Development of machine learning algorithms for scaling-up antibiotic stewardship.

BACKGROUND: Antibiotic stewardship programs (ASP) aim to reduce inappropriate use of antibiotics, but their labor-intensive nature impedes their wide adoption. The present study introduces explainable machine learning (ML) models designed to prioritize inpatients who would benefit most from stewardship interventions. METHODS: A cohort of inpatients who received systemic antibiotics and were monitored by a multidisciplinary ASP team at a tertiary hospital in the Republic of Korea was assembled. Data encompassing over 130,000 patient-days and comprising more than 160 features from multiple domains, including prescription records, laboratory, microbiology results, and patient conditions was collected.Outcome labels were generated using medication administration history: discontinuation, switching from intravenous to oral medication (IV to PO), and early or late de-escalation. The models were trained using Extreme Gradient Boosting (XGB) and light Gradient Boosting Machine (LGBM), with SHapley Additive exPlanations (SHAP) analysis used to explain the model's predictions. RESULTS: The models demonstrated strong discrimination when evaluated on a hold-out test set(AUROC - IV to PO: 0.81, Early de-escalation: 0.78, Late de-escalation: 0.72, Discontinue: 0.80). The models identified 41%, 16%, 22%, and 17% more cases requiring discontinuation, IV to PO, early and late de-escalation, respectively, compared to the conventional length of therapy strategy, given that the same number of patients were reviewed by the ASP team. The SHAP results explain how each model makes their predictions, highlighting a unique set of important features that are well-aligned with the clinical intuitions of the ASP team. CONCLUSIONS: The models are expected to improve the efficiency of ASP activities by prioritizing cases that would benefit from different types of ASP interventions along with detailed explanations.

Snoring-related polygenic risk and its relationship with lifestyle factors in a Korean population: KoGES study.

Whereas lifestyle-related factors are recognized as snoring risk factors, the role of genetics in snoring remains uncertain. One way to measure the impact of genetic risk is through the use of a polygenic risk score (PRS). In this study, we aimed to investigate whether genetics plays a role in snoring after adjusting for lifestyle factors. Since the effect of polygenic risks may differ across ethnic groups, we calculated the PRS for snoring from the UK Biobank and applied it to a Korean cohort. We sought to evaluate the reproducibility of the UK Biobank PRS for snoring in the Korean cohort and to investigate the interaction of lifestyle factors and genetic risk on snoring in the Korean population. In this study, we utilized a Korean cohort obtained from the Korean Genome Epidemiology Study (KoGES). We computed the snoring PRS for the Korean cohort based on the UK Biobank PRS. We investigated the relationship between polygenic risks and snoring while controlling for lifestyle factors, including sex, age, body mass index (BMI), alcohol consumption, smoking, physical activity, and sleep time. Additionally, we analyzed the interaction of each lifestyle factor and the genetic odds of snoring. We included 3526 snorers and 1939 nonsnorers from the KoGES cohort and found that the PRS, a polygenic risk factor, was an independent factor for snoring after adjusting for lifestyle factors. In addition, among lifestyle factors, higher BMI, male sex, and older age were the strongest lifestyle factors for snoring. In addition, the highest adjusted odds ratio for snoring was higher BMI (OR 1.98, 95% CI 1.76-2.23), followed by male sex (OR 1.54, 95% CI 1.28-1.86), older age (OR 1.23, 95% CI 1.03-1.35), polygenic risks such as higher PRS (OR 1.18, 95% CI 1.08-1.29), drinking behavior (OR 1.18, 95% CI 1.03-1.35), late sleep mid-time (OR 1.17, 95% CI 1.02-1.33), smoking behavior (OR 0.99, 95% CI 0.82-1.19), and lower physical activity (OR 0.92, 95% CI 0.85-1.00). Our study identified that the UK Biobank PRS for snoring was reproducible in the Korean cohort and that genetic risk served as an independent risk factor for snoring in the Korean population. These findings may help to develop personalized approaches to reduce snoring in individuals with high genetic risk.

Evaluation of Vancomycin TDM Strategies: Prediction and Prevention of Kidney Injuries Based on Vancomycin TDM Results.

