Effect of selective decontamination on antimicrobial resistance in intensive care units: a systematic review and meta-analysis

Antibiotic stewardship programmes in intensive care units: Why, how, and where are they leading us

Antibiotic usage and increasing antimicrobial resistance (AMR) mount significant challenges to patient safety and management of the critically ill on intensive care units (ICU). Antibiotic stewardship programmes (ASPs) aim to optimise appropriate antibiotic treatment whilst minimising antibiotic resistance. Different models of ASP in intensive care setting, include “standard” control of antibiotic prescribing such as “de-escalation strategies”through to interventional approaches utilising biomarker-guided antibiotic prescribing. A systematic review of outcomes related studies for ASPs in an ICU setting was conducted. Forty three studies were identified from MEDLINE between 1996 and 2014. Of 34 non-protocolised studies, [1 randomised control trial (RCT), 22 observational and 11 case series], 29 (85%) were positive with respect to one or more outcome: These were the key outcome of reduced antibiotic use, or ICU length of stay, antibiotic resistance, or prescribing cost burden. Limitations of non-standard antibiotic initiation triggers, patient and antibiotic selection bias or baseline demographic variance were identified. All 9 protocolised studies were RCTs, of which 8 were procalcitonin (PCT) guided antibiotic stop/start interventions. Five studies addressed antibiotic escalation, 3 de-escalation and 1 addressed both. Six studies reported positive outcomes for reduced antibiotic use, ICU length of stay or antibiotic resistance. PCT based ASPs are effective as antibiotic-stop (de-escalation) triggers, but not as an escalation trigger alone. PCT has also been effective in reducing antibiotic usage without worsening morbidity or mortality in ventilator associated pulmonary infection. No study has demonstrated survival benefit of ASP. Ongoing challenges to infectious disease management, reported by the World Health Organisation global report 2014, are high AMR to newer antibiotics, and regional knowledge gaps in AMR surveillance. Improved AMR surveillance data, identifying core aspects of successful ASPs that are transferable, and further well-conducted trials will be necessary if ASPs are to be an effective platform for delivering desired patient outcomes and safety through best antibiotic policy.

Public health evolutionary biology of antimicrobial resistance: priorities for intervention

The three main processes shaping the evolutionary ecology of antibiotic resistance (AbR) involve the emergence, invasion and occupation by antibiotic-resistant genes of significant environments for human health. The process of emergence in complex bacterial populations is a high-frequency, continuous swarming of ephemeral combinatory genetic and epigenetic explorations inside cells and among cells, populations and communities, expanding in different environments (migration), creating the stochastic variation required for evolutionary progress. Invasion refers to the process by which AbR significantly increases in frequency in a given (invaded) environment, led by external invaders local multiplication and spread, or by endogenous conversion. Conversion occurs because of the spread of AbR genes from an exogenous resistant clone into an established (endogenous) bacterial clone(s) colonizing the environment; and/or because of dissemination of particular resistant genetic variants that emerged within an endogenous clonal population. Occupation of a given environment by a resistant variant means a permanent establishment of this organism in this environment, even in the absence of antibiotic selection. Specific interventions on emergence influence invasion, those acting on invasion also influence occupation and interventions on occupation determine emergence. Such interventions should be simultaneously applied, as they are not simple solutions to the complex problem of AbR.

Ventilator-associated pneumonia prevention methods using topical antibiotics: herd protection or herd peril?

Ventilator-associated pneumonia (VAP) develops in approximately 20% of patients in the ICU receiving prolonged mechanical ventilation (MV). Among the range of methods for preventing VAP, the evidence base for topical antibiotics (TAs), including selective digestive decontamination, appears to be the most compelling. However, several observations are puzzling, and the contextual influence resulting from concurrent use of both topical placebo and TA within an ICU remains untested. As with herd protection conferred by vaccination, contextual influences resulting from a population-based intervention cannot be estimated at the level of a single trial. Estimating contextual effects requires multilevel random-effects methods. In this way the dispersion in VAP incidence across groups from 206 studies, as cited in various-source systematic reviews, was calibrated. The benchmark mean VAP incidence derived from 49 observational groups of patients receiving MV is 23.7% (95% CI, 20.6%-27.2%). In contrast, for 20 and 15 concurrent control groups from the TA evidence base that did vs did not receive topical placebo, respectively, this incidence is 38% (95% CI, 29%-48%) and 33% (95% CI, 20%-50%). This contextual influence remains significant in a meta-regression model adjusted for group-level variables, such as within a trauma ICU context. The mean VAP incidence for five other categories of control groups from the broader evidence base is within four percentage points of the benchmark. The contextual effect of TA is paradoxic, peculiar, potent, perfidious, and potentially perilous. The TA evidence base requires reappraisal to consider this herd peril.

