Variation in detection limits between bacterial growth phases and precision of an ATP bioluminescence system

The Influence of Chestnut Extract and Its Components on Antibacterial Activity against Staphylococcus aureus

Increasing antimicrobial resistance has caused a great interest in natural products as alternatives or potentiators of antibiotics. The objective of this study was to isolate individual tannins from crude chestnut extract as well as to determine the influence of both crude extracts (tannic acid extract, chestnut extract) and individual pure tannins (gallic acid, vescalin, vescalagin, castalin, castalagin) on the growth of Gram-positive Staphylococcus aureus bacteria. Their antibacterial activity was monitored by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) as well as the duration of the lag phase, growth rate and generation time. The effect of growth medium strength on the MIC of different tannins was also investigated. Bacterial growth was followed spectrophotometrically, and MIC values were determined by the microdilution method. The MIC values of various isolated compounds allowed us to determine the bioactive compounds and their contribution to antimicrobial activity. It was found that MIC values increase with increasing growth medium strength and that the lag phase lengthens with increasing tannin concentrations, while the growth rates decrease. Comparing the results of the two studies, the antimicrobial activity of tannins against S. aureus was not as pronounced as in the case of E. coli, which may indicate that a different mechanism of action is responsible for the antimicrobial effects of tannins on Gram-positive than on Gram-negative bacteria, or that a different mechanism is more pronounced.

Synthetic Microbial Surrogates Consisting of Lipid Nanoparticles Encapsulating DNA for the Validation of Surface Disinfection Procedures

Effective cleaning and disinfection procedures are an integral part of good manufacturing practice and in maintaining hygiene standards in health-care facilities. In this study, a method to validate such cleaning and disinfection procedures of surfaces was established employing lipid nanoparticles (LNPs) encapsulating DNA. It was possible to determine and distinguish between the physical cleaning effect (dilution) and the chemical cleaning effect (disintegration) on the LNPs during the cleaning and disinfection procedure (wiping). After treatment with 70 v % ethanol as a disinfectant and SDS solution as a cleaning agent, LNPs showed log₁₀ reductions of 4.5 and 4.0, respectively. These values are similar to the log₁₀ reductions exhibited by common bacteria, such as Escherichia coli and Serratia marcescens. Therefore, LNPs pose as useful tools for cleaning validation with advantages over the already existing tools and enable a separate detection of dilution and chemical disinfectant action.

Evaluation of L-Alanine Metabolism in Bacteria and Whole-Body Distribution with Bacterial Infection Model Mice

The World Health Organization has cautioned that antimicrobial resistance (AMR) will be responsible for an estimated 10 million deaths annually by 2050. To facilitate prompt and accurate diagnosis and treatment of infectious disease, we investigated the potential of amino acids for use as indicators of bacterial growth activity by clarifying which amino acids are taken up by bacteria during the various growth phases. In addition, we examined the amino acid transport mechanisms that are employed by bacteria based on the accumulation of labeled amino acids, Na⁺ dependence, and inhibitory effects using a specific inhibitor of system A. We found that ³H-L-Ala accurately reflects the proliferative activity of Escherichia coli K-12 and pathogenic EC-14 in vitro. This accumulation in E. coli could be attributed to the amino acid transport systems being different from those found in human tumor cells. Moreover, biological distribution assessed in infection model mice with EC-14 using ³H-L-Ala showed that the ratio of ³H-L-Ala accumulated in infected muscle to that in control muscle was 1.20. By detecting the growth activity of bacteria in the body that occurs during the early stages of infection by nuclear imaging, such detection methods may result in expeditious diagnostic treatments for infectious diseases.

