Colistin monotherapy or combination for the treatment of bloodstream infection caused by Klebsiella pneumoniae: a systematic review and meta-analysis.

BACKGROUND: Bloodstream infection of Klebsiella pneumoniae (BSI-KP) were associated with increased mortality. Klebsiella pneumoniae was tested to susceptible to colistin by E-test and broth microdilution method in clinical laboratory. This study aimed to assess the efficacy of colistin versus tigecycline, carbapenem monotherapy and combination in the treatment of BSI-KP. METHODS: Electronic databases such as PubMed, Web of Science and Embase were searched. The last search was in November 24th, 2022, addressing the colistin, carbapenems and tigecycline monotherapy and combination treatments in patients with BSI-KP. The primary outcomes were 30-day or 28-day mortality. OR where available with 95% CI were pooled in random-effects meta-analysis. RESULTS: Following the outlined search strategy, a total of 658 articles were identified from the initial database searching. Six studies, 17 comparisons were included. However, they all were observational design, lacking high-quality randomized controlled trials (RCTs). Moderate or low-quality evidences suggested that colistin monotherapy was associated with an OR = 1.35 (95% CI = 0.62-2.97, P = 0.45, Tau2 = 0.00, I2 = 0%) compared with tigecycline monotherapy, OR = 0.81 (95% CI = 0.27-2.45, P = 0.71, Tau2 = 0.00, I2 = 0%) compared with carbapenem monotherapy. Compared with combination with tigecycline or carbapenem, Colistin monotherapy resulted in OR of 3.07 (95% CI = 1.34-7.04, P = 0.008, Tau2 = 0.00, I2 = 0%) and 0.98 (95%CI = 0.29-3.31, P = 0.98, Tau2 = 0.00, I2 = 0% ), respectively. CONCLUSIONS: Colistin, carbapenem and tigecycline monotherapy showed similar treatment effects in patients who suffered from BSI-KP. Compared with colistin monotherapy, colistin combined tigecycline therapy might play the synergism effects. TRIAL REGISTRATION: retrospectively registered.

Colistin resistance increases 28-day mortality in bloodstream infections due to carbapenem-resistant Klebsiella pneumoniae.

Mortality due to K. pneumoniae bacteremia is on rise, particularly in regions with high rates of carbapenem and colistin resistance. We aimed to define risk factors for colistin resistance and its impact on mortality. Patients diagnosed with "carbapenem-resistant K. pneumoniae (CRKp)" bacteremia between 2014 and 2018 were divided into two groups as "colistin susceptible (ColS)" and "colistin resistant (ColR)" based on broth microdilution method. Retrospective case-control study was conducted to compare characteristics and outcomes. Multiple logistic regression model was used to define independent risk factors for acquired colistin resistance and Cox proportional hazard model for 28-day mortality. A total of 82 patients (39 ColS and 43 ColR) were included. Mean age was 61.5 years, and 50 (61%) were male. Colistin resistance was significantly increased with duration of hospital stay (p = 0.007) and prior colistin use (p = 0.007). Overall, the 28-day mortality rate was 66%. Age (p = 0.014) and colistin resistance significantly increased 28-day (p = 0.009) mortality. Microbiological response to treatment within 7 days favors survival. PFGE analysis revealed an outbreak with K. pneumoniae ST78 and ST45 clones. Patients treated with combined antimicrobials had significantly lower 28-day mortality (p = 0.045) in comparison to monotherapy. However, types of combinations did not show significant superiority on each other. Colistin resistance increases 28-day mortality in CRKp bacteremia. Although combined regimens are more effective than monotherapy, existing antibacterial combinations have no apparent superiority to each other. New treatment options are pivotal.

Clinical impact of cefepime breakpoint in patients with carbapenem-resistant Klebsiella pneumoniae bacteraemia.

