Study on the construction of nomogram prediction model for prognostic assessment of heart failure patients based on serological markers and echocardiography.

OBJECTIVE: We aimed to construct a nomogram prediction model for prognostic assessment of patients with heart failure (HF) based on serological markers and echocardiography. PATIENTS AND METHODS: A total of 200 HF patients admitted to the Second Affiliated Hospital of Nanchang University from January 2018 to January 2020 were selected as the research objects. According to the New York Heart Association (NYHA) cardiac function classification, they were divided into 3 groups, including 65 cases of grade II, 97 cases of grade III, and 38 cases of grade IV. Three groups of echocardiographic parameters were compared [including left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), left ventricular end-systolic volume (LVESV)], differences in serum markers brain natriuretic peptide (BNP), soluble growth-stimulating expression gene 2 (sST2) and the Modified Early Warning Score (MEWS). The patients were divided into two groups according to their clinical outcomes during the follow-up period, including 52 cases in the death group and 148 cases in the survival group. The clinical data of the two groups were compared, and multi-factor logistic regression analysis was performed to screen out the independent risk factors affecting the patient's death. A nomogram model of the patient's mortality risk was constructed based on the independent risk factors. Receiver operating characteristic (ROC) curves and calibration curves were used to evaluate the discrimination and accuracy of the nomogram model. RESULTS: As the cardiac function class of elderly chronic heart failure (CHF) patients increases, LVEDD, LVESD, sST2, and MEWS increase and LVEF decreases (p<0.05). Multifactor analysis results showed that LVEF, LVEDD, sST2, and MEWS were independent factors affecting the clinical outcome of patients. The AUCs predicted using LVEF, LVEDD, sST2, and MEWS alone were 0.738, 0.775, 0.717, 0.831, and 0.768, respectively. There is a certain degree of discrimination, and the model has extremely high accuracy. CONCLUSIONS: MEWS, LVEDD, and sST2 increase as the NYHA cardiac function grade of HF patients increases and LVEF decreases, which can reflect the severity of the disease to a certain extent. Additionally, the nomogram model established based on this has a high predictive value for the long-term prognosis of patients and can formulate effective intervention measures for quantitative values.

[68Ga-PSMA-I&T PET/CT for assessment of tumor burden in primary lesions of treatmentnaïve prostate cancer].

OBJECTIVE: To investigate the value of 68Ga-labeled prostate specific membrane antigen (PSMA) PET/CT for assessing tumor load in primary lesions for risk stratification and predicting metastasis of newly diagnosed prostate cancer (PCa). METHODS: We retrospectively analyzed the data of 36 patients (mean age 71.3 ± 8.6 years, range 56 to 89 years) with newly diagnosed PCa undergoing 68Ga-PSMA-I&T PET/CT from June 2018 to July 2019. SUVmax and SUVmean of the primary lesions were measured, and the primary PSMA tumor volume (PSMA-TV) and total lesion PSMA (TL-PSMA) were automatically measured and calculated in all the patients. The correlations of primary SUVmax, PSMA-TV, and TL-PSMA with PSA and Gleason score (GS) were analyzed, and SUVmax, PSMA-TV and TL-PSMA of the primary lesions were compared among different PCa subgroups. RESULTS: SUVmax, PSMA-TV and TL-PSMA of the primary lesions were all correlated with PSA and GS (P < 0.05). PCa subgroup analysis showed that SUVmax, PSMA-TV and TL-PSMA were all significantly higher in patients with PSA >20 ng/mL than in those with PSA ≤20 ng/mL (P < 0.001), and were higher in patients with a GS ≥8 than in those with a GS ≤7 (P < 0.001). PSMA-TV and TL-PSMA were significantly higher in patients with tumor metastasis than in those without metastasis (P < 0.001), while SUVmax did not differ significantly with tumor metastasis. SUVmax (P=0.002), PSMA-TV (P < 0.001), and TL-PSMA (P < 0.001) were all significantly higher in high-risk group than in low-to moderate-risk group. CONCLUSION: PSMA-TV and TL-PSMA of 68Ga-PSMA-I&T PET/CT have potential value in predicting risk stratification and metastasis of newly diagnosed PCa.

