Cycling empirical antimicrobial agents to prevent emergence of antimicrobial-resistant Gram-negative bacteria among intensive care unit patients

Antimicrobial stewardship

In response to the global antibiotic resistance crisis, antimicrobial stewardship programs have emerged throughout the United States. Effective programs integrate several strategic methods, including evaluation and feedback regarding the necessity and appropriateness of antimicrobial therapy, staff education, and formulary restrictions. Multidisciplinary teams as well as institutional support are needed to form effective subcommittees to monitor national and local surveillance reports and resistance patterns, and to update antibiograms. Computerized decision support programs have been effective and successful methods of antimicrobial stewardship and can be a powerful tool in stewardship programs. Successful programs have reduced not only institutional resistance rates, but also morbidity, mortality, and cost.

Implementation of antibiotic rotation protocol improves antibiotic susceptibility profile in a surgical intensive care unit

BACKGROUND

Antibiotic rotation has been proposed as a way to potentially reduce the development of antimicrobial resistant bacteria in intensive care units. We assessed the effect of an antibiotic rotation protocol on the antibiotic susceptibility profiles of three clinically relevant gram-negative microorganisms within our surgical intensive care unit (SICU).

METHODS

Our SICU implemented an antibiotic rotation protocol in 2003. Four antibiotics (piperacillin/tazobactam, imipenem/cilastin, ceftazidime, and ciprofloxacin) were rotated as the primary antibiotic used to treat suspected gram-negative infections every month, with the four-drug cycle being repeated every 4 months. Antibiotic susceptibility data for three microorganisms (Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae) were collected for the year before (2002) and the year after (2004) the implementation of the rotation protocol. Changes in antimicrobial susceptibility rates were analyzed for the three microorganisms. As a comparison, a similar analysis was conducted for microorganisms isolated from our medical intensive care unit, where no antibiotic rotation protocol was implemented.

RESULTS

Implementation of an antibiotic rotation protocol in our SICU resulted in a significant increase in the percentage of P. aeruginosa isolates sensitive to ceftazidime (67% in 2002 vs. 92% in 2004, p = 0.002) and piperacillin/tazobactam (78% in 2002 vs. 92% in 2004, p = 0.043). Isolates from the medical intensive care unit did not demonstrate an increase in antimicrobial susceptibility. In fact, the susceptibility of E. coli to piperacillin/tazobactam decreased during this time period (p = 0.047).

CONCLUSIONS

Implementation of an antibiotic rotation protocol in our SICU resulted in overall improvement in the antibiotic susceptibility profile of gram-negative microorganisms relative to our medical intensive care unit, where such a protocol was not used.

Antibiotic cycling to decrease bacterial antibiotic resistance: a 5-year experience on a bone marrow transplant unit

Multidrug-resistant pathogens have important effects on clinical outcomes. Antibiotic cycling is one approach to control anti-microbial resistance, but few studies have examined cycling in hematology-oncology units. Antibiotic cycling was implemented in January 1999 at our hematology-oncology unit, alternating piperacillin-tazobactam (pip-tazo) and cefepime in 3 months periods, until June 2004. Clinical isolates were compared in post- and pre-intervention periods and with the susceptibility among the solid organ transplant intensive care unit (TICU) isolates. The rate of Gram-negative isolates remained stable. Among Gram-negatives, susceptibility to cefepime and pip-tazo remained stable. There was an increase in Enterococcus spp. (P=0.007), and susceptibility to ampicillin and vancomycin decreased (odds ratio (OR): 0.04, 95% confidence interval (CI): 0.17-0.89 and OR: 0.23, 95% CI: 0.09-0.58). Compared with the TICU, there was increased susceptibility to pip-tazo and cefepime among enterics (OR: 7.32, 95% CI: 4.44-12.07 and OR: 8.82, 95% CI: 2.1-37.13) and Pseudomonas aeruginosa (OR: 4.27, 95% CI: 1.47-12.4 and OR: 4.61, 95% CI: 1.75-12.1) and decreased susceptibility to ampicillin and vancomycin among enterococci (OR: 0.44, 95% CI: 0.30-0.63 and OR: 0.38, 95% CI: 0.26-0.56). Cycling was associated with preserved antibiotic susceptibility among Gram-negatives, but with an increase in Enterococcus spp. and vancomycin and ampicillin resistance among enterococci.

