Implications of Adenylate Metabolism in Hygiene Assessment: A Review

AMP, ADP, and ATP Concentrations Differentially Affected by Meat Processing, Manufacturing, and Nonmeat Ingredients

Given its presence in a wide spectrum of soils relevant to food process hygiene, the biological metabolite adenosine triphosphate (ATP) is used as a target for surface hygiene assessments in food processing facilities. Yet, ample evidence demonstrates that ATP is depleted into adenosine di- (ADP) and monophosphate (AMP) homologs resulting in a loss of sensitivity for ATP-based hygiene assays. Yet, there are few studies that denote the degree of these shifts under routine processing conditions such as those encountered during various meat processing steps that may likely alter redox potential and adenosine profiles (e.g., tissue/cellular disruption, application of reducing additives, fermentation, or thermal treatment steps). In this study, meat samples were collected from homogenized beef tissue treated with nonmeat ingredients (sodium chloride, sodium nitrite, sodium erythorbate, natural smoke condensate, and sodium acid pyrophosphate) during manufacture at predetermined steps, and from retail meat products purchased from local markets. Concentrations of ATP, ADP, AMP, and AXP (sum concentration of all homologs) in a lab setting and in situ meat processing venues were determined and compared. Greater differences in AXP were seen during manufacture, where ADP generally comprised ∼90% as a mole fraction of AXP across all treatments, with the exception of the final cook step where AMP predominated. ATP concentrations averaged 2 log values lower than ADP and AMP. Adenosine profiles in retail samples followed similar trends with minimal ATP concentrations with ADP predominant in uncooked samples and AMP predominant in cooked samples. Resultingly, meat processing steps during product manufacture will alter AXP-reliant test sensitivities which should be considered when such technologies are utilized for hygiene verification in meat processing.

Hygiene Assessment of Buffalo Milking Parlours in Campania Region, Italy: A Preliminary Study by Using ATP Luminometry and Bacteriological Investigation

Careful cleaning of a milking parlour and its equipment is fundamental to guarantee good raw milk quality and prevent the dissemination of bacteria and improve animal welfare. This study aimed to investigate, using an ATP-bioluminescence assay and bacteriological analysis, the bacterial contamination of milking parlours on milking parlour surfaces of buffalo farms in the Campania Region, evaluating the seasonal dynamics during the year 2022. Eight farms were selected by the Italian ClassyFarm system, which assesses the level of animal welfare and biosecurity according to risk analysis. Before sampling, all dairy farm owners filled out a questionnaire on milking management, animal hygiene, and health. The questionnaires evidenced similar cleaning procedures but an absence of a standardised cleaning protocol among the different farms. ATP bioluminescence results evidenced similar levels of contamination in all the selected buffalo farms, and the season comparison showed no significant differences. A variation in the percentages of bacterial isolates during the different seasons was observed, with a higher prevalence of Enterobacteriaceae (38%) in summer. A small number of samples exhibited an absence of bacterial growth. Identifying bacteria is crucial for understanding the microorganisms present in the milking parlour, yet employing ATP luminometry could offer broad and accurate applications in buffalo milking parlours. In conclusion, the use of ATP bioluminescence for evaluating the hygiene of a buffalo milking parlour could represent a further important advancement in dairy farming technology.

Validity of luminometry and bacteriological tests for diagnosing intramammary infection at dry-off in dairy cows

