The utility of tracheal aspirate cultures in the immediate neonatal period

Correlation of Polymorphonuclear Cell Burden and Microbial Growth to the Inflammatory Cytokines in Tracheal Aspirates from Ventilated Preterm Infants

OBJECTIVE

 The significance of the presence of microorganisms and polymorphonuclear cells in the tracheal aspirates (TAs) of ventilated preterm infants is not well known. Our aim was to correlate information about the presence of polymorphonuclear cells with microbial growth and the cytokine milieu in the TAs of infants who have been intubated for >7 days.

STUDY DESIGN

 TAs were collected from infants who had been intubated for 7 days or longer. Respiratory cultures were performed, and infants were stratified based on the presence and abundance of polymorphonuclear cells and microbial growth. Cytokines were measured in the TAs of each of the respective groups.

RESULTS

 In the 19 infants whose TAs were collected, the presence of at least moderate WBC with presence of microbial growth was positively associated with the presence of interleukin (IL)-10, IL-1β, IL-8, and tumor necrosis factor (TNF)-α. The presence of at least moderate WBC, with or without microbial growth, was correlated positively with the presence of IL-8 and TNF-α.

CONCLUSION

 There are higher levels of proinflammatory cytokines (especially, IL-10, IL-1β, and TNF-α) in TAs with higher cell counts and presence of microbial growth. The findings suggest that the presence of microbial growth correlated with inflammatory burden and warrant a larger study to see if treatment of microbial growth can ameliorate the inflammatory burden.

KEY POINTS

· Concomitant evaluation of inflammatory cells, microbial growth, and cytokines in tracheal aspirates.. · Moderate TA WBC with presence of microbial growth associated with IL-10, IL-1β, IL-8, and TNF-α.. · Moderate TA WBC, with/without microbial growth, correlated with the presence of IL-8 and TNF-α.. · Higher levels of IL-10, IL-1β, and TNF-α correlated with higher TA cell counts and microbial growth..

Incidence, Risk Factors, Short-term Outcomes, and Microbiome of Ventilator-associated Pneumonia in Very-low-birth-weight Infants: Experience at a Single Level III Neonatal Intensive Care Unit

BACKGROUND

Ventilator-associated pneumonia (VAP) is a common hospital-acquired infection in neonates on invasive mechanical ventilation, resulting in high morbidity and mortality. The objective of this study is to determine the incidence, risk factors, short-term outcomes and microbiome associated with VAP in very-low-birth-weight (VLBW) infants born at <32 weeks of gestational age (GA).

METHODS

Retrospective study of intubated VLBW infants born at <32 weeks of GA admitted to the Los Angeles General Medical Center neonatal intensive care unit from July 2015 to July 2021 who had routine tracheal aspirate cultures obtained. Neonates were retrospectively classified into 3 groups, confirmed VAP, suspected VAP and no VAP, for comparison of risk factors, outcomes and airway microbial colonization.

RESULTS

Eighty-seven infants met inclusion criteria with a mean GA of 26.1 ± 1 weeks and mean birth weight of 812 ± 281 g. The incidence of VAP was 7.8 per 1000 ventilator days, and the most common causative organisms were Gram-positive organisms (39%), predominantly coagulase-negative Staphylococcus. Duration of postnatal dexamethasone exposure predicted VAP compared to no VAP (coefficient, 0.31; 95% CI 0.03-0.59; P = 0.03) after adjusting for duration of intubation, surfactant use and antenatal steroid exposure. Infants with VAP had higher rate of grade 2/3 bronchopulmonary dysplasia (P = 0.03) and longer hospital stay (P = 0.04).

CONCLUSIONS

VAP occurs at a high rate in VLBW infants who are exposed to prolonged dexamethasone use. It is predominantly caused by Gram-positive organisms.

