Pathogenesis and management of neonatal sepsis and meningitis

Evaluation and Management of Women and Newborns With a Maternal Diagnosis of Chorioamnionitis: Summary of a Workshop

In January 2015, the Eunice Kennedy Shriver National Institute of Child Health and Human Development invited an expert panel to a workshop to address numerous knowledge gaps and to provide evidence-based guidelines for the diagnosis and management of pregnant women with what had been commonly called chorioamnionitis and the neonates born to these women. The panel noted that the term chorioamnionitis has been used to label a heterogeneous array of conditions characterized by infection and inflammation or both with a consequent great variation in clinical practice for mothers and their newborns. Therefore, the panel proposed to replace the term chorioamnionitis with a more general, descriptive term: "intrauterine inflammation or infection or both," abbreviated as "Triple I." The panel proposed a classification for Triple I and recommended approaches to evaluation and management of pregnant women and their newborns with a diagnosis of Triple I. It is particularly important to recognize that an isolated maternal fever is not synonymous with chorioamnionitis. A research agenda was proposed to further refine the definition and management of this complex group of conditions. This article provides a summary of the workshop presentations and discussions.

Bacterial Sepsis in the Newborn Infant: Developmental Deficiencies in Neutrophils and the Role of Neutrophil Transfusion

Bacterial sepsis is an important cause of morbidity and mortality in newborns. Group B streptococci and Es cherichia coli are the primary causative organisms. New and theoretically more effective antibiotics have not im proved survival. Because the neonate has defects in the immune response, new forms of therapy may be able to improve outcome by correcting or circumventing those deficiencies. The neutrophil has a substantial role in antibacterial defense, yet neonatal neutrophil function is limited by impaired chemotaxis, phagocytosis, and in tracellular killing. The supply of neonatal neutrophils is restricted by a small neutrophil reserve, a delay in mobilization of neutrophils from the bone marrow re serve after bacterial invasion, a small granulocytopoietic progenitor cell reserve, and a limited ability to acceler ate proliferation of progenitor cells during bacterial in fection. Recent studies of neutrophil transfusions in in fected neonates suggest a beneficial effect at least in certain situations. Exchange transfusion with fresh whole blood may be an alternative to transfusion with neutro phils obtained by apheresis. The ultimate role of neutro phil transfusions as an adjunct therapy for neonatal sep sis remains to be determined.

How can the microbiologist help in diagnosing neonatal sepsis?

Neonatal sepsis can be classified into two subtypes depending upon whether the onset of symptoms is before 72 hours of life (early-onset neonatal sepsis—EONS) or later (late-onset neonatal sepsis—LONS). These definitions have contributed greatly to diagnosis and treatment by identifying which microorganisms are likely to be responsible for sepsis during these periods and the expected outcomes of infection. This paper focuses on the tools that microbiologist can offer to diagnose and eventually prevent neonatal sepsis. Here, we discuss the advantages and limitation of the blood culture, the actual gold standard for sepsis diagnosis. In addition, we examine the utility of molecular techniques in the diagnosis and management of neonatal sepsis.

A study of the role of multiple site blood cultures in the evaluation of neonatal sepsis

BACKGROUND

The optimal number of blood cultures needed to document sepsis in an ill neonate has undergone little critical evaluation. Multiple site cultures may improve pathogen detection if intermittent bacteremia occurs, or if a low density of bacteria is present in the blood. We hypothesized, however, that bacterial clearance is slower and bacteremia more continuous in septic neonates, so that a single site blood culture should be sufficient to accurately document true septicemia.

OBJECTIVE

To determine the need for multiple site blood cultures in the evaluation of neonates for sepsis.

DESIGN/METHODS

Clinical data were prospectively collected for 216 neonates who had 269 pairs of blood cultures taken from two different peripheral sites for the evaluation of possible sepsis. A minimum of 1 ml of blood was obtained from the two peripheral sites within 15-30 min of each other. Based on prior retrospective data, we determined that 203 infants would need to have two site blood cultures to demonstrate a significant improvement in pathogen detection at an alpha of 0.05 and a beta of 0.20 (80%) power.

RESULTS

A total of 186 culture pairs were taken for evaluation of early-onset sepsis in 186 neonates, while 83 pairs were drawn for evaluation of late-onset sepsis in 43 neonates. In all, 21 neonates from the late-onset group were evaluated more than once, and 12 neonates were evaluated for both early- and late-onset sepsis. In all, 20 (9.2%) of 216 neonates had 22 episodes of culture-proven sepsis at a median age of 18 days. All neonates with positive cultures had the same organism with a similar sensitivity pattern obtained from the two different peripheral sites. The other 196 study neonates had negative blood cultures from both sites. The single episode of early-onset sepsis was caused by Listeria monocytogenes, while all remaining episodes were late-onset with the following organisms: Staphylococcus epidermidis (7), methicillin-resistant Staphylococcus aureus (MRSA) (3), combined MRSA and Candida albicans (2), Candida albicans alone (2), late-onset Group B beta-hemolytic Streptococcus (GBS) (2), Klebsiella pneumoniae (2), Enterococcus fecalis (1), Escherichia coli (1), and Serratia marcescens (1). Since no infant grew organisms from only one of the two sites, the data indicate that the diagnosis of sepsis would have been made correctly in all infants with a single site culture.