The objective of this cross-sectional study was to estimate the validity of laboratory culture, Petrifilm and Tri-Plate on-farm culture systems, and luminometry to correctly identify IMI at dry-off in dairy cows, considering all tests as imperfect. From September 2020 until December 2021, we collected composite milk samples from cows before dry-off and divided them into 4 aliquots for the luminometry test, the Petrifilm (aerobic count), the Tri-Plate, and the laboratory culture. While we assessed multiple thresholds of relative light units (RLU) for the luminometry, we used thresholds of ≥100 cfu/mL for the laboratory culture, ≥ 50 cfu/mL for the Petrifilm, and ≥1 cfu for the Tri-Plate. We fitted Bayesian latent class analysis (LCA) models to estimate the sensitivity (Se) and specificity (Sp) for each test to identify IMI, with 95% credibility interval (BCI). Using different prevalence measures (0.30, 0.50, and 0.70), we calculated the predictive values (PV) and misclassification cost terms (MCT) at different false-negative to false-positive ratios (FN:FP). A total of 333 cows were enrolled in the study from one commercial Holstein herd. The validity of the luminometry was poor for all thresholds, with Se of 0.51 (95% BCI = 0.43-0.59) and Sp of 0.38 (95% BCI = 0.26-0.50) when using a threshold of ≥150 RLU. The laboratory culture had Se of 0.93 (95% BCI = 0.85-0.98) and Sp of 0.69 (95% BCI = 0.49-0.89), the Petrifilm had Se of 0.91 (95% BCI = 0.80-0.98) and Sp of 0.71 (95% BCI = 0.51-0.90), and the Tri-Plate had Se of 0.65 (95% BCI = 0.53-0.82) and Sp of 0.85 (95% BCI = 0.66-0.97). Bacteriological tests had good PVs, with comparable positive PV for all 3 tests, but lower negative PV for the Tri-Plate compared with the laboratory culture and the Petrifilm. For a prevalence of IMI of 0.30, all 3 tests had similar MCT, but for prevalence of 0.50 and 0.70, the Tri-Plate had higher MCT in scenarios where leaving a cow with IMI untreated is considered to have greater detrimental impacts than treating a healthy cow (i.e., FN:FP of 3:1). Our results showed that the bacteriological tests have adequate validity to diagnose IMI at dry-off, but the luminometry does not. We concluded that, while luminometry is not useful to identify IMI at dry-off, the Petrifilm and Tri-Plate tests performed similarly to the laboratory culture, depending on the prevalence and the importance of the FP and FN results.

Standardization and validation of ATP luminometry as a diagnostic tool to assess the cleanliness of feeding equipment in preweaning calves

The objective of this cross-sectional study was to standardize a reliable and repeatable swabbing technique using ATP luminometry (light emission proportional to the amount of ATP with result provided in relative light units [RLU]) to describe the cleanliness of various feeding equipment used for preweaning calves in dairy farms. A total of 7 Québec commercial dairy herds were selected conveniently. Following visual hygiene scoring, the cleanliness of every available piece of feeding equipment was assessed using direct surface swabbing for buckets and nipples with Hygiena UltraSnap swabs. A liquid rinsing technique was used for esophageal feeders, bottles, and automatic milk feeders (AMF) with UltraSnap, AquaSnap, and MicroSnap swabs. To validate direct swabbing technique of buckets, a stage within and between operators was realized, as well as a conventional bacterial culture. A total of 519 swab samples were obtained from 201 pieces of equipment. The median (interquartile range) contamination in RLU for a bottle, esophageal feeder, AMF, bucket and nipple was 2 (1;6), 2 (0;12), 52 (19;269), 886 (128;7,230) and 899 (142;6,928), respectively. The direct swabbing technique, which consists in swabbing directly the surface of an equipment, showed excellent correlation for intrarater reliability (intraclass correlation (ICC) = 0.93; 95% CI: 0.88-0.96). The interoperator (2 sessions with 3 different operators) reliability also showed high correlation (ICC = 0.88; 95% CI: 0.78-0.94 for the first session, and ICC = 0.89; 95% CI: 0.79-0.95 for the second session). Luminometer values were positively associated with the visual score of esophageal feeders, AMF and buckets. A positive correlation between bacterial culture and direct swabbing of buckets was also found for the UltraSnap (rs = 0.653; 95% CI: 0.283-0.873; P = 0.0003) and MicroSnap (rs = 0.569, 95% CI: 0.309-0.765; P = 0.002). This study describes a standardized and practical on-farm swabbing technique for assessing the hygienic status of feeding equipment by luminometry, which can be integrated in the investigation of preweaning dairy calves problems.

Comparison of coliform paper test and ATP bioluminescence assay for monitoring the disinfection of kitchen utensils in canteens of hebei, China

Background

Two common techniques used in canteen hygiene supervision, are the coliform paper assay, which is the standard method, and the adenosine triphosphate (ATP) bioluminescence method. The coliform paper assay requires the incubation of the sample, which is time-consuming and does not provide a real-time assessment. Meanwhile, the ATP bioluminescence assay can provide real-time kitchenware cleanliness data.

Objective

This study aimed to compare these two methods for evaluating the sanitary condition of kitchenware and explore whether the ATP bioluminescence assay can be used as a standard method in sanitary inspection.

