Photocatalytic Bactericidal Performance of LaFeO3 under Solar Light in the Presence of Natural Organic Matter: Spectroscopic and Mechanistic Evaluation

Solar photocatalytic inactivation (SPCI) of E. coli as the indicator microorganism using LaFeO3 (LF) has already been investigated under various experimental conditions, excluding any role of natural organic matter (NOM). However, comprehensive information about the behavior of E. coli and its inactivation mechanism in the presence of NOM, as well as the behavior of NOM components via solar photocatalysis using LF as a photocatalyst, has prime importance in understanding real natural water environments. Therefore, in this study, further assessment was devoted to explore the influence of various NOM representatives on the SPCI of E. coli by using LF as a novel non-TiO2 photocatalyst. The influence of NOM as well as its sub-components, such as humic acids (HA) and fulvic acids (FA), was also investigated to understand different NOM-related constituents of real natural water conditions. In addition to spectroscopic and mechanistic investigations of cell-derived organics, excitation emission matrix (EEM) fluorescence spectra with parallel factor multiway analysis (PARAFAC) modeling revealed further information about the occurrence and/or disappearance of NOM-related and bacteria-related fluorophores upon LF SPCI. Both the kinetics as well as the mechanism of the LF SPCI of E. coli in the presence of NOM compounds displayed substrate-specific variations under all conditions.

Influence of dry and wet beef maturation on the microbiological quality and safety

The most used methods for the maturation process are vacuum (wet-aged) and dry (dry-aged), which can influence the microbiological quality and safety of meat for consumption. In this study, we aimed to verify the differences in microbiological quality between beef (Longissimus dorsi) that was wet-aged and dry-aged for 30 days, by quantification of indicator microorganism groups and molecular identification of Salmonella, Listeria monocytogenes, and diarrheagenic Escherichia coli. This study verified that the meat matured by the dry-aged method showed significantly lower counts of total coliforms, aerobic mesophiles, psychrotrophs, and molds and yeasts as compared to wet-aged meat. While the Salmonella spp. was not isolated in any beef sample, L. monocytogenes and enteropathogenic E. coli (EPEC), and shiga toxin-producing E. coli (STEC) and enterohemorrhagic E. coli (EHEC) were isolated only from wet-aged beef. Thus, it was concluded that the superficial dehydration of the meat during dry-aged maturation, if carried out correctly and hygienically, confers higher microbiological quality and can reduce the occurrence of microbiological hazards.

COMPARATIVE ASSESSMENT OF THE SANITARY AND EPIDEMIC IMPORTANCE OF СOLIFORM INDICATORS OF THE DRINKING WATER QUALITY

Introduction. The criteria used for the sanitary-bacteriological assessment of the quality of tap water should ensure its epidemic safety, which is important when choosing priority indicator microorganisms, quantitative determination of which will allow characterizing the risk of intestinal infections associated with water use conditions with sufficient reliability. Material and methods. Analyzed water studies for 10 years for the presence of sanitary-indicative bacteria in the water of surface water bodies in accordance with the guidelines MUK 4.2.1884. To isolate and quantify Salmonella, there were used the conventional magnesium medium and the developed nutrient medium, ready for use. The obtained data were processed using the statistical software package Statistic for Windows. Results. It has been established that E.coli can be considered as an additional indicator in order to assess recent fecal contamination. The absence of E.coli in drinking water does not guarantee the absence of other members of the family Enterobacteriaceae. Pathogenic and potentially pathogenic bacteria exhibited the greatest viability. E. coli turned out to be less stable, i.e. microorganisms, on an indication of which the system of sanitary and epidemic safety of the water use was built. In the experiments, lactose-positive coliform bacteria were established to be less resistant to the action of disinfecting agents than salmonella and potentially pathogenic bacteria, which should not be inherent to the indicator microorganism. Conclusion. Research results indicate that the absence of normalized lactose-positive fecal indicators fails to guarantee the absence of infectious agents since lactose-negative enterobacteria are unaccounted for - pathogenic and potentially pathogenic species causing intestinal infections. Therefore, in the sanitary-bacteriological control of tap water, it is more expedient to focus on the indicator glucose coliform bacteria (GKB).

