Positive Tracheal Aspirate Research Articles

Contaminated Ventilator Air Flow Sensor Linked toBacillus cereusColonization of Newborns

We investigated Bacillus cereus–positive tracheal aspirates from infants on ventilators in a neonatal intensive care unit. Multilocus sequence typing determined a genetic match between strains isolated from samples from a case-patient and from the air flow sensor in the ventilator. Changing the sterilization method for sensors to steam autoclaving stopped transmission.

Use of a Microbiology Database to Analyse Changes in Resistance Patterns in the ICU

We combined our ICNARC dataset with a microbiology database in a mixed general and neurosurgical intensive care unit (ICU). We identified 1,097 positive tracheal aspirate cultures in 2,525 consecutive adult patients admitted over a three-year period. The database enabled us to track changes in tracheal aspirate flora and antibiotic resistance patterns following the introduction of a hospital-wide restrictive antibiotic policy targeted at Clostridium difficile infection (CDI) reduction. The pattern of organism types was unchanged although meticillin resistance in Staphylococcus aureus decreased from 33% to 17% (p=0.014). Sensitivity of tracheal aspirate cultures to empirical antibiotics increased from 67% to 86% in the first five days after hospital admission and from 53% to 81% in the subsequent five days. A combined microbiology/ICU database allowed resistance patterns to be identified within our unit. We believe this should be developed nationally both for research and for real time targeting of empiric antibiotic therapy.

The use of C-reactive protein in predicting bacterial co-Infection in children with bronchiolitis.

Background:Bronchiolitis is a potentially life-threatening respiratory illness commonly affecting children who are less than two years of age. Patients with viral lower respiratory tract infection are at risk for co-bacterial infection.Aim:The aim of our study was to evaluate the use of C-reactive protein (CRP) in predicting bacterial co-infection in patients hospitalized for bronchiolitis and to correlate the results with the use of antibiotics.Patients and Methods:This is a prospective study that included patients diagnosed with bronchiolitis admitted to Makassed General Hospital in Beirut from October 2008 to April 2009. A tracheal aspirate culture was taken from all patients with bronchiolitis on admission to the hospital. Blood was drawn to test C-reactive protein level, white cell count, transaminases level, and blood sugar level.Results:Forty-nine patients were enrolled in the study and were divided into two groups. Group 1 included patients with positive tracheal aspirate culture and Group 2 included those with negative culture. All patients with a CRP level ≥2 mg/dL have had bacterial co-infection. White cell count, transaminases and blood sugar levels were not predictive for bacterial co-infection. The presence of bacterial co-infection increased the length of hospital stay in the first group by 2 days compared to those in the second group.Conclusion:Bacterial co-infection is frequent in infants with moderate to severe bronchiolitis and requires admission. Our data showed that a CRP level greater than 1.1 mg/dL raised suspicion for bacterial co-infection. Thus, a tracheal aspirate should be investigated microbiologically in all hospitalized patients in order to avoid unnecessary antimicrobial therapy and to shorten the duration of the hospital stay.

Significance of the isolation of Candida species from airway samples in critically ill patients: a prospective, autopsy study

Recovery of Candida from the respiratory tract is common. Large series on the incidence of histologically proven Candida pneumonia in intensive care unit (ICU) patients are lacking. A two-year prospective study of all autopsies performed on patients who died in the ICU was conducted. For autopsy-proven cases of Candida pneumonia, we required microscopic demonstration of yeast invasion in lung autopsy specimens that showed inflammation. We looked for differences in incidence in patients with and without respiratory samples positive for Candida species pre-mortem. Of 1,587 patients admitted to the ICU, 301 (19%) died of whom 232 (77%) were autopsied. Of those, 135 patients (58%) had histopathological evidence of pneumonia. A total of 77 cases (57%) with pneumonia at autopsy had positive tracheal aspirate and/or BAL cultures for Candida spp. performed during the preceding two weeks. No cases of Candida pneumonia were identified amongst those 77 cases. In the other 58 patients with autopsy-proven pneumonia and no Candida isolation pre-mortem, no Candida pneumonia was observed either. Despite frequent isolation of Candida spp. from the airways, over a two-year period no single case of Candida pneumonia was found among the patients with evidence of pneumonia on autopsy. This study indicates that Candida pneumonia is an extremely rare occurrence in ICU patients and provides further evidence against the common use of antifungal therapy triggered by a microbiology report of Candida isolation from the respiratory tract.

