cm2 biofilm cells from mussel shell surfaces. The detection of PAA residues after biofilm treatment demonstrated that higher biofilm production resulted in higher PAA residues (p < 0.05), suggesting biofilm is acting as a barrier interfering with PAA diffusing into the matrices. Based on the comparative analysis of genomes, robust biofilm formation and metabolic heterogeneity within niches might have contributed to the variations in PAA resistance of V. parahaemolyticus biofilms.
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    Emetic toxin production of Bacillus cereus in a biofilm
    (Elsevier Ltd, 2022-01-15) Huang Y; Flint SH; Loo TS; Palmer JS
    Bacillus cereus sensu stricto (B. cereus) belongs to the B. cereus group, and is a well-known foodborne pathogen causing human disease including emesis which is caused by an emetic toxin, cereulide, with 105-108 cells per gram required to cause disease. The presence of this highly heat, pH and protease-resistant toxin presents a serious challenge to the food industry, as the bacteria itself may be eliminated during processing but the cereulide toxin will survive most food processing techniques. This study shows that cereulide toxin is associated with cells and biofilm structures rather than suspended in the surrounding liquid phase or environment. This is the first report investigating the cereulide toxin production in the presence of biofilms of B. cereus, showing that the cereulide toxin produced is associated with biofilm complex and also attaches to the substrate such as glass and stainless-steel on which the biofilm grows. The RT-qPCR showed that the expression of cesA and cesB were comparable between planktonic cells and biofilms. This study contributes a better understanding of food safety issues in the industry caused by cereulide toxin produced by B. cereus, and provides valuable information for developing control methods for cereulide toxin in the food industry.
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    Global expansion of Vibrio parahaemolyticus threatens the seafood industry: Perspective on controlling its biofilm formation
    (Elsevier Ltd, 2022-03-15) Wang D; Flint SH; Palmer JS; Gagic D; Fletcher GC; On SLW
    As global warming increases the geographical range and frequency of Vibrio parahaemolyticus infections, its formation of biofilms providing bacteria greater resistance to stress and contributing to the persistence of pathogens, is threatening the seafood industry. V. parahaemolyticus has a number of advantages leading to biofilm formation. This study reviews recent advances in understanding V. parahaemolyticus biofilm formation on biotic and abiotic surfaces, discusses research gaps in the mechanism of biofilm formation and examines promising biofilm control strategies to overcome current limitations of chemical disinfectant. This information will deepen our understanding of V. parahaemolyticus biofilm formation, as well as help design and optimize V. parahaemolyticus biofilm control strategies for the seafood industry.
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    Phenotypic properties and genotyping analysis of Bacillus cereus group isolates from dairy and potato products
    (Elsevier Ltd, 2021-04) Huang Y; Flint SH; Yu S; Ding Y; Palmer JS
    Bacillus cereus group (B. cereus sensu lato) are ubiquitously distributed in diverse environments. In this study, eight isolates including B. cereus, B. paranthracis and B. toyonensis species, from dairy and potato products, were assessed for biofilm formation, sporulation and genetic information including biofilm-related genes and toxin genes. The isolates varied in their ability to form biofilm (either at the stainless steel-liquid-air interface or floating pellicles). The amounts of biofilms of B. cereus s.l., were increased when incubated in agitation condition varied between isolates. Sporulation within the planktonic and biofilm modes of growth was compared, suggesting that biofilm is a favourable environment for B. cereus s.l. to form spores. Whole genome sequencing (WGS) was used to compare these B. cereus s.l. isolates. New sequence types (STs) of B. cereus were found in this study. Isolates that shared similar genomes had different biofilm-forming and sporulation abilities. Most of isolates tested, possessed biofilm-related genes. Different combinations of toxin-producing genes were identified in different isolates, with all isolates containing nhe while only some contained hbl and cytK. None of the food isolates contained the emetic ces gene. This study highlights the diversity of B. cereus s.l. in biofilm formation, sporulation and their genetic variables.