Impact of healthcare-associated acquisition on community-onset Gram-negative bloodstream infection: a population-based study: healthcare-associated Gram-negative BSI

Isolation and Characterization of Colistin-Resistant Enterobacteriaceae from Foods in Two Italian Regions in the South of Italy

The emergence of colistin-resistant Enterobacteriaceae in food products is a growing concern due to the potential transfer of resistance to human pathogens. This study aimed to assess the prevalence of colistin-resistant Enterobacteriaceae in raw and ready-to-eat food samples collected from two regions of Italy (Apulia and Basilicata) and to evaluate their resistance phenotypes and genetic characteristics. A total of 1000 food samples were screened, with a prevalence of 4.4% of colistin-resistant Enterobacteriaceae. The majority of the isolates belonged to Enterobacter spp. (60%), followed by Moellerella wisconsensis, Atlantibacter hermannii, Klebsiella pneumoniae, and Escherichia coli, among others. Genomic sequencing and antimicrobial susceptibility testing revealed high levels of resistance to β-lactams, with most isolates exhibiting multidrug resistance (MDR). Notably, seven isolates harbored mcr genes (mcr-1, mcr-9, and mcr-10). Additionally, in four of them were predicted the IncHI2 plasmids, known to facilitate the spread of colistin resistance. Furthermore, 56 antimicrobial resistance genes were identified, suggesting the genetic mechanisms underlying resistance to several antibiotic classes. Virulence gene analysis showed that E. coli and other isolates carried genes linked to pathogenicity, increasing the potential risk to public health. This study emphasizes the role of food as a potential reservoir for colistin-resistant bacteria and the importance of monitoring the spread of AMR genes in foodborne pathogens.

Comparative evaluation of BacT/ALERT VIRTUO and BACTEC FX400 blood culture systems for the detection of bloodstream infections

Bloodstream infections (BSI) pose significant threats to patient health, necessitating timely and accurate diagnostics to reduce mortality and morbidity. This study aimed to evaluate the clinical performance of the BacT/ALERT VIRTUO blood culture system with FANPlus bottles compared to the BACTEC FX400 system in detecting bloodstream pathogens. A total of 1,772 blood specimens were collected from various hospital wards. Specimen selection criteria were based on clinical suspicion of bloodstream infections, ensuring the inclusion of relevant and representative patient samples. These blood samples, collected from the same suspected sepsis patients, were cultured in parallel using both the BacT/ALERT VIRTUO and BACTEC FX400 systems. The diagnostic efficiency of both systems, including detection rates, time to detection (TTD), and sensitivity across different bacterial species, was assessed. In various application scenarios, the VIRTUO system demonstrates a higher positive detection rate, whether in the intensive care unit (ICU) (8.5% vs 6.4%, P = 0.028) or in general wards. Additionally, for different types of bacteria, the TVIRTUO system exhibits superior detection rates for anaerobic bacteria (5.9% vs 3.2%, P < 0.001) and aerobic bacteria (9.1% vs 7.2%, P = 0.043). Furthermore, it boasts a shorter median TTD of 14 hours compared to 16 hours, and a higher sensitivity for Gram-positive bacteria (2.8% vs 1.6%, P < 0.001). These findings emphasize VIRTUO's effectiveness in enhancing diagnostic accuracy, achieving faster time to detection, and expanding the spectrum of detected organisms, thereby facilitating the quicker initiation of appropriate therapies, supporting precise clinical decision-making, and ultimately improving patient outcomes.IMPORTANCEOur study conducted a critical evaluation of advanced blood culture technologies for managing bloodstream infections (BSI). A distinctive strength of our research is the large sample size and the concurrent testing of the same patients with two systems, a methodology rarely achieved in other studies. BSIs present severe health threats, necessitating prompt and accurate diagnostics to mitigate morbidity and mortality. The BacT/ALERT VIRTUO system, in comparison to the BACTEC FX400 system, demonstrated superior detection capabilities, emphasizing the critical role of advanced diagnostics in clinical settings.

Is Carbapenem Therapy Necessary for the Treatment of Non-CTX-M Extended-Spectrum β-Lactamase-Producing Enterobacterales Bloodstream Infections?

BACKGROUND

Investigations into antibiotics for extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E) bloodstream infections (BSIs) have focused on blaCTX-M genes. Patient outcomes from non-CTX-M-producing ESBL-E BSIs and optimal treatment are unknown.

METHODS

A multicenter observational study investigating 500 consecutive patients with ceftriaxone-resistant Enterobacterales BSIs during 2018-2022 was conducted. Broth microdilution and whole-genome sequencing confirmed antibiotic susceptibilities and ESBL gene presence, respectively. Inverse probability weighting (IPW) using propensity scores ensured patients with non-CTX-M and CTX-M ESBL-E BSIs were similar before outcome evaluation.

RESULTS

396 patients (79.2%) were confirmed to have an ESBL-E BSI. ESBL gene family prevalence was as follows: blaCTX-M (n = 370), blaSHV (n = 16), blaOXY (n = 12), and blaVEB (n = 5). ESBL gene identification was not limited to Escherichia coli and Klebsiella species. In the IPW cohort, there was no difference in 30-day mortality or ESBL-E infection recurrence between the non-CTX-M and CTX-M groups (odds ratio [OR], 0.99; 95% confidence interval [CI], .87-1.11; P = .83 and OR, 1.10; 95% CI, .85-1.42; P = .47, respectively). In an exploratory analysis limited to the non-CTX-M group, 86% of the 21 patients who received meropenem were alive on day 30; none of the 5 patients who received piperacillin-tazobactam were alive on day 30.

CONCLUSIONS

Our findings suggest that non-CTX-M and CTX-M ESBL-E BSIs are equally concerning and associated with similar clinical outcomes. Meropenem may be associated with improved survival in patients with non-CTX-M ESBL-E BSIs, underscoring the potential benefit of comprehensive molecular diagnostics to enable early antibiotic optimization for ESBL-E BSIs beyond just blaCTX-M genes.

Novel evidence on sepsis-inducing pathogens: from laboratory to bedside

Sepsis is a life-threatening condition and a significant cause of preventable morbidity and mortality globally. Among the leading causative agents of sepsis are bacterial pathogens Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes, along with fungal pathogens of the Candida species. Here, we focus on evidence from human studies but also include in vitro and in vivo cellular and molecular evidence, exploring how bacterial and fungal pathogens are associated with bloodstream infection and sepsis. This review presents a narrative update on pathogen epidemiology, virulence factors, host factors of susceptibility, mechanisms of immunomodulation, current therapies, antibiotic resistance, and opportunities for diagnosis, prognosis, and therapeutics, through the perspective of bloodstream infection and sepsis. A list of curated novel host and pathogen factors, diagnostic and prognostic markers, and potential therapeutical targets to tackle sepsis from the research laboratory is presented. Further, we discuss the complex nature of sepsis depending on the sepsis-inducing pathogen and host susceptibility, the more common strains associated with severe pathology and how these aspects may impact in the management of the clinical presentation of sepsis.

Effectiveness of Ultraviolet-C Disinfection on Hospital-Onset Gram-Negative Rod Bloodstream Infection: A Nationwide Stepped-Wedge Time-Series Analysis

BACKGROUND

The effectiveness of enhanced terminal room cleaning with ultraviolet C (UV-C) disinfection in reducing gram-negative rod (GNR) infections has not been well evaluated. We assessed the association of implementation of UV-C disinfection systems with incidence rates of hospital-onset (HO) GNR bloodstream infection (BSI).