Cost of Gram-negative resistance*

OBJECTIVE

It is unclear that infections with Gram-negative rods resistant to at least one major class of antibiotics (rGNR) have a greater effect on patient morbidity than infections caused by sensitive strains (sGNR). We wished to test the hypothesis that rGNR infections are associated with higher resource utilization.

DESIGN

Retrospective observational cohort study of prospectively collected data.

SETTING

University hospital surgical intensive care unit and ward.

PATIENTS

Surgical patients with at least one GNR infection.

MEASUREMENTS

We compared admissions treated for rGNR infection with those with sGNR infections. Primary outcomes were total hospital costs and hospital length of stay. Other outcomes included antibiotic treatment cost, in-hospital death, and intensive care unit length of stay. After univariate analysis comparing outcomes after rGNR infection with those after sGNR infection, multivariate linear regression models for hospital cost and length of stay were created to account for potential confounders.

MAIN RESULTS

Cost data were available for 604 surgical admissions treated for at least one GNR infection (Centers for Disease Control and Prevention criteria), 137 (23%) of which were rGNR infections. Admissions with rGNR infections were associated with a higher severity of illness at the time of infection (Acute Physiology and Chronic Health Evaluation II score, 17.6 +/- 0.6 vs. 13.9 +/- 0.3), had higher median hospital costs ($80,500 vs. $29,604, p < .0001) and median antibiotic costs ($2,607 vs. $758, p < .0001), and had longer median hospital length of stay (29 vs. 13 days, p < .0001) and median intensive care unit length of stay (13 days vs. 1 day, p < .0001). Infection with rGNR within the first 7 days of admission was independently predictive of increased hospital cost (incremental increase in median hospital cost estimated at $11,075; 95% confidence interval, $3,282-$20,099).

CONCLUSIONS

Early infection with rGNR is associated with a high economic burden, which is in part related to increased antibiotic utilization compared with infection with sensitive organisms. Efforts to control overuse of antibiotics should be pursued.

The Impact of an Antibiotic Cycling Program on Empirical Therapy for Gram-Negative Infections

BACKGROUND

Antimicrobial-resistant organisms are an emerging problem in the ICU. Therapy cycling empiric antibiotics between various classes may influence bacterial resistance patterns. Understanding the impact of cycling on the appropriate treatment of suspected Gram-negative infections is important.

METHODS

Data were prospectively collected on patients who were admitted to a 19-bed medical ICU (MICU). A total of 1,172 patients were admitted to the MICU for > 48 h and were evaluated during a 28.5-month period. After 4.5 months of baseline data collection, an antibiotic-cycling protocol was implemented, using four different antibiotic classes with Gram-negative activity that were cycled every 3 to 4 months. Therapy was considered to be inappropriate if the subsequent bacterial isolate was resistant to the empiric drug used.

RESULTS

There were 59 bloodstream infections (BSIs), 17 ventilator-associated pneumonias (VAPs), and 101 urinary tract infections (UTIs) involving Gram-negative bacteria among 139 patients. Fifty-five infections (31%) were due to Gram-negative bacteria resistant to one or more antibiotic agents (BSIs, 18 [30%]; VAPs, 4 [23%]; and UTIs, 33 [33%]). Fifteen patients received inappropriate empiral therapy for 18 resistant Gram-negative infections (BSIs, 7 [39%]; VAPs, 3 [75%]; UTIs, 8 [24%]). Patients receiving inappropriate therapy were more likely to die (10 patients [67%] vs 40 patients [32%], respectively; p < 0.01). There was no difference in the receipt of appropriate empirical antibiotic therapy during the baseline compared to cycling (infectious episodes, 15% vs 10%, respectively; p = 0.4).

CONCLUSIONS

Antimicrobial resistance occurred in almost 30% of ICU infections involving Gram-negative bacteria. Antibiotic cycling was not associated with significant changes in the receipt of appropriate empirical antimicrobial therapy for the treatment of ICU infections.

Is Antibiotic Cycling the Answer to Preventing the Emergence of Bacterial Resistance in the Intensive Care Unit?

