Variability in antibiotic prescribing patterns and outcomes in patients with clinically suspected ventilator-associated pneumonia

Disease Risk and Mortality Prediction in Intensive Care Patients with Pneumonia. Australian and New Zealand Practice in Intensive Care (ANZPIC II)

This study of ventilated patients investigated pneumonia risk factors and outcome predictors in 476 episodes of pneumonia (48% community-acquired pneumonia, 24% hospital-acquired pneumonia, 28% ventilator-associated pneumonia) using a prospective survey in 14 intensive care units within Australia and New Zealand. For community acquired pneumonia, mortality increased with immunosuppression (OR 5.32, CI 95% 1.58–17.99, P<0.01), clinical signs of consolidation (OR 2.43, CI 95% 1.09–5.44, P=0.03) and Sepsis-Related Organ Failure Assessment (SOFA) scores (OR 1.19, CI 95% 1.08–1.30, P<0.001) but improved if appropriate antibiotic changes were made within three days of intensive care unit admission (OR 0.42, CI 95% 0.20–0.86, P=0.02). For hospital-acquired pneumonia, immunosuppression (OR 6.98, CI 95% 1.16–42.2, P=0.03) and non-metastatic cancer (OR 3.78, CI 95% 1.20–11.93, P=0.02) were the principal mortality predictors. Alcoholism (OR 7.80, CI 95% 1.20–17.50, P<0.001), high SOFA scores (OR 1.44, CI 95% 1.20–1.75, P=0.001) and the isolation of “high risk” organisms including Pseudomonas aeruginosa, Acinetobacter spp, Stenotrophomonas spp and methicillin resistant Staphylococcus aureus (OR 4.79, CI 95% 1.43–16.03, P=0.01), were associated with increased mortality in ventilator-associated pneumonia. The use of non-invasive ventilation was independently protective against mortality for patients with community-acquired and hospital-acquired pneumonia (OR 0.35, CI 95% 0.18–0.68, P=0.002). Mortality was similar for patients requiring both invasive and non-invasive ventilation and non-invasive ventilation alone (21% compared with 20% respectively, P=0.56).

Pneumonia risks and mortality predictors in Australian and New Zealand ICUs vary with pneumonia type. A history of alcoholism is a major risk factor for mortality in ventilator-associated pneumonia, greater in magnitude than the mortality effect of immunosuppression in hospital-acquired pneumonia or community-acquired pneumonia. Non-invasive ventilation is associated with reduced ICU mortality. Clinical signs of consolidation worsen, while rationalising antibiotic therapy within three days of ICU admission improves mortality for community-acquired pneumonia patients.

Management of ventilator-associated pneumonia in intensive care units: a mixed methods study assessing barriers and facilitators to guideline adherence

Background

Guidelines from the Infectious Diseases Society of America/The American Thoracic Society (IDSA/ATS) provide recommendations for diagnosis and treatment of ventilator-associated pneumonia (VAP). However, the mere presence of guidelines is rarely sufficient to promote widespread adoption and uptake. Using the Systems Engineering Initiative for Patient Safety (SEIPS) model framework, we undertook a study to understand barriers and facilitators to the adoption of the IDSA/ATS guidelines.

Methods

We conducted surveys and focus group discussions of different health care providers involved in the management of VAP. The setting was medical-surgical ICUs at a tertiary academic hospital and a large multispecialty rural hospital in Wisconsin, USA.

Results

Overall, we found that 55 % of participants indicated that they were aware of the IDSA/ATS guideline. The top ranked barriers to VAP management included: 1) having multiple physician groups managing VAP, 2) variation in VAP management by differing ICU services, 3) physicians and level of training, and 4) renal failure complicating doses of antibiotics.

Facilitators to VAP management included presence of multidisciplinary rounds that include nurses, pharmacist and respiratory therapists, and awareness of the IDSA/ATS guideline. This awareness was associated with receiving effective training on management of VAP, keeping up to date on nosocomial infection literature, and belief that performing a bronchoscopy to diagnose VAP would help with expeditious diagnosis of VAP.

Conclusions

Findings from our study complement existing studies by identifying perceptions of the many different types of healthcare workers in ICU settings. These findings have implications for antibiotic stewardship teams, clinicians, and organizational leaders.

Inapparent Outbreaks of Ventilator-Associated Pneumonia An Ecologic Analysis of Prevention and Cohort Studies

Objective:

To compare ventilator-associated pneumonia (VAP) rates and patterns of isolates across studies of antibiotic and non-antibiotic methods for preventing VAP.

Design:

With the use of 42 cohort study groups as the reference standard, the prevalence of VAP was modeled in two linear regressions: one with the control groups and the other with the intervention groups of 96 VAP prevention studies. The proportion of patients admitted with trauma and the VAP diagnostic criteria were used as ecologic correlates. Also, the patterns of pathogenic isolates were available for 117 groups.

Results:

In the first regression model, the VAP rates for the control groups of antibiotic-based prevention studies were at least 18 (CI95, 12 to 24) per 100 patients higher than those in the cohort study groups (P< .001). By contrast, comparisons of cohort study groups with all other control and intervention groups in the first and second regression models yielded differences that were less than 6 per 100 and not significant (P> .05). For control groups with VAP rates greater than 35%, the patterns of VAP isolates, such as the proportion ofStaphylococcus aureus,more closely resembled those in the corresponding intervention groups than in the cohort groups.

Conclusions:

The rates of VAP in the control groups of the antibiotic prevention studies were significantly higher than expected and the patterns of pathogenic isolates were unusual. These observations suggest that inapparent outbreaks of VAP occurred in these studies. The possibility remains that antibiotic-based VAP prevention presents a major cross-infection hazard.

SaMpling Antibiotics in Renal Replacement Therapy (SMARRT): an observational pharmacokinetic study in critically ill patients

Background

Optimal antibiotic dosing is key to maximising patient survival, and minimising the emergence of bacterial resistance. Evidence-based antibiotic dosing guidelines for critically ill patients receiving RRT are currently not available, as RRT techniques and settings vary greatly between ICUs and even individual patients. We aim to develop a robust, evidence-based antibiotic dosing guideline for critically ill patients receiving various forms of RRT. We further aim to observe whether therapeutic antibiotic concentrations are associated with reduced 28-day mortality.

Methods/Design

We designed a multi-national, observational pharmacokinetic study in critically ill patients requiring RRT. The study antibiotics will be vancomycin, linezolid, piperacillin/tazobactam and meropenem. Pharmacokinetic sampling of each patient’s blood, RRT effluent and urine will take place during two separate dosing intervals. In addition, a comprehensive data set, which includes the patients’ demographic and clinical parameters, as well as modality, technique and settings of RRT, will be collected. Pharmacokinetic data will be analysed using a population pharmacokinetic approach to identify covariates associated with changes in pharmacokinetic parameters in critically ill patients with AKI who are undergoing RRT for the five commonly prescribed antibiotics.

Discussion

Using the comprehensive data set collected, the pharmacokinetic profile of the five antibiotics will be constructed, including identification of RRT and other factors indicative of the need for altered antibiotic dosing requirements. This will enable us to develop a dosing guideline for each individual antibiotic that is likely to be relevant to any critically ill patient with acute kidney injury receiving any of the included forms of RRT.

Trial registration

Australian New Zealand Clinical Trial Registry (ACTRN12613000241730) registered 28 February 2013

Incidence and outcome of inappropriate in-hospital empiric antibiotics for severe infection: a systematic review and meta-analysis

INTRODUCTION

The aims of this study were to explore the incidence of in-hospital inappropriate empiric antibiotic use in patients with severe infection and to identify its relationship with patient outcomes.

