Selective digestive tract decontamination and vancomycin-resistant enterococcus isolation in the surgical intensive care unit

Selective Intestinal Decontamination as a Method for Preventing Infectious Complications (Review)

Infectious complications are the most common cause of death in patients with severe burns. To date, there is no generally accepted method for preventing such complications in burn injury. One of the possible prevention options is selective intestinal decontamination (SID). This method is based on the enteral administration of non-absorbable antimicrobial agents. The preventive effect of SID involves inhibition of intestinal microflora translocation through the mucous membranes, inasmuch as studies demonstrate that endogenous opportunistic microorganisms are a common cause of infectious complications in various critical conditions.

The SID method was originally developed in the Netherlands for patients suffering from mechanical injury. Antimicrobial drugs were selected based on their high activity in relation to the main endogenous opportunistic pathogens and minimal activity against normal intestinal microflora components. The combination of polymyxin (B or E), tobramycin, and amphotericin B with intravenous cefotaxime was chosen as the first SID regimen. Other regimens were proposed afterwards, and the application field of the method was expanded. In particular, it became the method of choice for prevention of infectious complications in patients with severe burn injury.

Clinical studies demonstrate efficacy of some SID regimens for preventing infectious complications in patients with thermal injury. Concomitant administration of SID and systemic preventive antibiotics and addition of oropharyngeal decontamination increases the method efficacy. SID is generally well-tolerated, but some studies show an increased risk of diarrhea with this preventive option. In addition, SID increases the risk of developing antibiotic resistance like any other antibiotic regimens.

Studies of selective digestive decontamination as a natural experiment to evaluate topical antibiotic prophylaxis and cephalosporin use as population-level risk factors for enterococcal bacteraemia among ICU patients

BACKGROUND

Selective digestive decontamination (SDD) and selective oropharyngeal decontamination (SOD) regimens appear protective against ICU-acquired overall bacteraemia. These regimens can be factorized as topical antibiotic prophylaxis (TAP) with (SDD) or without (SOD) protocolized parenteral antibiotic prophylaxis (PPAP) using cephalosporins. Both TAP and cephalosporins are risk factors for enterococcal colonization although their impact on enterococcal bacteraemia within studies of SDD/SOD remains unclear.

OBJECTIVES

To benchmark the enterococcal bacteraemia incidence within component (control and intervention) groups of SDD/SOD studies among ICU patients versus studies without intervention (observational groups).

METHODS

The literature was searched for SDD/SOD studies reporting enterococcal bacteraemia incidence data. In addition, component groups of studies of various non-antibiotic interventions served to provide additional points of reference.

RESULTS

The mean incidence per 100 patients (and 95% CI) for enterococcal bacteraemia among 19 SDD/SOD studies was equally increased among concurrent control (2.1; 1.0%-4.7%) and intervention (2.3; 2.0%-2.7%) groups versus the benchmark incidence (0.8; 0.6%-1.2%) derived from 16 observational study groups and also versus 9 component groups from non-antibiotic studies. These higher incidences remained apparent (P < 0.02) in a meta-regression model adjusting for groupwide factors such as PPAP use, mechanical ventilation proportion, group mean length of stay >7 days and publication year.

CONCLUSIONS

The incidences of enterococcal bacteraemia within both concurrent control and intervention groups of SDD/SOD studies are unusually high compared with the literature-derived benchmark. The impact of parenteral cephalosporin used as PPAP additional to TAP on enterococcal bacteraemia incidence was indeterminate in this analysis.

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

BACKGROUND

Many meta-analyses have shown reductions in infection rates and mortality associated with the use of selective digestive decontamination (SDD) or selective oropharyngeal decontamination (SOD) in intensive care units (ICUs). These interventions have not been widely implemented because of concerns that their use could lead to the development of antimicrobial resistance in pathogens. We aimed to assess the effect of SDD and SOD on antimicrobial resistance rates in patients in ICUs.