Bacterial Surface Disturbances Affecting Cell Function during Exposure to Three-Compound Nanocomposites Based on Graphene Materials

Combating pathogenic microorganisms in an era of ever-increasing drug resistance is crucial. The aim of the study was to evaluate the antibacterial mechanism of three-compound nanocomposites that were based on graphene materials. To determine the nanomaterials' physicochemical properties, an analysis of the mean hydrodynamic diameter and zeta potential, transmission electron microscope (TEM) visualization and an FT-IR analysis were performed. The nanocomposites' activity toward bacteria species was defined by viability, colony forming units, conductivity and surface charge, cell wall integrity, ATP concentration, and intracellular pH. To ensure the safe usage of nanocomposites, the presence of cytokines was also analyzed. Both the graphene and graphene oxide (GO) nanocomposites exhibited a high antibacterial effect toward all bacteria species (Enterobacter cloacae, Listeria monocytogenes, Salmonella enterica, and Staphylococcus aureus), as well as exceeded values obtained from exposure to single nanoparticles. Nanocomposites caused the biggest membrane damage, along with ATP depletion. Nanocomposites that were based on GO resulted in lower toxicity to the cell line. In view of the many aspects that must be considered when investigating such complex structures as are three-component nanocomposites, studies of their mechanism of action are crucial to their potential antibacterial use.

ATP Bioluminescence Assay To Evaluate Antibiotic Combinations against Extensively Drug-Resistant (XDR) Pseudomonas aeruginosa

Time-kill curves are used to study antibiotic combinations, but the colony count method to obtain the results is time-consuming. The aim of the study was to validate an ATP assay as an alternative to the conventional colony count method in studies of antibiotic combinations. The cutoff point for synergy and bactericidal effect to categorize the results using this alternative method were determined in Pseudomonas aeruginosa. The ATP assay was performed using the GloMax 96 microplate luminometer (Promega), which measures bioluminescence in relative light units (RLU). To standardize this assay, background, linearity, and the detection limit were determined with one strain each of multidrug-resistant P. aeruginosa and Klebsiella pneumoniae. Twenty-four-hour time-kill curves were performed in parallel by both methods with 12 strains of P. aeruginosa. The conventional method was used as a “gold” standard to establish the pharmacodynamic cutoff points in the ATP method. Normal saline solution was established as washing/dilution medium. RLU signal correlated with CFU when the assay was performed within the linear range. The categorization of the pharmacodynamic parameters using the ATP assay was equivalent to that of the colony count method. The bactericidal effect and synergy cutoff points were 1.348 (93% sensitivity, 81% specificity) and 1.065 (95% sensitivity, 89% specificity) log RLU/mL, respectively. The ATP assay was useful to determine the effectiveness of antibiotic combinations in time-kill curves. This method, less laborious and faster than the colony count method, could be implemented in the clinical laboratory workflow.

IMPORTANCE Combining antibiotics is one of the few strategies available to overcome infections caused by multidrug-resistant bacteria. Time-kill curves are usually performed to evaluate antibiotic combinations, but obtaining results is too laborious to be routinely performed in a clinical laboratory. Our results support the utility of an ATP measurement assay using bioluminescence to determine the effectiveness of antibiotic combinations in time-kill curves. This method may be implemented in the clinical laboratory workflow as it is less laborious and faster than the conventional colony count method. Shortening the obtention of results to 24 h would also allow an earlier guided combined antibiotic treatment.

A Comprehensive Analysis of ATP Tests: Practical Use and Recent Progress in the Total Adenylate Test for the Effective Monitoring of Hygiene

ABSTRACT

Rapid hygiene monitoring tests based on the presence of ATP have been widely used in the food industry to ensure that adequate cleanliness is maintained. In this study, the practical applications and limitations of these tests and recent technological progress for facilitating more accurate control were evaluated. The presence of ATP on a surface indicates improper cleaning and the presence of contaminants, including organic debris and bacteria. Food residues are indicators of insufficient cleaning and are direct hazards because they may provide safe harbors for bacteria, provide sources of nutrients for bacterial growth, interfere with the antimicrobial activity of disinfectants, and support the formation of biofilms. Residues of allergenic foods on a surface may increase the risk of allergen cross-contact. However, ATP tests cannot detect bacteria or allergenic proteins directly. To ensure efficient use of commercially available ATP tests, in-depth knowledge is needed regarding their practical applications, methods for determining pass-fail limits, and differences in performance. Conventional ATP tests have limitations due to possible hydrolysis of ATP to ADP and AMP, which further hinders the identification of food residues. To overcome this problem, a total adenylate test was developed that could detect ATP+ADP+AMP (A3 test). The A3 test is suitable for the detection of adenylates from food residues and useful for verification of hygiene levels. The A3 test in conjunction with other methods, such as microorganism culture and food allergen tests, may be a useful strategy for identifying contamination sources and facilitating effective hygiene management.