METHODS

We obtained information regarding UV-C use and the timing of implementation through a survey of all Veterans Health Administration (VHA) hospitals providing inpatient acute care. Episodes of HO-GNR BSI were identified between January 2010 and December 2018. Bed days of care (BDOC) was used as the denominator. Over-dispersed Poisson regression models were fitted with hospital-specific random intercept, UV-C disinfection use for each month, baseline trend, and seasonality as explanatory variables. Hospitals without UV-C use were also included to the analysis as a nonequivalent concurrent control group.

RESULTS

Among 128 VHA hospitals, 120 provided complete survey responses with 40 reporting implementations of UV-C systems. We identified 13 383 episodes of HO-GNR BSI and 24 141 378 BDOC. UV-C use was associated with a lower incidence rate of HO-GNR BSI (incidence rate ratio: 0.813; 95% confidence interval: .656-.969; P = .009). There was wide variability in the effect size of UV-C disinfection use among hospitals.

CONCLUSIONS

In this large quasi-experimental analysis within the VHA System, enhanced terminal room cleaning with UV-C disinfection was associated with an approximately 19% lower incidence of HO-GNR BSI, with wide variability in effectiveness among hospitals. Further studies are needed to identify the optimal implementation strategy to maximize the effectiveness of UV-C disinfection technology.

Diagnosis and Management of Bloodstream Infections With Rapid, Multiplexed Molecular Assays

Bloodstream infection is a major health concern, responsible for considerable morbidity and mortality across the globe. Prompt identification of the responsible pathogen in the early stages of the disease allows clinicians to implement appropriate antibiotic therapy in a timelier manner. Rapid treatment with the correct antibiotic not only improves the chances of patient survival, but also significantly reduces the length of hospital stay and associated healthcare costs. Although culture has been the gold standard and most common method for diagnosis of bloodstream pathogens, it is being enhanced or supplanted with more advanced methods, including molecular tests that can reduce the turnaround time from several days to a few hours. In this article, we describe two rapid, molecular bloodstream infection panels that identify the most common pathogens and associated genetic determinants of antibiotic resistance – the Luminex^® VERIGENE^® Gram-Positive Blood Culture Test and the VERIGENE^® Gram-Negative Blood Culture Test. We conducted a search on PubMed to retrieve articles describing the performance and impact of these tests in the clinical setting. From a total of 48 articles retrieved, we selected 15 for inclusion in this review based on the type and size of the study and so there would be minimum of three articles describing performance and three articles describing the impact post-implementation for each assay. Here we provide a comprehensive review of these publications illustrating the performance and clinical utility of these assays, demonstrating how genotypic tests can benefit diagnostic and antimicrobial stewardship efforts.

A literature survey on antimicrobial and immune-modulatory effects of butyrate revealing non-antibiotic approaches to tackle bacterial infections

The excessive prescription of antibiotics has led to an increasing number of antimicrobial resistances, posing a major public health concern. Therefore, the pharmacological research has shifted its focus to the identification of natural compounds that exhibit anti-pathogenic properties without triggering antibiotic resistance. Butyrate has received increasing attention as a promising candidate for the treatment of bacterial infections in the gastrointestinal tract, particularly when antibiotic treatment is contraindicated. This literature survey summarizes recently investigated antibacterial and immunemodulatory effects of butyrate. This survey revealed that butyrate exerts direct antimicrobial effects against distinct strains of Acinetobacter baumannii, Escherichia coli, Bacillus, and Staphylococcus species. In addition, in vitro and in vivo studies confirmed indirect antimicrobial effects of butyrate, which were exhibited via induction of host defensin production as well as by activation of innate and adaptive immune responses. Finally, the synergistic action of butyrate in combination with other antimicrobial compounds results in a striking clearance of bacterial pathogens. In conclusion, butyrate and its derivatives might be considered as promising antibacterial and immune-modulatory agents in order to tackle bacterial infections without antibiotics.

Impact of Reappraisal of Fluoroquinolone Minimum Inhibitory Concentration Susceptibility Breakpoints in Gram-Negative Bloodstream Isolates

The Clinical Laboratory Standards Institute lowered the fluoroquinolone minimum inhibitory concentration (MIC) susceptibility breakpoints for Enterobacteriaceae and glucose non-fermenting Gram-negative bacilli in January 2019. This retrospective cohort study describes the impact of this reappraisal on ciprofloxacin susceptibility overall and in patients with risk factors for antimicrobial resistance. Gram-negative bloodstream isolates collected from hospitalized adults at Prisma Health-Midlands hospitals in South Carolina, USA, from January 2010 to December 2014 were included. Matched pairs mean difference (MD) with 95% confidence intervals (CI) were calculated to examine the change in ciprofloxacin susceptibility after MIC breakpoint reappraisal. Susceptibility of Enterobacteriaceae to ciprofloxacin declined by 5.2% (95% CI: −6.6, −3.8; p < 0.001) after reappraisal. The largest impact was demonstrated among Pseudomonas aeruginosa bloodstream isolates (MD −7.8, 95% CI: −14.6, −1.1; p = 0.02) despite more conservative revision in ciprofloxacin MIC breakpoints. Among antimicrobial resistance risk factors, fluoroquinolone exposure within the previous 90 days was associated with the largest change in ciprofloxacin susceptibility (MD −9.3, 95% CI: −16.1, −2.6; p = 0.007). Reappraisal of fluoroquinolone MIC breakpoints has a variable impact on the susceptibility of bloodstream isolates by microbiology and patient population. Healthcare systems should be vigilant to systematically adopt this updated recommendation in order to optimize antimicrobial therapy in patients with bloodstream and other serious infections.

Empirical fluoroquinolones versus broad-spectrum beta-lactams for Gram-negative bloodstream infections in the absence of antimicrobial resistance risk factors

OBJECTIVES

Increasing antimicrobial resistance rates limit empirical antimicrobial treatment options for Gram-negative bloodstream infections (GN-BSI). However, antimicrobial resistance may be predicted based on patient-specific risk factors using precision medicine concepts. This retrospective, 1:2 matched cohort examined clinical outcomes in hospitalized adults without major risk factors for antimicrobial resistance receiving empirical fluoroquinolones or broad-spectrum beta-lactams (BSBL) for GN-BSI at Prisma Health-Midlands hospitals in Columbia, SC, USA from January 2010 through June 2015.

METHODS

Multivariable logistic regression was used to examine early treatment failure at 72-96 h from GN-BSI. Cox proportional hazards regression was used to examine 28-day mortality and hospital length of stay (HLOS).

RESULTS

Among 74 and 148 patients receiving empirical fluoroquinolones and BSBL for GN-BSI, respectively, median age was 68 years, 159 (72%) were women, and 152 (68%) had a urinary source of infection. Early treatment failure rates were comparable in fluoroquinolone and BSBL groups (27% vs. 30%, respectively, odds ratio 0.82, 95% confidence intervals [CI] 0.43-1.54, P = 0.53), as well as 28-day mortality (8.9% vs. 9.7%, respectively, hazards ratio [HR] 0.74, 95% CI 0.26-1.90, P = 0.54). Median HLOS was 6.1 days in the fluoroquinolone group and 7.1 days in the BSBL group (HR 0.73, 95% CI 0.54-0.99, P = 0.04). Transition from intravenous to oral therapy occurred sooner in the fluoroquinolone group than in the BSBL group (3.0 vs. 4.9 days, P < 0.001).

CONCLUSIONS

In the absence of antimicrobial resistance risk factors, fluoroquinolones provide an additional empirical treatment option to BSBL for GN-BSI. Shorter HLOS in the fluoroquinolone group may be due to earlier transition from intravenous to oral antimicrobial therapy.

Rates, predictors and mortality of community-onset bloodstream infections due to Pseudomonas aeruginosa: systematic review and meta-analysis

BACKGROUND

Pseudomonas aeruginosa is mostly a nosocomial pathogen affecting predisposed patients. However, community-onset bloodstream infections (CO-BSI) caused by this organism are not exceptional.

