James E Keen

Cook County Health and Hospitals System, Chicago, Illinois, United States

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Publications (63)177.33 Total impact

  • John D Keen, James Keen
    Archives of internal medicine 03/2012; 172(5):447. · 11.46 Impact Factor
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    ABSTRACT: Cattle are a major reservoir for Shiga toxin-producing Escherichia coli O157 (STEC O157) and harbor multiple genetic subtypes that do not all associate with human disease. STEC O157 evolved from an E. coli O55:H7 progenitor; however, a lack of genome sequence has hindered investigations on the divergence of human- and/or cattle-associated subtypes. Our goals were to 1) identify nucleotide polymorphisms for STEC O157 genetic subtype detection, 2) determine the phylogeny of STEC O157 genetic subtypes using polymorphism-derived genotypes and a phage insertion typing system, and 3) compare polymorphism-derived genotypes identified in this study with pulsed field gel electrophoresis (PFGE), the current gold standard for evaluating STEC O157 diversity. Using 762 nucleotide polymorphisms that were originally identified through whole-genome sequencing of 189 STEC O157 human- and cattle-isolated strains, we genotyped a collection of 426 STEC O157 strains. Concatenated polymorphism alleles defined 175 genotypes that were tagged by a minimal set of 138 polymorphisms. Eight major lineages of STEC O157 were identified, of which cattle are a reservoir for seven. Two lineages regularly harbored by cattle accounted for the majority of human disease in this study, whereas another was rarely represented in humans and may have evolved toward reduced human virulence. Notably, cattle are not a known reservoir for E. coli O55:H7 or STEC O157:H(-) (the first lineage to diverge within the STEC O157 serogroup), which both cause human disease. This result calls into question how cattle may have originally acquired STEC O157. The polymorphism-derived genotypes identified in this study did not surpass PFGE diversity assessed by BlnI and XbaI digestions in a subset of 93 strains. However, our results show that they are highly effective in assessing the evolutionary relatedness of epidemiologically unrelated STEC O157 genetic subtypes, including those associated with the cattle reservoir and human disease.
    Molecular Biology and Evolution 02/2012; 29(8):2047-62. · 14.31 Impact Factor
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    ABSTRACT: Visna/Maedi, or ovine progressive pneumonia (OPP) as it is known in the United States, is an incurable slow-acting disease of sheep caused by persistent lentivirus infection. This disease affects multiple tissues, including those of the respiratory and central nervous systems. Our aim was to identify ovine genetic risk factors for lentivirus infection. Sixty-nine matched pairs of infected cases and uninfected controls were identified among 736 naturally exposed sheep older than five years of age. These pairs were used in a genome-wide association study with 50,614 markers. A single SNP was identified in the ovine transmembrane protein (TMEM154) that exceeded genome-wide significance (unadjusted p-value 3×10(-9)). Sanger sequencing of the ovine TMEM154 coding region identified six missense and two frameshift deletion mutations in the predicted signal peptide and extracellular domain. Two TMEM154 haplotypes encoding glutamate (E) at position 35 were associated with infection while a third haplotype with lysine (K) at position 35 was not. Haplotypes encoding full-length E35 isoforms were analyzed together as genetic risk factors in a multi-breed, matched case-control design, with 61 pairs of 4-year-old ewes. The odds of infection for ewes with one copy of a full-length TMEM154 E35 allele were 28 times greater than the odds for those without (p-value<0.0001, 95% CI 5-1,100). In a combined analysis of nine cohorts with 2,705 sheep from Nebraska, Idaho, and Iowa, the relative risk of infection was 2.85 times greater for sheep with a full-length TMEM154 E35 allele (p-value<0.0001, 95% CI 2.36-3.43). Although rare, some sheep were homozygous for TMEM154 deletion mutations and remained uninfected despite a lifetime of significant exposure. Together, these findings indicate that TMEM154 may play a central role in ovine lentivirus infection and removing sheep with the most susceptible genotypes may help eradicate OPP and protect flocks from reinfection.
