Measurement uncertainty evaluation and risk of false conformity assessment for microbial enumeration tests.

Microbial enumeration tests are widely used to assess the microbiological quality of non-sterile pharmaceutical products. Despite of all efforts to guarantee the reliability of microbial enumeration tests, there will always be an uncertainty associated with the measured values, which can lead to false conformity/non-conformity decisions. In this work, we evaluated the measurement uncertainty using a bottom-up approach and estimate the consumer's or producer's risk due to the measurement uncertainty. Three main sources of uncertainty were identified and quantified: dilution factor, plated volume, and microbial plate counts. The contribution of these sources of uncertainty depends on the measured value of microbial load in pharmaceutical products. The contribution of dilution factor and plated volume uncertainties increase with an increase of measured value, while the contribution of microbial plate count uncertainty decreases with an increase of measured value. The overall uncertainty values were expressed as uncertainty factors, which provide an asymmetric 95% level confidence level of microbial load in pharmaceutical products. In addition, the risk of false conformity/non-conformity decisions due to measurement uncertainty was assess using Monte Carlo method. When the measured value is close to the upper specification limit and/or the measurement uncertainty is large, the risk of false conformity/non-conformity decisions may be significantly high. Thus, we conclude that the use of uncertainty factor in the conformity/non-conformity assessment is important to guarantee the reliability of microbial enumeration test results and to support decision-making.

A Possible Flow Cytometry-Based Viability and Vitality Assessment Protocol for Pathogenic Vibrio cholerae O1 and O139 Postexposure to Simulated Gastric Fluid.

During the intake of contaminated water, for diarrheal disease to occur, Vibrio cholerae must survive through the bactericidal digestive secretion of gastric fluid during passage through the stomach. Determining the viability of these bacteria is challenging, with the standard cultivation methods for viability being time-consuming and unable to culture cells that may still function accordingly. This study assessed the use of enzyme action and membrane integrity as alternatives for determining vitality and viability, respectively, in gastric acid-stressed pathogenic Vibrio cholerae O1 and O139, using fluorescent probes thiazole orange (TO) for viability based on membrane integrity, carboxyfluorescein diacetate (CFDA) with acetoxymethyl ester (AM) for vitality based on metabolic activity, and propidium iodide (PI) for cell death/damage due to loss of membrane integrity, with flow cytometry. Simulated gastric fluid-treated bacterial cells were labelled with blends of TO+PI and CFDA-AM+PI, and these stained cells were separated into heterologous populations based on their fluorescence signal. The gastric acid exposed cells presented with high green fluorescence signals after staining with the metabolic probe CFDA-AM, which indicated intact (live) cells due to being metabolically active, whereas when the same cells were stained with the DNA probe (TO), these appeared to be in a "stressed state" due to loss of membrane integrity. Damaged cells (dead cells) showed high red fluorescence levels after staining with PI probe. The use of flow cytometry with fluorescent probes is a favorable method for evaluating the vitality and viability of bacteria when cells are labelled with a combination of CFDA-AM+PI.

Interventions to reduce contaminated aerosols produced during dental procedures for preventing infectious diseases.

