Combination antibiotic therapy for Pseudomonas aeruginosa bacteraemia

Impact of adequate empirical combination therapy on mortality in septic shock due to Pseudomonas aeruginosa bloodstream infections: a multicentre retrospective cohort study

OBJECTIVES

To determine the association of adequate empirical combination therapy (AECT) with 30-day all-cause mortality in patients with septic shock due to Pseudomonas aeruginosa bloodstream infections (BSI).

METHODS

This multicentre, retrospective cohort study analysed data from 14 public hospitals in Italy, including all consecutive adult patients admitted during 2021-2022 with septic shock due to P. aeruginosa BSI. We compared the outcomes of patients receiving AECT to those on adequate empirical monotherapy (AEMT) using Cox regression analyses.

RESULTS

Of the 98 patients who received adequate empirical antibiotic treatment for septic shock due to P. aeruginosa BSI, 24 underwent AECT and 74 were given AEMT. AECT was associated with a lower 30-day all-cause mortality (25%, six out of 24) compared to AEMT (56.8%, 42 out of 74; P = 0.007). Multivariate Cox regression analysis indicated AECT as the only factor significantly associated with improved survival (aHR 0.30; 95% CI 0.12-0.71; P = 0.006). By contrast, the use of monotherapy or combination therapy in the definitive regimen did not influence mortality (aHR 0.73; 95% CI 0.25-2.14; P = 0.568).

CONCLUSIONS

AECT may be associated with reduced mortality compared to monotherapy in septic shock patients due to P. aeruginosa BSI. However, the administration of definitive adequate monotherapy or combination therapy yields similar outcomes, suggesting that once susceptibility is documented, switching to a single active in vitro drug is safe and feasible. Further studies are recommended to validate these findings.

Resistance in Pseudomonas aeruginosa: A Narrative Review of Antibiogram Interpretation and Emerging Treatments

Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium renowned for its resilience and adaptability across diverse environments, including clinical settings, where it emerges as a formidable pathogen. Notorious for causing nosocomial infections, P. aeruginosa presents a significant challenge due to its intrinsic and acquired resistance mechanisms. This comprehensive review aims to delve into the intricate resistance mechanisms employed by P. aeruginosa and to discern how these mechanisms can be inferred by analyzing sensitivity patterns displayed in antibiograms, emphasizing the complexities encountered in clinical management. Traditional monotherapies are increasingly overshadowed by the emergence of multidrug-resistant strains, necessitating a paradigm shift towards innovative combination therapies and the exploration of novel antibiotics. The review accentuates the critical role of accurate antibiogram interpretation in guiding judicious antibiotic use, optimizing therapeutic outcomes, and mitigating the propagation of antibiotic resistance. Misinterpretations, it cautions, can inadvertently foster resistance, jeopardizing patient health and amplifying global antibiotic resistance challenges. This paper advocates for enhanced clinician proficiency in interpreting antibiograms, facilitating informed and strategic antibiotic deployment, thereby improving patient prognosis and contributing to global antibiotic stewardship efforts.

Influence of empirical double-active combination antimicrobial therapy compared with active monotherapy on mortality in patients with septic shock: a propensity score-adjusted and matched analysis

Objectives

To evaluate the influence on mortality of empirical double-active combination antimicrobial therapy (DACT) compared with active monotherapy (AM) in septic shock patients.

Methods

A retrospective study was performed of monomicrobial septic shock patients admitted to a university centre during 2010-15. A propensity score (PS) was calculated using a logistic regression model taking the assigned therapy as the dependent variable, and used as a covariate in multivariate analysis predicting 7, 15 and 30 day mortality and for matching patients who received DACT or AM. Multivariate models comprising the assigned therapy group and the PS were built for specific patient subgroups.

Results

Five-hundred and seventy-six patients with monomicrobial septic shock who received active empirical antimicrobial therapy were included. Of these, 340 received AM and 236 DACT. No difference in 7, 15 and 30 day all-cause mortality was found between groups either in the PS-adjusted multivariate logistic regression analysis or in the PS-matched cohorts. However, in patients with neutropenia, DACT was independently associated with a better outcome at 15 (OR 0.29, 95% CI 0.09-0.92) and 30 (OR 0.25, 95% CI 0.08-0.79) days, while in patients with Pseudomonas aeruginosa infection DACT was associated with lower 7 (OR 0.12, 95% CI 0.02-0.7) and 30 day (OR 0.26, 95% CI 0.08-0.92) mortality.