METHODS

We did a systematic review of the effect of SDD and SOD on the rates of colonisation or infection with antimicrobial-resistant pathogens in patients who were critically ill. We searched for studies using Medline, Embase, and Cochrane databases, with no limits by language, date of publication, study design, or study quality. We included all studies of selective decontamination that involved prophylactic application of topical non-absorbable antimicrobials to the stomach or oropharynx of patients in ICUs, with or without additional systemic antimicrobials. We excluded studies of interventions that used only antiseptic or biocide agents such as chlorhexidine, unless antimicrobials were also included in the regimen. We used the Mantel-Haenszel model with random effects to calculate pooled odds ratios.

FINDINGS

We analysed 64 unique studies of SDD and SOD in ICUs, of which 47 were randomised controlled trials and 35 included data for the detection of antimicrobial resistance. When comparing data for patients in intervention groups (those who received SDD or SOD) versus data for those in control groups (who received no intervention), we identified no difference in the prevalence of colonisation or infection with Gram-positive antimicrobial-resistant pathogens of interest, including meticillin-resistant Staphylococcus aureus (odds ratio 1·46, 95% CI 0·90-2·37) and vancomycin-resistant enterococci (0·63, 0·39-1·02). Among Gram-negative bacilli, we detected no difference in aminoglycoside-resistance (0·73, 0·51-1·05) or fluoroquinolone-resistance (0·52, 0·16-1·68), but we did detect a reduction in polymyxin-resistant Gram-negative bacilli (0·58, 0·46-0·72) and third-generation cephalosporin-resistant Gram-negative bacilli (0·33, 0·20-0·52) in recipients of selective decontamination compared with those who received no intervention.

INTERPRETATION

We detected no relation between the use of SDD or SOD and the development of antimicrobial-resistance in pathogens in patients in the ICU, suggesting that the perceived risk of long-term harm related to selective decontamination cannot be justified by available data. However, our study indicates that the effect of decontamination on ICU-level antimicrobial resistance rates is understudied. We recommend that future research includes a non-crossover, cluster randomised controlled trial to assess long-term ICU-level changes in resistance rates.

FUNDING

None.

[Decontamination. A treatment without indications]

The prevention of ventilator-associated pneumonia (VAP) is a priority in the Intensive Care Unit (ICU). To achieve this goal, clinical practice guidelines recommend the simultaneous application of a heterogeneous group of preventive measures of proven effectiveness. That is why we are presently seeing a reduction in VAP incidence to values previously considered unreachable. Better compliance with clinical practice guidelines has resulted in VAP rates approaching zero in multiple studies. Faced with the measures recommended in these guidelines, selective digestive decontamination (SDD), used together with other infection control practices, has shown efficacy in hospitals with high baseline incidence of pneumonia. However, its effectiveness in hospitals with good compliance of clinical practice guidelines and lower rates of VAP is highly unlikely. A serious drawback of DDS is the risk of favoring the selection of resistant microorganisms that can spread easily through the ICU and the hospital. With current standards of infection prevention, DDS is an unnecessary and risky measure, which should not be used on a widespread basis. Those situations in which the DDS may increase the effectiveness of properly implemented standard measures are still unknown.

Selective Digestive Tract Decontamination—Will It Prevent Infection with Multidrug-Resistant Gram-Negative Pathogens but Still Be Applicable in Institutions where Methicillin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococci Are Endemic?

The purposes of selective decontamination of the digestive tract are to treat infections that may be incubating at the time a patient is admitted to an intensive care unit (ICU), by intravenous administration of antibiotics during the first days of a stay in the ICU, and to prevent ICU-acquired infections, by topical application of antibiotics in the oropharynx and the gastrointestinal tract. Despite multiple trials in which a considerable reduction in the incidence of ventilator-associated pneumonia was demonstrated, major objections against the routine use of selective decontamination of the digestive tract have included a lack of demonstrated reductions in mortality rates and in length of stay (in individual trials), a lack of cost-efficacy data, and the threat of selection of multidrug-resistant bacteria. Recently, 2 controlled, randomized studies reported significant reductions in mortality rates among patients in ICUs who underwent selective decontamination of the digestive tract in combination with reduced selection of antibiotic-resistant pathogens. However, those studies were performed in settings where levels of antibiotic resistance are low, and some methodological issues remain unresolved. If these beneficial results are confirmed, the question of how to balance these benefits against the expected enhanced selection of methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and, possibly, multidrug-resistant gram-negative bacteria will emerge.