Bacteriological quality evaluation of bedpans in a university hospital

According to the Centers of Disease Control and prevention recommendations, it is necessary to restrain the emergence of multiresistant microorganisms at hospital and control cross-transmission among patients. In this context, one of the main points is the daily strict management of excreta in the care units. We aim to evaluate the safety of reusable bedpans, from a bacteriological point of view, after passing through bedpan washers in our hospital. The present study was conducted from 15 January 2015 to 27 February 2015 in Strasbourg Hospital University. 25 bedpan washers were selected. Three bedpans per bedpan washer were collected for bacterial analysis after cleaning and disinfection. Samples were performed in real conditions, i.e. patients used bedpans without protective bag before passing through bedpan washers. There was no growth (≤1 CFU/25cm2) in 75.3% (55/73) of the samples and 95.8% (70/73) had a result which was below the target value (≤25 CFU/25cm2). Only 3 samples (4.1%), from different bedpan washers, have a result above the target value. A third of the identified bacteria were environmental microorganisms and 2 thirds were skin flora. No indicator microorganism was identified (Staphylococcus aureus, enterobacteria, enterococci, Pseudomonas aeruginosa, Pseudomonas sp, Stenotrophomonas maltophilia, Acinetobacter spp., Candida spp., filamentous fungi). The effectiveness of bedpan washers is quite acceptable regarding the bactericidal activity. Indeed, we expected less good results since a small amount of bedpans are visibly soiled at the end of the cycle. However, it would be of interest to perform a second study evaluating the virucidal and sporicidal activity of the bedpan washers.

Contamination Revealed by Indicator Microorganism Levels during Veal Processing

ABSTRACT During site visits of veal processors, the U.S. Department of Agriculture, Food Safety Inspection Service (FSIS) has reported processing deficiencies that likely contribute to increased levels of veal contamination. Here, we report the results of measuring aerobic plate count bacteria (APC), Enterobacteriaceae, coliforms (CF), and Escherichia coli during eight sample collections at five veal processors to assess contamination during the harvest of bob veal and formula-fed veal before (n = 5 plants) and after (n = 3 plants) changes to interventions and processing practices. Hides of veal calves at each plant had mean log CFU/100 cm2 APC, Enterobacteriaceae, CF, and E. coli of 6.02 to 8.07, 2.95 to 5.24, 3.28 to 5.83, and 3.08 to 5.59, respectively. Preintervention carcasses had mean log CFU/100 cm2 APC, Enterobacteriaceae, CF, and E. coli of 3.08 to 5.22, 1.16 to 3.47, 0.21 to 3.06, and −0.07 to 3.10, respectively, before and 2.72 to 4.50, 0.99 to 2.76, 0.69 to 2.26, and 0.33 to 2.12, respectively, after changes were made to improve sanitary dressing procedures. Final veal carcasses had mean log CFU/100 cm2 APC, Enterobacteriaceae, CF, and E. coli of 0.36 to 2.84, −0.21 to 1.59, −0.23 to 1.59, and −0.38 to 1.45 before and 0.44 to 2.64, −0.16 to 1.33, −0.42 to 1.20, and −0.48 to 1.09 after changes were made to improve carcass-directed interventions. Whereas the improved dressing procedures resulted in improved carcass cleanliness, the changes to carcass-directed interventions were less successful, and veal processors are urged to use techniques that ensure uniform and consistent delivery of antimicrobials to carcasses. Analysis of results comparing bob veal to formula-fed veal found bob veal hides, preintervention carcasses, and final carcasses to have increased (P < 0.05) APC, Enterobacteriaceae, CF, and E. coli (with the exception of hide Enterobacteriaceae; P > 0.05) relative to formula fed veal. When both veal categories were harvested at the same plant on the same day, similar results were observed. Since identification by FSIS, the control of contamination during veal processing has started to improve, but challenges still persist.

