Acinetobacter baumannii bacteraemia in patients with haematological malignancy: a multicentre retrospective study from the Infection Working Party of Jiangsu Society of Hematology

Clinical characteristics and prognosis of bloodstream infections with carbapenem-resistant Gram-negative organisms in patients with hematological malignancies: A multicenter case-control study in China

OBJECTIVE

To investigate clinical characteristics of hematological malignancy (HM) patients with carbapenem-resistant gram-negative organism (CRO) bloodstream infections (BSI) in China, and to elucidate the prognostic risk factors of CRO BSI.

METHODS

We conducted a multicenter case-control study of 201 HM patients with CRO BSI between 2018-2020. Antimicrobial susceptibility testing and whole genome sequencing were performed for CRO isolates. Independent risk factors for 28-day crude mortality were analyzed using Cox proportional hazards regression models. The subgroups of major species were also evaluated.

RESULTS

The pathogens responsible for CRO BSI in HM patients dominated by ST11 CRKP, ST167 CREC and ST463 CRPA. Most isolates produced carbapenemases with KPC and NDM being the main. CRO isolates had resistance rates to conventional antimicrobials ranging from 55%-100% and poor susceptibility to novel antimicrobials related to carbapenemases and species. The 28-day crude mortality was 24.2%. Non-Hodgkin lymphoma, heart disease, blaKPC-2 positive, empirical antibiotic therapy with linezolid, Pitt bacteremia score >3.5 were risk factors for 28-day mortality and appropriate definitive antibiotic therapy, tigecycline-containing therapy and aminoglycoside-containing therapy were protective factors. blaKPC-2 positive in CRKP and ST463 in CRPA were associated with Pitt bacteremia score >3.5. Solid tumor and other site infections before BSI were risk factors for ST463 CRPA BSI and pulmonary infection before BSI was risk factor for KPC-KP BSI.

CONCLUSIONS

The antimicrobial resistance of CRO isolates for BSI in HM patients is critical. HM patients with CRO BSI should be treated with appropriate definitive antibiotic therapy based on early clarification of pathology and their antimicrobial susceptibility.

Characteristics of Oral Acinetobacter spp. and Evolution of Plasmid-Mediated Carbapenem Resistance in Bacteremia Patients with Hematological Malignancies

Background

Patients with hematological malignancies are more susceptible to infections, leading to a poor prognosis. Acinetobacter colonization is a risk factor for secondary bacteremia.

Methods

Antibiotic susceptibility phenotypes and genomic characteristics of 48 oral Acinetobacter spp. and one bloodstream Acinetobacter baumannii from patients with hematological malignancies were analyzed by antimicrobial susceptibility tests and whole-genome sequencing. We conducted comparative genomic analysis of oral and blood isolates from the same patient.

Results

A. baumannii was the most common (72.92%, 35/48) Acinetobacter species in oral Acinetobacter spp. isolates. Seventeen different A. baumannii sequence types were identified using the Pasteur MLST scheme; however, the dominant global clones GC1 and GC2 were not present. Among the isolates, 46 (95.8%) were carbapenem-susceptible Acinetobacter spp. One patient treated with meropenem for 15 days developed A. baumannii bacteremia 46 days after the isolation of oral A. baumannii AOR07. Oral and bloodstream isolates from the same patient were closely related to only four non-synonymous mutations on the chromosome. The bla OXA-58 gene was transferred between plasmids through XerCD-mediated recombination, leading to an elevated copy number, causing carbapenem resistance in bloodstream isolates.

Conclusion

Oral Acinetobacter spp. may cause secondary bacteremia. The amplification and transfer of bla OXA-58 in the plasmids explained the increased carbapenem resistance in the bloodstream isolate.

Prognostic Factors That Affect Mortality Patients with Acinetobacter baumannii Bloodstream Infection

Background

To evaluate the clinical features of patients with Acinetobacter baumannii bloodstream infection (BSI).

Methods

Totally 200 inpatients with Acinetobacter baumannii BSI were included, clinical features of Acinetobacter baumannii BSI inpatients between 90-day survival and 90-day mortality groups, between 30-day survival and 30-day mortality groups, between patients infected with multidrug-resistant (MDR group) and sensitive Acinetobacter baumannii (sensitive group) were analyzed. The prognostic factors of 90-day mortality were analyzed by univariate logistic regression and multivariate logistic regression. The survival curve in bloodstream infectious patients with multidrug-resistant (MDR group) and sensitive Acinetobacter baumannii (sensitive group) was analyzed by Kaplan-Meier analysis.