METHODS

Medline (from 2004 to 2014) was systematically searched by using predefined inclusion criteria. Reference lists of retrieved articles were screened for additional relevant studies. The systematic review included original articles reporting a quantitative measure of the association between the use of (in)appropriate empiric antibiotics in patients with severe in-hospital infections and their outcomes. A meta-analysis, using a random-effects model, was conducted to quantify the effect on mortality by using risk ratios.

RESULTS

In total, 27 individual articles fulfilled the inclusion criteria. The percentage of inappropriate empiric antibiotic use ranged from 14.1% to 78.9% (Q1-Q3: 28.1% to 57.8%); 13 of 27 studies (48.1%) described an incidence of 50% or more. A meta-analysis for 30-day mortality and in-hospital mortality showed risk ratios of 0.71 (95% confidence interval 0.62 to 0.82) and 0.67 (95% confidence interval 0.56 to 0.80), respectively. Studies with outcome parameter 28-day and 60-day mortality reported significantly (P ≤0.02) higher mortality rates in patients receiving inappropriate antibiotics. Two studies assessed the total costs, which were significantly higher in both studies (P ≤0.01).

CONCLUSIONS

This systematic review with meta-analysis provides evidence that inappropriate use of empiric antibiotics increases 30-day and in-hospital mortality in patients with a severe infection.

Quality indicators on the use of antimicrobials in critically ill patients

Quality indicators have been applied to many areas of health care in recent years, including intensive care. However, they have not been specifically developed and validated for antimicrobial use in critically ill patients. Antimicrobials play a key role in intensive care units not only in the prognosis of each individual patient, but also in the development of resistance and changes in the flora in this setting. Evaluating the use of these agents is complex in the intensive care unit, however, because the indications vary greatly and antimicrobial treatment is often changed during admission. We designed and developed specific quality indicators regarding the use of antimicrobials in critically ill patients admitted to the intensive care unit. These indicators are proposed as a tool for application in intensive care units to detect problems in the use of antimicrobials. Future trials are needed, however, to validate these indicators in a large population over time.

Ventilator-Associated Pneumonia: When to hold the breath?

Ventilator-associated pneumonia (VAP) is the most common infection in mechanically ventilated patients, and carries the highest mortality. An early diagnosis and definitive management not only reduces the overall mortality, but also brings down the burden of health care to the patient by reducing the cost, length of Intensive Care Unit (ICU) stay, duration of mechanical ventilation, and so on. Out of the various scoring systems, the Clinical Pulmonary Infection Score (CPIS) calculation for VAP has a good sensitivity (72%) and specificity (85%) and the targeted antibiotic therapy in the appropriate dosage is found to be more beneficial than empirical treatment. Although controversies persist on several issues, preventive strategies like head elevation by 30 degrees, cuff pressure monitoring, avoidance of sedatives and muscle relaxants, and so on, have been found to reduce the occurrence of VAP.

Comparison of colistin-carbapenem, colistin-sulbactam, and colistin plus other antibacterial agents for the treatment of extremely drug-resistant Acinetobacter baumannii bloodstream infections

The purpose of this investigation was to compare the efficacy of colistin-based therapies in extremely drug-resistant Acinetobacter spp. bloodstream infections (XDR-ABSI). A retrospective study was conducted in 27 tertiary-care centers from January 2009 to August 2012. The primary end-point was 14-day survival, and the secondary end-points were clinical and microbiological outcomes. Thirty-six and 214 patients [102 (47.7%): colistin-carbapenem (CC), 69 (32.2%): colistin-sulbactam (CS), and 43 (20.1%: tigecycline): colistin with other agent (CO)] received colistin monotherapy and colistin-based combinations, respectively. Rates of complete response/cure and 14-day survival were relatively higher, and microbiological eradication was significantly higher in the combination group. Also, the in-hospital mortality rate was significantly lower in the combination group. No significant difference was found in the clinical (p = 0.97) and microbiological (p = 0.92) outcomes and 14-day survival rates (p = 0.79) between the three combination groups. Neither the timing of initial effective treatment nor the presence of any concomitant infection was significant between the three groups (p > 0.05) and also for 14-day survival (p > 0.05). Higher Pitt bacteremia score (PBS), Acute Physiology and Chronic Health Evaluation II (APACHE II) score, Charlson comorbidity index (CCI), and prolonged hospital and intensive care unit (ICU) stay before XDR-ABSI were significant risk factors for 14-day mortality (p = 0.02, p = 0.0001, p = 0.0001, p = 0.02, and p = 0.01, respectively). In the multivariable analysis, PBS, age, and duration of ICU stay were independent risk factors for 14-day mortality (p < 0.0001, p < 0.0001, and p = 0.001, respectively). Colistin-based combination therapy resulted in significantly higher microbiological eradication rates, relatively higher cure and 14-day survival rates, and lower in-hospital mortality compared to colistin monotherapy. CC, CS, and CO combinations for XDR-ABSI did not reveal significant differences with respect to 14-day survival and clinical or microbiological outcome before and after propensity score matching (PSM). PBS, age, and length of ICU stay were independent risk factors for 14-day mortality.

Ventilator-associated pneumonia: overdiagnosis and treatment are common in medical and surgical intensive care units

OBJECTIVE

Diagnosing ventilator-associated pneumonia (VAP) is difficult, and misdiagnosis can lead to unnecessary and prolonged antibiotic treatment. We sought to quantify and characterize unjustified antimicrobial use for VAP and identify risk factors for continuation of antibiotics in patients without VAP after 3 days.

METHODS

Patients suspected of having VAP were identified in 6 adult intensive care units (ICUs) over 1 year. A multidisciplinary adjudication committee determined whether the ICU team's VAP diagnosis and therapy were justified, using clinical, microbiologic, and radiographic data at diagnosis and on day 3. Outcomes included the proportion of VAP events misdiagnosed as and treated for VAP on days 1 and 3 and risk factors for the continuation of antibiotics in patients without VAP after day 3.

RESULTS

Two hundred thirty-one events were identified as possible VAP by the ICUs. On day 1, 135 (58.4%) of them were determined to not have VAP by the committee. Antibiotics were continued for 120 (76%) of 158 events without VAP on day 3. After adjusting for acute physiology and chronic health evaluation II score and requiring vasopressors on day 1, sputum culture collection on day 3 was significantly associated with antibiotic continuation in patients without VAP. Patients without VAP or other infection received 1,183 excess days of antibiotics during the study.

CONCLUSIONS

Overdiagnosis and treatment of VAP was common in this study and led to 1,183 excess days of antibiotics in patients with no indication for antibiotics. Clinical differences between non-VAP patients who had antibiotics continued or discontinued were minimal, suggesting that clinician preferences and behaviors contribute to unnecessary prescribing.

Empirical Antibiotic Therapy for Ventilator-Associated Pneumonia

Ventilator-associated pneumonia (VAP) is the most common infectious complication in the intensive care unit. It can increase duration of mechanical ventilation, length of stay, costs, and mortality. Improvements in the administration of empirical antibiotic therapy have potential to reduce the complications of VAP. This review will discuss the current data addressing empirical antibiotic therapy and the effect on mortality in patients with VAP. It will also address factors that could improve the administration of empirical antibiotics and directions for future research.

