Introduction

Bloodstream Infections (BSI) are among the seven leading causes of death in Europe [1], and those caused by carbapenemresistant enterobacteria in children are increasingly prevalent, with poor clinical outcomes [2]. In the United States, between one-third of carbapenem-resistant enterobacteria isolates in adult patients are carbapenemase producers, and the class A serine carbapenemase of Ambler K. pneumoniae Carbapenemase (KPC) accounts for more than 90% of these [2].

The spread of carbapenem-resistant enterobacteria has been a global public health threat. Carbapenems have been used conventionally in the hospital setting to treat infections caused by β-lactamase-producing Escherichia coli and Klebsiella pneumoniae, and to date are considered to be antibiotics of last resort [3].

Data from China Antimicrobial Surveillance Network show resistance rate of K. pneumoniae to meropenem and imipenem increase from 2.9 to 3.0% in 2005 and 26.3 and 25% in 2018, respectively. While in Europe, carbapenem-resistant K. pneumoniae are most common in Mediterranean and Balkan countries, with a prevalence of 60% in Greece and 40% in Italy [4].

The mortality rate of Health Care Related Infections (HAI) caused by carbapenem-resistant enterobacteria, specifically K. pneumoniae, ranges from 30% to 50%, with BSI being the most important infection, with a high risk of mortality [5]. In Brazil, this pathogen has become endemic in some regions of the country [2,6].

According to the Brazilian SCOPE study, 58.5% of BSI were caused by a Gram-negative. The overall mortality rate was 40% in patients with BSI, 49% of BSI occurred in patients admitted to Intensive Care and 5% had a polymicrobial origin (isolated more than one microorganism in the blood culture) [7,8]. Also in that same cohort, the 2013 data showed a total of 2,563 cases of BSI reported by the hospitals included in the study, of which 342 episodes of BSI in pediatric patients (≤16 years of age), 45% of which occurred in Pediatric and Intensive Care and 96% of BSI were monomicrobial and mortality was 21.6% [8].

The International Nosocomial Infection Control Consortium (INICC) [9] cohort, which includes 43 developing countries, reported a mortality rate of 17%. Klebsiella pneumoniae and Acinetobacter spp isolates ranked third and fourth, respectively, among the main agents isolated as cause of healthcare-associated infection in Brazil [7].

The National Program for Prevention and Control of HealthRelated Infections described in its report that among the resistant Gram-negative bacilli that have been reported most frequently as etiologic agents of primary bloodstream infections associated with central venous catheters (IPCSL) in patients hospitalized in pediatric PICUs are: Klebsiella pneumoniae carbapenem-resistant to third and fourth generation cephalosporins and carbapenems. These data lead us to the need to know the prognostic factors of patients with positive blood cultures for bloodstream infection by KPC during hospitalization, and thus contribute to decisionmaking aimed at prevention and better prognosis of these patients.

Therefore, this study sought to identify the prognostic factors of patients who had presented laboratory-defined KPC bloodstream infection during hospitalization in the Pediatric Intensive Care Unit of a high-complexity Brazilian hospital between 2013 and 2018.

Methods

Historical cohort study with children hospitalized in the Pediatric Intensive Care Unit of a high-complexity university hospital, who were diagnosed with Klebsiella pneumoniae carbapenemase bloodstream infection confirmed in the laboratory. The institution has 226 beds, including 20 PICU-specific beds, between 2013 and 2018.

Data collection

The following variables were collected:

Outcome: positive blood cultures for Klebsiella pneumoniae carbapenemase, laboratory confirmed, after 48 hours in the PICU, at discharge or on the day of death.

Demographic data: age, weight, color, gender

Clinical characteristics: PELOD-2 score, length of stay in PICU, exposure to broad spectrum antibiotics, PICU admission, invasive devices, solid organ transplantation, parenteral nutrition, combined therapy.

Definitions

Bloodstream Infection (BSI) results from blood cultures (HMC) positive for Klebsiella pneumoniae carbapenemase laboratory confirmed and identified by the service’s Hospital Infection Control Subcommittee (SCIH) according to the diagnostic criteria of the National Agency for Sanitary Surveillance (ANVISA) [10] and Centers for Disease Control and Prevention/ National Healthcare Safety Network (CDC/NHSN) [11,12] described below:

Primary catheter-associated bloodstream infection should be considered only if the patient has been using a central catheter for a period longer than two calendar days (with D1 being the day the device was installed) and that on the date of infection the patient was either wearing the device or the device was removed the day before.

All microbiological tests were performed according to the guidelines established by the Clinical and Laboratory Standards Institute [13].