    PLoS Genetics 01/2012; 8(1):e1002467. · 8.52 Impact Factor
  • John D. Keen, James E. Keen
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    ABSTRACT: PURPOSE Digital mammography has experienced rapid growth despite lack of cost-effectiveness (Tosteson 2008). Furthermore, the linkage to CAD risks decreased specificity from CAD induced recall exams (Fenton 2007). Economic analysis of the conversion to digital from film requires knowing the market penetration of CAD in United States (U.S.) mammography facilities and the price differentials for digital vs. film screening. METHOD AND MATERIALS Using a random sample, we conducted a telephone survey of 400, or 4.6%, of the 8651 Mammography Quality Standard Act of 1992 (MQSA) certified mammography facilities excluding U.S. territories as of August 2007. Between January and March of 2008, we called the phone number as listed in the FDA database and asked if the facility provided digital or film screening mammograms as well as technical, professional, or global cash prices. We also asked if the facility used “computer-aided detection.” We made additional calls as needed. RESULTS 367/400 or 92% of facilities provided basic responses. Overall, 238/367 or 64.8% used CAD, while 140/367 or 38.1% claimed digital technology. For digital facilities, 128 of 140 (91.4%, 85.5 to 95.5 95% CI) used CAD, while only 110 of 227 (48.5%, 41.8 to 55.2 95% CI) film-only facilities used CAD. CAD usage by digital differed significantly from film facilities (odds ratio 11.4, 5.9 to 25.0 95% CI). Only one facility had optional CAD, or 0.3%. We obtained global prices from 252/400 or 63% of facilities. For the n=98 digital, the median/mean prices were $250/$263, and for the n=154 film $176/$192, (median difference $74, p<0.0001). For the n=83 Film/CAD, the median price was $198 vs. $153 for the n=71 Film/noCAD (difference $45, p<0.004). For the 91 Dig/CAD facilities, the median price was $260 (difference with Film/noCAD $107, p <0.0001). 38 facilities provided separate CAD prices: median $43, no difference digital vs. film. Average insurance reimbursements compiled by radiology benefits manager National Imaging Associates for 2008 for Dig/CAD ($209) and Film/noCAD ($118) show a new technology premium of 77% vs. 70% for cash. CONCLUSION In 2008 over 90% of digital facilities used CAD. Dig/CAD price differentials versus film without CAD are substantial. CLINICAL RELEVANCE/APPLICATION Widespread use of CAD is likely compromising any presumed accuracy benefit from digital technology, and their combined adoption has significantly increased screening resource costs versus film.
    Radiological Society of North America 2011 Scientific Assembly and Annual Meeting; 11/2011
  • John D. Keen, James E. Keen
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    ABSTRACT: PURPOSE Between the ages of 30 and 50, about 1000 single-phase CT scans of the abdomen and pelvis will induce one future cancer over a lifetime. Surveillance Epidemiology and End Results (SEER) data show half of all cancers are lethal, so the absolute death risk is 0.5/1000, the same as the absolute benefit from 10 years of routine screening mammography. Given widespread innumeracy, we wanted to provide another perspective to promote insight into the radiation harm from the typical CT scan. METHOD AND MATERIALS We obtained the projected number of future cancers related to overall CT scan use in the United States in 2007 by age at exposure from a recent analysis. Since the cancer types were not broken down by race or sex, we calculated combined life expectancy estimates by using the gamma-mixed exponential (GAME) method, which required the United States Life Table for 2005 and SEER 10 year survival statistics for each cancer diagnosed in 1996. We assumed CT exposure at age 30 and age 50, with worst-case cancer induction at 5 years as well as at 20 years for age 50. We calculated years lost in life expectancy along with a utility loss assuming a chronic cancer state of 88% of normal health. RESULTS At age 50, the normal life expectancy is 30 years. The top five lethal cancers for life expectancy are pancreas 1.2, liver 1.8, lung 2.9, esophagus 3.5, and stomach 4.9 years. With equal cancer induction, the years lost are 13.9 and utility loss is 1.4 years. With CT weighted cancer induction, the total life loss is 16.7 years. Lung cancer contributes 30%, followed by stomach at 13%, leukemia and colon at 10%, liver at 7%, oral at 6%, bladder and brain at 5%, pancreas at 4%, and breast at 3%. For cancer induction at 5 years, the loss averages 3.6 days for every CT scan. At 20 years induction, the loss averages 8.9 years per cancer and 1.9 days per scan. At age 30 and life expectancy of 49 years, the loss averages 30 years per cancer and 7.4 days per scan. We did not discount the results. CONCLUSION For a CT scan at age 50, the percentage total life loss from a CT induced cancer at worse is 16.7/30.5 years or 54%. Every CT patient between the ages of 30 and 50 loses on average between 2 days and 1 week of life expectancy. CLINICAL RELEVANCE/APPLICATION Since the average life gain per mammogram for 40-year-old women routinely screened for 10 years is about 1 day (undiscounted), should radiologists inform their patients that CT scans take lives?