Antibiotic resistance has emerged as an important determinant of mortality for patients in the intensive care unit (ICU) setting. This is largely due to the increasing presence of pathogenic microorganisms with resistance to existing antibiotic agents, resulting in the administration of inappropriate treatment. Escalating antibiotic resistance has also been associated with greater overall health care costs, as a result of prolonged hospitalizations and convalescence associated with failure of antibiotic treatment, the need to develop new antibiotic agents, and the implementation of broader infection control and public health interventions aimed at curbing the spread of antibiotic-resistant pathogens. Antibiotic cycling has been advocated as a tool to reduce the occurrence of antibiotic resistance, especially in the ICU setting. Unfortunately, the cumulative evidence to date suggests that antibiotic cycling has limited efficacy for preventing antibiotic resistance. Nevertheless, a strategy whereby multiple or all classes of antibiotics are available for use (i.e., antibiotic heterogeneity) can be part of a broader effort aimed at curtailing antibiotic resistance within ICUs. Such efforts should be routine, given the limited availability of new antibiotic drug classes for the foreseeable future.

Healthcare Epidemiology: Potential Confounding in Evaluating Infection‐Control Interventions in Hospital Settings: Changing Antibiotic Prescription

The colonization dynamics of antibiotic-resistant pathogens in hospital settings are complex, with multiple and continuously interacting variables (e.g., introduction of resistance, infection-control practices, antibiotic use). Quantification of these variables is indispensable in the evaluation of intervention studies, because these variables represent potential confounders. In this article, the complexity of colonization dynamics is described. Through a systematic review, we identified studies that evaluated the modification of antibiotic prescription to reduce antibiotic resistance in intensive care units (n=19), and the extent of confounding-control was determined. Most studies evaluated antimicrobial restriction/substitution (n=12) or antibiotic rotation (n=4). Sixteen studies had a prospective cohort design (before-after), of which 12 were without a control group. Introduction of antibiotic resistance was determined in 10 studies. The relative importance of colonization routes and adherence to infection-control measures were not determined in any study. Therefore, it remains uncertain whether observed changes in the prevalence of antibiotic resistance after intervention were causally related to the intervention. Appropriate choices of study design, primary end point (colonization rates rather than infection rates) and statistical tests, determination of colonization routes, and control of potential confounders are needed to increase validity of intervention studies.

The intensive care unit as a research laboratory: developing strategies to prevent antimicrobial resistance

OBJECTIVE

To assemble the available clinical data on the prevention of antimicrobial resistance in the intensive care unit (ICU) setting.

DATA SOURCE

A MEDLINE database search and references from identified articles were employed to obtain the literature relating to the prevention of antimicrobial resistance in the ICU.

CONCLUSIONS

The ICU presents a unique environment for the conduct of clinical research. The closed physical space with centralized patient management and efficient data recovery allows important clinical questions to be evaluated in a timely manner. Antimicrobial resistance has emerged as an important determinant of mortality for patients in the ICU. Additionally, there is currently a limited pipeline of new agents for the treatment of emerging bacteria with new resistance genes that pose an increasing threat to the ICU patient. Effective strategies for the prevention of antimicrobial resistance within ICUs are available and should be implemented aggressively. These strategies can be divided into non-pharmacologic infection- control strategies (e.g., routine hand hygiene, infection-specific prevention protocols) and antibiotic management strategies (e.g., shorter courses of appropriate antibiotics, narrowing of the antimicrobial spectrum on the basis of culture results). Additional studies conducted in ICUs are needed urgently to identify the optimal approaches for the management of antibiotics in order to balance the need for efficacy with the ability to minimize resistance.

Risk factors for the isolation of multi-drug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa: a systematic review of the literature

An understanding of the epidemiology of multi-drug-resistant (MDR) Acinetobacter baumannii and Pseudomonas aeruginosa infections is necessary in order to develop strategies to curtail their spread. For this purpose, the evidence linking the isolation of MDR A. baumannii and P. aeruginosa with specific risk factors was evaluated. PubMed was searched for the 20-year period from September 1985 to September 2005, and eligible studies were considered to be those that: (1) linked the isolation of A. baumannii and P. aeruginosa with specific risk factors; (2) described the characteristics of the affected patients in detail; and (3) provided data on the antibiotic resistance profile of the isolated micro-organisms. Fifty-five studies were found referring to A. baumannii (28 with case-control methodology and 27 outbreak investigations without case-control methodology), and 42 studies were found referring to P. aeruginosa (25 with case-control methodology and 17 outbreak investigations without case-control methodology). Although heterogeneous study designs and investigated risk factors limited this analysis, it was concluded that acquisition and spread of these micro-organisms appear to be related to a large number of variables. Among the most important were deficiencies in the implementation of infection control guidelines and the use of broad-spectrum antibiotics. Use of carbapenems and third-generation cephalosporins appear to be related to the development of an MDR phenotype by A. baumannii, while carbapenems and fluoroquinolones are implicated in MDR P. aeruginosa. The diversity of risk factors associated with the development of MDR A. baumannii and P. aeruginosa suggests that a separate outbreak investigation should be performed in each hospital setting. The development of innovative control strategies is needed in order to limit the spread of these pathogens.