The application of cefepime breakpoint for carbapenem-resistant Klebsiella pneumoniae (CRKP) bacteraemia has not been explored. Adult cases of monomicrobial bloodstream infection (BSI) caused by cefepime-susceptible [minimum inhibitory concentration (MIC) ≤8 mg/L] K. pneumoniae isolates with carbapenem resistance between 2010 and 2015 were reviewed. Patients treated with cefepime were compared with those treated by other active agents using a propensity score-matched analysis to assess therapeutic effectiveness. The primary endpoint was 30-day crude mortality. A total of 114 patients experienced cefepime-susceptible CRKP bacteraemia and 40 (35.1%) died during hospitalisation. A total of 33 patients (28.9%) received cefepime therapy. Fifteen patients (13.2%) had BSI due to carbapenemase-producing isolates, and 86.7% (13/15) of carbapenemase-producing isolates were classified as cefepime susceptible dose-dependent (SDD). In the multivariate logistic regression analysis, 30-day mortality was independently associated with the presence of a critical illness [adjusted odds ratio (aOR) = 12.89, 95% confidence interval (CI) 3.88-42.83; P < 0.001], pneumonia (aOR = 5.97, 95% CI 1.65-21.76; P = 0.007) and rapidly fatal underlying disease (aOR = 6.43, 95% CI 1.30-31.09; P = 0.02). In contrast, cefepime-based therapy (aOR = 0.03, 95% CI 0.003-0.38; P = 0.006) and combination therapy (aOR = 0.09, 95% CI 0.02-0.36; P = 0.001) were protective against a fatal outcome. Based on current breakpoints for Enterobacterales, cefepime therapy was not associated with an unfavourable outcome for CRKP BSI with MIC-based dosing strategies. However, the susceptibility result of SDD to cefepime should alert clinicians for possible therapeutic failure.

Treatment Outcome of Bacteremia Due to Non-Carbapenemase-producing Carbapenem-Resistant Klebsiella pneumoniae Bacteremia: Role of Carbapenem Combination Therapy.

PURPOSE: Infections caused by carbapenemase-producing Klebsiella pneumoniae are emerging causes of morbidity and mortality worldwide. Optimal treatment for non-carbapenemase-producing carbapenem-resistant K pneumoniae (nCP-CRKP) bacteremia remains undefined. The goal of this study was to assess the clinical outcome, predictors of mortality, and therapeutic strategy of carbapenems for nCP-CRKP bacteremia. METHODS: A retrospective study of monomicrobial bacteremia caused by nCP-CRKP, at a medical center between 2010 and 2015 was conducted. CRKP which was defined as a minimum inhibitory concentration (MIC) of ≥ 2 for ertapenem or ≥ 4 mg/L for meropenem, or imipenem. Multiplex polymerase chain was applied to detect carbapenemase genes. The patients definitively treated with combination therapy were compared with monotherapy using a propensity score-matched analysis to assess therapeutic effectiveness. The primary end point was the 30-day crude mortality and clinical prognostic factors were assessed. FINDINGS: Overall 171 patients met criteria were eligible for the study and their overall 30-day mortality rate was 38.6%. The multivariate logistic regression analysis showed that combination therapy was associated with a lower 30-day mortality rate (adjusted odds ratio [aOR], 0.11; 95% CI, 0.03-0.43; P = 0.001) and less clinical (aOR, 0.21; 95% CI, 0.08-0.58; P = 0.003) and microbiologic (aOR, 0.36; 95% CI, 0.19-0.71; P = 0.003) failure. However, the 30-day mortality rate in the cases infected by a pathogen with a meropenem MIC ≤8 mg/L receiving carbapenem-containing or carbapenem-sparing combination regimens was similar (15 of 58 [25.9%] vs 5 of 20 [23.3%]; P = 1.0). IMPLICATIONS: Combination therapy, regardless of carbapenem-containing or carbapenem-sparing, with one or more active agents improved survival more than monotherapy and was more effective in patients with critical illness. (Clin Ther. 2020; 42:XXX-XXX) © 2020 Elsevier HS Journals, Inc.

Coinfections of Two Strains of NDM-1- and OXA-232-Coproducing Klebsiella pneumoniae in a Kidney Transplant Patient.

We report here a fatal case of carbapenem-resistant Klebsiella pneumoniae (CRKP) infections in a renal transplant patient without a travel history in the prior year, from whom 2 genetically different CRKP (sequence type 14 [ST14] and ST2497) strains carrying the same plasmids and antimicrobial resistance genes, including blaNDM-1, blaOXA-232, blaCTX-M-15, armA, and tet(D), were isolated from blood and the abdominal cavity. The isolates were susceptible to colistin, tigecycline, eravacycline, and cefiderocol, which was used to treat the CRKP in combination with ceftazidime-avibactam and polymyxin B and resulted in bacterial clearance. Despite the aggressive treatment, the patient died of ischemic colitis and multiorgan failure.

Risk factors and survival of patients infected with carbapenem-resistant Klebsiella pneumoniae in a KPC endemic setting: a case-control and cohort study.