Use of Optical Redox Imaging to Quantify Alveolar Macrophage Redox State in Infants: Proof of Concept Experiments in a Murine Model and Human Tracheal Aspirates Samples

Emerging data indicate that lung macrophages (LM) may provide a novel biomarker to classify disease endotypes in bronchopulmonary dysplasia (BPD), a form of infant chronic lung disease, and that augmentation of the LM phenotype may be a potential therapeutic target. To contribute to this area of research, we first used Optical Redox Imaging (ORI) to characterize the responses to H2O2-induced oxidative stress and caffeine treatment in an in vitro model of mouse alveolar macrophages (AM). H2O2 caused a dose-dependent decrease in NADH and an increase in FAD-containing flavoproteins (Fp) and the redox ratio Fp/(NADH + Fp). Caffeine treatment did not affect Fp but significantly decreased NADH with doses of ≥50 µM, and 1000 µM caffeine treatment significantly increased the redox ratio and decreased the baseline level of mitochondrial ROS (reactive oxygen species). However, regardless of whether AM were pretreated with caffeine or not, the mitochondrial ROS levels increased to similar levels after H2O2 challenge. We then investigated the feasibility of utilizing ORI to examine macrophage redox status in tracheal aspirate (TA) samples obtained from premature infants receiving invasive ventilation. We observed significant heterogeneity in NADH, Fp, Fp/(NADH + Fp), and mitochondrial ROS of the TA macrophages. We found a possible positive correlation between gestational age and NADH and a negative correlation between mean airway pressure and NADH that provides hypotheses for future testing. Our study demonstrates that ORI is a feasible technique to characterize macrophage redox state in infant TA samples and supports further use of this method to investigate lung macrophage-mediated disease endotypes in BPD.

Association of Endotracheal Aspirate Culture Variability and Antibiotic Use in Mechanically Ventilated Pediatric Patients

IMPORTANCE

Endotracheal aspirate cultures are commonly collected from patients with mechanical ventilation to evaluate for ventilator-associated pneumonia or tracheitis. However, the respiratory tract is not sterile, making differentiating between colonization from bacterial infection challenging, and results may be unreliable owing to variable specimen quality and sample processing across laboratories. Despite these limitations, clinicians routinely interpret bacterial growth in endotracheal aspirate cultures as evidence of infection, sometimes regardless of organism significance, prompting antibiotic treatment.

OBJECTIVE

To assess the variability in endotracheal aspirate culture rates and the association between culture rates and antibiotic prescribing among patients with mechanical ventilation across children's hospitals in the US.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional retrospective analysis of data obtained from the Children's Hospital Association Pediatric Health Information System database between January 1, 2016, through December 31, 2019. Participants were all patients hospitalized with mechanical ventilation aged less than 18 years.

EXPOSURES

A charge for an endotracheal aspirate culture on a ventilated day.

MAIN OUTCOMES AND MEASURES

Endotracheal aspirate culture rate and antibiotic days of therapy per ventilated days. For mechanical ventilation, clinical transaction classification codes for mechanical ventilation other unspecified ventilator assistance were used. To identify respiratory cultures, the laboratory test code for aerobic culture was used and relevant keywords (ie, respiratory tract, sputum) were used to identify sources in the hospital charge description master.

RESULTS

A total of 152 132 patients were identified among 31 hospitals. Among these patients, 79 691 endotracheal aspirate cultures were collected on a ventilator-day (patients aged less than 1 year, 44%; 1-4 years, 27%, 5-11 years. 16%, and 12-18 years, 13%; 3% were Asian; 17% Hispanic; 21% non-Hispanic Black; 45% Non-Hispanic White patients; 14% were other; 56% of patients were male, 44% were female). The overall median rate of culture use was 46 per 1000 ventilator-days (IQR, 32-73 cultures per 1000 ventilator-days). The endotracheal aspirate culture rate was positively correlated with the hospital's antibiotic days of therapy rate (R = 0.46; P = .009). In a multivariable model adjusting for patient-level and hospital-level characteristics and among patients with mechanical ventilation, each additional endotracheal aspirate culture was associated with 2.87 (95% CI, 2.74-3.01) higher odds of receiving additional days of therapy compared with patients who did not receive and endotracheal aspirate culture.

CONCLUSIONS AND RELEVANCE

In this study, notable variability was found in endotracheal aspirate culture rates across US pediatric hospitals and pediatric intensive care units, and endotracheal aspirate culture use was associated with increased antibiotic use. These findings suggest an opportunity for diagnostic and antibiotic stewardship to standardize testing and treatment of suspected ventilator-associated infections in pediatric patients with mechanical ventilation pediatric patients.

Lack of utility of tracheal aspirates in the management of suspected pneumonia in intubated neonates

OBJECTIVES

To evaluate the utility of tracheal aspirates in suspected pneumonia in intubated neonates and to measure the burden of antibiotic use associated with a positive tracheal aspirate culture.