The current guidelines for therapeutic drug monitoring (TDM) of vancomycin suggest a target 24-hour area under the curve (AUC0-24) of 400 to 600 mg*h/L for serious methicillin-resistant Staphylococcus aureus infections. In this study, the predictabilities of acute kidney injury (AKI) of various TDM target parameters, target levels, and sampling methods were evaluated in patients who underwent TDM from January 2020 to December 2020. The AUC0-24 and trough values were calculated by both one- and two-point sampling methods, and were evaluated for the predictability of AKI. Among the AUC0-24 cutoff comparisons, the threshold value of 500 mg*h/L in the two sampling methods was statistically significant (P = 0.042) when evaluated for the predictability of AKI. Analysis by an receiver operating characteristic curve estimated an AUC0-24 cutoff value of 563.45 mg*h/L as a predictor of AKI, and was proposed as the upper limit of TDM target.

Current Status of Outpatient Parenteral Antimicrobial Therapy in Korea: Experience of a Single University-Affiliated Acute-Care Hospital.

BACKGROUND: Systematic protocols for the management of outpatient parenteral antimicrobial therapy (OPAT) and information on the current status of a prescription of parenteral antibiotics for outpatients and referred patients are lacking in the Korea. This study aimed to describe the current status of OPAT at a tertiary care hospital in Korea. MATERIALS AND METHODS: This was a retrospective study of outpatients and referral patients who were prescribed parenteral antibiotics from July to December 2019. We reviewed the prescribed antimicrobials, indications for antimicrobial therapy, institution administering the antimicrobial injections, and pre- and post-prescription management. RESULTS: Of the 577 prescriptions assessed in this study, 399 (69.2%) and 178 (30.8%) were delivered using the referral and outpatient models, respectively. About 70% of OPATs were prescribed in the pulmonology, infectious diseases, orthopedics, gastroenterology, and hematology departments. Five antibiotics (ertapenem [26.0%], ceftriaxone [12.8%], kanamycin [11.8%], amikacin [10.1%], and cefazolin [8.5%]) accounted for 69.2% of the total OPATs. Urinary tract (27.3%), respiratory (20.8%), and intra-abdominal (15.9%) infections were the most frequent indications for OPAT. After prescription, there were 295 (73.9%) and 150 (84.3%) follow-up visits in the referral and outpatient models, respectively (P <0.05). Laboratory tests necessary for monitoring were fully performed for 274 (47.5%) prescriptions. CONCLUSION: We found that a significant number of OPATs were prescribed, follow-up visits were not performed in the case of about a quarter of prescriptions, and laboratory monitoring was not fully conducted in more than half of the cases. Therefore, it is necessary to establish an appropriate management program for OPAT. Considering the limited resources and the distribution of OPAT prescriptions, an effective strategy may be to select the frequently-used antibiotics or frequently-prescribing departments and start the program with them.

Stepwise Expansion of Antimicrobial Stewardship Programs and Its Impact on Antibiotic Use and Resistance Rates at a Tertiary Care Hospital in Korea.

To optimize antibiotic use, the US CDC has outlined core elements of antimicrobial stewardship programs (ASP). However, they are difficult to implement in limited-resource settings. We report on the successful implementation of a series of ASP with insufficient number of infectious diseases specialists. We retrospectively collected data regarding antibiotic administration and culture results of all patients admitted to a tertiary care teaching hospital, Seoul National University Bundang Hospital (SNUBH), from January 2010 to December 2019. Trends of antibiotic use and antibiotic resistance rates were compared with those from Korean national data. Trend analyses were performed using nonparametric, two-sided, correlated seasonal Mann-Kendall tests. Total antibiotic agent usage has significantly decreased with ASP implementation at SNUBH since 2010. National claim data from tertiary care hospitals have revealed an increase in the use of all broad-spectrum antibiotics except for third-generation cephalosporins (3GC). In contrast, at SNUBH, glycopeptide and fluoroquinolone use gradually decreased, and 3GC and carbapenem use did not significantly change. Furthermore, the rate of colonization with methicillin-resistant Staphylococcus aureus showed a consistently decreasing trend, while that with 3GC- and fluoroquinolone-resistant Escherichia coli significantly increased. Unlike the national rate, the rate of colonization with antibiotic resistant-Klebsiella pneumoniae did not increase and that of 3GC- and fluoroquinolone-resistant Pseudomonas aeruginosa significantly decreased. Stepwise implementation of core ASP elements was effective in reducing antibiotic use despite a lack of sufficient manpower. Long-term multidisciplinary teamwork is necessary for successful and sustainable ASP implementation. IMPORTANCE Antimicrobial stewardship programs aimed to optimize antibiotic use are difficult to implement in limited-resource settings. Our study indicates that stepwise implementation of core antimicrobial stewardship program elements was effective in reducing antibiotic use in a tertiary care hospital despite the lack of sufficient manpower.

