Advances in bacterial concentration methods and their integration in portable detection platforms: a review

Legionella is a pathogenic bacterium, ubiquitous in freshwater environments and able to colonise man-made water systems from which it can be transmitted to humans during outbreaks. The prevention of such outbreaks requires a fast, low cost, automated and often portable detection system. In this work, we present a combination of sample concentration, immunoassay detection, and measurement by chronoamperometry. A nitrocellulose microfiltration membrane is used as support for both the water sample concentration and the Legionella immunodetection. The horseradish peroxidase enzymatic label of the antibodies permits using the redox substrate 3,3′,5,5′-Tetramethylbenzidine to generate current changes proportional to the bacterial concentration present in drinking water. Carbon screen-printed electrodes are employed in the chronoamperometric measurements. Our system reduces the detection time: from the 10 days required by the conventional culture-based methods, to 2–3 h, which could be crucial to avoid outbreaks. Additionally, the system shows a linear response (R2 value of 0.99), being able to detect a range of Legionella concentrations between 101 and 104 cfu·mL−1 with a detection limit (LoD) of 4 cfu·mL−1.

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Recirculation versus flow-through rainbow trout laboratory Flavobacterium columnare challenge

Diseases of Aquatic Organisms ◽

10.3354/dao03487 ◽

2020 ◽

Vol 139 ◽

pp. 213-221

Author(s):

C Birkett ◽

R Lipscomb ◽

T Moreland ◽

T Leeds ◽

JP Evenhuis

Keyword(s):

Rainbow Trout ◽

Environmental Parameters ◽

Cumulative Effects ◽

Flavobacterium Columnare ◽

Replacement Rate ◽

Bacterial Concentration ◽

Water Replacement ◽

Dose Concentration ◽

Flow Through ◽

And Control

Flavobacterium columnare immersion challenges are affected by water-related environmental parameters and thus are difficult to reproduce. Whereas these challenges are typically conducted using flow-through systems, use of a recirculating challenge system to control environmental parameters may improve reproducibility. We compared mortality, bacterial concentration, and environmental parameters between flow-through and recirculating immersion challenge systems under laboratory conditions using 20 rainbow trout families. Despite identical dose concentration (1:75 dilution), duration of challenge, lot of fish, and temperature, average mortality in the recirculating system (42%) was lower (p < 0.01) compared to the flow-through system (77%), and there was low correlation (r = 0.24) of family mortality. Mean days to death (3.25 vs. 2.99 d) and aquaria-to-aquaria variation (9.6 vs. 10.4%) in the recirculating and flow-through systems, respectively, did not differ (p ≥ 0.30). Despite 10-fold lower water replacement rate in the recirculating (0.4 exchanges h-1) compared to flow-through system (4 exchanges h-1), differences in bacterial concentration between the 2 systems were modest (≤0.6 orders of magnitude) and inconsistent throughout the 21 d challenge. Compared to the flow-through system, dissolved oxygen during the 1 h exposure and pH were greater (p ≤ 0.02), and calcium and hardness were lower (p ≤ 0.03), in the recirculating system. Although this study was not designed to test effects of specific environmental parameters on mortality, it demonstrates that the cumulative effects of these parameters result in poor reproducibility. A recirculating immersion challenge model may be warranted to empirically identify and control environmental parameters affecting mortality and thus may serve as a more repeatable laboratory challenge model.

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Efficacy of Lysophosphatidylcholine as Direct Treatment in Combination with Colistin against Acinetobacter baumannii in Murine Severe Infections Models

Antibiotics ◽

10.3390/antibiotics10020194 ◽

2021 ◽

Vol 10 (2) ◽

pp. 194

Author(s):

Andrea Miró-Canturri ◽

Rafael Ayerbe-Algaba ◽

Manuel Enrique Jiménez-Mejías ◽

Jerónimo Pachón ◽

Younes Smani

Keyword(s):

