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Biomedical subjects

P A Blake

Publications and source records attributed to P A Blake.

At least 19 recordsLinked to original sources
PubMed2004

Rapid evaluation of risk of white particulate matter in blood components by a statewide survey of transfusion reactions.

BACKGROUND: In January 2003, white particulate matter (WPM) was detected in blood components. Because the composition and cause of WPM was not understood at that time, there was uncertainty about whether WPM could endanger patient safety. To investigate possible adverse patient events associated with WPM, transfusion reaction rates were examined. STUDY DESIGN AND METHODS: A questionnaire was distributed to Georgia medical centers. Data collected included the number of components transfused and reported adverse reactions by component type from January 2002 through January 2003, and date, reaction type, and blood supplier for events in January 2003. RESULTS: Of 124 transfusion services contacted, 108 (87%) responded. During the survey period, there were 1213 reported transfusion reactions and 528,412 units transfused, or 2.3 reactions per 1000 units transfused; for RBCs, 2.4 (range, 1.8-3.1); plasma, 1.5 (range, 0.6-3.5); and PLTs, 3.4 (2.1-5.4) per 1000 units. Transfusion reaction rates by component for January 2003 did not differ significantly from the rate for January 2002 or for the calendar year. The 86 reported reactions that occurred in January 2003 were attributed to bacterial contamination (n = 2, 2.3%), other febrile nonhemolytic (n = 49, 57.0%), allergic (n = 14, 16.3%), and "other" reactions (n = 21, 24.4%); the proportions of reaction types did not differ significantly during the month. CONCLUSION: No overall changes in reported adverse reaction rates occurred over the survey period or in the proportion of reaction types during January 2003 when WPM was detected. Statewide surveillance of transfusion reactions could be useful to evaluate potential threats to blood safety.

Blood Specimen Collection↗
PubMed2001

Lice, nits, and school policy.

BACKGROUND: The epidemiology of head lice infestation is poorly understood. Many schools treat all children with nits as though they are contagious. Children with nits but no lice are often removed from school until they are treated and all visible nits are removed. OBJECTIVE: To investigate the probability that children with nits alone will become infested with lice. DESIGNS: Prospective cohort study. SETTING: Two metropolitan Atlanta elementary schools. PARTICIPANTS: A total of 1729 children were screened for head lice. Twenty-eight children (1.6%) had lice, whereas 63 (3.6%) had nits without lice. Fifty of the 63 children (79%) with nits alone completed follow-up. OUTCOME MEASURE: Conversion (ie, becoming infested with lice) within 14 days after initial screening. RESULTS: Nine of 50 children (18.0%) followed for nits alone converted. Although children who converted did not have significantly more nits than did nonconverters, having nits near the scalp was a risk factor for conversion. Seven of 22 children (31.8%) with >/=5 nits within one fourth inch of the scalp converted, compared with 2 of 28 children (7.1%) with fewer (relative risk: 4.45; 95% confidence interval: 1.03-19.35). This risk remained statistically significant after separately stratifying for sex, recent treatment, and total number of nits. CONCLUSIONS: Although having >/=5 nits within one fourth inch of the scalp was a risk factor for conversion, most children with nits alone did not become infested. Policies requiring exclusion from school and treatment for all children with nits alone are likely excessive. Instead, these children may benefit from repeated examination to exclude the presence of crawling lice.lice, pediculus, lice infestations, pediatrics, school.

Animals↗
PubMed2000

Factors influencing a communitywide campaign to administer hepatitis A vaccine to men who have sex with men.

OBJECTIVES: A hepatitis A outbreak among men who have sex with men (MSM) led to a publicly funded vaccination campaign. We evaluated the MSM community's response. METHODS: A cohort of MSM from 5 community sites was surveyed. RESULTS: Thirty-four (19%) of 178 potential vaccine candidates received the vaccine during the campaign. We found a linear relation between the number of exposures to campaign information and the likelihood of vaccination (P < .001). Vaccination was independently associated with awareness of the outbreak and the vaccine, having had sexual relations with men for 12 years or longer, having recently consulted a physician, and routinely reading a local gay newspaper. CONCLUSIONS: The difficult task of vaccinating MSM can be aided by repetitive promotional messages, especially via the gay media.

Adult↗
PubMed1999

A Mexican restaurant-associated outbreak of Salmonella Enteritidis type 34 infections traced to a contaminated egg farm.