Methods

In this study, the cluster random sampling method was used to sample kitchenware from six canteens in the Hebei province, China. Samples were, assessed through the coliform paper test and ATP bioluminescence assay.

Results

Kitchenware negative rates for the coliform paper method and the ATP test were 64.39% and 49.07%, respectively. The Escherichia coli positive detection rate grew steadily as the relative light units (RLU) value for the ATP technique increased. The kappa coefficient for the two methods was 0.549, indicating that the two methods yield relatively consistent results.

Conclusion

Although currently not considered a standard method, simply using ATP detection is advantageous for quick on-site detection in catering unit hygiene supervision.

Relationship between ATP Bioluminescence Measurements and Microbial Assessments in Studies Conducted in Food Establishments: A Systematic Literature Review and Meta-Analysis

ABSTRACT

Adherence to proper environmental cleaning practices is critical in food establishments. To validate cleanliness, cleaning practices should be routinely monitored, preferably by a rapid, reliable, and cost-effective method. The aim of this study was to determine whether a correlation exists between ATP bioluminescence measurements and selected microbial assessments in studies conducted in food establishments. A systematic literature review and meta-analysis was conducted using the principles of preferred reporting items for systematic reviews and meta-analyses. Twelve online databases and search engines were selected for the review. Peer-reviewed articles published in English between January 2000 and July 2020 were included in the search. From a total of 19 eligible studies, 3 that included Pearson correlation coefficients (r) between ATP bioluminescence measurements and microbial assessments were used for the meta-analysis calculations. Only the fixed-effect model produced a strong correlation because one value dominated the estimates: r = 0.9339 (0.9278, 0.9399). In contrast, both the random effects model, 0.2978 (0.24, 0.3471), and the mixed effects model, r = 0.3162 (-0.0387, 0.6711), indicated a weak relationship between ATP bioluminescence and microbial assessments, with no evidence of a strong correlation. The meta-analysis results indicated no sufficient evidence of a strong correlation between ATP bioluminescence measurements and microbial assessments when applied within food establishments. This lack of evidence for a strong correlation between the results of these two monitoring tools suggests that food establishments cannot depend on only one method. Yet, with immediate feedback and quantification of organic soiling, ATP bioluminescence could be an effective monitoring tool to use in food establishments.

HIGHLIGHTS

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

Use of ATP luminometry to assess the cleanliness of equipment used to collect and feed colostrum on dairy farms

The objective of this observational cross-sectional study was to describe the cleanliness of various equipment used for colostrum harvest and calf feeding procedures on dairy farms in Québec, Canada. The study was performed on 42 commercial dairy herds also enrolled in another study aiming to determine the transfer of passive immunity over a 14-mo period. Information on colostrum quality (using Brix value) and cleanliness (total aerobic and total coliform count) were recorded as well as various practices focused on colostrum-feeding equipment and preweaning period using a standard questionnaire. During the study period, colostrum and milk-feeding equipment cleanliness was assessed using direct surface swabbing with Hygiena Ultrasnap swabs. A total of 155 swab samples were obtained from 6 pieces of equipment. Adenosine triphosphate collected from the swabbed surface reacts with the luciferase solution present in the swab by bioluminescence, which is proportional to the quantity of ATP present and quantified as relative light units (RLU). The description of feed equipment cleanliness (defined as the maximal RLU found for a specific herd, dichotomized as <1,000 RLU vs. ≥1,000 RLU) was compared with the herds' descriptive characteristics, focusing on the first 2 components of a multiple correspondence analysis. The median (range) RLU for buckets used for colostrum harvest, bucket or bottle used for feeding, tube feeders, milking colostrum line, and internal surface of the nipples were 41 RLU (3-1,625 RLU), 78 RLU (<1-3,765 RLU), 29 RLU (<1-2,177 RLU), 83 RLU (<1-9,968 RLU), and 1,101 RLU (2-9,546 RLU), respectively. The first 2 components of multiple correspondence analysis explained 24.7% of data variances and were related to the farms' hygiene and health (13.0%) and feeding practices (11.7% of data variance). The maximal dichotomized luminometry value (<1,000 RLU or ≥1,000 RLU) was associated with hygiene and health dimension. This study gave promising results concerning the potential application of ATP luminometry for calf rearing practices assessment.