Nosocomial pneumonia: lessons learned

Nosocomial pneumonia remains a significant cause of hospital-acquired infection, imposing substantial economic burden on the health care system worldwide. Various preventive strategies have been increasingly used to prevent the development of pneumonia. It is now recognized that patients with health care-associated pneumonia are a heterogeneous population and that not all are at risk for infection with nosocomial pneumonia pathogens, with some being infected with the same organisms as in community-acquired pneumonia. This review discusses the risk factors for nosocomial pneumonia, controversies in its diagnosis, and approaches to the treatment and prevention of nosocomial and health care-associated pneumonia.

Factors predicting ventilator dependence in patients with ventilator-associated pneumonia

Objectives. To determine risk factors associated with ventilator dependence in patients with ventilator-associated pneumonia (VAP). Study Design. A retrospective study was conducted at Chang Gung Memorial Hospital, Kaohsiung, from January 1, 2007 to January 31, 2008. Methods. This study evaluated 163 adult patients (aged ≥18 years). Eligibility was evaluated according to the criterion for VAP, Sequential Organ Failure Assessment (SOFA) score, Acute Physiological Assessment and Chronic Health Evaluation II (APACHE II) score. Oxygenation index, underlying comorbidities, septic shock status, previous tracheostomy status, and factors related to pneumonia were collected for analysis. Results. Of the 163 VAP patients in the study, 90 patients survived, yielding a mortality rate of 44.8%. Among the 90 surviving patients, only 36 (40%) had been weaned off ventilators at the time of discharge. Multivariate logistic regression analysis was used to identify underlying factors such as congestive cardiac failure (P = 0.009), initial high oxygenation index value (P = 0.04), increased SOFA scores (P = 0.01), and increased APACHE II scores (P = 0.02) as independent predictors of ventilator dependence. Results from the Kaplan-Meier method indicate that initial therapy with antibiotics could increase the ventilator weaning rate (log Rank test, P < 0.001). Conclusions. Preexisting cardiopulmonary function, high APACHE II and SOFA scores, and high oxygenation index were the strongest predictors of ventilator dependence. Initial empiric antibiotic treatment can improve ventilator weaning rates at the time of discharge.

Empiric antibiotics pending bronchoalveolar lavage data in patients without pneumonia significantly alters the flora, but not the resistance profile, if a subsequent pneumonia develops

INTRODUCTION

Ventilator-associated pneumonia (VAP) occurs in up to 25% of mechanically ventilated patients, with an associated mortality up to 50%. Early diagnosis and appropriate empiric antibiotic coverage of VAP are crucial. Given the multitude of noninfectious clinical and radiographic anomalies within trauma patients, microbiology from bronchioalveolar lavage (BAL) is often needed. Empiric antibiotics are administered while awaiting BAL culture data. Little is known about the effects of these empiric antibiotics on patients with negative BAL microbiology if a subsequent VAP occurs during the same hospital course.

METHODS

This is a retrospective chart review of intubated trauma patients undergoing BAL for suspected pneumonia over a 3-y period at a Level 1 trauma center. All patients with suspected VAP undergoing a BAL receive empiric antibiotics. If microbiology data are negative at 72 h, all antibiotics are stopped; however, if the BAL returns with ≥10(5) colony-forming units per milliliter, the diagnosis of VAP is confirmed. We divided patients into three groups. Group 1 consisted of patients in whom the initial BAL was positive for VAP. Group 2 consisted of patients with an initial negative BAL, who subsequently developed VAP at a later point in the hospital course. Group 3 consisted of patients with negative BAL who did not develop a subsequent VAP.

RESULTS

We obtained 499 BAL specimens in 185 patients over the 3-y period. A total of 14 patients with 23 BAL specimens initially negative for VAP subsequently developed VAP later during the same hospital stay. These patients did not have an increase in the hospital length of stay, intensive care unit days, ventilator days, or mortality compared with those who had a positive culture on the first suspicion of VAP. There was a significant increase in the percentage of Enterobacter (21% versus 8%) and Morganella (8% versus 0%) as the causative organism in these 14 patients when the VAP occurred. Furthermore, the profile of the top two organisms in each group changed. Enterobacter (21%) and Pseudomonas (17%) were the principal organisms in the initial BAL-negative group, whereas the two predominant strains in the initial positive BAL group were methicillin-sensitive Staphylococcus aureus (21%) and Haemophilus influenza (11%). Interestingly, methicillin-resistant S. aureus remained the third most common organism in both groups. Empiric antibiotics also did not seem to induce the growth of multidrug-resistant organisms, and there was no increased rate of secondary infections such as Clostridium difficile.

CONCLUSIONS

Ventilator-associated pneumonia remains a significant cause of morbidity and mortality in mechanically ventilated trauma patients. The diagnosis and treatment of VAP continue to be challenging. Once clinically suspected, empiric coverage decreases morbidity and mortality. Our data demonstrate that patients who receive empiric coverage exhibit a significantly different microbiologic profile compared with those who had an initial positive BAL culture. Initial empiric antibiotics in BAL-negative patients were not associated with an increase in multidrug-resistant organisms, hospital, or intensive care unit length of stay, ventilator days, and mortality or secondary infections.

What is the efficacy and safety of colistin for the treatment of ventilator-associated pneumonia? A systematic review and meta-regression

BACKGROUND

Experience with intravenous and aerosolized forms of colistin for the treatment of ventilator-associated pneumonia (VAP) in patients without cystic fibrosis is limited. We aimed to assess the safety and efficacy of colistin for the treatment of VAP.

METHODS

We searched MEDLINE and Cochrane Database of Systematic Reviews for studies comparing colistin vs other antibiotics for treatment of VAP in patients without cystic fibrosis. QUOROM guidelines were followed, the I(2) method was used for heterogeneity, and a random-effects model for odds ratio (OR) estimates.

RESULTS

Six controlled studies met the inclusion criteria. Clinical response did not differ significantly between colistin and control groups (OR, 1.14; 95% confidence interval [CI], .74-1.77; P = .56; I(2) = 0%). The efficacy of colistin was independent of study design (prospective OR, 0.89 [95% CI, .48-1.66; P = .71; I(2) = 0%]; retrospective OR, 1.45 [95% CI, .79-2.68; P = .23; I(2) = 0%]); randomized trials OR, 0.86 [95% CI, .43-1.74; P = .68; I(2) = 0%]). There was no indication of a significant change in clinical response after controlling for concomitant antibiotic treatment (intercept, 0.121; slope, 0.0315; P = .95). Treatment with colistin vs controls did not affect hospital mortality (OR, 0.92; 95% CI, .50-1.67; P = .78; I(2) = 34.59%) or nephrotoxicity (OR, 1.14; 95% CI, .59-2.20; P = .69; I(2) = 0%). Fourteen single-arm studies have been analyzed, and the results were in concordance with the findings of the controlled studies.

CONCLUSIONS

Our results suggest that colistin may be as safe and as efficacious as standard antibiotics for the treatment of VAP.

Clinical practice guidelines for hospital-acquired pneumonia and ventilator-associated pneumonia in adults

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are important causes of morbidity and mortality, with mortality rates approaching 62%. HAP and VAP are the second most common cause of nosocomial infection overall, but are the most common cause documented in the intensive care unit setting. In addition, HAP and VAP produce the highest mortality associated with nosocomial infection. As a result, evidence-based guidelines were prepared detailing the epidemiology, microbial etiology, risk factors and clinical manifestations of HAP and VAP. Furthermore, an approach based on the available data, expert opinion and current practice for the provision of care within the Canadian health care system was used to determine risk stratification schemas to enable appropriate diagnosis, antimicrobial management and nonantimicrobial management of HAP and VAP. Finally, prevention and risk-reduction strategies to reduce the risk of acquiring these infections were collated. Future initiatives to enhance more rapid diagnosis and to effect better treatment for resistant pathogens are necessary to reduce morbidity and improve survival.

