Development and verification of a test rig for inactivation of bacteria and (corona-) viruses by UVC air disinfection systems

The ongoing coronavirus pandemic spreads through airborne transmission and is therefore difficult to contain. However, coronaviruses are highly sensitive to UVC, so UVC air disinfection systems should be able to inactivate the virus. Unfortunately, so far there are only few possibilities to test the reduction of airborne viruses or other pathogens. A special test rig, which mainly consisted of a nebulizer and an airflow system, was developed to determine the antiviral and antibacterial efficiency of UVC air disinfection systems. In the assessment of such an UVC air disinfection system with nebulized Staphylococcus carnosus and a sampling period of 30 minutes, a mean bactericidal reduction of 3.70 log10 (99.98 %) was determined. For antiviral irradiation of the coronavirus surrogate phi6 a mean viral load reduction of 1.18 log10 (93.40 %) was observed after a sampling period of 10 minutes. Therefore, mobile UVC air disinfection systems could be applied in hospitals, retirement and nursing homes.

The effect of two starter cultures on some chemical and sensory properties of Macedonian traditional sausage

The aim of this study is to monitor the effect of two starter cultures on some chemical and sensory properties of industrially produced Macedonian traditional sausage. The research covered three variants: Variant 1: Control variant (conventionally produced Macedonian traditional sausages using nitrite salt and powdered acerola); Variant 2: Macedonian traditional sausages where the basic formulation was enriched by addition of starter culture CS-300 (Staphylococcus carnosus ssp. utilis + Staphylococcus carnosus) in combination with Swiss chard powder and powdered acerola; Variant 3: Macedonian traditional sausages where the basic formulation was enriched by addition of starter cultures CS-300 (Staphylococcus carnosus ssp. utilis + Staphylococcus carnosus) and BLC-78 (Pediococcus acidilactici + Staphylococcus carnosus) in combination with Swiss chard powder and powdered acerola. Starter cultures have a positive effect on changing the pH value of sausages, which creates favorable conditions for the development of the desired microflora. In the sausages from variant 2 the value for water activity is constant, and the largest decrease was determined in the variant 3. Nitrate-reducing bacteria in combination with a natural source of nitrates (Swiss chard powder and leek) are a suitable substitute for nitrite salt, thus eliminating its negative effects on consumer health. According to the obtained results, with the use of the starter culture CS-300 good quality of the sausages is achieved. At the same time a safe product is obtained where the use of nitrite salt is completely eliminated.

Photoinactivation of Staphylococci with 405 nm Light in a Trachea Model with Saliva Substitute at 37 °C

The globally observed rise in bacterial resistance against antibiotics has increased the need for alternatives to antibiotic treatments. The most prominent and important pathogen bacteria are the ESKAPE pathogens, which include among others Staphylococcus aureus, Klebsiella pneumoniae and Acinetobacter baumannii. These species cause ventilator-associated pneumonia (VAP), which accounts for 24% of all nosocomial infections. In this study we tested the efficacy of photoinactivation with 405 nm violet light under conditions comparable to an intubated patient with artificial saliva for bacterial suspension at 37 °C. A technical trachea model was developed to investigate the visible light photoinactivation of Staphylococcus carnosus as a non-pathogen surrogate of the ESKAPE pathogen S. aureus (MRSA). The violet light was coupled into the tube with a fiber optic setup. The performed tests proved, that photoinactivation at 37 °C is more effective with a reduction of almost 3 log levels (99.8%) compared to 25 °C with a reduction of 1.2 log levels. The substitution of phosphate buffered saline (PBS) by artificial saliva solution slightly increased the efficiency during the experimental course. The increased efficiency might be caused by a less favorable environment for bacteria due to for example the ionic composition.

Label-Free Electrochemical Sensor for Rapid Bacterial Pathogen Detection Using Vancomycin-Modified Highly Branched Polymers

Rapid point of care tests for bacterial infection diagnosis are of great importance to reduce the misuse of antibiotics and burden of antimicrobial resistance. Here, we have successfully combined a new class of non-biological binder molecules with electrochemical impedance spectroscopy (EIS)-based sensor detection for direct, label-free detection of Gram-positive bacteria making use of the specific coil-to-globule conformation change of the vancomycin-modified highly branched polymers immobilized on the surface of gold screen-printed electrodes upon binding to Gram-positive bacteria. Staphylococcus carnosus was detected after just 20 min incubation of the sample solution with the polymer-functionalized electrodes. The polymer conformation change was quantified with two simple 1 min EIS tests before and after incubation with the sample. Tests revealed a concentration dependent signal change within an OD600 range of Staphylococcus carnosus from 0.002 to 0.1 and a clear discrimination between Gram-positive Staphylococcus carnosus and Gram-negative Escherichia coli bacteria. This exhibits a clear advancement in terms of simplified test complexity compared to existing bacteria detection tests. In addition, the polymer-functionalized electrodes showed good storage and operational stability.

