Risk Factors and Outcomes for Intestinal Carriage of AmpC-Hyperproducing Enterobacteriaceae in Intensive Care Unit Patients

Gut colonization with multidrug resistant organisms in the intensive care unit: a systematic review and meta-analysis

BACKGROUND

Gut colonization with multidrug-resistant organisms (MDRO) frequently precedes infection among patients in the intensive care unit (ICU), although the dynamics of colonization are not completely understood. We performed a systematic review and meta-analysis of ICU studies which described the cumulative incidence and rates of MDRO gut acquisition.

METHODS

We systematically searched PubMed, Embase, and Web of Science for studies published from 2010 to 2023 reporting on gut acquisition of MDRO in the ICU. MDRO were defined as multidrug resistant non-Pseudomonas Gram-negative bacteria (NP-GN), Pseudomonas spp., and vancomycin-resistant Enterococcus (VRE). We included observational studies which obtained perianal or rectal swabs at ICU admission (within 48 h) and at one or more subsequent timepoints. Our primary outcome was the incidence rate of gut acquisition of MDRO, defined as any MDRO newly detected after ICU admission (i.e., not present at baseline) for all patient-time at risk. The study was registered with PROSPERO, CRD42023481569.

RESULTS

Of 482 studies initially identified, 14 studies with 37,305 patients met criteria for inclusion. The pooled incidence of gut acquisition of MDRO during ICU hospitalization was 5% (range: 1-43%) with a pooled incidence rate of 12.2 (95% CI 8.1-18.6) per 1000 patient-days. Median time to acquisition ranged from 4 to 26 days after ICU admission. Results were similar for NP-GN and Pseudomonas spp., with insufficient data to assess VRE. Among six studies which provided sufficient data to perform curve fitting, there was a quasi-linear increase in gut MDRO colonization of 1.41% per day which was stable through 30 days of ICU hospitalization (R2 = 0.50, p < 0.01).

CONCLUSIONS

Acquisition of gut MDRO was common in the ICU and increases with days spent in ICU through 30 days of follow-up. These data may guide future interventions seeking to prevent gut acquisition of MDRO in the ICU.

The problem of multi-resistance in gram-negative bacilli in intensive care units: Treatment and prevention strategies

The rise of infections caused by multi-resistant gram-negative bacilli (MR-GNB), which includes carbapenems, represents one of the major current challenges worldwide. These MR-GNB include extended spectrum β-lactamase-producing Enterobacterales, derepressed AmpC-producing or carbapenemase-producing Enterobacterales as well as non-fermenting Gram-negative bacilli such as Pseudomonas aeruginosa or Acinetobacter baumannii. P. aeruginosa predominantly exhibits other resistance mechanisms different to β-lactamases such as expulsion pumps or loss of porins. A. baumannii frequently presents several of these resistance mechanisms. Mortality is high especially if empirical treatment is inadequate. In this review, treatment strategies are revised, describing the tools available to identify patients in whom empirical antibiotic treatment would be justified to cover MR-GNB, the importance of optimizing the administration of these antibiotics, as well as prevention strategies to avoid its spread from patients colonized or infected by a MR-GNB.

Empiric Treatment in HAP/VAP: “Don’t You Want to Take a Leap of Faith?”

Ventilator-associated pneumonia is a frequent cause of ICU-acquired infections. These infections are associated with high morbidity and mortality. The increase in antibiotic resistance, particularly among Gram-negative bacilli, makes the choice of empiric antibiotic therapy complex for physicians. Multidrug-resistant organisms (MDROs) related infections are associated with a high risk of initial therapeutic inadequacy. It is, therefore, necessary to quickly identify the bacterial species involved and their susceptibility to antibiotics. New diagnostic tools have recently been commercialized to assist in the management of these infections. Moreover, the recent enrichment of the therapeutic arsenal effective on Gram-negative bacilli raises the question of their place in the therapeutic management of these infections. Most national and international guidelines recommend limiting their use to microbiologically documented infections. However, many clinical situations and, in particular, the knowledge of digestive or respiratory carriage by MDROs should lead to the discussion of the use of these new molecules, especially the new combinations with beta-lactamase inhibitors in empirical therapy. In this review, we present the current epidemiological data, particularly in terms of MDRO, as well as the clinical and microbiological elements that may be taken into account in the discussion of empirical antibiotic therapy for patients managed for ventilator-associated pneumonia.

