The early detection of neonatal sepsis by examination of liquid obtained from the external ear canal

The intensity of the fetal inflammatory response in intraamniotic inflammation with and without microbial invasion of the amniotic cavity

OBJECTIVE

Intraamniotic inflammation is a risk factor for adverse pregnancy and neonatal outcome, regardless of the presence or absence of a positive amniotic fluid (AF) culture. The purpose of this study was to determine whether the intensity of a fetal inflammatory response (FIR) differs between cases of intraamniotic inflammation with microbiologically proven infection and cases with negative AF cultures.

STUDY DESIGN

The FIR was examined in 89 cases of women with preterm premature rupture of membranes who delivered singleton preterm newborn infants within 48 hours of amniocentesis. AF was cultured for aerobic and anaerobic bacteria and for genital mycoplasmas. AF white blood cell (WBC) count and matrix metalloproteinase-8 (MMP-8) determinations were performed to assess the presence of intraamniotic inflammation. Intraamniotic inflammation was defined as an elevated AF MMP-8 concentration (>23 ng/mL). The intensity of the FIR was determined by the umbilical cord plasma concentrations of C-reactive protein (CRP). Patients were divided into 3 groups according to the presence or absence of intraamniotic inflammation and AF culture results: group 1, without intraamniotic inflammation and with a negative AF culture (n = 28); group 2, with intraamniotic inflammation and with a negative AF culture (n = 26); group 3, with a positive AF culture (n = 35).

RESULTS

Neonates who were born to mothers with intraamniotic inflammation and negative AF cultures had a significantly higher median umbilical cord plasma CRP concentration than did those without intraamniotic inflammation and a negative AF culture (P < .005) but a significantly lower median cord plasma CRP concentration than did those with proven AF infection (P < .05). Patients with intraamniotic inflammation and a negative AF culture had significantly higher median AF MMP-8 concentrations and WBC count than did those without intraamniotic inflammation and a negative AF culture (P < .001). However, there was no significant difference in the median AF MMP-8 and WBC count between patients with intraamniotic inflammation and a negative AF culture and those with proven AF infection (MMP-8, P > .1, and WBC, P = .09).

CONCLUSION

Intraamniotic inflammation without documented AF infection is a risk factor for a systemic FIR. However, the magnitude of the FIR in those cases was lower than in those with documented AF infection.

Diagnostic tests for bacterial infection from birth to 90 days--a systematic review

AIM

To determine the clinical value of common diagnostic tests for bacterial infection in early life.

METHODS

A Medline search (1966-95) was undertaken to identify studies that reported the assessment of a diagnostic "test," predicting the presence or absence of bacterial infection in infants up to 90 days of age. The quality of each selected study was assessed using defined criteria. Data were extracted twice to minimise errors.

RESULTS

Six hundred and seventy articles were identified. Two independent investigators agreed that 194 studies met the inclusion criteria (kappa = 0.85), 52 of which met primary quality criteria; 23 studies reported data on (a) haematological indices, (b) C reactive protein evaluation, and (c) surface swab assessment. For haematological indices, the likelihood ratios for individual tests ranged from 20.4 (95% confidence interval 7.3 to 56.8) for a white cell count < 7000/mm3 to 0.12 (0.04 to 0.37) for an immature:total (I:T) white cell ratio < 0.2. For C reactive protein evaluation, the likelihood ratios ranged from 12.56 (0.79 to 199.10) for a value of > 6 mg/l to 0.22 (0.08 to 0.65) for a negative value. For surface swab assessment, the likelihood ratios ranged from 33.6 (2.1 to 519.8) for a positive gastric aspirate culture to 0.08 (0.006 to 1.12) for microscopy of ear swab material that did not show any neutrophils. Likelihood ratios for combinations of these individual tests ranged from 10.17 (3.64 to 28.41) to 0.47 (0.22 to 1.00).

CONCLUSIONS

The methodological quality of studies assessing the accuracy of diagnostic tests is generally poor. Even in rigorous studies, the reported accuracy of the tests varies enormously and they are of limited value in the diagnosis of infection in this population.

Role of body surface cultures in prediction of sepsis in a neonatal intensive care unit

An analysis of surface cultures of 35 preterm infants of less than 33 weeks gestational age hospitalized in a neonatal intensive care unit was made. The babies had received neither antiseptic nor antibiotic therapy prior to collection of specimens. Surface cultures were collected on the 4th or 5th day of life from 16 skin or mucosal sites. At the onset of a febrile episode within 14 days of collection of surface swabs, a blood culture was done on 31 infants (four did not develop fever) and the results were compared with the surface cultures. Sepsis was diagnosed by positive blood culture in twenty neonates (57.1%). With this frequency of sepsis, the optimum sensitivity, specificity and positive predictive values of surface cultures were 60%, 27% and 60%, respectively. These values did not improve substantially for any anatomic site cultured or for any pathogen recovered. We conclude that surface cultures are of limited value in predicting the aetiology of sepsis in neonates.