Comparative assessment of amino acids and volatile compounds role in the formation of wines sensor properties by means of covariation analysis.

The objects of study were 150 samples of natural dry red and white grape wines of Russian origin, obtained by traditional technologies from European and hybrid grape varieties grown in wineries in Krasnodar Krai in 2010-2016. Natural red (Cabernet, Merlot) and white (Aligote, Riesling, Pinot Noir) (alcohol content of 9-13 % by volume, acidity of 4-7 g/dm3), as well as blend wines based on Cabernet Sauvignon, Merlot and Pinot Noir wines made under experimental conditions were analyzed. Chromatographic and electrophoretic methods were used to determine the content of volatile components and amino acids in the studied samples. A sensory assessment of wine quality was carried out by wine specialists working in the wine industry and having professional experience in the field of sensory analysis. Using statistical modeling we carried out a comparative assessment of the role of amino acids - threonine, proline, arginine and volatile compounds - methanol, acetic acid, furfural in the perception of taste and aromatic properties of wines, a general indicator of which is the average tasting rating. High adequacy of the regression model constructed using covariance analysis indicates that mainly amino acids and volatile compounds determine the sensory properties of wines. The dominant role of amino acids in the perception of taste and aromatic characteristics compared to other wine components is mathematically justified in accordance with the criterion of one-dimensional significance. It has been shown that more than 82% of the sensory characteristics of the analyzed wines group fall on the amino acids and volatile compounds under consideration, and less than 18% - on all the others, including titrated acids, free amino acids, mineral components, phenols, etc.

[Epidemiology and Management of Heart Failure Patients With Atrial Fibrillation].

The number of patients with heart failure and atrial fibrillation is huge. Population of patients with heart failure in combination with atrial fibrillation is characterized by poor quality of life and adverse outcomes. In this review we summarized data on the guideline adherence and prevalence of long-term anticoagulant therapy in patients with atrial fibrillation and heart failure.

Assessment of cognitive function in adult patients with hemorrhagic moyamoya disease who received no surgical revascularization.

BACKGROUND AND PURPOSE: Due to controversial surgical treatment for hemorrhagic moyamoya disease (MMD), a large proportion of these patients chose conservative treatment. The aim of this study was to assess cognitive function in adult patients with hemorrhagic MMD who received no surgical revascularization. METHODS: Twenty-six adult hemorrhagic MMD patients with only intraventricular hemorrhage (IVH) confirmed by positive computed tomography and magnetic resonance imaging scan, 20 patients with spontaneous IVH whose digital subtraction angiography results were negative, and 30 healthy controls were identified and matched for age, gender, education background and living area. Cognitive function was evaluated by Montreal Cognitive Assessment (MoCA). The non-parametric test was used for comparisons among the three groups. RESULTS: No patient was confirmed cognitive dysfunction at the initial screening. Twenty-four (92%) cases presented mild cognitive impairment (MCI) after 1 year. All the cases demonstrated MCI after 2 years. The difference between cases and healthy controls was statistically significant at the second screening (P = 0.000) and the third screening (P = 0.000), as was that between cases and patients with spontaneous IVH at the second screening (P = 0.000) and the third screening (P = 0.000). In addition, there were significant decreases in all MoCA subscores (P = 0.000) with special regards to delayed recall, visual space and executive function in cases compared with the other two groups. Moreover, significant differences were found in the subgroups of smoking (P = 0.021) and Suzuki angiographic classification of MMD (P = 0.030). CONCLUSIONS: Cognitive impairment is a long-term complication for adult hemorrhagic MMD patients who underwent conservative treatment.

Dreaming during sevoflurane or propofol short-term sedation: a randomised controlled trial.