Results

The 90-day mortality patients had significantly higher carbapenem-resistant bacterial infection and critical care unit (ICU) admission. The 90-day and 30-day mortality groups showed higher C-reactive protein (CRP) and serum creatinine (Scr) levels and lower red blood cells (RBC) and albumin (ALB) levels than their survival counterparts, respectively. Critical surgery, ICU admission and delayed antibiotic treatment were independently prognostic risk predictors for 90-day mortality in Acinetobacter baumannii BSI patients, while critical surgery and diabetes were independently prognostic risk predictors for 90-day mortality in carbapenem-resistant Acinetobacter baumannii BSI patients. Compared with sensitive group, MDR group showed significantly longer ICU and whole hospital stay, lower levels of lymphocytes, RBC, hemoglobin, lactate dehydrogenase and ALB, higher frequency of infection originating from the skin and skin structure. Moreover, patients in the MDR group had a significantly worse overall survival than the sensitive group.

Conclusion

We identified the prognostic factors of Acinetobacter baumannii BSI and carbapenem-resistant Acinetobacter baumannii BSI patients. Critical surgery, ICU admission, delayed antibiotic treatment or diabetes were significantly associated with the mortality of those patients. Moreover, aggressive measures to control MDR Acinetobacter baumannii could lead to improved outcomes.

Strong Homology Between Colonizing and Bloodstream Carbapenem-Resistant Acinetobacter Spp.: Implications for Empiric Antibiotic Therapy in Hematological Patients

Objective

This study aimed to assess the impact of colonization status on the outcomes of Acinetobacter spp. bloodstream infection (BSI) and investigate the homology and within-host evolution between colonizing and bloodstream carbapenem-resistant Acinetobacter spp. (CRA) to inform antibiotic therapeutic decisions.

Methods

We analyzed clinical outcomes of 46 hematological patients with Acinetobacter spp. BSI and performed whole-genome sequencing on the remaining CRA isolates.

Results

Among the patients, 39.1% (n=18) had prior Acinetobacter spp. colonization. Colonized patients had higher rates of polymicrobial BSI (50.0% vs 21.4%, P=0.044) and CRA BSI (72.2% vs 17.9%, P<0.001), resulting in elevated inflammatory markers and increased 30-day mortality. Each of the eight pairs of the remaining respiratory colonizing and bloodstream CRA strains belonged to the same genomospecies. Each pair exhibited definitive agreement in at least 21 of the 22 most representative antibiotic susceptibility tests. The minimum spanning tree based on multilocus sequence typing (MLST) and phylogenetic trees based on MLST and single nucleotide polymorphism (SNP) all indicated that each pair shared the same minimum branch. Very few non-synonymous SNPs in genic regions were identified during the transition from respiratory colonization to bloodstream infection, with minimal changes in virulence genes. Homology analysis suggested that CRA BSI originated from colonizing isolates in the respiratory tract.

Conclusion

Strict infection control measures are needed to manage Acinetobacter spp. colonisation in hematological patients. Appropriate empirical therapy can be administered for suspected CRA BSI based on the antimicrobial minimum inhibitory concentration of CRA colonising the respiratory tract.

Acinetobacter spp. bloodstream infection in hematological patients: a 10-year single-center study

PURPOSE

This study investigated the clinical and antimicrobial characteristics of Acinetobacter spp. bloodstream infection (BSI) in hematological patients. Risk factors for 30-day mortality and carbapenem-resistant Acinetobacter spp. (CRA) BSI acquisition were also identified.

METHODS

We reviewed forty hematological patients with Acinetobacter spp. BSI in a large Chinese blood disease hospital between 2013 and 2022. The remaining CRA isolates were subjected to whole-genome sequencing.