Neues in der perioperativen antibiotischen Prophylaxe

Perioperative antimicrobial prophylaxis (PAP) leads to a reduction in surgical site infections. The aim of PAP is adequate serum and tissue concentrations of the antimicrobial drug in the field of operation. The antibiotic must be effective against the expected pathogens during the operation, safe, and have the fewest possible side effects. The indication for PAP should take into account the risks of the operative procedure and especially the individual risk factors of the patient. Depending on pharmacokinetics, the antibiotic should be administered within 60 min before incision. After closure of the wound, further applications of the antibiotic drug have no influence on the infection rate of the wound but do increase the side effects (resistance, CDT colitis, allergy). Operation-specific recommendations according to guidelines of the Paul Ehrlich Society are given.

Effect of Antibiotic Heterogeneity on the Development of Infections with Antibiotic-resistant Gram-negative Organisms in a Non-intensive Care Unit Surgical Ward

BACKGROUND

Heterogeneous antibiotic use has been suggested to limit the emergence of resistance, but determining the optimal strategy is difficult.

METHODS

We developed a new strategy, termed "periodic antibiotic monitoring and supervision" (PAMS) program in a non-ICU surgical ward. The 2-year prospective study was divided into a 1-year observation period and a 1-year PAMS period. The use of four major classes of antibiotics in empirical therapy for Gram-negative rod (GNR) infections was supervised. During the PAMS program, recommended, restricted, and off-supervised classes of antibiotics were changed every 3 months according to the usage pattern of the antibiotics in the preceding term.

RESULTS

Cefepime (45.5%) and imipenem/cilastatin (39.4%) were the most common antibiotics of choice during the observation period. The use of these antibiotics decreased significantly during the PAMS period, and that of fluoroquinolones and extended-spectrum penicillin/beta-lactamase inhibitor increased (4.8% vs. 21.4% and 2.4% vs. 21.4%, P<0.01 respectively). Outcome analysis demonstrated a tendency toward reduction in the incidence of resistant GNR infections (P=0.079) and that of Pseudomonas aeruginosa (P=0.053). The incidence of resistant Gram-positive core infections did not decrease. Analysis of antibiotic susceptibility to GNR revealed no significant beneficial results for any antibiotics.

CONCLUSIONS

As significant changes were not observed, the PAMS program is not generally applicable and heterogeneous antibiotic use as a way of reducing infections with resistant GNR in non-ICU surgical wards was not established.

Reduction in acquisition of vancomycin-resistant enterococcus after enforcement of routine environmental cleaning measures

BACKGROUND

The role of environmental contamination in nosocomial cross-transmission of antibiotic-resistant bacteria has been unresolved. Using vancomycin-resistant enterococci (VRE) as a marker organism, we investigated the effects of improved environmental cleaning with and without promotion of hand hygiene adherence on the spread of VRE in a medical intensive care unit.

METHODS

The study comprised a baseline period (period 1), a period of educational intervention to improve environmental cleaning (period 2), a "washout" period without any specific intervention (period 3), and a period of multimodal hand hygiene intervention (period 4). We performed cultures for VRE of rectal swab samples obtained from patients at admission to the intensive care unit and daily thereafter, and we performed cultures of environmental samples and samples from the hands of health care workers twice weekly. We measured patient clinical and demographic variables and monitored intervention adherence frequently.

RESULTS

Our study included 748 admissions to the intensive care unit over a 9-month period. VRE acquisition rates were 33.47 cases per 1000 patient-days at risk for period 1 and 16.84, 12.09, and 10.40 cases per 1000 patient-days at risk for periods 2, 3, and 4, respectively. The mean (+/-SD) weekly rate of environmental sites cleaned increased from 0.48+/-0.08 at baseline to 0.87+/-0.08 in period 2; similarly high cleaning rates persisted in periods 3 and 4. Mean (+/-SD) weekly hand hygiene adherence rate was 0.40+/-0.01 at baseline and increased to 0.57+/-0.11 in period 2, without a specific intervention to improve adherence, but decreased to 0.29+/-0.26 in period 3 and 0.43+/-0.1 in period 4. Mean proportions of positive results of cultures of environmental and hand samples decreased in period 2 and remained low thereafter. In a Cox proportional hazards model, the hazard ratio for acquiring VRE during periods 2-4 was 0.36 (95% confidence interval, 0.19-0.68); the only determinant explaining the difference in VRE acquisition was admission to the intensive care unit during period 1.

