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Biomedical subjects

C J Baker

Publications and source records attributed to C J Baker.

At least 55 records · Page 3Linked to original sources

Changing epidemiology of group B streptococcal colonization.

OBJECTIVES: To define factors influencing vertical transmission of and neonatal colonization with group B streptococci (GBS) in neonates representing ethnically and economically diverse populations, and to determine the serotype distribution of isolates, especially new types IV-VIII. STUDY DESIGN: Prospective, cross-sectional study of neonates born to women evaluated for GBS colonization at admission for delivery to one of four hospitals between January 1994 and February 1995. Cultures of throat, umbilicus, and rectum were obtained from 24- to 48-hour-old infants for isolation of GBS. Isolates were classified by capsular polysaccharide (I-VIII) and C protein (alpha and beta) antigen components. RESULTS: Colonization was detected in 28% of 546 mothers, was higher in blacks than whites (40.6% vs 20.3%) and Hispanics (26. 9%), and was not influenced by socioeconomic status. Overall, ethnic origin did not seem to be related to GBS serotype, but whites were more likely to carry the new type V strain than blacks (6 out of 24 [25%] vs 1 out of 43 [2%]). Vertical transmission of GBS to neonates was significantly diminished when their mothers had intrapartum antibiotics (0% vs 52%), rupture of membranes <12 hours before delivery (38.4% vs 73.3%), or delivery by cesarean section (25.9% vs 45.2%). Colonization with GBS was found in 13.8% of 549 neonates, was acquired vertically in 97%, and was less frequent in neonates at the private hospitals (4% vs 20%) where intrapartum antibiotics were given more frequently (34.7% vs 17.3%). Among isolates from neonates, serotype Ia predominated (31.6%) followed by types II (25%), III (22.4%), and V (11.8%); approximately 40% of strains contained C protein antigen. CONCLUSIONS: Changes in the epidemiology of GBS colonization included diminished rates in some populations associated with use of maternal intrapartum antibiotics, and a shift in serotype prevalence, with Ia as predominant and V, in addition to II and III, as common.

Antibiotic Prophylaxis↗

Neurologic, neurocognitive, and brain growth outcomes in human immunodeficiency virus-infected children receiving different nucleoside antiretroviral regimens. Pediatric AIDS Clinical Trials Group 152 Study Team.

OBJECTIVES: To compare the impact of three different nucleoside reverse transcriptase inhibitor regimens, zidovudine (ZDV) monotherapy, didanosine (ddI) monotherapy, and ZDV plus ddI combination therapy, on central nervous system (CNS) outcomes in symptomatic human immunodeficiency virus (HIV)-infected children. METHODS: Serial neurologic examinations, neurocognitive tests, and brain growth assessments (head circumference measurements and head computed tomography or magnetic resonance imaging studies) were performed in 831 infants and children who participated in a randomized double-blind clinical trial of nucleoside reverse transcriptase inhibitors. The Pediatric AIDS Clinical Trials Group study 152 conducted between 1991 and 1995 enrolled antiretroviral therapy-naive children. Subjects were stratified by age (3 to <30 months of age or 30 months to 18 years of age) and randomized in equal proportions to the three treatment groups. RESULTS: Combination ZDV and ddI therapy was superior to either ZDV or ddI monotherapy for most of the CNS outcomes evaluated. Treatment differences were observed within both age strata. ZDV monotherapy showed a modest statistically significant improvement in cognitive performance compared with ddI monotherapy during the initial 24 weeks, but for subsequent protection against CNS deterioration no clear difference was observed between the two monotherapy arms. CONCLUSIONS: Combination therapy with ZDV and ddI was more effective than either of the two monotherapies against CNS manifestations of human immunodeficiency virus disease. The results of this study did not indicate a long-term beneficial effect for ZDV monotherapy compared with ddI monotherapy.

Adolescent↗

Oxygen metabolism in plant/bacteria interactions: effect of DPI on the pseudo-NAD(P)H oxidase activity of peroxidase.

