Risk factors and outcomes of bloodstream infections caused by Acinetobacter baumannii: a case-control study

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.

Shift in risk factors for mortality by period of the bloodstream infection timeline

BACKGROUND

This study was designed to determine changes in risk factors on the prognosis of patients during each period of the bloodstream infection (BSI) timeline.

METHODS

Through an integrated study of multivariable regressions with machine learning techniques, the risk factors for mortality during each period of BSI were analyzed.

RESULTS

A total of 302,303 inpatients who underwent blood cultures during 2011-2021 were enrolled. More than 8 % of BSI cases progressed to subsequent BSI, and risk factors were identified as gut colonization with vancomycin-resistant enterococci (aOR 1.82; 95 % CI 1.47-2.24), intensive care unit admission (aOR 3.37; 95 % CI 3.35-4.28), and current cancer chemotherapy (aOR 1.54; 95 % CI 1.36-1.74). The mean SOFA score of the deceased patients during the first 7 days was 10.6 (SD 4.3), which was significantly higher than those on days 8-30 (7.0 ± 4.2) and after Day 30 (4.0 ± 3.5). BSIs caused by Acinetobacter baumannii and Candida albicans were more likely to result in deaths of patients for all time periods (all, P < 0.001). BSIs caused by Enterococcus faecalis and Enterococcus faecium were associated with a poor outcome in the period after Day 30 (both, P < 0.001). Nonsusceptible phenotypes to β-lactam/β-lactamase inhibitors of Escherichia coli and Klebsiella pneumoniae influenced the prognoses of patients with BSI in terms of high mortality rates during both days 8-30 and after Day 30.

CONCLUSION

Influence of microbiological factors on mortality, including BSI-causative microorganisms and their major antimicrobial resistance, was emphasized in both periods of days 8-30 and after Day 30.

Bloodstream Infection in the Intensive Care Unit: Evolving Epidemiology and Microbiology

Bloodstream infections (BSIs) arising in the intensive care unit (ICUs) present a significant challenge and we completed a narrative review of the emerging literature on this issue. Multiple reports document that these infections are associated with substantial morbidity and mortality. Also, they can be caused by a variety of pathogens. Generally classified as either community or hospital in onset, or as either primary or secondary in origin, the microbiology of ICU BSIs varies across the globe. Gram-positive pathogens predominate in certain regions such as the United States while Gram-negative organisms occur more frequently in Europe, Asia, and Latin America. The incidence of ICU BSIs climbed during the recent pandemic. BSIs complicating the care of persons suffering from Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection significantly heighten the risk for death compared to patients who develop ICU BSIs but who are not infected with SARS-CoV-2. Furthermore, rates of antimicrobial resistance are generally increasing in ICU BSIs. This fact complicates attempts to ensure that the patient receives initially appropriate antimicrobial therapy and is of particular concern in Methicillin-resistant Staphylococcus aureus, Carbapenem-resistant Enterobacterales, and Acinetobacter baumannii. Fortunately, with respect to clinical application, preventive measures exist, and recent analyses suggest that increased collaboration between infectious disease specialists and intensivists can improve patient outcomes.

Risk factors for progression to bacteremia among patients with nosocomial carbapenem-resistant Acinetobacter baumannii pneumonia in the Intensive Care Unit