Patient-Level Fall Risk Prediction Using the Observational Medical Outcomes Partnership's Common Data Model: Pilot Feasibility Study.

BACKGROUND: Falls in acute care settings threaten patients' safety. Researchers have been developing fall risk prediction models and exploring risk factors to provide evidence-based fall prevention practices; however, such efforts are hindered by insufficient samples, limited covariates, and a lack of standardized methodologies that aid study replication. OBJECTIVE: The objectives of this study were to (1) convert fall-related electronic health record data into the standardized Observational Medical Outcome Partnership's (OMOP) common data model format and (2) develop models that predict fall risk during 2 time periods. METHODS: As a pilot feasibility test, we converted fall-related electronic health record data (nursing notes, fall risk assessment sheet, patient acuity assessment sheet, and clinical observation sheet) into standardized OMOP common data model format using an extraction, transformation, and load process. We developed fall risk prediction models for 2 time periods (within 7 days of admission and during the entire hospital stay) using 2 algorithms (least absolute shrinkage and selection operator logistic regression and random forest). RESULTS: In total, 6277 nursing statements, 747,049,486 clinical observation sheet records, 1,554,775 fall risk scores, and 5,685,011 patient acuity scores were converted into OMOP common data model format. All our models (area under the receiver operating characteristic curve 0.692-0.726) performed better than the Hendrich II Fall Risk Model. Patient acuity score, fall history, age ≥60 years, movement disorder, and central nervous system agents were the most important predictors in the logistic regression models. CONCLUSIONS: To enhance model performance further, we are currently converting all nursing records into the OMOP common data model data format, which will then be included in the models. Thus, in the near future, the performance of fall risk prediction models could be improved through the application of abundant nursing records and external validation.

Guidelines on Implementing Antimicrobial Stewardship Programs in Korea.

These guidelines were developed as a part of the 2021 Academic R&D Service Project of the Korea Disease Control and Prevention Agency in response to requests from healthcare professionals in clinical practice for guidance on developing antimicrobial stewardship programs (ASPs). These guidelines were developed by means of a systematic literature review and a summary of recent literature, in which evidence-based intervention methods were used to address key questions about the appropriate use of antimicrobial agents and ASP expansion. These guidelines also provide evidence of the effectiveness of ASPs and describe intervention methods applicable in Korea.

Impact of a computerised clinical decision support system on vancomycin loading and the risk of nephrotoxicity.

BACKGROUND: A vancomycin loading dose is recommended for the treatment of serious methicillin-resistant Staphylococcus aureus (MRSA) infections. However, clinicians often do not adhere to these recommendations, mainly due to nephrotoxicity risk, unfamiliarity with the guideline, or complexity of calculating an individual dose. Therefore, we introduced a computerised clinical decision support system (CDSS) for vancomycin loading (hereafter Vancomycin CDSS) to promote the use of vancomycin loading dose. METHODS: We describe a quasi-experimental study spanning 6 months before and 18 months after the deployment of a Vancomycin CDSS. The Vancomycin CDSS was integrated into the hospital's electronic medical record system in the form of a vancomycin order set. Our primary endpoint was the incidence of nephrotoxicity; the secondary endpoint was mean initial vancomycin trough levels. We also conducted a survey to evaluate the reasons why clinicians opted not to utilise a vancomycin loading dose. RESULTS: After implementation of Vancomycin CDSS, 363 out of 746 patients (49 %) who were first administered vancomycin received a loading dose. We did not find significant differences in nephrotoxicity between the pre- and post-intervention groups, nor between the loading- and non-loading groups. In the pre-intervention group, the mean initial vancomycin trough level was 7.10 mg/L, which was significantly lower than that in the post-intervention group of 11.11 mg/L. In the vancomycin loading group, the mean initial trough level was 11.95 mg/L, compared to 7.55 mg/L in the non-loading group. The main reason stated for not prescribing a vancomycin loading dose was concern about nephrotoxicity. CONCLUSION: Introduction of the Vancomycin CDSS did not increase nephrotoxicity and increased the mean initial dose and trough level of vancomycin.