Diphenyleneiodonium (DPI) has been used frequently as a specific inhibitor of NADH oxidase activity in studies of plant/pathogen interactions. The present study reports the effect of DPI on the pseudo-oxidative activity of horseradish peroxidase. DPI, like other phenolics, is able to catalytically stimulate NADH oxidation in the presence of exogenous H2O2. The stimulated NADH oxidation has an acidic pH optimum and has an apparent Km of 111 microM NADH. The NADH oxidation rate is linearly proportional to [DPI] and the amount of NADH oxidized is proportional to [H2O2]. Once exogenous H2O2 is depleted, the NADH oxidation is abruptly halted until additional H2O2 is supplied. In some respects DPI appears to mimic the effects of certain anti-oxidants that use HRP to scavenge H2O2 and NAD(P)H as a reductant.

Bacteria↗

Predictive value of quantitative plasma HIV RNA and CD4+ lymphocyte count in HIV-infected infants and children.

CONTEXT: Pediatric human immunodeficiency virus (HIV) infection has unique viral pathogenetic features that preclude routine extrapolation from adult studies and require specific analysis. OBJECTIVES: To evaluate the prognostic value of 2 key laboratory markers-plasma RNA and CD4+ lymphocyte count-for HIV disease progression in infants and children and to establish targeted values for optimal outcome. DESIGN: Data from a cohort of 566 infants and children who participated in a randomized, placebo-controlled trial of nucleoside reverse transcriptase inhibitors (ACTG 152) were analyzed. The trial was conducted between 1991 and 1995 and enrolled a heterogeneous cohort of antiretroviral therapy-naive children (age, 3 months to 18 years); patients had a median follow-up of 32 months. MAIN OUTCOME MEASURES: The trial clinical end points consisted of time to first HIV disease progression (growth failure, decline in neurologic or neurodevelopmental function, opportunistic infections) or death. RESULTS: Baseline plasma RNA levels were high (age group medians, 5 x 10(4) to >10(6) copies/mL), and both baseline RNA and CD4+ lymphocyte count were independently predictive of subsequent clinical course. Risk reduction for disease progression between 49% and 64% was observed for each log10 reduction in baseline RNA and was linear without suggestion of a threshold or age effect. Disease progression predictive power was enhanced by the combined use of plasma RNA and CD4+ cell count. Marker values of less than 10000 copies/mL for plasma RNA and greater than 500 x 10(6)/L (<6.5 years of age) or greater than 200 x 10(6)/L (>6.5 years) for CD4+ cell count were associated with a 2-year disease progression rate of less than 5%. CONCLUSIONS: Two key laboratory markers--plasma RNA and CD4+ lymphocyte count-are independent predictors of clinical course among HIV-infected infants and children. The linear, age-independent relationship between log10 plasma RNA and relative risk of disease progression strongly supports therapeutic efforts to achieve plasma virus levels as low as possible.

Adolescent↗

Recurrent group B streptococcal disease in infants: Who should receive rifampin?

A preterm breast-fed infant had three episodes of type Ia/c group B streptococcus septicemia. After the second episode rifampin was given to the infant, but further Ia/c exposure to maternal breast milk ensued. We propose rifampin treatment for both the mother and infant in cases of recurrent group B streptococcus disease.

Breast Feeding↗

Variations in HIV risk behaviors of incarcerated juveniles during a four-year period: 1989-1992.

