Paul J. Edelson

Anaerobic bacteremia in a neonatal intensive care unit: an eighteen-year experience.

A review of anaerobic bacteremia in the Neonatal Intensive Care Unit identified 29 episodes of clinically significant bacteremia occurring over the past 18 years. This experience suggested that certain clinical settings were associated with specific anaerobic infections. Although Gram-positive and Gram-negative anaerobes were isolated with similar frequency, 8 of 12 infants bacteremic within the first 48 hours of life were infected with Gram-positive, penicillin G-susceptible organisms whereas 11 of 17 infants older than 2 days were bacteremic with Gram-negative, penicillin G-resistant anaerobes. Eleven of 17 infants with anaerobic bacteremia associated with necrotizing enterocolitis were bacteremic with Gram-negative anaerobes. Five of 6 infants with anaerobic bacteremia associated with chorioamnionitis were bacteremic with Gram-positive anaerobes. These observations should be considered in making decisions regarding empiric therapy for the newborn at highest risk for anaerobic bacteremia.

The Role of C3 in Mediating Binding and Ingestion of Group B Streptococcus Serotype III by Murine Macrophages

ABSTRACT: To understand how complement effects phagocytosis of type III group B streptococcus, we assessed the specific role of C3 in mediating binding and ingestion of these bacteria by macrophages. Phagocytosis of bacteria by resident mouse peritoneal macrophages was measured under conditions in which C3 deposition on bacteria was inhibited or after blockade of C3-ligands or of complement receptor type three (CR3) with specific antibodies. C3 depletion, incubation with F(ab′)2 fragments of antibody to C3, or blockade of CR3 completely inhibited the binding of bacteria that was seen in the presence of nonimmune serum. Immune serum increased the number of associated organisms 6-fold compared to that seen with nonimmune serum. With this serum, 82% of organisms were ingested. C3 depletion or CR3 blockage had a modest effect, but this interaction could be ablated completely only after Fc receptors were blocked. Using varied concentrations of an IgG2a MAb against type III capsular antigen, it was possible to show that small amounts of antibody incapable of mediating bacterial binding by itself directed an interaction that also depended upon C3. Phagocytosis of group B streptococci by macrophages in the presence of little or no antibody requires complement and C3 opsonization specifically. C3-dependent binding may be important in determining mononuclear phagocyte-dependent clearance of these pathogens from blood, particularly in patients with little or no type-specific serum antibody.

Pneumocystis carinii infections in HIV-infected children

Since 1981, 1200 children with acquired immunodeficiency syndrome have been reported to the Centers for Disease Control. Among these children, Pneumocystis carinii has been the leading cause of serious morbidity and mortality. This review discusses the epidemiology, diagnosis, and treatment of P. carinii.

Mechanisms of microbial entry and endocytosis by mononuclear phagocytes.

Phagocytosis is a primary component of the host defense against invading microorganisms. Macrophages, working in concert with cellular and humoral immune mechanisms, are active both in clearing organisms from the blood or tissues and in killing and degrading them once they have been ingested. In this chapter we examine the molecular recognition mechanisms involved in the interaction of microbial pathogens with the macrophages and how these interactions contribute either to eradication of the invaders or to their ultimate ability to survive in the host. To that end, we review the physiology of phagocytosis, the classes of membrane binding sites currently recognized on the macrophage, the alteration of these binding sites upon macrophage activation, and the ways in which these sites may contribute to or oppose microbial infection. We are especially interested in examining the hypothesis that the initial plasma membrane binding mechanisms play important roles in determing the ultimate intracellular fate of phagocytized organisms.

