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D T Crouse

Publications and source records attributed to D T Crouse.

At least 19 recordsLinked to original sources
PubMed2001

Immunomodulation by exogenous surfactant: effect on TNF-alpha secretion and luminol-enhanced chemiluminescence activity by murine macrophages stimulated with group B streptococci.

Group B streptococci (GBS) are important pathogens in neonatal sepsis and pneumonia. GBS stimulate alveolar macrophages to produce inflammatory cytokines and free oxygen radicals, which can damage the lungs. In several studies, use of exogenous surfactant in term babies has improved outcome related to sepsis and respiratory failure. The role(s) of exogenous surfactant in modulating the inflammatory response produced by this microbe was examined. Tumor necrosis factor alpha (TNF-alpha) production and luminol-enhanced chemiluminescence (LCL), a measure of respiratory burst, were investigated. For measuring TNF-alpha release, RAW 264.7 murine macrophages were pre-incubated with bovine surfactant and stimulated with either lipopolysaccharide, live or heat-killed GBS type Ia. LCL was measured after macrophages were pre-incubated with or without surfactant overnight, then stimulated with GBS or phorbol myristate acetate. Lipopolysaccharide and GBS stimulated TNF-alpha secretion from macrophages that was suppressed by exogenous surfactant in a dose-dependent fashion. GBS and phorbol myristate acetate also increased LCL from macrophages, which was significantly suppressed by pre-incubation of macrophages with exogenous surfactant. We conclude that GBS type Ia stimulates TNF-alpha release and LCL from RAW 264.7 cells and that these responses are suppressed by surfactant. Suppression of inflammatory mediators by exogenous surfactant might improve respiratory disease associated with GBS.

Animals↗
PubMed1999

Antibiotic use in pregnancy and drug-resistant infant sepsis.

OBJECTIVE: We sought to evaluate the effect of antepartum and intrapartum antibiotic use on antimicrobial-resistant neonatal sepsis. STUDY DESIGN: We analyzed perinatal outcomes for 8474 pregnancies (8593 live births) delivered at 6 hospitals. Data were collected regarding maternal antibiotic use and perinatal course, neonatal cultures, and outcomes. The diagnosis of confirmed neonatal sepsis required at least one positive blood or cerebrospinal fluid culture. Neonatal cultures were evaluated on the basis of the occurrence and timing of maternal antibiotic exposure. RESULTS: There were 96 neonates with confirmed sepsis (11.2/1000 live births). Sepsis was 19.3-fold more common after preterm birth (57 vs 3. 1/1000; P <.001), with 76% of septic infants being delivered preterm. Forty-five percent of pathogens were ampicillin resistant. Ampicillin resistance increased with preterm birth (50% vs 26%; P =. 04), antepartum antibiotics (57% vs 34%; P =.03), intrapartum antibiotics (55% vs 28%; P <.01), and any prenatal antibiotic exposure (52% vs 22%; P =.01). Infection with an organism resistant to at least one maternal antibiotic was more common with intrapartum antibiotic exposure than with antepartum exposure only (57% vs 17%; P =.01). Regarding early-onset sepsis (n = 55), ampicillin resistance was more common with intrapartum antibiotics (50% vs 16%; P <.01), and resistance to at least one maternally administered antibiotic was more frequent with intrapartum exposure (56.7% vs 0%; P <.01). CONCLUSIONS: Maternal antibiotic treatment is associated with neonatal sepsis by organisms resistant to ampicillin and to maternally administered antibiotics.

Ampicillin Resistance↗
PubMed1998

Exogenous bovine surfactant suppresses tumor necrosis factor-alpha release by murine macrophages stimulated by genital mycoplasmas.

Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine that appears to play a significant role in the development of neonatal chronic lung disease (CLD). Inflammation and CLD are also associated with respiratory tract colonization with genital mycoplasmas. The possible protective roles of surfactant in mitigating the inflammatory response to these microbes were investigated. Murine RAW 264.7 macrophages were preincubated with an exogenous surfactant and exposed overnight to sterile media, lipopolysaccharide (LPS), Mycoplasma hominis, or Ureaplasma urealyticum. Macrophages released TNF-alpha in response to challenge with LPS, U. urealyticum, and M. hominis in a concentration-dependent fashion. Surfactant suppressed LPS and M. hominis induced TNF-alpha production in a dose-dependent manner but suppressed U. urealyticum-mediated TNF-alpha production only at the higher dose tested. Similar effects were seen in hyperoxia (95% O2). Thus, exogenous bovine surfactant significantly inhibits the production of TNF-alpha by murine macrophages stimulated with genital mycoplasmas and bacterial LPS.

Animals↗
PubMed1998

Genital mycoplasmas stimulate tumor necrosis factor-alpha and inducible nitric oxide synthase production from a murine macrophage cell line.

Ureaplasma urealyticum and Mycoplasma hominis, two genital mycoplasmas, are the most common organisms isolated in the perinatal period and both either cause or are associated with poor perinatal outcomes. We speculate that these microbes could increase inflammation by stimulating macrophages to produce tumor necrosis factor-alpha (TNF-alpha) and inducible nitric oxide synthase because of their propensity to interact with the host's immune system. To test this hypothesis, RAW 264.7 cells, a murine macrophage cell line, were coincubated for 16 h with either U. urealyticum or M. hominis, and LPS and sterile broth were used as controls. Lipopolysaccharide (LPS) and both mycoplasmas induced TNF-alpha production, which was concentration-dependent, whereas sterile broth had little effect. TNF-alpha production was not inhibited by the addition of polymyxin B, excluding the possibility of contaminating endotoxin in this effect. Inducible nitric oxide synthase was produced only in the presence of recombinant inteferon-gamma. We conclude that both viable and nonviable U. urealyticum and M. hominis are capable of TNF-alpha induction from murine macrophages and that LPS is not involved in this event. Also, the genital mycoplasmas are capable of stimulating inducible nitric oxide synthase production from murine macrophages. We speculate that the genital mycoplasmas produce perinatal disease by producing proinflammatory mediators by their interaction with inflammatory cells and either induce or act as a catalyst and augment inflammation which in turn leads to a poor pregnancy outcome.

Animals↗
PubMed1994

Serum concentrations of erythromycin after intravenous infusion in preterm neonates treated for Ureaplasma urealyticum infection.

Erythromycin is receiving renewed attention as an alternative for treatment of neonatal infections caused by Ureaplasma urealyticum because of recently proved abilities of this organism to produce systemic disease in this population. Although erythromycin has been used clinically for almost 40 years, very little is known about its activity in the preterm neonate. Fourteen neonates, birth weights < or = 1500 g and < or = 15 days of age, from whom U. urealyticum was isolated from the lower respiratory tract were randomized to receive erythromycin lactobionate either 25 or 40 mg/kg/day in four divided doses at 6-hour intervals scheduled for a total of 10 days. Blood samples collected at multiple time points after initial and steady state doses were assayed for erythromycin by liquid chromatography. Minimal inhibitory concentrations (MICs) of erythromycin for the U. urealyticum isolates were determined. MICs ranged from 0.031 to 2 micrograms/ml; MIC90 = 2 micrograms/ml. Serum erythromycin concentrations met or exceeded most MICs, with peak values of 3.05 to 3.69 and 1.92 to 2.9 micrograms/ml for the 40- and 25-mg/kg/day dosage groups, respectively. Pharmacokinetic parameters were calculated after the initial dose and at steady state for both dosage groups and compared. No adverse effects thought to be related to administration of erythromycin were observed. These preliminary findings showed that erythromycin is well-tolerated, has favorable pharmacokinetic activity in the preterm neonate and should be further investigated for treatment of ureaplasmal infections.

Bacteriological Techniques↗
PubMed1993

Radiographic changes associated with tracheal isolation of Ureaplasma urealyticum from neonates.

