Flexible PC-based workstation for auditory evoked potential and psychoacoustic experiments.
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Evoked Potentials, Auditory↗
Biomedical subjects
J G Wells
Publications and source records attributed to J G Wells.
Cholera in Piura, Peru: a modern urban epidemic.
In late January 1991, epidemic cholera appeared in Peru. Within 2 months, 7922 cases and 17 deaths occurred in Piura, a Peruvian city of 361,868. A hospital-based culture survey showed that 79%-86% of diarrhea cases were cholera. High vibriocidal antibody titers were detected in 34% of the asymptomatic population. A study of 50 case-patients and 100 matched controls demonstrated that cholera was associated with drinking unboiled water (odds ratio [OR], 3.9; 95% confidence interval [CI], 1.7-8.9), drinking beverages from street vendors (OR, 14.6; CI, 4.2-51.2), and eating food from street vendors (OR, 24.0; CI, 3.0-191). In a second study, patients were more likely than controls to consume beverages with ice (OR, 4.0; CI, 1.1-18.3). Ice was produced from municipal water. Municipal water samples revealed no or insufficient chlorination, and fecal coliform bacteria were detected in samples from 6 of 10 wells tested. With epidemic cholera spreading throughout Latin America, these findings emphasize the importance of safe municipal drinking water.
Adolescent↗
Diarrhea among African children born to human immunodeficiency virus 1-infected mothers: clinical, microbiologic and epidemiologic features.
Diarrhea and weight loss are common features of pediatric and adult human immunodeficiency type 1 (HIV-1) infection, particularly in developing countries. We studied prospectively episodes of diarrhea in 559 children, ages 10 to 15 months, participating in a longitudinal study of perinatal HIV-1 infection in Kinshasa, Zaire. Children with HIV-1 infection had more frequent episodes of diarrhea and were more likely to present with fever or moderate or severe dehydration and to have persistent or fatal diarrhea. Of 9 HIV-1-positive infants with diarrhea, 3 had enteroadherence factor-positive Escherichia coli, compared with 5 of 74 HIV-1-negative children with diarrhea (P = 0.04); no other pathogen was associated with HIV-1 infection. In a logistic regression model diarrhea was significantly associated with HIV-1 infection in the child, moderate or severe malnutrition and symptoms of acquired immunodeficiency syndrome in the mother. Diarrhea among children with perinatal HIV infection in Zaire is more severe than among uninfected children and is associated with malnutrition and advanced disease in the mother.
Cohort Studies↗
Covering the costs of care in neonatal intensive care units.
The continued rise of health care costs, despite private and governmental control efforts, has sustained cost containment as a central issue for health care researchers and policy makers. In keeping with these concerns, the Florida Health Care Cost Containment Board conducted a study of neonatal intensive care units (NICUs) in Florida to ascertain the costs, charges, and net revenues associated with NICU services in individual hospitals, to document cost shifting and cross-subsidization as a means of financing NICU care for indigent populations, and to assess the fiscal impact of NICUs in state-sponsored vs non-state-sponsored Regional Perinatal Intensive Care Center hospitals providing NICU care. Hospitals in the state-sponsored program reported a loss of approximately $16.5 million in contrast to the non-state-sponsored hospitals, which reported a gain of $1 million. Payment being generated by private-pay patients amounted to almost 60% of total revenues but constituted less than one third of the costs in state-sponsored hospitals, indicating a high level of cost shifting. Government support of state-sponsored NICUs, while substantial, has been insufficient; increasing constraints on this funding source would likely worsen the deficit and increase the necessity of cost shifting.
Ancillary Services, Hospital↗
The use of plasmid profiles and nucleic acid probes in epidemiologic investigations of foodborne, diarrheal diseases.
