Late-onset Bloodstream Infections in Hospitalized Infants
Late-onset Bloodstream Infections in Hospitalized Infants
We identified all infants born ≥37 weeks gestational age (GA), admitted ≤120 days of life to 315 NICUs managed by the Pediatrix Medical Group in the United States and discharged from 1997 to 2010. We used an administrative database that prospectively captures information from daily progress notes, laboratory results, admission and discharge notes and maternal information. Clinicians generated notes using a computer-assisted tool on all infants cared for by the Pediatrix Medical Group. We excluded infants: (1) discharged before day of life (DOL) 4; (2) with major congenital anomalies and (3) who had surgery before DOL 120. We collected information on neonatal and maternal demographics, discharge data and all blood cultures drawn for each patient.
We defined late-onset BSIs as a positive blood culture for an identified pathogen if the culture was obtained between 4 and 120 days of life; early-onset BSIs were defined as a positive blood culture in the first 3 days of life. Multiple positive blood cultures for the same organism within 21 days were considered a single episode of sepsis, and we excluded organisms considered contaminants, including nonspeciated streptococci, Bacillus sp., Corynebacterium sp., diphtheroids and Gram-positive rods other than Listeria sp., Lactobacillus sp., Micrococcus sp., Stomatococcus sp. and Bacteroides sp. We included CoNS in the analysis if there were: (1) 2 positive blood cultures for CoNS in a 4-day period, (2) 3 positive blood cultures for CoNS in a 7-day period or (3) 4 positive blood cultures in a 10-day period.
We excluded infants with major congenital anomaly, which was defined as an anomaly presenting at birth with 1 of the following characteristics: (1) lethal; (2) life-shortening; (3) life-threatening; (4) requiring major surgery or (5) affecting the infant's quality of life in a significant way. The neonatologist recorded maternal antibiotic use on admission of the infant to the NICU. We classified infants as small for GA if birth weight was <10th percentile for age and sex. Mortality was calculated for each organism, considering the organism identified closest to death as the cause of death for infants with >1 organism identified. If >1 organism was identified at the same day, for the culture closest to death, we considered both organisms as the cause of death.
We examined the distribution of positive blood cultures and calculated the incidence of sepsis per 1000 NICU admissions. We used time-to-event analysis with Cox model hazard ratio to assess the risk factors for late-onset BSIs among hospitalized infants and allowed for multiple failures in the Cox model. Risk of late-onset BSIs was the dependent variable, and the covariates included were GA, sex, ethnicity, small-for-gestational-age status, Apgar score at 5 minutes, mode of delivery, use of antenatal antibiotics, history of early-onset BSIs and discharge year. To examine the relationship between late-onset BSIs and risk of death, we used multivariable logistic regression controlling for the same covariates.
STATA 12.1 (College Station, TX) was used to perform the statistical analyses. All statistical tests were 2-sided with significance defined as P < 0.05. Permission to conduct this analysis was provided by the Duke University Institutional Review Board.
Materials and Methods
Study Design and Setting
We identified all infants born ≥37 weeks gestational age (GA), admitted ≤120 days of life to 315 NICUs managed by the Pediatrix Medical Group in the United States and discharged from 1997 to 2010. We used an administrative database that prospectively captures information from daily progress notes, laboratory results, admission and discharge notes and maternal information. Clinicians generated notes using a computer-assisted tool on all infants cared for by the Pediatrix Medical Group. We excluded infants: (1) discharged before day of life (DOL) 4; (2) with major congenital anomalies and (3) who had surgery before DOL 120. We collected information on neonatal and maternal demographics, discharge data and all blood cultures drawn for each patient.
Definitions
We defined late-onset BSIs as a positive blood culture for an identified pathogen if the culture was obtained between 4 and 120 days of life; early-onset BSIs were defined as a positive blood culture in the first 3 days of life. Multiple positive blood cultures for the same organism within 21 days were considered a single episode of sepsis, and we excluded organisms considered contaminants, including nonspeciated streptococci, Bacillus sp., Corynebacterium sp., diphtheroids and Gram-positive rods other than Listeria sp., Lactobacillus sp., Micrococcus sp., Stomatococcus sp. and Bacteroides sp. We included CoNS in the analysis if there were: (1) 2 positive blood cultures for CoNS in a 4-day period, (2) 3 positive blood cultures for CoNS in a 7-day period or (3) 4 positive blood cultures in a 10-day period.
We excluded infants with major congenital anomaly, which was defined as an anomaly presenting at birth with 1 of the following characteristics: (1) lethal; (2) life-shortening; (3) life-threatening; (4) requiring major surgery or (5) affecting the infant's quality of life in a significant way. The neonatologist recorded maternal antibiotic use on admission of the infant to the NICU. We classified infants as small for GA if birth weight was <10th percentile for age and sex. Mortality was calculated for each organism, considering the organism identified closest to death as the cause of death for infants with >1 organism identified. If >1 organism was identified at the same day, for the culture closest to death, we considered both organisms as the cause of death.
Statistical Methods
We examined the distribution of positive blood cultures and calculated the incidence of sepsis per 1000 NICU admissions. We used time-to-event analysis with Cox model hazard ratio to assess the risk factors for late-onset BSIs among hospitalized infants and allowed for multiple failures in the Cox model. Risk of late-onset BSIs was the dependent variable, and the covariates included were GA, sex, ethnicity, small-for-gestational-age status, Apgar score at 5 minutes, mode of delivery, use of antenatal antibiotics, history of early-onset BSIs and discharge year. To examine the relationship between late-onset BSIs and risk of death, we used multivariable logistic regression controlling for the same covariates.
STATA 12.1 (College Station, TX) was used to perform the statistical analyses. All statistical tests were 2-sided with significance defined as P < 0.05. Permission to conduct this analysis was provided by the Duke University Institutional Review Board.
Source...