BACKGROUND: Many dental procedures produce aerosols (droplets, droplet nuclei and splatter) that harbour various pathogenic micro-organisms and may pose a risk for the spread of infections between dentist and patient. The COVID-19 pandemic has led to greater concern about this risk. OBJECTIVES: To assess the effectiveness of methods used during dental treatment procedures to minimize aerosol production and reduce or neutralize contamination in aerosols. SEARCH METHODS: Cochrane Oral Health's Information Specialist searched the following databases on 17 September 2020: Cochrane Oral Health's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (in the Cochrane Library, 2020, Issue 8), MEDLINE Ovid (from 1946); Embase Ovid (from 1980); the WHO COVID-19 Global literature on coronavirus disease; the US National Institutes of Health Trials Registry (ClinicalTrials.gov); and the Cochrane COVID-19 Study Register. We placed no restrictions on the language or date of publication. SELECTION CRITERIA: We included randomized controlled trials (RCTs) and controlled clinical trials (CCTs) on aerosol-generating procedures (AGPs) performed by dental healthcare providers that evaluated methods to reduce contaminated aerosols in dental clinics (excluding preprocedural mouthrinses). The primary outcomes were incidence of infection in dental staff or patients, and reduction in volume and level of contaminated aerosols in the operative environment. The secondary outcomes were cost, accessibility and feasibility. DATA COLLECTION AND ANALYSIS: Two review authors screened search results, extracted data from the included studies, assessed the risk of bias in the studies, and judged the certainty of the available evidence. We used mean differences (MDs) and 95% confidence intervals (CIs) as the effect estimate for continuous outcomes, and random-effects meta-analysis to combine data. We assessed heterogeneity. MAIN RESULTS: We included 16 studies with 425 participants aged 5 to 69 years. Eight studies had high risk of bias; eight had unclear risk of bias. No studies measured infection. All studies measured bacterial contamination using the surrogate outcome of colony-forming units (CFU). Two studies measured contamination per volume of air sampled at different distances from the patient's mouth, and 14 studies sampled particles on agar plates at specific distances from the patient's mouth. The results presented below should be interpreted with caution as the evidence is very low certainty due to heterogeneity, risk of bias, small sample sizes and wide confidence intervals. Moreover, we do not know the 'minimal clinically important difference' in CFU. High-volume evacuator Use of a high-volume evacuator (HVE) may reduce bacterial contamination in aerosols less than one foot (~ 30 cm) from a patient's mouth (MD -47.41, 95% CI -92.76 to -2.06; 3 RCTs, 122 participants (two studies had split-mouth design); very high heterogeneity I² = 95%), but not at longer distances (MD -1.00, -2.56 to 0.56; 1 RCT, 80 participants). One split-mouth RCT (six participants) found that HVE may not be more effective than conventional dental suction (saliva ejector or low-volume evacuator) at 40 cm (MD CFU -2.30, 95% CI -5.32 to 0.72) or 150 cm (MD -2.20, 95% CI -14.01 to 9.61). Dental isolation combination system One RCT (50 participants) found that there may be no difference in CFU between a combination system (Isolite) and a saliva ejector (low-volume evacuator) during AGPs (MD -0.31, 95% CI -0.82 to 0.20) or after AGPs (MD -0.35, -0.99 to 0.29). However, an 'n of 1' design study showed that the combination system may reduce CFU compared with rubber dam plus HVE (MD -125.20, 95% CI -174.02 to -76.38) or HVE (MD -109.30, 95% CI -153.01 to -65.59). Rubber dam One split-mouth RCT (10 participants) receiving dental treatment, found that there may be a reduction in CFU with rubber dam at one-metre (MD -16.20, 95% CI -19.36 to -13.04) and two-metre distance (MD -11.70, 95% CI -15.82 to -7.58). One RCT of 47 dental students found use of rubber dam may make no difference in CFU at the forehead (MD 0.98, 95% CI -0.73 to 2.70) and occipital region of the operator (MD 0.77, 95% CI -0.46 to 2.00). One split-mouth RCT (21 participants) found that rubber dam plus HVE may reduce CFU more than cotton roll plus HVE on the patient's chest (MD -251.00, 95% CI -267.95 to -234.05) and dental unit light (MD -12.70, 95% CI -12.85 to -12.55). Air cleaning systems One split-mouth CCT (two participants) used a local stand-alone air cleaning system (ACS), which may reduce aerosol contamination during cavity preparation (MD -66.70 CFU, 95% CI -120.15 to -13.25 per cubic metre) or ultrasonic scaling (MD -32.40, 95% CI - 51.55 to -13.25). Another CCT (50 participants) found that laminar flow in the dental clinic combined with a HEPA filter may reduce contamination approximately 76 cm from the floor (MD -483.56 CFU, 95% CI -550.02 to -417.10 per cubic feet per minute per patient) and 20 cm to 30 cm from the patient's mouth (MD -319.14 CFU, 95% CI - 385.60 to -252.68). Disinfectants ‒ antimicrobial coolants Two RCTs evaluated use of antimicrobial coolants during ultrasonic scaling. Compared with distilled water, coolant containing chlorhexidine (CHX), cinnamon extract coolant or povidone iodine may reduce CFU: CHX (MD -124.00, 95% CI -135.78 to -112.22; 20 participants), povidone iodine (MD -656.45, 95% CI -672.74 to -640.16; 40 participants), cinnamon (MD -644.55, 95% CI -668.70 to -620.40; 40 participants). CHX coolant may reduce CFU more than povidone iodine (MD -59.30, 95% CI -64.16 to -54.44; 20 participants), but not more than cinnamon extract (MD -11.90, 95% CI -35.88 to 12.08; 40 participants). AUTHORS' CONCLUSIONS: We found no studies that evaluated disease transmission via aerosols in a dental setting; and no evidence about viral contamination in aerosols. All of the included studies measured bacterial contamination using colony-forming units. There appeared to be some benefit from the interventions evaluated but the available evidence is very low certainty so we are unable to draw reliable conclusions. We did not find any studies on methods such as ventilation, ionization, ozonisation, UV light and fogging. Studies are needed that measure contamination in aerosols, size distribution of aerosols and infection transmission risk for respiratory diseases such as COVID-19 in dental patients and staff.