OBJECTIVE: To retrospectively monitor over several years change in incarcerated juveniles' human immunodeficiency virus (HIV) risk behaviors. METHODS: From 1989 to 1992, detainees who volunteered after an HIV class or were referred by a health care provider were counseled individually and privately by health educators using a standardized questionnaire and counseling form developed from an instrument used to counsel prostitutes in Los Angeles, California. RESULTS: The number counseled each year was 1045, 1745, 2354 and 1428 from 1989 to 1992, respectively. Those agreeing to HIV testing rose from 72% of total participants in 1989 to 84% of total participants in 1992. Eight of those youth tested as HIV positive. Four blind seroprevalence studies during the same time yielded one case in 1000 for 1988, one case in 1005 for 1989, two cases in 751 in late 1989 (2.7/1000), and one case in 1214 for 1990 (1.25/1000). The number worrying about AIDS and considering themselves vulnerable to AIDS increased, but protective behaviors did not. Sexual partners per year were 2.1 regardless of the age of first sexual activity. Alcohol was associated with an increased number of sexual partners (2.6/year) and higher rates of sexually transmissible infections (STIs) and pregnancy. Although 96% of boys and girls were sexually active, only 4% used a condom consistently during the first 3 years, and only 7% in 1992. Those reporting having used condoms with the intention to prevent both STIs and pregnancy had a higher rate of use. Those carrying condoms all the time used condoms more often. Males having sex with both males and females rarely used condoms, and 45% had one or more STIs. CONCLUSIONS: Although the rate of HIV infection remains low in juveniles detained by the County of Los Angeles, their rates of risky behaviors place them at high risk for HIV acquisition.

Adolescent↗

Congenital varicella-zoster virus infection and Barrett's esophagus.

Congenital varicella syndrome is a rare complication of varicella-zoster virus (VZV) infection during pregnancy. An infant was exposed to VZV at 18.5 weeks of gestation and had eye and skin abnormalities at birth and persistent feeding difficulties, prompting esophageal biopsies at 12 days and 20 and 20.5 months of age. Esophageal tissues demonstrated specialized intestinal metaplasia (Barrett's esophagus). VZV DNA (in situ hybridization) and proteins (immunohistochemistry and polymerase chain reaction) were found in esophageal epithelial cells adjacent to the Barrett's lesion. Immediate-early 63 protein (IE63) of VZV was demonstrated in the day 12 specimen, and IE62 and the late VZV glycoprotein E (gE) were found in the 20-month specimen. Clinical and endoscopic improvement followed fundoplication and acyclovir therapy, but VZV DNA and IE62 persisted in esophageal tissue. These findings associate VZV with specialized intestinal metaplasia within the esophagus and suggest a novel site for either latent or active VZV infection.

Barrett Esophagus↗

Diagnosis and monitoring of cerebral hyperfusion after carotid endarterectomy with single photon emission computed tomography: case report.

OBJECTIVE AND IMPORTANCE: Focal neurological deficits after carotid endarterectomy may result from ischemia or hyperperfusion. The usefulness of single photon emission computed tomography (SPECT) for differentiating between these two mechanisms has not been previously emphasized. CLINICAL PRESENTATION: An 83-year-old man experienced dysarthria and left-sided weakness immediately after undergoing endarterectomy of the right internal carotid artery. The results of computed tomography of the head were normal, and transcranial Doppler sonography showed symmetrically elevated velocities in both middle cerebral arteries. On the 1st postoperative day, the patient's deficits worsened in parallel with spontaneous increases in blood pressure, and blood pressure reduction with labetalol resulted in clinical improvement. INTERVENTION: On the 2nd postoperative day, technetium-99-hexametazime SPECT demonstrated markedly increased flow in the right basal ganglia and inferior frontal cortex, confirming the diagnosis of cerebral hyperperfusion. The patient's deficits continued to improve with antihypertensive therapy, and SPECT performed 7 and 48 days after surgery showed gradual normalization of the focal hyperemia. CONCLUSION: SPECT can be used to diagnose and monitor cerebral hyperperfusion after carotid endarterectomy and may be of particular value for differentiating hyperperfusion from ischemia when characteristic computed tomographic and transcranial Doppler sonographic findings are absent.

Aged↗

Antimicrobial susceptibilities of group B streptococci isolated between 1992 and 1996 from patients with bacteremia or meningitis.

In vitro testing of 229 group B streptococcal isolates from a variety of patients with invasive infections indicated uniform penicillin G susceptibility. However, 17 (7.4%) isolates were resistant to erythromycin and 8 (3.4%) were resistant to clindamycin. These results support the continued use of penicillin G as the drug of choice for the treatment and prevention of group B streptococcal disease.