Increased Glucose Variability During Long-Term Therapeutic Hypothermia as a Predictor of Poor Neurological Outcomes and Mortality: A Retrospective Study.

Therapeutic hypothermia (TH) is considered as a treatment option in patients with stroke and brain injury for controlling intracranial pressure. A relatively longer duration of TH is required in such patients than in cardiac arrest patients. We aimed to investigate blood glucose parameters during TH that predict unfavorable neurological outcomes and mortality in patients admitted to the neurological or neurosurgical intensive care unit (ICU). This retrospective study evaluated electronic medical records of patients admitted to the ICU from January 1, 2012, to May 20, 2017. A total of 103 patients were included in the analyses. Multivariable analyses revealed that age and glycemic variability (GV) index were significantly associated with poor neurological outcomes (odds ratio [OR] 1.09, 95% confidence interval [CI] 1.03-1.15, p = 0.002, and OR 1.04, 95% CI 1.02-1.06, p < 0.001, respectively); furthermore, cumulative input-output balance, sequential organ failure assessment score, and glucose variability index were associated with 90-day mortality (hazard ratio [HR] 1.13, 95% CI 1.05-1.21, p < 0.001; HR 1.20, 95% CI 1.04-1.38, p = 0.010; and HR 1.01, 95% CI 1.01-1.02, p < 0.001, respectively). Receiver operating characteristic curve analyses of the GV index for prediction of 90-day mortality and poor neurological outcomes revealed that the areas under the curves were 0.747 (95% CI 0.65-0.85) and 0.826 (95% CI 0.75-0.91), respectively. In conclusion, variability in glucose levels may be valuable for predicting 90-day mortality and poor neurological outcomes in patients undergoing long-term TH.

Nutritional support and clinical outcomes in critically ill patients supported with veno-arterial extracorporeal membrane oxygenation.

BACKGROUND & AIMS: Patients undergoing veno-arterial extracorporeal membrane oxygenation (VA-ECMO) are likely to be develop malnutrition because of catabolism and protein consumption. Administration of appropriate nutrition to these patients is difficult because of hemodynamic instability and multiorgan failure. The aim of this study was to evaluate the relationship between nutritional supply and clinical outcomes in patients undergoing VA-ECMO. METHODS: Patients who received VA-ECMO in a single tertiary teaching hospital between 2013 and 2018 were reviewed retrospectively. Linear regression and Cox regression were performed to assess the relationship between the following factors and clinical outcomes: sex, age, BMI, modified nutrition risk in the critically ill (mNUTRIC) score, sequential organ failure assessment (SOFA) score, acute physiology and chronic health evaluation (APACHE II) score, ENCOURAGE score, daily average achievement of an energy target (%), and average protein intake during the first week and second week. RESULTS: Forty-one patients were included. Patients on VA-ECMO received lower amounts of energy and protein in the first week than in the second week (33.9 vs 77.7% target/day, 0.24 vs. 0.74 g/kg/day) and achieved 70% of their energy requirement at a median of 8 days after the initiation of VA-ECMO. Multiple Cox regression analysis revealed an association among energy received daily during the second week of VA-ECMO, mNUTRIC score, and 90-day mortality (hazard ratio, 0.82, 95% confidence interval [0.69-0.97], P = 0.018 vs. hazard ratio, 1.51, 95% confidence interval [1.06-2.15], P = 0.022). CONCLUSION: In VA-ECMO patients, when the daily average energy intake increased by 10% of the target over 8-14 days, the 90-day mortality decreased by 18%.

Development and Validation of Predictive Model for Salmonella Growth in Unpasteurized Liquid Eggs.

