Prevalence of Bacteremia in Pediatric Patients With CAP
Prevalence of Bacteremia in Pediatric Patients With CAP
We determined the prevalence of bacteremia in children hospitalized with CAP across 4 children's hospitals in the conjugate vaccine era. Blood cultures were obtained in only slightly more than half of the study population. Bacteremia was identified in 3.9% overall, and 7.1% of those who had a blood culture obtained, which is higher than previously reported from single-center studies of children in the hospital and outpatient settings. Pneumococcus was the predominant pathogen identified in this study, consistent with previous studies in both the pre- and postvaccine eras. Pleural fluid examination identified an additional 6 organisms that were not found on blood culture, increasing the yield to 8.7% in patients who had a blood culture obtained.
While the prevalence of bacteremia was low overall, it was higher in children with a longer duration of fever, elevated C-reactive protein, complicated pneumonia and metastatic complications, adding data to the current evidence that patients with moderate-to-severe disease are more likely to have a positive blood culture than children with mild disease and have the potential to benefit from pathogen-directed therapy. In addition, there were 6 (23.1%) patients with bacteremia whose pneumonia was uncomplicated at admission that evolved to become complicated over time. This highlights the difficulty in determining risk of bacteremia in the patient who appears to have a simple pneumonia at admission. Interestingly, only 1 of these patients had the pathogen identified on pleural fluid. This finding underscores the importance of obtaining a blood culture at admission, as these patients were initially classified as uncomplicated. If blood cultures were only directed at those with complicated pneumonia at presentation, the causative pathogen for 5 of these patients would have been missed.
Contamination rates were low across institutions with a mean of 2% (range: 1–3.8%), which is consistent with other studies that have examined the contamination rates in outpatient settings. Herz et al reported a blood culture contamination rate of 1.8% in their study evaluating the prevalence of bacteremia before and after the pneumococcal vaccine era using a large outpatient database. Conversely, contamination rates have been reported to be as high as 8%, making a false-positive result more likely than a true positive result in some studies.However, in this study, the positive blood culture rate was higher than the contamination rate in those who had a blood culture obtained.
One-quarter of patients for whom a pathogen was identified and susceptibility results were available had a change in management, with narrowing of antibiotic therapy at hospital discharge. While these changes were typically made to target therapy based on the culture result, 1 of these could have been narrowed even further. Furthermore, an additional 10 patients could have safely been narrowed by either decreasing the number of agents used (eg, case 2: clindamycin alone instead of clindamycin plus a third-generation cephalosporin for methicillin-resistant Staphylococcus aureus) or by using the most narrow agent available (eg, case 5: amoxicillin instead of amoxicillin-clavulanate for a susceptible pneumococcus). These findings provide information regarding optimal narrowing and further opportunities to narrow therapy for patients with bacteremia in the inpatient setting. While previous work has suggested that positive blood culture results have had little or no impact on clinical management due to few positive cultures, these studies were performed in the emergency department or outpatient setting, and as such may not be easily generalized to the inpatient population.
Variability in patient management was noted across hospitals in percentage of patients with a blood culture obtained, method of antibiotic delivery and antibiotic spectrum at hospital discharge. These findings are consistent with other studies that have found significant variation among practitioners and across sites. This highlights not only the importance of national guideline development but also the value of monitoring guideline adherence.
There are several limitations to this study. First, the data are retrospective and subject to availability in the medical record. Second, it is possible that the prevalence of bacteremia was overestimated because culture collection was at the discretion of the provider and may have been preferentially obtained in patients who were more ill at presentation, and thus more likely to have bacteremia. The reasons for blood cultures being obtained in slightly over half of the population are unclear, but may be related to more ill appearance, or in some cases pretreatment with antibiotics and a common thought process that bacteremia is unlikely in the pretreatment setting. Third, decisions regarding appropriateness of blood culture–directed changes in management were based solely on spectrum of antibiotic coverage relative to S. pneumoniae and Staphylococcus aureus, thus excluding a determination of broadening or narrowing of anaerobic (eg, clindamycin) or Gram-negative coverage (eg, ceftriaxone) in that context. However, as nearly all pathogens were identified as either S. pneumoniae or Staphylococcus aureus, decisions about the coverage provided against other pathogens are less relevant. Finally, the data from this study were obtained from large children's hospitals that provide tertiary care, and as such may not be able to be generalized to smaller community-based hospitals.
