Early Intravenous Colistin Therapy as a Favorable Prognostic Factor for 28-day Mortality in Patients with CRAB Bacteremia: a Multicenter Propensity Score-Matching Analysis

Optimizing Treatment for Carbapenem-Resistant Acinetobacter baumannii Complex Infections: A Review of Current Evidence

Carbapenem-resistant Acinetobacter baumannii complex (CRAB) poses a significant global health challenge owing to its resistance to multiple antibiotics and limited treatment options. Polymyxin-based therapies have been widely used to treat CRAB infections; however, they are associated with high mortality rates and common adverse events such as nephrotoxicity. Recent developments include numerous observational studies and randomized clinical trials investigating antibiotic combinations, repurposing existing antibiotics, and the development of novel agents. Consequently, recommendations for treating CRAB are undergoing significant changes. The importance of colistin is decreasing, and the role of sulbactam, which exhibits direct antibacterial activity against A. baumannii complex, is being reassessed. High-dose ampicillin-sulbactam-based combination therapies, as well as combinations of sulbactam and durlobactam, which prevent the hydrolysis of sulbactam and binds to penicillin-binding protein 2, have shown promising results. This review introduces recent advancements in CRAB infection treatment based on clinical trial data, highlighting the need for optimized treatment protocols and comprehensive clinical trials to combat the evolving threat of CRAB effectively.

Risk factors for bacteremic pneumonia and mortality (28-day mortality) in patients with Acinetobacter baumannii bacteremia

BACKGROUND

Patients infected with Acinetobacter baumannii (AB) bacteremia in hospital have high morbidity and mortality. We analyzed the clinical characteristics of pneumonia and nonpneumonia-related AB bloodstream infections (AB BSIs) and explored the possible independent risk factors for the incidence and prognosis of pneumonia-related AB BSIs.

METHODS

A retrospective monocentric observational study was performed. All 117 episodes of hospital-acquired AB bacteremia sorted into groups of pneumonia-related AB BSIs (n = 45) and nonpneumonia-related AB BSIs (n = 72) were eligible. Univariate/multivariate logistic regression analysis was used to explore the independent risk factors. The primary outcome was the antibiotic susceptibility in vitro of pneumonia-related AB BSIs group. The secondary outcome was the independent risk factor for the pneumonia-related AB BSIs group.

RESULTS

Among 117 patients with AB BSIs, the pneumonia-related group had a greater risk of multidrug resistant A. baumannii (MDRAB) infection (84.44%) and carbapenem-resistant A. baumannii (CRAB) infection (80%). Polymyxin, minocycline and amikacin had relatively high susceptibility rates (> 80%) in the nonpneumonia-related group. However, in the pneumonia-related group, only polymyxin had a drug susceptibility rate of over 80%. Univariate analysis showed that survival time (day), CRAB, MDRAB, length of hospital stay prior to culture, length of ICU stay prior to culture, immunocompromised status, antibiotics used prior to culture (n > = 3 types), endotracheal tube, fiberoptic bronchoscopy, PITT, SOFA and invasive interventions (n > = 3 types) were associated with pneumonia-related AB bacteremia. The multivariate logistic regression analysis revealed that recent surgery (within 1 mo) [P = 0.043; 0.306 (0.098-0.962)] and invasive interventions (n > = 3 types) [P = 0.021; 0.072 (0.008-0.671)] were independent risk factors related to pneumonia-related AB bacteremia. Multivariate logistic regression analysis revealed that length of ICU stay prior to culture [P = 0.009; 0.959 (0.930-0.990)] and recent surgery (within 1 mo) [P = 0.004; 0.260 (0.105-0.646)] were independent risk factors for mortality in patients with pneumonia-related AB bacteremia. The Kaplan‒Meier curve and the timing test showed that patients with pneumonia-related AB bacteremia had shorter survival time compared to those with nonpneumonia-related AB bacteremia.

CONCLUSIONS

Our study found that A. baumannii had a high rate of antibiotic resistance in vitro in the pneumonia-related bacteremia group, and was only sensitive to polymyxin. Recent surgery was a significantly independent predictor in patients with pneumonia-related AB bacteremia.

Risk factors for early mortality in patients with carbapenem-resistant Acinetobacter baumannii bacteraemia

OBJECTIVES

Although many deaths due to carbapenem-resistant Acinetobacter baumannii (CRAB) bacteraemia occur within a few days after the onset of bacteraemia, risk factors for early mortality (EM) have not been deeply investigated. We aimed to determine the risk factors for EM and the difference between risk factors associated with EM and late mortality (LM) in CRAB bacteraemia.

METHODS

Clinical information on all patients with CRAB bacteraemia in 10 hospitals during a 1-year period was collected. Among the cases with mortality within 30 days, EM and LM were defined as death within 3 and more than 5 calendar days from the first positive blood culture, respectively.