Liquid egg products can be contaminated with Salmonella spp. during processing. A predictive model for the growth of Salmonella spp. in unpasteurized liquid eggs was developed and validated. Liquid whole egg, liquid yolk, and liquid egg white samples were prepared and inoculated with Salmonella mixture (approximately 3 Log CFU/mL) containing five serovars (S. Bareilly, S. Richmond, S. Typhimurium monophasic, S. Enteritidis, and S. Gallinarum). Salmonella growth data at isothermal temperatures (5, 10, 15, 20, 25, 30, 35, and 40°C) was collected by 960 h. The population of Salmonella in liquid whole egg and egg yolk increased at above 10°C, while Salmonella in egg white did not proliferate at all temperature. These results demonstrate that there is a difference in the growth of Salmonella depending on the types of liquid eggs (egg yolk, egg white, liquid whole egg) and storage temperature. To fit the growth data of Salmonella in liquid whole egg and egg yolk, Baranyi model was used as the primary model and the maximum growth rate and lag phase duration for each temperature were determined. A secondary model was developed with maximum growth rate as a function of temperature. The model performance measures, bias factor (B f , 0.96-0.99) and r2 (0.96-0.99) indicated good fit for both primary and secondary models. In conclusion, it is thought that the growth model can be used usefully to predict Salmonella spp. growth in various types of unpasteurized liquid eggs when those are exposed to various temperature and time conditions during the processing.

Genotypic characterization of ESBL-producing E. coli from imported meat in South Korea.

Twenty extended-spectrum ß-lactamase (ESBL)-producing E. coli strains were isolated from imported meat in South Korea. ESBL strains of E. coli were detected in chicken (14/20) more often than in pork (6/20) and beef (0/20); the highest number (12/20) was detected in Brazilian meats. The blaCTX-M genes were predominant in meats from many countries. E. coli from pork imported from France produced the blaCTX-M-58 enzyme, which has never been documented previously in ESBL-producing bacteria from clinical or environmental sources. Additionally, the coexistence of the blaCTX-M-2 and blaOXA-1 enzymes in EC12-5 isolate was found for the first time in an ESBL E. coli isolate. A rare blaCTX-M type, blaCTX-M-25, was found in 40% of ESBL E. coli isolates. Phenotypic susceptibility testing showed that E. coli isolates were resistant to up to eleven antibiotics, including ciprofloxacin. For the first time, a new combination in an integron gene cassette, aacA4-cmlA6-qacEΔ1, was found in an E. coli isolate from poultry imported from Brazil. Three E. coli ST117 isolates, from an avian pathogenic lineage producing CTX-M-94, harbored fimH, fyuA, iutA, papC, rfc, and traT virulence genes and were not susceptible to quinolones. For the first time, rfc and papG virulence factors were detected in ESBL E. coli strains isolated from meat products. Even though E. coli CC21 and CC22 were obtained from meats from the USA and Brazil, respectively, they had a similarity coefficient higher than 99% in rep-PCR and the same MLST type (ST117), phenotypic antibiotic resistance pattern, integron gene (qacEΔ1), and plasmid DNA profile. This study indicates that imported meat products may be a source of ESBL-producing E. coli strains in South Korea.

Distribution and Molecular Characterization of Campylobacter Species at Different Processing Stages in Two Poultry Processing Plants.

The present study analyzed the prevalence and molecular characterization of Campylobacter at different processing steps in poultry slaughterhouses to determine where contamination mainly occurs. A total of 1,040 samples were collected at four different stages (preprocessing cloacal swabs, postevisceration, postwashing, and postchilling) in two processing plants. Campylobacter was detected in 5.8% (15 of 260) of the cloacal swabs and in 13.3% (104 of 780) of the processing samples. In both plants, the sampling points with the greatest contamination rates were after evisceration (20.5% and 15.4% for plants A and B, respectively) and significantly decreased after chilling (p < 0.05, from 20.5% to 10.9%) in plant A and after washing (from 15.4% to 2.9%) in plants B. In the result, however, the reduction in Campylobacter contamination was achieved through the sequential processing procedures in both plants. Campylobacter loads (>103 colony-forming units [CFUs]/mL) also decreased from 41.7% at evisceration to 20.0% in final carcasses. The genetic relationships of isolates were analyzed by the automated repetitive sequence-based polymerase chain reaction (rep-PCR) system, and the rep-PCR banding pattern was found to be unrelated to the processing plants, species, sampling point, or sampling day. As the gap in the intervention efficacy remains between plant A and B despite several consistencies, a national program for monitoring critical processing stages in poultry processing plants is recommended for the successful exportation of Korean-processed white mini broiler meat.

Prevalence Analysis and Molecular Characterization of Salmonella at Different Processing Steps in Broiler Slaughter Plants in South Korea.

