Clinical Features and Risk Factors for Development of Breakthrough Gram-Negative Bacteremia during Carbapenem Therapy

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.

Risk factors of Carbapenem-resistant Enterobacterales intestinal colonization for subsequent infections in hematological patients: a retrospective case-control study

Objective

Infections caused by Carbapenem-resistant Enterobacterales (CRE) have high treatment costs, high mortality and few effective therapeutic agents. This study aimed to determine the risk factors for progression from intestinal colonization to infection in hematological patients and the risk factors for 30-day mortality in infected patients.

Methods

A retrospective case-control study was conducted in the Department of Hematology at Shandong Provincial Hospital affiliated to Shandong First Medical University from April 2018 to April 2022. Patients who developed subsequent infections were identified as the case group by electronic medical record query of patients with a positive rectal screen for CRE colonization, and patients who did not develop subsequent infections were identified as the control group by stratified random sampling. Univariate analysis and logistic regression analysis determined risk factors for developing CRE infection and risk factors for mortality in CRE-infected patients.

Results

Eleven hematological patients in the study developed subsequent infections. The overall 30-day mortality rate for the 44 hematological patients in the case-control study was 11.4% (5/44). Mortality was higher in the case group than in the control group (36.5 vs. 3.0%, P = 0.0026), and septic shock was an independent risk factor for death (P = 0.024). Univariate analysis showed that risk factors for developing infections were non-steroidal immunosuppressants, serum albumin levels, and days of hospitalization. In multivariable logistic regression analysis, immunosuppressants [odds ratio (OR), 19.132; 95% confidence interval (CI), 1.349-271.420; P = 0.029] and serum albumin levels (OR, 0.817; 95% CI, 0.668-0.999; P = 0.049) were independent risk factors for developing infections.

Conclusion

Our findings suggest that septic shock increases mortality in CRE-infected hematological patients. Hematological patients with CRE colonization using immunosuppressive agents and reduced serum albumin are more likely to progress to CRE infection. This study may help clinicians prevent the onset of infection early and take measures to reduce mortality rates.

Global mapping of antibiotic resistance rates among clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

INTRODUCTION

Infections caused by Stenotrophomonas maltophilia are clinically important due to its intrinsic resistance to a broad range of antibiotics. Therefore, selecting the most appropriate antibiotic to treat S. maltophilia infection is a major challenge.

AIM

The current meta-analysis aimed to investigate the global prevalence of antibiotic resistance among S. maltophilia isolates to the develop more effective therapeutic strategies.

METHOD

A systematic literature search was performed using the appropriate search syntax after searching Pubmed, Embase, Web of Science and Scopus databases (May 2023). Statistical analysis was performed using Pooled and the random effects model in R and the metafor package. A total of 11,438 articles were retrieved. After a thorough evaluation, 289 studies were finally eligible for inclusion in this systematic review and meta-analysis.

RESULT

Present analysis indicated that the highest incidences of resistance were associated with doripenem (97%), cefoxitin (96%), imipenem and cefuroxime (95%), ampicillin (94%), ceftriaxone (92%), aztreonam (91%) and meropenem (90%) which resistance to Carbapenems is intrinsic. The lowest resistance rates were documented for minocycline (3%), cefiderocol (4%). The global resistance rate to TMP-SMX remained constant in two periods before and after 2010 (14.4% vs. 14.6%). A significant increase in resistance to tigecycline and ceftolozane/tazobactam was observed before and after 2010.

CONCLUSIONS

Minocycline and cefiderocol can be considered the preferred treatment options due to low resistance rates, although regional differences in resistance rates to other antibiotics should be considered. The low global prevalence of resistance to TMP-SMX as a first-line treatment for S. maltophilia suggests that it remains an effective treatment option.

