Influence of water activity on the production of extracellular enzymes by Staphylococcus aureus

A comprehensive review of intelligent controlled release antimicrobial packaging in food preservation

Intelligent responsive packaging provides informative feedback or control the release of active substances like antimicrobial agents in response to stimuli in food or the environment to ensure food safety. This paper provides an overview of two types of intelligent packaging, information-responsive and intelligent controlled-release, focusing on the recent research progress of intelligent controlled-release antimicrobial packaging with enzyme, pH, relative humidity, temperature, and light as triggering factors. It also summarizes the current status of application in different food categories, as well as the challenges and future prospects. Intelligent controlled-release technology aims to optimize the antimicrobial effect and ensure the quality of food products by synchronizing the release of active substances with food preservation needs through sensing stimuli, which is an innovative and challenging packaging technology. The paper seeks to provide a reference for the research and industrial development of responsive intelligent packaging and controlled-release packaging applications in food.

Relationship between items of DMIST and healing of diabetic foot ulcers

A monitoring tool for the wound-healing process of diabetic foot ulcers (DFUs) was developed. It comprises seven domains, namely, depth, maceration, inflammation/infection, size, tissue type of the wound bed, type of wound edge, and tunnelling/undermining. It was named "DMIST" based on the initials of its domains. Although DMIST is useful for assessing wound-healing processes, the monitoring items related to wound healing remain unclear, thereby making the selection of optimal care based on the assessment difficult. We identified the relationship between the DMIST items and wound healing. This study was a secondary analysis of five previous investigations and was conducted using DMIST based on the diabetic foot ulcer assessment scale score and DFU images. Multivariate logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs) after simultaneously controlling for potential confounders. The examined DFU healing status revealed that some DFUs healed at 4 weeks from baseline, whereas some DFUs did not. Variables considered in the models were the scores of each DMIST domain. The study population comprised 146 Indonesian patients and 33 Japanese patients. Depth, maceration, and size were associated with DFU healing at 4 weeks from baseline [depth: OR = 0.317 (95% CI: 0.145-0.693, P = 0.004); maceration: OR = 0.445 (95% CI: 0.221-0.896, P = 0.023); size: OR = 0.623 (95% CI: 0.451-0.862, P = 0.004)]. Our findings suggest that appropriate management of maceration promotes DFU healing.

Relationship between maceration and wound healing on diabetic foot ulcers in Indonesia: a prospective study

The aim of this study was to clarify the relationship between maceration and wound healing. A prospective longitudinal design was used in this study. The wound condition determined the type of dressings used and the dressing change frequency. A total of 62 participants with diabetic foot ulcers (70 wounds) were divided into two groups: non-macerated (n = 52) and macerated wounds (n = 18). Each group was evaluated weekly using the Bates-Jensen Wound Assessment Tool, with follow-ups until week 4. The Mann-Whitney U test showed that the changes in the wound area in week 1 were faster in the non-macerated group than the macerated group (P = 0·02). The Pearson correlation analysis showed a moderate correlation between maceration and wound healing from enrolment until week 4 (P = 0·002). After week 4, the Kaplan-Meier analysis showed that the non-macerated wounds healed significantly faster than the macerated wounds (log-rank test = 19·378, P = 0·000). The Cox regression analysis confirmed that maceration was a significant and independent predictor of wound healing in this study (adjusted hazard ratio, 0·324; 95% CI, 0·131-0·799; P = 0·014). The results of this study demonstrated that there is a relationship between maceration and wound healing. Changes in the wound area can help predict the healing of wounds with maceration in clinical settings.

Microbiological Quality of Raw Dried Pasta from the German Market, with Special Emphasis on Cronobacter Species

The microbiological quality of 132 dried pasta products available on the German market, originating from 11 different countries, was studied. Sample materials included soft or durum wheat products, some of which produced with other ingredients such as eggs, spices, or vegetables. Parameters included hygiene indicators (aerobic plate count, mold count, the presence of Enterobacteriaceae) and pathogenic/toxinogenic bacterial species (Salmonella spp., Staphylococcus aureus, presumptive Bacillus cereus, and Cronobacter spp.). The overall results of hygiene parameters indicated a satisfactory quality. Salmonella was not found in any sample. Three samples were positive for S. aureus (10(2) to 10(4) colony forming unit (CFU)/g). Presumptive B. cereus at levels of 10(3) to 10(4) CFU/g were detected in 3 samples. Cronobacter spp. were isolated from 14 (10.6%) products. Of these, 9 isolates were identified as C. sakazakii, 2 each as C. turicensis and C. malonaticus, and 1 as C. muytjensii. The isolates were assigned to 9 multilocus sequence typing (MLST) sequence types and to 14 different PFGE profiles. Although pasta products are typically cooked before consumption, some consumers, and children in particular, may also eat raw pasta as nibbles. Raw pasta seems to be a relevant source of exposure to dietary Cronobacter spp., although health risks are probably restricted to vulnerable consumers. High numbers of presumptive B. cereus as found in some samples may be a risk after improper storage of cooked pasta products because toxinogenic strains are frequently found within this species.

Novel theranostic DNA nanoscaffolds for the simultaneous detection and killing of Escherichia coli and Staphylococcus aureus

A novel theranostic platform is made by utilizing a self-assembled DNA nanopyramid (DP) as scaffold for incorporation of both detection and therapeutic moieties to combat bacterial infection. Red-emissive glutathione-protected gold nanoclusters (GSH-Au NCs) were used for bacterial detection. Actinomycin D (AMD) that was intercalated on the DP scaffold was used as therapeutic agent. This results in the formation of theranostic DPAu/AMD. Model bacteria Escherichia coli and Staphylococcus aureus were found to be readily taken in the DPAu/AMD and be susceptible to its killing effect. In addition, DPAu/AMD was observed to outperform the free AMD in killing infectious bacteria. The degradation of the DP structure by DNase was found to be responsible for the release of AMD and the effective killing effect of the infectious bacteria. This novel strategy presents a basic platform for future improvements to detect infectious bacteria and treatment.