In May 1996, the Georgia Division of Public Health was notified about a cluster of persons with Salmonella Enteritidis (SE) infections in Waycross, Georgia. A matched pair case-control study to determine risk factors for illness found a statistically significant association of SE infection with a history of having eaten at Restaurant A during the 5 days before onset of illness (relative risk = 13 [95% confidence interval (CI) = 3-62, P < 0.01]). In a second case-control study, to determine specific food exposures, consumption of a deep-fried Mexican dish (chile relleno) (4 of 21 cases vs. 0 of 26 controls, odds ratio undefined, 95% CI > 1.46, P = 0.034) was found to be significantly associated with SE infection. An environmental investigation found evidence of suboptimal food storage and cooking temperatures at Restaurant A; cross contamination of foods may have contributed to the low attributable risk identified for chile rellenos. Five of 37 Restaurant A food and environment specimens yielded SE strains. All five positive specimens were from chiles rellenos. Of the seven outbreak-associated strains (six patient isolates and one food isolate from Restaurant A) for which phage typing was conducted, all were phage type 34. A FDA traceback investigation through Restaurant A's single-egg supplier identified the potential source as three interrelated farms in South Carolina. Environmental culture from one of these farms yielded SE phage type 34. As a result of this outbreak, FDA helped institute a statewide egg quality-assurance programme in South Carolina to minimize SE contamination of eggs.

Animal Husbandry↗
PubMed1997

Postlicensure effectiveness of varicella vaccine during an outbreak in a child care center.

CONTEXT: Because lyophilized varicella vaccine must be stored frozen at -15 degrees C or less (> or = 5 degrees F) and administered within 30 minutes after reconstitution, the potential exists for decreased vaccine effectiveness when the vaccine is used under field conditions. OBJECTIVES: To describe an outbreak of varicella in a child care center and to determine postlicensure effectiveness of varicella vaccine. DESIGN: Retrospective cohort study. SETTING: A child care center in DeKalb County, Georgia, in 1996. PARTICIPANTS: Of the 184 children registered in the child care center, 148 were eligible for the study based on absence of history of varicella before January 1, 1996. MAIN OUTCOME MEASURES: Data on disease status, severity and impact of disease, and risk factors for varicella and for vaccine failure were obtained from parents and their children's pediatricians. Varicella vaccine effectiveness was calculated among children aged 12 months or older (eligible for vaccination) using the cohort method. RESULTS: The outbreak started on January 17, 1996, and lasted 15 weeks. Of the 148 eligible children, 81 (55%) developed varicella. Cases among children younger than 12 months (n =7) were more severe than cases among older children. Varicella occurred in 9 (14%) of 66 vaccinated children and 72 (88%) of 82 unvaccinated children. Varicella was less severe and resulted in fewer days of absence from the child care center among vaccinated compared with unvaccinated cases. Varicella vaccine effectiveness against all forms of disease was 86% (95% confidence interval [CI], 73%-92%), and against moderate-to-severe varicella disease it was 100% (95% CI, 96%-100%). Vaccinated children with asthma or other reactive airway diseases were 7.1 times more likely to have varicella than were vaccinated children without reactive airway diseases (95% CI, 2.4-21.3). CONCLUSIONS: Varicella vaccine administered under routine conditions in physicians' offices was highly effective in preventing varicella in an outbreak characterized by intense exposure. The role of asthma and other reactive airway diseases as risk factors for varicella disease and vaccine failure deserves to be investigated further.

Asthma↗
PubMed1995

Communitywide shigellosis: control of an outbreak and risk factors in child day-care centers.

OBJECTIVES: The study's objectives were to assess (1) control of a community outbreak of shigellosis through the promotion of handwashing, (2) risk factors in day-care centers, and (3) shigellosis attributable to attendance at a day-care center. METHODS: In 1991, an outbreak of Shigella sonnei infections occurred in Lexington-Fayette County, Ky; 14 licensed child day-care centers were involved. Communitywide promotion of hand washing was instituted along with diarrhea surveillance. A case-control study compared day-care centers that had confirmed cases of shigellosis with centers that had none. A family transmission study determined those cases attributable to attendance at day-care centers. RESULTS: The outbreak abated 3 weeks after the interventions' initiation. Day-care centers with outbreaks were more likely than those with no cases to have a food handler who changed diapers and to provide transportation for children from their homes to the center. These centers also had a higher toddler-to-toilet ratio than control centers (21 vs 12). In 58% of families with shigellosis, the first person with diarrhea during the outbreak was a child younger than 6 years; 92% of diarrheal illnesses among these children were attributable to day-care attendance. CONCLUSIONS: Community involvement in increasing hand washing most likely resulted in control of this shigellosis outbreak. Diarrhea prevention strategies in day-care centers could prevent substantial communitywide disease.