Exposure to broad-spectrum antibiotics before infection: patients who had received a broad-spectrum antimicrobial (vancomycin, meropenem, piperacillin and tazobactam, linezolid, fluconazole, ceftriaxone, cefepime, ciprofloxacin, levofloxacin) up to 60 days before infection.

Combined therapy: patients who received two or more

antimicrobials in the same period with activity against the bacteria;

Death: the frequency of deaths occurring within 30 days after diagnosis of infection was verified;

Colonization: patients who had Klebsiella pneumoniae carbapenemase isolated in the rectal swab, urine and/or tracheal secretions when admitted to the unit, but without any clinical expression or detection of an immune response in patients, when this was isolated;

Early therapy: Administration of the prescribed therapy up to 24 hours before the blood culture and sensitivity results of the antibiogram.

Previous admission to the PICU: because there is no consensus in the literature about previous hospitalization, this study considered patients who had been admitted to the PICU up to 120 days before the infection;

Invasive devices: Indwelling urinary catheter, invasive blood pressure, orotracheal cannula, drains, tracheostomy tube, gastrostomy tube, central venous catheter.

Date of infection: is the date when the first element (sign, symptom, or imaging or laboratory test results) used to define IPCSL occurred within the 7-day infection window period;

Infection window period: period of 7 days during which all elements (signs, symptoms, results of imaging and/or laboratory tests) necessary to define the infection are identified. To identify the IPCSL window period, three days before and three days after the date of the first positive blood culture should be considered;

Time frame for repeat infections: For IPCSL, a patient cannot have more than one event reported within a 14-day period.

The time limit for repeat infections applies only to a single admission to the health facility. This time limit does not extend to different hospitalizations, even if they are in the same institution.

Patient’s discharge from the PICU was defined by the physician based on clinical improvement and laboratory test results.

To assess the severity of cases of organ dysfunction syndrome, we used the Pediatric Logistic Organ Dysfunction score (PELOD-2) [14], which includes ten variables corresponding to five organ systems and determines the severity of multiple organ dysfunction syndrome in the PICU on a scale to be continued. This tool is divided into four subsections and the scoring considers the cardiovascular, neurological, respiratory, hematological and renal systems. Based on the score for each system, a dysfunction score is assigned, and a mortality rate is estimated.

The comorbidities considered were those of primary character and liver disease was defined based on the criteria of the King’s College and Pediatric Acute Liver Failure Study Group, which included: biochemical evidence of acute liver failure (increased transaminases and bilirubins associated with hepatic coagulopathy (INR>1,5 or PT >15 seconds compared to control, no response to vitamin K administration, in a patient with hepatic encephalopathy) [15,16].

Data Analysis

Categorical variables were presented by absolute and relative frequencies. Quantitative variables were calculated, including mean, median, standard deviation and minimum and maximum values. Association between categorical variables was accomplished by Pearson’s chi-square test or Fisher’s exact test.

Comparison between quantitative variables between groups was obtained by the Mann-Whitney test, following a data normality test. Univariate and multiple logistic regression was used to calculate the odds ratio (OR), as well as the 95% confidence interval (95% CI) of the association measure. To analyze survival, we evaluated the period between infection and death, and used the Kaplan-Meier survival curve and survival probabilities at specific dates (7, 14, 21 and 28 days). The significance level was set at 5% for all statistical tests. All analyzes were carried out using a statistical software (SPSS 18 for Windows).

Results

During the period of data collection, 2.696 patients were admitted to the PICU, 92 patients had bloodstream infection (BSI) by different microorganisms, and only 34 of these BSIs were laboratory-confirmed Klebsiella pneumoniae carbapenemase isolates, as shown in Figure 1.

Most patients were male (58.8%), infants (52.9%), 35.3% were malnourished, all had chronic underlying diseases and had hospitalization up to 6 months prior to admission to the PICU before infection. Hepatopathies were the most frequent underlying disease (47.1%). The median age was 22 months (2-208) and the median weight was 9 kg (3-50).

The clinical characteristics showed that 31 (91.2%) of the patients had central venous access, 21 (67.7%) located in the internal jugular vein, and 30 (88.2%) received combined antimicrobial therapy. In 24(70.6%) antibiotic therapy was prescribed and administered within 48h before the HMC result was released by the laboratory. 41,2% of patients had isolated KPC in other sites such as ascitic fluid, urine and tracheal secretion and 9 (26.5%) of patients were colonized (had the bacteria identified in rectal swab research). Also, mechanical ventilation was used in 23 (67.6%) of the patients, indwelling urinary catheter in 18 (52.9%), and hemodiafiltration in 14 (41.2%).