RESULTS

In total, 212 CRAB bacteraemia cases were included in the analysis. Of 122 (57.5%) patients with 30-day mortality, EM was observed in 75 (61.5%) patients and LM in 39 (32.0%) patients. The proportion of severe sepsis or septic shock, Pitt score, and Sequential Organ Failure Assessment (SOFA) score was significantly higher in patients with EM than those with LM. Although urinary tract infection as the site of infection and the severity of illness were independent predictors of LM, only factors representing the severity of illness were independent risk factors for EM.

CONCLUSION

Our results suggest that a large proportion of CRAB bacteraemia with high severity progresses to a rapidly fatal course, regardless of the underlying diseases or source of infection. Further studies might be needed to investigate the microbiological factors associated with CRAB and pathogen-host interaction in patients with EM.

Comparison of pneumonia- and non-pneumonia-related Acinetobacter baumannii complex bacteremia: A single-center retrospective study

BACKGROUND

Acinetobacter baumannii complex (ABC) is a group of increasingly prevalent opportunistic pathogens that cause a variety of life-threatening nosocomial infections, especially in the intensive care unit (ICU). This study assessed the differences between pneumonia- and non-pneumonia-related ABC bacteremia and possible independent risk factors for 30-day mortality.

METHODS

The clinical data of ICU patients diagnosed with ABC bacteremia at a tertiary care hospital from January 2009 to December 2020 were collected, and sorted into groups of ABC bacteremia with and without pneumonia.

RESULTS

Significant changes in the incidence of ABC bacteremia and antibiotic resistance were observed over the 12-year study. Compared with nonpneumonia-related ABC bacteremia, pneumonia-related ABC bacteremia was associated with a higher rate of hypertension, less prior tigecycline use, more carbapenem-resistant (CR) strains, and a higher 30-day mortality rate. In multivariate analysis, immunosuppression, higher APACHE II score, and SOFA score were independent risk factors for 30-day mortality. Moreover, the risk of death was 1.919 times higher in the pneumonia-related group.

CONCLUSIONS

Although pneumonia-related ABC bacteremia had worse outcomes, it was not an independent risk factor for death statistically. Immunosuppression and disease severity levels increased the risks of death in ICU patients with ABC bacteremia.

The epidemiology of bloodstream infection contributing to mortality: the difference between community-acquired, healthcare-associated, and hospital-acquired infections

BACKGROUND

The epidemiology of bloodstream infection (BSI) is well-established; however, little is known about the contribution of different pathogens to mortality. To understand true burden of BSI, pathogens contributing to mortality were investigated and compared according to where the BSI was acquired.

METHODS

Data from deceased patients in two teaching hospitals in the Republic of Korea were collected. BSI contributing mortality was defined as BSI within 2-weeks before death. Cases were grouped by acquisition sites: community-acquired (CA)-, healthcare-associated (HCA)-, and hospital-acquired (HA)-BSI. Drug resistance, BSI focus, and appropriateness of empirical antimicrobial therapy were also compared.

RESULTS

Among 1849 deceased patients in the hospitals, 280 (15.1%) patients experienced BSI within 2-weeks before death. In all, 71, 53, and 156 patients in the CA-, HCA-, and HA-BSI groups, respectively, with 316 total isolated pathogens were analyzed. The three most common pathogens were Klebsiella pneumoniae (17.1%), Escherichia coli (16.4%), and Staphylococcus aureus (11.4%). While K. pneumoniae and E. coli were the most common pathogens in CA- and HCA-BSI, Acinetobacter baumannii and Candida species were in HA-BSI. 26.3% (41/156) of patients experienced breakthrough HCA-BSI during administration of carbapenem and/or vancomycin. The proportion of central venous catheter-related infection (0%, 3.4% and 28.3%), carbapenem resistant-Gram negative bacilli (0%, 6.9% and 21.9%), and inappropriate empirical antimicrobial therapy (21.1%, 37.7% and 51.9%; all P < 0.001) were more frequently observed in HA-BSI.

CONCLUSION

The epidemiology of BSI related to mortality had unique characteristics according to the acquisition site. Given the epidemiology of HA-BSI, infection control and antibiotics stewardship programs should be emphasized.

Predictors of Acute Kidney Injury and 28-Day Mortality in Carbapenem-Resistant Acinetobacter baumannii Complex Bacteremia

Colistin is an, antibiotic used to treat carbapenem-resistant Acinetobacter baumannii complex (CRABC) infection. However, colistin is well known for its nephrotoxicity. To accurately assess the effects of colistin on acute kidney injury (AKI) and 28-day mortality, we investigated the risk factors associated with AKI and mortality in patients with CRABC bacteremia who received or never received colistin. Patients with CRABC bacteremia aged ≥18 years were retrospectively identified for 3 years at five tertiary teaching hospitals. AKI was defined by using the Kidney Disease Improving Global Outcomes criteria. AKI developed in 103 (34.9%) of the 295 patients enrolled patients. AKI developed more frequently in patients who received colistin than in patients who did not (46.7% vs. 29.5%, p = 0.004). Multivariate analysis showed that intravenous colistin usage was an independent risk factor for AKI in these patients. Nonfatal disease, catheter-related bloodstream infection, and administration of colistin were protective factors for 28-day mortality. However, the sequential organ failure assessment score and AKI were associated with poor outcomes. In conclusion, colistin may be a double-edged sword; although it causes AKI, it also reduces 28-day mortality in patients with CRABC bacteremia. Therefore, colistin administration as an appropriate antibiotic may improve CRABC bacteremia prognosis, despite its nephrotoxicity.

