Biomedical subjects

L K Pickering

Publications and source records attributed to L K Pickering.

At least 37 records · Page 2Linked to original sources

PubMed1999

Molecular epidemiology of childhood astrovirus infection in child care centers.

This study assessed the role of human astrovirus (HAstV) in outbreaks and sporadic cases of diarrhea among children attending child care centers (CCCs) and determined the infecting astrovirus antigenic types by reverse transcriptase-polymerase chain reaction (RT-PCR) and sequence analysis. Eight astrovirus outbreaks occurred in 6 CCCs. Of 179 children with diarrhea, 36 (20%) had astrovirus-associated diarrhea. Diarrhea stools obtained during diarrhea outbreaks were more likely to contain astrovirus (40/476) than were samples not associated with a diarrhea outbreak (14/452) (P<.001). Type-specific RT-PCR and DNA sequencing identified 5 outbreaks associated with HAstV-1 and 3 outbreaks with HAstV-2. Sequential outbreaks in 2 CCCs occurred with a different type in the same year. Phylogenetic analysis identified 6 clades of HAstV-1 and 2 clades of HAstV-2 during this 1-year surveillance. Astrovirus was a significant cause of diarrhea outbreaks, and 2 antigenic types were present in the community during 1 diarrhea season.

Animals↗

PubMed1999

Prevalence of antibodies to astrovirus types 1 and 3 in children and adolescents in Norfolk, Virginia.

OBJECTIVE: To determine the prevalence of antibody to human astrovirus types 1 (HAstV-1) and 3 (HAstV-3) in children. METHODS: Sera from children hospitalized in Norfolk, VA, for noninfectious conditions were collected for a 1-month period every 6 months from 1993 to 1996 and tested by enzyme immunoassay for antibody to HAstV-1 and HAstV-3 with the use of baculovirus-expressed recombinant capsid proteins as antigens. RESULTS: The seroprevalence of 393 infants and children to HAstV-1 decreased from 67% in infants <3 months of age to 7% by 6 to 8 months of age, consistent with loss of transplacental antibodies. Children acquired HAstV-1 antibody with a peak prevalence of 94% at 6 to 9 years of age (P < 0.001). Antibodies to HAstV-3 exhibited a lower prevalence, with 26% positive at <3 months, 0% at 6 to 11 months and 42% by 6 to 9 years of age. HAstV-1 seroprevalence in children O to 2 months of age decreased from 89% in November, 1993, to 40% in November, 1996 (P = 0.009). CONCLUSIONS: Astrovirus type-specific antibody prevalence can be measured by baculovirus-expressed capsid antigens in an enzyme immunoassay. Children developed antibody to HAstV-1 (94%) and to HAstV-3 (42%) by 6 to 9 years of age indicating frequent exposure to these enteric viruses in infancy and early childhood.

Adolescent↗

PubMed1998

Role of human-milk lactadherin in protection against symptomatic rotavirus infection.

BACKGROUND: Human milk contains a 46 kDa mucin-associated glycoprotein, lactadherin, which binds specifically to rotavirus and inhibits its replication. This study tested the hypothesis that lactadherin protects against symptoms of rotavirus infection. METHODS: 200 infants in Mexico City were recruited at birth and monitored by regular stool EIA for rotavirus, serology, and recording of feeding and stool patterns. Milk samples were obtained from the mothers weekly until 4 weeks post partum then monthly. The sample taken immediately before an infant's episode of rotavirus infection was assayed for lactadherin, butyrophilin, mucin, and secretory IgA. An infection was defined as symptomatic if diarrhoea occurred in the 5 days before or after detection of the virus. FINDINGS: 31 infants developed rotavirus infection; 15 were symptomatic and 16 had no symptoms. The median concentration of lactadherin in the milk samples (obtained 4-41 days [median 13] before the infection) was 48.4 (range 5.6-180) microg/mL in the asymptomatic group and 29-2 (6.2-103-4) microg/mL in the symptomatic group. Although these medians did not differ significantly, in logistic regression analysis adjusted for age at infection and secretory IgA concentration there was a significant difference between the groups (p=0O01). No association between symptom status and concentrations of butyrophilin, mucin, or secretory IgA was found. INTERPRETATION: Protection against rotavirus by human milk is associated with the glycoprotein lactadherin. This association is independent of products of the secretory immune system.