Acinetobacter Baumannii ◽

Multidrug Resistant ◽

Experimental Models ◽

Antimicrobial Treatment ◽

Clinical Settings ◽

Monotherapy Group ◽

Bacterial Concentration ◽

Sepsis Model ◽

Severe Infections ◽

Stimulation Of

The stimulation of the immune response to prevent the progression of an infection may be an adjuvant to antimicrobial treatment. Here, we aimed to evaluate the efficacy of lysophosphatidylcholine (LPC) treatment in combination with colistin in murine experimental models of severe infections by Acinetobacter baumannii. We used the A. baumannii Ab9 strain, susceptible to colistin and most of the antibiotics used in clinical settings, and the A. baumannii Ab186 strain, susceptible to colistin but presenting a multidrug-resistant (MDR) pattern. The therapeutic efficacies of one and two LPC doses (25 mg/kg/d) and colistin (20 mg/kg/8 h), alone or in combination, were assessed against Ab9 and Ab186 in murine peritoneal sepsis and pneumonia models. One and two LPC doses combined with colistin and colistin monotherapy enhanced Ab9 and Ab186 clearance from spleen, lungs and blood and reduced mice mortality compared with those of the non-treated mice group in both experimental models. Moreover, one and two LPC doses reduced the bacterial concentration in tissues and blood in both models and increased mice survival in the peritoneal sepsis model for both strains compared with those of the colistin monotherapy group. LPC used as an adjuvant of colistin treatment may be helpful to reduce the severity and the resolution of the MDR A. baumannii infection.

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Concentrating Model Solutions and Fruit Juices Using CO2 Hydrate Technology and Its Quantitative Effect on Phenols, Carotenoids, Vitamin C and Betanin

Foods ◽

10.3390/foods10030626 ◽

2021 ◽

Vol 10 (3) ◽

pp. 626

Author(s):

Alexander Rudolph ◽

Amna El-Mohamad ◽

Christopher McHardy ◽

Cornelia Rauh

Keyword(s):

Vitamin C ◽

Food Production ◽

Bubble Column ◽

Hydrate Formation ◽

Fruit Juices ◽

Bubble Column Reactor ◽

High Concentration ◽

Model Solutions ◽

Concentration Potential ◽

Concentration Methods

Fruits have an important economic impact in the context of plant-based food production. The consumption of fruit juices, mostly produced from concentrates, is particularly noteworthy. Conventional concentration methods do not always enable a sustainable and gentle concentration. The innovative gas hydrate technology addresses this point with its energy-saving, gentle character, and high concentration potential. In this study, the concentration of fruit juices and model solutions using CO2 hydrate technology was investigated. To find a suitable operating point for hydrate formation in the used bubble column, the hydrate formation in a water–sucrose model solution was evaluated at different pressure and temperature combinations (1, 3, 5 °C and 32.5, 37.5, 40 bar). The degrees of concentration indicate that the bubble column reactor operates best at 37.5 bar and 3 °C. To investigate the gentle processing character of the hydrate technology, its quantitative effects on vitamin C, betanin, polyphenols, and carotenoids were analyzed in the produced concentrates and hydrates via HPLC and UV/VIS spectrophotometry. The results for fruit juices and model solutions imply that all examined substances are accumulated in the concentrate, while only small amounts remain in the hydrate. These amounts can be related to an inefficient separation process.

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Further In Vitro Assessment and Mid-Term Evaluation of Control Strategy of Xylella fastidiosa subsp. pauca in Olive Groves of Salento (Apulia, Italy)

Pathogens ◽

10.3390/pathogens10010085 ◽

2021 ◽

Vol 10 (1) ◽

pp. 85

Author(s):

Giuseppe Tatulli ◽

Vanessa Modesti ◽

Nicoletta Pucci ◽

Valeria Scala ◽

Alessia L’Aurora ◽

...

Keyword(s):

