Prospective randomized trial of piperacillin monotherapy versus carboxypenicillin-aminoglycoside combination regimens in the empirical treatment of serious bacterial infections

Systematic Review of Beta-Lactam vs. Beta-Lactam plus Aminoglycoside Combination Therapy in Neutropenic Cancer Patients

We performed a systematic review of studies that compared beta-lactams vs. beta-lactams plus aminoglycosides for the treatment of febrile neutropenia in cancer patients.

METHOD

We searched CENTRAL, MEDLINE, and Embase for studies published up to October 2023, and randomized controlled trials (RCTs) that compared anti-Pseudomonas aeruginosa beta-lactam monotherapy with any combination of an anti-Pseudomonas aeruginosa beta-lactam and an aminoglycoside were included.

RESULT

The all-cause mortality rate of combination therapy showed no significant differences compared with that of monotherapy (RR 0.99, 95% CI 0.84 to 1.16, high certainty of evidence). Infection-related mortality rates showed that combination therapy had a small positive impact compared with the intervention with monotherapy (RR 0.83, 95% CI 0.66 to 1.05, high certainty of evidence). Regarding treatment failure, combination therapy showed no significant differences compared with monotherapy (RR 0.99, 95% CI 0.94 to 1.03, low certainty of evidence). In the sensitivity analysis, the treatment failure data published between 2010 and 2019 showed better outcomes in the same beta-lactam group (RR 1.10 [95% CI, 1.01-1.19]). Renal failure was more frequent with combination therapy of any daily dosing regimen (RR 0.46, 95% CI 0.36 to 0.60, high certainty of evidence).

CONCLUSION

We found combining aminoglycosides with a narrow-spectrum beta-lactam did not spare the use of broad-spectrum antibiotics. Few studies included antibiotic-resistant bacteria and a detailed investigation of aminoglycoside serum levels, and studies that combined the same beta-lactams showed only a minimal impact with the combination therapy. In the future, studies that include the profile of antibiotic-resistant bacteria and the monitoring of serum aminoglycoside levels will be required.

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.

National Survey of Thai Infectious Disease Physicians on Treatment of Carbapenem-Resistant Acinetobacter baumannii Ventilator-Associated Pneumonia: The Role of Infection Control Awareness

OBJECTIVE To evaluate the expected and treatment outcomes of Thai infectious disease physicians (IDPs) regarding carbapenem-resistant Acinetobacter baumannii (CRAB) ventilator-associated pneumonia (VAP) METHODS From June 1, 2014, to March 1, 2015, survey data regarding the expected and clinical success rates of CRAB VAP treatment were collected from all Thai IDPs. The expected success rate was defined as the expectation of clinical response after CRAB VAP treatment for the given case scenario. Clinical success rate was defined as the overall reported success rate of CRAB VAP treatment based on the clinical practice of each IDP. The expected and clinical success rates were divided into low (80%) categories and were then compared with standard clinical response rates archived in the existing literature. RESULTS Of 183 total Thai IDPs, 111 (60%) were enrolled in this study. The median expected and clinical success rates were 68% and 58%, respectively. Using multivariate analysis, we determined that working in a hospital that implemented the standard intervention combined with an intensified infection control (IC) intervention for CRAB (adjusted odds ratio [aOR], 3.01; 95% confidence interval [CI], 1.17-7.73; P=.02) was associated with standard and high expected rates (>60%). Being a board-certified IDP (aOR, 5.76; 95% CI, 2.16-15.37; P60%). We identified a significant correlation between expected and clinical success rates (r=0.58; P<.001). CONCLUSIONS Awareness of IC among IDPs can improve physicians' expected and clinical success rates for CRAB VAP treatment, and treatment experience impacts overall treatment success. Infect. Control Hosp. Epidemiol. 2015;37(1):61-69.