Adult↗

PubMed1998

Pathogen transmission in child care settings studied by using a cauliflower virus DNA as a surrogate marker.

Two regions of cauliflower mosaic virus DNA were designed as markers to study pathogen transmission in a child care home (CCH) and child care center (CCC) and in homes of CCC children. The DNA markers were stable for 1 month in the environment. The DNA markers were introduced into the environment through sensitized objects, and spread in the environment was traced by detection of the markers with polymerase chain reaction. The DNA markers spread rapidly in both the CCH and CCC after introduction and spread more rapidly in the toddler room than in the infant room of the CCC. Hand touching of contaminated areas was the major factor leading to spread of the markers. Hand washing and surface wiping decreased spread of the markers. The markers spread minimally from room to room in the CCC but were detected in the children's homes after introduction of markers in the CCC.

Adult↗

PubMed1998

A prospective study of astrovirus diarrhea of infancy in Mexico City.

AIM: To describe the epidemiologic and clinical characteristics of astrovirus-associated diarrhea in a cohort of young children from a periurban community in Mexico City. METHODS: From November, 1988, through December, 1991, a total of 214 children were enrolled in a longitudinal study of diarrhea and monitored from birth to 18 months of age. A stool specimen was collected during each episode of diarrhea. Specimens from a total of 510 diarrhea episodes were tested for astrovirus by enzyme immunoassay and examined for other enteric pathogens. The antigenic types of astrovirus were determined by a typing enzyme immunoassay. RESULTS: Astrovirus was detected in 26 (5%) of 510 diarrhea episodes, with an incidence rate of 0.1 episode/child year; the highest rate was in children 13 to 18 months of age. Astrovirus-associated diarrhea was characterized by a median of 4 stools (range, 2 to 10) during the first 24 h, a median duration of 3 days (range, 1 to 21), vomiting (20%), and fever (7%). No cases of dehydration or repeat symptomatic infections were observed. Coinfection with another pathogen was detected in 11 of the 26 episodes (42%). Serotype 2 (35%) was most common, followed by serotypes 4 (15%), 3 (11%), and 1 and 5 (4% each); 31% were nontypable. Astrovirus-associated diarrhea was less severe, as measured by the number of stools (4.3 +/- 1.9), than diarrhea caused by rotavirus (7.1 +/- 2.8) or when coinfections occurred (5.5 +/- 1.6; P = 0.008). CONCLUSIONS: Astrovirus was associated with 5% of the episodes of diarrhea in this cohort of young Mexican children and presented as a mild secretory diarrhea. Five predominant antigenic types were detected with type 2 being the most common.

Astroviridae Infections↗

PubMed1998

Modulation of the immune system by human milk and infant formula containing nucleotides.

OBJECTIVE: To determine whether human milk and nucleotides added to infant formula at levels present in human milk enhance development of the immune system during infancy. METHODS: A 12-month, controlled, randomized and blinded, multisite feeding trial was conducted on two infant formulas: iron-fortified, milk-based control formula (Control) or the same formula fortified with nucleotides (Nucleotide). The level (72 mg/L) and ratio of individual nucleotides selected were patterned after those available in human milk. A third group fed human milk exclusively for 2 months and then human milk or Similac with iron until 12 months of age also was studied. Response to immunizations was chosen to assess development of the immune system. Infants followed the immunization schedule recommended by the American Academy of Pediatrics in 1991. OUTCOME VARIABLES: Antibody responses were determined at 6, 7, and 12 months of age to Haemophilus influenzae type b polysaccharide (Hib), to diphtheria and tetanus toxoids, and to oral polio virus (OPV) immunizations. RESULTS: Of 370 full-term, healthy infants enrolled, 311 completed the study (107 Control, 101 Nucleotide, 103 human milk/Similac with iron). Intake, tolerance, and growth of infants were similar in all three groups. Compared with the Control group 1 month after the third immunization (7 months of age), the Nucleotide group had a significantly higher Hib antibody concentration (geometric mean concentrations of 7.24 vs 4.05 micrograms/mL, respectively), and a significantly higher diphtheria antibody concentration (geometric mean of 1.77 vs 1.38 U/mL). The significantly higher Hib antibody response in the Nucleotide group persisted at 12 months. The antibody responses to tetanus and OPV were not enhanced by nucleotide fortification. There also was an effect of breastfeeding on immune response. Infants who breastfed had significantly higher neutralizing antibody titers to polio virus than either formula-fed group (1:346 vs 1:169 and 1:192 in the Control and Nucleotide groups, respectively) at 6 months of age. CONCLUSION: Infant formula fortified with nucleotides enhanced H influenzae type b and diphtheria humoral antibody responses. Feeding human milk enhanced antibody responses to OPV. Dietary factors play a role in the antibody response of infants to immunization.