Screening for Antimicrobial-Resistant Gram-negative bacteria in hospitalised patients, and risk of progression from colonisation to infection: Systematic review

BACKGROUND

Transmission of antimicrobial-resistant Gram-negative bacteria (AMR-GNB) among hospitalised patients can lead to new cases of carriage, infection and outbreaks, hence the need for early carrier identification. We aim to explore two key elements that may guide control policies for colonisation/infection in hospital settings: screening practices on admission to hospital wards and risk of developing infection from colonisation.

METHODS

We searched on PubMed, Scopus and Cochrane databases for studies published from 2010 up to 2021 reporting on adult patients hospitalised in high-income countries.

RESULTS

The search retrieved 11853 articles. After screening, 100 studies were included. Combining target patient groups and setting type, we identified six screening approaches. The most reported approach was all admitted patients to high-risk (HR) wards (49.4%). The overall prevalence of AMR-GNB was 13.8% (95%CI 9.3-19.0) with significant differences across regions and time. Risk of progression to infection among colonised patients was 11.0% (95%CI 8.0-14.3) and varied according to setting and pathogens' group (p value<0.0001), with higher values reported for Klebsiella species (18.1%; 95%CI 8.9-29.3).

CONCLUSIONS

While providing a comprehensive overview of the screening approaches, our study underlines the considerable burden of AMR-GNB colonisation and risk of progression to infection in hospitals by pathogen, setting and time.

The role of antimicrobial stewardship in preventing KPC-producing Klebsiella pneumoniae

Antimicrobial stewardship programmes are widely considered to be a core component of the response to the antimicrobial resistance threat. However, a positive impact of these interventions in terms of microbiological outcomes remains difficult to demonstrate, especially when focusing on specific resistant phenotypes. The first part of this review aims to explore the complex relationship between antibiotic exposure and resistance development in KPC-producing Klebsiella pneumoniae. In the second part we aim to summarize published examples of antimicrobial stewardship interventions intended to impact on the epidemiology of KPC-producing K. pneumoniae. For this purpose, a literature search was performed and seven studies were included in the review. Both restrictive and non-restrictive interventions were associated with an overall reduction in antibiotic consumption, and a decrease in carbapenem resistance rates was observed in five studies. The overall quality of the evidence was low, mainly due to the poor reporting of microbiological outcomes, lack of a control group and suboptimal study design. Although the link between antibiotic use and resistance development is supported by strong evidence, demonstrating the impact of antimicrobial stewardship interventions on microbiological outcomes remains difficult. Studies with adequate design and appropriate outcome measures are needed to further promote antimicrobial stewardship and elucidate which interventions are more successful for controlling the spread of KPC-producing K. pneumoniae.

The effect of prophylaxis with ertapenem versus cefuroxime/metronidazole on intestinal carriage of carbapenem-resistant or third-generation-cephalosporin-resistant Enterobacterales after colorectal surgery

OBJECTIVES

Compared to cephalosporin-based prophylaxis, ertapenem prophylaxis lowers the risk of surgical site infection among carriers of extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PEs) undergoing colorectal surgery. We aimed to determine whether ertapenem prophylaxis leads to increased postoperative colonization with carbapenem-resistant Enterobacterales (CREs) and third-generation-cephalosporin-resistant Enterobacterales (3GCR-Es).

METHODS

This study was nested within a quality improvement study of prophylaxis for ESBL-PE carriers undergoing colorectal surgery. Patients were screened 4-6 days after surgery for carriage of ESBL-PEs or other 3GCR-Es and CREs. When CREs were detected, pre- and postsurgical clones were compared using Fourier-transform infrared (FT-IR) spectroscopy.

RESULTS

The sample consisted of 56 patients who carried ESBL-PEs before surgery and received cefuroxime/metronidazole prophylaxis (Group 1), 66 who carried ESBL-PEs before surgery and received ertapenem (Group 2), and 103 ESBL-PE non-carriers who received cefuroxime/metronidazole prophylaxis (Group 3). CRE carriage was detected postoperatively in one patient (1.5%) in Group 2 versus eight patients (14.3%) in Group 1 (RD -12.8%; 95%CI -22.4% to -3.1%). For seven out of nine patients, preoperative ESBL-PE and postoperative CRE isolates were compared; in five of them, the pre- and postoperative clones were identical. Postoperative 3GCR-E carriage was detected in 37 patients (56.1%) in Group 2 versus 46 patients in Group 1 (82.1%) (aRD -20.7%, 95%CI -37.3% to -4.1%).