    Radiological Society of North America 2010 Scientific Assembly and Annual Meeting; 12/2010
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    ABSTRACT: To compare methods for identification of bulls that were carriers for Tritrichomonas foetus during an outbreak on a large beef ranch and determine whether the percentage of nonpregnant cows was associated with the percentage of bulls infected with T foetus. Epidemiological study. 121 Angus and Hereford bulls (1.5 to 6 years old) and 2,960 Angus-cross cows (2.5 to 14 years old) managed as 5 herds on a Nebraska beef ranch. 3 sequential preputial scrapings collected from the bulls at 12- to 27-day intervals were cultured, and cultures were examined for live T foetus daily for 5 days. On day 5, aliquots of the culture fluid were tested by means of T foetus-specific gel and real-time PCR assays. Cows were tested for pregnancy by means of rectal palpation. For 361 preputial scrapings obtained from 121 bulls, results of culture and gel PCR assay were in close agreement. The real-time PCR assay had similar sensitivity to culture and the gel PCR assay but generated more false-positive results. Twenty-four of the 121 (19.8%) bulls were identified as infected with T foetus. For the 5 ranch herds, there was a positive linear correlation between percentage of infected bulls (range, 0% to 40%) and percentage of nonpregnant cows (range, 8.3% to 19.2%). Results suggested that a combination of culture and the gel PCR assay performed on 3 sequential preputial scrapings was the best method for identifying bulls that were carriers for T foetus during this herd outbreak.
    Journal of the American Veterinary Medical Association 11/2010; 237(9):1068-73. · 1.72 Impact Factor
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    ABSTRACT: Shiga-toxigenic Escherichia coli (STEC) O157 occurrence was determined along the entire gastrointestinal tract (GIT) of each of four naturally shedding cattle and at three sites in 61 slaughter cattle. STEC O157 was distributed along the entire GIT, though interanimal distribution was variable. Neither feces nor rectoanal-junction samples accurately predicted the STEC O157-negative status of any particular animal.
    Applied and Environmental Microbiology 08/2010; 76(15):5278-81. · 3.95 Impact Factor
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    ABSTRACT: The intestinal microbiota of beef cattle are important for animal health, food safety, and methane emissions. This full-length sequencing survey of 11,171 16S rRNA genes reveals animal-to-animal variation in communities that cannot be attributed to breed, gender, diet, age, or weather. Beef communities differ from those of dairy. Core bovine taxa are identified.
    Applied and Environmental Microbiology 07/2010; 76(14):4858-62. · 3.95 Impact Factor
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    ABSTRACT: The objectives of the study described here were (i) to investigate the dynamics of Escherichia coli O157:H7 fecal and hide prevalence over a 9-month period in a feedlot setting and (ii) to determine how animals shedding E. coli O157:H7 at high levels affect the prevalence and levels of E. coli O157:H7 on the hides of other animals in the same pen. Cattle (n = 319) were distributed in 10 adjacent pens, and fecal and hide levels of E. coli O157:H7 were monitored. When the fecal pen prevalence exceeded 20%, the hide pen prevalence was usually (25 of 27 pens) greater than 80%. Sixteen of 19 (84.2%) supershedder (>10(4) CFU/g) pens had a fecal prevalence greater than 20%. Significant associations with hide and high-level hide (>/=40 CFU/100 cm(2)) contamination were identified for (i) a fecal prevalence greater than 20%, (ii) the presence of one or more high-density shedders (>/=200 CFU/g) in a pen, and (iii) the presence of one or more supershedders in a pen. The results presented here suggest that the E. coli O157:H7 fecal prevalence should be reduced below 20% and the levels of shedding should be kept below 200 CFU/g to minimize the contamination of cattle hides. Also, large and unpredictable fluctuations within and between pens in both fecal and hide prevalence of E. coli O157:H7 were detected and should be used as a guide when preharvest studies, particularly preharvest intervention studies, are designed.