Control Strategy ◽

Xylella Fastidiosa ◽

In Planta ◽

Bacterial Concentration ◽

Infected Area ◽

Olive Groves ◽

Term Evaluation ◽

In Vitro Assessment ◽

Olive Trees

During recent years; Xylella fastidiosa subsp. pauca (Xfp) has spread in Salento causing relevant damage to the olive groves. Measures to contain the spreading of the pathogen include the monitoring of the areas bordering the so-called “infected” zone and the tree eradication in case of positive detection. In order to provide a control strategy aimed to maintain the tree productivity in the infected areas, we further evaluated the in vitro and in planta mid-term effectiveness of a zinc-copper-citric acid biocomplex. The compound showed an in vitro bactericidal activity and inhibited the biofilm formation in representative strains of X. fastidiosa subspecies, including Xfp isolated in Apulia from olive trees. The field mid-term evaluation of the control strategy assessed by quantitative real-time PCR in 41 trees of two olive groves of the “infected” area revealed a low concentration of Xfp over the seasons upon the regular spraying of the biocomplex over 3 or 4 consecutive years. In particular, the bacterial concentration lowered in July and October with respect to March, after six consecutive treatments. The trend was not affected by the cultivar and it was similar either in the Xfp-sensitive cultivars Ogliarola salentina and Cellina di Nardò or in the Xfp-resistant Leccino. Moreover, the scoring of the number of wilted twigs over the seasons confirmed the trend. The efficacy of the treatment in the management of olive groves subjected to a high pathogen pressure is highlighted by the yielded a good oil production

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Faecal bacteria in Perna perna (Linnaeus, 1758) (Mollusca: Bivalvia) for biomonitoring coastal waters and seafood quality

Brazilian Journal of Oceanography ◽

10.1590/s1679-87592010000700005 ◽

2010 ◽

Vol 58 (spe3) ◽

pp. 29-35 ◽

Cited By ~ 7

Author(s):

Diego Igawa Martinez ◽

Ana Júlia Fernandes Cardoso de Oliveira

Keyword(s):

Coastal Waters ◽

Microbiological Quality ◽

Perna Perna ◽

Clearance Rates ◽

Bacterial Concentration ◽

Allometric Relations ◽

The Mean ◽

Negative Impacts ◽

Faecal Bacteria

Urban development in coastal areas is intense and leads to the increase of sewage outfall and other negative impacts as consequences. Thus, stringent regulations establishing limits to the microbiological contamination of water and seafood are needed. The objective of this study is to evaluate the usefulness of Enterococci and Thermotolerant Coliform densities in the flesh of mussels Perna perna as an alternative tool for monitoring the microbiological quality of coastal waters. The study also considers allometric relations applied to clearance rates to understand rates of bacterial concentration. Bacterial loads obtained in mussels' flesh were from 50 to 4,300 times greater than in the water sampled in the vicinity of the mussels and some were considered inappropriate for consumption even when the water presented no restrictions. The mean clearance rate obtained for Enterococci retention was 317.7 ml h-1 and this rate (CR) is related to the mussels' size (L) by the equation CR = 28.3229L1.6421. The results showed that bacterial densities in the mussels' tissues may reflect chronic contamination of the environment and that clearance rates are important for taking the best decision in situations where, for example, it is desired to introduce mussels for aquaculture and the evaluation of the water concerned is required.

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Nitrification in activated sludge batch reactors is linked to protozoan grazing of the bacterial population

Canadian Journal of Microbiology ◽

10.1139/w05-069 ◽

2005 ◽

Vol 51 (9) ◽

pp. 791-799 ◽

Cited By ~ 24

Author(s):

Penny Petropoulos ◽

Kimberley A Gilbride

Keyword(s):

Activated Sludge ◽

Bacterial Population ◽

Grazing Pressure ◽

Nitrification Rate ◽

Batch Reactors ◽

Ammonia Oxidizing Bacteria ◽

Bacterial Concentration ◽

Batch Cultures ◽

Protozoan Grazing ◽

Swimming Bacteria

Protozoa feed upon free-swimming bacteria and suspended particles inducing flocculation and increasing the turnover rate of nutrients in complex mixed communities. In this study, the effect of protozoan grazing on nitrification was examined in activated sludge in batch cultures maintained over a 14-day period. A reduction in the protozoan grazing pressure was accomplished by using either a dilution series or the protozoan inhibitor cycloheximide. As the dilutions increased, the nitrification rate showed a decline, suggesting that a reduction in protozoan or bacterial concentration may cause a decrease in nitrification potential. In the presence of cycloheximide, where the bacterial concentration was not altered, the rates of production of ammonia, nitrite, and nitrate all were significantly lower in the absence of active protozoans. These results suggest that a reduction in the number or activity of the protozoans reduces nitrification, possibly by limiting the availability of nutrients for slow-growing ammonia and nitrite oxidizers through excretion products. Furthermore, the ability of protozoans to groom the heterotrophic bacterial population in such systems may also play a role in reducing interspecies competition for nitrification substrates and thereby augment nitrification rates.Key words: nitrification, activated sludge, protozoan grazing, ammonia-oxidizing bacteria, cycloheximide.

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