Our retrospective analysis of pediatric BSIs caused by ESBL-producing E. coli and K. pneumoniae with a 30-day mortality of 17% suggested that administration of non-carbapenem antibiotics as an initial empirical antibiotic was not a significant risk factor for 30-day mortality or microbiological failure at day 2 if early transition to a definitive carbapenem regimen was possible when susceptibility was proven. Being a preterm infant was the only significant risk factor for 30-day all-cause mortality of BSIs caused by ESBL-producing E. coli and K. pneumoniae in this study.
Based on the data from our institute from 2009 to 2018, the resistance rates of E. coli and K. pneumoniae to 3rd and/or 4th generation CSs were as high as 40–50%, and their resistance rates to piperacillin/tazobactam were approximately £20% (9, 21). If the antimicrobial resistance rate to a certain antibiotic in a hospital or community is higher than 10–20%, clinicians should consider using a different antibiotic or combination therapy as an empirical regimen (22-24). Considering the high ESBL-positive rate of Enterobacteriaceae at our institution, if the strain is reported as a Gram-negative strain in the blood culture reporting system, the treatment is first changed to a carbapenem; then, de-escalation is performed if necessary. In cases of septic shock, carbapenems tend to be used as empirical antibiotics. In suspected CNS infections, meropenem is the empirical choice of antibiotic to achieve CNS penetration because the usual doses of tazobactam have been considered to be insufficient for appropriate treatment of CNS infections (25), although fewConsidering the high ESBL-positive rate of Gram-negative strains at this medical institution, if the G(-) strain is reported to the blood culture notification system, the antibiotic susceptibility result of the strain is reported and the treatment is changed to carbapenem. In the present medical gram Considering that the high prevalence of ESBL negative strains blood culture system reported in the G (-) when the reported isolates and treatment to become a cover antibiotic susceptibility results of isolates reported changes penem. Although studies have reported the successful treatment of patients with CNS infections with piperacillin/tazobactam (26). So, carbapenems could be easily used as the initial regimen, especially in high-risk patients. However, considering the positive correlation between antibiotic burden and antibiotic resistance (27-29), administration of broad-spectrum antibiotics should be considered carefully.
Carbapenems have been considered the best choice for definitive therapy in serious infections caused by ESBL producers (30). However, there is controversy regarding appropriate initial empirical antibiotics in both pediatric and adult patients infected with ESBL producers. Inappropriate initial empirical antibiotic treatment has been associated with increased mortality in patients with bacteremia caused by ESBL-producing Enterobacteriaceae (31, 32). In contrast, one multicenter study including approximately 10% of pediatric patients aged <18 years suggested that inappropriate empirical therapy within <24 hours was not associated with increased mortality (33). Our single center study suggested that there is no significant advantage in choosing a carbapenem as an initial antimicrobial agent in terms of the microbiological failure rate by day 2 and 30-day mortality. However, this could not be applied in general. The microbiological laboratory of our institute operates the blood culture system 24 hours a day, year-round; when an automatic signal is reported from the BACTEC blood culture system, laboratory personnel perform Gram staining and report the results to an electronic medical record in real time. Therefore, in the case of Gram-negative bacteria isolated from a blood culture, it usually takes less than 24 hours to report the automatic positive signal with the Gram-staining result for a corresponding one. Therefore, most patients with BSIs caused by ESBL-producing Enterobacteriaceae treated with non-carbapenems as initial empirical antibiotics can be switched to a carbapenem as the definitive therapy within two calendar days, if necessary; furthermore, more than half of them can be switched within one calendar day. These conditions might explain why non-carbapenems as empirical antibiotics were not associated with an increased mortality rate or microbiological failure rate in our study.
A recent case-control study including 110 pediatric patients showed that neonates were more likely than older children to develop bacteremia caused by ESBL producers (6). Moreover, one study about risk factors for infection with ESBL-producing Enterobacteriaceae during an outbreak in a neonatal ICU (NICU) found that infections with ESBL producers were associated with prematurity (34). During our study period, an outbreak of ESBL-producing K. pneumoniae bacteremia among extremely low birth weight infants in the NICU resulted in four fatal cases associated with necrotizing enterocolitis (NEC) that were all initially treated with carbapenems and died within 2 days. Furthermore, two more fatal cases were observed in preterm infants as sporadic cases. Considering the high prevalence of bacteremia caused by ESBL-producing Enterobacteriaceae and high fatality rates regardless of types of empirical antibiotics in neonates (8, 35-38), delicate care and appropriate management for premature infants infected with ESBL producers are necessary to minimize morbidity and mortality.
There are limitations in assessing the causal relationship of some phenomena because this was a retrospective observational study. The more severe the initial symptoms and signs were, the more likely the physician was to administer carbapenems from the beginning, especially for premature infants with septic shock. Most of the fatal cases in this study were associated with premature infants. Even though we performed a multivariate logistic analysis to adjust for possible confounding factors, the sample size is just too small to draw definite conclusions about the effect of empirical antibiotic on microbiological failure or mortality while taking into account other risk factors. Furthermore, it was not possible to analyze the statistical difference between the 30-day mortality according to the appropriateness of empirical antibiotics used in the non-carbapenem group. However, no fatal cases were observed among patients who received appropriate empirical non-carbapenem antibiotics. In addition, we did not identify virulent factors, antibiotic resistance mechanism including specific ESBL genes, and host immune responses, which could be an important way to explain the outcomes of the ESBL producing G(-) bacteremic patients (39), because our study was a retrospective study, and PCR test for ESBL genes was not routinely performed at our institute. Although our result cannot be extrapolated to the general pediatric population, these findings suggest that it is not always necessary to select a carbapenem as an initial empirical antibiotic for ESBL-producing E. coli and K. pneumoniae bacteremia in children if the appropriate antibiotics can be administered without delay with the support of a culture reporting system. Laboratory-based antimicrobial resistance surveillance systems can incorporate epidemiological data in determining appropriate empirical antibiotics in high endemic setting while balancing between selecting appropriate empirical antibiotics and minimizing antibiotic pressure.
In conclusion, if early transition to carbapenems as a definitive antimicrobial therapy is possible, empirical use of non-carbapenems may be considered an appropriate option in pediatric bacteremia caused by ESBL-producing E. coli and K. pneumoniae. A large multicenter study should be conducted to identify appropriate carbapenem-sparing options for medically fragile pediatric patients and to minimize the spread of MDR pathogens such as carbapenem-resistant bacteria.