The influence of the denitrifying strain of Staphylococcus carnosus No. 5304 on the content of nitrates in the technology of yogurt production

Contamination of food with nitrates is a generally recognized problem. Milk is the basis for the production of many milk mixtures for baby food, and children are considered to be the most vulnerable category to the harmful influence of nitrates. The purpose of the search was to investigate the denitrification of milk with different amounts of nitrates by the denitrifying microorganisms of Staphylococcus carnosus in the technology of production of sour-milk products. The denitrification process of S. carnosus milk in the amount of 103 CFU.cm-3 was found to reduce the nitrate content by an average of 88.0 ±3.9 mg.kg-1 and in the samples of the first group was 10.3 ±2.4 mg.kg-1, the second 110.7 ±4.1 and the third 214.5 ±6.3 mg.kg-1, respectively. In the search of the denitrification process of S. carnosus milk in the amount of 104 CFU.cm-3, was found that in the ready yogurt in the samples of the first group the amount of nitrates was 1.1 ±0.1 mg.kg-1, in the second group 56.4 ±3.5 mg.kg-1, and in the third 159.5 ±4.1 mg.kg-1 respectively. In the search of the denitrification process of S. carnosus milk in the amount of 105 CFU.cm-3, was found that nitrates were practically absent in the samples of the first group, the second group did not exceed 10 mg.kg-1, and the third was 107.4 ±3.9 mg.kg-1. Therefore, received data indicate the possibility of using strain S. carnosus No. 5304 for denitrification of milk with a high content of nitrates in the technology of production of fermented milk products, in particular yogurt.

The Use of the Mixed Bacteria Limosilactobacillus fermentum and Staphylococcus carnosus in the Meat Curing Process with a Reduced Amount of Sodium Nitrite

The aim of the research was to estimate the possibility of using mixed bacteria cultures consisting of Lactobacillus fermentum S8 and Staphylococcus carnosus ATCC 51365 in the meat curing process with a reduced amount of sodium nitrite and to study the effect of bacteria on residual nitrites and nitrates, nitrosyl pigments content, colour, pH, redox potential, microbiologic, and the sensory quality of a cooked meat product. The study was performed on heat treated three-model meat treatments in cans: (C) a control treatment with NaNO2 at 100 mg/kg, (M) a treatment with NaNO2 at 50 mg/kg and (SL) a treatment with NaNO2 at 50 mg/kg and L. fermentum S8 at about 107 cfu/g and S. carnosus ATCC 51365 at about of 107 cfu/g. The research was performed after production and after cold storage. It was shown that using a mixed bacteria culture for meat curing had an influence (p < 0.05) on reducing nitrite and nitrate levels and increasing the amount of nitrosyl pigments in the SL treatment compared to the M treatment. Applying mixed bacteria in curing meat with NaNO2 at 50 mg/kg allowed for obtaining a higher redness in the cooked meat product after production, storage and exposure to light than in the product cured with NaNO2 at 100 mg/kg, with similar sensory and microbiological quality in both products.

Avaliação da qualidade sensorial, instrumental e microbiológica de salames tipo Italiano, adicionados de culturas starters

Objetivou-se com esse estudo, produzir salames com e sem a adição de culturas starters e avaliar o efeito das mesmas sobre as características sensoriais, físicas e microbiológicas dos produtos. Foram elaborados 3 tratamentos de salames tipo italiano: T1 (controle - sem adição de cultura starter); T2, produto com adição de culturas starters Lyocarni RHM-33 (Pediococcus pentosaceus e Staphylococcus xylosus) e T3 com adição de culturas starters Lyocarni SBM-11 (Staphylococcus xylosus, Staphylococcus carnosus, e Lactobacillus sakei). A contagem de bactérias láticas nos produtos inoculados ao final do 21º dia de processamento, foi de 2,9 x 106 UFC/g, e 3,2 x 105 UFC/g, para os tratamentos 2 e 3 respectivamente. A contagem de coliformes totais e termotolerantes não foi afetada (P>0,05) pela interação entre tratamentos. A presença de culturas starters nos tratamentos não afetou os índices de luminosidade (L*) e Índice de amarelo (b*) em relação ao tratamento controle (p>0,05). Para índice de vermelho e saturação, o Tratamento 2 apresentou maiores valores (P<0,05). Apenas os parâmetros de dureza e mastigabilidade foram afetados (p<0,05) pela adição das culturas starters. Os dados obtidos com a análise sensorial mostraram que o tratamento T2, apresentou-se como o melhor aceito entre os salames produzidos, para os atributos de sabor, textura e impressão global. Com isso, este trabalho mostrou que devem ser estudados profundamente os aspectos físicos, microbiológicos e sensoriais para a escolha de culturas starters, pois a interação dos microrganismos interferem nos aspectos tecnológicos dos produtos.

Effect of storage temperature on volatile marker compounds in cured loins fermented with Staphylococcus carnosus by brine injection

In this study, the influence of low (5 °C), intermediate (15 °C) and high (25 °C) storage temperatures on the profile of volatile compounds of North European cured loins fermented with Staphylococcus carnosus strains was investigated. In this context, proteolytic activity, bacterial growth, key volatile compounds and sensory attributes were studied. In conclusion, storage temperature significantly affected the volatile marker compounds. A multiple regression indicated significant effects of seven volatile compounds (acetophenone, benzaldehyde, butanone, 3-methylbutanal, 1-octen-3-ol, nonanal and pentanone) on the overall odor (R2 = 95.9%) and overall flavor (R2 = 81.1%). The sum of the marker volatiles aldehydes, ketones and alcohol increased with rising temperatures and the highest amounts of the odor active 3-methylbutanal up to 155 and 166 ng/g meat were detected in high temperature-stored loins. Moreover, the addition of S. carnosus strain LTH 3838 showed maximum effect at 5 °C-storage temperature in comparison to the control.