RESULTS

The 30-day mortality rate was high at 35%. Hematological patients with Acinetobacter spp. BSI often presented with severe conditions and co-infections at multiple sites. All strains were colistin-susceptible and 40.0% were CR. Multivariate analysis identified several risk factors associated with CRA BSI acquisition, including previous exposure to carbapenems within 30 days and CRA colonization. Very severe aplastic anaemia, tetracycline-resistant Acinetobacter spp. BSI, and unresolved neutropenia after infection were closely associated with 30-day mortality. Non-survivors often presented with higher median PCT and CRP levels and severe complications, such as intracranial infection, cardiac dysfunction, respiratory failure, and severe sepsis or septic shock. Our study also identified inappropriate empirical antibiotic therapy as an independent predictor of 30-day mortality (OR: 11.234, 95% CI: 1.261-20.086, P = 0.030). This study was the first to report A. oleivorans as a human pathogen, and to identify its unique oxacillinase, OXA-325.

CONCLUSION

An environment-originated non-pathogenic species can become pathogenic when the body's immunity is compromised. Our results also highlighted the importance of improving neutropenia after infection, treating severe organ dysfunction, and administering appropriate empirical antibiotic therapy to reduce mortality in this patient population.

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.

Distribution and Antibiotic Resistance Analysis of Blood Culture Pathogens in a Tertiary Care Hospital in China in the Past Four Years

Purpose

This study aimed to investigate the antibiotic resistance patterns and clinical distribution of blood culture-positive isolates at Suining Central Hospital between 2018 and 2021. The findings of this study can provide a basis for ensuring rational and effective use of antibiotic therapy in clinical settings.

Methods

This retrospective study analyzed the data of 3660 non-repeating strains that tested positive for clinical blood culture, collected from the microbiology laboratory of Suining Central Hospital between January 2018 and December 2021. The identification of bacterial species and their antibiotic resistance patterns were analyzed.

Results

The study found that 76.7% of the bacterial strains identified were Gram-negative bacteria, while 23.3% were Gram-positive bacteria. Escherichia coli (44.8%), Klebsiella spp. (19.2%), Staphylococcus aureus (9.2%), Enterococcus spp. (5.3%), and Enterobacter spp. were the top five bacterial ratios observed. These bacteria were detected most frequently in the Digestion Center, intensive care unit (ICU), Neurology Center, Urology Department, and Hematology Department. Among the Staphylococcus spp., methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MRCNS) were detected at rates of 39.3% and 71.8%, respectively. However, no vancomycin- or linezolid-resistant staphylococci were identified. Enterococcus faecalis showed higher susceptibility to most antibiotic than Enterococcus faecium, except for tetracycline. The resistance rates of E. coli and Klebsiella spp. to meropenem and imipenem were low, but the resistance rates for other antibiotic were above 40%.

Conclusion

The results of this study show a rising incidence of bacterial antibiotic resistance in positive blood culture specimens at Suining Central Hospital. Clinicians should carefully consider the importance of blood culture antibiotic susceptibility testing to ensure effective treatment. The Department of Microbiology at Suining Central Hospital should regularly analyze the distribution of pathogenic bacteria and antibiotic resistance in blood cultures to ensure the most effective treatment possible.

A systematic review and meta-analysis for risk factor profiles in patients with resistant Acinetobacter baumannii infection relative to control patients

BACKGROUND

Acinetobacter baumannii is a major cause of nosocomial infections and high mortality rates. Evaluation of risk factors for such resistant infections may aid surveillance and diagnostic initiatives, as well as, can be crucial in early and appropriate antibiotic therapy.

OBJECTIVE

To identify the risk factors in patients with resistant A. baumannii infection with respect to controls.

METHODS

Prospective or retrospective cohort and case-control studies reporting the risk factors for resistant A. baumannii infection were collected through two data sources, MEDLINE/PubMed and OVID/Embase. Studies published in the English language were included while animal studies were excluded. The Newcastle-Ottawa Scale was used to assess the quality of studies. The odds ratio of developing antibiotic resistance in patients with A. baumannii infection was pooled using a random-effect model.

RESULTS

The results are based on 38 studies with 60878 participants (6394 cases and 54484 controls). A total of 28, 14, 25, and 11 risk factors were identified for multi-drug resistant (MDRAB), extensive-drug resistant (XDRAB), carbapenem-resistant (CRAB) and imipenem resistant A. baumannii infection (IRAB), respectively. In the MDRAB infection group, exposure to carbapenem (OR 5.51; 95% CI: 3.88-7.81) and tracheostomy (OR 5.01; 95% CI: 2.12-11.84) were identified with maximal pool odd's ratio. While previous use of amikacin (OR 4.94; 95% CI: 1.89-12.90) and exposure to carbapenem (OR 4.91; 95% CI: 2.65-9.10) were the foremost factors associated with developing CRAB infection. Further analysis revealed, mechanical ventilation (OR 7.21; 95% CI: 3.79-13.71) and ICU stay (OR 5.88; 95% CI: 3.27-10.57) as the most significant factors for XDRAB infection.