    Applied and Environmental Microbiology 09/2009; 75(20):6515-23. · 3.95 Impact Factor
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    ABSTRACT: Cattle are a reservoir of Shiga toxin-producing Escherichia coli O157:H7 (STEC O157), and are known to harbor subtypes not typically found in clinically ill humans. Consequently, nucleotide polymorphisms previously discovered via strains originating from human outbreaks may be restricted in their ability to distinguish STEC O157 genetic subtypes present in cattle. The objectives of this study were firstly to identify nucleotide polymorphisms in a diverse sampling of human and bovine STEC O157 strains, secondly to classify strains of either bovine or human origin by polymorphism-derived genotypes, and finally to compare the genotype diversity with pulsed-field gel electrophoresis (PFGE), a method currently used for assessing STEC O157 diversity. High-throughput 454 sequencing of pooled STEC O157 strain DNAs from human clinical cases (n = 91) and cattle (n = 102) identified 16,218 putative polymorphisms. From those, 178 were selected primarily within genomic regions conserved across E. coli serotypes and genotyped in 261 STEC O157 strains. Forty-two unique genotypes were observed that are tagged by a minimal set of 32 polymorphisms. Phylogenetic trees of the genotypes are divided into clades that represent strains of cattle origin, or cattle and human origin. Although PFGE diversity surpassed genotype diversity overall, ten PFGE patterns each occurred with multiple strains having different genotypes. Deep sequencing of pooled STEC O157 DNAs proved highly effective in polymorphism discovery. A polymorphism set has been identified that characterizes genetic diversity within STEC O157 strains of bovine origin, and a subset observed in human strains. The set may complement current techniques used to classify strains implicated in disease outbreaks.
    Genome biology 06/2009; 10(5):R56. · 10.30 Impact Factor
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    John D Keen, James E Keen
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    ABSTRACT: We analyzed the claim "mammography saves lives" by calculating the life-saving absolute benefit of screening mammography in reducing breast cancer mortality in women ages 40 to 65. To calculate the absolute benefit, we first estimated the screen-free absolute death risk from breast cancer by adjusting the Surveillance, Epidemiology and End Results Program 15-year cumulative breast cancer mortality to account for the separate effects of screening mammography and improved therapy. We calculated the absolute risk reduction (reduction in absolute death risk), the number needed to screen assuming repeated screening, and the survival percentages without and with screening. We varied the relative risk reduction from 10%-30% based on the randomized trials of screening mammography. We developed additional variations of the absolute risk reduction for a screening intervention, including the average benefit of a single screen, as well as the life-saving proportion among patients with earlier cancer detection. Because the screen-free absolute death risk is approximately 1% overall but rises with age, the relative risk reduction from repeated screening mammography is about 100 times the absolute risk reduction between the starting ages of 50 and 60. Assuming a base case 20% relative risk reduction, repeated screening starting at age 50 saves about 1.8 (overall range, 0.9-2.7) lives over 15 years for every 1000 women screened. The number needed to screen repeatedly is 1000/1.8, or 570. The survival percentage is 99.12% without and 99.29% with screening. The average benefit of a single screening mammogram is 0.034%, or 2970 women must be screened once to save one life. Mammography saves 4.3% of screen-detectable cancer patients' lives starting at age 50. This means 23 cancers must be found starting at age 50, or 27 cancers at age 40 and 21 cancers at age 65, to save one life. The life-saving absolute benefit of screening mammography increases with age as the absolute death risk increases. The number of events needed to save one life varies depending on the prospective screening subset or reference class. Less than 5% of women with screen-detectable cancers have their lives saved.