Conclusions

All-cause mortality at 7, 15 and 30 days was similar in patients with monomicrobial septic shock receiving empirical double-active combination therapy and active monotherapy. However, a beneficial influence of empirical double-active combination on mortality in patients with neutropenia and those with P. aeruginosa infection is worthy of further study.

Pseudomonas aeruginosa AmpR: an acute-chronic switch regulator

Pseudomonas aeruginosa is one of the most intractable human pathogens that pose serious clinical challenge due to extensive prevalence of multidrug-resistant clinical isolates. Armed with abundant virulence and antibiotic resistance mechanisms, it is a major etiologic agent in a number of acute and chronic infections. A complex and intricate network of regulators dictates the expression of pathogenicity factors in P. aeruginosa. Some proteins within the network play key roles and control multiple pathways. This review discusses the role of one such protein, AmpR, which was initially recognized for its role in antibiotic resistance by regulating AmpC β-lactamase. Recent genomic, proteomic and phenotypic analyses demonstrate that AmpR regulates expression of hundreds of genes that are involved in diverse pathways such as β-lactam and non-β-lactam resistance, quorum sensing and associated virulence phenotypes, protein phosphorylation, and physiological processes. Finally, ampR mutations in clinical isolates are reviewed to shed light on important residues required for its function in antibiotic resistance. The prevalence and evolutionary implications of AmpR in pathogenic and nonpathogenic proteobacteria are also discussed. A comprehensive understanding of proteins at nodal positions in the P. aeruginosa regulatory network is crucial in understanding, and ultimately targeting, the pathogenic stratagems of this organism.

Beta lactam antibiotic monotherapy versus beta lactam-aminoglycoside antibiotic combination therapy for sepsis

BACKGROUND

Optimal antibiotic treatment for sepsis is imperative. Combining a beta lactam antibiotic with an aminoglycoside antibiotic may provide certain advantages over beta lactam monotherapy.

OBJECTIVES

Our objectives were to compare beta lactam monotherapy versus beta lactam-aminoglycoside combination therapy in patients with sepsis and to estimate the rate of adverse effects with each treatment regimen, including the development of bacterial resistance to antibiotics.

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 11); MEDLINE (1966 to 4 November 2013); EMBASE (1980 to November 2013); LILACS (1982 to November 2013); and conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (1995 to 2013). We scanned citations of all identified studies and contacted all corresponding authors. In our previous review, we searched the databases to July 2004.

SELECTION CRITERIA

We included randomized and quasi-randomized trials comparing any beta lactam monotherapy versus any combination of a beta lactam with an aminoglycoside for sepsis.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause mortality. Secondary outcomes included treatment failure, superinfections and adverse events. Two review authors independently collected data. We pooled risk ratios (RRs) with 95% confidence intervals (CIs) using the fixed-effect model. We extracted outcomes by intention-to-treat analysis whenever possible.

MAIN RESULTS

We included 69 trials that randomly assigned 7863 participants. Twenty-two trials compared the same beta lactam in both study arms, while the remaining trials compared different beta lactams using a broader-spectrum beta lactam in the monotherapy arm. In trials comparing the same beta lactam, we observed no difference between study groups with regard to all-cause mortality (RR 0.97, 95% CI 0.73 to 1.30) and clinical failure (RR 1.11, 95% CI 0.95 to 1.29). In studies comparing different beta lactams, we observed a trend for benefit with monotherapy for all-cause mortality (RR 0.85, 95% CI 0.71 to 1.01) and a significant advantage for clinical failure (RR 0.75, 95% CI 0.67 to 0.84). No significant disparities emerged from subgroup and sensitivity analyses, including assessment of participants with Gram-negative infection. The subgroup of Pseudomonas aeruginosa infections was underpowered to examine effects. Results for mortality were classified as low quality of evidence mainly as the result of imprecision. Results for failure were classified as very low quality of evidence because of indirectness of the outcome and possible detection bias in non-blinded trials. We detected no differences in the rate of development of resistance. Nephrotoxicity was significantly less frequent with monotherapy (RR 0.30, 95% CI 0.23 to 0.39). We found no heterogeneity for all these comparisons.We included a small subset of studies addressing participants with Gram-positive infection, mainly endocarditis. We identified no difference between monotherapy and combination therapy in these studies.

AUTHORS' CONCLUSIONS

The addition of an aminoglycoside to beta lactams for sepsis should be discouraged. All-cause mortality rates are unchanged. Combination treatment carries a significant risk of nephrotoxicity.