Colloidal and antibacterial properties of novel triple-headed, double-tailed amphiphiles: exploring structure-activity relationships and synergistic mixtures

Two novel series of tris-cationic, tripled-headed, double-tailed amphiphiles were synthesized and the effects of tail length and head group composition on the critical aggregation concentration (CAC), thermodynamic parameters, and minimum inhibitory concentration (MIC) against six bacterial strains were investigated. Synergistic antibacterial combinations of these amphiphiles were also identified. Amphiphiles in this study are composed of a benzene core with three benzylic ammonium bromide groups, two of which have alkyl chains, each 8-16 carbons in length. The third head group is a trimethylammonium or pyridinium. Log of critical aggregation concentration (log[CAC]) and heat of aggregation (ΔHagg) were both inversely proportional to the length of the linear hydrocarbon chains. Antibacterial activity increases with tail length until an optimal tail length of 12 carbons per chain, above which, activity decreased. The derivatives with two 12 carbon chains had the best antibacterial activity, killing all tested strains at concentrations of 1-2μM for Gram-positive and 4-16μM for Gram-negative bacteria. The identity of the third head group (trimethylammonium or pyridinium) had minimal effect on colloidal and antibacterial activity. The antibacterial activity of several binary combinations of amphiphiles from this study was higher than activity of individual amphiphiles, indicating that these combinations are synergistic. These amphiphiles show promise as novel antibacterial agents that could be used in a variety of applications.

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.

Beta-lactam versus beta-lactam-aminoglycoside combination therapy in cancer patients with neutropenia

BACKGROUND

Continued controversy surrounds the optimal empirical treatment for febrile neutropenia. New broad-spectrum beta-lactams have been introduced as single treatment, and classically, a combination of a beta-lactam with an aminoglycoside has been used.

OBJECTIVES

To compare beta-lactam monotherapy versus beta-lactam-aminoglycoside combination therapy for cancer patients with fever and neutropenia.

SEARCH METHODS

The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 7, 2012), LILACS (August 2012), MEDLINE and EMBASE (August 2012) and the Database of Abstracts of Reviews of Effects (DARE) (Issue 3, 2012). We scanned references of all included studies and pertinent reviews and contacted the first author of each included trial, as well as the pharmaceutical companies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing any beta-lactam antibiotic monotherapy with any combination of a beta-lactam and an aminoglycoside antibiotic, for the initial empirical treatment of febrile neutropenic cancer patients. All cause mortality was the primary outcome assessed.

DATA COLLECTION AND ANALYSIS

Data concerning all cause mortality, infection related mortality, treatment failure (including treatment modifications), super-infections, adverse effects and study quality measures were extracted independently by two review authors. Risk ratios (RRs) with their 95% confidence intervals (CIs) were estimated. Outcomes were extracted by intention-to-treat (ITT) analysis whenever possible. Individual domains of risk of bias were examined through sensitivity analyses. Published data were complemented by correspondence with authors.

MAIN RESULTS

Seventy-one trials published between 1983 and 2012 were included. All cause mortality was lower with monotherapy (RR 0.87, 95% CI 0.75 to 1.02, without statistical significance). Results were similar for trials comparing the same beta-lactam in both trial arms (11 trials, 1718 episodes; RR 0.74, 95% CI 0.53 to 1.06) and for trials comparing different beta-lactams－usually a broad-spectrum beta-lactam compared with a narrower-spectrum beta-lactam combined with an aminoglycoside (33 trials, 5468 episodes; RR 0.91, 95% CI 0.77 to 1.09). Infection related mortality was significantly lower with monotherapy (RR 0.80, 95% CI 0.64 to 0.99). Treatment failure was significantly more frequent with monotherapy in trials comparing the same beta-lactam (16 trials, 2833 episodes; RR 1.11, 95% CI 1.02 to 1.20), and was significantly more frequent with combination therapy in trials comparing different beta-lactams (55 trials, 7736 episodes; RR 0.92, 95% CI 0.88 to 0.97). Bacterial super-infections occurred with equal frequency, and fungal super-infections were more common with combination therapy. Adverse events were more frequent with combination therapy (numbers needed to harm 4; 95% CI 4 to 5). Specifically, the difference with regard to nephrotoxicity was highly significant. Adequate trial methods were associated with a larger effect estimate for mortality and smaller effect estimates for failure. Nearly all trials were open-label. No correlation was noted between mortality and failure rates and these trials.