CONCLUSIONS

Two site blood cultures for the initial evaluation of neonatal sepsis do not have a better yield in pathogen detection. Sepsis in neonates can be detected with no loss of accuracy with a single site blood culture with blood volume of>or=1 ml.

Frequency and timing of symptoms in infants screened for sepsis: effectiveness of a sepsis-screening pathway

To determine the frequency and timing of symptoms and to evaluate the effectiveness of a sepsis-screening pathway in term and near-term infants, data were collected prospectively for a period of 1 year from December 1, 2000, to November 30, 2001. Results confirmed that a sepsis-screening pathway using a combination of at least 2 serial complete blood cell count and C-reactive protein measurements in both symptomatic and asymptomatic infants is a safe, simple strategy that prevents unnecessary treatment of infants with risk factors with antibiotics. However, most infants with presumed or suspected early-onset sepsis are symptomatic. Routine treatment of asymptomatic infants with risk factors or prior treatment with intrapartum antibiotics is unnecessary. A combined approach of screening in the presence of risk factors and /or symptoms of sepsis and adequate follow-up for infants discharged at less than 72 hours of age may help reduce unnecessary treatment of infants with antibiotics.

Neonatal sepsis workups in infants >/=2000 grams at birth: A population-based study

BACKGROUND

Few data are available on the outcome of neonatal sepsis evaluations in an era when intrapartum antibiotic therapy is common.

METHODS

We identified all newborns weighing >/=2000 g at birth who were ever evaluated for suspected bacterial infection at 6 Kaiser Permanente hospitals between October 1995 and November 1996, reviewed their records and laboratory data, and tracked them to 1 week after discharge. We analyzed the relationship between key predictors and the presence of neonatal bacterial infection.

RESULTS

Among 18 299 newborns >/=2000 g without major congenital anomalies, 2785 (15.2%) were evaluated for sepsis with a complete blood count and/or blood culture. A total of 62 (2.2%) met criteria for proven, probable, or possible bacterial infection: 22 (.8%) had positive cultures and 40 (1.4%) had clinical evidence of bacterial infection. We tracked all but 10 infants (.4%) to 7 days postdischarge. There were 67 rehospitalizations (2.4%; 2 for group B streptococcus bacteremia). Among 1568 infants who did not receive intrapartum antibiotics, initial asymptomatic status was associated with decreased risk of infection (adjusted odds ratio [AOR]:.26; 95% confidence interval [CI]:.11-.63), while chorioamnionitis (AOR: 2. 40; 95% CI: 1.15-5.00), low absolute neutrophil count (AOR: 2.84; 95% CI: 1.50-5.38), and meconium-stained amniotic fluid (AOR: 2.23; 95% CI: 1.18-4.21) were associated with increased risk. Results were similar among 1217 infants who were treated, except that maternal chorioamnionitis was not significantly associated with neonatal infection.

CONCLUSIONS

The risk of bacterial infection in asymptomatic newborns is low. Evidence-based observation and treatment protocols could be defined based on a limited set of predictors: maternal fever, chorioamnionitis, initial neonatal examination, and absolute neutrophil count. Many missed opportunities for treating mothers and infants exist.

Serum tumour necrosis factor in newborns at risk for infections

Tumour necrosis factor-alpha (TNF-alpha) is an important mediator in the pathogenesis of Gram-negative shock. In order to assess the role of TNF-alpha as a marker of the severity of infections in the neonates, serum TNF-alpha concentrations were determined at the time of septic work-up in 69 newborns (gestational age: 28-40 weeks). Nine patients had systemic infection (group A), four of them with signs of circulatory failure. Eleven patients had positive cultures of gastric aspiration or placental smears (group B) and 49 patients had completely negative septic work-up. Patients of group A had significantly more elevated serum TNF-alpha levels than patients of group B and C. Within group A, patients with circulatory failure had mean serum TNF-alpha concentration of 2165 +/- 817 pg/ml versus 27 +/- 8 pg/ml in newborns without shock. Serum TNF-alpha concentrations of more than 15 pg/ml detected systemic infections in eight out of nine patients. The specificity was 98% (1 elevated TNF-alpha concentration out of 60 non infected patients). These data indicate that premature neonates and term newborns are able to produce TNF-alpha when they are infected. Highly elevated TNF-alpha concentrations are found in severe systemic infections causing cardiovascular impairment.