BACKGROUND: Many gaps in the burden of resistant pathogens exist in endemic areas of low- and middle-income economies, especially those endemic for carbapenem resistance. The aim of this study is to evaluate risk factors for carbapenem-resistance, to estimate the association between carbapenem-resistance and all-cause 30-day mortality and to examine whether mortality is mediated by inappropriate therapy. METHODS: A case-control and a cohort study were conducted in one tertiary-care hospital in Medellín, Colombia from 2014 to 2015. Phenotypic and genotypic characterization of isolates was performed. In the case-control study, cases were defined as patients infected with carbapenem-resistant K. pneumoniae (CRKP) and controls as patients infected with carbapenem-susceptible K. pneumoniae (CSKP). A risk factor analysis was conducted using logistic regression models. In the cohort study, the exposed group was defined as patients infected with CRKP and the non-exposed group as patients infected with CSKP. A survival analysis using an accelerated failure time model with a lognormal distribution was performed to estimate the association between carbapenem resistance and all-cause 30-day-mortality and to examine whether mortality is mediated by inappropriate therapy. RESULTS: A total of 338 patients were enrolled; 49 were infected with CRKP and 289 with CSKP. Among CRKP isolates CG258 (n = 29), ST25 (n = 5) and ST307 (n = 4) were detected. Of importance, every day of meropenem (OR 1.18, 95%CI 1.10-1.28) and cefepime (OR 1.22, 95%CI 1.03-1.49) use increase the risk of carbapenem resistance. Additional risk factors were previous use of ciprofloxacin (OR 2.37, 95%CI 1.00-5.35) and urinary catheter (OR 2.60, 95%CI 1.25-5.37). Furthermore, a significant lower survival time was estimated for patients infected with CRKP compared to CSKP (Relative Times 0.44, 95%CI 0.24-0.82). The strength of association was reduced when appropriate therapy was included in the model (RT = 0.81 95%CI 0.48-1.37). CONCLUSION: Short antibiotic courses had the potential to reduce the selection and transmission of CRKP. A high burden in mortality occurred in patients infected with CRKP in a KPC endemic setting and CRKP leads to increased mortality via inappropriate antibiotic treatment. Furthermore, dissemination of recognized hypervirulent clones could add to the list of challenges for antibiotic resistance control.

Prognosis of urinary tract infection caused by KPC-producing Klebsiella pneumoniae: The impact of inappropriate empirical treatment.

INTRODUCTION: There is scarce information on the prognosis of urinary tract infections (UTI) caused by KPC carbapenemase-producing Klebsiella pneumoniae (KPC-Kp). OBJETIVE: To investigate the association between KPC-Kp aetiology and clinical failure and all cause mortality and to explore the impact of inappropriate empirical treatment. MATERIAL AND METHODS: This is a retrospective observational study of hospitalized patients with UTI due to K. pneumoniae. We explored clinical failure at day 21 and 30-day all-cause mortality using different models of adjusted analysis. RESULTS: We analyzed 142 episodes of UTI; 46 episodes (32.4%) were due to KPC-Kp and 96 episodes (67.6%) were due to non-KPC-Kp strains (62 wild type and 34 EBSL producer). Clinical failure was more frequent in the KPC-Kp group (41.3% vs. 15.6%, p = 0.001). KPC-Kp aetiology and inappropriate empirical therapy were associated in the non-adjusted analysis with clinical failure. When analysed in separate adjusted models, both were found to be associated; inappropriate empirical treatment (OR 2.51; 95% CI, 1.03-6.12; p = 0.04) and KPC-Kp (OR 2.73; 95% CI, 1.03-7.22; p = 0.04) were associated with increased risk of failure. All-cause 30-day mortality was higher in patients with KPC-Kp UTI (39.1% vs. 15.6%, p = 0.002). Bacteraemia was more frequent in patients with KPC-Kp etiology (23.9% vs. 10.4%; p = 0.034). In both cases, the association was not confirmed in the adjusted analysis. CONCLUSION: KPC-Kp UTI is associated with higher clinical failure and may be due to an increase in inappropriate empirical treatment.

Use of Ceftazidime-avibactam for the Treatment of Extensively drug-resistant or Pan drug-resistant Klebsiella pneumoniae in Neonates and Children <5 Years of Age.