Prior reports suggest that dreaming during anaesthesia is dependent on recovery time. Dreaming during sedation may impact patient satisfaction. The current study explores the incidence and content of dreaming during short-term sedation with sevoflurane or propofol and investigates whether dreaming is affected by recovery time. A total of 200 women undergoing first trimester abortion (American Society of Anesthesiologists physical status I) participated in the study. Patients were randomly assigned to receive either sevoflurane or propofol for short-term sedation. Patients were interviewed upon emergence with the modified Brice questionnaire. The results showed the incidence of dreaming was significantly different between anaesthesia groups with 60% (60/100) of the sevoflurane group and 33% (33/100) of the propofol group (P=0.000). However, recovery time did not significantly differ between groups. In the sevoflurane group, a greater number of dreamers could not recall what they had dreamed about (P=0.02) and more patients reported dreams that had no sound (P=0.03) or movement (P=0.001) compared with dreamers in the propofol group. Most participants reported dreams with positive emotional content and this did not significantly differ between groups. Anaesthesia administered had no effect on patient satisfaction. The results suggest that the incidence of dreaming was not affected by recovery time. Patient satisfaction was not influenced by choice of sedative and/or by the occurrence of dreaming during sevoflurane or propofol short-term sedation.

Strong association of socioeconomic status with genetic ancestry in Latinos: implications for admixture studies of type 2 diabetes.

AIMS/HYPOTHESIS: Type 2 diabetes is more prevalent in US American minority populations of African or Native American descent than it is in European Americans. However, the proportion of this epidemiological difference that can be ascribed to genetic or environmental factors is unknown. To determine whether genetic ancestry is correlated with diabetes risk in Latinos, we estimated the proportion of European ancestry in case-control samples from Mexico and Colombia in whom socioeconomic status had been carefully ascertained. METHODS: We genotyped 67 ancestry-informative markers in 499 participants with type 2 diabetes and 197 controls from Medellín (Colombia), as well as in 163 participants with type 2 diabetes and 72 controls from central Mexico. Each participant was assigned a socioeconomic status scale via various measures. RESULTS: Although European ancestry was associated with lower diabetes risk in Mexicans (OR [95% CI] 0.06 [0.02-0.21], p = 2.0 x 10(-5)) and Colombians (OR 0.26 [0.08-0.78], p = 0.02), adjustment for socioeconomic status eliminated the association in the Colombian sample (OR 0.64 [0.19-2.12], p = 0.46) and significantly attenuated it in the Mexican sample (OR 0.17 [0.04-0.71], p = 0.02). Adjustment for BMI did not change the results. CONCLUSIONS/INTERPRETATION: The proportion of non-European ancestry is associated with both type 2 diabetes and lower socioeconomic status in admixed Latino populations from North and South America. We conclude that ancestry-directed search for genetic markers associated with type 2 diabetes in Latinos may benefit from information involving social factors, as these factors have a quantitatively important effect on type 2 diabetes risk relative to ancestry effects.

Understanding Taiwanese children's perceptions of peace and strategies to make peace: a social and cultural perspective.

This exploratory study described Taiwanese children's perceptions of peace and what they think children can do to make peace. In-depth interviews were conducted with 60 Taiwanese children ages 4 to 18 years. The most predominant themes for the perceptions of peace were what peace is not, prosocial behaviors, positive emotions, and positive evaluations of peace. Approximately half of the children (48%) provided specific strategies for making peace. The suggested strategies generally were based on the child's immediate environment, such as "don't fight" "don't argue," and specific prosocial behaviors. 52% of children either said, "I don't know" when asked what children can do to make peace, or did not feel empowered to make peace. The initial findings were interpreted in terms of sociocultural issues, such as cultural heritage and upbringing, as well as within a political context.

The cost of screening adolescents for overweight and hypertension using a community partnership model.