Less is more: combination antibiotic therapy for the treatment of gram-negative bacteremia in pediatric patients

IMPORTANCE

Definitive combination antibiotic therapy with a β-lactam and an aminoglycoside for the treatment of gram-negative bacteremia is commonly prescribed in pediatric patients; however, its efficacy and toxicity relative to β-lactam monotherapy are unknown.

OBJECTIVE

To determine whether definitive combination antibiotic therapy affects mortality and nephrotoxicity in pediatric patients with gram-negative bacteremia.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study including pediatric patients (aged ≤18 years) with gram-negative bacteremia hospitalized at the Johns Hopkins Children's Center between 2002 and 2011.

MAIN OUTCOMES AND MEASURES

Outcomes included 30-day mortality and nephrotoxicity classified according to the pediatric RIFLE (risk for renal dysfunction, injury to the kidney, failure of kidney function, loss of kidney function, and end-stage renal disease) criteria. To account for nonrandom assignment of combination therapy, propensity score weighting was combined with multivariable logistic regression to estimate the effect of combination therapy on mortality and nephrotoxicity.

RESULTS

Of the 879 eligible pediatric patients with bacteremia, 537 (61.1%) received combination therapy. After propensity score adjustment, baseline demographic and clinical characteristics between the groups were well balanced. There was no association between combination therapy and 30-day mortality (odds ratio, 0.98; 95% CI, 0.93-1.02; P = .27). There were 170 patients (19.3%) with evidence of acute kidney injury, including 135 (25.1%) and 35 (10.2%) in the combination therapy and monotherapy arms, respectively. Patients receiving combination therapy had approximately twice the odds of nephrotoxicity compared with those receiving monotherapy (odds ratio, 2.15; 95% CI, 2.09-2.21).

CONCLUSIONS AND RELEVANCE

The use of β-lactam monotherapy for gram-negative bacteremia in pediatric patients reduces subsequent nephrotoxicity without compromising survival.

Effect of adequate single-drug vs combination antimicrobial therapy on mortality in Pseudomonas aeruginosa bloodstream infections: a post Hoc analysis of a prospective cohort

BACKGROUND

Empirical combination therapy is recommended for patients with known or suspected Pseudomonas aeruginosa (PA) infection as a means to decrease the likelihood of administering inadequate antimicrobial treatment, to prevent the emergence of resistance, and to achieve a possible additive or even synergistic effect.

METHODS

We performed a post hoc analysis of patients with PA bloodstream infections from a published prospective cohort. Mortality was compared in patients treated with adequate empirical and definitive combination therapy (AECT, ADCT), and adequate empirical and definitive single-drug therapy (AESD, ADSD). Confounding was controlled by Cox regression analysis, and a propensity score for receiving AECT or ADCT was also used.

RESULTS

The final cohort comprised 593 patients with a single episode of PA bacteremia. The 30-day mortality was 30% (176 patients); 76 patients (13%) died during the first 48 hours. The unadjusted probabilities of survival until day 30 were 69.4% (95% confidence interval [CI], 59.1-81.6) for the patients receiving AECT, 73.5% (95% CI, 68.4%-79.0%) for the AESD group, and 66.7% (95% CI, 61.2%-72.7%) for patients who received inadequate empirical therapy (P = .17, log-rank test). After adjustment for confounders, the AESD group (adjusted hazard ratio [AHR], 1.17; 95% CI, .70-1.96; P = .54) and patients who received ADSD (AHR, 1.34; 95% CI, .73-2.47; P = .35) showed no association with 30-day mortality compared with the AECT and ADCT groups, respectively.

CONCLUSIONS

These results suggests that treatment with combination antimicrobial therapy did not reduce the mortality risk compared with single-drug therapy in PA bloodstream infections.

Outcomes of appropriate empiric combination versus monotherapy for Pseudomonas aeruginosa bacteremia

