Antibiotic resistance in foodborne Listeria.
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Anti-Bacterial Agents↗
Biomedical subjects
E Giovanetti
Publications and source records attributed to E Giovanetti.
Development of in-vitro resistance to glycopeptide antibiotics: assessment in staphylococci of different species.
Forty-two clinical isolates belonging to ten species of staphylococci were studied for their ability to develop single-step resistance, in vitro, to glycopeptide antibiotics. Selection was attempted through separate exposure to four glycopeptides (vancomycin, teicoplanin, and two investigational semisynthetic derivatives of the latter, TD-A3 and CTA-A1) on agar containing 10 mg/l of the test drug. No survivors from any test strain were recovered after exposure to TD-A3 or CTA-A1. After exposure to vancomycin or teicoplanin, surviving clones were only recovered from strains of three species, Staphylococcus aureus, S. epidermidis, and S. haemolyticus. Emergence of resistant clones was easier to observe from strains of S. haemolyticus exposed to teicoplanin. When tested for susceptibility, many survivors exhibited vancomycin and teicoplanin MICs below the drug concentration used for in-vitro selection, probably due to an inoculum effect in the plating procedure. In particular, the vancomycin MICs did not exceed 8 mg/l for S. aureus and S. epidermidis clones, and reached 16 mg/l for some clones from a S. haemolyticus strain. Teicoplanin MICs did not exceed 8 mg/l for S. aureus clones, but reached 64 mg/l for some clones of S. epidermidis, and were particularly high (64 to greater than or equal to 128 mg/l) for most clones of S. haemolyticus. In contrast, against all clones selected from all three species, the MICs of TD-A3 and CTA-A1 did not exceed 2 and 4 mg/l, respectively. Morphological investigations indicated that the colonies of a highly resistant S. haemolyticus clone were smaller and more butyraceous in consistency than those of the parent strain. In transmission and scanning electron microscopy studies, this same S. haemolyticus clone showed a more irregular cell wall than the parent strain.
Aminoglycosides↗
Selection of resistance to glycopeptide antibiotics in staphylococci.
Clinical strains belonging to ten Staphylococcus species were investigated for their abilities to develop single-step resistance in vitro to vancomycin and teicoplanin. Surviving clones were only recovered from strains of three species, namely S. aureus, S. epidermidis, and S. haemolyticus. A similar ratio of grown to plated cells (approximately 1 x 10(-8)) was mostly obtained from strains of S. aureus and S. epidermidis. Higher ratios (1 x 10(-6) to 1 x 10(-7)) were obtained from strains of S. haemolyticus, especially when exposed to teicoplanin. When tested for susceptibility, many survivors exhibited vancomycin and teicoplanin minimum inhibitory concentrations (MICs) below the drug concentration used for in vitro selection, probably due to an inoculum effect in the plating procedure. However, MICs were particularly high in many clones of S. haemolyticus (up to 12.8 microg/ml for vancomycin, and > or = 102.4 microg/ml for teicoplanin).
Anti-Bacterial Agents↗
Antimicrobial properties of N-carboxybutyl chitosan.
N-Carboxybutyl chitosan, a modified chitin of crustacean origin, displayed inhibitory, bactericidal, and candidacidal activities when tested against 298 cultures of various pathogens. Examination by electron microscopy showed that microbial cells exposed to N-carboxybutyl chitosan underwent marked morphological alterations. The data are of importance in defining the suitability of N-carboxybutyl chitosan as a wound dressing.
Anti-Bacterial Agents↗
[Staphylococcus haemolyticus. Bacterial resistance to teicoplanin and associated morpho-structural aspects].
To improve our understanding of the bases of teicoplanin resistance we studied a "one-step" mutant of S. haemolyticus from a morphological point of view. The results show that the organization of peptidoglycan is altered in the resistant S. haemolyticus strain. It is suggested that the alterations, including the spongier cell wall structure, may prevent the teicoplanin from reaching its target.
Anti-Bacterial Agents↗