OBJECTIVES: (1) Determine the prevalence of overweight and high blood pressure (BP) among middle and high school students over a 2-year period and, (2) measure the cost and initial outcomes of screening. DESIGN: Cost and outcome description using a cross-sectional design sample. The target population was 12- to 19-year-old healthy students attending grades 7 through 12 at 3 proximal schools located in a large urban school district in Texas. RESULTS: Of 2,338 students screened, 925 (39.6%) had a body mass index (BMI)>or=85th percentile and 504 (21.6%) had BMIs>or=95th percentile for age and gender. There were 346 students (14.8%) with BMIs>or=85th percentile and systolic blood pressure (SBP)>or=95th percentile for age, gender, and height. The cost of the 2-year screening program was $66,442, and the cost per student was $28. The cost to identify a student with increased BMI or high SBP was $72 and $107, respectively. CONCLUSIONS: This study offered an objective framework to examine the cost and outcomes of screening children for overweight and increased BP. The study has implications for discussion and informed decision making about school-based screening for these conditions.

Assessment of DNA damage in multiple organs of mice after whole body X-irradiation using the comet assay.

The comet assay was performed to elucidate the linearity of calibration curves and detection limits for DNA damage in multiple organs of whole body X-irradiated mice, and rates of reduction in DNA damage by DNA repair during the irradiation period were estimated in the respective organs by comparing the rates of increase in DNA damage at different absorbed dose rates of X-rays. Of the assay parameters, tail length and the percentage DNA in the tail showed a higher sensitivity to DNA damage in most organs than Olive tail moment. Data at the higher absorbed dose rates (2.22 or 1.44 Gy/min) showed good correlations between absorbed doses and these two parameters, with correlation coefficients of more than 0.7 in many organs. However, this assay had difficulty detecting DNA damage at the lower absorption dose rate (0.72 Gy/min). The estimated rates of increase in DNA damage and those of DNA repair during the irradiation period in the respective organs suggested differences in the radiosensitivity of nuclear DNA and DNA repair capacity among organs. Our results indicated that absorbed dose rates of 1.0-1.3 Gy/min or greater were needed to induce detectable DNA damages by the comet assay in many organs.

Surgical undertreatment of glaucoma in black beneficiaries of medicare.

OBJECTIVE: To identify whether there was surgical undertreatment of glaucoma in black beneficiaries of Medicare from 1991 to 1994. METHODS: We performed a retrospective cohort analysis on all argon laser trabeculoplasty or trabeculectomy surgery claims to the Health Care Financing Administration between 1991 and 1994. There were 191 287 Medicare patients who were black or white, at least 65 years of age, and resided in the United States at the time of their glaucoma surgery. Age- and sex-adjusted rates were obtained and compared with surgery rates expected based on disease prevalence. RESULTS: The age-sex-adjusted rate ratio of glaucoma surgical procedures for blacks to whites was 2.14. Assuming that treatments should be done in proportion to age-race prevalence, blacks undergo glaucoma surgery at approximately 47% below the expected rate. CONCLUSIONS: Blacks underwent argon laser trabeculoplasties and trabeculectomies at half the rate of whites from 1991 to 1994. Although in 1993 and 1994 there was a slight trend toward higher surgery rates in blacks, the magnitude of this improvement was small compared with estimated differences in the surgery rates between blacks and whites.

Prospective study of the value of serum chromogranin A or serum gastrin levels in the assessment of the presence, extent, or growth of gastrinomas.