BACKGROUND: Emergence of extensively drug-resistant (XDR) or pan drug-resistant (PDR) Enterobacteriaceae is a major public threat especially for young patients. Treatment options for these bacteria are extremely limited with no safety data existing for neonates and children. Ceftazidime-avibactam has activity against Gram-negative bacteria producing Klebsiella pneumoniae carbapenemase, but virtually no data exist on its use in neonatal and pediatric patients. METHODS: We present a single-center case series of neonates and children <5 years treated with ceftazidime-avibactam for XDR or PDR K. pneumoniae infections until August 2018. Medical records of patients who received ceftazidime-avibactam for at least 2 days (6 doses) were reviewed. Clinical, laboratory and microbiologic data were collected using a prestructured form. Adverse events and clinical/microbiologic responses and 15- and 30-day outcome were assessed. RESULTS: In our case series, 8 patients (median age 53 days, range from 13 days to 4.5 years) received 9 courses of ceftazidime-avibactam at a dose of 62.5 mg/kg q8h for suspected or proven XDR/PDR K. pneumoniae infections including bloodstream infections (8 courses), central nervous system infections (2 courses) and urinary tract infection (1 course). All patients were critically ill and received other antibiotics prior and concomitantly with the administration of ceftazidime-avibactam. There was no treatment discontinuation due to adverse events. Clinical and microbiologic responses occurred in all patients, and no patient died by day 30. CONCLUSIONS: Administration of ceftazidime-avibactam appears to be well tolerated and efficacious against in vitro susceptible XDR or PDR Enterobacteriaceae without being associated with significant adverse events.

Combination therapy with polymyxin B for carbapenemase-producing Klebsiella pneumoniae bloodstream infection.

Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-KP) bloodstream infections (BSIs) are related to high mortality rates, and combination therapy has been associated with lower mortality in patients treated mostly with colistin. There is a paucity of studies addressing polymyxin B (PMB) treatment for KPC-KP infections. This was a retrospective cohort study of patients with monomicrobial KPC-KP BSIs. The primary outcome was 30-day mortality. Antimicrobial therapy was defined as empirical (started within the first 48 h) or definitive (initiated after >48 h) and was evaluated as follows: monotherapy (only one in vitro active agent or combination therapy of one in vitro active agent plus one or more in vitro non-active agents); and combination therapy with two or more in vitro active agents. A total of 82 KPC-KP BSIs were included; 40 patients (48.8%) died in the first 30 days. Mortality of patients treated with the combination of two in vitro active antimicrobial agents, mostly PMB plus amikacin, was significantly lower (37.5%) compared with monotherapy (64.7%) (P= 0.01). Combination therapy [adjusted hazard ratio (aHR) = 0.40, 95% confidence interval (CI) 0.22-0.83; P = 0.01] was independently associated with lower 30-day survival when controlled for non-surgical admission (aHR = 2.33, 95% CI 1.14-4.80; P = 0.02) and use of vasoactive drugs (aHR = 7.37, 95% CI 3.01-18.02; P < 0.01). In conclusion, combination therapy with two in vitro active agents, mostly PMB plus amikacin, showed a survival benefit compared with other regimens.

Mortality attributable to different Klebsiella susceptibility patterns and to the coverage of empirical antibiotic therapy: a cohort study on patients admitted to the ICU with infection.

PURPOSE: To evaluate the prognostic importance of different Klebsiella spp. sensitivity patterns: multi-susceptible Klebsiella (MS-K), extended-spectrum cephalosporin-resistant, but carbapenem-susceptible Klebsiella (ESCR-CS-K), and carbapenem-resistant Klebsiella (CR-K). METHODS: We developed a prognostic model to predict hospital mortality in patients with infection on admission to the intensive care units (ICUs), and assessed its calibration in the subgroups of interest: patients with infections due to MS-K, ESCR-CS-K, CR-K. We assessed the calibration of the model also in ESCR-CS-K treated empirically with carbapenems and with piperacillin-tazobactam. RESULTS: A total of 13,292 adults with an ongoing infection were admitted to 137 Italian ICUs in 2012-2013. Of 801 Klebsiella spp. infected patients, 451 had MS-K, 116 ESCR-CS-K, and 234 CR-K. The prognostic model calibrated well for the MS-K and ESCR-CS-K subgroups. In the CR-K subgroup there were more deaths than predicted (standardized mortality ratio 1.20; 95% CI 1.08-1.31), indicating a negative prognostic role of the infection, mainly in the medium and high risk-of-death patients. When infection was caused by ESCR-CS-K, treatment with piperacillin-tazobactam increased adjusted mortality among the most severe patients (similarly to CR-K), while treatment with carbapenems did not (similarly to MS-K). CONCLUSIONS: In low risk-of-death patients admitted to the ICU with a Klebsiella spp. infection, the appropriateness of empirical antibiotic therapy seemed uninfluential to eventual mortality, while it appeared to be crucial in high-risk ones. The use of piperacillin-tazobactam may be inappropriate in severe patients with ESCR-CS-K infection. CR-K is associated to a significant 20% increase of adjusted mortality, only for patients at higher risk of death.