The application of nucleic acid analyses to investigations of infectious disease outbreaks has resulted in useful molecular strain markers that distinguish the epidemic clone of a particular pathogen and help identify specific vehicles of infection. We have successfully used plasmid profile analysis, restriction endonuclease digestion of plasmid and whole-cell DNAs, and nucleic acid hybridization to investigate recent outbreaks of foodborne diarrheal illness. Plasmid analysis has been important in identifying epidemic strains of Salmonella enteritidis and Escherichia coli O157:H7. In a culture survey of S. enteritidis isolates from humans and a variety of animals, including chickens and chicken eggs, we identified 16 distinct plasmid profiles and used these to differentiate strains, especially within commonly occurring phage types (Colindale 8 and 13a). HindIII digests of plasmid DNA were useful in distinguishing plasmids of similar mass but dissimilar enzyme target sequences; they clearly distinguished S. enteritidis strains causing systemic infections in children in parts of Africa from U.S. isolates. Investigations of outbreaks of hemorrhagic colitis have also been assisted by plasmid analysis. Restriction endonuclease digests of whole-cell DNA and Southern blot analysis, hybridizing with E. coli 16S and 23S rRNA (ribotyping), have been effective subtyping techniques, especially for plasmidless isolates of Campylobacter jejuni. In five outbreaks of C. jejuni infections, ribotyping of PvuII and ClaI digests distinguished individual epidemic strains within one commonly occurring C. jejuni serotype (Penner 2, Lior 4). Preliminary data show that ribotyping of NcoI digests can also distinguish individual epidemic strains of E. coli O157:H7 and may provide a more stable marker than plasmid profiles. Specific DNA probes derived from cloned virulence genes of E. coli have been invaluable in epidemic investigations and surveys. Using colony hybridization, we found in one survey of stool specimens from 174 dairy cattle that 11% of animals were asymptomatically carrying Shiga-like toxigenic E. coli other than O157:H7. We also found that newly synthesized oligonucleotide probes for the Shiga-like toxins I and II agreed 100% with cloned gene probes in a study of 613 E. coli strains. Future studies of these organisms will include the use of additional synthetic oligonucleotides as primers to amplify the toxin genes directly in patient and animal specimens by the polymerase chain reaction. There is a continuing and expanding role for molecular approaches in epidemiological investigations. The DNA methods described above are not based on the often complex expression of phenotypic characteristics, and, unlike sensitive and specific techniques such as phage typing, a single method can be used to study a variety of Gram-positive and negative bacterial pathogens.
Animals↗
Escherichia coli O157:H7, a cause of hemorrhagic colitis and hemolytic uremic syndrome.
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Colitis↗
Isolation of Escherichia coli serotype O157:H7 and other Shiga-like-toxin-producing E. coli from dairy cattle.
We examined 1,266 fecal specimens from healthy cattle during the investigations of two sporadic cases of hemolytic uremic syndrome associated with raw milk consumption and an outbreak of gastroenteritis and hemolytic uremic syndrome caused by Escherichia coli serotype O157:H7. We collected specimens from heifers, calves, and adult cows on 22 farms, in a stockyard, and in a packing house. We also collected 3 raw hamburger specimens from a restaurant and 23 raw milk samples from two farms. All specimens were examined for E. coli O157:H7 by using sorbitol-MacConkey agar, H immobilization, O157 agglutination, and tissue culture cytotoxicity. E. coli O157:H7 was isolated from 16 heifers or calves and 1 adult cow on 22 farms, 1 stockyard calf, 2 beef specimens, and 1 raw milk sample. Selected fecal specimens were also examined for the presence of other Shiga-like-toxin-producing E. coli (SLTEC) by testing polymyxin B extracts of colony sweeps and then testing individual colonies for toxin production. SLTEC other than O157 was isolated from 8 of 10 farms investigated and from the stockyard; 8% of adult cows and 19% of heifers and calves were positive for SLTEC. Several animals were positive for SLTEC by colony sweep only. This investigation demonstrates that dairy cattle are a reservoir of E. coli O157:H7 and other SLTEC.
Animals↗
Recommendations for collection of laboratory specimens associated with outbreaks of gastroenteritis.
Recent discoveries have implicated a number of "new" (i.e., previously unrecognized) infectious agents as important causes of outbreaks of gastroenteritis. Unfortunately, the ability to detect these agents in an outbreak can be limited by two factors: 1) the lack of appropriate assays-many of which are still in developmental stages and are not readily available to clinical laboratories, and 2) inadequately or improperly collected specimens. At CDC, many newly developed assays are being used for research and for outbreak investigations. The information in this report is especially intended for public health agencies that collaborate with CDC in investigating outbreaks of gastroenteritis. The report provides an update on guidelines and recommendations for the proper collection of specimens to be sent to CDC, gives general background information concerning some recently discovered pathogens, lists some of the tests available at CDC, and provides a list of CDC contacts. The guidelines and the general information provided on causes of outbreaks of gastroenteritis can be also used by public health workers for investigations when specific testing is available and appropriate.
