Recovery of heat-injured listeria innocua

Listeria innocua was subjected to thermal inactivation and the extent of heat-injured cells was quantified. Cultures were heated in liquid medium for different times, using temperatures in the range of 52.5 to 65.0 °C, and plated on Tryptic Soy Agar with 0.6% yeast extract (TSAYE) used as non-selective medium and on TSAYE plus 5% NaCl (TSAYE+NaCl) and Palcam agar with selective supplement (Palcam agar) as selective media. The difference observed in counts in non-selective and in selective media gave an indication of cell injury during the heat treatment. D- and z- values were calculated for all conditions considered. For each temperature, D-values obtained using non-selective recovery procedures were higher than the ones obtained using the two selective media. When comparing the selective media, it can be concluded that Palcam agar allowed recovery and growth of thermally injured cells and so it was less inhibitor than TSAYE+NaCl. Another important result was the influence of temperature on the degree of cellular injury. As temperature increases, the degree of heat-injured cells also increases, and consequently concern has to be taken with the temperature and the counting medium used in food processing studies. The results of this work clearly demonstrated that selective media used for Listeria monocytogenes enumeration/detection might not be suitable for the recovery of heatinjured cells, which can dangerously underestimate the presence of this foodborne pathogen

Comparison of recovery methods for the enumeration of injured Listeria innocua cells under isothermal and non-isothermal treatments

This study compares the feature of different media with the combination of selective with non-selective media in a TAL method for recovery of Listeria innocua cells exposed to thermal treatments. Experiments were conducted in broth at constant temperature (52.5 and 65.0 ºC) and pH (4.5 and 7.5) conditions, using NaCl or glycerol to adjust water activity to 0.95. Four different media were used in bacterial cell enumeration: (i) a non-selective medium e TSAYE, (ii) two selective media e TSAYE þ 5%NaCl and Palcam Agar and (iii) TAL medium (consisting of a layer of Palcam Agar overlaid with one of TSAYE). Two food products were used as case studies aiming at comparison of results obtained on selective and TAL media enumeration. Parsley samples were inoculated with L. innocua and subjected to posterior thermal treatments both under isothermal (52.5, 60.0 and 65.0 ºC) and non-isothermal (heating rate of 1.8 ºC/min from 20.0 to 65.0 ºC) conditions. The recovery capability of TAL method was also studied when a pre-cooked frozen food (i.e. meat pockets) was fried (oil temperature of w180 ºC). TAL method proved to be better than Palcam Agar in terms of capability to recover injured cells and was effective in L. innocua enumeration when non-sterile samples were analysed.info:eu-repo/semantics/acceptedVersio

Sigmoidal thermal inactivation kinetics of listeria innocua in broth: Influence of strain and growth phase

Listeria innocua inactivation was studied within the temperature range 52.5–65.0 ºC, comparing two different strains (10528 and 2030c) and two growth phases (exponential and stationary). Survival curves may present a sigmoidal behaviour, with an initial shoulder (L), followed by a maximum inactivation rate (kmax) period and a final tailing tendency. A Gompertz-inspired model was used to fit experimental data, and kinetic parameters (L, kmax and tail) were estimated by non-linear regression analysis. The influence of temperature, growth phase and strain on kinetic parameters was studied using a 23 factorial experimental design. Results showed that temperature and growth phase were the most significant variables affecting the kinetic parameters. Listeria thermal inactivation varied from a log-linear tendency till a pronounced sigmoidal behaviour, depending on the studied factors

Influence of pH, type of acid and recovery media on the thermal inactivation of listeria innocua