    BMC Medical Informatics and Decision Making 05/2009; 9:18. · 1.60 Impact Factor
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    ABSTRACT: To identify cases, describe the outbreak, implement control measures, and identify factors associated with infection or protection from infection, including contact with animals and hand hygiene practices. Case finding, a case-control study of 45 cases and 188 controls, environmental investigation, and molecular subtyping of clinical and environmental Escherichia coli O157:H7 isolates. The 2004 North Carolina State Fair. Case patients were fair visitors who had laboratory-confirmed E coli O157 infections, hemolytic uremic syndrome (HUS) diagnoses, or bloody diarrheal illnesses. Control subjects were recruited from a randomized list of persons who had purchased fair tickets online. Environmental samples from the fairgrounds were obtained from locations that had held animals during the fair. Main Exposure Visiting a petting zoo. Case finding: Summary descriptive statistics of suspected, probable, or confirmed E coli O157:H7 infections, signs, symptoms, and HUS. Environmental investigation: E coli O157:H7 isolates, pulsed-field gel electrophoresis patterns, and spatial distribution of source locations. Case-control study: Odds ratios (ORs) comparing reported fair-related activities, hygiene practices, and zoonotic disease knowledge with outcome. A total of 108 case patients were ascertained, including 41 with laboratory-confirmed illness and 15 who experienced HUS. Forty-five case patients and 188 controls were enrolled in the case-control study. Visits to a petting zoo having substantial environmental E coli O157:H7 contamination were associated with illness (age-adjusted OR, 8.2; 95% confidence interval [CI], 3.3-20.3). Among children 5 years or younger who had visited the implicated petting zoo, contact with animal manure (OR, 6.9; 95% CI, 2.2-21.9) and hand-to-mouth behaviors (OR, 10.6; 95% CI, 2.0-55.0) were associated with illness. Reported hand hygiene practices did not differ significantly (OR, 1.8; 95% CI, 0.3-9.5). Reported awareness of the risk for zoonotic disease was protective (OR, 0.1; 95% CI, 0.03-0.5). Environmental samples from the petting zoo implicated in the case-control study yielded E coli O157:H7, with indistinguishable pulsed-field gel electrophoresis patterns from the predominant strain. We describe one of the largest petting zoo outbreaks of E coli O157:H7 to date. Persons became infected after contact with manure and engaging in hand-to-mouth behaviors in a petting zoo having substantial E coli O157:H7 contamination. Use of alcohol-based hand-sanitizing gels was not protective, although knowledge of the risk for zoonotic infection was protective. Future investigations in similar outbreaks should assess risks for infection and protective measures (eg, physical barriers separating visitors from animal manure, education, and appropriate hand hygiene practices).
    JAMA Pediatrics 02/2009; 163(1):42-8. · 4.28 Impact Factor
  • John D. Keen, James E. Keen
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    ABSTRACT: PURPOSE To expand the concept of informed medical decision making regarding screening, we calculated the average life expectancy for a woman diagnosed with breast cancer. We derived the percentage life expectance (PLE) by dividing this average by the normal life expectancy. For comparison, we calculated the PLE for patients with other types of cancer. METHOD AND MATERIALS We obtained the life expectancy for patients with invasive breast cancer and ductal carcinoma in situ (DCIS) by using Surveillance Epidemiology and End Results (SEER) survival statistics prior to and after widespread population screening. For lung, ovarian, colon, cervical, and prostate cancer we used the most recent SEER 10 year survival data for diagnosis in 1993. We applied the gamma mixed-exponential (GAME) method to estimate life expectancy for the average cancer patient using United States life tables for women and men in 2003. We applied the declining exponential approximation for life expectancy (DEALE) for DCIS. RESULTS A woman age 50 has a normal life expectancy of 32.4 years, and if diagnosed with invasive breast cancer after no screening she can expect to live at least 20 years, or 61% of her normal life expectancy. This survival is based on 1980 breast cancer therapy. At age 40 and 60, the PLE values are 59% and 64%. The age 50 PLE for 1993 survival data is 77%, which reflects the effects of screening bias, screening benefit, and better therapy. The pre-screen PLE for DCIS is 90%, or 29.2 years. For comparison, a 50 year old woman diagnosed with invasive lung, ovarian, colon, and cervical cancer has a PLE of about 11%, 36%, 51%, and 71%. A 50 year old man with lung, colon, and prostate cancer can expect to live 10%, 54%, and 96% of his normal life expectancy of 28.5 years. CONCLUSION A woman diagnosed with invasive breast cancer will live on average about two-thirds of her normal life expectancy assuming she does not get screening, similar to cervical cancer patients. Women with DCIS have a similar outcome to a man with prostate cancer. CLINICAL RELEVANCE/APPLICATION Life expectancy estimates may be a convenient way to present cancer lethality and the relationship between diagnosis risk and death risk before screening, and thus support informed decision making.