Neonatal sepsis. Progress in diagnosis and management

Despite the rarity of proven neonatal bacterial sepsis (1 to 5 cases/1000 live births) systemic bacterial infections during the first month of life remain a major cause of morbidity and mortality. Most neonatal bacterial infections occur during the first week of life (early onset sepsis) and result from the spread of micro-organisms colonising the maternal genital tract into the amniotic cavity. Susceptible infants either inhale or swallow contaminated amniotic fluid and develop generalised sepsis. During the last decade, however, improvements in neonatal intensive care have permitted the survival of a population of very low birthweight infants, who remain hospitalised for many months, and who are at increased risk of developing nosocomial infections. The primary objective of the clinician caring for infants at risk for neonatal infection is to identify all potential cases of bacterial disease quickly and begin antibiotic therapy promptly. It is equally important, however, to determine which of these cases represent true infection, and therefore require a full course of antibiotics, and which do not. This paper reviews the epidemiology of bacterial infections in neonates, and critically evaluates current recommendations for the diagnosis and treatment of neonatal sepsis.

Premature rupture of the membranes (PROM): a neonatal approach

The risks to the infant following prolonged premature rupture of the amniotic membranes are those of prematurity and infection. After the 36th week of pregnancy, healthy infants of healthy mothers may be treated as uninfected neonates, as their risk of infection does not appear to be significant. Before this gestational age, infants should receive a complete laboratory evaluation for infection, including blood culture and spinal fluid examination, and antibiotic therapy should not be withheld until these laboratory tests are reported to the clinician. While the indiscriminate use of antibiotic treatment should be avoided, sepsis in the newborn can be a rapidly progressive disease, with minimal physical and laboratory findings at its onset. Therefore, until some method of laboratory evaluation that will detect all cases of neonatal sepsis rapidly, and leave no infected infant unidentified, the clinician must be alerted to the presence of an infant delivered after PROM and institute the appropriate evaluation and treatment as soon as possible.

Age-dependent susceptibility of neonatal rats to group B streptococcal type III infection: correlation of severity of infection and response of myeloid pools

A distinct age-dependent susceptibility to group B streptococcus type III (GBS) was demonstrated, utilizing a neonatal rat model. The most dramatic changes in susceptibility occurred within the first 7 days of postnatal life. To further investigate this susceptibility, experiments were performed utilizing two age groups of rats: (i) animals within the first 24 h of life (NB) and (ii) 7-day-old animals (7d). The infective dosage used was 10(4) GBS per g of body weight, a dose lethal to 100% of NB but only to 15% of 7d. The responses of the myeloid cells in the peripheral blood, spleen, and bone marrow were evaluated at intervals during the first 24 h post-GBS infection. The susceptibility of the NB to GBS appeared to be associated with a number of events, including smaller base-line levels of myeloid elements particularly in the bone marrow, a lag of at least 2 h in their initial response to infection, and an inability to maintain the myeloid pools. The band form of neutrophils appeared to be the predominant cell type in both total number and rapidity of response to infection. Moreover, an initial depletion of this band form was seen in both groups, which returned to base-line levels with recovery in 7d but persisted until death in NB animals. Similarly, shifts in numbers of peripheral nucleated erythrocytes appeared to reflect changes in the myeloid storage pools, with numbers of nucleated erythrocytes significantly decreasing in 7d animals with recovery in contrast to persistence in NB until death. Therefore, shifts in these cells in peripheral blood during infection appear to reflect the state of myeloid storage pools which parallel disease outcome.

Non-group D alpha-hemolytic streptococci: new neonatal pathogens

Review of the bacteriologic records of a large city-county hospital from 1970 through 1980 has indicated a substantial increase in the frequency of isolation of non-group D alpha-hemolytic streptococci from blood and cerebrospinal fluid of neonates since 1978. These organisms accounted for 23% of all cases of neonatal septicemia and meningitis in 1980, and as a group were exceeded only by group B streptococci (28%) in prevalence. Most neonates (91.2%) had early-onset infection (mean age = 1.4 days); approximately one-third were premature (less than 36 weeks' gestation). Maternal obstetrical complications were common. Nearly 80% of the infants had signs or symptoms suggesting bacterial sepsis. Findings such as concomitant meningitis, shock, chest roentgenogram abnormalities, leukopenia, abnormal numbers of immature neutrophils, and death were infrequent when compared to those accompanying other invasive neonatal bacterial infections, suggesting that non-group D alpha-hemolytic streptococci may be less virulent for the neonate or that neonatal host defense mechanisms are more effective in containing the infection. Careful surveillance for these potential neonatal pathogens seems warranted.