BACKGROUND: Serum chromogranin A levels (CgA) are reported by some authors to be of clinical utility for assessing the presence or absence of a pancreatic endocrine tumor and tumor extent or growth. The aim of the current study was to assess this finding and compare the results with those from serum gastrin determinations (FSG) in a large cohort of patients with gastrinomas. METHODS: In 112 consecutive patients with the Zollinger-Ellison syndrome serum CgA and FSG levels were measured and correlated with disease activity, extent of disease, and the presence of multiple endocrine neoplasia type-1 (MEN-1) or gastric carcinoid tumors. RESULTS: Serum CgA levels drawn on 2 consecutive days correlated closely (P < 0.00001) as did serum gastrin levels. Serum CgA levels correlated significantly with FSG levels (P < 0.00001). Serum CgA and FSG levels were significantly higher in patients with active disease than in disease free patients (P < 0.00001). The sensitivity for the presence of disease was higher for CgA compared with FSG (92% vs. 80%; P = 0.021). However, the specificity of CgA was 67%. Serum CgA levels were not significantly different in the four disease categories (stable extrahepatic disease, increasing extrahepatic disease, stable liver metastases, and increasing liver metastases). FSG levels were significantly lower in patients with stable extrahepatic disease compared with those with increasing extrahepatic disease. However, both tumor markers decreased significantly with a gastrinoma resection in five patients. The presence of MEN-1 or a gastric carcinoid tumor did not influence the results. CONCLUSIONS: The results of the current study showed that serum CgA and FSG levels both are sensitive tumor markers for the detection of a gastrinoma; however, CgA levels have a relatively low specificity. Neither the magnitude of the serum CgA nor gastrin level correlated with tumor growth or tumor extent and therefore cannot be used to determine these variables. However, in contrast to some other studies, the results of the current study show that changes in serum CgA or gastrin in a given patient with time are related to the tumor extent and not to gastric mucosal changes due to hypergastrinemia.

Task analysis for industrial work process from aspects of human reliability and system safety.

In the design, development, and manufacturing stage of industrial products, engineers usually focus on the problems caused by hardware or software, but pay less attention to problems caused by "human error," which may significantly affect system reliability and safety. Although operating procedures are strictly followed, human error still may occur occasionally. Among the influencing factors, the inappropriate design of standard operation procedure (SOP) or standard assembly procedure (SAP) is an important and latent reason for unexpected results found during human operation. To reduce the error probability and error effects of these unexpected behaviors in the industrial work process, overall evaluation of SOP or SAP quality has become an essential task. The human error criticality analysis (HECA) method was developed to identify the potentially critical problems caused by human error in the human operation system. This method performs task analysis on the basis of operation procedure. For example, SOP, analyzes the human error probability (HEP) for each human operation step, and assesses its error effects to the whole system. The results of the analysis will show the interrelationship that exists between critical human tasks, critical human error modes, and human reliability information of the human operation system. To identify the robustness of the model, a case study of initiator assembly tasks was conducted. Results show that the HECA method is practicable in evaluating the operation procedure, and the information is valuable in identifying the means to upgrade human reliability and system safety for human tasks.

Factors associated with elevated rates of adverse outcomes after cyclodestructive procedures versus drainage device procedures.

OBJECTIVE: To identify factors associated with an increased risk of adverse outcomes after cyclodestructive or drainage device procedures. DESIGN: Retrospective, cohort analysis. PARTICIPANTS: A total of 5570 Medicare patients who were older than 65 years of age and who underwent cyclodestructive or drainage device procedures in 1994 participated. INTERVENTION: The authors identified cyclodestructive and drainage device procedures from claims to the Health Care Finance Administration (HCFA) by International Classification of Diseases (ICD-9) procedure codes, Current Procedural Terminology procedure codes, and HCFA Common Procedural Classification System codes. The authors analyzed adverse outcome rates using hierarchical logistic regression. Race, age group, gender, length of observed follow-up, state in which surgery took place, ocular procedures performed before and at the same time as the index surgery, and ocular diagnosis were included as covariates in the model. MAIN OUTCOME MEASURES: The authors defined an adverse outcome as the occurrence after the index surgery of at least one of the following: repeat cyclodestructive or drainage device procedure, retinal hole-tear repair, retinal detachment repair, surgery for endophthalmitis, vitrectomy, enucleation, evisceration, surgery for ocular hypotony, and/or extrusion or revision of drainage device. Adverse outcomes were also defined without the inclusion of repeat cyclodestructive or drainage device procedures. RESULTS: When repeat cyclodestructive or drainage device procedures were not included in the definition of an adverse outcome, eyes with a drainage device procedure were 3.8 times more likely to have an adverse outcome than eyes with a cyclodestructive procedure (odds ratio [OR], 3.8; 95% confidence interval [CI], 3.07, 4.67). Subjects with concurrent corneal transplant had increased odds of an adverse outcome compared to subjects without a concurrent corneal transplant (OR, 2.00; 95% CI, 1.27, 3.15). When the definition of an adverse outcome included repeat cyclodestructive or drainage device procedures, the odds of an adverse outcome were similar for both cyclodestructive and drainage device procedures (OR, 0.94; 95% CI, 0.79, 1.13). CONCLUSIONS: Cyclodestructive procedures need to be repeated more frequently than drainage device procedures. However, if the patient has a drainage device procedure, then that patient is more likely to have other types of adverse ophthalmic events than if he or she had a cyclodestructive procedure. Because the average follow-up of subjects in this study is 5 months (range, 0-12 months), outcomes that might take longer to manifest themselves would be excluded from this study.