CONCLUSION

The exposure of carbapenem, amikacin (previous) and mechanical ventilation were the most significant risk factors for multidrug, extensive-drug, and carbapenem resistance in patients with A. baumannii infection respectively. These findings may guide to control and prevent resistant infections by identifying the patients at higher risk of developing resistance.

Effects of Inappropriate Administration of Empirical Antibiotics on Mortality in Adults With Bacteraemia: Systematic Review and Meta-Analysis

Introduction

Bloodstream infections are associated with high mortality rates and contribute substantially to healthcare costs, but a consensus on the prognostic benefits of appropriate empirical antimicrobial therapy (EAT) for bacteraemia is lacking.

Methods

We performed a systematic search of the PubMed, Cochrane Library, and Embase databases through July 2021. Studies comparing the mortality rates of patients receiving appropriate and inappropriate EAT were considered eligible. The quality of the included studies was assessed using Joanna Briggs Institute checklists.

Results

We ultimately assessed 198 studies of 89,962 total patients. The pooled odds ratio (OR) for the prognostic impacts of inappropriate EAT was 2.06 (P < 0.001), and the funnel plot was symmetrically distributed. Among subgroups without between-study heterogeneity (I² = 0%), those of patients with severe sepsis and septic shock (OR, 2.14), Pitt bacteraemia scores of ≥4 (OR, 1.88), cirrhosis (OR, 2.56), older age (OR, 1.78), and community-onset/acquired Enterobacteriaceae bacteraemia infection (OR, 2.53) indicated a significant effect of inappropriate EAT on mortality. The pooled adjusted OR of 125 studies using multivariable analyses for the effects of inappropriate EAT on mortality was 2.02 (P < 0.001), and the subgroups with low heterogeneity (I² < 25%) exhibiting significant effects of inappropriate EAT were those of patients with vascular catheter infections (adjusted OR, 2.40), pneumonia (adjusted OR, 2.72), or Enterobacteriaceae bacteraemia (adjusted OR, 4.35). Notably, the pooled univariable and multivariable analyses were consistent in revealing the negligible impacts of inappropriate EAT on the subgroups of patients with urinary tract infections and Enterobacter bacteraemia.

Conclusion

Although the current evidence is insufficient to demonstrate the benefits of prompt EAT in specific bacteraemic populations, we indicated that inappropriate EAT is associated with unfavorable mortality outcomes overall and in numerous subgroups. Prospective studies designed to test these specific populations are needed to ensure reliable conclusions.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier: CRD42021270274.

The Threat of Carbapenem-Resistant Gram-Negative Bacteria in Patients with Hematological Malignancies: Unignorable Respiratory Non-Fermentative Bacteria-Derived Bloodstream Infections

Background

Carbapenem-resistant Gram-negative bacteria (CRGNB) bloodstream infection (BSI) pose a significant threat to the prognosis of hematologic malignancies (HM) patients. Understanding the distribution of pathogenic bacteria, changes in carbapenem-resistant trends, risk factors for CRGNB infections, and exploring the early detection measures can help reduce mortality.

Methods

We conducted a multicenter retrospective study of Gram-negative bacteria (GNB) BSI in patients with HM in three university-affiliated hospitals in Hunan Province, China, from January 2010 to December 2020. Demographic and clinical data were collected from the hospital electronic medical records system.

