Arch Dis Child: first published as 10.1136/adc.64.1_Spec_No.34 on 1 January 1989. Downloaded from Archives of Disease in Childhood, 1989, 64, 34-38 Routine endotracheal cultures for the prediction of sepsis in ventilated babies T A SLAGLE, E M BIFANO, J W WOLF, AND S J GROSS Department of Pediatrics, Health Science Center at Syracuse, New York, USA SUMMARY Serial cultures of endotracheal tube aspirates were carried out in 94 neonates who were intubated and had been ventilated for longer than one week. A similar change in bacterial colonisation with duration of ventilation was seen in infants who subsequently developed sepsis and those who did not. In both groups, 177 aspirates (more than 90%) obtained during the first week of ventilation were sterile. Thereafter, colonisation with mixed Gram positive flora emerged followed by growth of Gram negative bacilli. For the infants who developed sepsis, the correlation between pathogens isolated from blood during the episodes of sepsis and those from previous endotracheal tube isolates was poor; in only five of the 26 cases of sepsis (19%) was the same single strain of organism isolated from culture of the blood and of the endotracheal tube aspirate. Other markers of infection such as endotracheal tube aspirate white blood cell counts and changes in bacterial flora were not useful in predicting systemic infection. Routine surveillance cultures of endotracheal tube aspirates in ventilated infants are not helpful in by copyright. predicting the pathogens that are isolated from the blood during episodes of sepsis. Hospital acquired infection is an important cause of Patients and methods mortality and morbidity among infants in neonatal intensive care units. Surveillance cultures are per- The study population was selected from the 657 formed routinely in many units to monitor infants at neonates born between 1 January 1985 and risk of sepsis.1 ' For example, cultures of aspirates 31 December 1985 who were admitted to the obtained through endotracheal tubes from ventilated neonatal intensive care unit at Crouse Irving infants are monitored on the assumption that the Memorial Hospital. Ninety four of the 657 neonates http://adc.bmj.com/ organisms that are colonising the respiratory tract (14%) required endotracheal intubation and will be the same pathogens as those isolated from mechanical ventilation for longer than one week and the blood during episodes of sepsis. Support for this were included in the study. Tracheal aspirates were practice comes from studies showing that in infants collected through endotracheal tubes into DeLee who develop sepsis at birth, the same bacterial traps under sterile conditions every three days for as pathogens can be recovered from cultures of blood long as infants remained ventilated.6 A Gram stain and endotracheal tube aspirates.Y5 The value of was performed on all aspirates for the identification serial cultures of endotracheal tube aspirates, of bacteria and measurement of the white blood cell on September 26, 2021 by guest. Protected however, in determining the aetiology of sepsis in count. White cells were counted from 20 high power infants who remain intubated for longer periods of fields and the average taken. All aspirates were time has not been proved. Furthermore, the pattern plated immediately onto blood, chocolate, and of organisms colonising the endotracheal tube in MacConkey agars. Plates were examined daily and ventilated infants after the first week of life has not organisms identified by routine laboratory tech- been elucidated. niques.7 8 Antibiotic sensitivity testing was done on This study was designed to define the pattern of all Gram negative bacilli and coagulase positive respiratory tract colonisation in neonates intubated staphylococci that were isolated. Infants suspected and ventilated for longer than one week and to of having a septic focus on the basis of clinical assess the value of serial cultures of endotracheal findings had blood from at least one percutaneous tube aspirates in predicting pathogens isolated puncture site inoculated into tryptic soy broth. during episodes of sepsis. Antibiotic sensitivity testing was done on all 34 Arch Dis Child: first published as 10.1136/adc.64.1_Spec_No.34 on 1 January 1989. Downloaded from Routine endotracheal cultures for the prediction of sepsis in ventilated babies 35 organisms isolated from blood cultures. Over the reason for ventilation was respiratory distress syn- year of study, all infants requiring ventilation drome, which occurred in 63 (67%) of the infants. received antibiotics for the first three days of life. During the study period 26 episodes of sepsis Thereafter, antibiotics were given only during occurred in 22 of the ventilated infants. These 22 episodes of suspected or proved sepsis. infants with sepsis differed from the remaining 72 The pattern of respiratory tract colonisation over ventilated infants who never developed sepsis in that time in infants who developed sepsis was compared they weighed less at birth (926 (116) compared with with that of infants who did not. Additionally, for 