An optimized algorithm with improved turnaround time for detection of carbapenemase-producing Enterobacterales using the NG Test CARBA 5 in a routine laboratory.

Introduction. Rapid and reliable detection of carbapenemase-producing Enterobacterales (CPE) from surveillance cultures is critical in supporting a good infection control programme. We implemented a new algorithm for CPE detection incorporating the NG Test CARBA 5 in January 2019.Aim. Our goals were to compare turnaround time (TAT), costs and staff requirements between the old and new algorithm, and to evaluate the performance of the CARBA 5 test directly on colonies grown on CARBA Smart agar.Methodology. We analysed and compared the TAT of CPE surveillance cultures processed using the old and new CPE screening algorithm. The total actual reagent costs and staff requirements for the new CPE algorithm were compared with the estimated costs and staff requirements of the old CPE algorithm.Results. Of 197 isolates included in the evaluation of the new algorithm, 64 were positive for carbapenemases by both CARBA 5 and Xpert Carba-R assay. Of the 133 that were negative, two were found to harbour NDM and IMI genotypes. Significant improvements in TAT were achieved with 88.7 % of cultures with CPE, reported on the same day as growth was observed on CARBA Smart agar compared to none in the old algorithm. The new algorithm incurred lower costs and, based on our workload, the new algorithm is estimated to save 28.9 man-hours annually.Conclusion. CARBA 5 performs well on colonies growing on CARBA Smart agar and significant improvements in TAT can be achieved without incurring additional costs or staff requirements.

Computer Vision Approach for the Determination of Microbial Concentration and Growth Kinetics Using a Low Cost Sensor System.

The measurement of microbial contamination is of primary importance in different fields, from environmental monitoring to food safety and clinical analysis. Today, almost all microbiology laboratories make microbial concentration measurements using the standard Plate Count Technique (PCT), a manual method that must be performed by trained personnel. Since manual PCT analysis can result in eye fatigue and errors, in particular when hundreds of samples are processed every day, automatic colony counters have been built and are commercially available. While quick and reliable, these instruments are generally expensive, thus, portable colony counters based on smartphones have been developed and are of low cost but also not accurate as the commercial benchtop instruments. In this paper, a novel computer vision sensor system is presented that can measure the microbial concentration of a sample under test and also estimate the microbial growth kinetics by monitoring the colonies grown on a Petri dish at regular time intervals. The proposed method has been in-house validated by performing PCT analysis in parallel under the same conditions and using these results as a reference. All the measurements have been carried out in a laboratory using benchtop instruments, however, such a system can also be realized as an embedded sensor system to be deployed for microbial analysis outside a laboratory environment.

Viability assessment of Bifidobacterium longum ATCC 15707 on non-dairy foods using quantitative fluorescence microscopy.

