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CFU Cm (cfu + cm)
Selected AbstractsInvestigation of critical inter-related factors affecting the efficacy of pulsed light for inactivating clinically relevant bacterial pathogensJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2010H.P. Farrell Abstract Aims:, To investigate critical electrical and biological factors governing the efficacy of pulsed light (PL) for the in vitro inactivation of bacteria isolated from the clinical environment. Development of this alternative PL decontamination approach is timely, as the incidence of health care,related infections remains unacceptably high. Methods and Results:, Predetermined cell numbers of clinically relevant Gram-positive and Gram-negative bacteria were inoculated separately on agar plates and were flashed with ,60 pulses of broad-spectrum light under varying operating conditions, and their inactivation measured. Significant differences in inactivation largely occurred depending on the level of the applied lamp discharge energy (range 3·2,20 J per pulse), the amount of pulsing applied (range 0,60 pulses) and the distance between light source and treatment surface (range 8,20 cm) used. Greater decontamination levels were achieved using a combination of higher lamp discharge energies, increased number of pulses and shorter distances between treatment surface and the xenon light source. Levels of microbial sensitivity also varied depending on the population type, size and age of cultures treated. Production of pigment pyocynanin and alginate slime in mucoid strains of Pseudomonas aeruginosa afforded some protection against lethal action of PL; however, this was evident only by using a combination of reduced amount of pulsing at the lower lamp discharge energies tested. A clear pattern was observed where Gram-positive bacterial pathogens were more resistant to cidal effects of PL compared to Gram negatives. While negligible photoreactivation of PL-treated bacterial strains occurred after full pulsing regimes at the different lamp discharge energies tested, some repair was evident when using a combination of reduced pulsing at the lower lamp discharge energies. Strains harbouring genes for multiple resistances to antibiotics were not significantly more resistant to PL treatments. Slight temperature rises (,4·2°C) were measured on agar surfaces after extended pulsing at higher lamp discharge energies. Presence of organic matter on treatment surface did not significantly affect PL decontamination efficacy, nor did growth of PL-treated bacteria on selective agar diminish survival compared to similarly treated bacteria inoculated and enumerated on nonselective agar plates. Conclusions:, Critical inter-related factors affecting the effective and repeatable in vitro decontamination performance of PL were identified during this study that will aid further development of this athermal process technology for applications in health care and in industry. Very rapid reductions (c. 7 log10 CFU cm,2 within ,10 pulses) occurred using discharge energy of 20 J for all tested clinically relevant bacteria under study when treated at 8 cm distance from xenon light source. While no resistant flora is expected to develop for treatment of microbial pathogens on two-dimensional surfaces, careful consideration of scale up factors such as design and operational usage of this PL technique will be required to assure operator safety. Significance and Impact of the Study:, Findings and conclusions derived from this study will enable further development and optimization of this decontamination technique in health care and in food preparation settings, and will advance the field of nonthermal processing technologies. [source] Modelling of Campylobacter survival in frozen chicken meatJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2007M. Ritz Abstract Aims:, To model the survival kinetics of Campylobacter jejuni on frozen chicken meat. Methods and Results:, Three different types of chicken meat surface (skin, skinned muscle and cut muscle) were inoculated with stationary phase cells of C. jejuni (8 log10 CFU cm,2) and frozen for 5 weeks at ,20°C. Bacterial numbers were determined weekly using two different methods of enumeration to quantify uninjured and injured cells. Analysis of variance of the results showed that the type of chicken surface and the method used to enumerate surviving cells were the most significant sources of variations in the numbers recovered (P < 0·0001), much more than the freezing time. To identify an appropriate model for the description of effects of freezing on survival over time, several models were fitted to the count data. Decay was found to be nonlinear. In general, survival was least on skin, better on skinned muscle and best on cut muscle. After 2 weeks, additional inactivation by freezing appeared to be negligible. Conclusion:, Because of the variability of survival it was not possible to fit and select a general model useful for all the different surfaces types. Significance and Impact of the Study:, The injured state of the cells leads to variability and the underestimation of bacterial survival. This is an essential factor for the assessment of Campylobacter -associated risk. [source] Bacterial contamination on touch surfaces in the public transport system and in public areas of a hospital in LondonLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2009J.A. Otter Abstract Aims:, To investigate bacterial contamination on hand-touch surfaces in the public transport system and in public areas of a hospital in central London. Methods and Results:, Dipslides were used to sample 118 hand-touch surfaces in buses, trains, stations, hotels and public areas of a hospital in central London. Total aerobic counts were determined, and Staphylococcus aureus isolates were identified and characterized. Bacteria were cultured from 112 (95%) of sites at a median concentration of 12 CFU cm,2. Methicillin-susceptible Staph. aureus (MSSA) was cultured from nine (8%) of sites; no sites grew methicillin-resistant Staph. aureus (MRSA). Conclusions:, Hand-touch sites in London are frequently contaminated with bacteria and can harbour MSSA, but none of the sites tested were contaminated with MRSA. Significance and Impact of the Study:, Hand-touch sites can become contaminated with staphylococci and may be fomites for the transmission of bacteria between humans. Such sites could provide a reservoir for community-associated MRSA (CA-MRSA) in high prevalence areas but were not present in London, a geographical area with a low incidence of CA-MRSA. [source] Effect of dietary supplementation with vitamin E on characteristics of vacuum-packed lambJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2007Jesús de la Fuente Abstract The effect of dietary vitamin E supplementation on lamb during vacuum-packed storage was studied. Thirty-six weaned male Manchego breed lambs were offered four dietary treatments (20, 270, 520 and 1020 mg vitamin E kg,1 feed). Lambs were fed the vitamin E-supplemented diet from 13 until 26 kg live weight. Pieces of M. longissimus dorsi were stored under vacuum at 2 ± 1 °C in the dark and meat quality was assessed after 5, 14 and 28 days of storage. Dietary supplementation significantly increased the ,-tocopherol concentration in the muscle (P < 0.001). Initially, lipid oxidation, meat colour and bacterial load were similar in all groups. In meat of non-supplemented lambs the thiobarbituric acid reactive substance value increased throughout storage, whereas in meat of supplemented lambs it did not increase. Meat pigments and discolouration proportion were significantly affected by storage time (P < 0.001). The bacterial load was low initially, but after 28 days of storage it was close to 7 log10 colony-forming units (cfu) cm,2 and Enterobacteriaceae surpassed the limit of acceptability of 2.5 log10 cfu cm,2, making the lamb unsuitable for human consumption. Meat of supplemented lambs displayed less lipid oxidation than that of their non-supplemented counterparts, while meat colour and bacterial load were not affected by supplementation. Copyright © 2007 Society of Chemical Industry [source] | ||||||||||