Systematic review and meta-analysis of the efficacy of appropriate empiric antibiotic therapy for sepsis

Quantifying the benefit of early antibiotic treatment is crucial for decision making and can be assessed only in observational studies. We performed a systematic review of prospective studies reporting the effect of appropriate empirical antibiotic treatment on all-cause mortality among adult inpatients with sepsis. Two reviewers independently extracted data. Risk of bias was assessed using the Newcastle-Ottawa score. We calculated unadjusted odds ratios (ORs) with 95% confidence intervals for each study and extracted adjusted ORs, with variance, methods, and covariates being used for adjustment. ORs were pooled using random-effects meta-analysis. We examined the effects of methodological and clinical confounders on results through subgroup analysis or mixed-effect meta-regression. Seventy studies were included, of which 48 provided an adjusted OR for inappropriate empirical antibiotic treatment. Inappropriate empirical antibiotic treatment was associated with significantly higher mortality in the unadjusted and adjusted comparisons, with considerable heterogeneity occurring in both analyses (I(2) > 70%). Study design, time of mortality assessment, the reporting methods of the multivariable models, and the covariates used for adjustment were significantly associated with effect size. Septic shock was the only clinical variable significantly affecting results (it was associated with higher ORs). Studies adjusting for background conditions and sepsis severity reported a pooled adjusted OR of 1.60 (95% confidence interval = 1.37 to 1.86; 26 studies; number needed to treat to prevent one fatal outcome, 10 patients [95% confidence interval = 8 to 15]; I(2) = 46.3%) given 34% mortality with inappropriate empirical treatment. Appropriate empirical antibiotic treatment is associated with a significant reduction in all-cause mortality. However, the methods used in the observational studies significantly affect the effect size reported. Methods of observational studies assessing the effects of antibiotic treatment should be improved and standardized.

A survival benefit of combination antibiotic therapy for serious infections associated with sepsis and septic shock is contingent only on the risk of death: a meta-analytic/meta-regression study

OBJECTIVE

To assess whether a potential benefit with combination antibiotic therapy is restricted to the most critically ill subset of patients, particularly those with septic shock.

DATA SOURCES

OVID MEDLINE (1950-October 2009), EMBASE (1980-October 2009), the Cochrane Central Register of Controlled Trials (to third quarter 2009), the ClinicalTrial.gov database, and the SCOPUS database.

STUDY SELECTION

Randomized or observational studies of antimicrobial therapy of serious bacterial infections potentially associated with sepsis or septic shock. Fifty studies met entry criteria.

DATA EXTRACTION

Study design, mortality/clinical response, and other variables were extracted independently by two reviewers. When possible, study datasets were split into mutually exclusive groups with and without shock or critical illness.

DATA SYNTHESIS

Although a pooled odds ratio indicated no overall mortality/clinical response benefit with combination therapy (odds ratio, 0.856; 95% confidence interval, 0.71-1.03; p = .0943; I = 45.1%), stratification of datasets by monotherapy mortality risk demonstrated substantial benefit in the most severely ill subset (monotherapy risk of death >25%; odds ratio of death, 0.51; 95% confidence interval, 0.41-0.64; I = 8.6%). Of those datasets that could be stratified by the presence of shock/critical illness, the more severely ill group consistently demonstrated increased efficacy of a combination therapy strategy (odds ratio, 0.49; 95% confidence interval, 0.35-0.70; p < .0001; I = 0%). An increased risk of death was found in low-risk patients (risk of death <or=15% in the monotherapy arm) exposed to combination therapy (odds ratio, 1.53; 95% confidence interval, 1.16-2.03; p = .003; I = 8.2%). Meta-regression indicated that efficacy of combination therapy was dependent only on the risk of death in the monotherapy group.

CONCLUSION

Combination antibiotic therapy improves survival and clinical response of high-risk, life-threatening infections, particularly those associated with septic shock but may be detrimental to low-risk patients.

Management of nosocomial pneumonia on a medical ward: a comparative study of outcomes and costs of invasive procedures

The goal of this study was to compare outcomes and costs of two management strategies for non-ventilator-associated nosocomial pneumonia (NP) in a medical ward. In this single-centre study, NP patients (n = 68) were randomized to receive non-invasive management (NIM) with immediate empirical antibiotic treatment (n = 34), or invasive management (IM) based on protected brush sampling of specimens (n = 34). The economic analysis adopted the hospital's perspective and took into account only direct costs. Baseline characteristics did not differ significantly between the two patient groups. The most frequently isolated organisms were Staphylococcus (25.4%), Streptococcus (23.7%) and Pseudomonas (18.6%) species. The 28-day clinical cure rate did not differ notably between the two groups (NIM, 79.4%; IM, 73.5%). Mortality at 28 days tended to be lower in the NIM group (10.0% vs. 21.8%). Mean antibiotic costs were lower in the IM group (euro194 +/- 355 vs. euro300 +/- 335, p <0.001) but overall management costs were similar (respectively, euro367 +/- 355 and euro346 +/- 363 in the IM and NIM groups, p = 0.08). With respect to both outcome and cost, this study does not support routine management of NP in medical wards using invasive procedures.

Impact of inappropriate antibiotic therapy on mortality in patients with ventilator-associated pneumonia and blood stream infection: a meta-analysis

OBJECTIVES

Studies have found that initial treatment of ventilator-associated pneumonia (VAP) and blood stream infections (BSI) with inappropriate antimicrobial therapy is associated with higher rates of mortality, but additional studies have failed to confirm this.

METHODS

Databases were searched to identify studies that met the following criteria: observational trials, patients with VAP or BSI receiving appropriate and inappropriate antimicrobial therapy, and mortality data. We conducted random-effects model meta-analyses, both with and without adjustment.

RESULTS

Meta-analyses of VAP studies using unadjusted and adjusted data indicated that inappropriate therapy significantly increased patients' odds of mortality (odds ratio [OR], 2.34; 95% confidence interval [CI], 1.51-3.63; P = .0001, I 2 = 28.5% and OR, 3.03; 95% CI, 1.12-8.19; P = .0292, I 2 = 89.2%, respectively). Meta-analyses of BSI studies using unadjusted and adjusted data showed that inappropriate therapy significantly increased patients' odds of mortality (OR, 2.33; 95% CI, 1.96-2.76; P < .0001, I 2 = 48.7% and OR, 2.28; 95% CI, 1.43-3.65; P = .0006, I 2 = 88.2%, respectively).

CONCLUSIONS

There appears to be an association between initial inappropriate antimicrobial therapy and increased mortality in patients with VAP and BSI.

Incidence and impact on clinical outcome of infections with piperacillin/tazobactam resistant Escherichia coli in ICU: a retrospective study

BACKGROUND

Escherichia coli infections are frequent in ICU patients. The increased resistance to fluoroquinolones and amoxicillin/clavulanate of this pathogen mandates the prescription of broad-spectrum antibiotics such as piperacillin/tazobactam (PIP-TAZ) or third generation cephalosporins (3GC).

METHODS

To assess incidence and impact on clinical outcome of infections with PIP-TAZ resistant E. coli in ICU patients, we conducted a retrospective cohort study with infections due to PIP-TAZ resistant (PIP-TAZ R) or to PIP-TAZ susceptible strains (PIP-TAZ S) between 1 January 2002 and 30 June 2004.