This study demonstrates an effective technique for separating and purifying viable bacteria from samples that interfere with viability staining. The viability of Bifidobacterium longum ATCC 15707 was assessed using Percoll Buoyant Density Gradient Centrifugation (PBDC) to separate bacteria from complex non-dairy food matrices and Quantitative Fluorescence Microscopy (QFM) to determine individual cells using LIVE/DEAD BacLight bacterial viability staining. Water agar (3%) was used to retain cells of B. longum and offered a lower fluorescence background with BacLight viability staining, compared with fixation on polycarbonate (PC) black membrane. The effect of drying temperatures and non-dairy foods on viability of B. longum was assessed. B. longum coated on oat, peanut or raisin was separated by filtration, low- and high-speed centrifugation, flotation and sedimentation buoyant density centrifugation. Purified cells were subsequently deposited on water agar for rehydration followed by LIVE/DEAD BacLight viability staining and enumeration. Conventional plate counting was also conducted to compare viability results. Finally, this method was applied to assess cell membrane damages of B. longum incorporated onto non-dairy foods during 24 h drying. Furthermore, viability assessment of B. longum coated onto oat, peanut, or raisin was much lower by plate counting compared to viability staining. Drying appeared to have a greater impact when viability was assessed by plate counting compared to viability staining. IMPORTANCE: Enumeration of viable beneficial bacteria from function foods presents a significant bottleneck for product development and quality control. Interference with microscopic and/or fluorescent techniques by ingredients, time required to incubate plated microbes, and the transient nature of the colony forming unit make rapid assessment of viable bacteria difficult. Viability assessment of Bifidobacterium longum ATCC 15707 by Percoll Buoyant Density Gradient Centrifugation with LIVE/DEAD BacLight viability staining on water agar (3%) was in agreement with serial dilution enumeration. Without the need for incubation viability assessment by staining provided a more rapid means to assess the impact of drying on the viability of B. longum coated onto oat, peanut or raisin.

Comparative assessment of methicillin resistant Staphylococcus aureus diagnostic assays for use in resource-limited settings.

BACKGROUND: The rise of methicillin-resistant Staphylococcus aureus (MRSA) is a global health concern. Paucity of data on MRSA carriage prevalence and diagnostic methods in resource-limited settings hampers efforts to define the problem and plan an appropriate response. Additionally, high variability in cost and logistical characteristics of MRSA screening methods may impede infection control efforts. We compared the performance of locally-available chromogenic agar BD CHROMagar MRSA II and two PCR-based assays (Hain GenoQuick MRSA and Cepheid Xpert SA Complete) for the detection of asymptomatic MRSA carriage in nasal swabs. RESULTS: During 2015, we enrolled 500 patients from five hospital wards at a Ugandan regional referral hospital. We found 30% prevalence of methicillin-sensitive Staphylococcus aureus (MSSA) nasal carriage, and 5.4% MRSA nasal carriage prevalence. Compared to a composite reference standard defined as a positive test result on any one of the three assays, Hain GenoQuick MRSA demonstrated the highest sensitivity (96%) followed by direct plating on CHROMagar at (70%), with the lowest sensitivity observed with Xpert SA Complete (52%). Cepheid Xpert provided the most rapid results (< 1 h) but was the most expensive (US $45-50/test). Substantially more labor was required for the Hain GenoQuick MRSA compared to Xpert SA Complete or CHROMagar tests. CONCLUSION: MRSA nasal carriage prevalence rates were low, and high diagnostic sensitivity was achieved using Hain GenoQuick MRSA. Chromogenic media had significantly lower sensitivity, but may represent a viable local option given its lower cost compared to PCR-based assays.

Assessment of two selective agar media to isolate colistin-resistant bovine Escherichia coli: Correlation with minimal inhibitory concentration and presence of mcr genes.