Bottle Feeding↗

PubMed1997

Milk oligosaccharide profiles by reversed-phase HPLC of their perbenzoylated derivatives.

Human milk is rich in oligosaccharides, some of which inhibit toxins and pathogens involved in diseases of infants. To investigate qualitative and quantitative individual variation of human milk oligosaccharides, a sensitive method for routine identification and quantification of intact milk oligosaccharides was developed and applied to milk samples from 50 donors. The isolated, reduced neutral oligosaccharide fractions were perbenzoylated, resolved by reversed-phase HPLC, and detected at 229 nm. This method resolves most structural isomers and does not require stringent removal of lactose. Peaks were detected at the low nanogram (pmol) level and peak areas were linear from 1 to 1000 micrograms for a standard oligosaccharide. Oligosaccharide samples equivalent to 1 microliter of human milk give optimum chromatographic separation and resolution. The method gives quantitative results comparable to those obtained with classic total sugar analyses, and has an average coefficient of variation of 13%. The 12 major peaks in human milk coeluted with authentic oligosaccharide standards ranging from tri- to octasaccharides, and their identities were confirmed by mass spectrometry. Significant individual variation exists in oligosaccharide profiles; almost 70% of samples contained 2'-fucosyllactose and lacto-N-fucopentaose I as the major oligosaccharides; for the remainder, the major oligosaccharides were 3-fucosytlactose and lacto-N-fucopentaose-II or lacto-N-fucopentaose-III. This method can be used to investigate the extent and biological significance of oligosaccharide variation in human milk.

Benzoates↗

PubMed1997

Sapporo-like human caliciviruses are genetically and antigenically diverse.

The Sapporo-like human caliciviruses (HuCVs) comprise one of three genogroups of HuCVs associated with acute gastroenteritis. Phylogenetic analysis has shown that Sapporo-like HuCVs are related more closely to animal caliciviruses than to other known HuCVs. We produced 3.2 kb cDNA fragments from the 3' end to three Sapporo-like HuCVs that were associated with acute gastroenteritis in children (Houston/86, Houston/90, and London/92). Sequence analysis of the 3.2 kb cDNAs showed that two of the three viruses had a genomic organization similar to that of other Sapporo-like strains and the third strain (London/92) lacked an open reading frame overlapping the 5' end of the capsid gene. Alignment of the capsid sequences of these three strains showed 44-78% amino acid identity among the three strains. Phylogenetic analysis of the aligned sequences indicated the three strains are related but each belongs to a distinct genetic cluster. The genetic differences are associated with antigenic differences in that an enzyme immune assay (EIA) specific for the prototype Sapporo/82 strain detected the Houston/86 strain, but not the Houston/90 and London/92 strains. In vitro transcription and translation of viral cDNA containing the predicted capsid gene of Houston/90 resulted in a protein of 63 K, which is immunoprecipitated by sera from children infected with the strain. Genetically and antigenically distinct strains in the Sapporo-like HuCVs have not been described previously and the occurrence of such diverse strains in the same community likely increases the importance of these strains as a cause of illness in children.

Amino Acid Sequence↗

PubMed1997

Immunization of seronegative infants with hepatitis A vaccine (HAVRIX; SKB): a comparative study of two dosing schedules.