HIGHLIGHTS

Removal of peptidoglycan and inhibition of active cellular processes leads to daptomycin tolerance in Enterococcus faecalis

Daptomycin is a cyclic lipopeptide antibiotic used in the clinic for treatment of severe enterococcal infections. Recent reports indicate that daptomycin targets active cellular processes, specifically, peptidoglycan biosynthesis. Within, we examined the efficacy of daptomycin against Enterococcus faecalis under a range of environmental growth conditions including inhibitors that target active cellular processes. Daptomycin was far less effective against cells in late stationary phase compared to cells in exponential phase, and this was independent of cellular ATP levels. Further, the addition of either the de novo protein synthesis inhibitor chloramphenicol or the fatty acid biosynthesis inhibitor cerulenin induced survival against daptomycin far better than controls. Alterations in metabolites associated with peptidoglycan synthesis correlated with protection against daptomycin. This was further supported as removal of peptidoglycan induced physiological daptomycin tolerance, a synergistic relation between daptomycin and fosfomycin, an inhibitor of the fist committed step peptidoglycan synthesis, was observed, as well as an additive effect when daptomycin was combined with ampicillin, which targets crosslinking of peptidoglycan strands. Removal of the peptidoglycan of Enterococcus faecium, Staphylococcus aureus, and Bacillus subtilis also resulted in significant protection against daptomycin in comparison to whole cells with intact cell walls. Based on these observations, we conclude that bacterial growth phase and metabolic activity, as well as the presence/absence of peptidoglycan are major contributors to the efficacy of daptomycin.

Comparative study of rapid ATP bioluminescence assay and conventional plate count method for development of rapid disinfecting activity test

Antimicrobial activity is tested when developing disinfectants, pharmaceutical products, cosmetics, and many other consumer products. However, the plate count method, the conventional way to count the number of microorganisms, needs several days of culture. Consequently, a means of rapid microbial detection is strongly desired to replace this method. We have already developed a rapid and sensitive microbial adenosine triphosphate (ATP) detection system utilizing ATP bioluminescence, which can quantify microbial ATP within 1 h. To apply this technique to antibacterial activity tests, the ATP method should be proved equal or superior to the conventional method. In this study, we conducted disinfectant activity tests comparing the ATP method and the plate count method, using polyhexamethylene biguanide (PHMB) in different concentrations (0-10 ppm) as a model disinfectant against Staphylococcus aureus and Aspergillus brasiliensis. We found that the log reduction of intracellular ATP had a positive correlation with the log reduction of the plate count. Moreover, the ATP method was able to distinguish different conditions of injured microbial cells that were observed using scanning electron microscopy, whereas colony counting detects only culturable cells. The ATP method is thus a rapid and useful alternative to the conventional method in the field of antimicrobial activity testing.

Quantities of Adenylate Homologues (ATP+ADP+AMP) Change over Time in Prokaryotic and Eukaryotic Cells

Rapid assays for the assessment of the hygienic state of surfaces in food and medical industries include the use of technologies designed to detect the presence of the metabolite ATP. ATP is a critical metabolite and energy source for most living organisms; therefore, the presence of ATP can be an indicator of surface hygiene based on the presence of soil or food residues associated with inadequate cleaning. The concentrations of ATP vary based on an organism's metabolic state, thus potentially influencing the sensitivity of ATP-based assays. However, little has been published detailing the quantitative changes of ATP to the adenylate homologues ADP and AMP nor the quantitative and cumulative fate of these homologues over time as the metabolic state remains in flux. The objective of this study was to quantify the individual and cumulative (AXP) concentrations of these three adenylate homologues over defined time periods in selected eukaryotic tissue and prokaryotic cell cultures of significance to hygiene. ATP concentrations differed substantially across these selected variables of time and source. The 1- to 3-log reductions in ATP concentrations over time were highly affected by organism type. In general, ADP became the predominate adenylate in eukaryotic tissue, and AMP was the predominate adenylate in the prokaryotic cells at later time points in each study. Total AXP concentrations dropped in general, reflective primarily of the loss of ATP. The results of ATP-based techniques for hygiene surveillance will vary as a function of the amount of cellular material present and the metabolic state of such material.