The identification of colistin-resistant enterobacteria in veterinary medicine is impaired by the absence of first-line reliable phenotypic assay. The purpose of this study was to assess two selective agar media for the detection of colistin-resistant bovine pathogenic Escherichia coli. A total of 158 E. coli (46 R , 96 I and 16 S at the disk diffusion assay) isolated between 2013 and 2018 from <3 month-old calves suffering enteritis or septicaemia, were (i) tested by the broth dilution assay to determine colistin Minimal Inhibitory Concentrations (MIC); (ii) streaked on CHROMID® Colistin_R and CHROMagar™ COL-APSE agar plates; (iii) submitted to a pentaplex PCR to identify the presence of mcr-1 to mcr-5 genes. Of the 92 E. coli growing on both agar media, 90 had a MIC > 2.0 µg/ml as had the 3 E. coli that grew only on the CHROMID® Colistin_R agar medium and one E. coli that grew on neither agar media. Therefore, the positive predictive values of the CHROMID® Colistin_R and CHROMagar™ COL-APSE agar media were both 0.98 whereas their negative predictive values were 0.98 and 0.94, respectively. Also noteworthy 43 of the 46 R isolates had a MIC > 2.0 µg/ml and grew on both selective media as did half of the 96 I isolates and only 1 of the S isolates. Conversely, only 30 of the 90 isolates that grew on both agar media and with a MIC > 2.0 µg/ml tested positive for the mcr-1 or mcr-2 genes with the pentaplex PCR. These two selective agar media can be used to reliably detect colistin-resistant E. coli. Positive growth was highly correlated with R results at the disk diffusion assay, but not with the presence of mcr genes.

Assessment of stability and fluctuations of cultured lower airway bacterial communities in people with cystic fibrosis.

BACKGROUND: Routine clinical culture detects a subset of the cystic fibrosis (CF) airways microbiota based on culture-independent (molecular) methods. This study aimed to determine how extended sputum culture of viable bacteria changes over time in relation to clinical status and predicts exacerbations. METHODS: Sputa from patients at a baseline stable and up to three subsequent time-points were analysed by extended-quantitative culture; aerobe/anaerobe densities, ecological indexes and community structure were assessed together with clinical outcomes. RESULTS: Eighty patients were prospectively recruited. Sputa were successfully collected and cultured at 199/267 (74.5%) study visits. Eighty-two sputa from 25 patients comprised a complete sample-set for longitudinal analyses. Bacterial density, ecological indexes and clinical outcomes were unchanged in 18 patients with three sequential stable visits. Conversely, in 7 patients who had an exacerbation, total bacterial and aerobe densities differed over four study visits (P < .001) with this difference particularly apparent between the baseline visit and completion of acute antibiotic treatment where a decrease in density was observed. Bacterial communities were more similar within than between patients but stable patients had the least variation in community structure over time. Using logistic regression in a further analysis, baseline features in 37 patients without compared to 15 patients with a subsequent exacerbation showed that clinical measures rather than bacterial density or ecological indexes were independent predictors of an exacerbation. CONCLUSIONS: Greater fluctuation in the viable bacterial community during treatment of an exacerbation than between stable visits was observed. Extended-quantitative culture did not provide prognostic information of a future exacerbation.

The Influence of Traffic, Area Location, and Other Factors on Operating Room Microbial Load.

OBJECTIVE To determine how the movement of patients, equipment, materials, staff, and door openings within the operating room (OR) affect microbial loads at various locations within the OR. DESIGN Observation and sampling study. SETTING Academic health center, public hospital. METHODS We first analyzed 27 videotaped procedures to determine the areas in the OR with high and low numbers of people in transit. We then placed air samplers and settle plates in representative locations during 21 procedures in 4 different ORs during 2 different seasons of the year to measure microbial load in colony-forming units (CFU). The temperature and humidity, number of door openings, physical movement, and the number of people in the OR were measured for each procedure. Statistical analysis was conducted using hierarchical regression. RESULTS The microbial load was affected by the time of year that the samples were taken. Both microbial load measured by the air samplers and by settle plates in 1 area of the OR was correlated with the physical movement of people in the same area but not with the number of door openings and the number of people in the OR. CONCLUSIONS Movement in the OR is correlated with the microbial load. Establishing operational guidelines or developing OR layouts that focus on minimizing movement by incorporating desirable internal storage points and workstations can potentially reduce microbial load, thereby potentially reducing surgical site infection risk. Infect Control Hosp Epidemiol 2018;39:391-397.