Adolescent↗

Seroprevalence of antibodies to group B streptococcal polysaccharides in Gambian mothers and their newborns.

In developing countries, little is known about the relationship between group B streptococcal (GBS) colonization in pregnant women and serum antibody levels to capsular polysaccharide antigens of these organisms. This study examined the prevalence of antibodies to two polysaccharides of GBS, Ia and III, in 124 Gambian women with known GBS colonization at delivery and their newborns. Mean antibody levels in maternal-cord serum pairs were 4.06 +/- 0.25 micrograms/mL and 2.64 +/- 0.20 micrograms/mL for type Ia GBS, and 1.1 +/- 0.52 microgram/mL and 0.78 +/- 0.43 microgram/mL for type III GBS. Women colonized with type V GBS had significantly higher antibody levels to type III GBS than did noncolonized women, but no difference was found when these groups were compared for antibody levels to type Ia GBS. Women > or = 20 years had significantly higher antibody levels to type III GBS compared with younger women and those colonized by other GBS serotypes. Maternal antibodies to types la and III GBS were transferred across the placenta to newborns. The rarity of GBS disease in Gambia and other developing countries may be due to the prevalence of maternally derived GBS antibodies, the low prevalence of colonization with serotype III strains, or other undefined factors.

Adult↗

Epidemiological analysis defining concurrent outbreaks of Serratia marcescens and methicillin-resistant Staphylococcus aureus in a neonatal intensive-care unit.

OBJECTIVE: To describe the epidemiology, interventions, and molecular typing methods used during the investigation and control of concurrent outbreaks of Serratia marcescens and methicillin-resistant Staphylococcus aureus (MRSA) infections in a neonatal intensive-care unit (NICU). SETTING: A 206-bed women's and infants' hospital with a 48-bed NICU. DESIGN: A 22-week, prospective, descriptive study of all NICU infants with S marcescens or MRSA infection or colonization. Repetitive polymerase chain reaction (rep PCR) and pulsed-field gel electrophoresis (PFGE), respectively, were applied to the typing of S marcescens and MRSA isolates. INTERVENTIONS: Infants with S marcescens or MRSA infection or colonization were placed in isolation; all other infants were cohorted. A multidisciplinary task force implemented education for all hospital and medical staff regarding policies essential for outbreak control. Changes in physical setting and patient contact procedure were required to promote adherence to existing policies. RESULTS: Two premature infants had S marcescens infection, and five were colonized; rep PCR verified that both invasive and three of five colonizing isolates were related genotypically. Five bacteremic and 10 MRSA-colonized infants were identified; PFGE confirmed that 12 of the isolates had similar electrophoretic patterns. S marcescens infection was eliminated from the NICU 3 weeks after interventions were initiated. MRSA infections also were eliminated, and MRSA colonization fell to below pre-outbreak rates within 8 weeks. Despite a 100% increase in NICU patient days per month during the subsequent 2 years, no further clusters of S marcescens or MRSA infection have occurred. CONCLUSIONS: Concurrent outbreaks of S marcescens and MRSA in an NICU were confirmed by genotyping of strains. Control was achieved by isolation and cohorting of patients and strict adherence to NICU policies and procedures.

Disease Outbreaks↗

Zidovudine, didanosine, or both as the initial treatment for symptomatic HIV-infected children. AIDS Clinical Trials Group (ACTG) Study 152 Team.