DESIGN

Retrospective cohort study between January 2016 and December 2017.

SETTING

A level IV neonatal intensive care unit (NICU).

PATIENTS

Intubated patients with a tracheal aspirate culture.

METHODS

Data on temporally associated clinical measures of illness, laboratory and radiographic testing, and clinical demographic information were analyzed.

RESULTS

Positive tracheal aspirate cultures were associated with lower birth weight and a normal immature to total neutrophil ratio (I/T ratio). Positive tracheal aspirates were not significantly associated with clinical, laboratory, or radiographic markers used in clinical practice to screen for infection. Despite the lack of positive clinical associations, a positive tracheal aspirate culture was associated with increased risk of prolonged antibiotic exposure.

CONCLUSION

These findings suggest that positive tracheal aspirates do not always represent clinical infection and may result in unnecessary antibiotic exposure.

Elevated neutrophil-lymphocyte ratios in extremely preterm neonates with histologic chorioamnionitis

OBJECTIVE

Histologic chorioamnionitis (HCA) is a placental inflammation linked to preterm birth and adverse neonatal outcome. The neutrophil-lymphocyte ratio (NLR) can identify various inflammatory disorders, however its utility in HCA is not clear. Our goal was to examine NLR values and HCA diagnoses in at-risk pregnancies and neonates.

STUDY DESIGN

We retrospectively analyzed the EHR of mothers and preterm (<33 wk GA) neonates with or without HCA (identified by placental histology). The NLR was calculated from complete blood counts in laboring women and in their neonates (0-24 h of life).

RESULT

In 712 consecutive gestations, 50.8% had HCA (26.5% fetal HCA). The neonatal NLR (0-12 h, 13-24 h) predicted fetal HCA better than chance alone (p = 0.01 and 0.002, respectively).

CONCLUSION

Early NLR elevation in preterm neonates is consistent with a diagnosis of fetal HCA. The NLR may identify preterm neonates at risk for HCA-related complications.

Tracheal aspirate presepsin: a promising biomarker in early onset neonatal pneumonia

The early recognition and management of early-onset neonatal pneumonia is a challenge facing intensivists. Presepsin is an emerging immunologic and inflammatory biomarker that has been used for early non-culture-based detection of infection. We aimed to clarify the potential of presepsin assessed in tracheal aspirate of newborns to identify pneumonia. This prospective case - control study was conducted on 60 intubated neonates: Thirty neonates with pneumonia diagnosed according to clinical, radiological, and laboratory criteria as pneumonia group and thirty age and sex-matched intubated neonates without pneumonia as a control group. All neonates underwent full clinical evaluation and laboratory investigations. Plasma and tracheal aspirate presepsin was determined on the first day of life. The means of tracheal aspirate and plasma presepsin and CRP (525.55 ± 94.62 pg/mL, 670.95 ± 120.38 pg/mL and 26.4 ± 11.2 mg/L, respectively) were significantly higher in pneumonia group than control group (252.51 ± 104.95 pg/mL, 553.79 ± 117.48 pg/mL, 15.1 ± 3.1 mg/L, respectively) (p < .001 each). Receiver operating characteristic curve analysis for tracheal aspirate and plasma presepsin and CRP levels for the prediction of early-onset neonatal pneumonia was designed. Sensitivity was 86.6, 70 and 56.7%, respectively, while specificity was 90, 73.3, 53.3%, respectively, at a cut-off point of 385 pg/mL, 605 pg/mL and 36 mg/L, respectively [area under the curve (AUC) = 0.97, 0.74 and 0.51, respectively, p < .001, .001 and .44, repectively]. In conclusion, tracheal aspirate presepsin is increased in early-onset neonatal pneumonia and outperformed other plasma biomarkers in diagnosing neonatal pneumonia.

Infection control and other stewardship strategies in late onset sepsis, necrotizing enterocolitis, and localized infection in the neonatal intensive care unit

Suspected or proven late onset sepsis, necrotizing enterocolitis, urinary tract infections, and ventilator associated pneumonia occurring after the first postnatal days contribute significantly to the total antibiotic exposures in neonatal intensive care units. The variability in definitions and diagnostic criteria in these conditions lead to unnecessary antibiotic use. The length of treatment and choice of antimicrobial agents for presumed and proven episodes also vary among centers due to a lack of supportive evidence and guidelines. Implementation of robust antibiotic stewardship programs can encourage compliance with appropriate dosages and narrow-spectrum regimens.