Elevation of amniotic fluid interleukin 6 (IL-6), IL-8 and granulocyte colony stimulating factor (G-CSF) in term and preterm parturition

We determined the levels of inflammatory cytokines such as interleukin 6 (IL-6) granulocyte-colony stimulating factor (G-CSF) and IL-8 in the amniotic fluids from women with premature or term delivery. Cytokines were detectable even in the absence of apparent infection (group 1), but much higher cytokine levels were found in cases of intrauterine infection, particularly in cases of premature delivery (group 2). In cases of term delivery (groups 3-5), all of the cytokine levels showed c. 3- to 4-fold increase during labor pain (group 4) and an 8- to 13-fold increase in the presence of endotoxin (group 5), in comparison with the levels in cases where neither factor was present (group 3). Regarding infection, the cytokine levels were 20- to 30-fold higher in chorioamnionitis-positive premature delivery group (group 2), than in the infection-negative group (group 1). All the cytokines were simultaneously induced in amniotic fluid by labor pain and infection, and a significant positive correlation was observed among these three cytokine levels. In-vitro culture system and immunohistochemical study indicated that the cytokines in the amniotic fluid appeared to originate from trophoblasts and decidual cells. Thus, infection and labor pain may trigger the production of inflammatory cytokines at term as well as premature delivery and the determination of these cytokine levels will be a good indication for the prediction of the presence of intrauterine infection.

Superficial cultures in neonatal sepsis evaluations. Impact on antibiotic decision making

The authors performed a retrospective analysis of neonatal superficial cultures and their effect on antimicrobial decision making during a nine-month period at Nashville General Hospital. They obtained and reviewed charts of infants (n = 66) having paired superficial (skin and/or gastric aspirate) and deep (blood and cerebrospinal fluid) cultures for the evaluation of early-onset sepsis. Superficial cultures were positive for pathogens (any streptococcus or enteric gram-negative) in 15% (10/66) of cases. Antimicrobial decision making was affected in only one of these cases, and in a seemingly inappropriate manner. In summary, there was no evidence or review that superficial cultures used in sepsis evaluation influenced physician antimicrobial decision making; in one case they may have led to unnecessary antibiotic exposure.

Prolonged rupture of the fetal membranes and neonatal outcome

In order to establish the incidence of neonatal infection following prolonged (greater than 24 hours) rupture of the fetal membranes (PROM) and assess outcome of two year retrospective study was undertaken. The names of all babies born following PROM were obtained from the computerised obstetric record and the bacteriological results and outcome reviewed. Of 208 babies born following PROM only three had blood cultures containing pathogens--all of whom were of less than 1500 g birthweight and all of whom died. This represents a fivefold increased frequency of infection for premature babies but no increased risk for full term babies. The overall incidence of infection was much lower than in previous series and this may be due to performing amniocentesis as soon as possible following rupture and inducing labour where there was evidence of incipient chorioamnionitis. Meningitis was not associated with prolonged rupture of the membranes. The mortality for these babies was higher than those of babies without PROM in the 28-31 week gestation group. This was strongly associated with early onset of membrane rupture and none of the babies born following membrane rupture prior to 20 weeks gestation survived. Non-infective pulmonary disease was the main cause of increased mortality.

Group B streptococci in pharyngeal aspirates at birth and the early detection of neonatal sepsis

The pharyngeal aspirates collected from 400 babies at the time of delivery were examined for the presence of bacteria, especially group B streptococci. Aspirates from 79 babies were found to contain viable bacteria, including 4 with group B streptococci; one of these 4 babies developed streptococcal meningitis within 24 hours. The group B streptococci were seen on a Gram-stained film of the aspirate, and were detectable by coagglutination and countercurrent immunoelectrophoresis within 4 hours and by culture after 24 hours. Examination of pharyngeal aspirates may be of value as a screening test for neonatal sepsis.

Early diagnosis of neonatal bacteremia by buffy-coat examination

This study demonstrates the value of the buffy-coat smear examination in the early diagnosis of neonatal bacteremia. It is inexpensive, easy to perform, and relatively efficient. In most situations large numbers of bacteria could be seen in each positive smear. Unfortunately, the presence of a positive buffy-coat smear was often associated with a poor prognosis; more than one half (four of seven) of infants with positive smears died.

Early recognition of neonatal sepsis. The value of bacteriologic studies of gastric aspirate and external ear canal material

Cultures and gram stains of gastric and external ear canal contents can greatly assist the physician in the early diagno sis of newborn infections acquired in utero or during birth.