Rapid Hygiene Assay Sensitive to Cumulative Adenylate Homologues Exhibits Equal or Higher Frequencies of Soil Contamination Detection than Assay Limited to ATP Detection

ABSTRACT

Based upon regulatory and food industry-driven food safety standards, there is a need for rapid, accurate methods for assessing sanitary conditions. A commonly used assay is based on the assessment of the biochemical molecule adenosine triphosphate (ATP). A more recent assay, the total adenylate homologue-based (AXP) assay, targets the cumulative presence of ATP and its dephosphorylated homologues, adenosine diphosphate and adenosine monophosphate. Yet there is little information that compares the practical performance of these two assays. This work examined these two assay types with a comparative study in a grade A dairy foods processing plant and a licensed and inspected meat processing facility. A total of 1,920 concomitant analyses were conducted with main variables of assay type, processing facility type, and hygiene zone category. Statistical process control methodology was used to calculate 95% confidence control limits; data beyond those limits were considered contamination events. Results demonstrated that overall, the AXP assay detected contamination events approximately two times more often than the assay based on ATP only. This increase in the rate of contamination event detection was especially prevalent in the meat processing facility, where across all hygienic zones, there were 38 versus 85 contaminations events detected for the ATP and AXP assays, respectively. Across hygiene zones, the AXP data displayed either an equal or an increased incidence of soil detection compared with data from the ATP assay. This study provides applied evidence that assays solely dependent on ATP concentrations are less able to detect soil contaminants under conditions that favor ATP dephosphorylation reactions.

HIGHLIGHTS

Implementation of ATP and Microbial Indicator Testing for Hygiene Monitoring in a Tofu Production Facility Improves Product Quality and Hygienic Conditions of Food Contact Surfaces: A Case Study

Rapid ATP testing and microbiological enumeration are two common methods to monitor the effectiveness of cleaning and sanitation in the food industry. In this study, ATP testing and microbiological enumeration were implemented at a tofu production facility with the goal of improving cleaning practices and overall plant hygiene. Results from ATP monitoring were used to target areas of the production environment needing additional cleaning; ATP results were verified by microbiological enumeration of aerobic microorganisms, lactic acid bacteria, and yeasts and molds. Products from the production line were enumerated for the same microorganisms to determine if there was an impact on product quality. After the implementation of ATP monitoring and targeted cleaning, there was a statistically lower proportion of swabs that failed to meet established sanitary requirements for ATP, aerobic microorganisms, and lactic acid bacteria (p < 0.05), but not for yeasts and molds. ATP swabs and microbiological enumeration agreed on site hygiene 75.1% (72.3-77.7%, 95% CI) of the time. Product data indicated that unpasteurized finished products contained a statistically lower microbial load of the three groups of organisms following implementation of the practices (p < 0.05).ImportanceCleaning and sanitation are critical to maintaining safe and high-quality food production. Monitoring these activities is important to ensure proper execution of procedure and to assure compliance with regulatory guidelines. The results from monitoring activities can direct targeted cleaning of areas with higher risk of contamination from foodstuffs and microorganisms. The results of this study show that ATP monitoring and microbiological enumeration are useful tools to verify and improve the efficacy of cleaning and sanitation practices, which can have a positive impact on both plant hygiene and product quality. However, testing regimes and critical parameters will vary based on the product and facility.

Pyridinedicarboxylate-Tb(III) Complex-Based Luminescent Probes for ATP Monitoring

The pyridinedicarboxylate-Tb(III) complexes, TbPDC and Tb(PDC)₃, as luminescent probes for ATP monitoring have been conveniently prepared and characterized by FT-IR, ¹H-NMR, ESI-MS, UV-Vis, excitation, and emission spectroscopy. Interestingly, these two Tb(III) complexes were quenched by ATP by a similar mechanism via π-π stacking interaction between the chelating ligand and adenine moiety. The ability of luminescent probes applied for the determination of ATP in aqueous solution has been investigated. The dynamic ranges for the quantification of ATP are within 10-90 μM and 10-100 μM with detection limits of 7.62 and 11.20 μM for TbPDC and Tb(PDC)₃, respectively. The results demonstrated that these luminescent probes would be a potential candidate assay for ATP monitoring in hygiene assessment.