Treatment outcome of non-carbapenemase-producing carbapenem-resistant Klebsiella pneumoniae infections: a multicenter study in Taiwan.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are associated with high mortality, and experiences with its treatment are usually based on carbapenemase-producing strains. Non-carbapenemase-producing CRKP is of clinical significance, but relevant studies are lacking. This nationwide study aimed to evaluate the outcome of antimicrobial therapy in patients with non-carbapenemase-producing CRKP infections. Patients with non-carbapenemase-producing CRKP infections were enrolled from 16 hospitals during January 2013 to December 2014 in Taiwan. Carbapenem resistance was defined as reduced susceptibility with a minimum inhibitory concentration of ≥2 mg/L for imipenem or meropenem. The resistance mechanisms of CRKP isolates were analyzed, and the clinical data of these patients were collected retrospectively. Independent risk factors of 14-day morality were determined by Cox regression analysis. A total of 99 patients with non-carbapenemase-producing CRKP infections were enrolled, and 14-day mortality was 27.3%. Among 67 patients treated with appropriate antimicrobial therapy, most (n = 61) patients received monotherapy. The 14-day mortality was lower in patients treated with appropriate monotherapy (21.3%) than in those with inappropriate therapy (37.5%). The multivariate regression model identified monotherapy (hazard ratio [HR], 0.30; 95% confidence interval [CI], 0.13-0.71; P = 0.005) as protective factor, and APACHE II scores (HR, 1.09; 95% CI, 1.01-1.18; P = 0.022) as risk factor associated with 14-day mortality. Tigecycline, colistin, and carbapenem were the most commonly used drugs in monotherapy. This study provides evidence supporting the efficacy of monotherapy in the treatment of non-carbapenemase-producing CRKP infections, and provides a future target for antibiotics stewardship for CRKP infection.

Association of high mortality with extended-spectrum ß-lactamase (ESBL) positive cultures in community acquired infections.

PURPOSE: Infections due to multidrug resistant organisms have become a serious health concern worldwide. The present study was conducted to investigate the spectrum of microbial resistance pattern in the community and their effects on mortality. METHODS: A retrospective review and analysis of prospectively collected data was done of all patients admitted with diagnosis of sepsis in two tertiary care ICU's for a period of two years. Demographics, culture positivity, microbial spectrum, resistance pattern and outcome data were collected. RESULTS: Out of 5309 patients enrolled; 3822 had suspected clinical infection on admission with 1452 patients growing positive microbial cultures. Among these, 201 bacterial strains were isolated from patients who had community acquired infections. 73% were Gram negative bacilli, commonest being E. coli (63%). 63.4% E. coli and 60.7% Klebsiella isolates were ESBL producers. The mortality in ESBL positive infections was significantly higher as compared to ESBL negative infections (Odds ratio 2.756). Moreover, ESBL positive patients empirically treated with Beta Lactams+Beta Lactamase inhibitors (BL+BLI) had significantly higher mortality as compared to patients treated with carbapenems. More data from multiple centres need to be gathered to formulate appropriate antibiotic policy for critically ill patients admitted from the community.

Immune stealth-driven O2 serotype prevalence and potential for therapeutic antibodies against multidrug resistant Klebsiella pneumoniae.

Emerging multidrug-resistant bacteria are a challenge for modern medicine, but how these pathogens are so successful is not fully understood. Robust antibacterial vaccines have prevented and reduced resistance suggesting a pivotal role for immunity in deterring antibiotic resistance. Here, we show the increased prevalence of Klebsiella pneumoniae lipopolysaccharide O2 serotype strains in all major drug resistance groups correlating with a paucity of anti-O2 antibodies in human B cell repertoires. We identify human monoclonal antibodies to O-antigens that are highly protective in mouse models of infection, even against heavily encapsulated strains. These antibodies, including a rare anti-O2 specific antibody, synergistically protect against drug-resistant strains in adjunctive therapy with meropenem, a standard-of-care antibiotic, confirming the importance of immune assistance in antibiotic therapy. These findings support an antibody-based immunotherapeutic strategy even for highly resistant K. pneumoniae infections, and underscore the effect humoral immunity has on evolving drug resistance.