OBJECTIVES

To assess the predisposing factors for CO-BSI due to P. aeruginosa (CO-BSI-PA) and the impact in mortality of inappropriate empirical antimicrobial therapy.

DATA SOURCE

A systematic literature search was performed in the Medline, Embase, Cochrane Library, Scopus and Web of Science databases. Study eligibility criteria and participants: Articles published between 1 January 2002 and 31 January 2018 reporting at least of 20 adult patients with CO-BSI due to P. aeruginosa were considered.

INTERVENTION

Empiric antimicrobial therapy for CO-BSI-PA.

METHODS

A systematic review and a meta-analysis were conducted for risk factors and to evaluate if inappropriate empiric antimicrobial therapy increased mortality in CO-BSI-PA using a Mantel-Haenszel effects model.

RESULTS

Twelve studies assessing data of 1120 patients were included in the systematic review. Solid tumour (33.1%), haematologic malignancy (26.4%), neutropenia (31.7%) and previous antibiotic use (44.8%) were the most prevalent predisposing factors. Septic shock was present in 42.3% of cases, and 30-day crude mortality was 33.8%. Mortality in meta-analysis (four studies) was associated with septic shock at presentation (odds ratio, 22.31; 95% confidence interval, 3.52-141.35; p 0.001) and with inappropriate empiric antibiotic therapy (odds ratio, 1.83; 95% confidence interval, 1.12-2.98l p 0.02).

CONCLUSIONS

CO-BSI-PA mostly occurred in patients with predisposing factors and had a 30-day mortality comparable to hospital-acquired cases. Inappropriate empirical antibiotic therapy was associated with increased mortality. Appropriate identification of patients at risk for CO-BSI-PA is needed for empirical treatment decisions.

Association of 30-Day Mortality With Oral Step-Down vs Continued Intravenous Therapy in Patients Hospitalized With Enterobacteriaceae Bacteremia

IMPORTANCE

Conversion to oral therapy for Enterobacteriaceae bacteremia has the potential to improve the quality of life of patients by improving mobility, eliminating catheter-associated discomfort, decreasing the risk for noninfectious and infectious catheter-associated adverse events, and decreasing health care costs.

OBJECTIVE

To compare the association of 30-day mortality with early oral step-down therapy vs continued parenteral therapy for the treatment of Enterobacteriaceae bloodstream infections.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective multicenter cohort study included a 1:1 propensity score-matched cohort of 4967 unique patients hospitalized with monomicrobial Enterobacteriaceae bloodstream infection at 3 academic medical centers from January 1, 2008, through December 31, 2014. Eligibility criteria included appropriate source control measures, appropriate clinical response by day 5, active antibiotic therapy from day 1 until discontinuation of therapy, availability of an active oral antibiotic option, and ability to consume other oral medications or feeding. Statistical analysis was performed from March 2, 2018, to June 2, 2018.

EXPOSURES

Oral step-down therapy within the first 5 days of treatment of Enterobacteriaceae bacteremia.

MAIN OUTCOMES AND MEASURES

The main outcome was 30-day all-cause mortality.

RESULTS

Of the 2161 eligible patients, 1185 (54.8%) were male and 1075 (49.7%) were white; the median (interquartile range [IQR]) age was 59 (48-68) years. One-to-one propensity-score matching yielded 1478 patients, with 739 in each study arm. Sources of bacteremia included urine (594 patients [40.2%]), gastrointestinal tract (297 [20.1%]), central line-associated (272 [18.4%]), pulmonary (58 [3.9%]), and skin and soft tissue (41 [2.8%]). There were 97 (13.1%) deaths in the oral step-down group and 99 (13.4%) in the intravenous (IV) group within 30 days (hazard ratio [HR], 1.03; 95% CI, 0.82-1.30). There were no differences in recurrence of bacteremia within 30 days between the groups (IV, 6 [0.8%]; oral, 4 [0.5%]; HR, 0.82 [0.33-2.01]). Patients transitioned to oral step-down therapy were discharged from the hospital an average of 2 days (IQR, 1-6) sooner than patients who continued to receive IV therapy (5 days [IQR, 3-8 days] vs 7 days [IQR, 4-14 days]; P < .001).

CONCLUSIONS AND RELEVANCE

In this study, 30-day mortality was not different among hospitalized patients who received oral step-down vs continued parenteral therapy for the treatment of Enterobacteriaceae bloodstream infections. The findings suggest that transitioning to oral step-down therapy may be an effective treatment approach for patients with Enterobacteriaceae bacteremia who have received source control and demonstrated an appropriate clinical response. Early transition to oral step-down therapy may be associated with a decrease in the duration of hospital stay for patients with Enterobacteriaceae bloodstream infections.

Polymyxin derivatives NAB739 and NAB815 are more effective than polymyxin B in murine Escherichia coli pyelonephritis

Objectives

Extremely multiresistant strains of Enterobacteriaceae, such as those of Escherichia coli and Klebsiella pneumoniae, are emerging and spreading at a worrisome speed. Polymyxins (polymyxin B, colistin) are used as last-line therapy against such strains, in spite of their notable nephrotoxicity that may even require discontinuation of the therapy. We have previously developed polymyxin derivatives NAB739 and NAB815 that are better tolerated in cynomolgus monkeys than polymyxin B and are, in contrast to polymyxin B, excreted in the cynomolgus urine to a very significant degree. Here we have compared the efficacy of these NAB compounds and polymyxin B in the therapy of murine pyelonephritis caused by E. coli.

Methods

The challenge organism was a uropathogenic E. coli clinical isolate. Mice were inoculated via urethral catheterization with 5 × 108 cfu. All treatment groups consisted of 12 animals. On day 1 and day 2 post-infection, the mice were treated subcutaneously with NAB739, NAB815, polymyxin B or vehicle twice a day and on day 3 post-infection the animals were sacrificed. cfu in the kidney and bladder tissues and in the urine were determined.

Results

NAB739 reduced the bacterial burden in the kidney, urine and bladder at doses approximately 10-fold lower than those of polymyxin B. In the kidneys, the half-maximal effective dose (ED50) was 9-fold lower for NAB739 than for polymyxin B (0.24 mg/kg versus 2.1 mg/kg, respectively). NAB815 was as effective as NAB739.

Conclusions

NAB739 and NAB815 were unequivocally more effective than polymyxin B in the murine pyelonephritis model.

Evaluation of the efficacy and safety of ceftazidime/avibactam in the treatment of Gram-negative bacterial infections: a systematic review and meta-analysis

Data on the efficacy and safety of ceftazidime/avibactam (CAZ-AVI) are limited. A systematic review and meta-analysis was conducted to clarify the role of CAZ-AVI for patients with serious Gram-negative bacterial infections. The PubMed, EMBASE and Cochrane Library databases were searched for randomised controlled trials (RCTs) and cohort studies involving CAZ-AVI. Summary risk ratios (RRs) and 95% confidence intervals (CIs) were calculated using a fixed- or random-effects model. Twelve articles (4951 patients) were included, consisting of nine RCTs and three observational studies comparing CAZ-AVI with other regimens, e.g. carbapenems or colistin. CAZ-AVI showed a comparable clinical response (RR = 0.99, 95% CI 0.96-1.02; I2 = 0%) and non-inferior bacterial eradication (RR = 1.04, 95% CI 0.93-1.17; I2 = 79.1%) to carbapenems. No significant difference was detected between groups regarding mortality and adverse events. Moreover, subgroup analyses demonstrated that CAZ-AVI improved the clinical response (RR = 1.61, 95% CI 1.13-2.29) with reduced mortality (RR = 0.29, 95% CI 0.13-0.63) in patients infected by carbapenem-resistant Enterobacteriaceae versus comparators. Likewise, CAZ-AVI improved the clinical cure rate of bloodstream infections (RR = 2.11, 95% CI 1.54-2.88). An improved ability of CAZ-AVI in microbiological eradication was also detected in patients with complicated urinary tract infections (RR = 1.13, 95% CI 1.05-1.21). CAZ-AVI exhibited comparable efficacy and safety with carbapenems. Therefore, this agent might be a potential powerful agent for patients with serious Gram-negative bacterial infections.