Antibiotic-resistant Acinetobacter baumannii (A. baumannii) is a common cause of hospital-acquired infections. This study aimed to identify independent factors associated with progression from nosocomial pneumonia to bacteremia in patients infected with carbapenem-resistant A. baumannii (CR-AB). From 2019 to 2021, we conducted a retrospective anaylsis of the medical records of 159 nosocomial CR-AB pneumonia patients in our Intensive Care Unit (ICU). We employed both univariate and multivariable logistic regression models to identify factors associated with the progression of nosocomial CR-AB pneumonia to bacteremia. Among the 159 patients with nosocomial CR-AB pneumonia, 40 experienced progression to bacteremia and 38 died within 28 days following diagnosis. Patients who developed bacteremia had a significantly higher 28-day mortality rate compared to those without bloodstream infection (47.50% vs. 15.97%). Multivariable logistic regression revealed that higher levels of C-Reactive protein (CRP) (OR = 1.01) and the use of continuous veno-venous hemofiltration (CVVH) treatment (OR = 2.93) were independently associated with an elevated risk of developing bacteremia. Among patients who developed bloodstream infection, those who died within 28 days exhibited significantly higher level of interleukin-6 (IL-6), a greater frequency of antifungal drugs usage, and a longer duration of machanical ventilation compared to survivors. Furthermore, the use of antifungal drugs was the only factor that associated with 28-day mortality (OR = 4.70). In ICU patients with central venous catheters who have CR-AB pneumonia and are on mechanical ventilation, higher CRP levels and CVVH treatment are risk factors for developing bacteremia. Among patients with bacteremia, the use of antifungal drugs is associated with 28-day mortality.

Global genomic epidemiology of chromosomally mediated non-enzymatic carbapenem resistance in Acinetobacter baumannii: on the way to predict and modify resistance

Introduction

Although carbapenemases are frequently reported in resistant A. baumannii clinical isolates, other chromosomally mediated elements of resistance that are considered essential are frequently underestimated. Having a wide substrate range, multidrug efflux pumps frequently underlie antibiotic treatment failure. Recognizing and exploiting variations in multidrug efflux pumps and penicillin-binding proteins (PBPs) is an essential approach in new antibiotic drug discovery and engineering to meet the growing challenge of multidrug-resistant Gram-negative bacteria.

Methods

A total of 980 whole genome sequences of A. baumannii were analyzed. Nucleotide sequences for the genes studied were queried against a custom database of FASTA sequences using the Bacterial and Viral Bioinformatics Resource Center (BV-BRC) system. The correlation between different variants and carbapenem Minimum Inhibitory Concentrations (MICs) was studied. PROVEAN and I-Mutant predictor suites were used to predict the effect of the studied amino acid substitutions on protein function and protein stability. Both PsiPred and FUpred were used for domain and secondary structure prediction. Phylogenetic reconstruction was performed using SANS serif and then visualized using iTOL and Phandango.

Results

Exhibiting the highest detection rate, AdeB codes for an important efflux-pump structural protein. T48V, T584I, and P660Q were important variants identified in the AdeB-predicted multidrug efflux transporter pore domains. These can act as probable targets for designing new efflux-pump inhibitors. Each of AdeC Q239L and AdeS D167N can also act as probable targets for restoring carbapenem susceptibility. Membrane proteins appear to have lower predictive potential than efflux pump-related changes. OprB and OprD changes show a greater effect than OmpA, OmpW, Omp33, and CarO changes on carbapenem susceptibility. Functional and statistical evidence make the variants T636A and S382N at PBP1a good markers for imipenem susceptibility and potential important drug targets that can modify imipenem resistance. In addition, PBP3_370, PBP1a_T636A, and PBP1a_S382N may act as potential drug targets that can be exploited to counteract imipenem resistance.

Conclusion

The study presents a comprehensive epidemiologic and statistical analysis of potential membrane proteins and efflux-pump variants related to carbapenem susceptibility in A. baumannii, shedding light on their clinical utility as diagnostic markers and treatment modification targets for more focused studies of candidate elements.

Initial indicators for the prognosis of Acinetobacter Baumannii bacteremia in children

BACKGROUND

Risk factors related to mortality due to Acinetobacter baumannii (AB) bacteremia have been unveiled previously, but early clinical manifestations of AB bacteremia based on prognosis remain uncovered.

METHODS

The demographic characteristics, clinical features, antibiotic susceptibility, and outcomes of 37 hospitalized children with laboratory-confirmed AB bacteremia from Suzhou, China, were collected and analyzed retrospectively.