In this study, changes in the prevalence of Salmonella during the processing of broiler chicken carcasses were investigated. A total of 1040 fecal swabs and chicken carcasses samples were collected from 2 processing plants at the 4 stages of broiler processing, which included live birds in slaughter line, postevisceration/prewashing, postwashing/prechilling, and postchilling, respectively. The intraspecific biodiversity of the Salmonella isolates was determined using a DiversiLab automated repetitive sequence-based PCR (rep-PCR) system. In both plants, the prevalence of Salmonella increased considerably after evisceration (from 4.6% to 30.8%, P < 0.05) and decreased after washing (from 30.8% to 25.4%, P < 0.05). However, the chilling step had little effect on Salmonella prevalence (from 25.4% to 22.7%, P > 0.05). The most frequent Salmonella serovar in plant A was Infantis (35.8%), followed by Enteritidis (26.2%) and Montevideo (15.0%), while Montevideo (43.6%) and Enteritidis (35.9%) were most prevalent in plant B. A difference in the rep-PCR banding pattern was found to be related to the processing plant origin and serovar rather than sampling point or sampling day, although there were some exceptional strains.

Short communication: Proteomic characterization of tuberculin purified protein derivative from Mycobacterium bovis.

Bovine tuberculin purified protein derivative (bPPD) is used as an intradermal test (IT) reagent to detect bovine tuberculosis (bTB) in most countries. Identification of bPPD proteins is critical to understanding the immunological reaction of IT at the molecular level. While bPPD from the United Kingdom (UK) and Brazil (BR) have been recently defined at the proteomic level, bPPD from the Republic of Korea (KR) has not yet been analyzed. Here, bPPD KR proteome was examined for the first time. In total, 271 proteins were identified, including Mycobacterium bovis-specific proteins Mb0854c and Mb2898, and 42 known T cell antigens. On comparing with proteomes of bPPD UK and BR, 33 proteins were found to be common among all three bPPDs, of which 15 proteins were T cell antigens. M. bovis-specific antigens with T cell activity in bPPD may be novel candidates for use as alternatives to currently available bPPD in diagnostics.

Antibiotic Resistance and Virulence Potentials of Shiga Toxin-Producing Escherichia coli Isolates from Raw Meats of Slaughterhouses and Retail Markets in Korea.

In this study, the prevalence of Shiga toxin-producing Escherichia coli (STEC) was investigated among raw meat or meat products from slaughterhouses and retail markets in South Korea, and their potential for antibiotic resistance and virulence was further analyzed. A total of 912 raw meats, including beef, pork, and chicken, were collected from 2008 to 2009. E. coli strains were frequently isolated in chicken meats (176/233, 75.9%), beef (102/217, 42.3%), and pork (109/235, 39.2%). Putative STEC isolates were further categorized, based on the presence or absence of the Shiga toxin (stx) genes, followed by standard O-serotyping. Polymerase chain reaction assays were used to detect the previously defined virulence genes in STEC, including Shiga toxins 1 and Shiga toxin 2 (stx1 and 2), enterohemolysin (ehxA), intimin (eaeA), STEC autoagglutination adhesion (saa), and subtilase cytotoxin (subAB). All carried both stx1 and eae genes, but none of them had the stx2, saa, or subAB genes. Six (50.0%) STEC isolates possessed the ehxA gene, which is known to be encoded by the 60-megadalton virulence plasmid. Our antibiogram profiling demonstrated that some STEC strains, particularly pork and chicken isolates, displayed a multiple drug-resistance phenotype. RPLA analysis revealed that all the stx1-positive STEC isolates produced Stx1 only at the undetectable level. Altogether, these results imply that the locus of enterocyte and effacement (LEE)-positive strains STEC are predominant among raw meats or meat products from slaughterhouses or retail markets in Korea.

Traceback investigation for Salmonella contamination at egg processing plants in South Korea: prevalence, antibiotic resistance, and epidemiological tracing by rep-PCR fingerprinting.