Predicting Resistance to Piperacillin-Tazobactam, Cefepime and Meropenem in Septic Patients With Bloodstream Infection Due to Gram-Negative Bacteria

Background

Predicting antimicrobial resistance in gram-negative bacteria (GNB) could balance the need for administering appropriate empiric antibiotics while also minimizing the use of clinically unwarranted broad-spectrum agents. Our objective was to develop a practical prediction rule able to identify patients with GNB infection at low risk for resistance to piperacillin-tazobactam (PT), cefepime (CE), and meropenem (ME).

Methods

The study included adult patients with sepsis or septic shock due to bloodstream infections caused by GNB admitted between 2008 and 2015 from Barnes-Jewish Hospital. We used multivariable logistic regression analyses to describe risk factors associated with resistance to the antibiotics of interest (PT, CE, and ME). Clinical decision trees were developed using the recursive partitioning algorithm CHAID (χ2 Automatic Interaction Detection).

Results

The study included 1618 consecutive patients. Prevalence rates for resistance to PT, CE, and ME were 28.6%, 21.8%, and 8.5%, respectively. Prior antibiotic use, nursing home residence, and transfer from an outside hospital were associated with resistance to all 3 antibiotics. Resistance to ME was specifically linked with infection attributed to Pseudomonas or Acinetobacter spp. Discrimination was similar for the multivariable logistic regression and CHAID tree models, with both being better for ME than for PT and CE. Recursive partitioning algorithms separated out 2 clusters with a low probability of ME resistance and 4 with a high probability of PT, CE, and ME resistance.

Conclusions

With simple variables, clinical decision trees can be used to distinguish patients at low, intermediate, or high risk of resistance to PT, CE, and ME.

Antimicrobial Nonsusceptibility of Gram-Negative Bloodstream Isolates, Veterans Health Administration System, United States, 2003-20131

Bacteremia caused by gram-negative bacteria is associated with serious illness and death, and emergence of antimicrobial drug resistance in these bacteria is a major concern. Using national microbiology and patient data for 2003–2013 from the US Veterans Health Administration, we characterized nonsusceptibility trends of community-acquired, community-onset; healthcare-associated, community-onset; and hospital-onset bacteremia for selected gram-negative bacteria (Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, and Acinetobacter spp.). For 47,746 episodes of bacteremia, the incidence rate was 6.37 episodes/10,000 person-years for community-onset bacteremia and 4.53 episodes/10,000 patient-days for hospital-onset bacteremia. For Klebsiella spp., P. aeruginosa, and Acinetobacter spp., we observed a decreasing proportion of nonsusceptibility across nearly all antimicrobial drug classes for patients with healthcare exposure; trends for community-acquired, community-onset isolates were stable or increasing. The role of infection control and antimicrobial stewardship efforts in inpatient settings in the decrease in drug resistance rates for hospital-onset isolates needs to be determined.

New polymyxin derivatives that display improved efficacy in animal infection models as compared to polymyxin B and colistin

Polymyxin B and colistin (polymyxin E) are bactericidal pentacationic lipopeptides that act specifically on Gram-negative bacteria, first by disrupting their outermost permeability barrier, the outer membrane (OM), and then damaging the cytoplasmic membrane. The discovery of both polymyxin B and colistin was published independently by three laboratories as early as in 1947. They were subsequently used in intravenous therapy. Unfortunately, they also exhibit significant and dose-limiting nephrotoxicity. Therefore, polymyxins were reserved as agents of last-line defense. The emergence of extremely multiresistant strains has now forced clinicians to reinstate polymyxins in the therapy of severe infections. However, the current dosage regimens lead to insufficient drug concentrations in serum and clinicians have been advised to use larger doses, which further increases the risk of nephrotoxicity. Very recently, the interest in developing better tolerated and more effective polymyxins has grown. This review focuses on describing four development programs that have yielded novel derivatives that are more effective than the old polymyxins in animal infection models. Compounds from three programs are superior to the old polymyxins in the rodent lung infection model with Acinetobacter baumannii and/or Pseudomonas aeruginosa. One of them is also more effective than polymyxin B in A. baumannii mouse thigh infection. The fourth program includes compounds that are approximately tenfold more effective in Escherichia coli murine pyelonephritis than polymyxin B.

Development of Institutional Guidelines for Management of Gram-Negative Bloodstream Infections: Incorporating Local Evidence

Background: Appropriate empirical antimicrobial therapy is associated with improved outcomes of patients with Gram-negative bloodstream infections (BSI). Objective: Development of evidence-based institutional management guidelines for empirical antimicrobial therapy of Gram-negative BSI. Methods: Hospitalized adults with Gram-negative BSI in 2011-2012 at Palmetto Health hospitals in Columbia, SC, USA, were identified. Logistic regression was used to examine the association between site of infection acquisition and BSI due to Pseudomonas aeruginosa or chromosomally mediated AmpC-producing Enterobacteriaceae (CAE). Antimicrobial susceptibility rates of bloodstream isolates were stratified by site of acquisition and acute severity of illness. Retained antimicrobial regimens had predefined susceptibility rates ≥90% for noncritically ill and ≥95% for critically ill patients. Results: Among 390 patients, health care-associated (odds ratio [OR]: 3.0, 95% confidence interval [CI]: 1.5-6.3] and hospital-acquired sites of acquisition (OR: 3.7, 95% CI: 1.6-8.4) were identified as risk factors for BSI due to P aeruginosa or CAE, compared with community-acquired BSI (referent). Based on stratified bloodstream antibiogram, ceftriaxone met predefined susceptibility criteria for community-acquired BSI in noncritically ill patients (95%). Cefepime and piperacillin-tazobactam monotherapy achieved predefined susceptibility criteria in noncritically ill (95% both) and critically ill patients with health care-associated and hospital-acquired BSI (96% and 97%, respectively) and critically ill patients with community-acquired BSI (100% both). Conclusions: Incorporation of site of acquisition, local antimicrobial susceptibility rates, and acute severity of illness into institutional guidelines provides objective evidence-based approach for optimizing empirical antimicrobial therapy for Gram-negative BSI. The suggested methodology provides a framework for guideline development in other institutions.

Management of intra-abdominal infections: recommendations by the WSES 2016 consensus conference

This paper reports on the consensus conference on the management of intra-abdominal infections (IAIs) which was held on July 23, 2016, in Dublin, Ireland, as a part of the annual World Society of Emergency Surgery (WSES) meeting. This document covers all aspects of the management of IAIs. The Grading of Recommendations Assessment, Development and Evaluation recommendation is used, and this document represents the executive summary of the consensus conference findings.

Association between chronic hemodialysis and bloodstream infections caused by chromosomally mediated AmpC-producing Enterobacteriaceae

BACKGROUND

The combination of inherent antimicrobial resistance and high mortality after bloodstream infections (BSIs) caused by chromosomally mediated AmpC-producing Enterobacteriaceae (CAE) emphasizes the importance of identifying patients at risk of BSI because of these bacteria. This retrospective case-control study examines chronic hemodialysis among other risk factors for BSI caused by CAE.

METHODS

Hospitalized adults with Enterobacteriaceae BSI from January 1, 2010-June 30, 2014, at 2 large community hospitals in the Southeastern United States were identified. Multivariate logistic regression was used to examine risk factors for CAE BSI.