RESULTS

Of 83 strains, 13 were PIP-TAZ R: 2 strains produced an extended-spectrum beta-lactamase (2%), 11 produced a high level penicillinase (13%). Prior amoxicillin or amoxicillin/clavulanate prescription was reported in 7 cases (54%) of infections with PIP-TAZ R isolates and in 15 cases (21%) of infections with PIP-TAZ S isolates (p = 0.03). Time of onset of the infection from hospital admission was longer in case of infections with PIP-TAZ R than with PIP-TAZ S isolates (22 +/- 32 vs 10 +/- 21 days, p = 0.01). The overall ICU mortality rate was 38%. Mortality and length of stay in ICU were similar in case of infections with PIP-TAZ R isolates and with PIP-TAZ S isolates.

CONCLUSION

Infections with PIP-TAZ R E. coli are frequent in ICU patients. No prognostic impact of this pattern of resistance was found. Prescription of PIP-TAZ for empirical treatment of E. coli infections in ICU however exposes to inappropriate therapy.

Treatment recommendations of hospital-acquired pneumonia in Asian countries: first consensus report by the Asian HAP Working Group

Many different treatment options are available for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), which are important causes of morbidity and mortality. Although guidelines for the diagnosis and treatment of HAP and VAP have been published by various American and European societies, these guidelines may not be applicable in all respects to the diagnosis and treatment of HAP and VAP in Asian countries. In addition, clinical practice may vary among Asian countries, due to such factors as availability of specific antibiotics and formulations and their relative cost. In addition, and in particular, different epidemiologic, etiologic, and resistance patterns in Asian countries may affect treatment choices compared with those in Western countries. To address these issues, the Asian-Pacific Research Foundation for Infectious Diseases, together with the Asian Network for Surveillance of Resistant Pathogens, organized the Asian HAP Working Group to discuss current clinical practices and develop consensus treatment recommendations for HAP in Asian countries. The consensus treatment recommendations, summarized herein, represent the findings of an expert panel comprising 30 representatives from 10 Asian countries.

Empiric antibiotic therapy for suspected ventilator-associated pneumonia: a systematic review and meta-analysis of randomized trials

OBJECTIVE

To compare specific antibiotic regimens, and monotherapy vs. combination therapy, for the empirical treatment of ventilator-associated pneumonia (VAP).

DESIGN

Meta-analysis.

DATA SOURCE

Medline, Embase, Cochrane register of controlled trials, study authors, and review articles.

STUDY SELECTION

We included randomized controlled trials that evaluated empirical parenteral antibiotic regimens for adult patients with clinically suspected VAP.

DATA SELECTION

Two independent review groups searched the literature, extracted data, and evaluated trial quality. The primary outcome was all-cause mortality; secondary outcomes included treatment failure. Relative risks were pooled using a random effects model.

RESULTS

We identified 41 trials randomizing 7,015 patients and comparing 29 unique regimens. Methodological quality was low, reflecting low rates of complete follow-up (43.9%), use of a double-blinded interventional strategy (14.6%), and randomization concealment (48.6%). Overall mortality was 20.3%; treatment failure occurred in 37.4% of patients who could be evaluated microbiologically. No mortality differences were observed between any of the regimens compared. Only one of three pooled comparisons yielded a significant difference for treatment failure: The combination of ceftazidime/aminoglycoside was inferior to meropenem (two trials, relative risk 0.70, 95% confidence interval 0.53-0.93). Rates of mortality and treatment failure for monotherapy compared with combination therapy were similar (11 trials, relative risk for mortality of monotherapy 0.94, confidence interval 0.76-1.16; and relative risk of treatment failure for monotherapy 0.88, confidence interval 0.72-1.07).

CONCLUSIONS

Monotherapy is not inferior to combination therapy in the empirical treatment of VAP. Available data neither identify a superior empirical regimen nor conclusively conclude that available regimens result in equivalent outcomes. Larger and more rigorous trials evaluating the choice of, and even need for, empirical therapy for VAP are needed.

Ventilator-associated pneumonia: impact of organisms on clinical resolution and medical resources utilization

BACKGROUND

Clinical resolution of ventilator-associated pneumonia (VAP) determines the duration of treatment and mechanical ventilation. The aim of this study was to evaluate the influence of organisms and their susceptibility to treatment on outcomes.

METHODS

Prospective observational study in three teaching ICUs. Sixty episodes of VAP with appropriate therapy (Haemophilus influenzae, 15 episodes; methicillin-sensitive Staphylococcus aureus [MSSA], 15 episodes; Pseudomonas aeruginosa, 15 episodes; and methicillin-resistant S aureus [MRSA], 15 episodes), and 30 episodes with initial inappropriate therapy, all due to P aeruginosa, were compared. The main outcome measures were clinical resolution variables and, in survivors, length of mechanical ventilation after VAP onset.

RESULTS

A significant delay in the resolution of hypoxemia was observed in VAP episodes due to MRSA and P aeruginosa with inappropriate antibiotic therapy (IAT) (median time to resolution, 10 and 8 days, respectively) when compared with the remaining pathogens (median time to resolution, 2 days). A multiple regression model, adjusted for disease severity, confirmed the delayed clinical resolution for MRSA and P aeruginosa with IAT. Similar associations were documented for defervescence. Among survivors, the median duration of mechanical ventilation after VAP onset was significantly longer for MRSA (17 days) and P aeruginosa IAT (11 days) when compared with episodes due to H influenzae or MSSA (6 days). Multiple regression analysis, adjusted for disease severity, confirmed that MRSA required significantly (R(2) = 0.132; p < 0.01) longer respiratory support than other organisms.

CONCLUSIONS

When treated promptly, the resolution of VAP due to MSSA, H influenzae, and P aeruginosa was comparable. The resolution of MRSA VAP, regardless of the appropriateness of initial antibiotic therapy, was associated with longer respiratory support.

Optimal management therapy for Pseudomonas aeruginosa ventilator-associated pneumonia: An observational, multicenter study comparing monotherapy with combination antibiotic therapy*

OBJECTIVE

To evaluate whether one antibiotic achieves equal outcomes compared with combination antibiotic therapy in patients with Pseudomonas aeruginosa ventilator-associated pneumonia.

DESIGN

A retrospective, multicenter, observational, cohort study.

SETTING

Five intensive care units in Spanish university hospitals.

PATIENTS

Adult patients identified to have monomicrobial episodes of ventilator-associated pneumonia with significant quantitative respiratory cultures for P. aeruginosa.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

A total of 183 episodes of monomicrobial P. aeruginosa ventilator-associated pneumonia were analyzed. Monotherapy alone was used empirically in 67 episodes, being significantly associated with inappropriate therapy (56.7% vs. 90.5%, p < .001). Hospital mortality was significantly higher in the 40 patients with inappropriate therapy compared with those at least on antibiotic with activity in vitro (72.5% vs. 23.1%, p < .05). Excess mortality associated with monotherapy was estimated to be 13.6% (95% confidence interval -2.6 to 29.9). The use of monotherapy or combination therapy in the definitive regimen did not influence mortality, length of stay, development of resistance to the definitive treatment, or appearance of recurrences. Inappropriate empirical therapy was associated with increased mortality (adjusted hazard ratio 1.85; 95% confidence interval 1.07-3.10; p = .02) in a Cox proportional hazard regression analysis, after adjustment for disease severity, but not effective monotherapy (adjusted hazard ratio 0.90; 95% confidence interval 0.50-1.63; p = .73) compared with effective combination therapy (adjusted hazard ratio 1). The other two variables also independently associated with mortality were age (adjusted hazard ratio 1.02; 95% confidence interval 1.01-1.04; p = .005) and chronic cardiac insufficiency (adjusted hazard ratio 1.90; 95% confidence interval 1.04-3.47; p = .035).