Risk factors for bacteremia and mortality due to multidrug-resistant Acinetobacter baumannii: a retrospective study

This research aimed to determine the relationships between the risk factors for nosocomial multidrug-resistant Acinetobacter baumannii (MDRAB) bacteremia and associated mortality. We analyzed 144 patients treated for A. baumannii bacteremia, including 120 patients with MDRAB bacteremia, from March 2015 to March 2020, in this retrospective study. The overall bacteremia-related mortality rate was 48.6%. The mortality rates were 25.0% and 53.3% for non-MDRAB and MDRAB bacteremia, respectively. Risk factors for the development of MDRAB bacteremia were prior use of cephalosporins [odds ratio (OR): 8.62; P < .001], carbapenems (OR: 15.04; P < .001), or quinolones (OR: 5.02; P = .040); indwelling urinary catheters (OR: 21.38; P < .001); and respiratory tract as the source of bacteremia (OR: 75.33; P < .001). Patients with elective surgeries were inclined to develop non-MDRAB bacteremia (OR: 0.45; P = .029). High scores in the Acute Physiology and Chronic Health Evaluation II (OR: 1.321; P < .001) and Sequential Organ Failure Assessment (OR: 1.326; P < .001) were risk factors for mortality from MDRAB infection. In summary, higher mortality rates occur in patients with MDRAB bacteremia, and risk factors include prior use of cephalosporins, carbapenems, or quinolones. Urinary catheters and the respiratory tract as sources of the infection increase the risk of MDRAB bacteremia.

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.

Does Emerging Carbapenem Resistance in Acinetobacter baumannii Increase the Case Fatality Rate? Systematic Review and Meta-Analysis

BACKGROUND

In the era of rising carbapenem resistance, we aimed to investigate the change in mortality rate and positivity of carbapenemase genes in Acinetobacter baumannii.

METHODS

Preferred Reporting Items for Systematic Review (PRISMA) guidelines were adopted in this systematic review. Our literature search included the Cochrane Library, Pubmed, Scopus, Web of Science, Medline, Tubitak TR Dizin, and Harman databases for studies dating back from 2003 to 2023 reporting bloodstream A. baumannii infections in Türkiye. A simple linear regression model was used to determine the association between resistance, mortality, and time.

RESULTS

A total of 1717 studies were identified through a literature search, and 21 articles were selected based on the availability of the data regarding mortality and resistance rate (four articles) or the molecular epidemiology of carbapenem-resistant A. baumannii (17 articles) in Türkiye. From 2007 to 2018, the carbapenem resistance rate increased (p = 0.025). The OXA-23 and OXA-58 positivities were inversely correlated (p = 0.025).

CONCLUSIONS

Despite the emergence of carbapenem resistance, mortality did not increase in parallel, which may be due to improved medical advancements or the fitness cost of bacteria upon prolonged antimicrobial exposure. Therefore, we suggest further global research with the foresight to assess clonal relatedness that might affect the carbapenem resistance rate.

Follow-up Blood Cultures in Gram-negative Bacteremia: How Do They Impact Outcomes?

Introduction

Several studies have questioned the utility of obtaining follow-up blood cultures in Gram-negative bacteremia, but the impact of this practice on clinical outcomes is not fully understood.

Methods

A retrospective cohort study of adult patients admitted with Gram-negative bacteremia over a two year period, to compare outcomes in those with and without follow-up blood cultures obtained. Data collected included demographics, comorbidities and presumed source of bacteremia. White blood cell count and presence of fever or hemodynamic compromise on the day of follow-up blood culture were recorded. The primary objective was to compare 30-day mortality between the two groups. Secondary objectives included comparing 30-day readmission rate, hospital length of stay and antibiotics duration.

Results

Of 482 included patients, 321 (66.6%) had follow-up blood cultures. 96% of follow-up blood cultures were negative. Persistent bacteremia occurred in 9 patients. There was no significant difference in 30-day mortality between those with and without follow-up blood cultures (2.9% and 2.7% respectively, P > 0.999), and no difference in 30-day readmission rate (21.4% and 23.4% respectively, P = 0.704). Patients with follow-up blood cultures had longer hospital length of stay (7 days vs 5 days, P < 0.001), and longer mean antibiotic duration (14 days vs 11 days, P < 0.001).

Conclusion

Obtaining follow-up blood cultures in Gram-negative bacteremia had no impact on 30-day mortality or 30-day readmission rates. It was associated with longer length of stay and antibiotic duration. We found this practice to be low yield and its routine use may be of questionable value.