Maceration of the skin and wound bed. 1: Its nature and causes

Maceration, caused by prolonged exposure to moisture, can complicate the healing of wounds, especially chronic ones. This paper--the first of three reviewing the literature on its aetiology and management--looks at how maceration occurs.

Synthesis of pyruvate dehydrogenase in Staphylococcus aureus is stimulated by osmotic stress

The pyruvate dehydrogenase multienzyme complex (PDHC) was found to be upregulated by osmotic stress in the osmotolerant pathogen Staphylococcus aureus. Upregulation was detectable in the levels of both activity and protein and was judged to be about fourfold when sodium chloride was used to adjust the water activity (a(w)) of the growth medium to 0.94. The upregulation of the PDHC was also found to be humectant dependent and was greatest when impermeant, nonmetabolizable humectants were used to adjust a(w). Further experiments provided evidence that in addition to osmotic upregulation, the PDHC complex is also subject to catabolite repression, thus providing a possible explanation for the observation that high concentrations of carbohydrates are generally more inhibitory to the growth of this bacterial pathogen than are high concentrations of salts.

Effect of low water activity on staphylococcal enterotoxin A and B biosynthesis

Staphylococcus aureus strains FDA 743 (staphylococcal enterotoxin A [SEA]-producing), FDA 778 (staphylococcal enterotoxin B [SEB]-producing), and S6 (SEA- and SEB-producing) were used to examine the effect of low water activity (a(w)) on SEA and SEB biosynthesis. In this report, we show that SEB production is more sensitive to low a(w) than SEA production. We also show that when proline is available as a compatible solute for S. aureus, SEB production is significantly stimulated at low a(w). This stimulatory effect was not observed when other compatible solutes (i.e., glycine betaine or carnitine) were added to low a(w) growth media. Finally, Northern blot analysis revealed that the stimulation of SEB production at low a(w) by added proline occurs at the level of transcription.

Short communication: Effect of water activity on cell growth and phenol oxidase production by Streptomyces cyaneus var. viridochromogenes in surface culture

In surface cultures of Streptomyces cyaneus var. viridochromogenes, NaCl depressed water activity (a w) without supporting growth. Reducing a w from 0.987 to 0.951 led to 3- and 4-fold increases in intracellular and extracellular phenol oxidase activities, respectively.

Predictive modelling of growth of Staphylococcus aureus: the effects of temperature, pH and sodium chloride

The growth responses of Staphylococcus aureus as affected by NaCl concentration, pH value and storage temperature were studied in laboratory medium. Growth curves at concentrations of NaCl in the range 0.5-13.5% (w/v), pH values in the range 4.0-7.0 and storage temperatures in the range 10-30 degrees C were fitted using the Gompertz routine and the derived parameters modelled. Growth curves could then be regenerated for any set of conditions within the matrix studied and values for growth rate, generation time, lag time and time to 1000-fold increase predicted. The model was validated against data from the literature and was found to give realistic estimates of generation time for media and a range of foods including milk, cheese, starch-based foods and cooked meats but not for mayonnaise or Wiltshire bacon. All predictions were consistently 'fail-safe'.

High sodium chloride concentrations inhibit staphylococcal enterotoxin C gene (sec) expression at the level of sec mRNA

Expression of the staphylococcal enterotoxin type C gene (sec) is regulated in response to both high NaCl concentrations (osmolarity) and the accessory gene regulator (agr). agr is a global regulator that alters the expression of many genes in Staphylococcus aureus. In this report, we have demonstrated that osmoregulation of sec occurs at the level of mRNA independently of an intact agr allele. Northern (RNA) and Western blot (immunoblot) analyses of samples from cultures grown in low- (0 M NaCl) and high-osmotic-strength (1.2 M NaCl) media revealed that the low-osmotic-strength culture contained approximately 16-fold more SEC and sec mRNA than the high-osmotic-strength culture. sec expression in high-osmotic-strength medium was enhanced when osmoprotective compounds were added. Osmoregulation of sec expression in Agr- strains was also examined; SEC and sec mRNA levels decreased in response to high osmolarity in a manner similar to that seen in the Agr+ strains.

Moisture Requirements for Growth and Metabolite Production by Lactic Acid Bacteria

The effect of water activity ( a w ) reduction on growth and acid and diacetyl production by three lactic streptococci was studied. In addition, the influence of low moisture conditions on several bacteria of significance in the fermentation of sauerkraut was examined. The minimal a w supporting growth of dairy lactics was 0.93 in a medium adjusted with glycerol. Media adjusted with sucrose generally were more inhibitory than those in which glycerol was the humectant. Titratable acidity, although not related to the type of humectant, did depend on the a w of the medium and was directly related to the extent of growth. Diacetyl concentration increased in cultures of reduced a w when the media were adjusted with both humectants; however, the effect was greatest with glycerol. A lactic strain associated with sauerkraut fermentation appeared to grow at a lower minimal a w in a glycerol-adjusted medium than in a system adjusted with NaCl; however, none of the sauerkraut organisms grew at a w levels of <0.95 when NaCl was the solute. Acid production appeared to be related to the presence and extent of growth at all of the a w levels studied.