CONCLUSIONS

Initial use of combination therapy significantly reduces the likelihood of inappropriate therapy, which is associated with higher risk of death. However, administration of only one effective antimicrobial or combination therapy provides similar outcomes, suggesting that switching to monotherapy once the susceptibility is documented is feasible and safe.

Article Commentary: Strategies in the Prevention and Management of Ventilator-Associated Pneumonia

Ventilator-associated pneumonia (VAP) is a leading cause of morbidity and mortality in the intensive care unit. Prevention of VAP is possible through the use of several evidence-based strategies intended to minimize intubation, the duration of mechanical ventilation, and the risk of aspiration of oropharyngeal pathogens. Current data favor the quantitative analysis of lower respiratory tract cultures for the diagnosis of VAP, accompanied by the initiation of broad-spectrum empiric antimicrobial therapy based on patient risk factors for infection with multi-drug-resistant pathogens and data from unit-specific antibiograms. Eventual choice of antibiotic and duration of therapy are selected based on culture results and patient stability, with an emphasis on minimization of unnecessary antibiotic use.

Inadequate treatment of ventilator-associated pneumonia: risk factors and impact on outcomes

Initial antibiotic therapy is an important determinant of clinical outcomes in ventilator-associated pneumonia (VAP). Several studies have investigated this issue, with conflicting results. This study investigated risk factors of inadequate empirical antimicrobial therapy and its impact on outcomes for patients with a clinical diagnosis of VAP. The primary outcome was adequacy of antimicrobial therapy. Secondary outcomes were duration of mechanical ventilation, hospital and intensive care unit (ICU) lengths of stay, and mortality due to VAP. Mean age was 62.9+/-15.2 years, mean APACHE (Acute Physiological Assessment and Chronic Health Evaluation) II score was 20.1+/-8.1 and mean MODS (Multiple Organ Dysfunction Score) was 3.7+/-2.5. Sixty-nine (45.7%) of 151 patients with a clinical diagnosis of VAP received inadequate antimicrobial treatment for VAP initially. There were 100 (66.2%) episodes of VAP caused by multidrug-resistant pathogens, of which 56% were inadequately treated, whereas the rate of inadequate antimicrobial therapy for VAP caused by susceptible-drug pathogens was 25.5% (P<0.001). Multiple logistic regression analysis revealed that the risk of inadequate antimicrobial treatment was more than twice as great for patients with late-onset VAP [odds ratio (OR), 2.93; 95% confidence interval (CI), 1.30-6.64; P=0.01], and more than three times for patients with VAP caused by multidrug-resistant pathogens (OR, 3.07; 95% CI, 1.29-7.30; P=0.01) or with polymicrobial VAP (OR, 3.67; 95% CI, 1.21-11.12; P=0.02). Inadequate antimicrobial treatment was associated with higher mortality for patients with VAP. Two of three independent risk factors for treatment inadequacy were associated with the isolation and identification of micro-organisms.

Can the clinical pulmonary infection score impact ICU antibiotic days?

BACKGROUND

The Clinical Pulmonary Infection Score (CPIS) has been used in the intensive care unit (ICU) as a decision tool for initiation of antibiotics in suspected pneumonia and also for discontinuing antibiotics if the CPIS score is <or=6 on day three of therapy, but it is not in common clinical use. We sought to determine if application of a CPIS score<or=6 at three days could reduce antibiotic use and if a blinded committee would have a greater percentage of patients with CPIS>6 on day one receiving antibiotics empirically for pneumonia.

METHODS

Over 11 months, we evaluated empiric antibiotics prospectively in two ICUs of a large tertiary university teaching hospital. A pneumonia committee (PC) reviewed all patients and defined pneumonia according to the guidelines of the U.S. Centers for Disease Control and Prevention (CDC). The CPIS was calculated for all patients at day one and day three of antibiotic therapy. The percentage of patients with a CPIS<or=6 was compared for the ICU and PC, and the total antibiotic days potentially saved by using CPIS<or=6 as the criterion for treatment were determined. Receiver operating characteristic (ROC) curves and inter-observer reliability were determined.

RESULTS

Three hundred twelve patients received empiric antibiotics, 83 of whom were believed to have pneumonia by the ICU staff (2,283 antibiotic days). On day one, the 55 patients started on antibiotics had a CPIS<or=6, with 1,460 antibiotic-days, and only 28 patients had a CPIS>6 (823 antibiotic-days). In contrast, the PC determined 19 patients (23%) to have pneumonia by the CDC definition (731 antibiotic-days), with eight of these patients having a CPIS<or=6 and 11 a CPIS>6. Pneumonia committee review resulted in fewer patients believed to have pneumonia and a greater percentage with a CPIS>6 (odds ratio [OR] 2.7; 95% confidence interval [CI] 0.86, 8.6; p=0.05). Restriction of antibiotics to patients with a CPIS>6 would have saved 1,460 antibiotic-days at day one and 1,053 days if treatment was delayed until day three. Clinical Pulmonary Infection Score ROC curves for the PC showed an area under the curve (AUC) of 0.82 (95% CI 0.72, 0.91), whereas the AUC for the ICU group was 0.85 (95% CI 0.79, 0.92). The sensitivity and specificity of a CPIS>6 for the PC were 79% and 75%, respectively, with correct prediction 76% of the time. The inter-observer reliability of the CPIS had a kappa value of 0.88.

CONCLUSIONS

This prospective evaluation confirms that 50% of antibiotic-days in our ICU are used empirically for pneumonia when that infection is not likely to be present by either CDC or CPIS criteria. Although the CPIS has good reliability and acceptable sensitivity and specificity, PC review and CPIS<or=6 were commonly divergent (42-47%). Thus, better strategies should be developed for identification of pneumonia and empiric antibiotic administration in the ICU.

Ventilator associated pneumonia

Hospital acquired or nosocomial infections continue to be an important cause of morbidity and mortality. The critically ill patient is at particular risk of developing intensive care unit acquired infection, with the lungs being especially vulnerable. Nosocomial bacterial pneumonia occurring after two days of mechanical ventilation is referred to as ventilator associated pneumonia, and is the most common nosocomial infection seen in the intensive care unit. Intubation of the trachea and mechanical ventilation is associated with a 7-fold to 21-fold increase in the incidence of pneumonia and up to 28% of patients receiving mechanical ventilation will develop this complication. Its development is associated with an attributable increase in morbidity and mortality. The establishment of an accurate diagnosis of ventilator associated pneumonia remains problematic and as yet there is still no accepted "gold standard" for diagnosis. The responsible pathogens vary according to case mix, local resistance patterns, and methodology of sampling. However, there is general agreement that rapid initiation of appropriate antimicrobial therapy improves outcome.

Update in ventilator-associated pneumonia

PURPOSE OF REVIEW

Ventilator-associated pneumonia remains an important topic (or subject) in the care of the critically ill. Issues related to ventilator-associated pneumonia are now particularly acute given the continued increase in rates of antimicrobial resistance seen in intensive care units. This review examines the latest literature in this area, including promising approaches to infection prevention and recently developed guidelines to aid clinicians in limiting, identifying and treating ventilator-associated pneumonia.