RESULTS

Of the 37 children with AB bacteremia included in this study, 23 were males and 14 were females, with a median age of 4.83 (0.60 to 10.15) years. Among the children, 18 died (48.65%, 18/37) and 19 survived (51.35%, 19/37). The dead group had a significantly higher incidence of respiratory failure (p = 0.008), shock (P = 0.000), MODS (p = 0.000), neutropenia (< 1.5 × 109/L) (p = 0.000) and serious neutropenia (< 0.5 × 109/L) (p = 0.000) than those in the survival group. The death group had significantly more invasive procedures (2 or more) than that in the survival group at 2 weeks before onset (p = 0.005). The proportion of MDR-AB in the death group was significantly higher than that in the survival group (p = 0.000), while the PICS score was significantly lower in the survival group than that in the death group (p = 0.000). There was no significant difference in effective antibiotic use within 24 h between these two groups (p = 0.295). Among the 37 children with bloodstream infection of AB, 56.76% (21/37) of the underlying diseases were hematological diseases and oncology. Among them, 17 (81.00%) were died in the hospital. The proportion of white blood cells (p = 0.000), neutrophils (p = 0.042), eosinophils (p = 0.029), the ANC (p = 0.000) and lymphocyte (p = 0.000), the NLR(p = 0.011), hemoglobin (p = 0.001), platelets (p = 0.000), prealbumin (P = 0.000), LDH (p = 0.017), blood gas pH (p = 0.000), and serum potassium (p = 0.002) in the death group were significantly lower than those in the survival group. However, CRP (p = 0.000) and blood glucose(p = 0.036) were significantly higher in the death group than those in the survival group. By further multivariate analysis, CRP [OR (95% CI): 1.022(1.003, 1.041), p = 0.021] and neutropenia [OR (95% CI): 21.634 (2.05, 228.313, p = 0.011] within 24 h of infection were independent risk factors for death in children with AB bacteremia. When CRP was higher than 59.02 mg/L, the sensitivity of predicting mortality was 88.9%, and the specificity was 78.9%. And the sensitivity and specificity of neutropenia for predicting mortality were 83.3% and 84.2%.

CONCLUSIONS

AB bacteremia has a high mortality in children, especially in patients with hematological diseases and oncology. Many early indicators were associated with poor prognosis, while elevated CRP and neutropenia were the independent predictors for the 30-day mortality of children with laboratory-confirmed AB bacteremia.

Excess mortality and long-term disability from healthcare-associated carbapenem-resistant Acinetobacter baumannii infections: A nationwide population-based matched cohort study

BACKGROUND

Carbapenem resistance is perceived as a clinical challenge in the management of debilitated and immunocompromised patients who eventually will die from underlying diseases. We aimed to examine whether carbapenem resistance per se, rather than the underlying diseases, negatively affect outcomes, by comparing the excess mortality and morbidity from healthcare-associated infections (HAIs) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-susceptible A. baumannii (CSAB).

METHODS

This was a nationwide retrospective matched cohort study of hospitalized patients in 96 hospitals which participated in Taiwan Nosocomial Infection Surveillance (TNIS). A total of 2,213 patients with A. baumannii HAIs were individually matched to 4,426 patients without HAIs. Main outcomes were excess risks for one-year all-cause mortality and one-year new-onset chronic ventilator dependence or dialysis-dependent end-stage renal disease.

RESULTS

Excess one-year mortality was 27.2% in CRAB patients, compared with their matched uninfected inpatients, as well as 15.4% in CSAB patients (also compared with their matched uninfected inpatients), resulting in an attributable mortality of 11.8% (P <0.001) associated with carbapenem resistance. The excess risk associated with carbapenem resistance for new-onset chronic ventilator dependence was 5.2% (P <0.001). Carbapenem resistance was also associated with an extra cost of $2,511 per case of A. baumannii HAIs (P <0.001).

CONCLUSION

Carbapenem resistance is associated with a significant disease burden in terms of excess mortality, long-term ventilator dependence, and medical cost. Further studies on effects of antimicrobial stewardship programs in decreasing this burden are warranted.

Risk factors for carbapenem-resistant Acinetobacter baumannii (CRAB) bloodstream infections and related mortality in critically ill patients with CRAB colonization

Background

Among MDR bacteria, carbapenem-resistant Acinetobacter baumannii (CRAB) is a major concern due to the limited therapeutic options. During the COVID-19 pandemic, a worrying increase in the spread of CRAB infections was reported.

