Sustained reductions in neonatal nosocomial infection rates following a comprehensive infection control intervention.

OBJECTIVE: Nosocomial infections (NI) are a frequent and important cause of morbidity and mortality in newborn infants who receive intensive care. We sought to determine if comprehensive infection control (CIC) measures decrease rates in a large neonatal intensive care nursery. METHODS: Single center interventional study. The CIC intervention consisted of increasing nursing and physician education and awareness of infection rates, establishing common improvement goals, training in hand and environment care, and implementing a specialty nursing team for central venous and arterial catheter care. Demographic and microbiology information for all infants admitted to the NICU from January 1, 1999 to December 31, 2000 established baseline data. The intervention period was during January and February 2001. The postintervention period was March 1, 2001 to February 29, 2004. The main outcome measure was the rate of blood, cerebrospinal and/or urinary tract bacterial infections per 1000 hospital days. RESULTS: Baseline infection rate was 8.5 per 1000 hospital days. The NI rate fell 26% (P=0.002) from baseline in the first year and 29% (P<0.001) in the second and third years after the CIC intervention. The reduction in total NI was due mostly to a 46% fall in coagulase-negative Staphylococcus infection rate (P<0.001); however, rates of all other organisms also fell by 21% (P=0.05). CONCLUSIONS: CIC measures can reduce bacterial and fungal NI rates. This effect has been sustained for 3 years following the intervention.

A blinded, randomized, multicenter study of an intravenous Staphylococcus aureus immune globulin.

OBJECTIVES: Very low birth weight (VLBW) infants are vulnerable to nosocomial infections and subsequent morbidity; including infections caused by Staphylococcus aureus: 85% of nosocomial S. aureus infections are caused by capsular polysaccharide (CPS) types 5 and 8. Altastaph is a polyclonal investigational human immunoglobulin G (IgG) with high levels of opsonizing S. aureus CPS types 5 and 8 IgG. METHODS: A Phase 2 clinical trial to assess the safety and kinetics of Altastaph in VLBW infants. Neonates in this multicenter study were randomized to receive two identical 20 ml/kg i.v. infusions of either 0.45% NaCl placebo or 1000 mg Altastaph/kg. Each infant was followed for 28 days after the second infusion or until discharge. Serum S. aureus CPS types 5 and 8 IgG levels were measured preinfusion and at various times after each infusion. RESULTS: Of 206 neonates, 158 received both infusions. Adverse events were similar in the two treatment groups. Six subjects (3% in each group) discontinued owing to an adverse event. Geometric mean anti-type 5 IgG levels were 402 and 642 mcg/ml 1 day following infusion of the first (day 0) and Second (day 14) doses, respectively, in neonates < or =1000 g and slightly higher in neonates 1001 to 1500 g. Trough levels before second infusion were 188 mcg/ml. Type 8 IgG levels were similar. Geometric mean IgG levels among placebo recipients were consistently <2 and <5 mcg/ml for types 5 and 8 in both weight groups. Three episodes of S. aureus bacteremia occurred in each arm. CONCLUSIONS: Infusion of Altastaph in VLBW neonates resulted in high levels of specific S. aureus types 5 and 8 CPS IgG. The administration of this anti-staphylococcal hyperimmune globulin was well tolerated in this population.

Interstitial duplication of 7(q22-->q34).

We report on a 3-year-old boy with an interstitial duplication of 7(q22-->q34), confirmed with fluorescent in-situ hybridization. He had post-natal growth retardation, developmental delay, frontal and parietal bossing, deep-set eyes, strabismus, bilateral optic nerve hypoplasia, and mild dilatation of the cerebral ventricles. His phenotype was not significantly different from that of the three previously reported patients with interstitial duplication of the smaller segment 7(q22-->q31).

Neonatal immunology.

The neonate, whether premature or of normal gestational age, is a unique host from an immunologic perspective. Many components of the immune system function less well in neonates compared with adults, giving rise to the concept of an "immunodeficiency of immaturity." The adaptive significance of these alterations for neonatal survival remains obscure. This review highlights some of the most prominent quantitative and qualitative differences between neonatal and adult immune systems. From a clinical standpoint, the most important differences appear to be (1) reduction in the available bone marrow reserve of granulocyte precursors, (2) reduction in serum complement activity, (3) decreased ability to produce antibodies against bacterial polysaccharide antigens, and (4) increased percentage of T lymphocytes bearing an antigenically "naive" cell surface phenotype and a correspondingly naive functional program.

Multiple-locus variable-number tandem-repeat analysis of meticillin-resistant Staphylococcus aureus discriminates within USA pulsed-field gel electrophoresis types.

Many isolates of meticillin-resistant Staphylococcus aureus (MRSA) are indistinguishable when compared using the standard pulsed-field gel electrophoresis (PFGE) typing method. This may present a problem when investigating local outbreaks of MRSA transmission in a healthcare setting. It also impedes investigation of the widely disseminated community-acquired MRSA (USA 300-0114) in the inpatient setting, which is displacing other traditional hospital-acquired PFGE types. Combination of methods, including multiple-locus sequence typing (MLST), spa typing and staphylococcal cassette chromosome mec (SCCmec) typing, have been used with, or in place of, PFGE to characterise MRSA for epidemiological purposes. These methods are technically challenging, time-consuming and expensive and are rarely feasible except in large laboratories in tertiary care medical centres. Another method, which is simpler and with faster turnaround time, is multiple-locus variable-number tandem-repeat analysis (MLVA). We investigated the utility of MLVA to distinguish common PFGE types. The results suggest that MLVA can be used to identify unrelated strains with identical PFGE patterns or confirm close genetic composition of linked isolates. MLVA could potentially be used in conjunction with PFGE to validate relationships, but further prospective evaluation of these relationships will be required in order to define the proper role, if any, for use of this method in hospital epidemiology.