RECENT FINDINGS

Increasingly rigorous and robust studies have shown the enormous cost, morbidity and mortality of infections acquired in the intensive care unit in general and of ventilator-associated pneumonia in particular, and offered potential management options. Specific areas of promise include advances in means of diagnosis, such as appropriate use of bronchoscopy and inflammatory markers, and treatment methods, including short-course treatment regimens and the use of 'de-escalation' as a strategy for antibiotic prescribing.

SUMMARY

Recent studies have started to illuminate the full magnitude of the impact of ventilator-associated pneumonia in the intensive care unit and suggest potential measures for intervention. Hopefully, additional work will aid in eventual development of effective preventive, diagnostic and therapeutic strategies that can reliably improve patient outcomes.

Diagnosis and Treatment of Ventilator-Associated Pneumonia

Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in the ICU. Patients who acquire VAP have higher mortality rates and longer ICU and hospital stays. Because there are other potential causes of fever, leukocytosis, and pulmonary infiltrates, clinical diagnostic criteria are overly sensitive in the diagnosis of VAP. Employing quantitative cultures of bronchopulmonary secretions in the diagnostic algorithm leads to less antibiotic use and probably to lower mortality. With respect to microbiologic diagnosis, it is not clear that the use of a particular sampling method (bronchoscopic or nonbronchoscopic), when quantitatively cultured, is associated with better outcomes. Delayed administration of adequate antibiotic therapy is linked to an increased mortality rate. Hence, the focus of initial antibiotic therapy should be to rapidly provide antibiotic coverage for all likely pathogens and to then narrow or focus the antibiotic spectrum based on the results of quantitative cultures. Eight days of antibiotic therapy appears equivalent to 15 days of therapy except when treating nonlactose-fermenting Gram-negative organisms. In this latter situation, longer treatment durations appear to reduce the risk of recrudescence after discontinuation of antibiotic therapy. A guideline-based approach using the local hospital or ICU antibiogram can increase the likelihood that adequate initial antibiotic therapy is used and reduce the overall use of antibiotics and the associated selection pressure for multidrug-resistant organisms.

Hospital-acquired pneumonia in the 21st century: a review of existing treatment options and their impact on patient care

Hospital-acquired pneumonia is a common nosocomial infection, with significant morbidity and mortality, and represents a major therapeutic challenge to clinicians. The therapeutic approach must be patient-oriented and institution-specific. The specific risk factors of each patient, such as previous antibiotic exposure, underlying diseases, length of hospital stay and the local patterns of antimicrobial resistance, should guide physicians in their decision of the initial optimal empirical therapy. Delays in the initiation or inappropriate/inadequate initial therapy are related to increased mortality and worse outcomes. In responding patients, as soon as culture data are available, efforts should be made to change the initial broad spectrum antibiotic regimen to a more targeted one (de-escalation). The optimal duration of treatment is a matter of debate, but courses longer than 1 week are rarely justified.

Gram-negative bacterial pneumonia: aetiology and management

PURPOSE OF REVIEW

Recent articles of clinical and investigational interest on Gram-negative pneumonia, particularly hospital-acquired and ventilator-associated pneumonia, are reviewed.

RECENT FINDINGS

The high rate of respiratory infections due to Gram-negative bacteria in late-onset ventilator-associated pneumonia has been repeatedly documented. The predominant pathogens are Pseudomonas aeruginosa and Acinetobacter baumannii. On the other hand, the frequency of Gram-negative bacteria in community-acquired pneumonia and in early-onset ventilator-associated pneumonia is increasing. Patients with risk factors for infection with resistant pathogens should initially receive a combination therapy that covers a broad spectrum, and, as soon as the pathogen and the susceptibilities are available, treatment should be simplified to a more targeted one (with the possible exception of P. aeruginosa pneumonia). Adequate dosing is of great importance and the use of pharmacodynamic/pharmacokinetic principles when prescribing antibiotics increases effectiveness. The optimal duration of therapy remains unknown; several studies have supported the use of shorter courses of treatment. Alternative treatment approaches (e.g. vaccines) are under investigation.

SUMMARY

The increasing frequency of resistant Gram-negative bacteria and the shortage of newer antibiotics in the pipeline with activity against Gram-negative bacteria is of concern. Early effective antimicrobial treatment is a key for the resolution of infection and improved survival.

Comparison of piperacillin/tazobactam and imipenem/cilastatin, both in combination with tobramycin, administered every 6 h for treatment of nosocomial pneumonia

This randomized, double-blind, multicenter study compared the efficacy and safety of piperacillin/tazobactam (P/T) and imipenem/cilastatin (IMP), both in combination with an aminoglycoside, in hospitalized patients with acute nosocomial pneumonia (NP). Patients with acute NP, defined as pneumonia with symptoms > or = 48 h after admission or < or =7 days after hospital discharge, received infusions of 4 g/500 mg P/T or 500 mg/500 mg IMP every 6 h. Endpoints were clinical cure and microbiological response rates; pathogen eradication rates; length of hospital stay; hospital readmissions; and adverse events (AEs). Of 437 patients in the intent-to-treat population, 197 were efficacy evaluable. At test-of-cure, response rates were similar between groups. Within the efficacy evaluable population, 68% of P/T patients and 61% of IMP patients were clinically cured (P = 0.256). Microbiological responses for P/T and IMP patients were: eradication, 64% versus 59%; persistence, 29% versus 21%; relapse, 0% versus 5%; and superinfection, 7% versus 15%, respectively. Gram-positive isolates were eradicated in 83% of P/T patients and 75% of IMP patients; Gram-negative pathogens were eradicated in 72% of P/T patients and 77% of IMP patients. Treatment groups had similar number of mean hospital days, readmission rates, and frequency of AEs. This study showed that P/T administered four times per day was as safe and efficacious as IMP in treating hospitalized patients with NP.

Pharmacodynamics of antimicrobials for the empirical treatment of nosocomial pneumonia: A report from the OPTAMA Program

OBJECTIVE

To compare the probability of achieving specific pharmacodynamic exposures of commonly used intravenous antibiotics for the empirical treatment of nosocomial pneumonia against those pathogens most commonly implicated in the disease.

DESIGN

Ten thousand-subject Monte Carlo simulation.

SETTING

Research center.

SUBJECT

None.

INTERVENTIONS

Pharmacodynamic analysis was conducted for the following antimicrobials at standard doses: meropenem, imipenem-cilastatin, ceftazidime, cefepime, piperacillin/tazobactam, and ciprofloxacin. Prevalence of causative pathogens was based on the 2000 SENTRY Antimicrobial Surveillance Study, and minimum inhibitory concentration (MIC) values were obtained using the 2003 US MYSTIC database. The probabilities of each drug and dosing regimen in achieving pharmacodynamic targets were calculated. Bactericidal targets were defined as 40% T>MIC for the carbapenems, 50% T>MIC for other beta-lactams, and an area under the curve (AUC)/MIC ratio of 125 for ciprofloxacin. A sensitivity analysis was performed using two alternate models to determine the impact of varying pathogen prevalence on target attainment.

MEASUREMENTS AND MAIN RESULTS

Meropenem and imipenem provided high probabilities of achieving their bactericidal target of 40% T>MIC, with target attainments of 98% for all regimens. At the bactericidal end point of 50% T>MIC, cefepime 2 g every 8 hrs displayed the highest target attainment at 99.9%, followed by cefepime 2 g every 12 hrs, ceftazidime 2 g every 8 hrs, piperacillin/tazobactam 4.5 g every 6 hrs and 3.375 g every 6 hrs, cefepime 1 g every 12 hrs, and ceftazidime 1 g every 8 hrs with target attainments of 95.0%, 92.5%, 92.3%, 91.3%, 90.3%, and 67.9%, respectively. Ciprofloxacin presented the lowest probability of achieving its bactericidal target of an AUC/MIC ratio of 125, with target attainments of 54.7% and 12.0% when given as 400 mg every 8 hrs and 400 mg every 12 hrs, respectively.