Hepatitis A virus (HAV) infection is of public health significance among infants and diapered children. Although two licensed HAV vaccines are available, they have not been assessed widely in children under the age of 2 years and are not currently licensed for this age group. The purpose of this study was to evaluate the immunogenicity and reactogenicity of HAV vaccine in seronegative infants. Fifty-three healthy infants were immunized with 360 ELISA Units (EL.U.) of an inactivated HAV vaccine at 2, 4, and 6 (Group 1) or 2, 4, and 15 months of age (Group 2). These injections were not received on the same day that participants received their routine childhood immunizations. HAV serum antibodies were detected using a modified radioimmunoassay procedure and concentrations were calculated using a World Health Organization serum anti-HAV reference standard. No serious-systemic or local reactions were noted among the immunized infants. Three months following the third immunization, seroconversion rates were 100% and 93% in groups 1 and 2, respectively. No significant differences were observed in the geometric mean anti-HAV concentrations between the two groups at comparable time points, i.e. 2 months after the second dose, 3 months after the third dose, and 19 months after the first dose. Three infants, not included in the data presented above, had preexisting maternal antibodies; one never responded to the vaccine and the other two did not respond until maternal antibody levels had become reduced. The results indicate that the inactivated HAV vaccine is highly immunogenic in seronegative infants and could be included in the routine harmonized infant immunization schedule.

Hepatitis A Antibodies↗

PubMed1997

Infection control challenges in child-care centers.

The child-care environment predisposes young children to infection with a variety of pathogens. Factors contributing to increased incidence of certain infections include age-specific hygiene behaviors, immunologic immaturity of young children, and exposure to pathogens with high infectivity. Respiratory tract and enteric pathogens are responsible for most illnesses, but a number of other agents are also important. Hygienic interventions, especially handwashing, remain important in infection control, but maintenance of appropriate immunization levels plays a crucial role in disease prevention in the child-care setting. Future interventions will center on development of new vaccines to eliminate susceptibility of young children to as many infectious agents as possible and continued evaluation of other preventive measures.

Bacterial Infections↗

PubMed1996

Rotavirus infection in infants as protection against subsequent infections.

BACKGROUND: Rotavirus is the leading cause of severe diarrhea in infants. To provide a base line for assessing the efficacy of rotavirus vaccines, we evaluated the protection that is conferred by natural rotavirus infection. METHODS: We monitored 200 Mexican infants from birth to two years of age by weekly home visits and stool collections. A physician assessed the severity of any episodes of diarrhea and collected additional stool specimens for testing by enzyme immunoassay and typing of strains. Serum collected during the first week of life and every four months thereafter was tested for antirotavirus IgA and IgG. RESULTS: A total of 316 rotavirus infections were detected on the basis of the fecal excretion of virus (56 percent) or a serologic response (77 percent), of which 52 percent were first and 48 percent repeated infections. Children with one, two, or three previous infections had progressively lower risks of both subsequent rotavirus infection (adjusted relative risk, 0.62, 0.40, and 0.34, respectively) and diarrhea (adjusted relative risk, 0.23, 0.17, and 0.08) than children who had no previous infections. No child had moderate-to-severe diarrhea after two infections, whether symptomatic or asymptomatic. Subsequent infections were significantly less severe than first infections (P=0.024), and second infections were more likely to be caused by another G type (P=0.054). CONCLUSION: In infants, natural rotavirus infection confers protection against subsequent infection. This protection increases with each new infection and reduces the severity of the diarrhea.

Antibodies, Bacterial↗

PubMed1996

Outbreaks of gastroenteritis in elderly nursing homes and retirement facilities associated with human caliciviruses.

Eleven outbreaks of acute gastroenteritis, eight of which were in nursing homes or retirement facilities, were reported in virginia during the winter of 1993-1994. Serum samples (four outbreaks) and stool samples (two outbreaks) from involved people were tested for human calicivirus (HuCV) infection by enzyme immune assays (EIAs) using recombinant Norwalk virus (rNV) and Mexico virus (rMX) capsid antigens and reverse transcription-polymerase chain reaction (RT-PCR). Of the 31 pairs of acute and convalescent serum specimens tested, 24 had a fourfold or more titer increase to rMX and 4 responded to rNV. In all four outbreaks, the geometric mean titers (GMTs) against rMX were significantly higher than those against rNV in the convalescent, but not in the acute phase of illness. The antibody response to rMX among these patients was also higher than to rNV (summary mean 32-fold increase vs. 0.7-fold increase, respectively, P < .001). Antigen was detected in 5 of 21 stool specimens tested by the rMX EIA, RNA in 12 of 17 stool specimens tested by RT-PCR, and small round structured virus (SRSV) particles in 12 of 21 by electron microscopy (EM); none were positive by the rNV EIA. Sequence analysis of the RT-PCR-amplified products from the viral RNA polymerase region revealed 92-93% amino acid identity with Snow Mountain agent (SMA), 86% with MX, 58-59% with NV, and 31-32% with Sapporo HuCV, suggesting that these viruses belong to the SMA HuCV genogroup.