Recent studies show an association between the presence of Ureaplasma urealyticum in tracheal aspirates and bronchopulmonary dysplasia. We hypothesized that among infants with birth weights < or = 1,250 g and respiratory disease, those with U. urealyticum in their tracheal aspirates would have radiographic evidence of more-severe pulmonary disease more often than would those without this organism. A total of 292 low-birth-weight infants who had endotracheal aspirate cultured within 7 days of birth were enrolled. The radiographic outcome variables were pneumonia, early severe bronchopulmonary dysplasia (precocious), and chronic lung disease. Microorganisms were isolated from 128 infants (44%); U. urealyticum was isolated from 44 (15%). Pneumonia was significantly more common in infants with than without U. urealyticum (30% vs. 16%, P = .03). U. urealyticum also was associated with precocious bronchopulmonary dysplasia independent of prematurity, race, and sex (odds ratio, 2.2; P < .05). Tracheal isolation of U. urealyticum within 7 days of birth is associated with pneumonia and precocious bronchopulmonary dysplasia.

Bronchopulmonary Dysplasia↗
PubMed1993

Systemic neonatal infection due to Ureaplasma urealyticum.

During the past decade considerable evidence, first based on individual case reports and later on prospective studies, has indicated that Ureaplasma urealyticum may be an important neonatal pathogen. Infections of the bloodstream, respiratory tract, and central nervous system have been documented. Isolation of U. urealyticum from the lower genital tract in a large percentage of healthy women and the likelihood that many may transmit infection to their offspring, either in utero or at delivery, have made it difficult to determine the pathogenic potential of this organism in perinatal infections. Early studies showed that newborn infants colonized superficially by U. urealyticum suffered no adverse effects. However, more recent studies involving primarily preterm neonates have clearly demonstrated the ability of U. urealyticum to produce invasive disease. Future investigation should be directed towards a more in-depth characterization of the basic biology of U. urealyticum, identification of the risk factors predictive of invasive disease among those colonized, and the development of rapid tests to detect its presence and to determine the overall significance and prevalence of this organism in specific neonatal infections.

Bacteremia↗
PubMed1993

Therapeutic considerations for Ureaplasma urealyticum infections in neonates.

Appreciation of Ureaplasma urealyticum as a human pathogen and documentation of antibiotic resistance have heightened interest in susceptibility testing and treatment alternatives. Treatment of neonates poses special problems because of potential drug toxicity, clinical unfamiliarity with the various conditions that may be due to or associated with ureaplasmal infection, and frequent isolation of the organism from mucosal surfaces in the absence of overt illness. Case reports have undeniably demonstrated the ability of U. urealyticum to cause neonatal bacteremia, pneumonia, and meningitis, although the frequency with which such clinically significant infections occur among the greater population of colonized neonates is unknown. The association of U. urealyticum with development of chronic lung disease of prematurity further intensifies the need for knowledge concerning effective antimicrobial treatment. Despite controversy stemming from nonstandardized susceptibility testing, erythromycin is the drug of choice for treating neonatal ureaplasmal infections not involving the central nervous system. The use of erythromycin is supported by its activity in vitro, limited data from clinical experience, and preliminary pharmacokinetic and safety studies.

Bronchopulmonary Dysplasia↗
PubMed1993

Ureaplasma urealyticum intrauterine infection: role in prematurity and disease in newborns.

Ureaplasma urealyticum, a common commensal of the urogenital tract of sexually mature humans, is gaining recognition as an important opportunistic pathogen during pregnancy. While its etiologic significance in many aspects of adverse pregnancy remains controversial, recent evidence indicates that U. urealyticum in the absence of other organisms is a cause of chorioamnionitis. Furthermore, ureaplasmal infection of the chorioamnion is significantly associated with premature spontaneous labor and delivery. In at least some cases, it appears to be causal. Present evidence indicates that U. urealyticum is a cause of septicemia, meningitis, and pneumonia in newborn infants, particularly those born prematurely. There is strong but not definitive evidence that ureaplasmal infection of the lower respiratory tract can lead to development of chronic lung disease in very low-birth-weight infants. Although risk factors for colonization of the lower genitourinary tract have been identified, little information is available concerning risk factors for intrauterine infection and host immune responses to invasive infection. Recent establishment of animal models of respiratory and central nervous system diseases should provide an opportunity to evaluate risk factors, pathogenic mechanisms, and operative immune mechanisms. However, the most critical need is additional information concerning indications for diagnosis and treatment as well as efficacy of treatment.