Overall Quality and Sanitation Evaluation of Fish Stores at Local Markets in Ibagué, Tolima, Colombia

HIGHLIGHTS

Results indicated ineffective cleaning and sanitation of surfaces and utensils. High incidence of coliforms indicated inadequate product handling. The low compliance with regulations was corroborated by luminometry results. Deficiencies in hygiene practices could be indicative of potential food safety problems.

Evaluation of ATP bioluminescence-based methods for hygienic assessment in fish industry

AIMS

To evaluate ATP bioluminescence-based hygiene monitoring systems under conditions relevant to fish processing environments.

METHODS AND RESULTS

The ATP bioluminescence of fish fractions that are potentially present after insufficient cleaning of fish processing environments was determined. Different fractions and interfering substances representing the stages from slaughtering to smoking were prepared and measured using two different commercial systems (SystemSURE Plus and Clean-Trace). ATP bioluminescence was quenched by acidic liquid smoke and by sodium chloride even at concentrations as low as 0·9% NaCl. Large variations were observed between different types of trout homogenates: the ATP bioluminescence from raw belly fat homogenate was 100-1000 times lower than for trout blood. There were about a 1000-fold lower ATP bioluminescence in raw compared to heat-treated fractions from trout, with the exception of blood. The bioluminescence from Listeria monocytogenes was very low. Results from fish processing plants supported the laboratory findings.

CONCLUSIONS

The output from ATP-monitoring instruments depends on the nature of fish soil present, as well as the presence of sodium chloride and low pH. This may lead to considerable under- or overestimation of the level of organic soil.

SIGNIFICANCE AND IMPACT OF THE STUDY

ATP bioluminescence instruments are widely used by the fish industry for monitoring hygiene. The monitoring method will only give valuable information about the hygiene if critical limits are set after a validation period, distinguishing between areas with different types of soil and between different hygiene zones.

Rapid Antibiotic Combination Testing for Carbapenem-Resistant Gram-Negative Bacteria within Six Hours Using ATP Bioluminescence

To guide the timely selection of antibiotic combinations against carbapenem-resistant Gram-negative bacteria (CR-GNB), an in vitro test with a short turnaround time is essential. We developed an in vitro ATP bioluminescence assay to determine effective antibiotic combinations against CR-GNB within 6 h. We tested 42 clinical CR-GNB strains (14 Acinetobacter baumannii, 14 Pseudomonas aeruginosa, and 14 Klebsiella pneumoniae strains) against 74 single antibiotics and two-antibiotic combinations. Bacteria (approximately 5 log₁₀ CFU/ml) were incubated with an antibiotic(s) at 35°C; ATP bioluminescence was measured at 6 h and 24 h; and the measurements were compared to viable counts at 24 h. Receiver operating characteristic (ROC) curves were used to determine the optimal luminescence thresholds (T_RLU) for distinguishing between inhibitory and noninhibitory combinations. The areas under the 6-h and 24-h ROC curves were compared using the DeLong method. Prospective validation of the established thresholds was conducted using 18 additional CR-GNB. The predictive accuracy of T_RLU for the 6-h ATP bioluminescence assay was 77.5% when all species were analyzed collectively. Predictive accuracies ranged from 73.7% to 82.7% when each species was analyzed individually. Upon comparison of the areas under the 6-h and 24-h ROC curves, the 6-h assay performed significantly better than the 24-h assay (P < 0.01). Predictive accuracy remained high upon prospective validation of the 6-h ATP assay (predictive accuracy, 79.8%; 95% confidence interval [CI], 77.6 to 81.9%), confirming the external validity of the assay. Our findings indicate that our 6-h ATP bioluminescence assay can provide guidance for prospective selection of antibiotic combinations against CR-GNB in a timely manner and may be useful in the management of CR-GNB infections.