Results

CRGNB caused 138 (15.3%) of 902 GNB BSI. The detection rate of CRGNB increased from 6.4% in 2010–2012 to 35.4% in 2019–2020. The 7-day mortality rate was significantly higher in patients with CRGNB BSI than in patients with carbapenem-susceptible Gram-negative bacteria (CSGNB) BSI [31.9% (44/138) vs 9.7% (74/764), P < 0.001], and the mortality rate in patients with carbapenem-resistant non-fermenting bacteria (CRNFB) bloodstream infections was generally higher than that of carbapenem-resistant Enterobacteriaceae (CRE). Urinary catheter (OR, 2.814; CI=1.395–5.680; P=0.004) and prior exposure to carbapenem (OR, 4.372; CI=2.881–6.635; P<0.001) were independent risk factors for CRGNB BSI. Analysis of co-infections showed that 50%–85% of patients with CRGNB BSI had pulmonary infections, sputum culture results suggested that sputum culture positivity rate was as high as 57.1%–66.7% in patients with carbapenem-resistant Acinetobacter baumannii (CRAB) and Stenotrophomonas maltophilia BSI, and the results of antimicrobial susceptibility testing of sputum cultures were consistent with the blood cultures.

Conclusion

Carbapenem resistance has dramatically increased in HM patients with GNB BSI in recent years and is associated with a worse outcome, especially for non-fermenting bacteria. In high-risk patients, early screening of the respiratory tract specimens may help to detect CRNFB colonization and protect patients from breakthrough BSI.

Infections Due to Acinetobacter baumannii-calcoaceticus Complex: Escalation of Antimicrobial Resistance and Evolving Treatment Options

Bacteria within the genus Acinetobacter (principally A. baumannii-calcoaceticus complex [ABC]) are gram-negative coccobacilli that most often cause infections in nosocomial settings. Community-acquired infections are rare, but may occur in patients with comorbidities, advanced age, diabetes mellitus, chronic lung or renal disease, malignancy, or impaired immunity. Most common sites of infections include blood stream, skin/soft-tissue/surgical wounds, ventilator-associated pneumonia, orthopaedic or neurosurgical procedures, and urinary tract. Acinetobacter species are intrinsically resistant to multiple antimicrobials, and have a remarkable ability to acquire new resistance determinants via plasmids, transposons, integrons, and resistance islands. Since the 1990s, antimicrobial resistance (AMR) has escalated dramatically among ABC. Global spread of multidrug-resistant (MDR)-ABC strains reflects dissemination of a few clones between hospitals, geographic regions, and continents; excessive antibiotic use amplifies this spread. Many isolates are resistant to all antimicrobials except colistimethate sodium and tetracyclines (minocycline or tigecycline); some infections are untreatable with existing antimicrobial agents. AMR poses a serious threat to effectively treat or prevent ABC infections. Strategies to curtail environmental colonization with MDR-ABC require aggressive infection-control efforts and cohorting of infected patients. Thoughtful antibiotic strategies are essential to limit the spread of MDR-ABC. Optimal therapy will likely require combination antimicrobial therapy with existing antibiotics as well as development of novel antibiotic classes.

Adverse clinical outcomes associated with carbapenem-resistant Acinetobacter (CRA) infections: a systematic review and meta-analysis

Background

Carbapenem-resistant Acinetobacter (CRA) infections have been associated with increased morbidity and mortality in hospitalized patients. This systematic review and meta-analysis aimed to quantify the association between CRA infections and adverse clinical outcomes.

Methods

Three databases (i.e. PubMed, EMBASE and Scopus) were searched for epidemiological studies that compared mortality, severe sepsis or shock, or bacteraemia among adult inpatients with CRA infections and those with carbapenem-susceptible Acinetobacter (CSA) infections. The pooled ORs for the three outcomes were estimated using the inverse variance heterogeneity model.

Results

Thirty-four studies were included. Patients with CRA infections had higher odds of mortality (31 studies, OR = 2.10, 95% CI: 1.58–2.79, I²=60.6%) and severe sepsis or septic shock (7 studies, OR = 1.51, 95% CI: 1.09–2.09, I²=0%) compared with CSA-infected patients. There was no difference in the odds of bacteraemia (four studies, OR = 1.39, 95% CI: 0.79–2.46, I²=38.1%). CRA-infected patients presented with worse comorbidity at admission (e.g. APACHE score) (eight studies, standardized mean difference = 0.25, 95% CI: −0.01 to 0.52) and had lower frequency of appropriate antibiotic therapy. Results were consistent when pooling 16 study-adjusted risk estimates for mortality. There was no difference in risk of mortality from CRA infection when compared across geographical regions, country income, median year of enrolment and day of mortality from infection onset.

