Category Archives: Pseudomonas fluorescens

RASFF Alert – Pseudomonas fluorescens – Mozzarella

European Food Alerts

RASFF

Pseudomonas fluorescens (130000000 CFU/g) in mozzarella from Italy in Italy

Research – Synergistic antibacterial effect of nisin, ethylenediaminetetraacetic acid, and sulfite on native microflora of fresh white shrimp during ice storage

Wiley Online

This study aims to investigate the effectiveness of using nisin, ethylenediaminetetraacetic acid (EDTA), and sulfite alone or in combination in reducing Vibrio parahaemolyticus Salmonella enterica , and Pseudomonas fluorescens in broth and native microflora on raw Pacific white shrimp during ice storage. Nisin (50 ppm), EDTA (20 mM), alone or in combination were used to test on the growth of parahaemolyticus enterica , and fluorescens in broth. Nisin (50 ppm), EDTA (20 mM), sodium metabisulfite (1.25 and 0.625%), ice; alone or in combination were used on shrimps during 1°C storage for 10 days. Microbial and chemical changes were analyzed during shrimp storage. First, the combination of nisin and EDTA exhibited antibacterial effects against parahaemolyticus enterica , and fluorescens in broth. Second, in shrimp preservation, the combination of nisin, EDTA, and sulfite at a low dose of 0.625% exhibited higher antimicrobial activity than did a high dose of sulfite (1.25%). Based on aerobic bacteria counts, psychrotrophic bacteria, and TVB‐N, shrimp treatment with combination of nisin, EDTA, and low‐dose sulfite were still acceptable within 10 days of storage. Based on our findings, nisin and EDTA can be used to reduce uses of sulfite for shrimp preservation in the future.

Research – Evaluation of weakly acidic electrolyzed water and modified atmosphere packaging on the shelf life and quality of farmed puffer fish (Takifugu obscurus ) during cold storage

Wiley Online

The combined effect of weakly acidic electrolyzed water (WAEW) and modified atmosphere packaging (MAP) treatments on the quality of puffer fish (Takifugu obscurus ) during cold storage was studied on aspects of microbiological activity, texture, total volatile basic nitrogen (TVB‐N), trimethylamine (TMA), free amino acids (FAAs), thiobarbituric acid reactive substance (TBARS), ATP‐related compounds and value, volatile organic compounds (VOCs), and organoleptic properties. As a result, significantly ( < .05) higher inhibitory effects on total viable counts (TVC), H2S‐producing bacteria (including Shewanella putrefaciens ), Pseudomonas spp., and lactic acid bacteria (LAB) were observed in WAEW‐treated puffer fish packaged in 60%CO2/5%O2/35%N2 atmosphere than that in air package and vacuum package with/without WAEW‐treated samples. In addition, chemical results showed that WAEW together with MAP treatments were highly efficient in maintaining lower TVB‐N, TMA, and TBARS values in refrigerated puffer fish. Moreover, the presence of WAEW combined with MAP treatments showed positive effects on retarding the relative content of fishy flavor compounds, such as 1‐octen‐3‐ol, 1‐penten‐3‐ol, hexanal, heptanal, nonanal, decanal, ()‐2‐octenal, and 2,3‐butanedione. As a whole, the combined effect of WAEW and MAP on refrigerated puffer fish is advisable to maintain better quality and extend the shelf life.

Research – Effect of Peracetic Acid Solutions and Lactic Acid on Microorganisms in On-Line Reprocessing Systems for Chicken Slaughter Plants

Journal of Food Protection

ABSTRACT

During poultry slaughter and processing, microbial cross-contamination between individual chickens is possible, as well as from one slaughter animal to the next without direct contact. One option for reducing the risk of cross-contamination is to decrease the number of microorganisms on contact surfaces by using disinfectants. The aim is to decontaminate the surfaces coming into direct contact with the carcasses. In the present study, the effectiveness of different disinfectants was investigated in laboratory settings, simulating the conditions in the slaughterhouses and in a chicken slaughterhouse. For this, an artificial residue substance (consisting of yeast extract, albumin, and agar) was developed, tested, and included in the assays. Two disinfectants were tested under laboratory conditions: lactic acid (5 and 6.67%) and peracetic acid (0.33 and 0.5%). At the slaughterhouse, peracetic acid (0.021%) was used. In the laboratory tests, it was found that the peracetic acid solution had the highest disinfection potential with respect to an Escherichia coli strain (reduction >4 log CFU mL−1) at 0.5% without an artificial residue substance. The tested lactic acid solutions also showed the highest disinfection potential against a Pseudomonas aeruginosa strain, without an artificial residue substance. When applying the artificial residue substance, the reduction potential of lactic acid and peracetic acid was decreased to less than 1.4 log CFU mL−1. Application of peracetic acid in the slaughterhouse reduced the number of total aerobic bacteria by more than 4 log CFU mL−1 and the number of Enterobacteriaceae by more than 3 log CFU mL−1, depending on the place of sampling.

HIGHLIGHTS
  • Peracetic acid and lactic acid decreases E. coli and P. aeruginosa numbers in vitro.
  • Sanitation in place reduces the number of bacteria in a chicken slaughterhouse.
  • The number of total aerobic bacteria and Enterobacteriaceae was significantly reduced.

Research – Microbiological and real-time mechanical analysis of Bacillus licheniformis and Pseudomonas fluorescens dual-species biofilm

Microbiology Research

n natural habitats, bacterial species often coexist in biofilms. They interact in synergetic or antagonistic ways and their interactions can influence the biofilm development and properties. Still, very little is known about how the coexistence of multiple organisms impact the multispecies biofilm properties. In this study, we examined the behaviour of a dual-species biofilm at the air–liquid interface composed by two environmental bacteria: Bacillus licheniformis and a phenazine mutant of Pseudomonas fluorescens . Study of the planktonic and biofilm growths for each species revealed that P. fluorescens grew faster than B. licheniformis and no bactericidal effect from P. fluorescens was detected, suggesting that the growth kinetics could be the main factor in the dual-species biofilm composition. To validate this hypothesis, the single- and dual-species biofilm were characterized by biomass quantification, microscopy and rheology. Bacterial counts and microscale architecture analysis showed that both bacterial populations coexist in the mature pellicle, with a dominance of P. fluorescens . Real-time measurement of the dual-species biofilms’ viscoelastic (i.e. mechanical) properties using interfacial rheology confirmed that P. fluorescens was the main contributor of the biofilm properties. Evaluation of the dual-species pellicle viscoelasticity at longer time revealed that the biofilm, after reaching a first equilibrium, created a stronger and more cohesive network. Interfacial rheology proves to be a unique quantitative technique, which combined with microscale imaging, contributes to the understanding of the time-dependent properties within a polymicrobial community at various stages of biofilm development. This work demonstrates the importance of growth kinetics in the bacteria competition for the interface in a model dual-species biofilm.