RESULTS

Among 831 Enterobacteriaceae bloodstream isolates, 106 (13%) met the phenotypic definition of CAE. Enterobacter spp accounted for 47% (50/106) of CAE BSIs. Chronic hemodialysis was an independent risk factor for CAE BSI (adjusted odds ratio [aOR], 2.34; 95% confidence interval [CI], 1.21-4.44). Other predictors of CAE BSI included nosocomial acquisition (aOR, 1.72; 95% CI, 1.02-2.87) and exposure to β-lactam antibiotics within the last 30 days (aOR, 2.39; 95% CI, 1.37-4.14).

CONCLUSIONS

To our knowledge, this is the first study to demonstrate an increased risk of CAE BSI in patients with end-stage renal disease undergoing chronic hemodialysis. This highlights the importance of effective infection prevention and antimicrobial stewardship interventions in hemodialysis clinics. Further studies to examine the impact of antibiotics on intestinal microbiota and rates of CAE colonization in this patient population are warranted.

Differential effect of prior β-lactams and fluoroquinolones on risk of bloodstream infections secondary to Pseudomonas aeruginosa

OBJECTIVE

This retrospective case-control study examines risk factors for bloodstream infections (BSI) due to Pseudomonas aeruginosa (PSA).

METHODS

Hospitalized adults with Gram-negative BSI at Palmetto Health from 2010 to 2015 were identified. Multivariate logistic regression was used to examine PSA BSI risk factors.

RESULTS

Seventy and 910 patients with PSA and Enterobacteriaceae BSI, respectively, were included. Prior use of β-lactams (adjusted odds ratio [aOR] 3.9, 95% confidence intervals [CI]: 2.3-6.9), but not fluoroquinolones (aOR 1.0, 95% CI: 0.4-2.2), was a risk factor for PSA BSI. Immune compromised status (aOR 3.7, 95% CI: 2.0-6.7), respiratory source (aOR 4.4, 95% CI: 2.1-8.9), and prolonged hospitalization (aOR 1.9, 95% CI: 1.1-3.5), were predictors of PSA BSI.

CONCLUSIONS

Determination of class of previously used antibiotics among other clinical variables helps identify patients at risk of PSA BSI and offers opportunities to optimize empirical antimicrobial therapy.

A cohort study of bacteremic pneumonia: The importance of antibiotic resistance and appropriate initial therapy?

Bacteremic pneumonia is usually associated with greater mortality. However, risk factors associated with hospital mortality in bacteremic pneumonia are inadequately described.The study was a retrospective cohort study, conducted in Barnes-Jewish Hospital (2008-2015). For purposes of this investigation, antibiotic susceptibility was determined according to ceftriaxone susceptibility, as ceftriaxone represents the antimicrobial agent most frequently recommended for hospitalized patients with community-acquired pneumonia as opposed to nosocomial pneumonia. Two multivariable analyses were planned: the first model included resistance to ceftriaxone as a variable, whereas the second model included the various antibiotic-resistant species (methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacteriaceae).In all, 1031 consecutive patients with bacteremic pneumonia (mortality 37.1%) were included. The most common pathogens associated with infection were S aureus (34.1%; methicillin resistance 54.0%), Enterobacteriaceae (28.0%), P aeruginosa (10.6%), anaerobic bacteria (7.3%), and Streptococcus pneumoniae (5.6%). Compared with ceftriaxone-susceptible pathogens (46.8%), ceftriaxone-resistant pathogens (53.2%) were significantly more likely to receive inappropriate initial antibiotic treatment (IIAT) (27.9% vs 7.1%; P < 0.001) and to die during hospitalization (41.5% vs 32.0%; P = 0.001). The first logistic regression analysis identified IIAT with the greatest odds ratio (OR) for mortality (OR 2.2, 95% confidence interval [CI] 1.5-3.2, P < 0.001). Other independent predictors of mortality included age, mechanical ventilation, immune suppression, prior hospitalization, prior antibiotic administration, septic shock, comorbid conditions, and severity of illness. In the second multivariable analysis that included the antibiotic-resistant species, IIAT was still associated with excess mortality, and P aeruginosa infection was identified as an independent predictor of mortality (OR 1.6, 95% CI 1.1-2.2, P = 0.047), whereas infection with ceftriaxone-resistant Enterobacteriaceae (OR 0.6, 95% CI 0.4-1.0, P = 0.050) was associated with lower mortality.More than one-third of our patients hospitalized with bacteremic pneumonia died. IIAT was identified as the most important risk factor for hospital mortality and the only risk factor amenable to potential intervention. Specific antibiotic-resistant pathogen species were also associated with mortality.

Antimicrobials: a global alliance for optimizing their rational use in intra-abdominal infections (AGORA)

Intra-abdominal infections (IAI) are an important cause of morbidity and are frequently associated with poor prognosis, particularly in high-risk patients. The cornerstones in the management of complicated IAIs are timely effective source control with appropriate antimicrobial therapy. Empiric antimicrobial therapy is important in the management of intra-abdominal infections and must be broad enough to cover all likely organisms because inappropriate initial antimicrobial therapy is associated with poor patient outcomes and the development of bacterial resistance. The overuse of antimicrobials is widely accepted as a major driver of some emerging infections (such as C. difficile), the selection of resistant pathogens in individual patients, and for the continued development of antimicrobial resistance globally. The growing emergence of multi-drug resistant organisms and the limited development of new agents available to counteract them have caused an impending crisis with alarming implications, especially with regards to Gram-negative bacteria. An international task force from 79 different countries has joined this project by sharing a document on the rational use of antimicrobials for patients with IAIs. The project has been termed AGORA (Antimicrobials: A Global Alliance for Optimizing their Rational Use in Intra-Abdominal Infections). The authors hope that AGORA, involving many of the world's leading experts, can actively raise awareness in health workers and can improve prescribing behavior in treating IAIs.

Role of newer and re-emerging older agents in the treatment of infections caused by carbapenem-resistant Enterobacteriaceae

Antimicrobial resistance has been identified by the World Health Organization as "one of the three greatest threats to human health." Gram negative bacteria in particular drive this alarming trend. Carbapenem-resistant Enterobacteriaceae (CRE) such as Escherichia coli, Klebsiella pneumoniae, and Enterobacter species are of particular importance as they are associated with poor clinical outcomes and are common causes for a variety of infections including bacteremia, urinary tract infection, intra-abdominal infections and pneumonia. CRE are difficult to treat as carbapenem resistance is often accompanied by resistance to additional drug classes. For example, CRE may be extensively drug resistant or even pandrug resistant. Unfortunately, CRE infections have increased over the past 15 y while new and effective antibiotics have not kept pace. Recently, however, new agents have become available to help treat CRE infection, and several more are under development. This article reviews the efficacy, safety, and pharmacokinetic issues around 4 emerging agents to treat CRE - ceftazidime-avibactam, fosfomycin, tigecycline, and minocycline. In addition, an overview of agents in the antibiotic pipeline - meropenem-vaborbactam, imipenem-relebactam, plazomicin, and eravacycline is provided. More established agents, such as those in the polymyxin class and aminoglycoside class (other than the pipeline agent plazomicin), are not addressed here.

The Effect of a Nationwide Infection Control Program Expansion on Hospital-Onset Gram-Negative Rod Bacteremia in 130 Veterans Health Administration Medical Centers: An Interrupted Time-Series Analysis

BACKGROUND

The Veterans Health Administration (VHA) introduced the Methicillin-Resistant Staphylococcus aureus (MRSA) Prevention Initiative in March 2007. Although the initiative has been perceived as a vertical intervention focusing on MRSA, it also expanded infection prevention and control programs and resources. We aimed to assess the horizontal effect of the initiative on hospital-onset (HO) gram-negative rod (GNR) bacteremia.