Pseudomonas aeruginosa bacteremia is associated with high hospital mortality. Empirical combination therapy is commonly used to increase the likelihood of appropriate therapy, but the benefits of employing >1 active agent have yet to be established. The purpose of this study was to compare outcomes of patients receiving appropriate empirical combination versus monotherapy for P. aeruginosa bacteremia. This was a retrospective, multicenter, cohort study of hospitalized adult patients with P. aeruginosa bacteremia from 2002 to 2011. The primary endpoint (30-day mortality) was assessed using multivariate logistic regression, adjusting for underlying confounding variables. Secondary endpoints of hospital mortality and time to mortality were assessed by Fisher's exact test and the Cox proportional hazards model, respectively. A total of 384 patients were analyzed. Thirty-day mortality was higher for patients receiving inappropriate therapy than for those receiving appropriate empirical therapy (43.8% versus 21.5%; P = 0.03). However, there were no statistical differences in 30-day mortality following appropriate empirical combination versus monotherapy after adjusting for baseline APACHE II scores and lengths of hospital stay prior to the onset of bacteremia (P = 0.55). Observed hospital mortality was 36.6% for patients administered combination therapy, compared with 28.7% for monotherapy patients (P = 0.17). After adjusting for baseline APACHE II scores, the relationship between time to mortality and combination therapy was not statistically significant (P = 0.59). Overall, no significant differences were observed for 30-day mortality, hospital mortality, and time to mortality between combination and monotherapy for P. aeruginosa bacteremia. Empirical combination therapy did not appear to offer an additional benefit, as long as the isolate was susceptible to at least one antimicrobial agent.

A survey on infection management practices in Italian ICUs

Introduction

An online survey was conducted to characterize current infection management practices in Italian intensive care units (ICUs), including the antibacterial and antifungal drug regimens prescribed for various types of infections.

Methods

During February and March 2011, all 450 ICUs in public hospitals in Italy were invited to take part in an online survey. The questionnaire focused on ICU characteristics, methods used to prevent, diagnose, and treat infections, and antimicrobials prescribing policies. The frequency of each reported practice was calculated as a percentage of the total number of units answering the question. The overall response rate to the questionnaire was 38.8% (175 of the 450 ICUs contacted) with homogeneous distribution across the country and in terms of unit type.

Results

Eighty-eight percent of the responding facilities performed periodical surveillance cultures on all patients. In 71% of patients, cultures were also collected on admission. Endotracheal/bronchial aspirates were the most frequently cultured specimens at both time points. Two-thirds of the responding units had never performed screening cultures for methicillin-resistant Staphylococcus aureus. Around 67% of the ICUs reported the use of antimicrobial de-escalation strategies during the treatment phase. In general, the use of empirical antimicrobial drug regimens was appropriate. Although the rationale for the choice was not always clearly documented, the use of a combination therapy was preferred over antibiotic monotherapy. The preferred first-line agents for invasive candidiasis were fluconazole and an echinocandin (64% and 25%, respectively). Two-thirds of the ICUs monitored vancomycin serum levels and administered it by continuous infusion in 86% of cases. For certain antibiotics, reported doses were too low to ensure effective treatment of severe infections in critically ill patients; conversely, inappropriately high doses were administered for certain antifungal drugs.

Conclusions

Although infection control policies and management practices are generally appropriate in Italian ICUs, certain aspects, such as the extensive use of multidrug empirical regimens and the inappropriate antimicrobial dosing, deserve careful management and closer investigation.

Combination therapy for treatment of infections with gram-negative bacteria

Combination antibiotic therapy for invasive infections with Gram-negative bacteria is employed in many health care facilities, especially for certain subgroups of patients, including those with neutropenia, those with infections caused by Pseudomonas aeruginosa, those with ventilator-associated pneumonia, and the severely ill. An argument can be made for empiric combination therapy, as we are witnessing a rise in infections caused by multidrug-resistant Gram-negative organisms. The wisdom of continued combination therapy after an organism is isolated and antimicrobial susceptibility data are known, however, is more controversial. The available evidence suggests that the greatest benefit of combination antibiotic therapy stems from the increased likelihood of choosing an effective agent during empiric therapy, rather than exploitation of in vitro synergy or the prevention of resistance during definitive treatment. In this review, we summarize the available data comparing monotherapy versus combination antimicrobial therapy for the treatment of infections with Gram-negative bacteria.

Influence of multidrug resistance and appropriate empirical therapy on the 30-day mortality rate of Pseudomonas aeruginosa bacteremia

