Morphophysiological responses of detached and adhered biofilms of Pseudomonas fluorescens to acidic electrolyzed water.

Pseudomonas spp. have emerged as the main spoilage bacteria, with many strains easily forming biofilms on food-contact surfaces and causing cross-contamination. The efficacy of disinfectants against bacteria is usually tested with planktonic cells; however, the disinfection tolerance of biofilms, especially detached biofilms, remains unknown. Here, we investigated the tolerance responses of detached and adhered biofilms of Pseudomonas fluorescens to acidic electrolyzed water (AEW) by determining tolerance responses by plate counting, comparing them using a Weibull model, and verifying changes in bacterial morphology by scanning electron microscopy. The experimental data and the responses calculated using Weibull a (scale) and b (shape) parameters agreed well (R2 values: 0.974-0.999), and we found that AEW exhibited effective antimicrobial activity against P. fluorescens, with adhered biofilms were more resistant than detached biofilms and planktonic cells. Additionally, AEW increased the bacterial membrane permeability and decreased the membrane potential, intracellular ATP concentrations, and intracellular pH while also triggering the disruption of extracellular polymeric substances. These results demonstrated that the morphophysiological responses of detached and adhered biofilms differed significantly and provided information on disinfectant-resistance strategies potentially beneficial to the development of novel disinfection approaches.

Evaluation of the spoilage potential of bacteria isolated from chilled chicken in vitro and in situ.

Microorganisms play an important role in the spoilage of chilled chicken. In this study, a total of 53 isolates, belonging to 7 species of 3 genera, were isolated using a selective medium based on the capacity to spoil chicken juice. Four isolates, namely Aeromonas salmonicida 35, Pseudomonas fluorescens H5, Pseudomonas fragi H8 and Serratia liquefaciens 17, were further characterized to assess their proteolytic activities in vitro using meat protein extracts and to evaluate their spoilage potential in situ. The in vitro studies showed that A. salmonicida 35 displayed the strongest proteolytic activity against both sarcoplasmic and myofibrillar proteins. However, the major spoilage isolate in situ was P. fragi H8, which exhibited a fast growth rate, slime formation and increased pH and total volatile basic nitrogen (TVBN) on chicken breast fillets. The relative amounts of volatile organic compounds (VOCs) originating from the microorganisms, including alcohols, aldehydes, ketones and several sulfur compounds, increased during storage. In sum, this study demonstrated the characteristics of 4 potential spoilage bacteria on chilled yellow-feather chicken and provides a simple and convenient method to assess spoilage bacteria during quality management.

A Small RNA, SaaS, Promotes Salmonella Pathogenicity by Regulating Invasion, Intracellular Growth, and Virulence Factors.

Salmonella enterica serovar Enteritidis is a common foodborne pathogen that infects both humans and animals. The S. Enteritidis virulence regulation network remains largely incomplete, and knowledge regarding the specific virulence phenotype of small RNAs (sRNAs) is limited. Here, we investigated the role of a previously identified sRNA, Salmonella adhesive-associated sRNA (SaaS), in the virulence phenotype of S. Enteritidis by constructing mutant (ΔsaaS) and complemented (ΔsaaS/psaaS) strains. SaaS did not affect S. Enteritidis; it was activated in the simulated intestinal environment (SIE), regulating the expression of virulence target genes. We discovered that it directly binds ssaV mRNA. Caco-2 and RAW 264.7 cell assays revealed that SaaS promoted S. Enteritidis invasion and damage to epithelial cells while suppressing macrophage overgrowth and destruction. Furthermore, a BALB/c mouse model demonstrated that the deletion of SaaS significantly reduced mortality and attenuated the deterioration of pathophysiology, bacterial dissemination into systemic circulation, and systemic inflammation. Our findings indicate that SaaS is required for S. Enteritidis virulence and further highlight its biological role in bacterial pathogenesis. IMPORTANCE Salmonella is a zoonotic pathogen with high virulence worldwide, and sRNAs have recently been discovered to play important roles. We explored the biological characteristics of the sRNA SaaS and developed two cell infection models and a mouse infection model. SaaS is an SIE-responsive sRNA that regulates the expression of virulence-targeted genes. Additionally, it differentially mediates invasion and intracellular growth for survival and infection of the epithelium and macrophages. We further found that SaaS enhanced bacterial virulence by promoting lethality, colonization, and inflammatory response. These findings provide a better understanding of the critical role of sRNA in bacterial virulence.