Factors associated with elevated complication rates after partial-thickness or full-thickness glaucoma surgical procedures in the United States during 1994.

OBJECTIVE: The purpose of the study was to identify factors associated with an increased risk of complications after partial-thickness or full-thickness glaucoma surgery. DESIGN: A retrospective, cohort analysis. PARTICIPANTS: A total of 24,206 Medicare patients who were older than 65 years of age and who were enrolled in Medicare in 1994 underwent partial-thickness or full-thickness glaucoma surgical procedures in 1994. INTERVENTION: The authors obtained data on all glaucoma surgery claims to the Health Care Finance Administration in 1994 and analyzed complication rates using hierarchical logistic regression, separately smoothing four sets of regression coefficients (state-level effects, systemic and ocular diagnoses, prior ocular surgeries, and concomitant ocular surgeries). MAIN OUTCOME MEASURE: Patients were classified as having complications if their records showed at least one of the following occurrences after surgery: retinal detachment repair, endophthalmitis, scleral fistula revision-repair, or cyclodestruction. RESULTS: The risk of complications was greater for full-thickness procedures than for partial-thickness procedures (odds ratio [OR] = 1.51; 95% confidence interval [CI] = 1.07, 2.12). Compared to glaucoma surgeries performed without an additional intraocular procedure, glaucoma surgery with prior phacoemulsification (OR = 0.51; 95% CI = 0.35, 0.74) was associated with lower complication rates, as was glaucoma surgery with prior argon laser trabeculoplasty (OR = 0.62; 95% CI = 0.44, 0.88). A concomitant vitrectomy (OR = 1.86, 95% CI = 1.35, 2.56) was associated with greater odds of a complication. The mean follow-up of subjects was 184 days (standard deviation, +/- 107), whereas the mean time to a complication was 49 days (standard deviation, +/- 63). CONCLUSION: The risk of an early postoperative complication after full-thickness procedures appears to be greater than that after partial-thickness procedures. Concomitant intraocular procedures performed in conjunction with glaucoma surgery, such as a vitrectomy, can substantially increase the risk of retinal detachment repair, endophthalmitis, scleral fistula revision-repair, and/or cyclodestruction.

Annual predictions of adverse outcomes after glaucoma surgery in the United States.

