Characterization of Surface Properties and Attachment of Campylobacter jejuni and Campylobacter coli to Abiotic Surfaces

Vu Tuan Nguyen (2011). Characterization of Surface Properties and Attachment of Campylobacter jejuni and Campylobacter coli to Abiotic Surfaces PhD Thesis, School of Agriculture and Food Sciences, The University of Queensland.

       
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Author Vu Tuan Nguyen
Thesis Title Characterization of Surface Properties and Attachment of Campylobacter jejuni and Campylobacter coli to Abiotic Surfaces
School, Centre or Institute School of Agriculture and Food Sciences
Institution The University of Queensland
Publication date 2011-11
Thesis type PhD Thesis
Supervisor Prof. Gary Dykes
Dr. Mark Turner
Dr. Narelle Fegan
Total pages 291
Total black and white pages 291
Language eng
Subjects 090804 Food Packaging, Preservation and Safety
060501 Bacteriology
030603 Colloid and Surface Chemistry
Abstract/Summary Campylobacter jejuni and C. coli are among the leading causes of human foodborne diarrhoeal diseases. Attachment to food related surfaces have been shown to enhance the movement of foodborne pathogens through food systems to ultimately cause disease. The mechanisms of attachment of C. jejuni and C. coli to abiotic surfaces remain relatively poorly understood. In order to assist in understanding this attachment, this work aimed to investigate the influence of cell surface hydrophobicity (water contact angle), surface charge (zeta potential), prior planktonic (broth) or sessile (agar) mode of growth, environmental temperature, contact time and the presence of cell surface polysaccharides on attachment of 13 C. jejuni strains and 5 C. coli strains to three abiotic surfaces (stainless steel, glass and polyurethane). All strains had different abilities to attach to stainless steel and glass but did not attach to polyurethane with the exception of one strain. The number of cells attaching to stainless steel and glass significantly correlated with water contact angles (P≤0.007), but not with zeta potential (P≥0.507). Cells grown as planktonic and sessile culture generally differed significantly from each other with respect to hydrophobicity and attachment (P<0.05), but not with respect to surface charge (P>0.05). These results suggest that increased cell surface hydrophobicity, but not surface charge, may enhance attachment of C. jejuni and C. coli to abiotic surfaces, while previous mode of growth affects their surface properties and attachment in a strain-dependent manner. Six strains (five C. jejuni strains and one C. coli strain) showing distinct hydrophobicity and ability to attach to abiotic surfaces were found to attach to stainless steel at significantly (P<0.05) lower numbers at 4°C (~ 4 log cells/cm2) than at higher temperatures (~ 5 log cells/cm2 at 55°C) after 30 min of contact, while their probability of detachment significantly (P<0.05) decreased from ≥ 0.219 at 4°C to ≥ 0.111 at 25°C. At 4°C, the numbers of cells attaching to stainless steel increased from ~ 4 to ~ 5 log cell/cm2 while the probability of detachment significantly (P<0.05) decreased from 0.443 to 0.134 after 1 min to 240 min of contact. These results suggest that elevated temperatures and longer contact times may increase the level and strength of attachment of C. jejuni and C. coli to abiotic surfaces. Three out of these five C. jejuni strains attached differently to abiotic surfaces from each other. This data could be interpreted using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory because these strains showed a significant difference (P<0.05) in contact angle measurement (CAM) data and subsequent acid-base (AB) interactions. However, XDLVO theory failed to explain the attachment of three Salmonella strains due to similar AB interactions, as established by CAM, between them. These findings indicate that the XDLVO theory could only predict bacterial attachment if differences in AB interactions between strains were apparent by CAM. However, CAM may not always reflect AB interactions exactly since microbial adhesion to solvents (MATS) revealed a significant difference (P<0.05) in AB interactions between the three Salmonella strains. The difference in the results from MATS and CAM should be therefore considered when predicting bacterial attachment using the XDLVO theory. Since surface polysaccharides including capsular polysaccharides (CPS) and lipooligosaccharides (LOS) are associated with cell surface hydrophobicity, four highly hydrophobic and adherent strains (three C. jejuni strains and one C. coli strain) were further characterized to investigate the role of CPS and LOS in cell surface hydrophobicity, surface charge, autoagglutination (AAG) activity and their attachment to stainless steel and glass. This was achieved by removal of CPS and truncation of LOS core oligosaccharides by inactivating the kpsE and waaF genes, respectively. There were no significant (P>0.05) differences between the three C. jejuni strains and their ∆kpsE and ∆waaF mutants with respect to all traits tested. However, inactivation of the kpsE gene significantly (P≤0.026) reduced the zeta potential of the C. coli strain from -10 to -6 mV and increased its AAG activity from 0.204 to 0.924 while disruption of the waaF gene significantly (P≤0.037) increased its water contact angles of > 8° and decreased numbers of cells attaching to stainless steel and glass of ~ 0.5 log/cm2. These results suggest that CPS and LOS may play a role in the cell surface properties and attachment to abiotic surfaces for C. coli but not C. jejuni. In conclusion, the initial attachment of C. jejuni and C. coli to food processing surfaces plays an important role in their contamination of food and transmission through food chain to infection. However, most previous studies have focused on their attachment to intestinal cells during infection rather than their initial attachment to abiotic surfaces. This work has made an original contribution to the field of food microbiology by, for the first time, investigating some bacterial surface and environmental factors associated with the attachment of C. jejuni and C. coli to abiotic surfaces commonly used in food processing. These results not only contribute towards a better understanding of the mechanisms of C. jejuni and C. coli attachment to abiotic surfaces but also provide a rationale for investigating the effect of other factors such as substratum properties, O-linked and N-linked glycans that are potentially involved in bacterial attachment. This knowledge is important with respect to food safety and public health because a better understanding of the mechanism of C. jejuni and C. coli attachment to abiotic surfaces may assist the development of anti-attachment interventions to ultimately reduce food contamination and human infections by these pathogens.
Keyword Campylobacter jejuni
Campylobacter coli
Attachment
detachment
Surface Properties
Capsular Polysaccharide
Lipooligosaccharide
XDLVO
Additional Notes Page numbers in landscape: 107, 109, 116, 137, 212- 215, 220-221, 228-235

 
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