Homogeneity of antimicrobial policy, yet heterogeneity of antimicrobial resistance: antimicrobial non-susceptibility among 108,717 clinical isolates from primary, secondary and tertiary care patients in London

OBJECTIVES

We examined the 4 year trend in antimicrobial susceptibilities and prescribing across levels of care at two London teaching hospitals and their multisite renal unit, and for the surrounding community.

METHODS

Laboratory and pharmacy information management systems were interrogated, with antimicrobial use and susceptibilities analysed between hospitals, within hospitals and over time.

RESULTS

A total of 108,717 isolates from 71,687 patients were identified, with significant differences (at P < 0.05) in antimicrobial susceptibility between and within hospitals. Across the 4 years, rates of ESBL-/AmpC-producing Enterobacteriaceae ranged from 6.4% to 10.7% among community isolates, 17.8% to 26.9% at ward level and 25.2% to 52.5% in critical care. Significant variations were also demonstrated in glycopeptide-resistant enterococci (ward level 6.2%-17.4%; critical care 21.9%-56.3%), MRSA (ward level 18.5%-38.2%; critical care 12.5%-47.9%) and carbapenem-resistant Pseudomonas spp. (ward level 8.3%-16.9%; critical care 19.9%-53.7%). Few instances of persistently higher resistance were seen between the hospitals in equivalent cohorts, despite persistently higher antimicrobial use in Hospital 1 than Hospital 2. We found significant fluctuations in non-susceptibility year on year across the cohorts, but with few persistent trends.

CONCLUSIONS

The marked heterogeneity of antimicrobial susceptibilities between hospitals, within hospitals and over time demands detailed, standardized surveillance and appropriate benchmarking to identify possible drivers and effective interventions. Homogeneous antimicrobial policies are unlikely to continue to be suitable as individual hospitals join hospital networks, and policies should be tailored to local resistance rates, at least at the hospital level, and possibly with finer resolution, particularly for critical care.

Trends in ventilator-associated pneumonia: impact of a ventilator care bundle in an Italian tertiary care hospital intensive care unit

BACKGROUND

The impact on ventilator-associated pneumonia (VAP) occurrence of a multifaceted program, including progressive strategies for VAP prevention, implemented in an Italian intensive care unit (ICU) is reported.

METHODS

All adults admitted to the ICU in 2004-2010 with a length of stay ≥72 hours and mechanical ventilation time ≥48 hours were included in the study. Demographics, clinical information, and data on VAP were extracted from the ICU-acquired infection surveillance dataset. A standardized bundle for VAP prevention was implemented in 2004. In 2008, selective digestive tract decontamination (SDD) was added to the protocol. Changes in VAP incidence were evaluated.

RESULTS

There were 1,372 subjects included in the study. Overall, 156 (11.4%) developed VAP. In the second part of the study VAP incidence decreased from 15.9% to 6.7% (P < .001). Reductions both in early-onset VAP (6.6% to 1.9%; P < .001) and late-onset VAP (9.3% to 4.7%; P = .001) incidence were observed. Multivariate analysis showed a significant reduction in the risk of developing VAP from multidrug-resistant pathogens in the bundle plus SDD period as well (odds ratio, .54; 95% confidence interval, .31-.91).

CONCLUSION

The implementation of a standardized approach to patient care, including a number of key reduction interventions, was associated with a significant reduction in the risk of developing VAP.

Antibiotic use and emerging resistance: how can resource-limited countries turn the tide?

Antibiotic resistance is a global crisis driven by appropriate and inappropriate antibiotic use to treat human illness and promote animal growth. The antimicrobial resistance epidemic continues to spread due to the triple threat of unfettered access, minimal product regulation and oversight of antibiotic prescription, and lack of clinical diagnostic tools to support antibiotic de-escalation in low-resource settings. In high-resource settings, evidence-based strategies have improved the appropriateness of antibiotic use, limiting the spread of drug-resistant organisms and reducing hospital-associated infections, strategies which may also be effective to stop the spread of resistance in resource-poor countries. Current research and surveillance efforts on antimicrobial resistance and hospital-associated infections in low-resource settings are extremely limited and largely focused on intensive care units. Many challenges exist to improving antibiotic use and infection control in resource-limited settings, and turning the tide requires intensifying research and surveillance, antimicrobial stewardship, and developing new bedside diagnostic tools for bacterial infections and antimicrobial susceptibility.

Effects of selective digestive decontamination (SDD) on the gut resistome

OBJECTIVES

Selective digestive decontamination (SDD) is an infection prevention measure for critically ill patients in intensive care units (ICUs) that aims to eradicate opportunistic pathogens from the oropharynx and intestines, while sparing the anaerobic flora, by the application of non-absorbable antibiotics. Selection for antibiotic-resistant bacteria is still a major concern for SDD. We therefore studied the impact of SDD on the reservoir of antibiotic resistance genes (i.e. the resistome) by culture-independent approaches.

