Category Archives: Pseudomonas

RASFF Alert- Pseudomonads and Acinetobacter – Fresh Low-Fat Milk

RASFF

Presence of Pseudomonads and Acinetobacter in fresh low-fat milk from Germany in Austria

Research – Killing of a Multispecies Biofilm Using Gram-Negative and Gram-Positive Targeted Antibiotic Released from High Purity Calcium Sulfate Beads

MDPI

Abstract

Background: Multispecies biofilm orthopedic infections are more challenging to treat than mono-species infections. In this in-vitro study, we aimed to determine if a multispecies biofilm, consisting of Gram positive and negative species with different antibiotic susceptibilities could be treated more effectively using high purity antibiotic-loaded calcium sulfate beads (HP-ALCSB) containing vancomycin (VAN) and tobramycin (TOB) in combination than alone. Methods: Three sets of species pairs from bioluminescent strains of Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA) and clinical isolates, Enterococcus faecalis (EF) and Enterobacter cloacae were screened for compatibility. PA + EF developed intermixed biofilms with similar cell concentrations and so were grown on 316L stainless steel coupons for 72 h or as 24 h agar lawn biofilms and then treated with HP-ALCSBs with single or combination antibiotics and assessed by viable count or bioluminescence and light imaging to distinguish each species. Replica plating was used to assess viability. Results: The VAN + TOB bead significantly reduced the PA + EF biofilm CFU and reduced the concentration of surviving antibiotic tolerant variants by 50% compared to single antibiotics. Conclusions: The combination of Gram-negative and positive targeted antibiotics released from HP-ALCSBs may be more effective in treating multispecies biofilms than monotherapy alone.

Research – Microbiological Quality and Safety of Fresh Quail Meat at the Retail Level

MDPI

Abstract

The objective of this study was to evaluate the microbiological quality and safety of 37 fresh quail meats. Mesophiles, Pseudomonas spp., Enterobacteriaceae, and staphylococci counts were 5.25 ± 1.14, 3.92 ± 1.17, 3.09 ± 1.02, and 2.80 ± 0.64 log CFU/g, respectively. Listeria monocytogenes was detected in seven samples (18.92%). Campylobacter jejuni was detected in one sample (2.70%). Clostridium perfringens was not detected in any sample. The dominant bacteria were Pseudomonas spp. (30.46%), Micrococcaceae (19.87%), lactic acid bacteria (14.57%), and Enterobacteriaceae (11.92%). Brochotrix thermosphacta and enterococci were isolated to a lesser extent, 7.28% and 1.99%, respectively. The dominant Enterobacteriaceae found were Escherichia coli (42.53%). ESBL-producing E. coli was detected in one sample (2.70%), showing resistance to 16 antibiotics. Sixteen different Staphylococcus spp. and three Mammaliicoccus spp. were identified, the most common being S. cohnii (19.86%) and M. sciuri (17.02%). S. aureus and S. epidermidis were also found in one and four samples, respectively. Methicillin-resistant M. sciuri and S. warneri were found in 13.51% and 10.81% of quail samples, respectively. These bacteria showed an average of 6.20 and 18.50 resistances per strain, respectively. The high resistance observed in ESBL-producing E. coli and methicillin-resistant S. warneri is of special concern. Measures should be adopted to reduce the contamination of quail meat.

Research – Microbial Spoilage of Traditional Goose Sausages Produced in a Northern Region of Italy

MDPI

Abstract

Recently, during the ripening of goose sausage, a defect consisting of ammonia and vinegar smell was noticed. The producer of the craft facility, located in Lombardia, a Northern region of Italy, asked us to identify the cause of that defect. Therefore, this study aimed to identify the potential responsible agents for the spoilage of this lot of goose sausages. Spoilage was first detected by sensory analysis using the “needle probing” technique; however, the spoiled sausages were not marketable due to the high ammonia and vinegar smell. The added starter culture did not limit or inhibit the spoilage microorganisms, which were represented by Levilactobacillus brevis, the predominant species, and by Enterococcus faecalis and E. faecium. These microorganisms grew during ripening and produced a large amount of biogenic amines, which could represent a risk for consumers. Furthermore, Lev. brevis, being a heterofermentative lactic acid bacteria (LAB), also produced ethanol, acetic acid, and a variation in the sausage colour. The production of biogenic amines was confirmed in vitro. Furthermore, as observed in a previous study, the second cause of spoilage can be attributed to moulds which grew during ripening; both the isolated strains, Penicillium nalgiovense, added as a starter culture, and P. lanosocoeruleum, present as an environmental contaminant, grew between the meat and casing, producing a large amount of total volatile nitrogen, responsible for the ammonia smell perceived in the ripening area and in the sausages. This is the first description of Levilactobacillus brevis predominance in spoiled goose sausage.