High levels of CXCL8 in tracheal aspirate samples taken at birth are associated with adverse respiratory outcome only in preterm infants younger than 28 weeks gestation

We investigated the relation between perinatal endotracheal colonization, the associated cytokine response and respiratory outcome in ventilated preterm neonates. Between September 1999 and March 2002, a cohort of 141 neonates with a gestational age <31 weeks requiring ventilation directly after birth, were followed prospectively. All were admitted to the Neonatal Intensive Care Unit, University Hospital of Antwerp, Belgium. A tracheal aspirate (TA) sample was collected soon after birth and was processed for microbiological examination, leukocyte count, and cytokine analysis (interleukins [IL] IL-1beta, IL-6, CXCL8 (formerly called IL-8), IL-10, IL-12p70 and tumor necrosis factor alpha [TNF-alpha]). Together with the prospectively registered patient's comorbidities and severity of disease, these inflammatory parameters were analyzed in a multivariate Cox proportional hazards model with time of extubation and duration of oxygen therapy as main outcome measures. Of the 141 patients included, 31 (22%) died before discharge from the unit and 37 (26%) had a positive TA culture. Independent predictors of duration of mechanical ventilation were: gestational age <28 weeks, degree of respiratory distress syndrome (RDS) at birth, significant patent ductus arteriosus (PDA), the SNAP-score, and high levels of CXCL8 (>4,153 pg/ml) in TA only in neonates with a gestational age <28 weeks. Variables associated with extended duration of oxygen therapy were gestational age <28 weeks, birth weight <1,000 g, degree of RDS at birth, and duration of mechanical ventilation.

MII + PH PROBE AND CORRELATION WITH TRACHEAL PEPSIN ASPIRATES IN 6 PATIENTS WITH MODERATE TO SEVERE PERSISTENT ASTHMA

Introduction: Coexistence of asthma, GER and mircroaspiration have been proposed previously. Non-acid reflux measures and availability of airway pepsin as markers of microaspiration have become recently available. We present the first series of cases from a retrospective chart review. Methods: Six patients (range 5 to 15 years) with moderate to severe asthma who had bronchoscopy as well as combined MII + pH probe studies (all greater then 18 hours) as part of their evaluations were reviewed. Pulmonary aspirates were assayed for pepsin. None had clinical suspicion of oral aspiration or radiological evidence of aspiration. One had history of TEF repair and one was subsequently diagnosed with a mild CF by genotype. All patients had impedance pH studies performed off acid suppression medications. NASPGHAN criteria for acid GER, number of MII episodes (up to the cervical esophagus) and symptom index for cough was recorded. Pepsin was assayed using floreroscein isothiocyanate casein. Normal airway aspirates are undetectable for pepsin. Results: All cases had positive airway pepsin (range 12.7 to 78 ng/ml). One case met criteria for acid GER. The 6 patients had mean of 42.5 (range 20 to 60) acid and non-acid MII episodes. Four of the six patients had minimal acid reflux events. There was a high degree correlation of MII with subsequent coughing events. Three of the five patients had symptoms index (SI) scores of greater then 40% for cough. Three of the four patients with high SI were mostly non-acid reflux events (range 57% to 100% nonacid MII events). Conclusion: Positive tracheal pepsin aspirates seen in these patients support microaspiration as a cause of chronic lung disease. Persistent asthma and MII events are associated temporally with cough. This supports GER and microapiration in association of moderate to severe asthma. Non-acid events in this sample were more commonly associated with symptoms, suggesting previous studies assessing acid GER only may be invalid.

Sequential microbiological monitoring of tracheal aspirates in intubated patients admitted to a pediatric intensive care unit

To evaluate, sequentially, tracheal aspirates from patients admitted to a pediatric intensive care unit and to associate these pathogens with length of hospital stay, previous use of antimicrobial therapy and diagnoses of ventilator-associated pneumonia. The study population consisted of patients admitted to a pediatric intensive care unit, between November 2002 and December 2003, on ventilator support. Three tracheal aspirates were collected serially from each patient. The first tracheal aspirate sample was obtained 6 hours after admission to the intensive care unit and the remaining samples were collected after 48 and 96 hours. One hundred patients aged from one day to 14 years were assessed. Positive tracheal cultures were observed to have increased in the three tracheal aspirate samples collected from each patient for Pseudomonas aeruginosa, from 6 to 22% (p = 0.002), and to have decreased for Staphylococcus aureus, from 23 to 8% (p = 0.009). Isolation of Candida spp increased for the subset that had received previous antimicrobial therapy (p < 0.05). Sixteen (23.5%) out of 68 patients admitted without pneumonia developed ventilator-associated pneumonia. Positive tracheal aspirate cultures were obtained in 10 out of 16 of these patients: six were positive for Staphylococcus aureus (three associated with Acinetobacter baumanii), two for Klebsiella spp (one associated with Enterobacter spp), one for Pseudomonas aeruginosa and one for Candida spp. Sequential evaluation of tracheal aspirates may be useful to track changes in bacterial flora at pediatric intensive care units.