Aged↗

PubMed1996

The changing epidemiology of astrovirus-associated gastroenteritis: a review.

Our understanding of the epidemiology of astrovirus-associated gastroenteritis has changed markedly with each improvement in detection method. In early surveys based on electronmicroscopy (EM), astroviruses appeared to be a rare cause of gastroenteritis, being found in fewer than 1% of children with diarrhea, usually in small outbreaks of disease and primarily during the winter season. The development and use of monoclonal antibodies and enzyme immunoassays (EIA) to detect astroviruses led to reports of a higher prevalence (2.5%-9%) of astrovirus infection among patients hospitalized with diarrhea. Astroviruses appeared second only to rotaviruses as a cause of hospitalization for childhood viral gastroenteritis. Studies based on EIA detection of astroviruses indicate that astroviruses are common causes of diarrhea in children worldwide, and that most children are infected during their first two years of life. The elderly and the immunocompromised represent high-risk groups as well. The observations that newborns monitored prospectively rarely have repeat disease and that the rate of detection decreases with increasing age suggest that immunity to astroviruses, as immunity to rotaviruses, may develop early in life. The cloning and sequencing of astroviruses have led to more sensitive assays to detect the viruses by reverse transcription, polymerase chain reaction (RT-PCR). Application of RT-PCR for detection of astroviruses in children in day-care centers showed a marked increase in the detected prevalence of astrovirus-associated diarrhea, the rate of asymptomatic infection, and the duration of shedding of virus among those infected, when compared with studies that used other methods. As with rotaviruses, neither the mode of transmission nor the reservoir of astrovirus infection has been identified. Both immune and molecular-based assays to detect astrovirus serotypes indicate that serotype 1 is most common worldwide, although the predominant serotypes may vary by region and time. In the absence of obvious strategies to prevent astrovirus-associated diarrhea, vaccines might be considered if further studies establish that the disease burden would render such a vaccine cost-effective.

Animals↗

PubMed1996

Child-care practices: effects of social change on the epidemiology of infectious diseases and antibiotic resistance.

The increasing number of mothers of young children in the work force and the resultant escalated use of child-care facilities has had a marked effect on the epidemiology of infectious diseases in young children. Children attending child care are at high risk for respiratory and gastrointestinal tract illnesses. The high prevalence of infectious diseases in the child-care setting is accompanied by high usage of antibiotics, which in turn has resulted in spread of antibiotic-resistant organisms. The infectious disease standards of the American Public Health Association/American Academy of Pediatrics guidelines were developed to prevent and limit transmission of infectious diseases in the child-care setting. Adherence to these standards is essential but will not completely eliminate the increased risk of infectious diseases in child-care settings. New challenges need to be addressed to assure that optimal health promotion and disease prevention is practiced in child-care settings. We approach the 21st century with a vast amount of medical knowledge, molecular technology, highly effective vaccines, and powerful antimicrobial agents. However, at the same time we face many unsolved serious problems, such as preventing or controlling the emergence and spread of antibiotic-resistant organisms that adversely affect our ability to treat infectious diseases. Further research is needed concerning the relations between child care, the use of antibiotics, and transmission of antibiotic-resistant organisms in order to design and implement the most effective strategies for preventing or controlling antibiotic resistance. The potential risk for transmission of HIV in the child-care setting also needs to be recognized, and procedures to prevent transmission of blood-borne pathogens need to be followed. Monitoring compliance with national standards for child-care facilities, dissemination of information concerning infectious diseases and use of antibiotics, and development and use of new vaccines are strategies which should be used to help protect the health of children in child-care environments.

Anti-Bacterial Agents↗

PubMed1996

Prospective study of toxigenic Clostridium difficile in children given amoxicillin/clavulanate for otitis media.