We conducted a survey of Salmonella from 8 egg-breaking plants and a farm to determine the prevalence and the source of the bacteria. The contents of 2400 shell eggs (20 eggs per pool), 75 pasteurized liquid egg products, and 120 unpasteurized liquid egg products from 8 egg-breaking plants in South Korea were examined. In liquid egg samples, 4 Salmonella-positive samples from 120 unpasteurized ones (3.3%) and 5 positive samples from 75 pasteurized ones (6.7%) were identified; no eggs were positive for Salmonella among shell egg samples. To trace the source of Salmonella, we revisited the 2 Salmonella-positive plants (plants A and C). We investigated the equipment and environments of the plants and a henhouse (farm A) that supplied shell eggs to plant A, and collected additional liquid eggs and shell eggs from plants A and C. All Salmonella isolates from plant A and the associated farm A, except for a single Typhimurium strain from farm A, were serotyped as Bareilly. Three serovars, including one Bareilly, four Tennessee, and one Richmond, were isolated from plant C. Most Salmonella isolates were susceptible to tested antibiotics. To identify differences between isolates, molecular subtyping by using the automated rep-PCR system was conducted. All Salmonella Bareilly (S. Bareilly) strains from plant A exhibited high similarity, indicating possible contamination by Salmonella strains from the henhouse A. Meanwhile, 2 S. Bareilly strains from plant C, one from liquid egg at the 1st visit and the other from container at the 2nd visit, exhibited identical antibiotic resistance and similar subtyping pattern, but clearly discriminated from the ones of plant A.

Comparison of the Microsatellite and Single Nucleotide Polymorphism Methods for Discriminating among Hanwoo (Korean Native Cattle), Imported, and Crossbred Beef in Korea.

The identity of 45 Hanwo and 47 imported beef (non-Hanwoo) samples from USA and Australia were verified using the microsatellite (MS) marker and single nucleotide polymorphism (SNP) methods. Samples were collected from 19 supermarkets located in the city of Seoul and Gyeonggi province, South Korea, from 2009 to 2011. As a result, we obtained a 100% concordance rate between the MS and SNP methods for identifying Hanwoo and non-Hanwoo beef. The MS method presented a 95% higher individual discriminating value for Hanwoo (97.8%) than for non-Hanwoo (61.7%) beef. For further comparison of the MS and SNP methods, blood samples were collected and tested from 54 Hanwoo × Holstein crossbred cattle (first, second, and third generations). By using the SNP and MS methods, we correctly identified all of the first-generation crossbred cattle as non-Hanwoo; in addition, among the second and third generation crossbreds, the ratio identified as Hanwoo was 20% and 10%, respectively. The MS method used in our study provides more information, but requires sophisticated techniques during each experimental process. By contrast, the SNP method is simple and has a lower error rate. Our results suggest that the MS and SNP methods are useful for discriminating Hanwoo from non-Hanwoo breeds.

In vitro activities of antimicrobials against Brucella abortus isolates from cattle in Korea during 1998-2006.

In vitro activities of 13 antibiotics were assessed against 85 Brucella abortus isolates from naturally infected cattle in the Republic of Korea during 1998-2006, using broth microdilution test. Tetracyclines showed the most excellent activity against B. abortus, displaying MIC values of 0.5 µg/ml or below. In particular, minocycline showed the lowest MIC50/90 values (0.125/0.125 µg/ml) in this study. Among four fluoroquinolones tested, ciprofloxacin (MIC50/90, 0.5/1 µg/ml) and norfloxacin (MIC50/90, 8/8 µg/ml) had the most and the least activities, respectively. Gentamicin (MIC50/90, 1/1 µg/ml) was more effective than streptomycin, erythromycin, rifampin, and chloramphenicol (MIC50/90, 2/2 µg/ml).

Quantitative Rose Bengal Test for diagnosis of bovine brucellosis.

The Rose Bengal Test (RBT) is the most widely used screening test for brucellosis in both humans and animals. Owing to its apparent simplicity of reading, however, interpretations of the RBT results can be affected by personal experience. This study describes a simple way to improve the accuracy and uniformity of reading the RBT reaction by counting the number of agglutinated particles using transparent OHP film with Quantity One, which was originally designed to count the bacterial colony numbers on agar plates. Using this system, the reactivities of three Rose Bengal antigens from different sources against international standard serum (1,000 units, VLA, UK) could be numerically measured: the intensity scale ranged from zero to around 1,600. This system enabled us to compare the antigenicity of Rose Bengal antigens from three different sources by using statistical analyses such as regression and mean intensity. Collectively, mathematical measuring of the reaction intensity used in this study may help interpret subtle test results by providing more reliable data and additional statistical information on the herd. In addition, the method would also be applicable to other agglutination test for other diseases.