CONCLUSIONS

Among ESBL-PE carriers undergoing colorectal surgery, detection of short-term postsurgical colonization by CREs and 3GCR-Es was significantly lower among patients who received ertapenem prophylaxis than those who received cephalosporin-metronidazole prophylaxis. Resistance development in a colonizing bacterial clone, rather than carbapenemase acquisition, was the major mechanism of carbapenem resistance.

Impact of systematic screening for AmpC-hyperproducing Enterobacterales intestinal carriage in intensive care unit patients

BACKGROUND

Empirical antimicrobial therapy (EAT) is a challenge for community-acquired, hospital-acquired and ventilator-associated pneumonia, particularly in the context of the increasing occurrence of third-generation cephalosporin-resistant Enterobacterales (3GCR-E), including extended-spectrum beta-lactamase Enterobacterales (ESBL-E) and high-level expressed AmpC cephalosporinase-producing Enterobacterales (HLAC-E). To prevent the overuse of broad-spectrum antimicrobial therapies, such as carbapenems, we assessed the performance of screening for intestinal carriage of HLAC-E in addition to ESBL-E to predict 3GCR-E (ESBL-E and/or HLAC-E) presence or absence in respiratory samples in ICU, and to evaluate its potential impact on carbapenem prescription.

MATERIALS AND METHODS

This monocentric retrospective observational study was performed in a surgical ICU during a 4-year period (January 2013-December 2016). Patients were included if they had a positive culture on a respiratory sample and a previous intestinal carriage screening performed by rectal swabbing within 21 days. Sensitivity, specificity, positive (PPV) and negative (NPV) predictive values and likelihood ratios were calculated for the screening for intestinal carriage of ESBL-E, HLAC-E and 3GCR-E (ESBL-E and/or HLAC-E) as predictor of their absence/presence in respiratory samples. Impact of HLAC-E and ESBL-E reporting on EAT was also studied.

RESULTS

765 respiratory samples, retrieved from 468 patients, were analyzed. ESBL-E prevalence was 23.8% in rectal swab and 4.4% in respiratory samples. HLAC-E prevalence was 9.0% in rectal swabs and 3.7% in respiratory samples. Overall, the 3GCR-E prevalence was 31.8% in rectal swabs and 7.7% in respiratory samples. NPVs were 98.8%, 98.0% and 96.6% for ESBL-E, HLAC-E and 3GCR-E, respectively. Over the study period, empirical antimicrobial therapy was initiated for 315 episodes of respiratory infections: 228/315 (72.4%) were associated with negative intestinal carriage screening for both HLAC-E and ESBL-E, of whom 28/228 (12.3%) were treated with carbapenems. Of 23/315 (7.3%) cases with screening for positive intestinal carriage with HLAC-E alone, 10/23 (43.5%) were treated with carbapenems.

CONCLUSION

Systematic screening and reporting of HLAC-E in addition to ESBL-E in intestinal carriage screening could help to predict the absence of 3GCR-E in respiratory samples of severe surgical ICU patients. This could improve the appropriateness of EAT in ICU patients with HAP and may prevent the overuse of carbapenems.

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.

Rationalizing antimicrobial therapy in the ICU: a narrative review

The massive consumption of antibiotics in the ICU is responsible for substantial ecological side effects that promote the dissemination of multidrug-resistant bacteria (MDRB) in this environment. Strikingly, up to half of ICU patients receiving empirical antibiotic therapy have no definitively confirmed infection, while de-escalation and shortened treatment duration are insufficiently considered in those with documented sepsis, highlighting the potential benefit of implementing antibiotic stewardship programs (ASP) and other quality improvement initiatives. The objective of this narrative review is to summarize the available evidence, emerging options, and unsolved controversies for the optimization of antibiotic therapy in the ICU. Published data notably support the need for better identification of patients at risk of MDRB infection, more accurate diagnostic tools enabling a rule-in/rule-out approach for bacterial sepsis, an individualized reasoning for the selection of single-drug or combination empirical regimen, the use of adequate dosing and administration schemes to ensure the attainment of pharmacokinetics/pharmacodynamics targets, concomitant source control when appropriate, and a systematic reappraisal of initial therapy in an attempt to minimize collateral damage on commensal ecosystems through de-escalation and treatment-shortening whenever conceivable. This narrative review also aims at compiling arguments for the elaboration of actionable ASP in the ICU, including improved patient outcomes and a reduction in antibiotic-related selection pressure that may help to control the dissemination of MDRB in this healthcare setting.

Carbapenems and alternative β-lactams for the treatment of infections due to extended-spectrum β-lactamase-producing Enterobacteriaceae: What impact on intestinal colonisation resistance?