A Novel Risk Predictive Scoring Model for Predicting Subsequent Infection After Carbapenem-Resistant Gram-Negative Bacteria Colonization in Hematological Malignancy Patients

Background

This study investigated the high-risk factors associated with the increased vulnerability for subsequent clinical CR-GNB infection in carbapenem-resistant Gram-negative bacteria (CR-GNB)-colonized hematological malignancy (HM) patients and built a statistical model to predict subsequent infection.

Method

All adult HM patients with positive rectoanal swabs culture for CR-GNB between January 2018 and June 2020 were prospectively followed to assess for any subsequent CR-GNB infections and to investigate the risk factors and clinical features of subsequent infection.

Results

A total of 392 HM patients were enrolled. Of them, 46.7% developed a subsequent clinical CR-GNB infection, with 42 (10.7%) cases of confirmed infection and 141 (36%) cases of clinically diagnosed infection. Klebsiella pneumoniae was the dominant species. The overall mortality rate of patients colonized and infected with CR-GNB was 8.6% and 43.7%. A multivariate analysis showed that remission induction chemotherapy and the duration of agranulocytosis, mucositis, and hypoalbuminemia were significant predictors of subsequent infection after CR-GNB colonization. According to our novel risk-predictive scoring model, the high-risk group were >3 times more likely to develop a subsequent infection in comparison with the low-risk group.

Conclusion

Our risk-predictive scoring model can early and accurately predict a subsequent CR-GNB infection in HM patients with CR-GNB colonization. The early administration of CR-GNB-targeted empirical therapy in the high-risk group is strongly recommended to decrease their mortality.

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.

Carbapenem use in critically ill patients

PURPOSE OF REVIEW

To review available data on carbapenem use in ICU. Carbapenem is a broad spectrum well tolerated antibiotic family that keep an excellent activity to extended spectrum β-lactamases and AmpC hyperproducer and in susceptible Pseudomonas aeruginosa and Acinetobacter baumannii. It becomes a drug of choice for empirical therapy of suspected sepsis in known or presumably known ESBLE carriers.

RECENT FINDINGS

Carbapenems remained the drug of choice for severe ESBLE infections. In severe critically ill patients, high off-label dose is necessary especially in patients with sepsis and glomerular hyperfiltration. Nevertheless, large spectrum of carbapenems leads to initial overuse. The increase in the overall consumption in the past years with lack of systematic re-evaluation observed is responsible of and carbapenem-selection pressure that contribute to the increase of carbapenem-resistant enterobacteriaceae, A. Baumannii and P. Aeruginosa in ICUs.

SUMMARY

Carbapenems remained a cornerstone of antibiotic therapy of severe infections. Emerging carbapenem resistance is related to the increase of carbapenem consumption. High doses are recommended for early therapy followed by systematic reevaluation on a daily basis with shift to narrow spectrum antimicrobials if possible and early stopping rules.

Prospective multi-center evaluation on risk factors, clinical characteristics and outcomes due to carbapenem resistance in Acinetobacter baumannii complex bacteraemia: experience from the Chinese Antimicrobial Resistance Surveillance of Nosocomial Infections (CARES) Network

Introduction. Increasing evidence demonstrates unfavourable outcomes in bloodstream infections (BSI) due to the carbapenem-resistant Acinetobacter baumannii complex (CRAB).Aim. To investigate the differences in risk factors, clinical characteristics and outcomes in patients with A. baumannii complex BSI stratified by carbapenem resistance, a prospective multi-center study was conducted.Methodology. Information was collected in a predefined form. A total of 317 cases was included for comparison between CRAB BSI vs. carbapenem-susceptible A. baumannii complex (CSAB) BSI. Among these cases, 229 cases were defined as CRAB BSI and 88 cases as CSAB BSI.Results. Univariable analysis showed that male gender, underlying neurologic disease, prior carbapenems exposure, intensive care unit (ICU) stay, presence of central venous catheter, endotracheal intubation, tracheotomy, Foley catheter, nasogastric intubation, lower respiratory tract infections and catheter-related infections were more prevalent in CRAB BSI. Only male gender, prior carbapenems exposure and presence of endotracheal intubation persisted as independent risk factors for acquiring CRAB BSI. Patients with CRAB BSI displayed unfavourable outcomes characterized by failure of pathogen clearance, continuous fever, disease aggravation and higher incidence of 30-day all-cause mortality. Multivariate analysis demonstrated carbapenem resistance as an independent risk factor for 30-day all-cause mortality.Conclusion. Our findings reveal the epidemiological differences between CRAB BSI and CSAB BSI in a Chinese cohort. Our data suggest that carbapenem resistance has a significant impact on mortality for patients with A. baumannii complex BSI, further strengthening the importance of active prevention and control strategies for the spread of CRAB in Chinese hospitals.

