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R V Lachica

Publications and source records attributed to R V Lachica.

At least 19 recordsLinked to original sources
PubMed1996

Hemolytic activity reevaluation of putative nonpathogenic Listeria monocytogenes strains.

Identification of 12 strains originally characterized as nonpathogenic Listeria monocytogenes was reassured following the evaluation of their hemolytic capability with a newly developed horse blood agar plate. Seven of the strains were observed consistently to be hemolytic and confirmed as L. monocytogenes with the use of two commercial systems: the Gene-Trak L. monocytogenes-specific colorimetric DNA hybridization assay and the API Listeria system. Except for one strain that formed typical smooth colonies, these hemolytic strains formed rough colonies on a selective medium, lithium chloride-ceftazidime agar. The rest of the strains were nonhemolytic and did not hybridize with the DNA probe; they were identified as Listeria innocua on the basis of their API Listeria system biochemical profile. All but one of these nonhemolytic strains formed smooth colonies on lithium chloride-ceftazidime agar.

Agar↗
PubMed1990

Selective plating medium for quantitative recovery of food-borne Listeria monocytogenes.

A new plating medium (lithium chloride-ceftazidime agar [LCA]) was designed to quantitatively recover food-borne Listeria monocytogenes in the form of large colonies while inhibiting most other food-borne microorganisms. This medium included brain heart infusion agar as the nutritive agar base and a combination of selective agents (LiCl, glycine anhydride, and ceftazidime). Comparison of LCA and lithium chloride-phenylethanol-moxalactam agar (LPM) indicated that both were equally effective for the enumeration of the cold-tolerant pathogen in artificially and naturally contaminated foods. However, LCA was more effective than LPM in the recovery of sublethally heat-injured cells. Moreover, Listeria colonies on LCA exhibited a more distinct bluish hue than those on LPM when viewed by the Henry oblique transillumination technique.

Culture Media↗
PubMed1990

Simplified Henry technique for initial recognition of Listeria colonies.

The Henry oblique transmitted-light viewing technique was modified to provide a more precise, convenient, and familiar manner with which to read (score) and recognize colonies of listeriae by their distinct bluish cast. The simplified technique involved illuminating each colony directly with a high-intensity lamp while viewing it with a hand lens at a precise angle in place of a scanning light microscope.

Bacteriological Techniques↗
PubMed1990

Same-day identification scheme for colonies of Listeria monocytogenes.

A diagnostic scheme is described for the same-day identification of food-borne cells of Listeria monocytogenes that emerge in 40 h at 30 degrees C as large colonies, representatives of which are used to advantage as heavy inocula on agar plates for the rapid determination of hemolytic activity and acidification of rhamnose and xylose. Additional tests consisting of phase-contrast microscopy for cell morphology and motility, the catalase production test, and the KOH viscosity test in place of Gram staining complete the rapid identification scheme.

Bacteriological Techniques↗
PubMed1990

Simple assay of calcium dependency for virulent plasmid-bearing clones of Yersinia enterocolitica.

A simplified procedure to detect the calcium dependency of virulent plasmid-bearing strains of Yersinia enterocolitica was developed. A low-calcium, agarose-based medium of brain heat infusion with added magnesium effectively differentiated plasmid-bearing and plasmidless isolates. Further, the expression of calcium dependency in plasmid-bearing strains of Y. enterocolitica as measured by the average colony diameter was proportional to the calcium concentration of the assay.

Calcium↗
PubMed1987

Assay of crystal violet binding for rapid identification of virulent plasmid-bearing clones of Yersinia enterocolitica.

A rapid, reliable, and simple method based on the binding of crystal violet (CV) is described for differentiating virulence-plasmid-bearing strains of Yersinia enterocolitica from their plasmidless derivatives. As with other plasmid-mediated properties of this organism, the binding of CV occurs at 37 degrees C but not at 25 degrees C. The CV-binding technique provides a simple and efficient means of screening Y. enterocolitica for virulence and for identifying individual plasmid-bearing colonies.

Animals↗
PubMed1984

Egg yolk-free Baird-Parker medium for the accelerated enumeration of foodborne Staphylococcus aureus.

A simplified procedure is described for the accelerated enumeration of foodborne Staphylococcus aureus. This involves the replacement of egg yolk in the Baird-Parker medium with Tween 80 and MgCl2. These compounds, along with pyruvate, allow the recovery of stressed cells of S. aureus on a medium which contains potassium tellurite, LiCl, and glycine as selective agents. Black colonies are identified as S. aureus by the simplified thermonuclease test.

Culture Media↗
PubMed1984

Plasmid-associated cell surface charge and hydrophobicity of Yersinia enterocolitica.

Virulent strains of Yersinia enterocolitica and their plasmidless, avirulent derivatives were examined for their cell surface properties. Increased surface charge and hydrophobicity of Y. enterocolitica were found to be associated with the possession of a 40- to 48-megadalton plasmid. These surface properties were expressed, as were other plasmid-associated properties, at 37 but not at 22 degrees C. The concentration of calcium in the growth medium had a moderate effect on the expression of the cell surface properties. These cell surface properties were greatly reduced among plasmid-bearing cells grown on tryptic soy agarose regardless of growth temperatures. These properties were also associated with the ability of Y. enterocolitica to colonize the gastrointestinal tract of mice.

Cell Membrane↗
PubMed1984

Association of fibril structure formation with cell surface properties of Yersinia enterocolitica.

Electron microscopic examination of virulence plasmid-bearing cells of Yersinia enterocolitica revealed the formation of a fibril structure when grown at 37 degrees C but not at 22 degrees C. Plasmidless cells did not exhibit any surface matrix. The formation of this surface component was associated with increased cell surface charge and hydrophobicity, formation of long chains of cells, and autoagglutination. This structure is distinct from the rigid appendages (fimbriae) which are elaborated by certain Yersinia strains.

Adhesiveness↗
PubMed1984

Determination of plasmid-associated hydrophobicity of Yersinia enterocolitica by a latex particle agglutination test.

A quick and simple method was developed to distinguish hydrophobic from hydrophilic cells. The latex particle agglutination test is based on the hydrophobic interactions between cells and latex particles which result in the agglutination of the suspension mixture. There was a direct correlation between the expression of plasmid-associated cell surface properties and latex particle agglutination by Yersinia enterocolitica. Multivalent cation-induced agglutination of suspensions of washed cells of virulent Y. enterocolitica and latex particles is indicative of their amphipathic character. Electrostatic interaction may also play a role in the latex particle agglutination reaction.

Latex Fixation Tests↗
PubMed1972

Tolerance of staphylococcal thermonuclease to stress.

Remarkable tolerance to prolonged heating, prolonged storage, and bacterial proliferation was exhibited by staphylococcal thermonuclease in foods and broth. A purified enzyme preparation added to Brain Heart Infusion broth was unaffected by the growth of five bacterial species. Minimal inactivation was effected by Bacillus subtilis. Optimal growth of Streptococcus faecalis var. liquifaciens caused extensive inactivation of thermonuclease. However, storage at room temperature or the addition of 5% NaCl caused only minimal inactivation.

Bacillus subtilis↗