METHODS

This retrospective cohort included all patients who had HO bacteremia due to Escherichia coli, Klebsiella species, or Pseudomonas aeruginosa at 130 VHA facilities from January 2003 to December 2013. The effects were assessed using segmented linear regression with autoregressive error models, incorporating autocorrelation, immediate effect, and time before and after the initiative. Community-acquired (CA) bacteremia with same species was also analyzed as nonequivalent dependent controls.

RESULTS

A total of 11 196 patients experienced HO-GNR bacteremia during the study period. There was a significant change of slope in HO-GNR bacteremia incidence rates from before the initiative (+0.3%/month) to after (-0.4%/month) (P < .01), while CA GNR incidence rates did not significantly change (P = .08). Cumulative effect of the intervention on HO-GNR bacteremia incidence rates at the end of the study period was estimated to be -43.2% (95% confidence interval, -51.6% to -32.4%). Similar effects were observed in subgroup analyses of each species and antimicrobial susceptibility profile.

CONCLUSIONS

Within 130 VHA facilities, there was a sustained decline in HO-GNR bacteremia incidence rates after the implementation of the MRSA Prevention Initiative. As these organisms were not specifically targeted, it is likely that horizontal components of the initiative contributed to this decline.

Burden of community-onset bloodstream infections, Western Interior, British Columbia, Canada

Although community-onset bloodstream infection (BSI) is recognized as a major cause of morbidity and mortality, its epidemiology has not been well defined in non-selected populations. We conducted population-based surveillance in the Interior Health West region of British Columbia, Canada in order to determine the burden associated with community-onset BSI. A total of 1088 episodes were identified for an overall annual incidence of 117·8/100 000 of which 639 (58·7%) were healthcare-associated (HA) and 449 (41·3%) were community-associated (CA) BSIs for incidences of 69·2 and 48·6/100 000, respectively. The incidence of community-onset BSI varied by age and gender and elderly males were at the highest risk. Overall 964 (88·6%) episodes resulted in hospital admission for a median length of stay of 8 days; the total days of acute hospitalization associated with community-onset BSI was 13 530 days or 1465 days/100 000 population per year. The in-hospital mortality rate was 10·6% (102/964) and this was higher for HA-BSI (72/569, 12·7%) compared to CA-BSI (30/395, 7·6%, P = 0·014) episodes. Community-onset BSI, especially HA-BSI, is associated with a major burden of illness.

Multidrug-Resistant Gram-Negative Bacterial Infections in the Hospital Setting: Overview, Implications for Clinical Practice, and Emerging Treatment Options

The increasing prevalence of infections due to multidrug-resistant (MDR) gram-negative bacteria constitutes a serious threat to global public health due to the limited treatment options available and the historically slow pace of development of new antimicrobial agents. Infections due to MDR strains are associated with increased morbidity and mortality and prolonged hospitalization, which translates to a significant burden on healthcare systems. In particular, MDR strains of Enterobacteriaceae (especially Klebsiella pneumoniae and Escherichia coli), Pseudomonas aeruginosa, and Acinetobacter baumannii have emerged as particularly serious concerns. In the United States, MDR strains of these organisms have been reported from hospitals throughout the country and are not limited to a small subset of hospitals. Factors that have contributed to the persistence and spread of MDR gram-negative bacteria include the following: overuse of existing antimicrobial agents, which has led to the development of adaptive resistance mechanisms by bacteria; a lack of good antimicrobial stewardship such that use of multiple broad-spectrum agents has helped perpetuate the cycle of increasing resistance; and a lack of good infection control practices. The rising prevalence of infections due to MDR gram-negative bacteria presents a significant dilemma in selecting empiric antimicrobial therapy in seriously ill hospitalized patients. A prudent initial strategy is to initiate treatment with a broad-spectrum regimen pending the availability of microbiological results allowing for targeted or narrowing of therapy. Empiric therapy with newer agents that exhibit good activity against MDR gram-negative bacterial strains such as tigecycline, ceftolozane-tazobactam, ceftazidime-avibactam, and others in the development pipeline offer promising alternatives to existing agents.

Population-based epidemiology and microbiology of community-onset bloodstream infections

Bloodstream infection (BSI) is a major cause of infectious disease morbidity and mortality worldwide. While a positive blood culture is mandatory for establishment of the presence of a BSI, there are a number of determinants that must be considered for establishment of this entity. Community-onset BSIs are those that occur in outpatients or are first identified <48 h after admission to hospital, and they may be subclassified further as health care associated, when they occur in patients with significant prior health care exposure, or community associated, in other cases. The most common causes of community-onset BSI include Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. Antimicrobial-resistant organisms, including methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamase/metallo-β-lactamase/carbapenemase-producing Enterobacteriaceae, have emerged as important etiologies of community-onset BSI.

Impact of fluoroquinolone resistance in Gram-negative bloodstream infections on healthcare utilization

There has been a concerning increase in fluoroquinolone resistance among Gram-negative bloodstream isolates. This retrospective cohort study examines the implications of fluoroquinolone resistance on use of healthcare resources in patients with Gram-negative bloodstream infections (BSI). Hospitalized adults with first episodes of community-onset Gram-negative BSI from 2010 to 2012 at Palmetto Health Hospitals in Columbia, SC, USA were identified. Multivariate linear regression was used to examine risk factors for prolonged hospital length of stay (HLOS) in survivors of Gram-negative BSI. Among 474 unique patients, 384 (81%) and 90 (19%) had BSI due to fluoroquinolone-susceptible (FQ-S) and fluoroquinolone non-susceptible (FQ-NS) Gram-negative bacilli, respectively. The FQ-NS bloodstream isolates, particularly Escherichia coli, were more likely than FQ-S isolates to be multi-drug resistant (56% versus 6%, p < 0.001). Compared with patients with BSI due to FQ-S bloodstream isolates, those with FQ-NS isolates were more likely to receive inappropriate empirical antimicrobial therapy (26% versus 3%, p < 0.001), have longer mean HLOS (11.6 versus 9.3 days, p 0.03) and treatment duration with intravenous antibiotics during hospitalization (9.1 versus 7.1 days, p 0.001), and use outpatient intravenous antibiotics at hospital discharge (15% versus 8%, p 0.05). After adjustments in the multivariate model, inappropriate empirical antimicrobial therapy was an independent risk factor for prolonged HLOS in survivors of Gram-negative BSI (parameter estimate 3.65 days, 95% CI 0.43-6.86). Multi-drug resistance among FQ-NS bloodstream isolates limits both empirical and definitive antimicrobial treatment options and poses excessive burdens on the healthcare system.

Identification of Gram-Negative Bacteria and Genetic Resistance Determinants from Positive Blood Culture Broths by Use of the Verigene Gram-Negative Blood Culture Multiplex Microarray-Based Molecular Assay

Bloodstream infection is a serious condition associated with significant morbidity and mortality. The outcome of these infections can be positively affected by the early implementation of effective antibiotic therapy based on the identification of the infecting organism and genetic markers associated with antibiotic resistance. In this study, we evaluated the microarray-based Verigene Gram-negative blood culture (BC-GN) assay in the identification of 8 genus or species targets and 6 genetic resistance determinants in positive blood culture broths. A total of 1,847 blood cultures containing Gram-negative organisms were tested using the BC-GN assay. This comprised 729 prospective fresh, 781 prospective or retrospective frozen, and 337 simulated cultures representing 7 types of aerobic culture media. The results were compared to those with standard bacterial culture and biochemical identification with nucleic acid sequence confirmation of the resistance determinants. Among monomicrobial cultures, the positive percent agreement (PPA) of the BC-GN assay with the reference method was as follows; Escherichia coli, 100%; Klebsiella pneumoniae, 92.9%; Klebsiella oxytoca, 95.5%; Enterobacter spp., 99.3%; Pseudomonas aeruginosa, 98.9%; Proteus spp., 100%; Acinetobacter spp., 98.4%; and Citrobacter spp., 100%. All organism identification targets demonstrated >99.5% negative percent agreement (NPA) with the reference method. Of note, 25/26 cultures containing K. pneumoniae that were reported as not detected by the BC-GN assay were subsequently identified as Klebsiella variicola. The PPA for identification of resistance determinants was as follows; blaCTX-M, 98.9%; blaKPC, 100%; blaNDM, 96.2%; blaOXA, 94.3%; blaVIM, 100%; and blaIMP, 100%. All resistance determinant targets demonstrated >99.9% NPA. Among polymicrobial specimens, the BC-GN assay correctly identified at least one organism in 95.4% of the broths and correctly identified all organisms present in 54.5% of the broths. The sample-to-result processing and automated reading of the detection microarray results enables results within 2 h of culture positivity.

