Biomedical subjects

L A McLandsborough

Publications and source records attributed to L A McLandsborough.

7 recordsLinked to original sources

PubMed2006

Concentrations and tracking of listeria monocytogenes strains in a seafood-processing environment using a most-probable-number enrichment procedure and randomly amplified polymorphic DNA analysis.

Concentrations of environmental microflora and Listeria monocytogenes were monitored at multiple environmental locations within a seafood-processing facility over the course of 6 months. Concentrations of L. monocytogenes were determined using a most-probable-number (MPN) enrichment procedure. Two floor drains had persistent low concentrations of L. monocytogenes (0.03 to >1,100 MPN/cm2). In comparison, concentrations of the other organisms in the drain were much higher (heterotrophic plate count range of 10(5) to 10(8) CFU/cm2). Concentrations of environmental organisms (heterotrophic aerobic plate counts and counts of pseudomonads, Shewanella spp., Aeromonas hydrophila, and coliforms) were not correlated with concentrations of L. monocytogenes. The 178 confirmed L. monocytogenes isolates from the MPN procedure were further characterized by randomly amplified polymorphic DNA analysis. Sixteen different banding patterns were identified, and nine of the patterns were identified from samples collected on two or more collection dates. From all locations, banding type A was observed in 98 confirmed isolates (55%). Although present, L. monocytogenes was a relatively minor component in the ecosystem of the floor drains in this seafood-processing facility.

Animals↗

PubMed2002

Microtiter plate assay for assessment of Listeria monocytogenes biofilm formation.

Listeria monocytogenes has the ability to form biofilms on food-processing surfaces, potentially leading to food product contamination. The objective of this research was to standardize a polyvinyl chloride (PVC) microtiter plate assay to compare the ability of L. monocytogenes strains to form biofilms. A total of 31 coded L. monocytogenes strains were grown in defined medium (modified Welshimer's broth) at 32 degrees C for 20 and 40 h in PVC microtiter plate wells. Biofilm formation was indirectly assessed by staining with 1% crystal violet and measuring crystal violet absorbance, using destaining solution. Cellular growth rates and final cell densities did not correlate with biofilm formation, indicating that differences in biofilm formation under the same environmental conditions were not due to growth rate differences. The mean biofilm production of lineage I strains was significantly greater than that observed for lineage II and lineage III strains. The results from the standardized microtiter plate biofilm assay were also compared to biofilm formation on PVC and stainless steel as assayed by quantitative epifluorescence microscopy. Results showed similar trends for the microscopic and microtiter plate assays, indicating that the PVC microtiter plate assay can be used as a rapid, simple method to screen for differences in biofilm production between strains or growth conditions prior to performing labor-intensive microscopic analyses.

Bacterial Adhesion↗

PubMed2000

A microscopic method to visualize Escherichia coli interaction with beef muscle.

The genetic determinant for enhanced green fluorescent protein (EGFP) was introduced into Escherichia coli JM109 (ATCC 53323) and E. coli O157:H7 (ATCC 43895) on plasmid EGFP. The expression of EGFP did not change the growth kinetics or surface properties tested (hydrophobicity and electrophoretic mobility). Microscope slides were modified to allow for optimal viewing of thick meat samples with an inverted microscope. Two fluorescent dyes, nile red and Cy3 were used to stain for lipid and protein portions of beef muscle, respectively. Laser scanning confocal microscopy was used to observe interaction of the EGFP-expressing E. coli strains and the fluorescently stained muscle components without changing the spatial and temporal environment of the organisms.

Animals↗

PubMed1999

The effects of the surface charge and hydrophobicity of Escherichia coli on its adhesion to beef muscle.

The surface characteristics of Escherichia coli strains were studied to evaluate the effect upon bacterial adhesion to beef muscle. The influence of suspension conditions upon the surface charge of a pathogenic strain, E. coli O157:H7 (EC01), and a saprophytic laboratory strain, E. coli JM109 (EC22) were investigated and compared. The cellular surface charge of most E. coli O157:H7 strains were much less affected by changes in the pH, ionic strength or concentration of surfactants in the suspending medium than was the surface charge of E. coli JM109 cells. Strong adhesion to beef muscle was found in suspending conditions of pH 4 or 10, and with a lowered ionic strength. All E. coli strains tested were negatively charged in 150 mM PBS buffer (pH 7.4) as measured by zeta potentials, ranging from -4.9 to -33.9 mV. Based on the results of adhesion to hexadecane, nine out of 22 strains tested were moderately hydrophobic with about 50% of the cells bound to the solvent. Cellular adhesion of 16 E. coli strains to beef muscle was examined in 150 mM PBS buffer. Generally, O157:H7 strains had lower adhesive properties (Sr value less than 0.10) to beef muscle than other serotypes (up to 0.39). No correlation was found between E. coli cell surface charge, hydrophobicity and adhesion to beef muscle.

Alkanes↗

PubMed1995

Insertional inactivation of virR in Streptococcus pyogenes M49 demonstrates that VirR functions as a positive regulator of ScpA, FcRA, OF, and M protein.

Several reports have shown that Streptococcus pyogenes strains which produce opacity factor (OF+) have diverged significantly from OF- serotypes. This study questions whether several surface proteins of an OF+ culture are regulated by the positive regulatory protein VirR, in a manner similar to OF- strains. Interruption of the virR region of an OF+ S. pyogenes (strain CS101, M type 49) was performed using a temperature-sensitive plasmid containing a fragment of virR. Interruption of the virR region produced cultures with undetectable amounts of M49 and ScpA proteins, and reduced the yield of FcRA protein. In addition, mutants had a significant reduction in detectable opacity factor. These results suggest that virR functions as a positive regulator of a variety of surface proteins in OF+ strains.

Antigens, Bacterial↗

PubMed1995

Cloning and characterization of the abortive infection genetic determinant abiD isolated from pBF61 of Lactococcus lactis subsp. lactis KR5.

A 6.3-kb fragment from pBF61 in Lactococcus lactis subsp. lactis KR5 was cloned and found to confer an abortive phage infection (Abi+) phenotype exhibiting a reduction in efficiency of plating and plaque size for small isometric- and prolate-headed bacteriophages sk1 and c2, respectively, and to produce a 10-fold decrease in c2 phage burst size. Phage adsorption was not significantly reduced. An open reading frame of 1,098 bp was sequenced and designated abiD. Tn5 mutagenesis confirmed that abiD was required for the Abi+ phenotype.

Amino Acid Sequence↗

PubMed1995

Insertional inactivation of virR in Streptococcus pyogenes M49 demonstrates that VirR functions as a positive regulator of streptococcal C5a peptidase and M protein in OF+ strains.

Mutational analysis confirms the presence of a positively controlled virulence regulon in the OF+ lineage of S. pyogenes. Although there are differences in the organization of the virR regulon in OF+ and OF- strains, expression of these surface proteins is dependent on a VirR protein. In addition, it appears that production of OF is dependent on virR. The contribution of OF to the pathogenesis of S. pyogenes is unknown. The greater association of OF+ strains with impetigo compared to the greater association of OF- strains with pharyngitis [2] may indicate that production of apoproteinase is a contributing factor to skin infections.

Adhesins, Bacterial↗