Spatiotemporal analysis of hand, foot and mouth disease data using time-lag geographically-weighted regression.

Hand, Foot, and Mouth Disease (HFMD) is a common and widespread infectious disease. Previous studies have presented evidence that climate factors, including the monthly averages of temperature, relative humidity, air pressure, wind speed and Cumulative Risk (CR) all have a strong influence on the transmission of HFMD. In this paper, the monthly time-lag geographically- weighted regression model was constructed to investigate the spatiotemporal variations of effect of climate factors on HFMD occurrence in Inner Mongolia Autonomous Region, China. From the spatial and temporal perspectives, the spatial and temporal variations of effect of climate factors on HFMD incidence are described respectively. The results indicate that the effect of climate factors on HFMD incidence shows very different spatial patterns and time trends. The findings may provide not only an indepth understanding of spatiotemporal variation patterns of the effect of climate factors on HFMD occurrence, but also provide helpful evidence for making measures of HFMD prevention and control and implementing appropriate public health interventions at the county level in different seasons.

Gelatin enhances the flavor of chicken broth: A perspective on the ability of emulsions to bind volatile compounds.

The mechanism of flavor retention in chicken broth from the perspective of gelatin affecting the flavor-binding ability of emulsions was investigated. Results showed that fat was the important reservoir for aroma compounds in the emulsion. The particle sizes of emulsions significantly decreased with prolonged stewing time of gelatin, which was consistent with the results from confocal laser scanning microscopy and interfacial tension. The ability of pre-heated gelatin emulsions to bind volatile compounds with higher hydrophobicity was enhanced. When 0.1% gelatin was added into chicken broth, the total amount of the main volatile compounds (OAV > 1) increased from 458.83 ng/g to 1218.42 ng/g. In summary, the pre-heated gelatin increased the interfacial pressure of water/oil interface, resulting in a smaller particle size of oil droplets, and these further increased the binding area between oil droplets and flavor compounds. This appears to be the mechanism that gelatin enhances the flavor intensity of chicken broth.

Characterization of the bacterial community of braised chicken, a specialty poultry product in China.

High-throughput sequencing of 16S rDNA and culture-dependent methods were applied to determine the bacterial communities of braised chicken during processing and storage. Environmental microorganisms were also evaluated using a sedimentation plate method. The results showed that airborne microbial counts in the braising room were higher than those in the control room (25°C, a space to lower the temperature of the chicken products) and storage rooms (4°C). The microbial identification technique 16S rDNA sequences has indicated that more than 229 operational bacterial species were associated with the microbiota present in braised chicken, largely involving Pseudomonas, Psychrobacter, Weissella, Kurthia, Brochothrix, and Lactobacillus in modified-atmosphere packing (MAP) products. The storage place and temperature during processing has great impact on the shelf life of the chicken. The microbes in MAP were significantly higher (P < 0.05) in 0 and 7th day, while the microbial activity in vacuum packaging (VP) was lower because the VP products were treated at higher temperature (100°C for 20 min). Within chicken products, Pseudomonas, Brochothrix, and Lactobacillus were most prevalent in MAP products. According to this research, in order to prolong the shelf life of meat products, proper storage places and packaging conditions are necessary to be improved to reduce the microbial load in the food products.

Characterization of Extracellular Polymeric Substances Produced by Pseudomonas fragi Under Air and Modified Atmosphere Packaging.

Extracellular polymeric substances (EPS) play an important role in bacterial biochemical properties. The characteristics of EPS from 2 strains of Pseudomonas fragi cultured in meat aerobically (control) and in modified atmosphere packaging (MAP) were studied. The amount and components of EPS, the surface properties, and the effect on biofilm formation of several spoilage organisms were evaluated. The results showed that MAP inhibited the growth of the P. fragi strains. Compared with the control, more loose and less bound EPS (containing protein and carbohydrate) were produced by P. fragi in MAP samples. MAP also caused increased cell autoaggregation and surface hydrophobicity. After the removal of the EPS, the surface property changes were strain-dependent, suggesting that membrane compositions were also changed. In addition, the EPS displayed significant antibiofilm activity on Pseudomonas fluorescens and Serratia liquefaciens. In conclusion, P. fragi strains not only modified the amount, components, and surface properties of EPS but also changed the cell membrane compositions to adapt to MAP stress. Moreover, EPS may play an important role in microbial community competitions.