No specific time window distinguishes between community-, healthcare-, and hospital-acquired bacteremia, but they are prognostically robust

OBJECTIVE

We examined whether specific time windows after hospital admission reflected a sharp transition between community and hospital acquisition of bacteremia. We further examined whether different time windows to distinguish between community acquisition, healthcare association (HCA), and hospital acquisition influenced the results of prognostic models.

DESIGN

Population-based cohort study.

SETTING

Hospitals in 3 areas of Denmark (2.3 million inhabitants) during 2000-2011.

METHODS

We computed graphs depicting proportions of males, absence of comorbidity, microorganisms, and 30-day mortality pertaining to bacteremia 0, 1, 2, …, 30, and 31 days and later after admission. Next, we assessed whether different admission (0-1, 0-2, 0-3, 0-7 days) and HCA (30, 90 days) time windows were associated with changes in odds ratio (OR) and area under the receiver operating characteristic (ROC) curve for 30-day mortality, adjusting for sex, age, comorbidity, and microorganisms.

RESULTS

For 56,606 bacteremic episodes, no sharp transitions were detected on a specific day after admission. Among the 8 combined time windows, ORs for 30-day mortality varied from 1.30 (95% confidence interval [CI], 1.23-1.37) to 1.99 (95% CI, 1.48-2.67) for HCA and from 1.36 (95% CI, 1.24-1.50) to 2.53 (95% CI, 2.01-3.20) for hospital acquisition compared with community acquisition. Area under the ROC curve changed marginally from 0.684 (95% CI, 0.679-0.689) to 0.700 (95% CI, 0.695-0.705).

CONCLUSIONS

No time transitions unanimously distinguished between community and hospital acquisition with regard to sex, comorbidity, or microorganisms, and no difference in 30-day mortality was seen for HCA patients in relation to a 30- or 90-day time window. ORs decreased consistently in the order of hospital acquisition, HCA, and community acquisition, regardless of time window combination, and differences in area under the ROC curve were immaterial.

Bloodstream infections and central line-associated bloodstream infections

It is estimated that more than 575,000 individuals develop bloodstream infections (BSI) annually in North America, accounting for nearly 80,000 deaths. Central line-associated BSI (CLABSI) is a major contributor to the cost of health care. Although primary BSI may be seen by the surgeon, a secondary BSI is more likely to be encountered, especially CLABSI. Prompt identification of the source of infection in patients with secondary BSI is paramount. This practice allows early source control and initiation of appropriate antimicrobial therapy, with subsequent improvement in outcomes. An understanding of evidence-based preventative measures and bundles is important.

Clinical characteristics and outcome of elderly patients with community-onset bacteremia

OBJECTIVES

To evaluate characteristics and prognostic factors of community-onset bloodstream infection (Co-BSI) in elderly patients (≥65 years).

METHODS

Analysis of a prospective series of Co-BSI at a tertiary hospital (2005-2011). Predictors of 30-day mortality were established by logistic regression analysis.

RESULTS

A total of 2605 episodes of Co-BSI were identified and empirical antibiotic treatment was inappropriate in 404 (15.5%). Thirty-day mortality was 11.4% and was independently associated with age (75-84 years OR 1.9, 1.37-2.67; ≥85 OR 2.85, 1.93-4.21), previous hospitalization (OR 1.45, 1.05-2.00), a fatal underlying disease (OR 2.81, 2.10-3.76), neutropenia (OR 2.62, 1.54-4.43), absence of fever (OR 1.99, 1.26-3.12), shock (OR 7.96, 5.83-10.89), inappropriate empirical treatment (OR 1.49, 1.03-2.16), isolation of Staphylococcus aureus (methicillin-resistant OR 2.83, 1.38-5.78; methicillin-susceptible OR 3.24, 1.98-5.32), enterococci (OR 2.02, 1.14-3.59) or Enterobacteriaceae resistant to third-generation cephalosporin (3GCR-E) (OR 1.96, 1.16-3.32) and having endovascular non-catheter (OR 4.64, 2.51-8.59), abdominal (OR 3.65, 2.12-6.27), skin/soft tissue (OR 3.48, 1.90-6.37), respiratory (OR 2.80, 1.75-4.50) or unknown (OR 1.83, 1.17-2.87) source.

CONCLUSIONS

Age is a prognostic factor and appropriateness of empirical treatment is the only modifiable variable. S. aureus, enterococci and 3GCR-E may be the microorganisms with major prognostic significance; hence efforts should be made to improve their management.

Epidemiology and clinical outcomes of multidrug-resistant, gram-negative bloodstream infections in a European tertiary pediatric hospital during a 12-month period

BACKGROUND

Bloodstream infections caused by multidrug-resistant, Gram-negative (MDRGN) bacteria represent a significant cause of morbidity and mortality. Prompt diagnosis and appropriate empiric treatment are the most important determinants of patient outcome. The objective of our study was to assess the epidemiology and clinical outcome of MDRGN sepsis in a tertiary-care pediatric hospital during a 12-month period.

METHODS

It was a retrospective, observational study of MDRGN bacteremia including all patients <18 years of age, hospitalized during 2011, with documented bacteremia caused by Enterobacteriaceae or non-fermentative bacteria.

RESULTS

Overall, 136 blood cultures in 119 patients were included. The median age of patients was 1.1 years; 86.3% of patients had an underlying disease. The cumulative incidence of Gram-negative bloodstream infections was 5.4/1000 hospital admissions and the infection rate was 0.65/1000 hospital days. Most frequently isolated strains were Klebsiella pneumoniae, Escherichia coli and Pseudomonas aeruginosa; 67.6% of infections were hospital acquired. The percentage of multidrug-resistant (MDR) organisms among isolated species was 39%. The crude rate of mortality was 16% and sepsis-related mortality was 9.2%. The mortality rate among patients with an antibiotic-resistant isolate was 22.6%. Factors significantly associated with sepsis-related mortality were antibiotic resistance (odds ratio: 4.26, 95% confidence interval: 1.07-16.9) and hospital acquisition of infection (odds ratio: 1.13, 95% confidence interval: 1.05-1.22).

CONCLUSIONS

This study demonstrates the high mortality of hospital-acquired MDRGN bacteremia in children. International networks focusing on clinical management and outcomes of MDRGN in children are required. Study of novel antibiotics active against Gram-negative bacteria should include children early in the clinical trial development programs.

Characteristics of hospital-acquired and community-onset blood stream infections, South-East Austria

Purpose

The objective of this study was to compare epidemiology, causative pathogens, outcome, and levels of laboratory markers of inflammation of community-onset (i.e. community-acquired and healthcare-associated) and hospital-acquired bloodstream infection (BSI) in South-East Austria.

Methods

In this prospective cohort study, 672 patients fulfilling criteria of systemic inflammatory response syndrome with positive peripheral blood cultures (277 community-onset [192 community-acquired, 85 healthcare-associated BSI], 395 hospital-acquired) were enrolled at the Medical University of Graz, Austria from 2011 throughout 2012. Clinical, microbiological, demographic as well as outcome and laboratory data was collected.