METHODS

We evaluated the impact of SDD on the gut microbiota and resistome in a single ICU patient during and after an ICU stay by several metagenomic approaches. We also determined by quantitative PCR the relative abundance of two common aminoglycoside resistance genes in longitudinally collected samples from 12 additional ICU patients who received SDD.

RESULTS

The patient microbiota was highly dynamic during the hospital stay. The abundance of antibiotic resistance genes more than doubled during SDD use, mainly due to a 6.7-fold increase in aminoglycoside resistance genes, in particular aph(2″)-Ib and an aadE-like gene. We show that aph(2″)-Ib is harboured by anaerobic gut commensals and is associated with mobile genetic elements. In longitudinal samples of 12 ICU patients, the dynamics of these two genes ranged from a ∼10(4) fold increase to a ∼10(-10) fold decrease in relative abundance during SDD.

CONCLUSIONS

ICU hospitalization and the simultaneous application of SDD has large, but highly individualized, effects on the gut resistome of ICU patients. Selection for transferable antibiotic resistance genes in anaerobic commensal bacteria could impact the risk of transfer of antibiotic resistance genes to opportunistic pathogens.

Trends in human fecal carriage of extended-spectrum β-lactamases in the community: toward the globalization of CTX-M

In the last 10 years, extended-spectrum β-lactamase-producing enterobacteria (ESBL-E) have become one of the main challenges for antibiotic treatment of enterobacterial infections, largely because of the current CTX-M enzyme pandemic. However, most studies have focused on hospitalized patients, though today it appears that the community is strongly affected as well. We therefore decided to devote our investigation to trends in ESBL-E fecal carriage rates and comprehensively reviewed data from studies conducted on healthy populations in various parts of the world. We show that (i) community ESBL-E fecal carriage, which was unknown before the turn of the millennium, has since increased significantly everywhere, with developing countries being the most affected; (ii) intercontinental travel may have emphasized and globalized the issue; and (iii) CTX-M enzymes, especially CTX-M-15, are the dominant type of ESBL. Altogether, these results suggest that CTX-M carriage is evolving toward a global pandemic but is still insufficiently described. Only a better knowledge of its dynamics and biology will lead to further development of appropriate control measures.

The views of health care professionals about selective decontamination of the digestive tract: an international, theoretically informed interview study

PURPOSE

Selective decontamination of the digestive tract (SDD) as a prophylactic intervention improves hospital-acquired infection and survival rates. Uptake of SDD is low and remains controversial. This study applied the theoretical domains framework to assess intensive care unit clinicians' views about SDD in regions with limited or no adoption of SDD.

MATERIALS AND METHODS

Participants were health professionals with "decisional authority" for the adoption of SDD. Semistructured interviews were conducted as the first round of a Delphi study. Views about SDD adoption, delivery, and further SDD research were explored. Directed content analysis of interview data identified subthemes, which informed item development for subsequent Delphi rounds. Linguistic features of interview data were also explored.

RESULTS

One hundred forty-one participants provided interview data. Fifty-six subthemes were identified; 46 were common across regions. Beliefs about consequences were the most widely elaborated theme. Linguistic features of how participants discussed SDD included caution expressed when discussing the risks and benefits and words such as "worry," "anxiety," and "fear" when discussing potential antibiotic resistance associated with SDD.

CONCLUSIONS

We identified salient beliefs, barriers, and facilitators to SDD adoption and delivery. What participants said about SDD and the way in which they said it demonstrated the degree of clinical caution, uncertainty, and concern that SDD evokes.

Systematic review of perioperative selective decontamination of the digestive tract in elective gastrointestinal surgery

BACKGROUND

Studies on selective decontamination of the digestive tract (SDD) in elective gastrointestinal surgery have shown decreased rates of postoperative infection and anastomotic leakage. However, the prophylactic use of perioperative SDD in elective gastrointestinal surgery is not generally accepted.

METHODS

A systematic review of randomized clinical trials (RCTs) was conducted to compare the effect of perioperative SDD with systemic antibiotics (SDD group) with systemic antibiotic prophylaxis alone (control group), using MEDLINE, Embase and the Cochrane Central Register of Controlled Trials. Endpoints included postoperative infection, anastomotic leakage, and in-hospital or 30-day mortality.

RESULTS

Eight RCTs published between 1988 and 2011, with a total of 1668 patients (828 in the SDD group and 840 in the control group), were included in the meta-analysis. The total number of patients with infection (reported in 5 trials) was 77 (19.2 per cent) of 401 in the SDD group, compared with 118 (28.2 per cent) of 418 in the control group (odds ratio 0.58, 95 per cent confidence interval 0.42 to 0.82; P = 0.002). The incidence of anastomotic leakage was significantly lower in the SDD group: 19 (3.3 per cent) of 582 patients versus 44 (7.4 per cent) of 595 patients in the control group (odds ratio 0.42, 0.24 to 0.73; P = 0.002).