    Radiological Society of North America 2008 Scientific Assembly and Annual Meeting; 12/2008
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    John D Keen, James E Keen
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    ABSTRACT: In order to promote consumer-oriented informed medical decision-making regarding screening mammography, we created a decision model to predict the age dependence of the cancer detection rate, the recall rate and the secondary performance measures (positive predictive values, total intervention rate, and positive biopsy fraction) for a baseline mammogram. We constructed a decision tree to model the possible outcomes of a baseline screening mammogram in women ages 35 to 65. We compared the single baseline screening mammogram decision with the no screening alternative. We used the Surveillance Epidemiology and End Results national cancer database as the primary input to estimate cancer prevalence. For other probabilities, the model used population-based estimates for screening mammography accuracy and diagnostic mammography outcomes specific to baseline exams. We varied radiologist performance for screening accuracy. The cancer detection rate increases from 1.9/1000 at age 40 to 7.2/1000 at age 50 to 15.1/1000 at age 60. The recall rate remains relatively stable at 142-157/1000, which varies from 73-236/1000 at age 50 depending on radiologist performance. The positive predictive value of a screening mammogram increases from 1.3% at age 40 to 9.8% at age 60, while the positive predictive value of a diagnostic mammogram varies from 2.9% at age 40 to 19.2% at age 60. The model predicts the total intervention rate = 0.013*AGE2 - 0.67*AGE + 40, or 34/1000 at age 40 to 47/1000 at age 60. Therefore, the positive biopsy (intervention) fraction varies from 6% at age 40 to 32% at age 60. Breast cancer prevalence, the cancer detection rate, and all secondary screening mammography performance measures increase substantially with age.
    BMC Medical Informatics and Decision Making 10/2008; 8:40. · 1.60 Impact Factor
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    ABSTRACT: Escherichia coli O157:H7 can live undetected in the gut of food animals and be spread to humans directly and indirectly. Bacteriophages are viruses that prey on bacteria, offering a natural, nonantibiotic method to reduce pathogens from the food supply. Here we show that a cocktail of phages isolated from commercial cattle feces reduced E. coli O157:H7 populations in the gut of experimentally inoculated sheep. A cocktail of phages was used in order to prevent the development of resistance to the phages. In our first in vivo study we found that our cocktail of phages reduced E. coli O157:H7 populations in the feces of sheep (p < 0.05) by 24 hours after phage treatment. Upon necropsy, populations of inoculated E. coli O157:H7 were reduced by phage treatment in both the cecum (p < 0.05) and rectum (p < 0.1). In our second in vivo study, several ratios of phage plaque-forming units (PFU) to E. coli O157:H7 colony-forming units (CFU) were used (0:1, 1:1, 10:1, and 100:1 PFU/CFU) to determine the most efficacious phage dose. A 1:1 ratio of phage to bacteria was found to be more effective (p < 0.05) than either of the higher ratios used (10:1 or 100:1). Ruminal levels of E. coli O157:H7 were not significantly reduced (p > 0.10) in any of the studies due to relatively low inoculated E. coli O157:H7 ruminal populations. Our results demonstrate that phage can be used as a preharvest intervention as part of an integrated pathogen reduction scheme.
    Foodborne Pathogens and Disease 05/2008; 5(2):183-91. · 2.28 Impact Factor
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    L M Durso, J E Keen
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    ABSTRACT: To quantify the effect of enrichment, immunomagnetic separation (IMS), and selective plating procedures on isolation of Shiga-toxigenic Escherichia coli O157 (STEC O157) and non-Shiga-toxigenic Escherichia coli O157 (non-STEC O157) from naturally contaminated bovine faeces. Two broth enrichment times, two IMS strategies, and two selective plating media were evaluated. STEC O157 and non-STEC O157 strains were often isolated from the same faecal specimen and responded differently to the isolation protocols. A large-volume IMS system was more sensitive than a conventional small-volume IMS method, but was also more expensive. STEC O157 was more frequently isolated from 6 h enriched broth and ChromAgar plates containing 0.63 mg l(-1) potassium tellurite (TCA). Non-STEC O157 was more frequently isolated from un-enriched broth and ChromAgar plates without tellurite (CA). The combination of 6-h enrichment in Gram-negative broth containing vancomycin, cefixime and cefsuludin, large volume IMS and selective plating on TCA maximized STEC O157 recovery from naturally contaminated cattle faecal specimens. The pairing of proper enrichment with a specific plating procedure is key for STEC O157 recovery from naturally contaminated bovine faeces. Incorporating tellurite into an E. coli O157 detection strategy may select for the subset of E. coli O157 that contains the Shiga-toxin genes.