Incidence, Etiology, and Outcome of Nosocomial Pneumonia in ICU Patients Requiring Percutaneous Tracheotomy for Mechanical Ventilation

To determine the epidemiology of pneumonia in patients with tracheotomy receiving short-term mechanical ventilation. Observational prospective study. A 14-bed medical-surgical ICU. Ninety-nine critically ill acute patients requiring percutaneous dilatational tracheotomy for mechanical ventilation. Tracheal aspirate obtained 48 h before tracheotomy. Eighteen patients (18.1%) acquired pneumonia (median of 7 days after tracheotomy). Pseudomonas aeruginosa was the most frequently identified pathogen, found in eight of the episodes (four not documented by prior tracheal colonization), followed by other Gram-negative bacilli. The development of ventilator-associated pneumonia (VAP) was not anticipated by any clinical variable. A positive tracheal aspirate (TA) culture result obtained before tracheotomy was associated with a risk of acquiring pneumonia of 19.7%, whereas sterile TA cultures were associated with a risk of 14.3% (p > 0.20). VAP prolonged ICU stay or the ventilation period for a median of 19 days and 15 days, respectively. Overall mortality was 34.3%, but the presence of VAP did not increase the mortality rate. Percutaneous tracheotomy in patients receiving short-term mechanical ventilation predisposes to pneumonia. Pneumonia was associated with prolonged ventilation and ICU stay, but was not associated with increased mortality. Pseudomonas is a common pathogen after tracheotomy, and this observation should be considered in selecting an antibiotic regimen, because TA obtained prior to the tracheotomy often failed to identify this pathogen.

Pneumonia after cardiac surgery is predictable by tracheal aspirates but cannot be prevented by prolonged antibiotic prophylaxis

Background. The purpose of this study was to assess the value of tracheal aspirate as a predictor of pneumonia after coronary artery bypass grafting and to evaluate the efficacy of prolonged perioperative antibiotic prophylaxis. Methods. Tracheal aspirates of 500 patients undergoing coronary artery bypass grafting were taken immediately after intubation and analyzed for microorganisms by Gram stain and semiquantitative microbiologic cultures. All patients received 2 g ceftriaxone as a single-dose perioperative antibiotic prophylaxis before operation. Results of Gram stains were available before the patients were transferred to the intensive care unit. After the results were known, both groups of patients (positive Gram stain, group 1; negative Gram stain, group 2) were randomly assigned to either conventional antibiotic prophylaxis (A), consisting of ceftriaxone 2 g on postoperative day 1, or prolonged antibiotic prophylaxis (B), with ticarcillin + clavulanic acid 3 × 5.2 g during 72 hours. Results. From 500 patients, 91 had a positive Gram stain whereas 409 had a negative one. The incidence of pneumonia was significantly higher in patients with preoperative positive tracheal aspirates (15.3%) than in patients with a negative one (3.6%; p < 0.01). However, prolonged prophylaxis did not reduce the rate of postoperative pneumonia, which was as high as 13% in untreated positive patients versus 17% in treated positive patients, and 2% in untreated negative patients versus 4% in treated patients. In patients who had pneumonia, there was a high correlation between the microorganisms found in preoperative aspirates and those observed when aspirates were repeated (100% correlation in patients with conventional antibiotic prophylaxis and 87% in those with prolonged prophylaxis). Conclusions. Early postoperative pneumonia (<7 days) is most likely caused by microorganisms that colonize the respiratory tract before operation. The risk of pulmonary infection after coronary artery bypass grafting can be predicted from the preoperative tracheal aspirates. Prolonged perioperative antibiotic prophylaxis has no efficacy in reducing the incidence of pulmonary infections.

Radiological Pulmonary Changes During Gram Negative Bacillary Nosocomial Bloodstream Infection (BSI) In Premature Infants. † 1143