Triple combination antibiotic therapy for carbapenemase-producing Klebsiella pneumoniae: a systematic review.

BACKGROUND: The spread of carbapenemase-producing K. pneumoniae (CPKP) has become a significant problem worldwide. Combination therapy for CPKP is encouraging, but polymyxin resistance to many antibiotics is hampering effective treatment. Combination therapy with three or more antibiotics is being increasingly reported, therefore we performed a systematic review of triple combination cases in an effort to evaluate their clinical effectiveness for CPKP infections. METHODS: The PubMed database was searched to identify all published clinical outcomes of CPKP infections treated with triple combination therapy. Articles were stratified into two tiers depending on the level of clinical detail provided. A tier 1 study included: antibiotic regimen, regimen-specific outcome, patient status at onset of infection, and source of infection. Articles not reaching these criteria were considered tier 2. RESULTS: Thirty-three studies were eligible, 23 tier 1 and ten tier 2. Among tier 1 studies, 53 cases were included in this analysis. The most common infection was pneumonia (31%) followed by primary or catheter-related bacteremia (21%) and urinary tract infection (17%). Different combinations of antibiotic classes were utilized in triple combinations, the most common being a polymyxin (colistin or polymyxin B, 86.8%), tigecycline (73.6%), aminoglycoside (43.4%), or carbapenem (43.4%). Clinical and microbiological failure occurred in 14/39 patients (35.9%) and 22/42 patients (52.4%), respectively. Overall mortality for patients treated with triple combination therapy was 35.8% (19/53 patients). CONCLUSIONS: Triple combination therapy is being considered as a treatment option for CPKP. Polymyxin-based therapy is the backbone antibiotic in these regimens, but its effectiveness needs establishing in prospective clinical trials.

Mortality Associated with Bacteremia Due to Colistin-Resistant Klebsiella pneumoniae with High-Level Meropenem Resistance: Importance of Combination Therapy without Colistin and Carbapenems.

Combination therapy including colistin and a carbapenem has been found to be associated with lower mortality in the treatment of bloodstream infections (BSI) due to KPC-producing Klebsiella pneumoniae when the isolates show a meropenem or imipenem MIC of <16 mg/liter. However, the optimal treatment of BSI caused by colistin- and high-level carbapenem-resistant KPC-producing K. pneumoniae is unknown. A prospective cohort study including episodes of bacteremia caused by colistin-resistant and high-level meropenem-resistant (MIC ≥ 64 mg/liter) KPC-producing K. pneumoniae diagnosed from July 2012 to February 2016 was performed. The impact of combination therapy on crude 30-day mortality was analyzed by Cox regression using a propensity score as a covariate to control for indication bias and in an inverse probability of treatment weighting (IPTW) cohort. The study sample comprised 104 patients, of which 32 (30.8%) received targeted monotherapy and 72 (69.2%) received targeted combination therapy; none of them received either colistin or a carbapenem. The 30-day crude mortality rate was 30.8% (43.8% in patients treated with monotherapy and 25% in patients receiving combination therapy). In the Cox regression analysis, 30-day mortality was independently associated with septic shock at BSI onset (hazard ratio [HR], 6.03; 95% confidence interval [CI], 1.65 to 21.9; P = 0.006) and admission to the critical care unit (HR, 2.87; 95% CI, 0.99 to 8.27; P = 0.05). Targeted combination therapy was associated with lower mortality only in patients with septic shock (HR, 0.14; 95% CI, 0.03 to 0.67; P = 0.01). These results were confirmed in the Cox regression analysis of the IPTW cohort. Combination therapy is associated with reduced mortality in patients with bacteremia due to colistin-resistant KPC-producing K. pneumoniae with high-level carbapenem resistance in patients with septic shock.

Colistin Resistance in Carbapenem-Resistant Klebsiella pneumoniae: Laboratory Detection and Impact on Mortality.