BACKGROUND: Zidovudine has been the drug of choice for the initial treatment of symptomatic children infected with the human immunodeficiency virus (HIV). This trial was designed to assess the efficacy and safety of treatment with zidovudine alone as compared with either didanosine alone or combination therapy with zidovudine plus didanosine. METHODS: In this multicenter, double-blind study, symptomatic HIV-infected children 3 months through 18 years of age were stratified according to age (<30 months or > or =30 months) and randomly assigned to receive zidovudine, didanosine, or zidovudine plus didanosine. The primary end point was length of time to death or to progression of HIV disease. RESULTS: Of the 831 children who could be evaluated, 92 percent had never received antiretroviral therapy and 90 percent had acquired HIV perinatally. An interim analysis (median follow-up, 23 months) showed a significantly higher risk of HIV-disease progression or death in patients receiving zidovudine alone than in those receiving combination therapy (relative risk, 0.61; 95 percent confidence interval, 0.42 to 0.88; P=0.007). The study arm with zidovudine alone was stopped and unblinded; the other two treatment arms were continued. At the end of the study, didanosine alone had an efficacy similar to that of zidovudine plus didanosine (median follow-up, 32 months) (relative risk of disease progression or death, 0.98; 95 percent confidence interval, 0.70 to 1.37; P=0.91). A significantly lower risk of anemia or neutropenia was seen in patients receiving didanosine alone (P=0.036). CONCLUSIONS: In symptomatic HIV-infected children, treatment with either didanosine alone or zidovudine plus didanosine was more effective than treatment with zidovudine alone. The efficacy of didanosine alone was similar to that of the combination therapy and was associated with less hematologic toxicity.

Adolescent↗

An N-terminally truncated third progesterone receptor protein, PR(C), forms heterodimers with PR(B) but interferes in PR(B)-DNA binding.

Multiple progesterone receptor (PR) isoforms may explain in part the complex and diverse biological actions of progestins. Recent studies demonstrate that the human 116 kDa B-receptor (PR[B]) and the 94 kDa A-receptor (PR[A]) can have very different transcriptional functions that are cell- and promoter-specific. Additionally, we have shown the existence of a smaller N-terminally truncated 60 kDa progestin-specific binding protein, called the C-receptor (PR[C]), that has unique transcriptional potentiating properties. In the presence of the other two PR isoforms, PR(C) enhances the transcriptional activities of the larger PR proteins. In order to determine the mechanism of action for the transcriptional promoting abilities of PR(C), the structural and functional properties of PR(C) were analysed and compared to those of PR(A) and PR(B). PR(C) consistently displayed a dissociation constant (Kd) approximately 5 times higher than that for PR(B) and PR(A), suggesting that the N-terminal truncation of PR(C) results in a conformation different from the two larger PR isoforms, that affects the hormone-binding region and its interaction with hormone. Despite this change, PR(C) is still capable of forming heterodimers with the larger PR(B) in solution, as determined by co-immunoprecipitation studies, but PR(C) interferes in tight PR(B) binding to DNA in gel-shift assays. Surprisingly, progestin and antiprogestin autoregulation of PR(C) protein levels parallel those for PR(B) and PR(A).

Binding, Competitive↗

Contribution of antibody to neutrophil-mediated killing of Enterococcus faecalis.

Late-onset septicemia due to Enterococcus faecalis is common among very low-birth weight neonates. These infants have low concentrations of placentally derived IgG and developmentally low levels of complement. The aim of the present study was to determine the contribution of antibody to in vitro neutrophil-mediated phagocytosis of E. faecalis. Antibody alone, as contained in an adult serum pool heated to inactivate complement, promoted only a modest reduction in the initial bacterial inoculum (50 +/- 12%) for 6 of 10 E. faecalis bacterial strains tested and allowed growth of the other four strains. In the presence of complement, NHS promoted > or = 90% reduction in the initial bacterial inoculum of two representative strains at serum concentrations as low as 0.5%. Hypogammaglobulinemic serum supported similar activity only at concentrations above 5%. Purification of IgG and IgM fractions from NHS revealed that IgM had the higher specific activity to promote phagocytic activity. Absorption to remove specific antibody significantly reduced bactericidal activity by normal human serum, complement-deficient sera, and hypogammaglobulinemic serum. Reconstitution of hypogammaglobulinemic serum with antibody as contained in 1% heated normal human serum or in immune globulin for intravenous use (1200 mg/dl) restored phagocytic activity. Thus, E. faecalis-specific antibody enhances PMN-mediated killing of this organism. Adjunctive therapy with intravenous immunoglobulin could augment the host response to enterococcal infections in infancy.

Adult↗