The ongoing pandemic of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) is responsible for a global rise in carbapenem consumption that may hasten the dissemination of carbapenemase-producing Enterobacteriaceae (CPE). Hence, carbapenem sparing through the use of alternative β-lactams is increasingly considered as a potential option in patients with ESBL-E infections. However, at the individual level, this strategy implies an in-depth understanding of how carbapenems and their alternatives impair the gut microbiota, especially the anaerobic bacteria and the colonisation resistance (CR) that it confers. In this review, we sought to appraise the impact of carbapenems and their main alternatives for ESBL-E infections (namely β-lactam/β-lactamase inhibitor combinations, cephamycins and temocillin) on the gut ecosystem and the resulting hazard for acquisition of CPE. Although limited, the available evidence challenges our perception of the ecological side effects of these antimicrobials and highlights knowledge gaps regarding antibiotic-induced alterations in intestinal CR. These alterations may depend not only on anti-anaerobic properties but also on a panel of parameters with marked interindividual variability, such as baseline characteristics of the gut microbiota or the degree of biliary excretion for the considered drug. In the current context of ESBL-E dissemination and increasing opportunities for carbapenem-sparing initiatives, large, comparative, high-quality studies based on new-generation sequencing tools are more than ever warranted to better define the positioning of alternative β-lactams in antimicrobial stewardship programmes.

Procalcitonin-guided decision making for duration of antibiotic therapy in neonates with suspected early-onset sepsis: a multicentre, randomised controlled trial (NeoPIns)

BACKGROUND

Up to 7% of term and late-preterm neonates in high-income countries receive antibiotics during the first 3 days of life because of suspected early-onset sepsis. The prevalence of culture-proven early-onset sepsis is 0·1% or less in high-income countries, suggesting substantial overtreatment. We assess whether procalcitonin-guided decision making for suspected early-onset sepsis can safely reduce the duration of antibiotic treatment.

METHODS

We did this randomised controlled intervention trial in Dutch (n=11), Swiss (n=4), Canadian (n=2), and Czech (n=1) hospitals. Neonates of gestational age 34 weeks or older, with suspected early-onset sepsis requiring antibiotic treatment were stratified into four risk categories by their treating physicians and randomly assigned [1:1] using a computer-generated list stratified per centre to procalcitonin-guided decision making or standard care-based antibiotic treatment. Neonates who underwent surgery within the first week of life or had major congenital malformations that would have required hospital admission were excluded. Only principal investigators were masked for group assignment. Co-primary outcomes were non-inferiority for re-infection or death in the first month of life (margin 2·0%) and superiority for duration of antibiotic therapy. Intention-to-treat and per-protocol analyses were done. This trial was registered with ClinicalTrials.gov, number NCT00854932.

FINDINGS

Between May 21, 2009, and Feb 14, 2015, we screened 2440 neonates with suspected early-onset sepsis. 622 infants were excluded due to lack of parental consent, 93 were ineligible for reasons unknown (68), congenital malformation (22), or surgery in the first week of life (3). 14 neonates were excluded as 100% data monitoring or retrieval was not feasible, and one neonate was excluded because their procalcitonin measurements could not be taken. 1710 neonates were enrolled and randomly assigned to either procalcitonin-guided therapy (n=866) or standard therapy (n=844). 1408 neonates underwent per-protocol analysis (745 in the procalcitonin group and 663 standard group). For the procalcitonin group, the duration of antibiotic therapy was reduced (intention to treat: 55·1 vs 65·0 h, p<0·0001; per protocol: 51·8 vs 64·0 h; p<0·0001). No sepsis-related deaths occurred, and 9 (<1%) of 1710 neonates had possible re-infection. The risk difference for non-inferiority was 0·1% (95% CI -4·6 to 4·8) in the intention-to-treat analysis (5 [0·6%] of 866 neonates in the procalcitonin group vs 4 [0·5%] of 844 neonates in the standard group) and 0·1% (-5·2 to 5·3) in the per-protocol analysis (5 [0·7%] of 745 neonates in the procalcitonin group vs 4 [0·6%] of 663 neonates in the standard group).

INTERPRETATION

Procalcitonin-guided decision making was superior to standard care in reducing antibiotic therapy in neonates with suspected early-onset sepsis. Non-inferiority for re-infection or death could not be shown due to the low occurrence of re-infections and absence of study-related death.

FUNDING

The Thrasher Foundation, the NutsOhra Foundation, the Sophia Foundation for Scientific research.