Clinical and Microbiological Analysis of Risk Factors for Mortality in Patients With Carbapenem-Resistant Acinetobacter baumannii Bacteremia

Background

Carbapenem-resistant Acinetobacter baumannii (CRAB) infection is associated with significant mortality, causing worldwide concern, yet there are limited data on contributing microbiological factors. This study aimed to identify the clinical and microbiologic risk factors for mortality in CRAB bacteremia.

Methods

Adult patients with monomicrobial CRAB bacteremia in a 2700-bed tertiary hospital between December 2012 and December 2018 were retrospectively enrolled. Risk factors for 30-day mortality were evaluated. All isolates collected on the first day of bacteremia were subjected to colistin susceptibility testing by broth microdilution and to genotyping by multilocus sequence typing.

Results

A total of 164 patients were enrolled, and 90 (55%) died within 30 days. The most common genotype among the isolates was ST191 (49%), and 12 isolates (7%) were resistant to colistin. Genotype, colistin minimum inhibitory concentration, and colistin resistance were not significantly associated with mortality, in contrast to several clinical factors. In multivariable analysis, ineradicable or not-eradicated focus (adjusted odds ratio [aOR], 4.92; 95% CI, 1.95–12.42; P = .001), septic shock (aOR, 4.72; 95% CI, 2.12–10.49; P < .001), and inappropriate antimicrobial therapy (aOR, 2.54; 95% CI, 1.05–6.16; P = .04) were independent risk factors for mortality. Among antibiotic strategies, colistin combined with tigecycline or other antibiotics were significantly associated with lower mortality after adjustment for confounding factors.

Conclusions

Clinical factors such as the nature of the infection source and source control, severity of bacteremia, and appropriateness of antibiotics, rather than microbiological factors, contribute to mortality in CRAB bacteremia. A specific antibiotic combination may help improve outcomes.

The effectiveness and nephrotoxicity of loading dose colistin combined with or without meropenem for the treatment of carbapenem-resistant A. baumannii

INTRODUCTION

Acinetobacter baumannii has emerged as an important nosocomial pathogen worldwide. In Thailand, the incidence and mortality rate of carbapenem-resistant A. baumannii (CRAB) is continuously increasing. This organism is a common pathogen that can cause HAP and VAP. CRAB tends to be susceptible to only colistin, so colistin would be the last line of treatment for CRAB. The recent data from in-vitro studies found that colistin and meropenem combination therapy could exert synergistic effects. However, some in-vivo studies have shown no significant difference in antibacterial effect between colistin monotherapy and colistin plus meropenem. Moreover, the clinical data are recently limited and not clear. Thus, the objective of this study was to compare clinical outcome, microbiological response, mortality rate and nephrotoxicity between loading dose (LD) colistin monotherapy and LD colistin-meropenem for treatment of infection caused by CRAB in Maharaj Nakorn Chiang Mai Hospital.

MATERIALS AND METHODS

This study is a retrospective analytical study. The data were collected from patients who received LD colistin monotherapy or LD colistin plus meropenem combination therapy for treatment of CRAB from 1 January 2013 to 31 August 2017 at Maharaj Nakorn Chiang Mai Hospital. A total of 324 patients met the inclusion criteria. The data were analyzed by descriptive statistics and inferential statistics, and were adjusted for confounding factors by logistic regression analysis.

RESULTS

The adjusted OR of good clinical outcome of patients who received LD colistin plus meropenem was 1.05 times that of patients who received loading dose colistin monotherapy (95%CI 0.62-1.74, p=0.860). Patients who received LD colistin plus meropenem had 0.93 times (adjusted OR) mortality rate at the end of treatment compared to patients who received LD colistin monotherapy (95%CI=0.51-1.71, p=0.935). In addition, microbiological response was defined as eradication of pre-treatment isolated pathogens in post-treatment cultures. Patients who received LD colistin plus meropenem could eradicate pathogens 1.28 times more than LD colistin monotherapy (95% CI=0.74-2.20, p=0.371). Also there was no significant difference in nephrotoxicity (adjusted OR=0.84, 95% CI 0.52-1.36, p=0.492) between LD colistin monotherapy and LD colistin plus meropenem.

CONCLUSION

There were no significant differences in effectiveness and nephrotoxicity of LD colistin monotherapy versus LD colistin plus meropenem for treatment of CRAB infection, so colistin combination therapy was not necessary for the management of infection caused by CRAB.