Acidification of foods with organic acids, either by fermentation or by intentional addition, is an important and common mechanism for controlling foodborne pathogens in a diversity of food products. The objective of this work was to study thermal inactivation of Listeria innocua, an acid tolerant microorganism, at 52.5, 60.0 and 65.0 °C, at different pH values (4.5, 6.0 and 7.5), using three types of acid (lactic, acetic and hydrochloric) and three different plating media (Tryptic Soy Agar with 0.6% yeast extract—TSAYE; TSAYE plus 5% NaCl—TSAYE+5%NaCl; and Palcam Agar with selective supplement—Palcam Agar), according to a 34 factorial experimental design. Survival data experimentally obtained were fitted with a Gompertz-inspired model and kinetic parameters (shoulder, maximum inactivation rate—kmax, and tail) were estimated for all conditions considered. The influence of temperature, pH, type of acid and enumeration media on kinetic parameters was assessed. Results showed that, with the exception of the type of acid, all the remaining factors and their combinations significantly affected the shoulder period and kmax. In relation to tail, temperature and recovery media were the affectable factors. It was concluded that the survival of this bacteria is higher when combining low temperature with neutral pH, and when TSAYE is the enumeration medium. Bigelow-inspired models were successfully developed and describe accurately the temperature and pH effects on the kinetic parameters

Early psychiatric morbidity in a Brazilian sample of acute ischemic stroke patients

OBJECTIVE: Stroke is a major public health problem worldwide, and its neuropsychiatric sequelae are frequent and disabling. Furthermore, there is evidence that these sequelae impair recovery. Brazil has the highest stroke rates in Latin America, but data on the frequency of neuropsychiatric disorders in these patients are scarce. This study aimed to identify mental disorders among in-hospital patients with acute ischemic stroke. METHODS: The Mini International Neuropsychiatric Interview-Plus (MINI-Plus) was applied to 60 patients during the first week of hospitalization. RESULTS: Psychiatric disorders were diagnosed in 55% of the patients. A wide range of neuropsychiatric disorders have been identified, mainly mood and anxiety disorders. Specifically, we identified major depression (26.7%), alcohol abuse or dependence (11.7%), specific phobia (8.3%), generalized anxiety disorder (6.7%), psychosis (5.0%), social phobia (3.3%), adjustment disorder (3.3%) and panic disorder (1.7%). CONCLUSION: Psychiatric comorbidity should be evaluated as part of the rehabilitation of stroke patients and should be carefully examined by physicians

Design of a lipid nanovesicle system encapsulating bacteriophages integrated in a multiple emulsion formulation: A proof-of-concept

Development of a biotechnological process for the inhalational administration of a bacteriophage was pursued, using strategies of nanoencapsulation within lipid nanovesicles. As a proof-of-concept for the nanoencapsulation strategy, a bacteriophage with broad lytic spectrum was entrapped within W/O/W multiple nanoemulsions. Physicochemical characterization of the optimized bacteriophage-encasing nanovesicles encompassed determination of particle hydrodynamic size, size distribution and particle charge via DLS, surface morphology via CRYO-SEM, and thermal analysis via DSC, whereas antimicrobial activity of the nanoemulsions produced was assessed in vitro using several bacterial strains. The optimized nanosystems showed no phase separation and encompassed nanovesicles with an average size of ca. 114 nm and an average Zeta Potential of ca. -13 mV, which were maintained stable over a storage timeframe of ca. 3 months.info:eu-repo/semantics/publishedVersio

Thermodynamics of Dipolar Chain Systems

The thermodynamics of a quantum system of layers containing perpendicularly oriented dipolar molecules is studied within an oscillator approximation for both bosonic and fermionic species. The system is assumed to be built from chains with one molecule in each layer. We consider the effects of the intralayer repulsion and quantum statistical requirements in systems with more than one chain. Specifically, we consider the case of two chains and solve the problem analytically within the harmonic Hamiltonian approach which is accurate for large dipole moments. The case of three chains is calculated numerically. Our findings indicate that thermodynamic observables, such as the heat capacity, can be used to probe the signatures of the intralayer interaction between chains. This should be relevant for near future experiments on polar molecules with strong dipole moments.Comment: 15 pages, 5 figures, final versio