Bacteremia↗
PubMed1992

Antibiotic susceptibilities and therapeutic options for Ureaplasma urealyticum infections in neonates.

The appreciation of Ureaplasma urealyticum as a human pathogen and documentation of antibiotic resistance have heightened interest in drug susceptibilities and treatment alternatives for patients infected with this organism. Neonates pose special problems when therapy must be considered because of potential toxicities, clinical unfamiliarity or lack of experience. Forty-three isolates of U. urealyticum obtained from the lower respiratory tracts of neonates were tested against chloramphenicol, ciprofloxacin, clindamycin, erythromycin, doxycycline, and gentamicin by a microbroth dilution technique in 10B broth. In vitro resistance was observed in 1 or more strains for each of the drugs tested, except for erythromycin (minimal inhibitory concentration (MIC) range, 0.125 to 4 micrograms/ml, MIC90 = 2 micrograms/ml). MIC90 values for the remaining five antibiotics were: doxycycline, 2 micrograms/ml; chloramphenicol, 8 micrograms/ml; ciprofloxacin, 8 micrograms/ml; clindamycin, 16 micrograms/ml; and gentamicin, 32 micrograms/ml. The effect of pH and/or media components on MICs was evaluated by comparing MICs of American Type Culture Collection reference strain Staphylococcus aureus 29213 obtained in Mueller-Hinton broth (pH 7.2 to 7.4) and 10B broth (pH 6.0). No appreciable effect was detected for ciprofloxacin, chloramphenicol or doxycycline, whereas gentamicin, erythromycin and clindamycin all had MICs elevated by one to several dilutions when tested in 10B broth. In some instances the difference was sufficient to alter the interpretation of the MIC. Clinical experience in treating neonatal ureaplasmal infections is reviewed along with recommendations for obtaining cultures, initiating and monitoring efficacy of therapy.

Anti-Bacterial Agents↗
PubMed1991

Perinatal mycoplasmal infections.

Maternal infections are known to play a major role in perinatal morbidity and mortality. Ureaplasma urealyticum and Mycoplasma hominis are sexually transmissible microorganisms associated with a number of pathologic conditions in the pregnant woman including chorioamnionitis and postpartum fever. They are rapidly gaining recognition as significant causes of perinatal infection, especially in infants born prematurely. This review summarizes current knowledge regarding the epidemiology, pathology, disease spectrum, and clinical manifestations of mycoplasmal and ureaplasmal perinatal infections and presents guidelines for proper diagnosis and treatment.

Amniotic Fluid↗
PubMed1990

Mycoplasmal infections of cerebrospinal fluid in newborn infants from a community hospital population.

Mycoplasma hominis or Ureaplasma urealyticum have previously been isolated from cerebrospinal fluid (CSF) in 13 of 100 newborn infants tested from a high risk university hospital population where the mothers were of predominantly lower income and socioeconomic status and had often received little or no prenatal care. We sought to determine whether such infections occur in neonates born to women cared for mainly through private obstetric practices and who delivered in 4 suburban community hospitals. CSF cultures were done in 318 infants during an 8-month period. M. hominis was isolated from 9 and U. urealyticum from 5 CSF cultures. Four infants infected with U. urealyticum and 3 infected with M. hominis were born at term. One infant infected with U. urealyticum had a birth weight of less than 1000 g. In 5 infants clearance of the infecting organism was documented without specific treatment. Twelve infants had good perinatal outcomes regardless of treatment and 2 died. One death in a 2240-g infant infected with M. hominis was associated with Haemophilus influenzae sepsis and pneumonia. The other death occurred 3 days after birth in a 630-g infant infected with U. urealyticum who had evidence of meningitis and intraventricular hemorrhage. Results of this study suggest that mycoplasmas are common causes of neonatal CSF infections, not only in high risk populations, but also in the general population.

Alabama↗
PubMed1990

Hyperoxia potentiates Ureaplasma urealyticum pneumonia in newborn mice.

