Things We Do For No Reason: Routine Blood Culture Acquisition for Children Hospitalized with Community-Acquired Pneumonia

Since the publication of the 2011 IDSA guidelines, new evidence has revealed a decreasing incidence of bacteremia in pediatric populations.⁵ Moreover, viruses were the most frequently identified pathogens in children hospitalized with CAP in a large study, which were isolated in 66% of patients, whereas typical bacteria (either alone or in combination with a virus) were identified in only 7% of cases.⁶ When blood cultures are obtained for pediatric CAP, the incidence of a true bacterial bloodstream pathogen is 1.4%-7% of patients in the United States in the conjugate vaccine era.^7-11 Given that the practice of obtaining blood cultures varies widely among hospitalized patients and that cultures are often obtained based on perceived severity of presentation,^8,9,12 the true incidence of bacteremia in children with CAP would likely be lower if blood cultures were performed in all patients.

Since the introduction of the first conjugated pneumococcal vaccine, the prevalence of penicillin resistance among pneumococcal isolates dramatically declined,¹³ though with geographic variability.¹⁴ Therefore, when we isolate pneumococcus strains, resistance prevalence requires that we alter treatment much less frequently in the majority of patients with CAP receiving IDSA-recommended ampicillin/amoxicillin.² In a large six-center, geographically dispersed retrospective cohort study, Neuman et al. reported a rate of true bacteremia of 2.53%; 82% of all pathogens and 92% of pneumococcal isolates were susceptible to penicillin. Therefore, the authors estimated that 667 children hospitalized with CAP would need blood cultures to identify one child requiring an antibiotic other than an aminopenicillin.⁹ Staphylococcus aureus was identified only in 1% (23/2,138) of patients in the EPIC cohort; the pathogen was identified via blood culture in only 26% (6/23) of these patients.¹⁵ Therefore, the concern about the possibility of S. aureus may be a common reason for physicians straying from IDSA-recommended therapy, but it is an uncommon cause of CAP and infrequently identified via blood culture.

Blood culture contaminants have been reported to approach the rate of true pathogens in some studies^8,9,11 and be equal or exceed the rates in others.^7,16 While awaiting bacterial speciation, antibiotic coverage is often broadened, even for contaminants,⁸ which can result in unnecessary exposure to nephrotoxic agents such as vancomycin, cause rare adverse events such as Stevens-Johnson syndrome, contribute to antibiotic resistance and unnecessary costs, and increase the length of stay and laboratory utilization.^17-19

Given the low penicillin resistance prevalence among pneumococcal isolates in several parts of the United States, blood cultures should be used to identify patients with nonpneumococcal CAP as these patients are more likely to require antibiotics other than penicillin or aminopenicillin. Children with complicated pneumonia are more likely to have nonpneumococcal etiologies than children with uncomplicated pneumonia.² Moreover, literature published since the IDSA guidelines continues to indicate that the incidence of bacteremia in complicated pneumonia is significantly higher than that in uncomplicated pneumonia (Table). This further supports the IDSA guideline recommendation for blood culture acquisition in children with complicated pneumonia.²