CONCLUSION

This systematic review and meta-analysis suggests that a combination of perioperative SDD and perioperative intravenous antibiotics in elective gastrointestinal surgery reduces the rate of postoperative infection including anastomotic leakage compared with use of intravenous antibiotics alone.

Gut instinct

Barriers to the use of selective digestive decontamination include concerns about emergence of resistant organisms, over-estimation of current performance in preventing ventilator-associated pneumonia (VAP), alternative methods of preventing VAP, and misunderstanding of mechanisms of action. A definitive cluster-randomised trial should be undertaken that incorporates practitioner concerns and effect-size preferences.

Clinical stakeholders' opinions on the use of selective decontamination of the digestive tract in critically ill patients in intensive care units: an international Delphi study

Introduction

Selective decontamination of the digestive tract (SDD) is a prophylactic antibiotic regimen that is not widely used in practice. We aimed to describe the opinions of key ‘stakeholders’ about the validity of the existing evidence base, likely consequences of implementation, relative importance of their opinions in influencing overall practice, likely barriers to implementation and perceptions of the requirement for further research to inform the decision about whether to embark on a further large randomised controlled trial.

Methods

This was a Delphi study informed by comprehensive framework of possible determinants of health professionals’ behaviour to study Critical Care practice in four countries. There were four key stakeholder participant groups including ICU physicians, pharmacists, clinical leads, and clinical microbiologists/ infectious disease physicians. Round one comprised participant interviews and Rounds two and three were online questionnaires using Delphi method.

Results

In this study, 141 participants were recruited of whom 82% were retained. Participants rated themselves as knowledgeable about SDD. Antibiotic resistance was identified as the most important issue. SDD was seen as a low clinical priority but few participants reported strong opposition. There was moderate agreement that research to date has not adequately addressed concerns about antibiotic resistance and lacks generalizability. Participants indicated equipoise with regard to benefits and harms of SDD, and indicated strong support for a further randomised trial.

Conclusions

Clinicians have clinical equipoise about the effectiveness of SDD. Future research requires longer follow up to assess antibiotic resistance as well as greater validity/generalizability to provide definitive answers on the effectiveness of decontamination and effects on antibiotic resistance. SDD was regarded as not being a high clinical priority, which may limit future trial participation. These results have identified that further large randomised controlled trial of SDD in critical care is both warranted and appropriate.

Early management of acute pancreatitis

Acute pancreatitis is the most common gastro-intestinal indication for acute hospitalization and its incidence continues to rise. In severe pancreatitis, morbidity and mortality remains high and is mainly driven by organ failure and infectious complications. Early management strategies should aim to prevent or treat organ failure and to reduce infectious complications. This review addresses the management of acute pancreatitis in the first hours to days after onset of symptoms, including fluid therapy, nutrition and endoscopic retrograde cholangiography. This review also discusses the recently revised Atlanta classification which provides new uniform terminology, thereby facilitating communication regarding severity and complications of pancreatitis.

Rapid emergence of secondary resistance to gentamicin and colistin following selective digestive decontamination in patients with KPC-2-producing Klebsiella pneumoniae: a single-centre experience

After a single patient was transferred to Leipzig University Hospital from a hospital in Rhodes, Greece, the hospital experienced the largest outbreak due to a KPC-2-producing Klebsiella pneumoniae (KPC-2-KP) strain thus far observed in Germany. Ninety patients hospitalised between July 2010 and October 2012 were affected. In an attempt to eliminate KPC-2-KP from their digestive tracts, 14 consecutive patients (16%) were treated with a short course (7 days) of selective digestive decontamination (SDD), employing colistin (1 million units q.i.d.) and gentamicin (80 mg q.i.d.) as oral solutions, and applying colistin/gentamicin gel (0.5 g) to the oral cavity. In a retrospective analysis, these 14 SDD patients were compared with the remaining 76 patients harbouring KPC-2-KP. KPC-2-KP carrier status was followed in all 14 SDD patients by submitting stool samples to KPC-specific PCR. The mean follow-up period was 48 days (range 12-103 days). Successful elimination of KPC-2-KP was defined as a minimum of three consecutive negative PCR test results separated by ≥48 h each. Decolonisation of KPC-2-KP was achieved in 6/14 patients (43%) after a mean of 21 days (range 12-40 days), but was also observed in 23/76 (30%) of the non-SDD controls (P = 0.102). SDD treatment resulted in the development of secondary resistance to colistin (19% increase in resistance rate) and gentamicin (45% increase) in post-treatment isolates. In the control group, no secondary resistance occurred. We conclude that the SDD protocol applied in this study was not sufficiently effective for decolonisation and was associated with resistance development.