Risk factors for and clinical outcomes of carbapenem non-susceptible gram negative bacilli bacteremia in patients with acute myelogenous leukemia

BACKGROUND

Carbapenem is frequently used when gram negative bacilli (GNB) bacteremia is detected especially in neutropenic patients. Consequently, appropriate treatment could be delayed in GNB bacteremia cases involving organisms which are not susceptible to carbapenem (carba-NS), resulting in a poor clinical outcomes. Here, we explored risk factors for carba-NS GNB bacteremia and its clinical outcomes in patients with acute myelogenous leukemia (AML) that underwent chemotherapy.

METHODS

We reviewed all GNB bacteremia cases that occurred during induction or consolidation chemotherapy, over a 15-year period, in a tertiary-care hospital.

RESULTS

Among 489 GNB bacteremia cases from 324 patients, 45 (9.2%) were carba-NS and 444 (90.8%) were carbapenem susceptible GNB. Independent risk factors for carba-NS GNB bacteremia were: carbapenem use at bacteremia onset (adjusted odds ratio [aOR]: 91.2; 95% confidence interval [95%CI]: 29.3-284.1; P < 0.001); isolation of carbapenem-resistant Acinetobacter baumannii (aOR: 19.4, 95%CI: 3.4-112.5; P = 0.001) in the prior year; and days from chemotherapy to GNB bacteremia (aOR: 1.1 per day, 95%CI: 1.1-1.2; P < 0.001). Carba-NS bacteremia was independently associated with in-hospital mortality (aOR: 6.6, 95%CI: 3.0-14.8; P < 0.001).

CONSLUSION

Carba-NS organisms should be considered for antibiotic selection in AML patients having these risk factors.

Breakthrough bloodstream infections in critically ill non-neutropenic patients: higher incidence and better survival than non-breakthrough infections

Introduction. Breakthrough bloodstream infections (BSIs) are rare among non-neutropenic patients.Aim. Our goal was to determine the risk factors associated with development of breakthrough BSIs among critically ill non-neutropenic patients and its role in mortality.Methodology. During a 24-month period (August 2016 to July 2018), all BSIs among non-neutropenic patients hospitalized at the University General Hospital of Patras, Greece, were included. Antimicrobial resistance of isolates was interpreted according to EUCAST guidelines. BSIs were considered as breakthrough when blood cultures yielded a pathogen in a patient who, for at least the previous 72 h, had been receiving at least one antibiotic to which the isolated microorganism was susceptible.Results. Among 217 episodes of BSI, 118 (54.4 %) developed a breakthrough infection. Primary BSIs predominated (101; 46.5 %), followed by catheter-related BSIs (56; 25.8 %). Gram-negative bacteria represented the most common pathogens isolated (157; 72.4 %), followed by Gram-positive bacteria (36; 16.6 %) and fungi (36; 16.6 %). Factors independently associated with the development of breakthrough BSIs were immunosuppressive therapy, obesity (body mass index ≥30 kg m^{- 2}), infection by Gram-positive bacteria, noradrenaline dose during 24 h from BSI onset, prior use of colistin and antifungal treatment. Overall 14-day mortality was 23.0 % (50 patients). Multivariate analysis revealed noradrenaline dose during 24 h from BSI onset as an independent predictor of mortality, while appropriate empiric antimicrobial treatment and breakthrough BSI were identified as predictors of good prognosis.Conclusion. Breakthrough BSIs were common among critically ill non-neutropenic patients and these patients were associated with better survival because they were de facto receiving appropriate antibiotics.

Antibiotics with activity against intestinal anaerobes and the hazard of acquired colonization with ceftriaxone-resistant Gram-negative pathogens in ICU patients: a propensity score-based analysis

Background

Intestinal colonization resistance is mainly exerted by commensal anaerobes.