Adult↗
A comparison of alkaline phosphatase and radiolabelled gene probes with bioassays for enterotoxigenic Escherichia coli.
Alkaline phosphatase-conjugated oligonucleotide probes (APO), 32P-labelled oligonucleotide (RO) and cloned polynucleotide (RP) probes were evaluated for their ability to detect enterotoxigenic Escherichia coli (ETEC) as defined by bioassay. These three sets of probes were applied to 301 E. coli strains that had previously been defined by the Y1 adrenal cell assay for heat-labile enterotoxin (LT) and the infant mouse assay for heat-stable enterotoxin (ST). The correlation of the APO probe for LT with the bioassay was 98% with five discrepancies and a positive predictive value (PPV) of 100%. For the APO/ST probe the correlation with the bioassay was 98% with seven discrepancies and a PPV of 96%. The correlation of the RO probe for LT was 99% with four discrepancies and a PPV of 100%, while the overall correlation for the two RO/ST probes was 97% with eight discrepancies and a PPV of 97%. For the RP probes, the correlation for LT was 99% with four discrepancies and a PPV of 100% and for ST was 98% with seven discrepancies and a PPV of 98%. These findings suggest that the APO probes were as sensitive as the RO and RP probes in detecting ETEC by colony hybridization and could be a practical alternative to bioassays and radiolabelled probes for ETEC since they do not require expensive equipment or extensive technical training.
Alkaline Phosphatase↗
Hemolytic-uremic syndrome during an outbreak of Escherichia coli O157:H7 infections in institutions for mentally retarded persons: clinical and epidemiologic observations.
PURPOSE: To describe an outbreak of Escherichia coli O175:H7 infection resulting in a high rate of progression to hemolytic-uremic syndrome, and to attempt to identify predictors of and risk factors for progression. DESIGN: Case-control study among employees and comparison of daily clinical features in two groups: infected residents with subsequent development of HUS and those who had no complications. SETTING: Two institutions for retarded persons in Utah. PATIENTS: Twenty residents with E. coli O157:H7 infection (13 culture confirmed, 2 probable, and 5 possible); HUS developed in 8, and 4 died. Thirty-one infected employees (3 with culture-confirmed, 6 with probable, and 22 with possible infection). MEASUREMENTS AND MAIN RESULTS: In a case-control study among employees, infection was independently associated with eating ground beef from a single lot prepared at several barbecues and with close contact with a resident who had diarrhea. Five of eight residents in whom HUS developed had received trimethoprim-sulfamethoxazole, compared with none of seven who had no subsequent complications (p = 0.026); this finding may reflect antimicrobial treatment of patients with more severe illness. Compared with infected residents without complications, persons with HUS were younger (median age 13 vs 27 years, p = 0.043) and, by the third day of illness, had higher leukocyte counts (median 23.7 X 10(9)/L vs 9.1 X 10(9)/L, p = 0.018) and temperature (median 38.5 degrees C vs 37.0 degrees C, p = 0.016). Leukocytosis peaked on day 4, more than 24 hours before signs of HUS appeared. CONCLUSIONS: Food-borne outbreaks of E. coli O157:H7 in institutions may have devastating effects. Leukocytosis and fever may precede and predict HUS in patients with E. coli O157:H7 infection.
Adolescent↗
Epidemiologic evidence that prior antimicrobial exposure decreases resistance to infection by antimicrobial-sensitive Salmonella.
Exposure to antimicrobials is known to increase the risk of infection with antimicrobial-resistant strains of Salmonella, but this effect has not been previously demonstrated with antimicrobial-sensitive strains. The effect of prior antimicrobial exposure was studied during a multistate outbreak of salmonellosis caused by an antimicrobial-sensitive strain of Salmonella havana: 19 (26%) of 72 persons infected had taken an antimicrobial within 30 days before onset of symptoms. Antimicrobial therapy was begun a mean of 15.9 days before and stopped a mean of 7.9 days before onset. In a case-control study, 11 (31%) of 35 case-patients had taken antimicrobials within 30 days of onset compared with 9 (13%) of 70 age- and neighborhood-matched controls (matched odds ratio, 4.3; 95% confidence interval, 1.3, 13.5). The association remained when controlled for the presence of underlying illness or immunosuppression. Prior antimicrobial exposure appears to increase the risk of infection with antimicrobial-sensitive and resistant strains of Salmonella. The delay between antimicrobial use and onset of symptoms suggests that the effect may be due to prolonged alteration of the colonic bacterial flora, resulting in decreased resistance to colonization.