We designed a retrospective study to characterize changes in chest radiographs that occur at the time of Gram negative bacilli (GNB) nosocomial BSI and to determine the radiological findings of neonatal nosocomial pneumonia. Forty-one infants who had BSI (study group) and 50 GNB airway colonized infants who had sepsis workup with negative blood cultures (control group) were studied. We correlated clinical data, 95 blood and 305 tracheal aspirate (TA) cultures, with radiographic findings from the day before, the day of, and the day after blood cultures were taken. Two radiologists independently graded 258 films using a modified score (AJDC, 1984;138:581) for bronchopulmonary dysplasia (BPD) and a semi-quantitative system (probable, possible or unlikely) for pneumonia. Of the study population, 54% were male, 21% black, 89% received surfactant, 79% dexamethasone and 88% survived. Mean birth weight was 1057g and 1044g for the study and control groups, respectively. Average age at the time of blood cultures was 23 days for both groups. Most common isolates from blood and TA were Klebsiella pneumoniae, Enterobacter cloacae, Escherichia coli and Pseudomonas aeruginosa. BSI infants (mainly P.aeruginosa and K.pneumonia) died twice as often as controls. Radiological findings: BPD scores did not change in relation to the day of the blood culture and were similar between study and control groups. Twenty-one BSI patients presented with newly positive TA at the time, or within 24 hours of blood culture. Probable or possible pneumonia was diagnosed in 18 of them. Their BPD scores were higher than those of the remaining BSI patients, of whom 7 were already airway colonized, 9 had negative TA's, and 4 were not intubated. Only one of these 20 patients had a possible pneumonia score. CONCLUSION: Radiographic signs of pneumonia in infants with BPD are of significance only when associated with positive blood culture with a respiratory pathogen. Thus, the CDC definition of nosocomial pneumonia is correct and is further supported by the recovery of the same GNB from the airway of an infant with previously negative tracheal aspirate cultures.

Failure of tracheal aspirate cultures to define the cause of respiratory deteriorations in neonates.

The spectrum of organisms responsible for lower respiratory tract infection in chronically ventilated neonates is poorly defined. During an 18-month period 63 infants with a respiratory deterioration defined as an increase in fractional inspired O2 concentration > or = 20% and/or mean airway pressure > or = 3 cm H2O were evaluated for pulmonary infection. These infants were compared with 58 stable control ventilated infants. Tracheal aspirates for culture and Gram stain were taken from both groups and were cultured for bacteria, viruses, Chlamydia trachomatis, Ureaplasma urealyticum and Mycoplasma hominis. In addition each infant had complete blood counts with differential and chest roentgenograms evaluated. Positive tracheal aspirates defined as a heavy growth of a single or two bacterial organisms, and/or any growth of virus, Chlamydia and U. urealyticum were found in 23 of 63 study patients and 20 of 58 controls (P > 0.05). The most frequent isolate in both groups was U. urealyticum. Chest radiographs were positive (new changes, particularly atelectasis and infiltrates) more frequently in the study group than in controls, but complete blood count and tracheal aspirate Gram-stained smears were not helpful in discerning colonization from infection. We conclude that positive tracheal aspirates occur with equal frequency among infants with a clinical suspicion of lower respiratory tract infection and in "well" controls. Chest roentgenogram may be a useful adjunctive test to discriminate between colonization and lower respiratory tract infection.

111 NEUTROPHIL ELASTASE IN DIAGNOSIS OF NEONATAL INFECTION

Elastase (E) released from neutrophils during phagocytosis is rapidly bound and inactivated by α1-proteinase inhibitor. As previously shown, the complex is a sensitive and rapidly responsive indicator of neonatal sepsis using a time-consuming ELISA method (J. Pediatr. 1986, 108:987). In this 3 center prospective study we measured E with a rapid assay (IMAC-Elastase, Merck; 15 min) and compared it with immature/total neutrophils (I/T) and C-reactive protein (CRP) In infants with suspected infection. Normal IMAC-E values (n=319) were obtained from 125 controls (upper limits; day 0-2, 130 μg/l; day 3-5, 95 μg/l; day 6-28, 65 μg/l). An additional 252 neonates of diverse birth weights and gestational ages were evaluated for infection. Sepsis was proved in 10 and pneumonia (positive tracheal aspirate culture and x-ray) in 23.*Values derived from infected (sepsis/pneumonia) ve. non-infected IMAC-E is a useful adjunct in diagnosing neonatal infection, but combining E with I/T and/or CRP markedly increases PPV.

Letters to the Editor

We agree that a positive tracheal aspirate may represent colonization without infection especially after 12 hours of age or if more than one organism is isolated. Dr Goldman suggests that our observations are merely confirmatory of the study by Harris et at,1 but the experimental designs were in fact quite different. Harris et al1 cultured organisms from the nasal pharynx or tracheal aspirate of only four of 29 patients evaluated before 12 hours of age, but did not state whether these four patients also had evidence of systemic infections.

Value of Tracheal Aspirates Questioned

The extensive study recently reported by Sherman and co-workers attempts to evaluate the use of early tracheal aspiration in diagnosing congenital pneumonia.1 Their findings are of interest and confirm some previous studies and clinical impressions. However, the authors' conclusion that "early direct tracheal aspiration ... appears to be a specific ... procedure for the early diagnosis of congenital pneumonia" does not seem to be supported by the data they present. Specifically, for their conclusion to be valid, a definite correlation of positive tracheal aspirates with presence of pneumonia must be made.