Microbiological Control for Affinity Capture Chromatography Processing: An Industry Perspective.

The purpose of this paper is to provide a summary of a BPOG-led industry survey of the microbiological control aspects of affinity chromatography processing in the biopharmaceutical industry. The document provides a summary of historical microbiological control concerns, coupled with industry-derived best practices, for material, equipment, and storage controls required to mitigate the potential for microbial ingress and contamination of chromatography resin and equipment. These best practice guidelines, which are derived from the members of the BPOG Bioburden Working Group, are intended to assist biopharmaceutical manufacturers to enhance microbial control and monitoring strategies for chromatography systems.

Assessment of real-time PCR cycle threshold values in Microsporum canis culture-positive and culture-negative cats in an animal shelter: a field study.

Objectives Real-time PCR provides quantitative information, recorded as the cycle threshold (Ct) value, about the number of organisms detected in a diagnostic sample. The Ct value correlates with the number of copies of the target organism in an inversely proportional and exponential relationship. The aim of the study was to determine whether Ct values could be used to distinguish between culture-positive and culture-negative samples. Methods This was a retrospective analysis of Ct values from dermatophyte PCR results in cats with suspicious skin lesions or suspected exposure to dermatophytosis. Results One hundred and thirty-two samples were included. Using culture as the gold standard, 28 were true positives, 12 were false positives and 92 were true negatives. The area under the curve for the pretreatment time point was 96.8% (95% confidence interval [CI] 94.2-99.5) compared with 74.3% (95% CI 52.6-96.0) for pooled data during treatment. Before treatment, a Ct cut-off of <35.7 (approximate DNA count 300) provided a sensitivity of 92.3% and specificity of 95.2%. There was no reliable cut-off Ct value between culture-positive and culture-negative samples during treatment. Ct values prior to treatment differed significantly between the true-positive and false-positive groups ( P = 0.0056). There was a significant difference between the pretreatment and first and second negative culture time points ( P = 0.0002 and P <0.0001, respectively). However, there was substantial overlap between Ct values for true positives and true negatives, and for pre- and intra-treatment time points. Conclusions and relevance Ct values had limited usefulness for distinguishing between culture-positive and culture-negative cases when field study samples were analyzed. In addition, Ct values were less reliable than fungal culture for determining mycological cure.

Cost-Effective Live Cell Density Determination of Liquid Cultured Microorganisms.

Live monitoring of microorganisms growth in liquid medium is a desired parameter for many research fields. A wildly used approach for determining microbial liquid growth quantification is based on light scattering as the result of the physical interaction of light with microbial cells. These measurements are generally achieved using costly table-top instruments; however, a live, reliable, and straight forward instrument constructed using parts that are inexpensive may provide opportunities for many researchers. Here, such an instrument has been constructed and tested. It consists of modular test tube holding chambers, each with a low power monochromatic light-emitting diode, and a monolithic photodiode. A microcontroller connects to all modular chambers to control the diodes, and send the live data to either an LCD screen, or a computer. This work demonstrate that this modular instrument can determine precise cell concentrations for the bacteria Escherichia coli and Pseudomonas syringae pv. tomato DC3000, as well as Saccharomyces cerevisiae yeast.

Feed gas effect on plasma inactivation mechanism of Salmonella Typhimurium in onion and quality assessment of the treated sample.

A submerged dielectric barrier discharge (DBD) plasma reactor was used to inactivate artificially inoculated reference strains of Salmonella Typhimurium ATCC 14028 on sliced onion (3 cm × 3 cm). Salmonella Typhimurium reductions obtained after 10 min of treatment were 3.96 log CFU/slice and 1.64 log CFU/slice for clean dry air and N2 feed gas, respectively. Variations observed in Optical Emission Spectra (OES) for different feed gases are responsible for the inactivation level variations of Salmonella Typhimurium. The physiochemical properties of the onion slices, such as quercetin content, ascorbic acid content and color parameters, were monitored before and after treatment and the changes that occurred were measured to be in the acceptable range. Quercetin content was reduced only 3.74-5.07% for 10 min treatment, higher reduction was obtained for the use of clean dry air than that of N2 feed gas. Ascorbic acid loss was measured to be 11.82% and 7.98% for a 10 min treatment with clean dry air and N2 feed gas, respectively. The color parameters did not show significant changes upon treatment (p > 0.05) of the same duration for the uses of different feed gases.