Discussion
We determined the prevalence of bacteremia in children hospitalized with CAP across 4 children's hospitals in the conjugate vaccine era. Blood cultures were obtained in only slightly more than half of the study population. Bacteremia was identified in 3.9% overall, and 7.1% of those who had a blood culture obtained, which is higher than previously reported from single-center studies of children in the hospital and outpatient settings. Pneumococcus was the predominant pathogen identified in this study, consistent with previous studies in both the pre- and postvaccine eras. Pleural fluid examination identified an additional 6 organisms that were not found on blood culture, increasing the yield to 8.7% in patients who had a blood culture obtained.
While the prevalence of bacteremia was low overall, it was higher in children with a longer duration of fever, elevated C-reactive protein, complicated pneumonia and metastatic complications, adding data to the current evidence that patients with moderate-to-severe disease are more likely to have a positive blood culture than children with mild disease and have the potential to benefit from pathogen-directed therapy. In addition, there were 6 (23.1%) patients with bacteremia whose pneumonia was uncomplicated at admission that evolved to become complicated over time. This highlights the difficulty in determining risk of bacteremia in the patient who appears to have a simple pneumonia at admission. Interestingly, only 1 of these patients had the pathogen identified on pleural fluid. This finding underscores the importance of obtaining a blood culture at admission, as these patients were initially classified as uncomplicated. If blood cultures were only directed at those with complicated pneumonia at presentation, the causative pathogen for 5 of these patients would have been missed.
Contamination rates were low across institutions with a mean of 2% (range: 1–3.8%), which is consistent with other studies that have examined the contamination rates in outpatient settings. Herz et al reported a blood culture contamination rate of 1.8% in their study evaluating the prevalence of bacteremia before and after the pneumococcal vaccine era using a large outpatient database. Conversely, contamination rates have been reported to be as high as 8%, making a false-positive result more likely than a true positive result in some studies.However, in this study, the positive blood culture rate was higher than the contamination rate in those who had a blood culture obtained.
One-quarter of patients for whom a pathogen was identified and susceptibility results were available had a change in management, with narrowing of antibiotic therapy at hospital discharge. While these changes were typically made to target therapy based on the culture result, 1 of these could have been narrowed even further. Furthermore, an additional 10 patients could have safely been narrowed by either decreasing the number of agents used (eg, case 2: clindamycin alone instead of clindamycin plus a third-generation cephalosporin for methicillin-resistant Staphylococcus aureus) or by using the most narrow agent available (eg, case 5: amoxicillin instead of amoxicillin-clavulanate for a susceptible pneumococcus). These findings provide information regarding optimal narrowing and further opportunities to narrow therapy for patients with bacteremia in the inpatient setting. While previous work has suggested that positive blood culture results have had little or no impact on clinical management due to few positive cultures, these studies were performed in the emergency department or outpatient setting, and as such may not be easily generalized to the inpatient population.
Variability in patient management was noted across hospitals in percentage of patients with a blood culture obtained, method of antibiotic delivery and antibiotic spectrum at hospital discharge. These findings are consistent with other studies that have found significant variation among practitioners and across sites. This highlights not only the importance of national guideline development but also the value of monitoring guideline adherence.
There are several limitations to this study. First, the data are retrospective and subject to availability in the medical record. Second, it is possible that the prevalence of bacteremia was overestimated because culture collection was at the discretion of the provider and may have been preferentially obtained in patients who were more ill at presentation, and thus more likely to have bacteremia. The reasons for blood cultures being obtained in slightly over half of the population are unclear, but may be related to more ill appearance, or in some cases pretreatment with antibiotics and a common thought process that bacteremia is unlikely in the pretreatment setting. Third, decisions regarding appropriateness of blood culture–directed changes in management were based solely on spectrum of antibiotic coverage relative to S. pneumoniae and Staphylococcus aureus, thus excluding a determination of broadening or narrowing of anaerobic (eg, clindamycin) or Gram-negative coverage (eg, ceftriaxone) in that context. However, as nearly all pathogens were identified as either S. pneumoniae or Staphylococcus aureus, decisions about the coverage provided against other pathogens are less relevant. Finally, the data from this study were obtained from large children's hospitals that provide tertiary care, and as such may not be able to be generalized to smaller community-based hospitals.