PURPOSE: To predict the number of adverse outcomes or additional ocular surgeries after glaucoma surgery in each year from 1990 to 1994 with ordinary and hierarchical logistic regression models developed with 1989 Medicare data. METHODS: We obtained data on all intraocular and laser glaucoma surgery claims (for example, laser trabeculoplasty, full-thickness and partial-thickness procedures, and cycloablation) to the Health Care Finance Administration (HCFA) in 1989 and developed an ordinary (non-hierarchical) logistic regression model and two hierarchical logistic regression models. The two hierarchical models smoothed state-level effects to different degrees in an effort to improve the precision of model predictions. RESULTS: The hierarchical logistic regression models predicted the number of adverse outcomes or additional ocular surgeries, including repeat glaucoma surgery, from 1990 to 1994 significantly better than the ordinary model. None of the models predicted the downward trend in adverse outcomes in 1990 and 1992, although all three models were able to predict the increase in adverse outcomes in 1991 and the downward trend in adverse outcomes in 1993 and 1994. CONCLUSION: Although systematic changes over time in physician practice or billing patterns affected the ability of both ordinary and hierarchical regression models to predict the number of adverse outcomes in 1990 and 1992, hierarchical logistic regression provides a useful framework for analyzing adverse event rates when the model contains many covariates with imprecisely estimated coefficients. The greater accuracy of predicted adverse event rates from ophthalmic surgeries obtained with hierarchical logistic regression will be useful for future planning and budgeting purposes.

Physiological assessment of bacteria using fluorochromes.

NASA: This minireview focuses on the application of fluorogenic compounds in the detection of bacteria with particular emphasis on the assessment of physiological activity using epifluorescence microscopy. Microbiological applications of several related methods will also be reviewed.^ieng

Rapid in situ assessment of physiological activities in bacterial biofilms using fluorescent probes.

Two rapid in situ enumeration methods using fluorescent probes were used to assess the physiological activities of Klebsiella pneumoniae biofilms on stainless steel. Fluorescent dyes, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and rhodamine 123 (Rh 123), were chosen to perform this study. CTC is a soluble redox indicator which can be reduced by respiring bacteria to fluorescent CTC-formazan crystals. Rh 123 is incorporated into bacteria with respect to cellular proton motive force. The intracellular accumulation of these fluorescent dyes can be determined using epifluorescence microscopy. The results obtained with these two fluorescent probes in situ were compared to the plate count (PC) and in situ direct viable count (DVC) methods. Viable cell densities within biofilms determined by the three in situ methods were comparable and always showed approximately 2-fold higher values than those obtained with the PC method. As an additional advantage, the results were observed after 2 h, which was shorter than the 4 h incubation time required for the DVC method and 24 h for colony formation. The results indicate that staining with CTC and Rh 123 provides rapid information regarding cell numbers and physiological activities of bacteria within biofilms.

A direct viable count method for the enumeration of attached bacteria and assessment of biofilm disinfection.

This report describes the adaptation of an in situ direct viable count (in situ DVC) method in biofilm disinfection studies. The results obtained with this technique were compared to two other enumeration methods, the plate count (PC) and conventional direct viable count (c-DVC). An environmental isolate (Klebsiella pneumoniae Kp1) was used to form biofilms on stainless steel coupons in a stirred batch reactor. The in situ DVC method was applied to directly assess the viability of bacteria in biofilms without disturbing the integrity of the interfacial community. As additional advantages, the results were observed after 4 h instead of the 24 h incubation time required for colony formation and total cell numbers that remained on the substratum were enumerated. Chlorine and monochloramine were used to determine the susceptibilities of attached and planktonic bacteria to disinfection treatment using this novel analytical approach. The planktonic cells in the reactor showed no significant change in susceptibility to disinfectants during the period of biofilm formation. In addition, the attached cells did not reveal any more resistance to disinfection than planktonic cells. The disinfection studies of young biofilms indicated that 0.25 mg/l free chlorine (at pH 7.2) and 1 mg/l monochloramine (at pH 9.0) have comparable disinfection efficiencies at 25 degrees C. Although being a weaker disinfectant, monochloramine was more effective in removing attached bacteria from the substratum than free chlorine. The in situ DVC method always showed at least one log higher viable cell densities than the PC method, suggesting that the in situ DVC method is more efficient in the enumeration of biofilm bacteria. The results also indicated that the in situ DVC method can provide more accurate information regarding the cell numbers and viability of bacteria within biofilms following disinfection.