Antimicrobial resistance profile according to antibiogram and treatment

We observed a significant predominance of beta-lactams and carbapenems resistance. Colistin was the most sensitive antibiotic, followed by tigecycline and aminoglycosides (Table 1):

The minimum inhibitory concentration (MIC) of Meropenem was ≥16 μg/ml (33/34, 97%) and 1/34 (3%) was intermediate for merepenem MIC (MIC, 8 μg/ml); Imipenem ≥16 μg/ml (34/34, 100%) and Ertapenem ≥8 μg/ml (34/34, 100%).

Demographic and clinical factors were evaluated in association to the death occurrence in this group of children and adolescents (n = 23). Table 2 shows the variables distributions according to the patient’s vital status (discharge or death), revealing that parenteral nutrition (p=0.038), in addition to PELOD-2 scores on the day of infection (p=0.005), PELOD-2 scores 48 hours after infection were statistically significant regarding the patients’ prognostic (survivors x non-survivors).

The HMC negative control after starting antibiotic therapy was unavailable in 23/16 (69.6%) died patients at the time of death, and the median time between positive blood culture (BSIs) and the death event was 1,5 (0 -14) days. The median time to treat the infection in this group of patients was 6 (4-57) days.

To determine the risk factors associated with mortality, the Odds Ratio (OR) and its respective 95% confidence interval were calculated, using logistic regression for the variables that presented statistical significance in the univariate analysis: PELOD-2 on the day of infection, PELOD-2 48h after infection and PELOD-2 in the occurrence of death or discharge. An increase of one unit in the PELOD-2 score on the day of the diagnostic of infection increased the risk of death by 56% and in the score 48 hours after infection, by 64%, as shown in Table 3.

Survival Analysis

The time between hospitalization and death in children with carbapenem-resistant Klebsiella pneumoniae infection was analyzed in the survival curve, according to the follow-up period (7, 14, 21 and 28 days) as showed in Figure 2.

Discussion

Increased microbial resistance by enterobacteria is considered a global and public health problem, associated with little research on KPC bloodstream infection in critically ill children.

Knowing evidence-based interventions can contribute to reduce the risk of KPC ICS and is fundamental for improving care for critically ill patients, as this bacteria has a high power of dissemination [17].

The profile of patients who had positive blood cultures for Klebsiella pneumoniae carbapenemase during hospitalization in the PICU is similar to that described in other publications conducted in hospitals with tertiary care level, showing patients with chronic underlying disease, predominance of males, infants, malnourished with comorbidities, in addition to previous hospitalization [17-19].

The mortality rate in the present series was 23/34 (67.6%) being higher when compared to other similar studies, however it was influenced by several factors such as: presence of various comorbidities, invasive devices, high number of surgical procedures with solid organ transplants and number of organic dysfunctions after infection [5-7,25,29].

In a systematic review6 with 51 studies to estimate the evolution of patients infected with KPC, overall mortality was 41.0% (95% CI 37.0-44.0) and significant differences were found in the analysis of subgroup by countries being higher in Brazil, with mortality of 51.0% (95%CI 43.0-60.0). In addition, Brazil was also the country with the lowest number of studies in critically ill patients, and no study evaluated a specific type of infection and factors that could increase the risk of mortality in patients [6].

In another study [5] with 4,701 patients, the mortality of patients with bloodstream infection (BSI) was 54.30%, and 48.9% of them were admitted to an Intensive Care Unit (ICU) or underwent solid organ transplantation (SOT). The mortality rate in patients with carbapenem-resistant K. pneumoniae infection was 42.14% versus K. pneumoniae susceptible to carbapenem 21.2%.

Although 16/23 (69.6%) of the patients who progressed to death still did not have negative control blood culture, even so due to the large number of comorbidities that patients had, it is not possible to directly relate deaths only to blood cell infection by KPC.

In the present study, the PELOD-2 score was significantly higher in the patients who did not survived. The most present dysfunctions were respiratory, hematological and renal, and explained, respectively, 56% and 64% of the variation in relation to mortality risk, besides the fact that 67.6% of the patients presented two to three dysfunctions from the date of infection. The presence of new organ dysfunctions during the PICU stay is associated with an increased risk of mortality [14].