Rapid Detection of Microbial Contamination Using a Microfluidic Device

A portable kinetics fluorometer is developed to detect viable cells which may be contaminating various samples. The portable device acts as a single-excitation, single-emission photometer that continuously measures fluorescence intensity of an indicator dye and plots it. The slope of the plot depends on the number of colony forming units per milliliter. The device uses resazurin as the indicator dye. Viable cells reduce resazurin to resorufin, which is more fluorescent. Photodiode is used to detect fluorescence change. The photodiode generated current proportional to the intensity of the light that reached it, and an op-amp is used in a transimpedance differential configuration to ensure amplification of the photodiode's signal. A microfluidic chip is designed specifically for the device. It acts as a fully enclosed cuvette, which enhances the resazurin reduction rate. In tests, the E. coli-containing media are injected into the microfluidic chip and the device is able to detect the presence of E. coli in LB media based on the fluorescence change that occurred in the indicator dye. The device provides fast, accurate, and inexpensive means to optical detection of the presence of viable cells and could be used in the field in place of more complex methods, i.e., loop-meditated isothermal amplification of DNA (LAMP) to detect bacteria in pharmaceutical samples (Jimenez et al., J Microbiol Methods 41(3):259-265, 2000) or measuring the intrinsic fluorescence of the bacterial or yeast chromophores (Estes et al., Biosens Bioelectron 18(5):511-519, 2003).

Bioluminescence assay for cell viability

Theoretical aspects of the adenosine triphosphate bioluminescence assay based on the use of the firefly luciferin-luciferase system are considered, as well as its application for assessing cell viability in microbiology, sanitation, medicine, and ecology. Various approaches for the analysis of individual or mixed cultures of microorganisms are presented, and capabilities of the method for investigation of biological processes in live cells including necrosis, apoptosis, as well as for investigation of the dynamics of metabolism are described.

Toward a microbial Neolithic revolution in buildings

The Neolithic revolution--the transition of our species from hunter and gatherer to cultivator--began approximately 14,000 years ago and is essentially complete for macroscopic food. Humans remain largely pre-Neolithic in our relationship with microbes but starting with the gut we continue our hundred-year project of approaching the ability to assess and cultivate benign microbiomes in our bodies. Buildings are analogous to the body and it is time to ask what it means to cultivate benign microbiomes in our built environment. A critical distinction is that we have not found, or invented, niches in buildings where healthful microbial metabolism occurs and/or could be cultivated. Key events affecting the health and healthfulness of buildings such as a hurricane leading to a flood or a burst pipe occur only rarely and unpredictably. The cause may be transient but the effects can be long lasting and, e.g., for moisture damage, cumulative. Non-invasive "building tomography" could find moisture and "sentinel microbes" could record the integral of transient growth. "Seed" microbes are metabolically inert cells able to grow when conditions allow. All microbes and their residue present actinic molecules including immunological epitopes (molecular shapes). The fascinating hygiene and microbial biodiversity hypotheses propose that a healthy immune system requires exposure to a set of microbial epitopes that is rich in diversity. A particular conjecture is that measures of the richness of diversity derived from microbiome next-generation sequencing (NGS) can be mechanistically coupled to--rather than merely correlated with some measures of--human health. These hypotheses and conjectures inspire workers and funders but an alternative is also consequent to the first Neolithic revolution: That the genetic uniformity of contemporary foods may also decrease human exposure to molecular biodiversity in a heath-relevant manner. Understanding the consequences--including the unintended consequences of the first Neolithic revolution--will inform and help us benignly implement the second--the microbial--Neolithic revolution.

Real time detection of live microbes using a highly sensitive bioluminescent nitroreductase probe

A highly sensitive and selective nitroreductase probe, showing a rapid and strong bioluminescence enhancement (>100-fold in 5 minutes), and its initial application in the real time detection of both Gram positive and Gram negative live bacteria and monitoring of their growth has been reported.