Peripheral leukocyte count and leukocyte indexes in healthy newborn term infants.

PURPOSE: This study was designed to determine normal values for the peripheral leukocyte count and leukocyte indexes in healthy term neonates at a specific time after birth. METHODS: We prospectively enrolled 193 healthy term-gestation neonates with no identifiable perinatal risk factors for sepsis. At 4 hours of age a blood sample was collected by warmed heel stick. An automated Coulter complete blood cell count and a 100-cell manual differential leukocyte count were performed on each sample. The differential count was performed by a single hematopathologist unaware of the clinical status of each infant. Perinatal factors were identified by review of the mothers' and infants' hospital records. RESULTS: The mean ratio of immature to total neutrophils was 0.16 (SD 0.10), and the 10% to 90% range was 0.05 to 0.27. The mean leukocyte count was 24.06 x 10(9)/L (24,060/mm3), and the 10% to 90% range was 16.2 to 31.5 x 10(9)/L (16,200 to 31,500/mm3). Neutropenia, < 1.5 x 10(9)/L (1500/mm3) segmented plus band form neutrophils, was not observed. Of all the perinatal factors studied, only the duration of stage 1 labor was found to be associated with significant elevations in the leukocyte and absolute neutrophil counts. CONCLUSIONS: Previously published normal ranges for leukocyte indexes in healthy newborn infants during the early neonatal period are too restrictive; reference standards should be broadened.

Volume of blood required to detect common neonatal pathogens.

OBJECTIVE: To determine the minimum volume of blood and the absolute number of organisms required for detection of bacteremia and fungemia by an automated colorimetric blood culture system (BacT/Alert, Organon Teknika). DESIGN: Common neonatal pathogens, Escherichia coli, Streptococcus agalactiae (group B streptococcus (GBS): one American Type Culture Collection (ATCC) strain and one clinical isolate), Staphylococcus epidermidis, and Candida albicans, were seeded into blood to produce bacteremia or fungemia with low colony counts (1 to 3 colony-forming units (CFU) per milliliter) and ultra-low colony counts (<1 CFU/ml). For each organism, 96 culture bottles were inoculated with either 0.25, 0.5, 1.0, or 4.0 ml of the two seeded blood concentrations. Blood culture bottles were incubated in the BacT/Alert device for 5 days, and time to positivity was noted when applicable. All bottles were subcultured on plated media. DATA ANALYSIS: The Poisson statistic was used to calculate the probability of finding at least one viable CFU per inoculated culture bottle. The fraction of culture bottles with positive findings per group was divided by the probability of one or more organisms present to give the positivity index. RESULTS: Plated subculture identified no growth of organisms not detected by the colorimetric detection system. The false-positive rate for the automated device was less than 1%. The positivity index for the GBS clinical isolate was 1.13, for the GBS ATCC isolate 0.96, for S. epidermidis 0.94, for C. albicans 0.97, and for E. coli 0.95. There was a statistically significant difference with time to positivity and inocula volume (p <0.01), but the difference was not clinically important. CONCLUSIONS: If one or two viable colony-forming units are in the blood inoculated into culture media, the BacT/Alert system will detect growth rapidly. Because there appears to be a sizable subset of neonates who are at risk of sepsis with a colony count less than 4 CFU/ml, then a 0.5 ml inoculum of blood into the culture media is inadequate for sensitive and timely detection of bacteremia. One to two milliliters of blood should increase microorganism recovery in the face of low-colony-count sepsis.

T cell receptor repertoire diversity and clonal expansion in human neonates.

Newborn human infants, particularly those born prematurely, are susceptible to infection with a variety of microorganisms. We questioned whether limitations in the T cell repertoire contribute to the neonatal immunocompromised state. To describe developmental changes of the T cell repertoire, cDNA segments corresponding to third complementarity regions (CDR3) of human umbilical cord blood T cell receptors (TCR) from 24-41-wk gestational age were amplified with TCR family-specific probes. The resulting amplified CDRs were visualized by fingerprinting and single strand conformation polymorphism (SSCP) analysis. At 24-wk gestation there were no limitations in TCRBV family usage, and the degree of CDR3 size heterogeneity was not different from the adult. However, earlier in gestation, CDR3s were shorter for all families and gradually increased in size until term. The extent of oligoclonal expansion observed in cord blood was greater than in adult peripheral blood (p = 0.03). T cell oligoclonal expansion was greatest at 29-33-wk gestation and declined toward term. Expansions were detectable in both CD4+ and CD8+ subpopulations. Our findings indicate that the genetic mechanisms of repertoire diversification appear intact as early as 24 wk of gestation, but repertoire diversity is limited as a result of smaller CDR3 sizes. In addition, there was a developmentally regulated progression of oligoclonally expanded T cells. These differences in the TCRBV repertoire add to the body of evidence demonstrating immaturity of the neonatal immune system. However, the role that these subtle differences are likely to play in the relative immunodeficiency of the neonate remains to be determined.

Differentiation of segmented and band neutrophils during the early newborn period.

This prospective study evaluated the degree of inter-reader variability in the identification of segmented and band neutrophils from blood smears of full-term, healthy neonates. Wide inter-reader differences of band neutrophil identification and the immature to total neutrophil ratio were observed. Because of poor correlation between evaluators of the same blood smear, the clinical utility of the manual differential leukocyte count in the evaluation of neonates is limited.