Objectives

The study assessed the risk factors for CRAB bloodstream infection (BSI) in patients admitted to the ICU with CRAB colonization, and the related mortality risk factors.

Methods

We conducted a single-centre, observational, prospective study; all consecutive patients with CRAB colonization admitted to the ICU of a tertiary hospital in Rome from January 2021 to September 2022 were included in the study. Univariate and multivariate analyses were performed to investigate BSI and mortality risk factors.

Results

Overall, 129 patients were included in the study; 57 (44%) out of these developed BSI. In our study population, at the multivariable analysis the Charlson comorbidity index (CCI) (P = 0.026), COVID-19 (P < 0.001), multisite colonization (P = 0.016) and the need for mechanical ventilation (P = 0.024) were risk factors independently associated with BSI development. Furthermore, age (P = 0.026), CCI (P < 0.001), septic shock (P = 0.001) and Pitt score (P < 0.001) were independently associated with mortality in the BSI patients. Instead, early appropriate therapy (P = 0.002) and clinical improvement within 72 h (P = 0.011) were shown to be protective factors.

Conclusions

In critically ill patients colonized by CRAB, higher CCI, multisite colonization and the need for mechanical ventilation were identified as risk factors for BSI onset. These predictors could be useful to identify patients at highest risk of BSI.

Outer Membrane Vesicle-Coated Nanoparticle Vaccine Protects Against Acinetobacter baumannii Pneumonia and Sepsis

The highly multidrug-resistant (MDR) Gram-negative bacterial pathogen Acinetobacter baumannii is a top global health priority where an effective vaccine could protect susceptible populations and limit resistance acquisition. Outer membrane vesicles (OMVs) shed from Gram-negative bacteria are enriched with virulence factors and membrane lipids but heterogeneous in size and cargo. We report a vaccine platform combining precise and replicable nanoparticle technology with immunogenic A. baumannii OMVs (Ab-OMVs). Gold nanoparticle cores coated with Ab-OMVs (Ab-NPs) induced robust IgG titers in rabbits that enhanced human neutrophil opsonophagocytic killing and passively protected against lethal A. baumannii sepsis in mice. Active Ab-NP immunization in mice protected against sepsis and pneumonia, accompanied by B cell recruitment to draining lymph nodes, activation of dendritic cell markers, improved splenic neutrophil responses, and mitigation of proinflammatory cytokine storm. Nanoparticles are an efficient and efficacious platform for OMV vaccine delivery against A. baumannii and perhaps other high-priority MDR pathogens.

Immunization with recombinant DcaP-like protein and AbOmpA revealed protections against sepsis infection of multi-drug resistant Acinetobacter baumannii ST2Pas in a C57BL/6 mouse model

BACKGROUNDS

The prevalence of infections associated with multi-drug resistant (MDR) Acinetobacter baumannii is increasing worldwide. Therefore, the introduction of effective vaccines against this bacterium seems necessary.

METHODS

AbOmpA and DcaP-like protein were selected as promising and putative immunogenic candidates based on previous in silico studies. Three formulations including AbOmpA, DcaP-like protein, and AbOmpA + DcaP-like protein were injected into C57BL/6 mice three times with Alum adjuvant. The specific production of IgG antibodies (e.g. total IgG, IgG1 and IgG2c) and cytokines (e.g. IL-4, IL-6, and IL-17A), were evaluated. LD50% of MDR A. baumannii ST2^Pas was measured using Probit's method. After the challenge with bacteria, a decrease in bacterial loads (DLs) in the lung and spleen of mice was measured. Then serum bactericidal assay was performed to determine the function of antibodies on day 42. In addition, histopathological examinations of the spleen and lung, the number of macrophage and neutrophil, as well as the rate of lymphocyte infiltration were assessed.