    Journal of Applied Microbiology 01/2008; 103(6):2457-64. · 2.20 Impact Factor
  • John D. Keen, James Edward Keen
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    ABSTRACT: PURPOSE In order to promote unbiased professional recommendations, we analyzed the marginal cost and marginal benefit of digital screening mammography performed at a hypothetical "expert" center rather than a random film screening facility. METHOD AND MATERIALS We assumed "expert" mammography centers are represented by the Digital Mammographic Screening Trial (DMIST) participants. We used a previously developed decision model of subsequent screening mammography, and assumed a 50 year old woman would face the cash price of a screening mammogram. We assumed that hypothetical "expert" breast imaging specialists work at the DMIST facilities, and would read at about one "great" or two "stellar" positive standard deviations above the mean. This gives a sensitivity of 85% or 95%, and specificity of 95% or 98%, instead of 78%/92% national averages for radiologists. We calculated the fair price to justify the "expert" skill assuming a value of $100K per year of life saved at 3% discount. We compared this price to the previously obtained national average digital and film price and the "expert" digital price. RESULTS The median DMIST cash price was $337 (95% CI 271-383, n=27). This compares to $241 (95% CI 216-276,n=24) for digital and $173 (95% CI 156-188,n=137) for film from a random survey of mammogram facilities. Increased specificity results in lower false recall costs, while increased sensitivity improves the cancer detection rate. The "fair" price would be $203 per digital mammogram for "great" readers and $246 for "stellar" readers. Applying the national cash price of $241 to "great" readers cost $500K/life year, while "stellar" readers cost $80K/life year. Only 3 of 27 DMIST facilities have fair prices. CONCLUSION Using society guidelines, "expert" digital breast imaging specialists can only charge at most a premium of $30 to $68 to justify the marginal benefit of their skill, not $164. Most "expert" centers would have to lower their prices to be a "good deal" to educated consumers in a competitive market. CLINICAL RELEVANCE/APPLICATION The claim that women should go to a digital breast imaging specialist instead of a general radiologist ignores costs and requires a means to identify expert performance, and is therefore problematic.
    Radiological Society of North America 2007 Scientific Assembly and Annual Meeting; 11/2007
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    ABSTRACT: PURPOSE Organizations including the American College of Physicians, the National Insitute of Health and others have promoted the concept of informed medical decision making regarding screening. We investigated the practices of a sample of "expert" mammography centers regarding this concept. METHOD AND MATERIALS We assumed informed decision making requires balancing the marginal benefit with the marginal cost (including financial price). We assumed that "expert" mammography centers were represented by the 31 U.S. centers participating in the Digital Mammographic Imaging Screening Trial (DMIST) sponsored by the National Cancer Institute (NCI). In April of 2006, we called the center telephone number listed in the Food and Drug Administration (FDA) database of screening facilities. We asked for a recommendation from anyone for a website that could provide information about digital and screening mammography. We called a second time in March of 2007 and asked for the total cash price for a screening mammogram. We called additional numbers as needed. We also confirmed if the center used digital or computer aided detection (CAD) technology. We recorded the time it took to get an answer. RESULTS Regarding the first survey on websites, 5 centers had persistent voicemails, and 7 had no recommendation. Three sites could not be found, and 6 were hospital or radiology departments. Ten centers had balanced information: one had its own site, one recommended the NCI (www.cancer.gov) and one the American Cancer Society, while 7 had patient education sites linked to the NCI. Regarding prices, 27 of 31 centers provided total prices after a median wait time of 7 minutes. Twenty of 30 could answer the CAD question (13 yes). The median total price was $337 (95% CI 271-383). CONCLUSION Only 32% of centers recommended a website with balanced information about mammography. While 67% provided CAD information, 87% provided price information. Based on a small sample, it is debateable whether expert mammography centers promote informed decision making about screening. CLINICAL RELEVANCE/APPLICATION Expert mammography centers can easily set a better example for the radiology profession as consultants in promoting consumer oriented education about screening.