Infections due to multidrug-resistant (MDR) Pseudomonas aeruginosa are increasing. The aim of our study was to evaluate the influences of appropriate empirical antibiotic therapy and multidrug resistance on mortality in patients with bacteremia due to P. aeruginosa (PAB). Episodes of PAB were prospectively registered from 2000 to 2008. MDR was considered when the strain was resistant to ≥3 antipseudomonal antibiotics. Univariate and multivariate analyses were performed. A total of 709 episodes of PAB were studied. MDR PAB (n = 127 [17.9%]) was more frequently nosocomial and associated with longer hospitalization, bladder catheter use, steroid and antibiotic therapy, receipt of inappropriate empirical antibiotic therapy, and a higher mortality. Factors independently associated with mortality were age (odds ratio [OR], 1.02; 95% confidence interval [CI], 1.002 to 1.033), shock (OR, 6.6; 95% CI, 4 to 10.8), cirrhosis (OR, 3.3; 95% CI, 1.4 to 7.6), intermediate-risk sources (OR, 2.5; 95% CI, 1.4 to 4.3) or high-risk sources (OR, 7.3; 95% CI, 4.1 to 12.9), and inappropriate empirical therapy (OR, 2.1; 95% CI, 1.3 to 3.5). To analyze the interaction between empirical therapy and MDR, a variable combining both was introduced in the multivariate analysis. Inappropriate therapy was significantly associated with higher mortality regardless of the susceptibility pattern, and there was a trend toward higher mortality in patients receiving appropriate therapy for MDR than in those appropriately treated for non-MDR strains (OR, 2.2; 95% CI, 0.9 to 5.4). In 47.9% of MDR PAB episodes, appropriate therapy consisted of monotherapy with amikacin. In conclusion, MDR PAB is associated with a higher mortality than non-MDR PAB. This may be related to a higher rate of inappropriate empirical therapy and probably also to amikacin as frequently the only appropriate empirical therapy given to patients with MDR PAB.

Does the piperacillin minimum inhibitory concentration for Pseudomonas aeruginosa influence clinical outcomes of children with pseudomonal bacteremia?

BACKGROUND

The Clinical and Laboratory Standards Institute (CLSI) recently elected to adjust the previous piperacillin susceptibility breakpoint of ≤64 µg/mL against Pseudomonas aeruginosa to ≤16 µg/mL, based largely on pharmacokinetic-pharmacodynamic (PK-PD) modeling studies. Data on whether PK-PD modeling correlates with clinical outcomes in children are needed before resorting to broader classes of antibiotics to treat P. aeruginosa.

METHODS

We performed a retrospective cohort study of children with P. aeruginosa bacteremia between 2001 and 2010 who were prescribed piperacillin. Baseline characteristics and clinical outcomes of children with piperacillin minimum inhibitory concentrations (MICs) of ≤16 µg/mL and of 32-64 µg/mL were compared. The primary outcome was 30-day mortality.

RESULTS

There were 170 children with P. aeruginosa bacteremia receiving piperacillin therapy who met inclusion criteria. One hundred twenty-four (72%) children had piperacillin MICs of ≤16 µg/mL and 46 (28%) children had piperacillin MICs of 32-64 µg/mL. There was no significant difference in baseline characteristics between the 2 groups. Thirty-day mortality was 9% and 24% in children with a piperacillin MIC of ≤16 µg/mL and of 32-64 µg/mL, respectively. Using multivariable logistic regression, children with elevated MICs had increased odds of mortality compared with children with lower MICs (odds ratio, 3.21; 95% confidence interval, 1.26-8.16).

CONCLUSIONS

Our finding that elevated piperacillin MICs are associated with higher mortality in children supports the recent CLSI recommendation to lower the breakpoint of piperacillin against P. aeruginosa to ≤16 µg/mL. Alternate therapeutic choices should be considered when piperacillin MICs against P. aeruginosa are ≥32 µg/mL.

Impact of definitive therapy with beta-lactam monotherapy or combination with an aminoglycoside or a quinolone for Pseudomonas aeruginosa bacteremia

Background

Bacteremia by Pseudomonas aeruginosa represents one severe infection. It is not clear whether beta-lactam monotherapy leads to similar rates of treatment success compared to combinations of beta-lactams with aminoglycosides or quinolones.

Methods

Retrospective cohort study from 3 tertiary hospitals (2 in Greece and 1 in Italy). Pseudomonas aeruginosa isolates were susceptible to a beta-lactam and an aminoglycoside or a quinolone. Patients received appropriate therapy for at least 48 hours. Primary outcome of interest was treatment success in patients with definitive beta-lactam combination therapy compared to monotherapy. Secondary outcomes were treatment success keeping the same empirical and definitive regimen, mortality, and toxicity.