Adolescent↗
Antimicrobial resistance of Shigella isolates in the USA: the importance of international travelers.
A nationwide sample of Shigella isolates was collected and tested for resistance to 12 antimicrobial agents to assess the prevalence and epidemiologic correlates of antimicrobial resistance in Shigella. Of the isolates, 32% were resistant to ampicillin, 7% to trimethoprim-sulfamethoxazole, and 0.4% to nalidixic acid. Fifty (20%) of 252 isolates were associated with foreign travel. The best predictor of clinically important resistance was a history of foreign travel: 20% of isolates from foreign travelers showed trimethoprim-sulfamethoxazole resistance, compared with only 4% of isolates from those without such a history. Quinolone resistance was not identified in travel-related isolates, and quinolones may be more appropriate for initial therapy of travel-related shigellosis than is trimethoprim-sulfamethoxazole.
Anti-Bacterial Agents↗
A large outbreak of antibiotic-resistant shigellosis at a mass gathering.
In July 1987, a large outbreak of shigellosis occurred among attendees at a mass gathering in a national forest, the annual Rainbow Family Gathering. Sanitation in the campsite was poor, allowing widespread transmission of disease, probably by food, water, and person-to-person spread. The attack rate may have been greater than 50% among the estimated 12,700 attendees. The outbreak was caused by Shigella sonnei, resistant to ampicillin, tetracycline, and trimethoprim-sulfamethoxazole; the organism was of colicin type 9 and contained a 90-kilobase plasmid not found in non-outbreak-related strains. The dispersal of the group resulted in nationwide dissemination of the organism, and outbreaks in three states were linked to transmission from attendees at the Gathering. This outbreak demonstrates the potential for rapid dissemination of disease in such a setting and the necessity for careful planning of mass gatherings.
Age Factors↗
Epidemic cholera in West Africa: the role of food handling and high-risk foods.
During an epidemic of cholera in Guinea, West Africa, in 1986, the authors conducted two studies of risk factors for transmission. In the capital city, 35 hospitalized cholera patients were more likely than 70 neighborhood-matched controls to have eaten leftover peanut sauces (odds ration (OR) = 3.1, 95% confidence interval (CI) 1.2-8.2), but less likely to have eaten tomato sauces (OR = 0.2, 95 percent CI 0.1-0.9). Hand washing with soap before meals by all family members protected against cholera (OR = 0.2, 95 percent CI 0.02-0.96), suggesting that persons asymptomatically infected with Vibrio cholerae 01 may have been the initial source for contamination of the leftover foods. Laboratory studies demonstrated that V. cholerae multiplied rapidly in peanut sauce (pH 6.0), but not in the more acidic tomato sauce (pH 5.0). In an outbreak of cholera-like illness after a rural funeral, illness was strongly associated with eating a rice meal served over many hours without reheating. These studies demonstrated that, in this epidemic, many cases of severe cholera were associated with eating specific cooked foods that could support bacterial growth after contamination of these foods with V. cholerae within the household. Epidemic control efforts should include identification of high-risk foods and promotion of simple changes in food handling behaviors to lower the risk of foodborne transmission.
Adolescent↗
A statewide outbreak of Escherichia coli O157:H7 infections in Washington State.
In November 1986, a statewide outbreak of Escherichia coli O157:H7 infections in Washington State was identified after a physician in an eastern Washington community hospitalized three patients with hemorrhagic colitis which progressed to thrombotic thrombocytopenic purpura. Epidemiologic investigation identified 37 cases in this community and linked the illnesses to a local restaurant which had served ground beef that was the suspected initial vehicle of transmission. The plasmid profile and toxin production pattern (Shiga-like toxin II alone) of the outbreak strain provided a unique strain marker. E. coli O157:H7 infections caused by this strain were simultaneously seen in other parts of the state among nursing home residents and in patients with the hemolytic-uremic syndrome, and an increase in sporadic cases of hemorrhagic colitis was noted at a Seattle health maintenance organization. It is suspected that a contaminated product, probably ground beef distributed statewide, was the common source. Tracing of this meat led to farms where rectal swabs from six (1%) of 539 cattle tested yielded E. coli O157:H7, although the plasmids and toxin production patterns of these isolates differed from the human outbreak strain. Introduction of a single strain of E. coli O157:H7 has the potential to cause widespread concurrent outbreaks. Such outbreaks are likely to escape recognition until heightened screening and surveillance for E. coli O157:H7 is established.