Research – Pseudomonas Biofilms Pose Food Safety Threat by Aiding Listeria Survival in Processing Environments

Food Safety.Com

Pseudomonas biofilms can aid the survival of Listeria monocytogenes cells even after disinfection, according to a recent study. Although Pseudomonas are often overlooked as a food safety hazard due to being associated with food spoilage rather than with human foodborne illnesses, the study’s findings suggest that the bacteria may pose a direct threat to food safety in the processing environment.

Pseudomonas are the most commonly found bacteria in food processing environments due to characteristics such as a high growth rate at low temperatures, a high tolerance of antimicrobial agents, and biofilm formation. The bacteria have been of special interest as colonizers in food processing environments, as a food spoilage organism, and as protectors of foodborne pathogens.

Previous research has demonstrated the possibility of surviving bacteria exposed to sub-lethal concentrations of disinfectants being able to co-select for both disinfectant- and antibiotic-resistant properties. Several studies also indicate that interspecies interactions in a biofilm could serve as an accelerator for horizontal gene transfer, as well as facilitate adaptation to environmental conditions and the subsequent decreased susceptibility to antimicrobials. It has been suggested that multi-species, Pseudomonas-dominated biofilms could host and shelter pathogens like L. monocyotogenes.

In the study, researchers from the Norwegian University of Science and Technology isolated Pseudomonas samples from cleaned and disinfected surfaces in a salmon processing facility. A total of 186 isolates were screened for biofilm formation at 12 °C, and were graded as strong, medium, or weak biofilm producers. A high variation in biofilm formation was observed, with 12 percent rated as strong, 29 percent as medium, and 27 percent as weak biofilm producers, as well as 29 percent not producing a detectable biofilm.

Research – High Disinfectant Tolerance in Pseudomonas spp. Biofilm Aids the Survival of Listeria monocytogenes

MDPI

Abstract

Pseudomonas spp. are the most commonly found bacteria in food-processing environments due to properties such as a high growth rate at low temperatures, a high tolerance of antimicrobial agents, and biofilm formation. In this study, a set of Pseudomonas isolates originating from cleaned and disinfected surfaces in a salmon processing facility were screened for biofilm formation at 12 °C. A high variation in biofilm formation between the isolates was observed. Selected isolates, in both planktonic and biofilm states, were tested for resistance/tolerance to a commonly used disinfectant (peracetic acid-based) and antibiotic florfenicol. Most isolates showed a much higher tolerance in the biofilm state than in the planktonic state. In a multi-species biofilm experiment with five Pseudomonas strains with and without a Listeria monocytogenes strain, the Pseudomonas biofilm appeared to aid the survival of L. monocytogenes cells after disinfection, underscoring the importance of controlling the bacterial load in food-processing environments.

Research – Bactericidal efficacy and mechanism of alkaline electrolyzed water co-action with acidic electrolyzed water on Pseudomonas aeruginosa biofilm

Wiley Online

Abstract

Here, the bactericidal efficacy and mechanism of action of the combination of alkaline electrolyzed water (AlEW) and acidic electrolyzed water (AcEW) on Pseudomonas aeruginosa biofilm were investigated, in comparison with single AcEW or AlEW treatment. The mature P. aeruginosa biofilm was formed at 120 h of cultivation. The number of bacteria in the P. aeruginosa biofilm decreased by 7.87 and 2.51 Lg CFU/mL after single AcEW and single AlEW treatment for 8 min, while the sterilization rate reached 92.2% and 33.1%, respectively. The group of AcEW (7 min) co-action with AlEW (1 min) had a P. aeruginosa sterilization rate of 85%. The AlEW (3 min) co-action with AcEW (5 min) treatment showed the best bactericidal efficacy. With this treatment, the sterilization rate achieved 94.4%, and the extracellular protein, polysaccharide, and DNA were degraded with the ratios of 70.8%, 77.7%, and 70.5%, respectively. Thus, AlEW exhibited a major washing effect, which can destroy the biofilm structure of extracellular polymers to a certain extent, while AcEW displayed a significant bactericidal effect. These results suggest that the AlEW co-action with AcEW treatment may be a promising candidate suitable for bacterial biofilm sterilization.

Research – Monitoring Growth and Removal of Pseudomonas Biofilms on Cellulose-Based Fabrics

MDPI

Abstract

Biofilms are often tolerant towards routine cleaning and disinfection processes. As they can grow on fabrics in household or healthcare settings, resulting in odors and serious health problems, it is necessary to contain biofilms through eradication strategies. The current study proposes a novel test model for the growth and removal of biofilms on textiles with Pseudomonas fluorescens and the opportunistic nosocomial pathogen Pseudomonas aeruginosa as model organisms. To assess the biofilm removal on fabrics, (1) a detergent-based, (2) enzyme-based, and (3) combined formulation of both detergent and enzymes (F1/2) were applied. Biofilms were analyzed microscopically (FE-SEM, SEM, 3D laser scanning- and epifluorescence microscopy), via a quartz crystal microbalance with mass dissipation monitoring (QCM-D) as well as plate counting of colonies. This study indicated that Pseudomonas spp. form robust biofilms on woven cellulose that can be efficiently removed via F1/2, proven by a significant reduction (p < 0.001) of viable bacteria in biofilms. Moreover, microscopic analysis indicated a disruption and almost complete removal of the biofilms after F1/2 treatment. QCM-D measurements further confirmed a maximal mass dissipation change after applying F1/2. The combination strategy applying both enzymes and detergent is a promising antibiofilm approach to remove bacteria from fabrics.