Selective decontamination of the digestive tract: impact on cytokine release and mucosal damage after hemorrhagic shock

OBJECTIVE

To determine if selective decontamination of the digestive tract (SDD) influences the proinflammatory immune response of the gut after hemorrhage.

DESIGN

Random assignment to either unmanipulated control after 7 days of SDD or conventional rat chow, or hemorrhagic shock group after the same time of conventional rat chow or SDD.

SETTING

University animal laboratory.

SUBJECTS

Male Wistar rats, weighing between 300 and 350 g.

INTERVENTION

Animals of the control group were not manipulated until organ harvesting, whereas animals of the hemorrhagic shock group were bled to 30 +/- 5 mm Hg for 90 mins by withdrawal/reinfusion of shed blood and were resuscitated by Ringer's lactate equivalent to the shed blood volume.

MEASUREMENTS AND MAIN RESULTS

Rats were killed after resuscitation (hemorrhagic shock group) or completed feeding (control group). Whole portal and caval blood was obtained, and splenic macrophages and gut mononuclear cells were harvested to measure supernatant tumor necrosis factor-alpha and IL-6 by bioassay. Mesenteric lymph nodes were obtained to determine bacterial translocation, and a histologic specimen was taken from the distal ileum. Feces were harvested to examine the effect of SDD. SDD eliminated Gram-negative enteric bacteria and had no influence on mucosal damage or on bacterial translocation in control animals and animals after hemorrhage. In animals receiving conventional rat chow, hemorrhagic shock led to significantly (p <.05) elevated lipopolysaccharide-stimulated proinflammatory cytokine (tumor necrosis factor-alpha and interleukin-6) release in whole portal blood, splenic macrophages, and gut mononuclear cells compared with the control group without shock. In contrast, hemorrhagic shock after SDD led to suppressed or unchanged cytokine release compared with unmanipulated animals receiving SDD. However, SDD itself induced significant (p <.05) cytokine release in these organs. Furthermore, plasma concentrations of tumor necrosis factor-alpha and interleukin-6 were significantly (p <.05) elevated in animals after hemorrhage and SDD compared with animals after hemorrhage alone.

CONCLUSIONS

Hemorrhagic shock led to significant cytokine release. In contrast, cytokine release after hemorrhage and SDD was unchanged or suppressed. Furthermore, in control animals without hemorrhagic shock, SDD induced significant cytokine release. Therefore, selective decontamination of the gut, as practiced in some patients, may induce additional proinflammatory cytokine release, which can add to the proinflammatory burst in case of a complication such as hemorrhagic shock.

Selective decontamination of the digestive tract

Ventilator-associated pneumonia usually originates from the patient's oropharyngeal microflora. In selective digestive decontamination, topical antibiotics are applied to the oropharynx and stomach for prevention of pneumonia and other infections, possibly reducing infection-related mortality. Selective digestive decontamination is also used for the prevention of gut-derived infections in acute necrotizing pancreatitis and liver transplantation. Despite numerous clinical trials, selective digestive decontamination remains controversial. Reduction of the incidence of pneumonia is accepted, but the extent of reduction is debated. Mortality was not reduced in most individual trials, but this finding was calculated in meta-analyses, especially for combined use of topical and systemic antibiotics in surgical ICU patients. Some investigators reported increased resistance and a shift to Gram-positive pathogens. Today, it appears that selective means not only selective suppression of pathogenic bacteria but also selection of appropriate groups of patients for underlying diseases and severity of illness, and selection of ICUs, where the endemic resistance patterns might allow the use of selective digestive decontamination at a relatively low risk for increased selection pressure.