Case-Control Studies↗
PubMed1994

Epidemic cholera in Trujillo, Peru 1992: utility of a clinical case definition and shift in Vibrio cholerae O1 serotype.

Epidemic cholera continues in Peru. Since 1991, cholera surveillance in Peru has been based mainly on clinical recognition. To determine the proportion of reported cholera patients who actually have cholera and to evaluate the clinical case definition used in surveillance, we cultured rectal swabs from patients presenting with acute diarrhea in March 1992 in Trujillo, Peru. Of 197 patients meeting the clinical case definition, 174 (88%) had confirmed Vibrio cholerae O1 infection. In this epidemic setting, watery diarrhea of sudden onset in a person of any age presenting for treatment is highly predictive of cholera. Of note, 90% of the current V. cholerae O1 El Tor isolates were of serotype Ogawa, while a year earlier, all were of serotype Inaba.

Acute Disease↗
PubMed1993

The molecular epidemiology of cholera in Latin America.

To explain the sudden appearance and rapid spread of cholera in Latin America in January 1991, molecular techniques were used to define Vibrio cholerae O1 isolates from around the world. Restriction fragment length polymorphisms of rRNA and ctxA genes, DNA sequence of cholera toxin B subunit gene ctxB, and multilocus enzyme electrophoresis data were used to characterize 197 isolates. Worldwide, there are at least four distinct toxigenic El Tor V. cholerae O1 clones: the seventh pandemic (Eastern Hemisphere), US Gulf Coast, Australian, and Latin American. Nontoxigenic V. cholerae O1 previously isolated in Brazil, Mexico, and Peru are unlike current toxigenic isolates. The Latin American clone probably represents an extension of the seventh pandemic into the Western Hemisphere, while the US Gulf Coast clone most likely evolved separately. These data will be useful in monitoring the spread of cholera, determining the origin of outbreaks in both hemispheres, and implicating specific vehicles of transmission.

Alleles↗
PubMed1993

Pathogen-specific risk factors and protective factors for acute diarrheal disease in urban Brazilian infants.

To evaluate potential risk factors and protective factors for acute diarrheal disease in urban infants, 500 infants < or = 12 months old with diarrhea and 500 age-matched control subjects coming to a São Paulo emergency room were studied. On multivariate analysis, these apparently sporadic community-acquired cases of diarrhea were significantly associated with hospitalization in the month before onset (odds ratio [OR], 3.4), day care center exposure (OR, 2.0), prior diarrhea in another household member (OR, 4.4), and low family income (OR, 1.8). Breast-feeding infants < 6 months old (OR, 0.3) and boiling household drinking water (OR, 0.4) were protective. Enteropathogenic Escherichia coli (EPEC; OR, 12.0) and Salmonella (OR, 7/0, discordant pairs) infections were associated with prior hospitalization, rotavirus infections were associated with day care (OR, 6/0), and breast-feeding was protective against EPEC infections (OR, 0.1). These results suggest that certain preventive strategies can prevent a substantial proportion of cases of diarrheal disease in Brazilian infants.

Acute Disease↗
PubMed1993

Typhoid fever at a resort hotel in New York: a large outbreak with an unusual vehicle.

The largest outbreak of typhoid fever in the United States since 1981 occurred in 1989 among guests and staff at a New York hotel. There were 43 culture-confirmed and 24 probable cases among guests, 1 culture-confirmed case and 1 asymptomatic culture-positive case among hotel employees, and 1 culture-confirmed secondary case. Twenty-one persons were hospitalized and 2 had bowel perforation. Breakfast on 13 June was the only meal consumed by all ill persons (relative risk, infinite; P = .004). In a case-control study, case-patients were more likely than controls to have consumed orange juice (odds ratio, 5.6; 95% confidence interval, 1.1-54.7), which had been prepared in a 208-L container with ample opportunity for hand contact. No other food was associated with illness. S. typhi was isolated from the stool of an asymptomatic food worker who handled orange juice but who was not known to be a typhoid carrier. S. typhi is a foodborne pathogen with continuing potential to cause large outbreaks in the United States.

Beverages↗
PubMed1993

Epidemiology of cholera in the Americas.