Conclusions

CRA-infected patients had worse clinical outcomes. This might be due to delay in appropriate antibiotic therapy, patients being sicker at admission and CRA strains potentially being more virulent than CSA strains. Improving appropriateness of antibiotic therapy in CRA-infected patients could reduce adverse clinical outcomes.

Antibiotic resistance in the patient with cancer: Escalating challenges and paths forward

Infection is the second leading cause of death in patients with cancer. Loss of efficacy in antibiotics due to antibiotic resistance in bacteria is an urgent threat against the continuing success of cancer therapy. In this review, the authors focus on recent updates on the impact of antibiotic resistance in the cancer setting, particularly on the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.). This review highlights the health and financial impact of antibiotic resistance in patients with cancer. Furthermore, the authors recommend measures to control the emergence of antibiotic resistance, highlighting the risk factors associated with cancer care. A lack of data in the etiology of infections, specifically in oncology patients in United States, is identified as a concern, and the authors advocate for a centralized and specialized surveillance system for patients with cancer to predict and prevent the emergence of antibiotic resistance. Finding better ways to predict, prevent, and treat antibiotic-resistant infections will have a major positive impact on the care of those with cancer.

Evolution of Acinetobacter baumannii in Clinical Bacteremia Patients

Introduction

Colonization of the respiratory tract by Acinetobacter baumannii has been established as an independent risk factor for bacteremia. However, within-host evolution of A. baumannii in bacteremia has not been extensively investigated.

Methods

We performed whole-genome sequencing to discover the evolutionary characteristics that accompany the transition from respiratory tract carriage to bloodstream infection in three patients with A. baumannii bacteremia.

Results

Within-host genetic diversity was identified. A total of 21 single nucleotide variants (SNVs) were detected. Genic and intergenic evolution occurred particularly in secretion system, DNA recombination, and cell motility genes. Intergenic SNVs occurred more frequently compared to synonymous and non-synonymous SNVs, which indicated potential transcription or translation regulation. Non-synonymous mutations mostly occurred during the transition from respiratory tract carriage to bloodstream infection. Isolates of clonal complex 208 (CC208) had lower substitution rate with approximately 10⁻⁶ nucleotide substitutions per site year⁻¹, compared with non-CC208 isolates (approximately 10⁻⁵). We found evidence for the occurrence of recombination in one patient. A total of 259 genes were found to be gained or lost during the within-host evolution, and 231 genes were only detected in one patient. Gene function annotation results suggested that most genes (71/259) were related to replication, recombination, and repair. Universal bloodstream specific genes were not found in all three patients, and only one putative membrane protein related gene was lost in two patients.

Conclusion

Our results indicated that within-host evolution of A. baumannii bacteremia was driven by mutations, gene content changes, and limited effect of recombination. Gene content diversity between different patients was identified, which suggested interplay of both host and pathogen factors in within-host genetic diversity. Secretion system-related genes showed higher frequency of genomic variations during the within-host evolution. Our findings enhanced our understanding of within-host evolution of A. baumannii bacteremia and provided a framework for discovering novel genomic changes and pathogenicity genes important for bacteremia, which will be validated in future studies.

In vivo fitness of carbapenem-resistant Acinetobacter baumannii strains in murine infection is associated with treatment failure in human infections

OBJECTIVES

Mortality among patients with carbapenem-resistant Acinetobacter baumannii (CRAB) infections varies between studies. We examined whether in vivo fitness of CRAB strains is associated with clinical outcomes in patients with CRAB infections.

METHODS

Isolates were collected from patients enrolled in the AIDA trial with hospital-acquired pneumonia, bloodstream infections and/or urinary tract infections caused by CRAB. The primary outcome was 14-day clinical failure, defined as failure to meet all criteria: alive; haemodynamically stable; improved or stable Sequential Organ Failure Assessment (SOFA) score; improved or stable oxygenation; and microbiological cure of bacteraemia. The secondary outcome was 14-day mortality. We tested in vivo growth using a neutropenic murine thigh infection model. Fitness was defined based on the CFU count 24 hours after injection of an inoculum of 10⁵ CFU. We used mixed-effects logistic regression to test the association between fitness and the two outcomes.