    Radiological Society of North America 2007 Scientific Assembly and Annual Meeting; 11/2007
  • John D. Keen, James Edward Keen
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    ABSTRACT: PURPOSE The recommended recall rate of 10% for screening mammography has no quantitative justification. We wanted to find the age dependence of the optimal decision thresholds for a single baseline and subsequent screening mammogram, and to determine if current recall rates are reasonable. METHOD AND MATERIALS Receiver operating characteristic (ROC) analysis predicts that the optimal false positive fraction (FPF) for a screening exam is a function of disease prevalence. We obtained age dependent breast cancer incidence and prevalence data from a national database. We used a previously developed decision model to calculate the cost of a false positive decision for a single baseline and subsequent mammogram. The false positive fraction (FPF) is close to the recall rate in a screening setting. We used previously developed life expectancy estimates and the life saving rate of mammography at ages 40, 50, and 60 to determine the utility of a true positive decision. We valued years of life saved at $50K/life year (LY) and $100K/LY and applied a discount rate of 3%. We ignored excess potential lawsuit costs for a false negative decision. ROC and average recall performance data were based on Breast Cancer Surveillance Consortium data. RESULTS The optimal decision thresholds depend on age and the value assumed for a year of life saved. For baseline mammography at age 50, the optimal FPF/TPF pair is about 7%/79% at $50K/LY and 14%/88% at $100K/LY. For 100K/LY, the FPF decreases to 9% at age 40, and increases to 17% at age 60. The national FPF/TPF/recall average is 14.1/89%/14.7%. For subsequent mammography at age 50, the operating points are 2%/57% at 50K/LY, and 5%/70% at 100K/LY. For $100K/LY the thresholds are 2%/47% at age 40, and 6%/73% at age 60. The national averages are 7.5%/77%/7.8%. CONCLUSION Baseline mammography recall rates for women over 50 are reasonable assuming a high society value per year of life saved. However, for subsequent mammography and lower life year values, recall rates are above optimal, especially for women under 50. CLINICAL RELEVANCE/APPLICATION Advocates of higher recall rates underestimate false positive costs, especially in younger women. Economic theory predicts higher income women would prefer a higher recall rate.
    Radiological Society of North America 2007 Scientific Assembly and Annual Meeting; 11/2007
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    ABSTRACT: To evaluate risk behaviors for transmission of zoonotic diseases at petting zoos during a period without a recognized disease outbreak. Observational survey with environmental microbiologic sampling. 6 petting zoos in Tennessee. Attendees were observed for animal and environmental contact, eating or drinking, hand-to-face contact, and use of a hand sanitizer. Hands were examined via bacteriologic culture on some attendees. Environmental samples were collected at three petting zoos. 991 attendees were observed; of these, 74% had direct contact with animals, 87% had contact with potentially contaminated surfaces in animal contact areas, 49% had hand-to-face contact, and 22% ate or drank in animal contact areas. Thirty-eight percent used hand sanitizer; children had better compliance than adults. Results of bacteriologic cultures of hands were negative for Salmonella spp and Escherichia coli O157; Salmonella spp were isolated from 63% and E coli O157 from 6% of the environmental samples. High risk behaviors were common among petting zoo visitors, and disease prevention guidelines were inconsistently followed. This is an example of the importance of one-medicine, one-health initiatives in protecting the public health. Veterinarians, venue operators, and public health authorities must work together on targeted education to improve implementation of existing disease prevention guidelines.
    Journal of the American Veterinary Medical Association 11/2007; 231(7):1036-8. · 1.72 Impact Factor

Publication Stats

2k Citations
177.33 Total Impact Points

Institutions

  • 2012
    • Cook County Health and Hospitals System
      Chicago, Illinois, United States
  • 1996–2012
    • United States Department of Agriculture
      • Agricultural Research Service (ARS)
      Washington, D. C., DC, United States
  • 2010
    • Lawrence Berkeley National Laboratory
      • Environmental Energy Technologies Division
      Berkeley, California, United States
  • 2009
    • University of Nebraska at Lincoln
      • Department of Veterinary Medicine and Biomedical Sciences
      Lincoln, Nebraska, United States
  • 2008–2009
    • Cook County Hospital
      • Department of Radiology
      Chicago, Illinois, United States
    • Agricultural Research Service
      Kerrville, Texas, United States
  • 2005
    • Texas A&M University
      College Station, Texas, United States
  • 2002
    • The Ohio State University
      • Department of Veterinary Preventive Medicine
      Columbus, OH, United States
  • 1995
    • Università degli Studi di Torino
      • Dipartimento di Scienze Veterinarie
      Torino, Piedmont, Italy