A persisting reservoir of the Gulf Coast strain of toxigenic V. cholerae O1 in Louisiana and Texas marshes and the shipment of seafood from these areas throughout the United States means that sporadic cases and outbreaks of cholera may occur anywhere in the country for the foreseeable future. Such cases are most likely to occur during warm months, especially between July and October. Physicians should think of cholera when consulted for severe watery diarrhea, even when the patient has no history of travel, and alert the laboratory. Experience has shown that US food and water sanitation is good enough to make either secondary transmission or large outbreaks unlikely; however, as long as we have foodborne and waterborne outbreaks of bacterial enteric diseases, the Gulf Coast strain may appear in a situation in which it can multiply and be ingested in large numbers by many people. The Latin American cholera epidemic has caused more cases of cholera in the United States in 2 years than the total of Gulf Coast strain cases identified during the past 20 years. The epidemic's future is uncertain. Despite knowing a great deal about cholera epidemiology, we cannot fully explain the ebb and flow of cholera epidemics. We do not know why cholera was apparently eliminated from the Western Hemisphere by 1900, nor can we predict which areas will be affected next or whether cholera will remain in a given area transiently or become endemic. The fact that cholera disappeared from the Western Hemisphere in the last century does not necessarily mean that it will disappear again. The situation is different now in several ways. The current pandemic is caused by the El Tor biotype, which persists better in the environment than does the classical biotype. Travel is now more frequent and more rapid. Finally, the population of the Western Hemisphere is about 14 times larger now than it was in 1850 and produces about 80,000 metric tons of human feces each day, of which only a fraction is treated. Thus, cholera will probably become endemic in Latin America and persist indefinitely.

Americas↗
PubMed1992

Use of plasmid profiles to differentiate strains within specific serotypes of classical enteropathogenic Escherichia coli.

1. The usefulness of plasmid profile analysis to differentiate strains of enteropathogenic Escherichia coli (EPEC) was evaluated by studying 123 strains of the most prevalent serotypes causing infant diarrhea in the city of São Paulo, Brazil, i.e., O111ab:H-, O111ab:H2 and O119:H6. 2. No common profiles were found among strains of distinct serotypes. However, within each serotype, most of the strains were grouped within a few major profiles. More than 68% of the strains of serotypes O111ab:H- and O111ab:H2 were included in 6 and 9 major profiles, respectively. In serotype O119:H6, about 48% of the strains were included in 3 major profiles. 3. This analysis suggests that only a few EPEC clones are causing infant diarrhea in São Paulo and revealed that the distribution of serotypes O111ab:H- and O111ab:H2 during the one-year study was at least partly determined by small outbreaks of the most common profiles. 4. We conclude that plasmid profile analysis is very useful to differentiate strains within specific EPEC serotypes.

Brazil↗
PubMed1991

Cholera in Africa: lessons on transmission and control for Latin America.

In January, 1991, epidemic cholera emerged in Peru and spread to 7 other countries of Latin America. Cholera was introduced 20 years ago to Africa, where it spread rapidly to 30 of the 46 countries of the region and by 1990 accounted for 90% of all cases reported to the World Health Organisation. Many lessons from the cholera epidemic in Africa are relevant to efforts to control the disease in Latin America. Public health practices from the past--quarantine and cordon sanitaire to halt introduction of cholera by travellers, and vaccination and mass chemoprophylaxis to control epidemics--are ineffective in preventing spread of the disease. Cholera can be transmitted not only by contaminated water but also by food. Social phenomena such as mass migrations and burial practices may play a greater role than previously understood. While efforts to prevent the spread of cholera have been ineffective, cholera-associated mortality can be decreased with rehydration therapy. Since the current pandemic is unlikely to retreat soon, new strategies are urgently needed to control the spread of cholera through sanitary and behavioural interventions or improved vaccines.

Africa↗
PubMed1991

A new look at typhoid vaccination. Information for the practicing physician.

Most cases of typhoid fever in the United States occur in international travelers, with the greatest risk associated with travel to Peru, India, Pakistan, and Chile. Laboratory workers and household contacts of long-term carriers are also at greater risk than the general population. Decisions to the use typhoid vaccine involve weighing the risk of illness against the risk of vaccine reactions. Until recently, the only typhoid vaccine commercially available to US civilians was a heat-phenol-inactivated parenteral product that is 51% to 77% effective in preventing typhoid fever but frequently produces local pain and swelling, fever, headache, and malaise. A new orally administered, live-attenuated vaccine, made from the Ty21a strain of Salmonella typhi, has been recently licensed in the United States. This vaccine provides equivalent protection with a much lower incidence of adverse reactions. It is administered in a four-dose series given over 7 days. Since neither vaccine offers total protection, the most important elements in prevention of typhoid fever remain sound biosafety precautions in laboratory workers and care in selecting food and beverages by those traveling to areas where typhoid fever is endemic.

Capsules↗
PubMed1991

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↗