RESULTS

The sample included 266 patients; 215 (80.8%) experienced clinical failure. CRAB fitness ranged from 5.23 to 10.08 log CFU/g. The odds of clinical failure increased by 62% for every 1-log CFU/g increase in fitness (OR 1.62, 95% CI 1.04-2.52). After adjusting for age, Charlson score, SOFA score and acquisition in the intensive care unit, fitness remained significant (adjusted OR 1.63, 95% CI 1.03-2.59). CRAB fitness had a similar effect on 14-day mortailty, although the association was not statistically significant (OR 1.56, 95% CI 0.95-2.57). It became significant after adjusting for age, Charlson score, SOFA score and recent surgery (adjusted OR 1.88, 95% CI 1.09-3.25).

CONCLUSIONS

In vivo CRAB fitness was associated with clinical failure in patients with CRAB infection.

5-Hydroxymethylfurfural inhibits Acinetobacter baumannii biofilms: an in vitro study

The present study was aimed to investigate the antibiofilm activity of 5-hydroxymethylfurfural against Acinetobacter baumanni and Vellar estuary isolates v3 (Acinetobacter nosocomialis). The biofilm inhibitory concentration (BIC) of 5HMF against A. baumannii and v3 (A. nosocomialis) was found to be 100 µg/ml) exhibited non-bactericidal concentration-dependent antibiofilm activities against Acinetobacter species. The present study found that 5HMF treatment is very effective in the initial stage of A. baumannii biofilms and it significantly disrupted the mature biofilms. Moreover, 5HMF treatment inhibited the extracellular polymeric substances (EPS), including polysaccharides and proteins production. Results from gene expression and in vitro assays further demonstrated the 5HMF treatment downregulated the expression of bfmR, bap, csuA/B, ompA and katE virulence genes, which consistently affects biofilm formation and its mediated virulence property. The present study suggests that 5HMF unveil its antibiofilm activity by interfering initial biofilm formation and suppressing the virulence regulator genes in A. baumannii. Further studies are required to explore the 5HMF mode of action responsible for the antibiofilm activity.

Development and Validation of a Model for Predicting the Risk of Death in Patients with Acinetobacter baumannii Infection: A Retrospective Study

Purpose

This study aimed to develop and validate a personalized prediction model of death risk in patients with Acinetobacter baumannii (A. baumannii) infection and thus guide clinical research and support clinical decision-making.

Patients and Methods

The development group is comprised of 350 patients with A. baumannii infection admitted between January 2013 and December 2015 in The First Affiliated Hospital of Anhui Medical University. Further, 272 patients in the validation group were admitted between January 2016 and December 2018. The univariate and multivariate logistic regression analyses were used to determine the independent risk factors for death with A. baumannii infection. The nomogram prediction model was established based on the regression coefficients. The discrimination of the proposed prediction model was evaluated using the area under the curve (AUC) of the receiver operating characteristic (ROC) curves and decision curve analysis (DCA). The calibration diagram was used to evaluate the calibration degree of this model.

Results

The infectious source, carbapenem-resistant A. baumannii (CRAB), hypoalbuminemia, Charlson comorbidity index (CCI), and mechanical ventilation (MV) were independent risk factors for death. The AUC of the ROC curve of the two groups was 0.768 and 0.792, respectively. The net income was higher when the probability was between 30% and 80%, showing a strong discrimination capacity of the proposed model. The calibration curve swung around the 45° oblique line, indicating a high degree of calibration.

Conclusion

The proposed model helped predict the risk of death from A. baumannii infection, improve the early identification of patients with a higher risk of death, and guide clinical treatment.

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Infections Due to Carbapenem-Resistant Bacteria in Patients With Hematologic Malignancies

In developed countries, hematological malignancies (HM) account for 8 to 10% of cancers diagnosed annually and one-third of patients with HM (HMP) are expected to die from their disease. The former wide spectrum “magic bullet,” imipenem, has been ousted by the emergence of carbapenem resistant (CR) pathogens. In endemic areas, infections with CR-bacteria occur in vulnerable patients, notably in HMP, who suffer from high mortality related to infectious complications. In this work, we reviewed epidemiologic and clinical factors associated with CR-infections in adult HMP and data on CR-related mortality and antibiotic treatments in this population. We found that resistance profile of strains involved in HMP infections, mainly bacteremia, reflect local epidemiology. Significant risk factors for infections with CR-bacteria include sex male, age around 50 years old, acute leukemia, selvage chemotherapy, neutropenia, and digestive colonization by CR-bacteria. Mortality rate is high in HMP infected with CR-Enterobacteriaceae, more particularly in case of acute myeloid leukemia and unresolved neutropenia, due to inappropriate empiric management and delayed administration of targeted antibiotics, such as tigecycline, colistin, or new associations of active drugs. Thus, we developed an algorithm for clinicians, assessing the incremental risk for CR-bacterial infection occurrence and mortality in febrile HMP, to guide decisions related to empirical therapeutic strategies.