Background: Polymyxins including colistin are an important "last-line" treatment for infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKp). Increasing use of colistin has led to resistance to this cationic antimicrobial peptide. Methods: A cohort nested within the Consortium on Resistance against Carbapenems in Klebsiella pneumoniae (CRACKLE) was constructed of patients with infection, or colonization with CRKp isolates tested for colistin susceptibility during the study period of December, 2011 to October, 2014. Reference colistin resistance determination as performed by broth macrodilution was compared to results from clinical microbiology laboratories (Etest) and to polymyxin resistance testing. Each patient was included once, at the time of their first colistin-tested CRKp positive culture. Time to 30-day in-hospital all-cause mortality was evaluated by Kaplan-Meier curves and Cox proportional hazard modeling. Results: In 246 patients with CRKp, 13% possessed ColR CRKp. ColR was underestimated by Etest (very major error rate = 35%, major error rate = 0.4%). A variety of rep-PCR strain types were encountered in both the ColS and the ColR groups. Carbapenem resistance was mediated primarily by blaKPC-2 (46%) and blaKPC-3 (50%). ColR was associated with increased hazard for in-hospital mortality (aHR 3.48; 95% confidence interval, 1.73-6.57; P < .001). The plasmid-associated ColR genes, mcr-1 and mcr-2 were not detected in any of the ColR CRKp. Conclusions: In this cohort, 13% of patients with CRKp presented with ColR CRKp. The apparent polyclonal nature of the isolates suggests de novo emergence of ColR in this cohort as the primary factor driving ColR. Importantly, mortality was increased in patients with ColR isolates.

Risk Factors, Outcomes, and Mechanisms of Tigecycline-Nonsusceptible Klebsiella pneumoniae Bacteremia.

A rise in tigecycline resistance in Klebsiella pneumoniae has been reported recently worldwide. We sought to identify risk factors, outcomes, and mechanisms for adult patients with tigecycline-nonsusceptible K. pneumoniae bacteremia in Taiwan. We conducted a matched case-control study (ratio of 1:1) in a medical center in Taiwan from January 2011 through June 2015. The cases were patients with tigecycline-nonsusceptible K. pneumoniae bacteremia, and the controls were patients with tigecycline-susceptible K. pneumoniae bacteremia. Logistic regression was performed to evaluate the potential risk factors for tigecycline-nonsusceptible K. pneumoniae bacteremia. Quantitative reverse transcription-PCR was performed to analyze acrA, oqxA, ramA, rarA, and kpgA expression among these isolates. A total of 43 cases were matched with 43 controls. The 14-day mortality of patients with tigecycline-nonsusceptible K. pneumoniae bacteremia was 30.2%, and the 28-day mortality was 41.9%. The attributable mortalities of tigecycline-nonsusceptible K. pneumoniae at 14 and 28 days were 9.3 and 18.6%, respectively. Fluoroquinolone use within 30 days prior to bacteremia was the only independent risk factor for tigecycline-nonsusceptible K. pneumoniae bacteremia. The tigecycline-nonsusceptible K. pneumoniae bacteremia was mostly caused by overexpression of AcrAB and/or OqxAB efflux pumps, together with the upregulation of RamA and/or RarA, respectively. One isolate demonstrated isolated overexpression of kpgA In conclusion, tigecycline-nonsusceptible K. pneumoniae bacteremia was associated with high mortality, and prior fluoroquinolone use was the independent risk factor for the acquisition of tigecycline-nonsusceptible K. pneumoniae The overexpression of AcrAB and/or OqxAB contributes to tigecycline nonsusceptibility in K. pneumoniae.

Combination Regimens for Treatment of Carbapenem-Resistant Klebsiella pneumoniae Bloodstream Infections.

