Differential Resistance to Staphylococcus aureus Challenge in Two Related Lines of Chickens

ABSTRACTMethicillin-resistantStaphylococcus aureus(MRSA) isolates that are susceptible to vancomycin but are tolerant to its killing effect may present a potential challenge for effective treatment. This study compared the microbiologic characteristics of clinical vancomycin-tolerant (VT-MRSA) and vancomycin-susceptible (VS-MRSA) strains using phenotypic and gene regulation studies. MRSA isolates collected from vancomycin-treated patients with bacteremia over a 5-year period were analyzed for vancomycin, daptomycin, and telavancin susceptibility, as well as accessory gene regulator (agr) group and function. Vancomycin tolerance was defined by a minimum bactericidal concentration (MBC)/minimum inhibitor concentration (MIC) ratio of ≥32 mg/liter. VT-MRSA isolates were compared to VS-MRSA isolates for differences in antimicrobial susceptibility, time-kill activity, and gene expression of key cell envelope response genesvraSR,dltA, andmprF. All 115 isolates evaluated were susceptible to vancomycin, daptomycin, and telavancin. Seven isolates (6%) were VT-MRSA.agrgroup II was more prevalent in isolates with vancomycin MBC/MIC ratios of ≥8. In time-kill analyses, VT-MRSA had reduced vancomycin killing, but daptomycin and telavancin activities were maintained. Significantly greater gene expression was observed in VT-MRSA after 72 h of subinhibitory antibiotic exposures. Vancomycin most notably increasedvraSRexpression (P= 0.002 versus VS-MRSA strains). Daptomycin and telavancin increased expression of all genes studied, most significantlymprFexpression (P< 0.001). Longer durations of antibiotic exposure (72 h versus 24 h) resulted in substantial increases in gene expression in VT-MRSA. Although the clinical impact of VT-MRSA is not fully recognized, these data suggest that VT-MRSA strains, while still susceptible, have altered gene regulation to adapt to the antimicrobial effects of glyco- and lipopeptides that may emerge during prolonged durations of exposure.

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Differential Resistance to Staphylococcus aureus Challenge in Major Histocompatibility (B) Complex Congenic Lines

Poultry Science ◽

10.3382/ps.0711873 ◽

1992 ◽

Vol 71 (11) ◽

pp. 1873-1878 ◽

Cited By ~ 19

Author(s):

PAUL F. COTTER ◽

ROBERT L. TAYLOR ◽

HANS ABPLANALP

Keyword(s):

Staphylococcus Aureus ◽

Differential Resistance ◽

Major Histocompatibility ◽

Congenic Lines

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Cytochemical Studies of Cell Wall Biosynthesis in Staphylococcus Aureus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100094905 ◽

1972 ◽

Vol 30 ◽

pp. 328-329

Author(s):

Masaatsu Koike ◽

Koichi Nakashima ◽

Kyoko Iida

Keyword(s):

Staphylococcus Aureus ◽

Periodate Oxidation ◽

Early Time ◽

The Other ◽

Penicillin G ◽

Cell Wall Biosynthesis ◽

Septal Wall ◽

Peptidoglycan Biosynthesis ◽

Gram Positive Bacteria ◽

Cross Linkage

Penicillin exerts the activity to inhibit the peptide cross linkage between each polysaccharide backbone at the final stage of wall-peptidoglycan biosynthesis of bacteria. Morphologically, alterations of the septal wall and mesosome in gram-positive bacteria, which were occurred in early time after treatment with penicillin, have been observed. In this experiment, these alterations were cytochemically investigated by means of silver-methenamine staining after periodate oxidation, which is applied for detection of localization of wall mucopolysaccharide.Staphylococcus aureus strain 209P treated with 100 u/ml of penicillin G was divided into two aliquotes. One was fixed by Kellenberger-Ryter's OSO4 fixative at 30, 60 and 120 min after addition of the antibiotic, dehydrated through alcohol series, and embedded in Epon 812 (Specimen A). The other was fixed by 21 glutaraldehyde, dehydrated through glycolmethacrylate series and embedded in glycolmethacrylate mixture, according to Bernhard's method (Specimen B).

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Gold labeling of teichoic acid on adjacent surfaces of staphylococcus aureus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100160443 ◽

1990 ◽

Vol 48 (3) ◽

pp. 578-579

Author(s):

Margaret Hukee

Keyword(s):

Staphylococcus Aureus ◽

Teichoic Acid ◽

Protein Labeling ◽

Minimal Amount ◽

Section Thickness ◽

Double Labeling ◽

Parallel Surfaces ◽

Supporting Membrane

Gold labeling of two antigens (double labeling) is often done on two section surfaces separated by section thickness. Whether labeling is done on both sides of the same section or on two parallel surfaces separated by section thickness (PSSST), comparable results are dependent on an equal number of epitopes being exposed at each surface. We propose a method to study protein labeling within the same field of proteins, by examining two directly adjacent surfaces that were split during sectioning. The number of labeling sites on adjacent surfaces (AS) were compared to sites on PSSST surfaces in individual bacteria.Since each bacteria needed to be recognizable in all three section surfaces, one-hole grids were used for labeling. One-hole grids require a supporting membrane and excessive handling during labeling often ruptures the membrane. To minimize handling, a labeling chamber was designed that is inexpensive, disposable, minimizes contamination, and uses a minimal amount of solution.

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Compositional Tuning of Negative Differential Resistance in Bulk Silver Iodide Memristor

New Journal of Chemistry ◽

10.1039/d0nj05427e ◽

2020 ◽

Author(s):

SMITA GAJANAN NAIK ◽

Mohammad Hussain Kasim Rabinal

Keyword(s):

Power Consumption ◽

Negative Differential Resistance ◽

Silver Iodide ◽

Differential Resistance ◽

Fast Response ◽

Low Power Consumption ◽

Switching Effect ◽

Memory Switching ◽

Bulk Silver ◽

Emerging Memory

Electrical memory switching effect has received a great interest to develop emerging memory technology such as memristors. The high density, fast response, multi-bit storage and low power consumption are their...

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