Technical assessment of the neonatal early-onset sepsis risk calculator

The use of the neonatal early-onset sepsis risk calculator, developed by Kaiser Permanente Northern California (CA, USA), is increasing for the management of late preterm and full term newborn babies at risk for early-onset sepsis. The calculator is based on a robust logistic regression model that provides quantitative individualised estimates of early-onset sepsis risk. Low sensitivity for prediction of sepsis at birth shows that standard perinatal risk factors alone are insufficient for ascertainment of neonatal early-onset sepsis. Performance is improved by the addition of physical examination findings at birth, but the sensitivity of combined findings remains limited. The present implementation of the calculator integrates risk factors and examination findings. A methodological error in adapting the regression for application in the population (rather than the development sample) and several subsequent modifications compromise the accuracy of quantitative predictions of the absolute risk of sepsis, but these factors are not expected to seriously undermine the use of the calculator for risk stratification. The calculator has served as an instrument of change away from previously recommended categorical risk ascertainment strategies, and its implementation reduces the need for diagnostic testing and empirical antibiotic treatment without apparent ill effects. However, the calculator should not be relied on to provide accurate estimates for individuals with regard to absolute risk of early-onset sepsis in newborn babies.

Challenging the "Culture" of the Tracheal Aspirate

The tracheal aspirate (TA) culture is commonly ordered in the NICU, but it has low sensitivity and specificity, limited by contamination. Interpretation of a TA culture out of context can lead to antibiotic overuse, which should be avoided. Clinicians should practice caution in the diagnosis of congenital pneumonia and use newer, published approaches to the diagnosis of ventilator-associated pneumonia in neonates. A subset of neonatal patients with risk factors of maternal fever or chorioamnionitis requiring intubation may benefit from TA culture performed within 12 hours after birth, to help identify an organism when blood culture may be negative, and tailor antimicrobial therapies. The more invasive, but more sensitive, technique of nonbronchoscopic bronchoalveolar lavage should be considered in older infants when bacterial isolation from the lower respiratory tract is necessary, because TA culture cannot distinguish between colonization and infection in that population.

Management of the neonate at risk for early-onset Group B streptococcal disease (GBS EOD): new paediatric guidelines in Belgium

Despite group B streptococcal (GBS) screening in late pregnancy and intrapartum antimicrobial prophylaxis, early-onset sepsis in neonates remains a common source of neonatal morbidity and mortality especially in preterm neonates. The identification of neonates with early-onset sepsis is usually based on perinatal risk factors. Clinical signs are aspecific and laboratory tests are not sensitive. Therefore, many clinicians will overtreat at-risk infants. Inappropriate treatment with antibiotics increases the risk for late-onset sepsis, necrotizing enterocolitis, mortality, and prolongs hospitalisation and costs. In 2003, the Belgian Health Council published guidelines for the prevention of perinatal GBS infections. This report presents the Belgian paediatric management guidelines, which have been endorsed by the Belgian and Flemish societies of neonatology and paediatrics. The most imported changes in the 2014 guidelines are the following: recommendations for a lumbar puncture; clarification of normal spinal fluid parameters and blood neutrophil indices corrected for gestation age; specific timing for diagnostic testing after birth; no indication for diagnostic testing in asymptomatic newborns unless additional risk factors; a revised algorithm for management of neonates according to maternal and neonatal risk factors; and premature infants described as those below 35 weeks instead of 37 weeks. The guidelines were made on the basis of the best evidence and on expert opinion when inadequate evidence exists.

Adjunct laboratory tests in the diagnosis of early-onset neonatal sepsis

Early-onset sepsis remains a major diagnostic problem in neonatal medicine. Definitive diagnosis depends on cultures of blood or other normally sterile body fluids. Abnormal hematological counts, acute-phase reactants, and inflammatory cytokines are neither sensitive nor specific, especially at the onset of illness. Combinations of measurements improve diagnostic test performance, but the optimal selection of analytes has not been determined. The best-established use of these laboratory tests is for retrospective determination that an infant was not infected, based on failure to mount an acute-phase response over the following 24 to 48 hours.