Results

Out of 92 bacteremias there were 54 evaluable episodes for the primary outcome (20 received monotherapy). Treatment success was higher with combination therapy (85%) compared to beta-lactam monotherapy (65%), however not statistically significantly [Odds ratio (OR) 3.1; 95% Confidence Interval (CI) 0.69–14.7, p = 0.1]. Very long (>2 months) hospitalisation before bacteremia was the only factor independently associated with treatment success (OR 0.73; 95% CI 0.01–0.95, p = 0.046), however this result entailed few episodes. All-cause mortality did not differ significantly between combination therapy [6/31 (19%)] and monotherapy [8/19 (42%)], p = 0.11. Only Charlson comorbidity index was associated with excess mortality (p = 0.03).

Conclusion

Our study, in accordance with previous ones, indicates that the choice between monotherapy and combination therapy may not affect treatment success significantly. However, our study does not have statistical power to identify small or moderate differences. A large randomized controlled trial evaluating this issue is justified.

Pneumonia due to Pseudomonas aeruginosa: part II: antimicrobial resistance, pharmacodynamic concepts, and antibiotic therapy

Pseudomonas aeruginosa carries a notably higher mortality rate than other pneumonia pathogens. Because of its multiple mechanisms of antibiotic resistance, therapy has always been challenging. This problem has been magnified in recent years with the emergence of multidrug-resistant (MDR) pathogens often unharmed by almost all classes of antimicrobials. The objective of this article is to assess optimal antimicrobial therapy based on in vitro activity, animal studies, and pharmacokinetic/pharmacodynamic (PK/PD) observations so that evidence-based recommendations can be developed to maximize favorable clinical outcomes. Mechanisms of antimicrobial resistance of P aeruginosa are reviewed. A selective literature review of laboratory studies, PK/PD concepts, and controlled clinical trials of antibiotic therapy directed at P aeruginosa pneumonia was performed. P aeruginosa possesses multiple mechanisms for inducing antibiotic resistance to antimicrobial agents. Continuous infusion of antipseudomonal β-lactam antibiotics enhances bacterial killing. Although the advantages of combination therapy remain contentious, in vitro and animal model studies plus selected meta-analyses of clinical trials support its use, especially in the era of MDR. Colistin use and the role of antibiotic aerosolization are reviewed. An evidence-based algorithmic approach based on severity of illness, Clinical Pulmonary Infection Score, and combination antibiotic therapy is presented; clinical outcomes may be improved, and the emergence of MDR pathogens should be minimized with this approach.

Early combination antibiotic therapy yields improved survival compared with monotherapy in septic shock: a propensity-matched analysis

BACKGROUND

Septic shock represents the major cause of infection-associated mortality in the intensive care unit. The possibility that combination antibiotic therapy of bacterial septic shock improves outcome is controversial. Current guidelines do not recommend combination therapy except for the express purpose of broadening coverage when resistant pathogens are a concern.

OBJECTIVE

To evaluate the therapeutic benefit of early combination therapy comprising at least two antibiotics of different mechanisms with in vitro activity for the isolated pathogen in patients with bacterial septic shock.

DESIGN

Retrospective, propensity matched, multicenter, cohort study.

SETTING

Intensive care units of 28 academic and community hospitals in three countries between 1996 and 2007.

SUBJECTS

A total of 4662 eligible cases of culture-positive, bacterial septic shock treated with combination or monotherapy from which 1223 propensity-matched pairs were generated.

MEASUREMENTS AND MAIN RESULTS

The primary outcome of study was 28-day mortality. Using a Cox proportional hazards model, combination therapy was associated with decreased 28-day mortality (444 of 1223 [36.3%] vs. 355 of 1223 [29.0%]; hazard ratio, 0.77; 95% confidence interval, 0.67-0.88; p = .0002). The beneficial impact of combination therapy applied to both Gram-positive and Gram-negative infections but was restricted to patients treated with beta-lactams in combination with aminoglycosides, fluoroquinolones, or macrolides/clindamycin. Combination therapy was also associated with significant reductions in intensive care unit (437 of 1223 [35.7%] vs. 352 of 1223 [28.8%]; odds ratio, 0.75; 95% confidence interval, 0.63-0.92; p = .0006) and hospital mortality (584 of 1223 [47.8%] vs. 457 of 1223 [37.4%]; odds ratio, 0.69; 95% confidence interval, 0.59-0.81; p < .0001). The use of combination therapy was associated with increased ventilator (median and [interquartile range], 10 [0-25] vs. 17 [0-26]; p = .008) and pressor/inotrope-free days (median and [interquartile range], 23 [0-28] vs. 25 [0-28]; p = .007) up to 30 days.

CONCLUSION

Early combination antibiotic therapy is associated with decreased mortality in septic shock. Prospective randomized trials are needed.