OBJECTIVE: Evaluate antibiotic-associated diarrhea and toxigenic Clostridium difficile in stool specimens obtained from children before and after 10 days of amoxicillin/clavulanate for otitis media. DESIGN: Children, 12 to 47 months of age, treated with amoxicillin/clavulanate for otitis media in an outpatient setting were enrolled. Stool specimens were obtained at enrollment, when diarrhea occurred and at the end of therapy. All stool specimens were tested for C. difficile toxins A and B by enzyme immunoassay. RESULTS: Seventy-six children who had stool specimens collected at enrollment and after therapy were included in the analysis. None had C. difficile toxin in stool specimens at enrollment. Six (27%) of 22 children with diarrhea, and 4 (7%) of 54 children without diarrhea had C. difficile toxin present at completion of therapy (P = 0.03). CONCLUSION: Toxigenic C. difficile was identified in 13% of children at the conclusion of amoxicillin/clavulanate therapy with a significantly higher frequency in children with diarrhea.

Amoxicillin↗

PubMed1995

Molecular characterization of a human calicivirus with sequence relationships closer to animal caliciviruses than other known human caliciviruses.

cDNA clones were produced from a morphologically typical human calicivirus (HuCV) in stool specimens collected in 1982 during an outbreak of gastroenteritis in Sapporo, Japan. The cDNA clones were generated separately in two laboratories by reverse transcriptase-polymerase chain reaction (RT-PCR) using primers 35 and 36 derived from Norwalk virus. The RT-PCR product from six specimens was of the predicted size, had a continuous protein encoding frame on the positive strand, and contained GLPS and YGDD amino acid motifs at the predicted distance from the primers. RT-PCR amplification with primer 35 and a HuCV/Sapporo-specific primer 36 of four HuCV/Sapporo-positive stool specimens from a 1986 Houston day care center outbreak yielded products with 93% nucleotide and 99% predicted amino acid sequence identity with the HuCV/Sapporo strain from the 1982 outbreak. The HuCV/Sapporo strains are genetically distinct from previously characterized HuCVs and more closely related to known animal CVs than other known HuCVs.

Animals↗

PubMed1995

Study of Norwalk-related viruses in Mexican children.

Two-hundred Mexican children monitored from birth to 2 years of age in a cohort study of diarrhea were tested for Norwalk virus (NV) and Norwalk-related virus infection. Blood was collected quarterly and tested by an enzyme immunoassay (EIA) using the recombinant NV (rNV) particles as antigen. Stool was collected weekly and tested by an EIA using hyperimmune anti-sera from animals immunized with rNV and a reverse transcription-polymerase chain reaction (RT-PCR) with primers in the RNA polymerase region of NV. A high prevalence of serum antibody to NV (85% at age 2 years) was found by the antibody EIA. In 54 stool specimens selected from children who developed a high titer of serum antibody to rNV, none was positive for NV by the antigen EIA, but 6 yielded products by the RT-PCR. One stool specimen (MX virus) yielded a 3.3 kb RT-PCR product from the 3' end of the viral genome. The MX virus cDNA has a genomic organization like other caliciviruses. Sequence comparison showed that MX virus shares 80% nucleic acid and 91% amino acid sequence identity with Snow Mountain agent (SMA), but only 62% and 60% identity, respectively, with NV in the RNA polymerase region, suggesting that MX virus is a SMA-like virus.

Amino Acid Sequence↗

PubMed1995

Effect of maternal rotavirus immunization on milk and serum antibody titers.

This prospective study evaluated human milk and serum antirotavirus antibody concentrations following maternal rotavirus immunization. Postpartum women (33) were randomized into 3 groups and received a single oral dose of rhesus rotavirus monovalent reassortant vaccine (10(4) pfu), tetravalent vaccine (10(4) pfu), or placebo. Milk (secretory [s] IgA) and serum (IgA and IgG) specimens were tested for antirotavirus isotype-specific antibody. Sera also were tested for G1- to G4-specific antibody. Prevaccine milk and serum isotype-specific antibody concentrations were not significantly different in the 3 groups. Postvaccine sIgA log titers were significantly greater in the 2 vaccine groups than the placebo group (P = .002). Mean log10 titers at 1 week were 2.1 (95% confidence interval [CI], 2.0-2.3) in the 2 vaccine groups and 1.7 (95% CI, 1.5-1.9) in the placebo group. Milk titers did not differ between vaccine groups. There was no difference in reactogenicity between groups. The significantly higher milk concentrations of antibody to rotavirus in postpartum women who received rotavirus immunization persisted for 4 months.

Adolescent↗