Objectives

To assess whether exposure to non-carbapenem antibiotics with activity against intestinal anaerobes (namely, piperacillin/tazobactam, amoxicillin/clavulanate and metronidazole) may promote the acquisition of gut colonization with ceftriaxone-resistant Gram-negative bacteria (CFR-GNB) in ICU patients.

Patients and methods

All patients with a first stay >3 days in a single surgical ICU over a 30 month period were retrospectively included. Rectal carriage of CFR-GNB (i.e. ESBL-producing Enterobacteriaceae, AmpC-hyperproducing Enterobacteriaceae, Pseudomonas aeruginosa, Stenotrophomonas maltophilia and CFR Acinetobacter baumannii) was routinely screened for at admission then weekly. The impact of anti-anaerobe antibiotics was investigated in propensity score (PS)-matched cohorts of patients exposed and not exposed to these drugs and through PS-based inverse probability of treatment weighting on the whole study cohort, treating in-ICU death or discharge as competing risks for CFR-GNB acquisition.

Results

Among the 352 included patients [median ICU stay 16 (9–30) days, in-ICU mortality 12.2%], 120 (34.1%) acquired one or more CFR-GNB, mostly AmpC-hyperproducing Enterobacteriaceae (17.6%) and P. aeruginosa (14.8%). Exposure to anti-anaerobe antibiotics was the main predictor of CFR-GNB acquisition in both the PS-matched cohorts [adjusted HR (aHR) 3.92, 95% CI 1.12–13.7, P = 0.03] and the whole study cohort (aHR 4.30, 95% CI 1.46–12.63, P = 0.01). Exposure to other antimicrobials—especially ceftriaxone and imipenem/meropenem—exerted no independent impact on the likelihood of CFR-GNB acquisition.

Conclusions

Exposure to non-carbapenem antibiotics with activity against intestinal anaerobes may predispose to CFR-GNB acquisition in ICU patients. Restricting the use of these drugs appears to be an antibiotic stewardship opportunity.

Clinical experience with tigecycline in the treatment of hospital-acquired pneumonia caused by multidrug resistant Acinetobacter baumannii

Background

Tigecycline, with broad in vitro antibacterial activity, has been widely used off-label for nosocomial pneumonia caused by multi-drug resistant Acinetobacter baumannii (MDRAB). However, many concerns have been raised about the efficacy of tigecycline treatment as the inconsistent results from previous clinical studies.

Methods

This retrospective study evaluated the outcome of adult patients with monomicrobial MDRAB nosocomial pneumonia treated with tigecycline between 2015 and 2017. Results.

A total of 77 patients was eligible for this study, and the overall clinical success and 30-day survival rates were 70.03 and 70.13%, respectively, however, the microbiological eradication rate was relatively low (48%). Multivariate analysis indicated that shorter duration of tigecycline use associated with increased clinical failure, whereas higher CURB65 scores, mechanical ventilation and tigecycline resistant to MDRAB have significant association with 30-day mortality.

Conclusions

Our results suggest that tigecycline is one of the potential choices for the treatment of hospital-acquired pneumonia caused by MDRAB, especially with a MIC≤2 mg/L. In addition, a longer duration of tigecycline treatment may be required to insure better clinical outcomes.

Cluster analysis to define distinct clinical phenotypes among septic patients with bloodstream infections