Influence of empiric therapy with a beta-lactam alone or combined with an aminoglycoside on prognosis of bacteremia due to gram-negative microorganisms

Evidence supporting the combination of aminoglycosides with beta-lactams for gram-negative bacteremia is inconclusive. We have explored the influence on survival of empirical therapy with a beta-lactam alone versus that with a beta-lactam-aminoglycoside combination by retrospectively analyzing a series of bacteremic episodes due to aerobic or facultative gram-negative microorganisms treated with single or combination therapy. The outcome variable was a 30-day mortality. Prognostic factors were selected by regression logistic analysis. A total of 4,863 episodes were assessed, of which 678 (14%) received combination therapy and 467 (10%) were fatal. Factors independently associated with mortality included age greater than 65 (odds ratio [OR], 2; 95% confidence interval [CI], 1.6 to 2.6), hospital acquisition (OR, 1.5; 95% CI, 1.2 to 1.9), a rapidly or ultimately fatal underlying disease (OR, 2.5; 95% CI, 2 to 3.2), cirrhosis (OR, 1.9; 95% CI, 1.4 to 2.6), prior corticosteroids (OR, 1.5; 95% CI, 1.1 to 2), shock on presentation (OR, 8.8; 95% CI, 7 to 11), pneumonia (OR, 2.8; 95% CI, 1.9 to 4), and inappropriate empirical therapy (OR, 1.8; 95% CI, 1.3 to 2.5). Subgroup analysis revealed that combination therapy was an independent protective factor in episodes presenting shock (OR, 0.6; 95% CI, 0.4 to 0.9) or neutropenia (OR, 0.5; 95% CI, 0.3 to 0.9). Combination therapy improved the appropriateness of empirical therapy in episodes due to extended-spectrum beta-lactamase (ESBL)- or AmpC-producing Enterobacteriaceae and Pseudomonas aeruginosa. In patients with gram-negative bacteremia, we could not find an overall association between empirical beta-lactam-aminoglycoside combination therapy and prognosis. However, a survival advantage cannot be discarded for episodes presenting shock or neutropenia, hence in these situations the use of combination therapy may still be justified. Combination therapy also should be considered for patients at risk of being infected with resistant organisms, if only to increase the appropriateness of empirical therapy.

Aminoglycoside drugs in clinical practice: an evidence-based approach

Resistant bacteria have renewed our interest in the aminoglycoside drugs. Evidence on the efficiency of aminoglycosides in their different clinical uses is available from numerous randomized controlled trials and has been accrued and examined in recent systematic reviews and meta-analyses. Their results show that aminoglycosides should not be added to broad-spectrum beta-lactams to achieve synergism in treating Gram-negative infections as combination does not improve efficacy and adds side effects. The evidence from randomized trials in humans does not support the use of aminoglycosides in staphylococcal or streptococcal endocarditis, and is lacking for endocarditis caused by enterococci. Aminoglycosides are efficacious and safe as single drugs for the treatment of pyelonephritis and sepsis of a urinary source, but their efficacy might be lower than that of beta-lactams in Gram-negative infections of other sources. In patients with no risk factors, aminoglycosides are as safe as beta-lactams regarding side effects. They probably induce less resistance. Pragmatic large trials are needed to answer open clinical questions on the use of aminoglycosides.

Vascular catheter-associated infections: a microbiological and therapeutic update

The increasing incidence of central venous catheter (CVC)-related infections can be ascribed to the wider indications to central venous catheterization, to the higher attention to this issue paid by clinicians and microbiologists, and to the patient population referred to hospitals, increasingly characterized by different degrees of immunosuppression and often in critical clinical conditions. This phenomenon implies a higher health care burden and higher related costs, as well as a significant attributable mortality, that varies however according to the pathogen involved. The microorganisms most frequently involved in CVC-related infections are coagulase-negative staphylococci, Staphylococcus aureus, aerobic Gram-negative bacilli, and Candida albicans. In the management of suspected or proven central venous catheter-related infections, several issues need to be addressed: the need to remove the device or the possibility of salvage, the immediate start of calculated antibiotic therapy or the possibility of waiting for results of microbiological diagnostics and proceeding to etiologically-guided therapy. The preferred conservative method is the "Antibiotic-Lock technique" (ALT), based on the endoluminal application of antibacterials at extremely high concentrations in situ for a period of time long enough to ensure bactericidal activity. On the other hand, immediate catheter removal and initiation of appropriate calculated therapy immediately after an adequate diagnostic work-up are strongly recommended in a clinical setting of severe sepsis or septic shock.