Results

Escherichia coli followed by Staphylococcus aureus were the most frequently isolated pathogens. While Streptococcus spp. and Escherichia coli were isolated more frequently in patients with community-onset BSI, Enterococcus spp., Candida spp., Pseudomonas spp., Enterobacter spp., and coagulase-negative staphylococci were isolated more frequently among those with hospital-acquired BSI. With regard to the outcome, 30-day (82/395 vs. 31/277; p = 0.001) and 90-day mortality (106/395 vs. 35/277; p<0.001) was significantly higher among patients with hospital-acquired BSI even though these patients were significantly younger. Also, hospital-acquired BSI remained a significant predictor of mortality in multivariable analysis. At the time the blood cultures were drawn, patients with community-onset BSI had significantly higher leukocyte counts, neutrophil-leucocyte ratios as well as C-reactive protein, procalcitonin, interleukin-6 and serum creatinine levels when compared to those with hospital-acquired BSI. Patients with healthcare-associated BSI presented with significantly higher PCT and creatinine levels than those with community-acquired BSI.

Conclusions

Hospital-acquired BSI was associated with significantly higher 30- and 90-day mortality rates. Hospital-acquired BSI therefore poses an important target for the most aggressive strategies for prevention and infection control.

Classification of healthcare-associated infection: a systematic review 10 years after the first proposal

BACKGROUND

Ten years after the first proposal, a consensus definition of healthcare-associated infection (HCAI) has not been reached, preventing the development of specific treatment recommendations. A systematic review of all definitions of HCAI used in clinical studies is made.

METHODS

The search strategy focused on an HCAI definition. MEDLINE, SCOPUS and ISI Web of Knowledge were searched for articles published from earliest achievable data until November 2012. Abstracts from scientific meetings were searched for relevant abstracts along with a manual search of references from reports, earlier reviews and retrieved studies.

RESULTS

The search retrieved 49,405 references: 15,311 were duplicates and 33,828 were excluded based on title and abstract. Of the remaining 266, 43 met the inclusion criteria. The definition more frequently used was the initial proposed in 2002--in infection present at hospital admission or within 48 hours of admission in patients that fulfilled any of the following criteria: received intravenous therapy at home, wound care or specialized nursing care in the previous 30 days; attended a hospital or hemodialysis clinic or received intravenous chemotherapy in the previous 30 days; were hospitalized in an acute care hospital for ≥2 days in the previous 90 days, resided in a nursing home or long-term care facility. Additional criteria founded in other studies were: immunosuppression, active or metastatic cancer, previous radiation therapy, transfer from another care facility, elderly or physically disabled persons who need healthcare, previous submission to invasive procedures, surgery performed in the last 180 days, family member with a multi-drug resistant microorganism and recent treatment with antibiotics.

CONCLUSIONS

Based on the evidence gathered we conclude that the definition initially proposed is widely accepted. In a future revision, recent invasive procedures, hospitalization in the last year or previous antibiotic treatment should be considered for inclusion in the definition. The role of immunosuppression in the definition of HCAI still requires ongoing discussion.

Decreasing incidence rates of bacteremia: a 9-year population-based study

BACKGROUND

Numerous studies have shown that the incidence rate of bacteremia has been increasing over time. However, few studies have distinguished between community-acquired, healthcare-associated and nosocomial bacteremia.

METHODS

We conducted a population-based study among adults with first-time bacteremia in Funen County, Denmark, during 2000-2008 (N = 7786). We reported mean and annual incidence rates (per 100,000 person-years), overall and by place of acquisition. Trends were estimated using a Poisson regression model.

RESULTS

The overall incidence rate was 215.7, including 99.0 for community-acquired, 50.0 for healthcare-associated and 66.7 for nosocomial bacteremia. During 2000-2008, the overall incidence rate decreased by 23.3% from 254.1 to 198.8 (3.3% annually, p < .001), the incidence rate of community-acquired bacteremia decreased by 25.6% from 119.0 to 93.8 (3.7% annually, p < .001) and the incidence rate of nosocomial bacteremia decreased by 28.9% from 82.2 to 56.0 (4.2% annually, p < .001). The incidence rate of healthcare-associated bacteremia remained stable. The most common microorganisms were Escherichia coli (28.3%), Staphylococcus aureus (12.3%), coagulase-negative staphylococci (10.0%) and Streptococcus pneumoniae (9.1%). Regardless of place of acquisition, the proportion of bacteremias caused by enterococci increased (p < .05) and the proportion caused by coagulase-negative staphylococci decreased (p < .05).

CONCLUSIONS

The incidence rates of community-acquired and nosocomial bacteremia decreased substantially over time.

Microbial etiology and antimicrobial resistance in healthcare-associated versus community-acquired and hospital-acquired bloodstream infection in a tertiary care hospital

Infections that occur in patients with significant exposure to the nosocomial environment while they reside in the community are currently classified separately as healthcare-associated infections. In this retrospective study, conducted at Ghent University Hospital between January 1, 2009, and May 31, 2011, we compared microbial characteristics of healthcare-associated bloodstream infection (HCAB) with that of community-acquired bloodstream infection (CAB) and hospital-acquired bloodstream infection (HAB). Three hundred eighty-six pathogens isolated from patients with HCAB were compared with 141 and 605 pathogens identified in patients with CAB and HAB, respectively. HCAB was associated with a distinct pathogen profile and with an antimicrobial susceptibility pattern different from that of other categories of bloodstream infection. We conclude that the concept of HCAB provides guidance in the choice of empirical antibiotic therapy but should be translated according to local epidemiology.

Novel derivatives of polymyxins

Polymyxin B and colistin (polymyxin E) are bactericidal pentacationic lipopeptides that act specifically on Gram-negative bacteria, first by disrupting their outermost permeability barrier, the outer membrane (OM), and then damaging the cytoplasmic membrane. Both were discovered in the mid-1950s and subsequently used in intravenous therapy, but soon largely abandoned because of nephrotoxicity. The emergence of extremely multiresistant strains has now forced clinicians to reinstate them in the therapy of severe infections caused by such strains. This article reviews recent attempts to develop novel derivatives of polymyxins that exhibit less toxicity and greater potency than the existing drugs. In addition, studies of novel des-fatty acyl-polymyxin derivatives that display activity against Pseudomonas aeruginosa are included. The review also covers recent studies of derivatives that lack potent bactericidal action, but which disrupt the OM, which increases bacterial permeability to other antibiotics, facilitating their entry into the cell.

Diagnostic challenges and opportunities in older adults with infectious diseases

Infections remain a major threat to the well-being of our growing aged population. The correct and timely diagnosis of infections in older adults is increasingly important in the current age of antimicrobial resistance. Urinary tract infection, pneumonia, and bacteremia present particular challenges. In older patients with bacteremia, blood cultures have comparable yield as compared with younger patients. However, the routine triggers for ordering blood cultures may not be appropriate in older adults. In addition, resistance patterns of isolated pathogens may change with age. The main difficulties in diagnosing urinary tract infections in older adults are caused by an increased prevalence of asymptomatic bacteriuria and frequent use of urinary catheters. However, a combined noninvasive approach that includes history, physical examination, urinary dipstick testing, urine cultures, and simple blood tests can provide direction. In addition, specific guidelines for specific populations are available. In older patients suspected of bacterial pneumonia, bedside pulse oximetry and urinary antigen testing for Streptococcus pneumoniae and Legionella pneumophila provide direction for the clinician. Although infected older adults pose specific and unique diagnostic challenges, a thorough history and physical examination combined with minimally invasive testing will lead to the correct diagnosis in most older adults with infectious diseases, limiting the need for empiric antibiotics in this age group.