Katie Fisher

The ecology, epidemiology and virulence of Enterococcus.

Enterococci are Gram-positive, catalase-negative, non-spore-forming, facultative anaerobic bacteria, which usually inhabit the alimentary tract of humans in addition to being isolated from environmental and animal sources. They are able to survive a range of stresses and hostile environments, including those of extreme temperature (5-65 degrees C), pH (4.5-10.0) and high NaCl concentration, enabling them to colonize a wide range of niches. Virulence factors of enterococci include the extracellular protein Esp and aggregation substances (Agg), both of which aid in colonization of the host. The nosocomial pathogenicity of enterococci has emerged in recent years, as well as increasing resistance to glycopeptide antibiotics. Understanding the ecology, epidemiology and virulence of Enterococcus species is important for limiting urinary tract infections, hepatobiliary sepsis, endocarditis, surgical wound infection, bacteraemia and neonatal sepsis, and also stemming the further development of antibiotic resistance.

The effect of lemon, orange and bergamot essential oils and their components on the survival of Campylobacter jejuni, Escherichia coli O157, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus in vitro and in food systems

Aims:  To investigate the effectiveness of oils and vapours of lemon (Citrus limon), sweet orange (Citrus sinensis) and bergamot (Citrus bergamia) and their components against a number of common foodborne pathogens.

The survival of three strains of Arcobacter butzleri in the presence of lemon, orange and bergamot essential oils and their components in vitro and on food

Aims:  To test the effect of oils and vapours of lemon, sweet orange and bergamot and their components against three Arcobacter butzleri strains.

The mechanism of action of a citrus oil blend against Enterococcus faecium and Enterococcus faecalis.

Aims:  The aim was to explore the mechanisms by which a blend of orange (Citrus sinensis) :  bergamot (Citrus bergamia) (1 : 1 v/v) EO (essential oil) (2% v/v) and its vapour (15 mg l−1 air) brings about its antimicrobial effect against Enterococcus faecium and Enterococcus faecalis.

In vitro inhibition of vancomycin susceptible and vancomycin resistant Enterococcus faecium and E. faecalis in the presence of citrus essential oils.

Abstract Glycopeptide-resistant Enterococcus (GRE) is an important healthcare-acquired infection (HCAI) which costs the healthcare service many millions of pounds worldwide. In this study, lemon (Citrus limon), sweet orange (Citrus sinensis) or bergamot (Citrus bergamia) essential oils (EO) and their vapours, alone and in combination, are tested for their antimicrobial activity against vancomycin-resistant and vancomycin-sensitive strains of E. faecium and E. faecalis. A blend of 1:1 (v/v) orange and bergamot EO was the most effective of the oils and/or blends tested with a minimum inhibitory concentration (MIC), at 25˚C and pH 5.5, of 0.25–0.5% (v/v) and a minimum inhibitory dose (MID) of 50 mg/L, at 50˚C at pH 7.5, when viable counts reduced by 5.5–10 log10 colony forming units (cfu)/mL, suggesting that this blend of citrus oils is effective under a range of conditions for inhibiting the growth and survival of E. faecalis, E. faecium and VRE.