[Pseudomonas aeruginosa: combined treatment vs. monotherapy]

Pseudomonas aeruginosa is a pathogen commonly encountered in clinical practice in critically ill patients. It is a serious cause of infection, associated with a high rate of morbidity and mortality. Inappropriate antimicrobial therapy and delay in starting effective antimicrobial therapy is associated with worse prognostic. This microorganism is clinically indistinguishable from others forms of gram-negative bacterial infection. The rate of multidrug-resistant P. aeruginosa has increased in the last years. For these reasons, patients with Pseudomonas infection might receive empirical antibiotics that are inactive against Pseudomonas, especially before antibiotic susceptibility results become available. It remains controversial whether combination therapy, given empirically or as definitive treatment, for suspected Pseudomonas aeruginosa infections is justifiable. In the present article, we aimed to review recent studies that have evaluated the impact of combination therapy on Pseudomonas infections outcome and we exhibit our point of view in this subject. It seems justifiable to start combination therapy with two antipseudomonal agents in patients with risk for Pseudomonas infection during the first 3-5 days, until having microbiological results. This combination therapy must be changed to monotherapy on the basis on the specific susceptibility pattern of the initial isolate. In cases without microbiological diagnosis and poor outcome, combination therapy will be maintained and other causes of infection will be studied. Multicentre prospective randomized trials in critically ill patients are needed to determine which antimicrobials combinations improve outcome in Pseudomonas infections.

Healthcare Epidemiology: Does Antibiotic Selection Impact Patient Outcome?

Inadequate antibiotic therapy, generally defined as microbiologically ineffective anti-infective therapy against the causative pathogen, can influence patient outcome. However, the detrimental effects of inadequate antibiotic therapy seem to become weaker in the most severely ill patients with short life expectancies. In addition to severity of illness, other methodological issues should be carefully examined in studies assessing the excess mortality due to inadequate therapy. To adjust for confounding as much as possible in order to obtain an unbiased estimate of the magnitude of the effect of inadequate therapy is a key methodological challenge for future research. With regard to the choice of antibiotic agents, beta-lactam and aminoglycoside combination therapy does not seem to improve clinical outcome in most cases of sepsis caused by gram-negative bacteria, including Pseudomonas aeruginosa bacteremia. A potential benefit of combination therapy in the treatment of severe pneumococcal sepsis has been suggested in several observational studies, but recently published data have disputed this hypothesis. Finally, better risk scores and laboratory tools are urgently needed to improve the adequacy of empirical antibiotic therapy and patient outcomes.

Antibiothérapie des états infectieux graves

Severe sepsis, which is related to a high mortality rate, requires a very specific antibiotic strategy, which must be adapted to each case. The appropriateness of empiric therapy is based on the delay before administration of the molecule, the bacterial resistance profile, and the kinetic and/or dynamic properties of the available antibiotics.

Stratégie antibiotique au cours du choc septique

Septic shock remains a true challenge to modern therapeutics. The quality and earliness of antibiotic administration are both fundamental elements. Treatment should be individually adapted to each patient. The pharmacokinetic indicators and predicted resistance of the bacteria targeted determine the choice of treatment, often empirical. Radical treatment of the source of infection, especially by surgery, should be combined with antibiotic treatment whenever possible.

Microbiological rationale for the utilisation of prulifloxacin, a new fluoroquinolone, in the eradication of serious infections caused by Pseudomonas aeruginosa

Minimal inhibitory concentrations (MICs) of prulifloxacin were evaluated in comparison with ciprofloxacin, levofloxacin and moxifloxacin against a large collection (N = 300) of Pseudomonas aeruginosa strains characterised according to the CLSI/NCCLS microdilution method. Additional in vitro tests (time-kill curves and mutant prevention concentration (MPC) determinations) were carried out. Assuming a susceptibility breakpoint for prulifloxacin identical to that of ciprofloxacin, the new fluoroquinolone emerged as the most potent antibiotic (72% of susceptible strains versus 65%, 61% and 23% for ciprofloxacin, levofloxacin and moxifloxacin, respectively). Time-kill tests at 4x MIC confirmed the pronounced bactericidal potency of the drug against P. aeruginosa. Amongst the members of the fluoroquinolone class assessed, prulifloxacin produced the lowest MPC values (< or = 4 mg/L). Our in vitro results indicate that prulifloxacin represents the most powerful antipseudomonal drug available today.