RESULTS

The highest level of total IgG was reported in the group immunized with DcaP-like protein on day 42. The survival rate of mice was 80% in the AbOmpA immunized group and 100% for the rest of two groups. DLs in the spleen of mice immunized with AbOmpA, DcaP-like protein, and combination form were 3.5, 3, and 3.4 Log₁₀ (CFU/g), respectively. While in the lung, the DLs were 7.5 Log₁₀ (CFU/g) for the AbOmpA group and 5 for the rest of two groups. The levels of IL-6, IL-4, and IL-17A were significantly decreased in all immunized groups after the bacterial challenge (except for IL-17A in the group of AbOmpA). The bactericidal effect of antibodies against DcaP-like protein was more effective. No histopathological damage was observed in the combination immunized group. The DcaP-like protein was more effective in neutrophil and macrophage deployment and decreased lymphocyte infiltration.

CONCLUSION

The results of immunization with AbOmpA + DcaP-like protein induced a protective reaction against the sepsis infection of MDR A. baumannii. It seems that in the future, these proteins can be considered as promising components in the development of the A. baumannii vaccine.

Acinetobacter baumannii complex-caused bloodstream infection in ICU during a 12-year period: Predicting fulminant sepsis by interpretable machine learning

BACKGROUND

Acinetobacter baumannii complex-caused bloodstream infection (ABCBSI) is a potentially fatal infection in intensive care units (ICUs). This study proposed an interpretable machine learning (ML) model to predict ABCBSI fulminant fatality.

METHODS

A retrospective study of ICU patients with ABCBSI was performed in China from 2009 to 2020. Patients were stratified into two groups: those that suffered from fulminant sepsis and died within 48 h, and those that survived for more than 48 h. The clinical score systems and ML models with Shapley additive explanation (SHAP) were used to develop the prediction models. The ML model was internally validated with five-fold cross-validation, and its performance was assessed using seven typical evaluation indices. The top 20 features ranked by the SHAP scores were also calculated.

RESULTS

Among 188 ICU patients with ABCBSI, 53 were assigned to the non-survival group and 135 to the survival group. The XGBoost model exhibited the greatest area under the receiver operating characteristic curve (AUC), which outperformed other models (logistic regression, AUC = 0.914; support vector machine, AUC = 0.895; random forest, AUC = 0.972; and naive Bayesian, AUC = 0.908) and clinical scores (Acute Physiology and Chronic Health Evaluation II (APACHE II), AUC = 0.855; Sequential Organ Failure Assessment (SOFA), AUC = 0.837). It also had a sensitivity of 0.868, a specificity of 0.970, an accuracy of 0.941, a positive predictive value of 0.920, a negative predictive value of 0.949, and an F1 score of 0.893. As well as identifying the top 12 different important predictors that contribute to early mortality, it also assessed their quantitative contribution and noteworthy thresholds.

CONCLUSION

Based on the XGBoost model, early mortality in ABCBSI is estimated to be more reliable than other models and clinical scores. The 12 most important features with corresponding thresholds were identified and more importantly, the SHAP method can be used to interpret this predictive model and support individual patient treatment strategies.

Molecular epidemiology and carbapenem resistance characteristics of Acinetobacter baumannii causing bloodstream infection from 2009 to 2018 in northwest China

Bloodstream infection (BSI) caused by Acinetobacter baumannii poses a serious threat to health and is correlated with high mortality in patients with hospital-acquired infections, so the molecular epidemiology and antimicrobial resistance characteristics of this pathogen urgently need to be explored. A. baumannii isolates from BSI patients were collected in three tertiary hospitals in northwest China from 2009 to 2018. Antimicrobial susceptibility testing was used to determine the MICs of the A. baumannii isolates. Whole-genome sequencing based on the Illumina platform was performed for molecular epidemiological analyses and acquired resistance gene screening. The efflux pump phenotype was detected by examining the influence of an efflux pump inhibitor. The expression of efflux pump genes was evaluated by RT-PCR. In total, 47 A. baumannii isolates causing BSI were collected and they presented multidrug resistance, including resistance to carbapenems. Clone complex (CC) 92 was the most prevalent with 30 isolates, among which a cluster was observed in the phylogenetic tree based on the core genome multi-locus sequence type, indicating the dissemination of a dominant clone. BSI-related A. baumannii isolates normally harbour multiple resistance determinants, of which oxacillinase genes are most common. Except for the intrinsic bla_OXA-51 family, there are some carbapenem-resistant determinants in these A. baumannii isolates, including bla_OXA-23, which is encoded within the Tn2006, Tn2008 or Tn2009 transposon structures and bla_OXA-72. The transfer of bla_OXA-72 was suggested by XerC/D site-specific recombination. The AdeABC efflux pump system contributed to carbapenem resistance in A. baumannii isolates, as evidenced by the high expression of some of its encoding genes. Both the clone dissemination and carbapenem resistance mediated by oxacillinase or efflux pumps suggest an effective strategy for hospital infection control.