Liquid based microbiological transport systems: conformity assessment of two commercial devices.

We compared two types of liquid-based microbiology devices for microorganism viability according to standardized quantitative elution method CLSI M40-A2. The eSwab® met CLSI acceptance criteria of viability maintenance for all microorganisms tested. The Σ-Transwab® failed to meet CLSI acceptance criteria for Peptostreptococcus anaerobius, Prevotella melaninogenica, Fusobacterium nucleatum and Haemophilus influenzae.

Highly selective colorimetric bacteria sensing based on protein-capped nanoparticles.

A rapid and cost-effective colorimetric sensor has been developed for the detection of bacteria (Bacillus subtilis was selected as an example). The sensor was designed to rely on lysozyme-capped AuNPs with the advantages of effective amplification and high specificity. In the sensing system, lysozyme was able to bind strongly to Bacillus subtilis, which effectively induced a color change of the solution from light purple to purplish red. The lowest concentration of Bacillus subtilis detectable by the naked eye was 4.5 × 10(3) colony-forming units (CFU) mL(-1). Similar results were discernable from UV-Vis absorption measurements. A good specificity was observed through a statistical analysis method using the SPSS software (version 17.0). This simple colorimetric sensor may therefore be a rapid and specific method for a bacterial detection assay in complex samples.

Bioluminescence ATP monitoring for the routine assessment of food contact surface cleanliness in a university canteen.

ATP bioluminescence monitoring and traditional microbiological analyses (viable counting of total mesophilic aerobes, coliforms and Escherichia coli) were used to evaluate the effectiveness of Sanitation Standard Operating Procedures (SSOP) at a university canteen which uses a HACCP-based approach. To that end, 10 cleaning control points (CPs), including food contact surfaces at risk of contamination from product residues or microbial growth, were analysed during an 8-month monitoring period. Arbitrary acceptability limits were set for both microbial loads and ATP bioluminescence readings. A highly significant correlation (r = 0.99) between the means of ATP bioluminescence readings and the viable counts of total mesophilic aerobes was seen, thus revealing a strong association of these parameters with the level of surface contamination. Among CPs, the raw meat and multi-purpose chopping boards showed the highest criticalities. Although ATP bioluminescence technology cannot substitute traditional microbiological analyses for the determination of microbial load on food contact surfaces, it has proved to be a powerful tool for the real time monitoring of surface cleanliness at mass catering plants, for verify the correct application of SSOP, and hence for their implementation/revision in the case of poor hygiene.

Microbiological assessment of well water at different durations of storage.

Water is the most universally used single necessity of life. To attain a safe water quality to various communities, an understanding of water microbiology and chemistry is therefore imperative. In this study, well water at different storage durations of 0, 2, 4, 6 and 8 weeks were assessed for bacteriological quality using standard microbiological techniques. Black barrel-shaped plastic containers (300 liter capacity) were used for different storage durations. Water samples at the different storage durations were collected from each corresponding containers. Sterile swabs were used to sample the sides and bottom of the storage containers to determine the prevalence of specific bacteria present in the samples. The results obtained showed that 0 week storage had the highest (100.00 CFU mL(-1)) coliform counts while the lowest (28 CFU mL(-1)) was obtained for 8 weeks of storage. Escherichia coli were not found in 4, 6 and 8 weeks old water. 0 and 2 weeks old water contained E. coli and the mean values were 1.80 x 10(4) +/- 0.03 and 1.43 x 10(4) +/- 0.01 CFU mL(-1), respectively (p < 0.05). Salmonella organisms were found in the 0 week old water but absent in the 2, 4, 6 and 8 weeks old water. Shigella count (62.33 x 10(2) +/- 45.30 CFU mL(-1)) was highest in 4 week old water while the lowest (11.0 x 10(3) +/- 1.00 CFU mL(-1)) was found in 6 week old water (p < 0.05). Zero week old water had the lowest significant (p < 0.05) value of 0.35 x 10(4) +/- 0.05 CFU mL(-1) for mesophilic bacteria and the highest value of 50.00 x 10(4) +/- 10.0 CFU mL(-1) was recorded in the 8 weeks old water. Sides and bottom samples were contaminated with coliforms, E. coli, Salmonella and Shigella organisms. It was concluded that the variously stored well water samples were contaminated with bacteria and the values obtained were above the recommended standards by the World Health Organization (WHO).