Prior attempts at identifying outcome determinants associated with bloodstream infection have employed a priori determined classification schemes based on readily identifiable microbiology, infection site, and patient characteristics. We hypothesized that even amongst this heterogeneous population, clinically relevant groupings can be described that transcend old a priori classifications.We applied cluster analysis to variables from three domains: patient characteristics, acuity of illness/clinical presentation and infection characteristics. We validated our clusters based on both content validity and predictive validity.Among 3715 patients with bloodstream infections from Barnes-Jewish Hospital (2008-2015), the most stable cluster arrangement occurred with the formation of 4 clusters. This clustering arrangement resulted in an approximately uniform distribution of the population: Cluster One "Surgical Outside Hospital Transfers" (21.5%), Cluster Two "Functional Immunocompromised Patients" (27.9%), Cluster Three "Women with Skin and Urinary Tract Infection" (28.7%) and Cluster Four "Acutely Sick Pneumonia" (21.8%). Staphylococcus aureus distributed primarily to Clusters Three (40%) and Four (25%), while nonfermenting Gram-negative bacteria grouped mainly in Clusters Two and Four (31% and 30%). More than half of the pneumonia cases occurred in Cluster Four. Clusters One and Two contained 33% and 31% respectively of the individuals receiving inappropriate antibiotic administration. Mortality was greatest for Cluster Four (33.8%, 27.4%, 19.2%, 44.6%; P < .001), while Cluster One patients were most likely to be discharged to a nursing home.Our results support the potential for machine learning methods to identify homogenous groupings in infectious diseases that transcend old a priori classifications. These methods may allow new clinical phenotypes to be identified potentially improving the severity staging and development of new treatments for complex infectious diseases.

Risk factors for acquisition and mortality of multidrug-resistant Acinetobacter baumannii bacteremia: A retrospective study from a Chinese hospital

Bloodstream infection caused by Acinetobacter baumannii has become a major clinical concern, especially multidrug-resistant A baumannii (MDRAB). The aim of this study was to identify the risk factors of nosocomial acquired MDRAB bacteremia and to determine the risk factors related to the mortality of patients with MDRAB bacteremia. Patients with nosocomial acquired A baumannii bacteremia were enrolled between January, 2013 and December, 2017 at the First Affiliated Hospital, School of Medicine, Zhejiang University. Medical records were reviewed, and the clinical and microbial characteristics were collected. Among the 338 patients suffering from A baumannii bacteremia, 274 patients were infected with MDRAB bacteremia. Bacteremia-related mortality was 46.4% for the overall sample; 56.2% for MDRAB bacteremia patients, 4.7% for non-MDRAB bacteremia patients. The identified risk factors for developing MDRAB bacteremia were previous exposure to carbapenems [odds ratio (OR) 5.78, P = .005] and penicillins+β-lactamase inhibitors (OR 4.29, P = .009). Primary bacteremia tended to develop non-MDR bacteremia (OR 0.10, P = .002). The risk factors for MDRAB bacteremia-related mortality were old age (OR 1.02, P = .036), a high Pitt bacteremia score (OR 1.32, P < .001), bacteremia occurring after severe pneumonia (OR 8.66, P < .001), while catheter-related infection (OR 0.47, P = .049) and operations for treating infection (OR 0.51, P = .043) may have a better outcome. Patients with MDRAB had a higher mortality rate. Patients with previous carbapenems and penicillins+β-lactamase inhibitor exposure are at an increased risk of MDRAB bacteremia, whereas patients with primary bacteremia tended to develop non-MDR bacteremia. The risk factors for MDRAB bacteremia-related mortality were old age, a high Pitt bacteremia score, and bacteremia occurring after severe pneumonia, whereas catheter-related infection and operations for the treatment of infection may have a better outcome.

Current time-to-positivity of blood cultures in febrile neutropenia: a tool to be used in stewardship de-escalation strategies

OBJECTIVES

We aimed to describe the current time-to-positivity (TTP) of blood cultures in individuals with onco-haematological diseases with febrile neutropenia. We assessed the probability of having a multidrug-resistant Gram-negative bacilli (MDR-GNB) bloodstream infection (BSI) 24 h after cultures were taken, to use this information for antibiotic de-escalation strategies.

METHODS

BSI episodes were prospectively collected (2003-2017). When a patient experienced more than one BSI, only one episode was randomly chosen. Time elapsed from the beginning of incubation to a positive reading was observed; TTP was recorded when the first bottle had a positive result.

RESULTS

Of the 850 patient-unique episodes, 323 (38%) occurred in acute leukaemia, 185 (21.8%) in non-Hodgkin's lymphoma and 144 (16.9%) in solid neoplasms. Coagulase-negative staphylococci (225; 26.5%), Escherichia coli (207; 26.1%), Pseudomonas aeruginosa (136; 16%), Enterococcus spp. (81; 9.5%) and Klebsiella pneumoniae (67; 7.9%), were the most frequent microorganisms isolated. MDR-GNB were documented in 126 (14.8%) episodes. Median TTP was 12 h (interquartile range 9-16.5 h). Within the first 24 h, 92.1% of blood cultures were positive (783/850). No MDR-GNB was positive over 24 h. Of the 67 (7.9%) episodes with a TTP ≥24 h, 25 (37.3%) occurred in patients who were already receiving active antibiotics against the isolated pathogen. Most common isolations with TTP ≥24 h were coagulase-negative staphylococci, candidaemia and a group of anaerobic GNB.