Multidrug-Resistant Acinetobacter baumannii May Cause Patients to Develop Polymicrobial Bloodstream Infection

Background

The incidence of polymicrobial bloodstream infections is increasing, the clinical characteristics of polymicrobial Acinetobacter baumannii bloodstream infections (AB-BSI) are unclear, and there are no reports of polymicrobial AB-BSI in mainland China. Therefore, our objective was to identify the clinical characteristics, risk factors, and outcomes of polymicrobial AB-BSI versus monomicrobial AB-BSI.

Methods

A retrospective survey of all patients with AB-BSI from January 1, 2015, to December 31, 2019, and their clinical data were collected and analyzed by reviewing electronic medical records. All data were compared and analyzed between groups of monomicrobial and polymicrobial AB-BSI. Risk factors for polymicrobial AB-BSI were assessed using multivariable logistic regression analysis.

Results

A total of 204 patients were included, of which 39 (19.1%) were patients with polymicrobial AB-BSI. The main sources of the pathogenicity of polymicrobial Acinetobacter baumannii bloodstream infections were skin and soft tissue (38.5% vs. 16.4%, p=0.002). Resistance to piperacillin/tazobactam as an independent factor for polymicrobial AB-BSI was found in multivariate analysis. Patients with polymicrobial AB-BSI had longer hospital stays compared to those with monomicrobial AB-BSI. However, there was no significant difference in mortality between the two groups.

Conclusions

Polymicrobial AB-BSI accounted for a significant proportion among all AB-BSI, and it did not influence mortality but was related to slightly longer total hospital stays. Multidrug resistance was associated with the development of polymicrobial AB-BSI but does not directly lead to polymicrobial AB-BSI, whereas resistance to piperacillin/tazobactam was highly correlated with polymicrobial AB-BSI. Therefore, while treating A. baumannii bloodstream infections, clinicians cannot ignore the multidrug-resistant A. baumannii, especially piperacillin/tazobactam-resistant A. baumannii, which may predispose to the development of polymicrobial AB-BSI.

Place in Therapy of the Newly Available Armamentarium for Multi-Drug-Resistant Gram-Negative Pathogens: Proposal of a Prescription Algorithm

The worldwide propagation of antimicrobial resistance represents one of the biggest threats to global health and development. Multi-drug-resistant organisms (MDROs), including carbapenem-resistant non-fermenting Gram-negatives and Enterobacterales, present a heterogeneous and mutating spread. Infections by MDRO are often associated with an unfavorable outcome, especially among critically ill populations. The polymyxins represented the backbone of antibiotic regimens for Gram-negative MDROs in recent decades, but their use presents multiple pitfalls. Luckily, new agents with potent activity against MDROs have become available in recent times and more are yet to come. Now, we have the duty to make the best use of these new therapeutic tools in order not to prematurely compromise their effectiveness and at the same time improve patients’ outcomes. We reviewed the current literature on ceftazidime/avibactam, meropenem/vaborbactam and cefiderocol, focusing on antimicrobial spectrum, on the prevalence and mechanisms of resistance development and on the main in vitro and clinical experiences available so far. Subsequently, we performed a step-by-step construction of a speculative algorithm for a reasoned prescription of these new antibiotics, contemplating both empirical and targeted use. Attention was specifically posed on patients with life-risk conditions and in settings with elevated prevalence of MDRO.