1164 EFFICACY OF RIBAVIRIN FOR TREATING RESPIRATORY SYNCYTIAL VIRUS (RSV) PNEUMONIA IN HIGH-RISK INFANTS

Twenty-two infants under 1 year hospitalized with lower respiratory tract disease due to RSV documented by virus isolation or indirect immunofluorescence were enrolled in a double blind placebo controlled efficacy trial of aerosolized Ribavirin. Nine patients with ten episodes of illness were classified as high-risk because of preexisting cardiac or pulmonary disease. The majority of patients in both groups presented with respiratory distress or apnea. All four patients in the treated group had bronchopulmonary dysplasia (BPD). In the placebo group, three patients had BPD and three had cardiac disease. Drug efficacy was assessed by comparing the mean duration of the following clinical characteristics between groups: tachypnea (RR > 50), days held NPO, days of hypoxemia (pO2 < 70), days requiring supplemental oxygen, and days requiring mechanical ventilation. Although trends in favor of Ribavirin were seen for all measures other than tachypnea, using the Wilcoxon rank-sum test, significant differences were seen for the two latter characteristics (2.2 days vs. 8.0 days, and 0.2 days vs. 4.5 days).

Effect of Pediatric Amino Acid Mixtures Aminosyn-Pf and Trophamine on Bacterial Growth of Staphylococcus Epidermidis 1479

Infection by staphylococcus (s) epidermidis is a common problem in infants who are on total parenteral nutrition for long periods. The purpose of this in- vitro study is to see whether two commonly used pediatric aminoacid mixtures differ in their effect on growth of s. epidermidis.

1075 IgE ANTI-RSV SECRETORY IMMUNE RESPONSE IN INFANTS TREATED WITH RIBAVIRIN AEROSOL

Twenty-two hospitalized infants with documented RSV lower respiratory tract infection were enrolled in a double-blind placebo-controlled drug efficacy study of the antiviral agent, Ribavirin. Fifteen infants were evaluated for production of specific IgE-RSV in nasopharyngeal secretions at time of admission and at regular intervals during convalescence, up to four months beyond initial presentation. Seven infants were treated with aerosolized Ribavirin for a mean duration of 3.14 days. They ranged in age from 1 mo-12 mos. (median 3 mos) with a male:female ratio of 3:4. Eight infants, during 9 episodes of illness received placebo for mean duration of 5.88 days. They ranged in age from 1-24 mos. (median 3.5 mos) with male:female ratio of 6:2. Atopic family history was positive in 6 of 7 patients treated with drug(85%) as compared to 3/8 in placebo group(38%). One patient in treated group, two in placebo presented with bronchiolitis. RSV infection was documented by indirect immunofluorescent assay for antigen and/or culture positivity. IgE-RSV titers in secretions were quantitated by an ELISA technique. Criteria for a significant response was IgE-RSV titer of 8 or greater by 4 months after initial infection. In the seven treated patients, only two had a significant rise in IgE titer. In contrast, 7 of 8 untreated patients had a significant titer rise. As calculated with the Fisher Exact test, this significant at a p value of 0.033.

STAPHYLOCOCCUS EPIDERMIDIS BACTEREMIA IN NEONATES: THE OCCURRENCE OF FOCAL INFECTION

The frequency and clinical significance of Staphylococcus epidermidis isolates from blood cultures of neonates collected over a 17 month period in The New York Hospital neonatal intensive care unit (NICU) were reviewed. Twenty-three episodes of clinically significant S. epidermidis bacteremia were identified using the criteria of isolation from 3 of 3 blood culture bottles from a single culture (6 episodes), or isolation from two or more blood cultures taken at different times (9 episodes), or simultaneous isolation from blood and fluid, pus, or vascular catheter (8 episodes). Of these 23 episodes, 10 were associated with colonized vascular catheters and four occurred in infants with necrotizing enterocolitis. Focal S. epidermidis infection occurred in 10 episodes and persistent bacteremia occurred in 7 of these episodes. S. epidermidis was the most frequent cause of bacteremia occurring in 1.2% of the neonates admitted to the NICU during the period reviewed. As assessed by disc method, 74% of the isolates determined to be clinically significant were resistant to methicillin and cephalothin and 91% were resistant to gentamicin. All isolates were sensitive to vancomycin. In addition to removing vascular catheters suspected of being colonized and searching for potential sites of focal infection, an antibiotic regimen which includes vancomycin should be initiated once clinically significant S. epidermidis bacteremia has been recognized.