CONCLUSIONS

Decreasing environmental contamination may help to control the spread of some antibiotic-resistant bacteria in hospitals.

Targeting mechanisms of Pseudomonas aeruginosa pathogenesis

Pseudomonas aeruginosa is an opportunistic pathogen responsible for ventilator-acquired pneumonia, acute lower respiratory tract infections in immunocompromised patients and chronic respiratory infections in cystic fibrosis patients. High incidence, infection severity and increasing resistance characterize P. aeruginosa infections, highlighting the need for new therapeutic options. One such option is to target the many pathogenic mechanisms conferred to P. aeruginosa by its large genome encoding many different virulence factors. This article reviews the pathogenic mechanisms and potential therapies targeting these mechanisms in P. aeruginosa respiratory infections.

Strategies to prevent antimicrobial resistance in the intensive care unit

OBJECTIVE

To assemble the available clinical data for the prevention of antimicrobial resistance into practical recommendations for clinicians.

DATA SOURCE

A Medline database and references from identified articles were employed to perform a literature search relating to the prevention of antimicrobial resistance.

CONCLUSIONS

Antimicrobial resistance has emerged as an important determinant of mortality for patients in the intensive care unit. This is largely due to the increasing presence of pathogenic microorganisms with resistance to existing antimicrobial agents, resulting in the administration of inappropriate treatment. Effective strategies for the prevention of antimicrobial resistance within intensive care units are available and should be aggressively implemented. These strategies can be divided into nonpharmacologic infection control strategies (e.g., routine hand hygiene, implementation of infection-specific prevention protocols) and antibiotic management strategies (e.g., shorter courses of appropriate antibiotic treatment, narrowing of antimicrobial spectrum based on culture results). Increasing current efforts aimed at the prevention of antimicrobial resistance is especially important given the limited availability of new antimicrobial drug classes for the foreseeable future.

Bench-to-bedside review: antimicrobial utilization strategies aimed at preventing the emergence of bacterial resistance in the intensive care unit

Antimicrobial resistance has emerged as one of the most important issues complicating the management of critically ill patients with infection. This is largely due to the increasing presence of pathogenic microorganisms with resistance to existing antimicrobial agents resulting in the administration of inappropriate treatment. Effective strategies for the prevention of antimicrobial resistance within intensive care units are available and should be aggressively implemented. The importance of preventing antimicrobial resistance is magnified by the limited availability of new antimicrobial drug classes for the foreseeable future.

The therapeutic challenge of Gram-negative sepsis: Prolonging the lifespan of a scarce resource

Mortality from severe bacterial sepsis remains high. The pathogenesis involves production of pro and anti-inflammatory cytokines which mediate: neutrophil adhesion to the endothelium, diffuse capillary leak, disseminated intravascular coagulation, vasodilatation and mitochondrial dysfunction, all of which culminate in microcirculatory failure. Therapy is multifaceted. As described in 'the surviving sepsis guidelines', many therapeutic interventions, such as early goal-directed resuscitation, low dose intravenous steroids, strict glucose control, recombinant activated protein C and ventilation according to ARDS- net criteria are critical to survival. However appropriate empiric antibiotic therapy initiated early is pivotal. Empiric therapy should be designed with regard to the bacterial epidemiology within the unit and the aim should be to optimise outcome while yet attempting to reduce the potential for resistance development. Antibiotic therapy for resistant organisms consists of the carbapenems, including ertapenem for ESBL's, cefepime, piperacillin/tazobactam and, on occasion, the Gram-negative quinolones, ciprofloxacin and levofloxacin. Consideration should be given to the possibility of 'collateral damage', where overuse of an antibiotic predisposes to multi-drug resistance. Antibiotics should be limited, where possible, to those organisms that are pathogens and not colonisers and should be discontinued if sepsis is not confirmed or there is rapid resolution of clinical indicators of sepsis. De-escalation strategies should be consistently employed and the duration of therapy should be tailored to clinical response. Continuation beyond 8 days is generally detrimental in terms of the potential for superinfection with resistant organisms. Failure of response necessitates, initially, a re-evaluation of source control and obsessive culturing of likely sites of sepsis prior to random antibiotic changes.