Antimicrobial and antioxidant activities of Enterococcus species isolated from meat and dairy products

Lactic acid bacteria (LAB) have an important role in a great variety of fermented foods. In addition to their contribution to sensory characteristics, they enhance food preservation and can be used as probiotics. In this study, the antimicrobial and antioxidant activities of culture supernatants and cell free extracts of 16 LAB isolated from meat and dairy products were investigated. The bacterial were identified by 16S rRNA sequencing. GenBank BLAST analysis revealed that all the isolates belong to Enterococcus faecium species. Antimicrobial activity against the indicator microorganism (Listeria monocytogenes) was observed at 11 culture supernatants and 4 cell free extracts. The sensibility of culture supernatant was evaluated by proteinase K and trypsin and it was observed that activity of antimicrobial substance was completely lost after the treatment. All of the isolates showed antioxidant activity as determined by the Thiobarbituric Acid Reactive Substances (TBARS) method with both types of extracts. When the antioxidant capacity was investigated using ABTS•+ method (2,2 azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) and DPPH method (2,2-diphenyl-1-picrylhydrazyl) it was observed that only culture supernatants showed antioxidant capacity. These bacteria could particularly help to reduce or inhibit pathogenic microorganisms as well as oxidative spoilage in foods and feed.

Disinfection characteristics of the combined ultraviolet radiation and ozone process using Escherichia coli as a probe

In the present study, the characteristics of the combined ultraviolet (UV) and ozone disinfection process were investigated from kinetic and mechanistic viewpoints employing Escherichia coli (E. coli) as an indicator microorganism. Compared to individual unit processes, the combined UV/O3 tests produced excess hydroxyl radicals (HO•) and yielded synergistic inactivation of E. coli in the initial phase of reaction. The presence of O3 during UV exposure caused the destruction of cell structure, and then repressed bacteria regrowth after treatment. Moreover, the formation of malondialdehyde (MDA) showed that the improved generation of intermediate HO• via ozone photolysis accelerated the decomposition of bacterial cell surfaces, which was further confirmed by the leakage of intracellular potassium ions (K+). The results suggested that the synergistic bactericidal effect of combined UV/O3 owed mainly to the enhanced destruction of bacterial cell structure.

Production of bacteriocin-like inhibitory substance by Bifidobacterium lactis in skim milk supplemented with additives

Bacteriocins are natural compounds used as food biopreservatives instead of chemical preservatives. Bifidobacterium animalis subsp. lactis (Bifid. lactis) was shown to produce a bacteriocin-like inhibitory substance (BLIS) able to inhibit the growth of Listeria monocytogenes selected as an indicator microorganism. To enhance this production by the strain Bifid. lactis BL 04, skim milk (SM) was used as a fermentation medium either in the presence or in the absence of yeast extract, Tween 80 or inulin as stimulating additives, and the results in terms of bacterial growth and BLIS production were compared with those obtained in a traditional high cost complex medium such as Man, Rogosa and Sharpe (MRS). To this purpose, all the cultivations were carried out in flasks at 200 rpm under anaerobic conditions ensured by a nitrogen flowrate of 1·0 L/min for 48 h, and BLIS production was quantified by means of a modified agar diffusion assay at low values of both temperature and concentration of List. monocytogenes. Although all these ingredients were shown to exert positive influence on BLIS production in both media, yeast extract and SM were by far the best ingredient and the best medium, respectively, allowing for a BLIS production at the late exponential phase of 2000 AU/ml.

Rapid Detection of Lactobacillus kefiranofaciens in Kefir Grain and Kefir Milk Using Newly Developed Real-Time PCR

Lactobacillus kefiranofaciens is an indicator microorganism for kefir and a key factor in kefir grain formation and kefiran production. We designed a novel real-time PCR primer and probe set, LKF_KU504, for the rapid detection of L. kefiranofaciens. In inclusivity and exclusivity tests, only 14 L. kefiranofaciens strains were positive among 61 microorganisms, indicating 100% sensitivity and specificity. The LKF_KU504 set also differentiated kefir milk from 30 commercial nonkefir yogurts. The levels of L. kefiranofaciens in kefir grain and kefir milk were significantly different, indicating L. kefiranofaciens was more concentrated in kefir grain than in kefir milk.

Assessment Antibacterial Activities on Essential Oil of Plant Extract

Essential oils are produced by plants for many reasons including protection against various bacterial and fungal. This study provides a dose-response analysis for antibacterial activity assessment using Escherichia coli DH5 as indicator microorganism. In this work it has been shown that it is possible to extract antibacterial activities using a simple process.