Previous studies reported decreased mortality in patients with carbapenemase-producing Klebsiella pneumoniae bloodstream infections (BSIs) treated with combination therapy but included carbapenem-susceptible and -intermediate isolates, as per revised CLSI breakpoints. Here, we assessed outcomes in patients with BSIs caused by phenotypically carbapenem-resistant K. pneumoniae (CRKP) according to the number of in vitro active agents received and whether an extended-spectrum beta-lactam (BL) antibiotic, including meropenem, or an extended-spectrum cephalosporin was administered. We retrospectively reviewed CRKP BSIs at two New York City hospitals from 2006 to 2013, where all isolates had meropenem or imipenem MICs of ≥4 µg/ml. Univariate and multivariable models were created to identify factors associated with mortality. Of 141 CRKP BSI episodes, 23% were treated with a single active agent (SAA), 26% were treated with an SAA plus BL, 28% were treated with multiple active agents (MAA), and 23% were treated with MAA plus BL. Ninety percent of isolates had meropenem MICs of ≥16 µg/ml. Thirty-day mortality was 33% overall and did not significantly differ across the four treatment groups in a multivariable model (P = 0.4); mortality was significantly associated with a Pitt bacteremia score of ≥4 (odds ratio [OR], 7.7; 95% confidence interval [CI], 3.2 to 18.1; P = 0.1), and immunosuppression was protective (OR, 0.4; 95% CI, 0.2 to 1.0; P = 0.04). Individual treatment characteristics were also not significantly associated with outcome, including use of SAAs versus MAA (26% versus 38%, P = 0.1) or BL versus no BL (26% versus 39%, P = 0.1). In summary, in patients with CRKP BSIs caused by isolates with high carbapenem MICs, the role of combination therapy remains unclear, highlighting the need for prospective studies to identify optimal treatment regimens.

Occult Klebsiella pneumoniae bacteremia at emergency department: A single center experience.

BACKGROUND/PURPOSE: Patients with undetected bacteremia when discharged from a hospital are considered to have occult bacteremia. Klebsiella pneumoniae bacteremia (KPB) is endemic to Taiwan. Our purpose was to study the impact of occult KPB. METHODS: We retrospectively reviewed the records of patients who were discharged from our emergency department (ED) and subsequently diagnosed with KPB (occult bacteremia), from January 2008 to March 2014. All patients are followed for at least 3 months after the index ED visit. The study group was compared to KPB patients who were directly hospitalized (DH) from ED in 2008. Thirty-day mortality was the primary endpoint. RESULTS: A total of 913 patients were admitted to our ED with KPB, and 88 of these patients (9.6%) had occult KPB. Among them, 43 had second ED visit and 41 were admitted. The overall 30-day mortality was 2.3%. Relative to patients with occult KPB, DH patients had more respiratory tract infections (p < 0.001) but fewer other intra-abdominal infections (p = 0.015). Liver abscess was the major diagnosis for the second ED visit (37.2%). DH patients had significantly greater 30-day mortality than that of overall patients with KPB (19.2% vs.2.3%, p < 0.001). CONCLUSION: Most patients with occult KPB had favorable outcomes, but about half of them required a second ED visit. Clinicians should aggressively follow patients with occult KPB and should seek to identify the focus of infection in this endemic area.

Comparative effectiveness of flomoxef versus carbapenems in the treatment of bacteraemia due to extended-spectrum ß-lactamase-producing Escherichia coli or Klebsiella pneumoniae with emphasis on minimum inhibitory concentration of flomoxef: a retrospective study.

This study compared treatment outcomes of adult patients with bacteraemia due to extended-spectrum ß-lactamase-producing Escherichia coli or Klebsiella pneumoniae (ESBL-EK) receiving flomoxef versus those receiving a carbapenem as definitive therapy. In propensity score matching (PSM) analysis, case patients receiving flomoxef shown to be active in vitro against ESBL-EK were matched with controls who received a carbapenem. The primary endpoint was 30-day crude mortality. The flomoxef group had statistically significantly higher sepsis-related mortality (27.3% vs. 10.5%) and 30-day mortality (28.8% vs. 12.8%) than the carbapenem group. Of the bacteraemic episodes caused by isolates with a MICflomoxef of ≤1 mg/L, sepsis-related mortality rates were similar between the two treatment groups (8.7% vs. 6.4%; P=0.73). The sepsis-related mortality rate of the flomoxef group increased to 29.6% and 50.0% of episodes caused by isolates with a MICflomoxef of 2-4 mg/L and 8 mg/L, respectively, which was significantly higher than the carbapenem group (12.3%). In the PSM analysis of 86 case-control pairs infected with strains with a MICflomoxef of 2-8 mg/L, case patients had a significantly higher 30-day mortality rate (38.4% vs. 18.6%). Multivariate regression analysis revealed that flomoxef therapy for isolates with a MICflomoxef of 2-8 mg/L, concurrent pneumonia or urosepsis, and a Pitt bacteraemia score ≥4 were independently associated with 30-day mortality. Definitive flomoxef therapy appears to be inferior to carbapenems in treating ESBL-EK bacteraemia, particularly for isolates with a MICflomoxef of 2-8 mg/L, even though the currently suggested MIC breakpoint of flomoxef is ≤8 mg/L.