The effect of continuous exposure to 80% oxygen on newborn mice with Ureaplasma urealyticum pneumonia was determined. Mice were inoculated intranasally with either U. urealyticum or sterile broth and then housed in either 80% oxygen or room air (21% oxygen). The mice were sacrificed at either 7 or 14 days after inoculation. Significantly more mice in the U. urealyticum group housed in 80% O2 than in the room air-exposed group were culture positive 14 days after inoculation (P = 0.042), but no difference was found at 7 days. The presence of alveolar macrophages, neutrophils, and lymphocytes and alveolar wall thickness were determined. Overall, the group housed in 80% O2 and inoculated with U. urealyticum had severe pulmonary lesions at both time points, while the lesion severity in the room air-exposed group inoculated with U. urealyticum and the group housed in 80% O2 and inoculated with sterile broth was dependent on the time point. Mortality was significantly higher in the group housed in 80% O2 and inoculated with U. urealyticum than it was in all other groups (P less than 0.001). Our results indicate that hyperoxia causes the persistence of U. urealyticum in the lungs of newborn mice, acutely potentiates the inflammatory response, and turns an otherwise self-limited pneumonia into a lethal disease.

Animals↗
PubMed1989

A randomized, controlled trial of very early prophylactic ligation of the ductus arteriosus in babies who weighed 1000 g or less at birth.

We speculated that prophylactic ligation of the ductus arteriosus would reduce mortality and morbidity in very-low-birth-weight infants. To test this hypothesis, we randomly assigned 84 babies who weighed 1000 g or less at birth and required supplemental oxygen either to receive standard treatment (n = 44) or to undergo prophylactic surgical ligation of the ductus arteriosus on the day of birth (n = 40). The ductus was ligated in babies in the control group only if the shunt was hemodynamically important. All the babies were followed for one year. The incidence of necrotizing enterocolitis was reduced in the group that underwent prophylactic ligation (3 of 40 [8 percent]) as compared with the control group (13 of 44 [30 percent]; P = 0.002). The frequency of death, bronchopulmonary dysplasia, retinopathy of prematurity, and intraventricular hemorrhage was similar in both groups. Because early enteral feeding may have increased the incidence of necrotizing enterocolitis, we analyzed separately the babies who were fed early. Among the infants who were fed within 14 days of birth, those who underwent prophylactic ligation had a lower incidence of necrotizing enterocolitis (1 of 11 [9 percent]) than those who did not (13 of 24 [54 percent]; P = 0.001). Within the control group, the infants who were fed within 14 days of birth and whose ductus was ligated for medical reasons within 5 days of birth had a lower incidence of necrotizing enterocolitis (2 of 10 [20 percent]) than those whose ductus was ligated later or not at all (11 of 14 [79 percent]; P = 0.004). We conclude that early surgical closure of the ductus arteriosus reduces the risk of necrotizing enterocolitis in infants of very low birth weight who require supplemental oxygen.

Bronchopulmonary Dysplasia↗
PubMed1989

Ureaplasmal pneumonia and sepsis associated with persistent pulmonary hypertension of the newborn.

Ureaplasma urealyticum was isolated from the lower respiratory tract of three infants with persistent pulmonary hypertension of the newborn. In one, cultures positive for U urealyticum were obtained on multiple occasions from trachea, blood, and pleural fluid prior to the infant's death on postnatal day 6. Autopsy findings confirmed the presence of severe pneumonia and the organism was again recovered from multiple sites. A second infant had no apparent predisposing factors for development of persistent pulmonary hypertension of the newborn but U urealyticum and Staphylococcus epidermidis were recovered from the trachea antemortem and from lung tissue obtained during autopsy on the 12th postnatal day. The third infant had persistent pulmonary hypertension of the newborn and a pulmonary infiltrate within hours after birth with tracheal cultures positive for both U urealyticum and Mycoplasma hominis. Erythromycin was given for ten days, and the infant gradually improved. Prolonged ventilation with supplemental oxygen was necessary, and chronic lung disease developed. This is the first report of neonatal ureaplasmal pneumonia with sepsis and persistent pulmonary hypertension of the newborn as well as the first time a microorganism other than streptococci has been specifically implicated in the pathogenesis of persistent pulmonary hypertension of the newborn. Respiratory infections with U urealyticum or other bacteria should be considered as possible causative or contributory factors in infants with persistent pulmonary hypertension of the newborn.

Female↗