A comparative assessment of culture and serology in the diagnosis of brucellosis in dairy cattle.

To investigate the usefulness of culture for the confirmation of brucellosis in cattle, a comparison of culture and serology was undertaken on 248 animals in four dairy herds where the disease was active. Paired supramammary (SM), retropharyngeal (RP), and internal iliac (IL) lymph nodes were cultured, and five serological tests were deployed: the microserum agglutination test (MSAT), complement fixation test (CFT), the indirect (iELISA) and competitive ELISA, and the fluorescence polarisation assay (FPA). Brucella abortus was isolated from 86.8% of animals on combined culture of all three lymph nodes. Individually, the highest isolation rate was from the RP (90.5% of culture positives). Of culture positive animals, 13.7% and 6.2% were positive from the RP and SM alone, respectively. Approximately half of the positive cultures yielded <10 colonies/culture plate. Although 80.9% of animals were positive in at least one serological test, only 45.2% were positive in all five. For culture-positive animals, the MSAT was the most sensitive test (71.8%). Of the culture-negative animals 67.7% were positive in at least one test, while 12.9% were positive in all five. Titres were higher in animals culture-positive from the SM, and there was a direct correlation between higher titres and higher colony counts in SM cultures. Only 8.9% of animals were both culture-negative and seropositive (in at least one test), while 16.5% were culture-positive and seronegative in all five tests. The results highlight and validate the sensitivity of bacteriological culture in confirming a diagnosis of bovine brucellosis. While the MSAT and FPA were the most sensitive serological tests, a significant percentage of infected animals were undetectable using these standard serological assays.

Application of microbiological quantitative methods for evaluation of changes in the amount of bacteria in patients with wounds and purulent fistulas subjected to phage therapy and for assessment of phage preparation effectiveness (in vitro studies).

PURPOSE: Quantitative microbiological studies may provide important information required for successful phage therapy (PT), however methods for PT monitoring of purulent wounds and fistulas has never been reported before. Therefore our goal was to determine and apply microbiological quantitative methods (MQMs) for monitoring experimental PT. METHODS: Samples from agar plates with growing bacteria were collected using dry and wet sterile compresses, or swabs. After shaking the sample in saline the amount of bacteria in suspension was determined. The method was standardized. The MQM using compress was applied for comparison of in vitro activity of phage preparations with other agents for wound rinsing. The usefulness of this swabbing method was tested in the Phage Therapy Unit for monitoring of experimental PT of patients with chronic wounds or purulent fistulas. RESULTS: Minimum, maximum and standard deviation values used for standardization of the studied method showed that data repeatability was good; thus the method was used for quantitation of bacteria taken both from plates in vitro and patients samples. Effectiveness of phage preparations was compared to gentamicin in vitro. Phages were as effective as antibiotics in reducing the amount of bacteria on agar plates, and this effect was not only due to simple mechanical removal of bacteria, but dependent on their antibacterial activity. We have also observed that the results of bacteria quantitation may correlate with the local status of a wound/fistula in a particular stage of PT. CONCLUSION: The standardized swabbing method of bacteria quantitation can be used for PT monitoring. Presented MQMs are simple and may help to monitor the therapy process and to decide on its duration, frequency and a kind of the phage applied. They can also be applied in other antibacterial treatment strategies.