CONCLUSIONS

Meropenem, imipenem, cefepime, ceftazidime (2 g every 8 hrs), and piperacillin/tazobactam have high probabilities of achieving adequate pharmacodynamic exposures when given for the empirical treatment of nosocomial pneumonia in the absence of methicillin-resistant S. aureus. Ceftazidime 1g every 8 hrs and ciprofloxacin produce low target attainment rates and will not likely result in high clinical success rates when given as monotherapy.

Ventilator-associated pneumonia

PURPOSE OF REVIEW

This review summarises some of the notable papers on ventilator-associated pneumonia (VAP) from January 2003 to October 2004.

RECENT FINDINGS

Ventilator-associated pneumonia remains an important drain on hospital resources. All population groups are affected, but patients with VAP are more likely to be older, sicker, and male, with invasive medical devices in situ. Early VAP diagnosis is desirable to reduce VAP mortality and to retard emergence of multidrug-resistant microbes. This may be possible using preliminary culture results or intracellular organism in polymorphonuclear cells. In most intensive care units, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii are the commonest organisms isolated in VAP. However, causative organisms vary between and within hospitals. Consequently, individual intensive care units should develop empirical antibiotic policies to target the pathogenic bacteria prevalent in their patient populations. Preventative strategies aimed at reducing aerodigestive tract colonisation by pathogenic organisms, and also their subsequent aspiration, are becoming increasingly important. Educating medical staff about these simple measures is therefore pertinent. To reduce the occurrence of multidrug-resistant organisms, limiting the duration of antibiotic treatment to 8 days and antimicrobial rotation should be contemplated. Empirical therapy with antipseudomonal penicillins plus beta-lactamase inhibitors should be considered. If methicillin-resistant Staphylococcus aureus VAP is a possibility, linezolid may be better than vancomycin.

SUMMARY

Prevention remains the key to reducing VAP prevalence.

Nosocomial lung infections in adult intensive care units

Nosocomial respiratory tract infections are the leading type of nosocomial infections. Despite the development of new antibiotic therapies, they are associated with an increased morbidity and mortality. Patients with comorbidities are especially predisposed to acquire these infections, as are patients exposed to respiratory therapy. Aspiration of colonized secretions from the oropharynx is the main mechanism of infection development. Barrier techniques to reduce aspiration and antimicrobial agents to alter bacterial flora are important in preventing pneumonia episodes. The initial institution of an adequate antibiotic regimen is a determinant of outcome. Nosocomial pneumonias are often difficult to treat due to antibiotic-resistant bacteria. Antibiotic policies are crucial in avoiding a progression in antibiotic resistance.

Hospital-acquired pneumonia

PURPOSE OF REVIEW

The aim of this review is to summarize recent developments regarding risks factors, clinical features, management and antimicrobial resistance, and prevention of hospital-acquired pneumonia.

RECENT FINDINGS

Risk factors for hospital-acquired pneumonia developing in specific ICUs (neurologic and cardiovascular surgery) were reported. Characteristics of pneumonia acquired in general wards but requiring ICU admission were studied. Analysis of the impact of reintubation on pneumonia occurrence demonstrated that only reintubation after accidental extubation increases the risk. Early administration of adequate antibiotic(s), associated with a deescalating strategy, remains the only measure directly amenable to modification by clinicians that decreases the infection-related mortality. Numerous data emphasized the recommendation that guidelines for hospital-acquired pneumonia therapy should be updated and customized to local patterns to improve the level of adequacy of antimicrobial treatment. A 8-day treatment regimen could be proposed when pneumonia is not caused by a nonfermenting, gram-negative bacilli. In cases of pneumonia caused by methicillin-resistant Staphylococcus aureus, linezolid, compared with vancomycin, significantly increases the rates of cure and survival. Semirecumbent positioning in all eligible patients, sucralfate rather than H2 antagonists in patients at low to moderate risk of gastrointestinal bleeding, and, in selected patients, aspiration of subglottic secretions and oscillating beds are the measures proposed to prevent the development of ventilator-associated pneumonia. Conversely, the routine or indiscriminate use of selective digestive decontamination is not recommended.

SUMMARY

In our opinion, the optimization of the length of treatment and the reduction of mortality with linezolid in staphylococcal pneumonia are two major recent developments.

Decision analysis of antibiotic and diagnostic strategies in ventilator-associated pneumonia

The optimal strategy for ventilator-associated pneumonia remains controversial. To clarify the tradeoffs involved, we performed a decision analysis. Strategies evaluated included antibiotic therapy with and without diagnostic testing. Tests that were explored included endotracheal aspirates, bronchoscopy with protected brush or bronchoalveolar lavage, and nonbronchoscopic mini-bronchoalveolar lavage (mini-BAL). Outcomes included dollar cost, antibiotic use, survival, cost-effectiveness, antibiotic use per survivor, and the outcome perspective of financial cost-antibiotic use per survivor. Initial coverage with three antibiotics was better than expectant management or one or two antibiotic approaches, leading to both improved survival (54% vs. 66%) and decreased cost (US dollars 55447 vs. US dollars 41483 per survivor). Testing with mini-BAL did not improve survival but did decrease costs (US dollars 41483 vs. US dollars 39967) and antibiotic use (63 vs. 39 antibiotic days per survivor). From the perspective of minimizing cost, minimizing antibiotic use, and maximizing survival, the best strategy was three antibiotics with mini-BAL.

Understanding resistance to beta-lactams and beta-lactamase inhibitors in the SHV beta-lactamase: lessons from the mutagenesis of SER-130

Bacterial resistance to beta-lactam/beta-lactamase inhibitor combinations by single amino acid mutations in class A beta-lactamases threatens our most potent clinical antibiotics. In TEM-1 and SHV-1, the common class A beta-lactamases, alterations at Ser-130 confer resistance to inactivation by the beta-lactamase inhibitors, clavulanic acid, and tazobactam. By using site-saturation mutagenesis, we sought to determine the amino acid substitutions at Ser-130 in SHV-1 beta-lactamase that result in resistance to these inhibitors. Antibiotic susceptibility testing revealed that ampicillin and ampicillin/clavulanic acid resistance was observed only for the S130G beta-lactamase expressed in Escherichia coli. Kinetic analysis of the S130G beta-lactamase demonstrated a significant elevation in apparent Km and a reduction in kcat/Km for ampicillin. Marked increases in the dissociation constant for the preacylation complex, KI, of clavulanic acid (SHV-1, 0.14 microm; S130G, 46.5 microm) and tazobactam (SHV-1, 0.07 microm; S130G, 4.2 microm) were observed. In contrast, the k(inact)s of S130G and SHV-1 differed by only 17% for clavulanic acid and 40% for tazobactam. Progressive inactivation studies showed that the inhibitor to enzyme ratios required to inactivate SHV-1 and S130G were similar. Our observations demonstrate that enzymatic activity is preserved despite amino acid substitutions that significantly alter the apparent affinity of the active site for beta-lactams and beta-lactamase inhibitors. These results underscore the mechanistic versatility of class A beta-lactamases and have implications for the design of novel beta-lactamase inhibitors.