Identification of New Peptide Biomarkers for Bacterial Bloodstream Infection

PURPOSE

Due to a lack of effective early diagnostic measures, new diagnostic methods for bacterial bloodstream infections (BSIs) are urgently needed. A protein-peptide profiling approach can be used to identify novel diagnostic biomarkers of BSIs.

EXPERIMENTAL DESIGN

In this study, MALDI-TOF MS and nano-LC/ESI-MS/MS are used to analyze serum peptides. In addition, GO and network analyses are conducted as a means of analyzing these potential protein markers. Finally, the potential biomarkers are verified in independent clinical samples via ELISA.

RESULTS

m/z 1533.8, 2794.3, 3597.3, 5007.3, and 7816.7 reveal an identical trend; the intensity of m/z 1533.8, 2794.3, and 3597.3 are higher in the infection group relative to controls, whereas the intensity of m/z 5007.3 and 7816.7 are lower in the infection group. Four peaks are successfully identified including ITIH4, KNG1, SAA2, and C3. GO and network analyses find these proteins to form an interaction network, which may be correlated with BSI. ELISA results indicate that ITIH4, KNG1, and SAA2 are effective in differentiating infected from normal control group and the febrile group.

CONCLUSIONS AND CLINICAL RELEVANCE

These biomarkers have the potential to offer new insights into the signaling networks underlying the development and progression of BSI.

Inhibitory effect of α-mangostin on Acinetobacter baumannii biofilms - an in vitro study

The present study was designed to investigate the anti-biofilm potential of alpha-mangostin (α-MG) against Acinetobacter baumannii (AB). The biofilm inhibitory concentration (BIC) of α-MG against AB was found to be 2 μg ml^-1. α-MG (0.5, 1 and 2 μg ml^-1) exhibited non-bactericidal concentration-dependent anti-biofilm activities against AB. However, α-MG failed to disintegrate the mature biofilms of AB even at a 10-fold increased concentration from its BIC. Results from qRT-PCR and in vitro bioassays further demonstrated that α-MG downregulated the expression of bfmR, pgaA, pgaC, csuA/B, ompA, bap, katE, and sodB genes, which correspondingly affects biofilm formation and its associated virulence traits. The present study suggests that α-MG exerts its anti-biofilm property by interrupting initial biofilm formation and the cell-to-cell signaling mechanism of AB. Additional studies are required to understand the mode of action responsible for the anti-biofilm property.

Good tolerability of high dose colistin-based therapy in patients with haematological malignancies

PURPOSE

Colistin is usually the only drug fully active against multi-drug resistant Gram-negative bacteria, but its nephrotoxicity might limit its use. Recent pharmacokinetic/pharmacodynamic data suggest that high dose of colistin, preceded by a loading dose, are needed to maximize its antibacterial effect. The aim of this study was to determine the safety of high doses colistin, in haematology population.

METHODS

A retrospective review of haematology patients who received high dose colistin-based therapy in years 2011-2016 was performed. Nephrotoxicity was assessed using RIFLE criteria.

RESULTS

Thirty patients who received 38 courses of colistin were included in the study. Colistin was always administered together with other antibiotics. Colistin was well tolerated, with one case of neurological toxicity and one of cutaneous reaction. There were 22 (58%) treatment cycles without any nephrotoxicity, even though during 16 of these cycles other nephrotoxic drugs were administered. Severe (injury or failure) renal toxicity occurred during 6 (16%) treatment courses, requiring colistin discontinuation in 2 patients and colistin dose reduction in 1. Poorer renal function at baseline and younger age were the only variables associated with increased renal toxicity (p = 0.011 and p = 0.031, respectively). Overall mortality was 18% (7/38) and 29% (11/38) at 7 and 30 days after the treatment onset.

CONCLUSIONS

In adult haematology population, high dose colistin therapy is safe and efficacious, despite high frequency of concomitant nephrotoxic treatment.