Regarding the use of combination therapy, the literature shows results of studies with the adult population with blood bloodstream infections by KPC and found benefit of related mortality with combined antimicrobial therapy, in particular, with combinations containing carbapenem [20]. In contrast to other studies [21,22] have suggested that this benefit is limited to patients at higher risk of mortality (including patients with septic shock, fatal underlying diseases and bacteremia from non-urinary/ non-biliary sources) specifically, for combinations containing carbapenem, for isolates with carbapenem MICs ≤8 μg/mL, a result that is in line with the findings of the present study.

The literature [1] shows that several mechanisms of resistance to carbapenem in vitro result in varyingly elevated meropenem CIMs, it is already known that meropenem plays an important role in the treatment of resistant enterobacteria infections in clinical scenarios where meropenem CIMs are ≤2 μg /mL.

Bacterial death from carbapenems depends on the drug’s free time above MIC, considered an optimal effect if the time above MIC exceeds 40% [1]. Pharmacokinetic data in pediatrics showed that, in healthy children, a prolonged infusion of meropenem for more than 3 hours can reach this goal for isolates with meropenem CIMs until 8 µg/mL [23]. However, in critically ill children, target serum concentrations are reliably achieved only for isolates with meropenem CIMs ≤2 μg/mL due to changes in the expected distribution volumes with sepsis [24]. In the present study, the MIC value was ≥16 μg/ml (33/34, 97%) for meropenem.

The antimicrobial therapy prescribed in this study coincides with the guidelines of ANVISA [28] Technical Note 01/2013, and in international studies [21,27] where the appropriate empirical therapy for multidrug-resistant enterobacteria infections is the use of polymyxin B or polymyxin E (colistin), in association with one or more antimicrobials such as aminoglycosides (gentamicin or amicacin), carbapenems (meropenem or doripenem) and tigecycline, avoiding the use of monotherapy due to the risk of developing resistance.

Studies with adults show that the institution of appropriate therapy is directly related to the reduction of mortality [27].

Early therapy was used in 19/34 patients (56%) of this population, and in 8/34 cases (23.5%) it was prescribed within 12 hours after blood culture results, and in 7/34 cases (20.5%) the appropriate therapy was prescribed within 48 hours after blood culture release. A study [29] demonstrates that for each hour of delay in administration there was an increase of 0.095 days in the length of stay in the ICU after infection.

The main prognostic factors associated with Klebsiella pneumoniae carbapenemase infection in children admitted to the PICU described in another study [26], conducted in Istanbul, were the use of mechanical ventilation, use of vasoactive drugs, previous hospitalization, acute renal injury, use of total parenteral nutrition, need for red blood cells transfusion and surgical procedures.

The resistance profile found in this study is similar to previously published studies [23], showing high resistance of KPC to carbapenems and cephalosporins, and consequent need for prevention studies, considering the susceptibility of the pediatric population.

When pathogenic bacteria develop resistance to multiple classes of antimicrobials, previously treatable diseases become lethal. Combating this challenge requires not only the discovery of new antimicrobial drugs, but also technological investment in rapid diagnosis and education of health professionals in the proper indication of antimicrobials, in addition to the participation of industry in the development of devices with technologies that also contribute to reduce the risk of infections related to health care.

Optimal therapy for the treatment of KPC bloodstream infection is not yet well defined for critically ill paediatric patients. It depends on the susceptibility of individual isolates of each patient and the choices that are very limited, based on the therapy used in adults.

The main limitation of this research was the fact that it was carried out in a single center, with retrospective design, being subject to data loss due to incomplete completion of medical records and small sample size.

Conclusion

The frequency of deaths was 23/34 cases, with mortality of 67.6% and the PELOD-2 score was the most relevant prognostic factor. The increase of one unit of the score on the day of infection increased the risk of death by 56% and the increase of one unit of the score in 48 hours after infection increased the risk of death by 64%.

Considering that the result of blood culture with antibiogram can take up to 72 hours to be obtained, these data corroborate the fact that measures aimed at the prevention and control of Carbapenemresistant K. pneumoniae infection are of great relevance especially in patients admitted to Intensive Care.

Contribution

Santos MLBM, Carvalho WB e Ferreira JCOA: Conception and design of the study, data collection, analysis and interpretation of the data, writing of the article and critical review of the important intellectual content, final approval of the version to be submitted.

Taminato M, Fernandes GJ e Delgado AF: Data collection, or analysis and interpretation of the data, writing of the article or critical review of the important intellectual content, final approval of the version to be submitted.

Ethical Considerations

The study was approved by the Research Ethics Committee. Certificate of Presentation for Ethical Appreciation (CAAE): 55779116.6.0000.0068. Research Ethics Committee Approval:

1.552.715.

Figures

Tables

References

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