Adolescent↗
Enteric disease in rabbits inoculated with stool filtrates from persons with chronic diarrhea.
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Animals↗
Development and evaluation of enzyme-linked immunosorbent assays for detection of shiga-like toxin I and shiga-like toxin II.
Shiga-like toxin (SLT)-producing Escherichia coli has been associated with a spectrum of human illnesses, including hemorrhagic colitis and hemolytic uremic syndrome. It produces at least two antigenically distinct toxins designated SLT-I and SLT-II, which have been implicated in disease. Currently available toxin assays, however, are not suitable for most clinical or public health laboratories. In this study, we have developed two sandwich enzyme-linked immunosorbent assays (ELISAs) based on toxin-specific murine monoclonal capture antibodies and rabbit polyclonal second antibodies which are specific for SLT-I and SLT-II. The SLT-I ELISA detected 200 pg of purified SLT-I, and the SLT-II ELISA detected 75 pg of purified SLT-II. The types of SLT produced by 166 human and 54 animal isolates of E. coli that produced moderate to high levels of toxin were determined by the ELISA, and results were confirmed by cytotoxin neutralization assays. With the exception of results from three strains, the tests agreed on the types of toxin present. DNA probe assays of 86 of 87 isolates also agreed with the ELISA and neutralization results. Although the SLT-II ELISA was specific for the SLT-II variant produced by porcine edema strains, most of the isolates examined produced levels of toxin (less than 50 50% cytotoxic doses [CD50] per ml) below the detection limit of the test. The ELISAs were not sufficiently sensitive to consistently detect low levels of toxin (less than 50 CD50 per ml) found in fecal extracts. On the basis of these findings, both ELISAs appeared to detect significant levels of SLT-I ( > 100 CD50 per ml) and SLT-II ( > 50 CD50 per ml) in E. coli culture extracts and should be useful diagnostic tools in many microbiology laboratories.
Animals↗
Illnesses associated with Escherichia coli O157:H7 infections. A broad clinical spectrum.
STUDY OBJECTIVE: To describe the spectrum of illnesses associated with Escherichia coli O157:H7 infections. DESIGN: Described an outbreak that showed the broad spectrum of these infections. Reviewed the clinical findings in the other eight major outbreaks reported between 1982 and 1986. Also reviewed reports of sporadic cases. SETTING: Outbreaks in communities, nursing homes, a day care center, and a kindergarten. CASES: Persons identified in outbreaks of E. coli O157:H7 infections. RESULTS: Escherichia coli O157:H7 infection causes bloody diarrhea (hemorrhagic colitis), nonbloody diarrhea, the hemolytic uremic syndrome, and thrombotic thrombocytopenic purpura. Infection can be asymptomatic, can involve extraintestinal sites, and can be fatal. Bloody diarrhea is the commonest symptom. Most patients have severe abdominal cramps; fever is documented in less than half. Findings from fecal leukocyte examinations often suggest a noninfectious cause. Results of radiologic and colonoscopic examinations can be consistent with a diagnosis of inflammatory bowel disease or ischemic colitis. Patients at the extremes of age are at increased risk for E. coli O157:H7-associated diarrhea, the hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, and death. Antimicrobial agents have not been shown to modify the illness, but there are few data on individual agents. CONCLUSION: Infection with E. coli O157:H7 should be considered in all patients with bloody diarrhea, the hemolytic uremic syndrome, or thrombotic thrombocytopenic purpura because the infection can masquerade as gastrointestinal bleeding of noninfectious cause, the antecedent diarrhea may be resolved and forgotten by the time the hemolytic uremic syndrome or thrombotic thrombocytopenic purpura is diagnosed, and the detection of E. coli O157:H7 requires specific stool culture techniques.
Adolescent↗