CONCLUSIONS

Currently, the vast majority of BSI in individuals with onco-haematological diseases with febrile neutropenia have a TTP <24 h, including all episodes caused by MDR-GNB. Our results support reassessing empiric antibiotic treatment in neutropenic patients at 24 h, to apply antibiotic stewardship de-escalation strategies.

Clinical predictors of Stenotrophomonas maltophilia bacteremia in adult patients with hematologic malignancy

Stenotrophomonas maltophilia (SM) has emerged as an important nosocomial pathogen with high morbidity and mortality. Because of its unique antimicrobial susceptibility pattern, appropriate antimicrobial therapy for SM bacteremia is still challenging, especially in immunocompromised patients. The present study was performed to assess clinical predictors of SM bacteremia in adult patients with hematologic malignancy. From 2006 through 2016, a case-control study was performed at a tertiary-care hospital. Case patients were defined as SM bacteremia in patients with hematologic malignancy. Date- and location-matched controls were selected from among patients with gram-negative bacteremia (GNB) other than SM. A total of 118 cases of SM bacteremia were identified and compared to 118 controls. While pneumonia was the most common source of SM bacteremia, centralline-associated infection was most common in the controls. The overall 30-day mortality rate of cases with SM bacteremia was significantly higher than that of the controls (61.0 and 32.2%, respectively; P < 0.001). A multivariable analysis showed that polymicrobial infection, previous SM isolation, the number of antibiotics previously used ≥ 3, and breakthrough bacteremia during carbapenem therapy were significantly associated with SM bacteremia (all P < 0.01). Previous use of trimethoprim/sulfamethoxazole (TMP/SMX) was negatively association with SM bacteremia (P = 0.002). Our data suggest that SM is becoming a significant pathogen in patients with hematologic malignancy. Several clinical predictors of SM bacteremia can be used for appropriate antimicrobial therapy in hematologic patients with suspected GNB.

Multicenter Study of Clinical Features of Breakthrough Acinetobacter Bacteremia during Carbapenem Therapy

Breakthrough Acinetobacter bacteremia during carbapenem therapy is not uncommon, and it creates therapeutic dilemmas for clinicians. This study was conducted to evaluate the clinical and microbiological characteristics of breakthrough Acinetobacter bacteremia during carbapenem therapy and to assess the efficacy of various antimicrobial therapies. We analyzed 100 adults who developed breakthrough Acinetobacter bacteremia during carbapenem therapy at 4 medical centers over a 6-year period. Their 30-day mortality rate was 57.0%, and the carbapenem resistance rate of their isolates was 87.0%. Among patients with carbapenem-resistant Acinetobacter bacteremia, breakthrough bacteremia during carbapenem therapy was associated with a significantly higher 14-day mortality (51.7% versus 37.4%, respectively; P = 0.025 by bivariate analysis) and a higher 30-day mortality (P = 0.037 by log rank test of survival analysis) than in the nonbreakthrough group. For the treatment of breakthrough Acinetobacter bacteremia during carbapenem therapy, tigecycline-based therapy was associated with a significantly higher 30-day mortality (80.0%) than those with continued carbapenem therapy (52.5%) and colistin-based therapy (57.9%) by survival analysis (P = 0.047 and 0.045 by log rank test, respectively). Cox regression controlling for confounders, including severity of illness indices, demonstrated that treatment with tigecycline-based therapy for breakthrough Acinetobacter bacteremia was an independent predictor of 30-day mortality (hazard ratio, 3.659; 95% confidence interval, 1.794 to 7.465; P < 0.001). Patients with breakthrough Acinetobacter bacteremia during carbapenem therapy posed a high mortality rate. Tigecycline should be used cautiously for the treatment of breakthrough Acinetobacter bacteremia that develops during carbapenem therapy.