Research – The efficacy of preharvest application of electrolyzed water and chemical sanitizers against foodborne pathogen surrogates on leafy green vegetables

 

 

Wiley Online

Abstract

Preharvest control strategies, to reduce or eliminate pathogenic bacteria in leafy vegetables that may be consumed raw, may provide additional food safety protection and shelf life quality extension beyond what is possible to achieve with postharvest sanitation alone. The aim of this study was to characterize the efficacy and effect of contact time of electrolyzed water (e-water), 1-bromo-3-chloro-5-dimethylhydantoin (BCDMH), and peracetic acid (PAA) at 80 and 150 ppm against pathogen surrogates Escherichia coli M23 (E. coli M23)and Listeria innocua ATCC 33090 (L. innocua), and a representative spoilage microorganism Pseudomonas fluorescens (P. fluorescens) on leafy green vegetables (LGV) mizuna, rocket (arugula), and red chard. Each of the leafy vegetables has a distinctly different leaf architectures that could alter the effectiveness of preharvest sanitation treatments. e-Water, BCDMH and PAA were equally effective in inactivating plant total viable count, E. coli M23, L. innocua and P. fluorescens (reduction compared to water control—0.5–4.0 log CFU/g). On average an additional 0.8 (0.4–1.1) log CFU/g inactivation was obtained by increasing sanitizer contact time from 30 min to 2 h, whereas increasing sanitizer concentrations produced, at maximum, an extra 0.5 log CFU/g inactivation. These findings suggest that e-water, BCDMH, and PAA are all useful for in-field preharvest application on a wide range of plants and increasing contact time rather than concentration improves sanitation efficacy.

Research – Report of the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) on the prospection of biological ha-zards of interest in food safety in Spain (2)

AESAN

This report addresses the prospection of biological hazards for some types of food that may pose a risk to the population and that are not currently included in the official control programs in Spain.

It completes and updates the 2018 report by the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN, 2018). A number of bacteria that are significant contributors to nosocomial infections due to the increase in the number of multi-resistant strains of Acinetobacter spp. ,Klebsiella pneumoniae and Pseudomonas aeruginosa are listed first.

It is also addressed the study of the prevalence and possible control of Bacillus cereus and Cronobacter spp. presence in cereal flours and others, the revision of Campylobacter jejuni and/or Campylobacter coli in meats other than poultry, as well as the study of Shigatoxin-producing Escherichia coli. These latter two biological agents are much better known from the food control perspective, although there are control measures for Campylobacter spp. in poultry meat and not in other types of meat such as beef or pork and in the case of E. coli, producers of Shiga toxins, the control of this particular type of pathogenic strains in food has not been specifically addressed either.

Finally, tick-borne viral encephalitis, which can be transmitted to humans through the consumption of raw milk or raw dairy products, has been indicated as a viral hazard. The prospective study shows the need to determine the prevalence of multi-resistant bacteria of Acinetobacter baumannii, K. pneumoniae and P. aeruginosa in foods in Spain, especially in ready-to-eat foods such as salads and fresh plant-based foods. This is especially important due to the lack of data on the prevalence of these bacteria in foods in Spain. However, food research is carried out in neighbouring countries.

It is also necessary to include C. jejuni and/or C. coli in the investigations of beef and pork, since the incidence of these foodborne pathogens in humans is not explained solely by the presence of these agents in poultry meat, being their presence in other animals for slaughter also evident. Similarly, outbreaks of Shiga toxin-producing E. coli have been reported in Spain over the last 25 years, which makes it advisable to control them in beef, raw milk and leafy vegetables.

With regard to Cronobacter spp. and B. cereus, the importance of these agents can be demonstrated given their survival in powdery materials such as flours of different origins, including cereals, although the reported outbreaks do not seem to indicate a high prevalence. As regards the only viral hazard mentioned, it should be noted that the wide dispersion of the ticks that can transmit this virus, together with the potential consumption of raw milk, makes it advisable to investigate it in raw milk products.

However, the study of the actual infective capacity of this virus is not easy to establish with simple analytical methods. With this last exception, research for controlling all these biological hazards in food is possible, with classical or advanced methodologies that are robust enough, available for each case.