1410 (118) g, p<0-01), were of lower gestational infants who developed sepsis, correlation between age (27.5 (0.7) compared with 29-6 (0.6) weeks, blood pathogens and isolates obtained from endo- p < 0.05), and required mechanical ventilation for a tracheal tubes during the week before the episode of longer period of time (83 (15) compared with 36 (4) sepsis was examined. The following definitions were days, p<0.001). The mean (SEM) age of infants used: full agreement when the organism strain when bacteraemia was diagnosed was 41 (7) days, isolated from blood matched the only isolate from range 8-130. the endotracheal tube; partial agreement when the A total of 1448 cultures of endotracheal tube organism strain isolated from the blood matched aspirates were done on the entire group of 94 one of several isolates from the endotracheal tube; infants; 395 (27%) grew no organisms, 410 (28%) and no agreement when the organism found in the grew mixed Gram positive flora (including coagulase blood did not match any of those isolated from the negative staphylococci, a haemolytic streptococci, endotracheal tube. and diphtheroids) and the remaining 643 cultures Differences in the characteristics between infants (45%) grew one or more Gram negative bacilli, with and without sepsis were evaluated by the two coagulase positive staphylococci, or other pathogens. tailed Student's t test. Differences in the Gram stain Bacterial colonisation of endotracheal tube white cell response were compared by Fisher's exact aspirates changed similarly with the duration of probability test. All values are expressed as mean ventilation in infants who developed sepsis and in by copyright. (SEM). those who did not (fig 1). In both groups of infants, more than 90% of the aspirates (177) obtained Results during the first week of ventilation were sterile. Between the second and fourth weeks of ventilation, The study group comprised 54 boys and 40 girls who respiratory colonisation with mixed Gram positive required endotracheal intubation and mechanical flora developed, and after four weeks of ventilation ventilation for a mean of 47 (5) days (range 8 to Gram negative bacilli predominated. Klebsiella 276). All but three infants were intubated and pneumoniae, Pseudomonas species, Enterobacter ventilated on the first day of life. The most common species, and Escherichia coli were not isolated http://adc.bmj.com/ Infants without sepsis Infants with sepsis 143 148 183 217 177 Noof infants 39 53 98 149 265 I:__FI O No growth so - * Mixed Gram positive n flora El Coagulase positive on September 26, 2021 by guest. Protected 60s- staphylococcus 0 * Mixed Gram negative 0 bacilli a) 40 - 0. o Other 20ol 1:.......... 0' ......... 1 2 3-4 5-8 9-20 1 Weeks of ventilation Fig 1 Developmentalpattern ofbacterial colonisation ofendotracheal tube aspirates in infants with and withoutsepsis. Arch Dis Child: first published as 10.1136/adc.64.1_Spec_No.34 on 1 January 1989. Downloaded from 36 Slagle, Bifano, Wolf, and Gross during the first week of ventilation but accounted obtained during the week before the onset of clinical for 138 (almost 40%) of all isolates obtained during infection (fig 2). In 14 of the 26 cases of sepsis the second month of ventilation and 316 (over 70%) (54%), the strain of organism isolated from blood of all isolates obtained after two months of ventila- was not found in the endotracheal tube aspirate. tion. These cases of 'no agreement' included five instances In the infants with sepsis, pathogens isolated from in which the previous endotracheal tube aspirates blood were compared with endotracheal tube isolates had been sterile and nine instances in which U No agreement between isolates from blood and endotracheal tube Outer ring= Isolates from endotracheal tube {4/ Partial agreement between isolates from Inner ring = Isolates from blood blood and endotracheal tube ff N Full agreement between isolates from blood and endotracheal tube by copyright. http://adc.bmj.com/ on September 26, 2021 by guest. Protected Fig2 Agreementbetween bloodpathogens isolatedduringepisodesofsepsisand bacteria isolatedfrom endotrachealtube aspirates duringtheprevious week. Arch Dis Child: first published as 10.1136/adc.64.1_Spec_No.34 on 1 January 1989. Downloaded from Routine endotracheal cultures for the prediction of sepsis in ventilated babies 37 different organisms were isolated from the endo- tracheal intubation and mechanical ventilation. Of tracheal tube aspirates. In seven of the 26 cases of the endotracheal tube aspirate cultures obtained sepsis (27%), the organism in the blood was found from infants during the first seven days of ventila- as one of multiple isolates from the endotracheal tion, 90% were sterile. The lack of organisms was tube (partial agreement). Finally, in only five cases probably the result of administration of antibiotics of sepsis (19%) was the same single strain of to all infants during the first three days of life. Harris organism isolated from both blood and endotracheal et al3 found a significant decrease in respiratory tube aspirate cultures (full agreement).