Physicochemical properties of Pseudomonas fragi isolates response to modified atmosphere packaging.

Pseudomonas spp., in particular Pseudomonas fragi, are dominant in aerobically stored chilled meats. This work isolated P. fragi isolates from spoiled chicken and investigated the effect of modified atmosphere packaging (MAP, CO2/N2 30%/70%) on physicochemical properties of P. fragi isolates compared to the corresponding controls (air). A total of six P. fragi isolates were isolated from aerobically stored spoiled chicken. MAP inhibited the growth of the isolates primarily in the exponential phase without inducing cell death and weakened the isolate's ability to form biofilms. Isolates 2 and 25, which readily form biofilms, exhibited improved stationary-phase growth in MAP compared to the control packaging. Changes in the surface properties, including reduced motility, increased aggregation and hydrophobicity, were also induced by MAP. The surface property results were then confirmed via scanning electron microscopy. In addition, significant differences were observed in cell phenotypic characterization between individual isolates tested, which indicated that the responses to MAP exposure were strain-dependent. These cell responses allowed P. fragi to adapt to MAP. The study provides practical information regarding microbial responses to MAP stresses, which will help further understanding the bacteriostatic mechanism of MAP.

Mini-invasive Transforaminal Lumbar Interbody Fusion through Wiltse Approach to Treating Lumbar Spondylolytic Spondylolisthesis.

OBJECTIVE: To assess the clinical efficacy of mini-invasive transforaminal lumbar interbody fusion (TLIF) through the Wiltse approach for treating lumbar spondylolytic spondylolisthesis. METHODS: In this retrospective controlled study, 69 cases with lumbar spondylolytic spondylolisthesis treated in Qilu hospital from April to November 2014 were randomly assigned to Wiltse approach (31 cases, 16 male, 15 female; mean age 45.1 years) and traditional approach groups (38 cases, 21 male, 17 female; 47.2 years. In the Wiltse approach group, the affected level was L4, 5 in 19 cases and L5 S1 in 12, 9 of whom had low back pain (LBP) only and 21 both LBP and leg pain. There were 17 cases of I degree and 14 of II degree spondylolisthesis. Pre-operative Japanese Orthopedic Association (JOA) score was 13.1 ± 2.6; visual analog scale (VAS) for LBP 7.4 ± 1.2; VAS for leg pain 6.1 ± 2.0 and Oswestry disability index (ODI) score 42.2% ± 1.2%. In the traditional approach group, the affected level was L4, 5 in 22 cases and L5 S1 in 16, 11 of whom had LBP only and 27 both LBP and leg pain. There were 21 cases of I degree and 17 of II degree spondylolisthesis. Pre-operative JOA score was 12.8 ± 1.2; VAS for LBP 6.9 ± 1.1; VAS for leg pain 7.1 ± 2.0 and ODI score 41.2% ± 2.0%. The JOA score, VAS for LBP and leg pain, ODI dynamic X-rays, CT and/or MR were evaluated 3 and 6 months and 1 year postoperatively. RESULTS: There were no differences in sex, age, affected levels, spondylolisthesis degree, pre-operative JOA score, VAS for LBP or leg pain and ODI score between the two groups (P > 0.05). The incision length, blood loss and time to achieving exposure were better in the Wiltse approach than the traditional approach group (P < 0.05). The VAS for LBP and muscle atrophy MRI scores were significantly lower in the Wiltse approach than the traditional approach group on Days 1 and 14 and at 1 year follow-up (P < 0.05). The VAS for leg pain, JOA recovery rate and JOA and ODI scores tended to be lower in the Wiltse approach than the traditional approach group at 1 year follow-up examinations (no differences statistically significant, P > 0.05). The interbody fusion rate was not significantly different between the groups (P > 0.05). There were no complications of internal fixation in either group. CONCLUSION: TLIF via both approaches has satisfactory clinical efficacy. TLIF through the Wiltse approach significantly reduces the damage of multifidus and postoperative incidence of chronic LBP.