AUTHORS' CONCLUSIONS

Beta-lactam monotherapy is advantageous compared with beta-lactam-aminoglycoside combination therapy with regard to survival, adverse events and fungal super-infections. Treatment failure should not be regarded as the primary outcome in open-label trials, as it reflects mainly treatment modifications.

Antimicrobial agent exposure and the emergence and spread of resistant microorganisms: issues associated with study design

Antibiotics are essential agents that have greatly reduced human mortality due to infectious diseases. Their use, and sometimes overuse, have increased over the past several decades in humans, veterinary medicine and agriculture. However, the emergence of resistant pathogens is becoming an increasing problem that could result in the re-emergence of infectious diseases. Antibiotic prescription in human medicine plays a key role in this phenomenon. Under selection pressure, resistance can emerge in the commensal flora of treated individuals and disseminate to others. However, even if the effects of antimicrobial use on resistance is intuitively accepted, scientific rationales are required to convince physicians, legislators and public opinion to adopt appropriate behaviours and policies. With this review, we aim to provide an overview of different epidemiological study designs that are used to study the relationship between antibiotic use and the emergence and spread of resistance, as well as highlight their main strengths and weaknesses.

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.

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.

Antibacterial-resistant Pseudomonas aeruginosa: clinical impact and complex regulation of chromosomally encoded resistance mechanisms

Treatment of infectious diseases becomes more challenging with each passing year. This is especially true for infections caused by the opportunistic pathogen Pseudomonas aeruginosa, with its ability to rapidly develop resistance to multiple classes of antibiotics. Although the import of resistance mechanisms on mobile genetic elements is always a concern, the most difficult challenge we face with P. aeruginosa is its ability to rapidly develop resistance during the course of treating an infection. The chromosomally encoded AmpC cephalosporinase, the outer membrane porin OprD, and the multidrug efflux pumps are particularly relevant to this therapeutic challenge. The discussion presented in this review highlights the clinical significance of these chromosomally encoded resistance mechanisms, as well as the complex mechanisms/pathways by which P. aeruginosa regulates their expression. Although a great deal of knowledge has been gained toward understanding the regulation of AmpC, OprD, and efflux pumps in P. aeruginosa, it is clear that we have much to learn about how this resourceful pathogen coregulates different resistance mechanisms to overcome the antibacterial challenges it faces.

Antibacterial-resistant Pseudomonas aeruginosa: clinical impact and complex regulation of chromosomally encoded resistance mechanisms

Treatment of infectious diseases becomes more challenging with each passing year. This is especially true for infections caused by the opportunistic pathogen Pseudomonas aeruginosa, with its ability to rapidly develop resistance to multiple classes of antibiotics. Although the import of resistance mechanisms on mobile genetic elements is always a concern, the most difficult challenge we face with P. aeruginosa is its ability to rapidly develop resistance during the course of treating an infection. The chromosomally encoded AmpC cephalosporinase, the outer membrane porin OprD, and the multidrug efflux pumps are particularly relevant to this therapeutic challenge. The discussion presented in this review highlights the clinical significance of these chromosomally encoded resistance mechanisms, as well as the complex mechanisms/pathways by which P. aeruginosa regulates their expression. Although a great deal of knowledge has been gained toward understanding the regulation of AmpC, OprD, and efflux pumps in P. aeruginosa, it is clear that we have much to learn about how this resourceful pathogen coregulates different resistance mechanisms to overcome the antibacterial challenges it faces.

Empiric therapy for febrile neutropenia: what are the choices?

The management of febrile neutropenia has evolved gradually over the years toward a risk-adapted strategy based on validated prediction rules by risk of complications. The drug choice for empiric therapy is influenced by several factors, either related to the patient or to the institution. Microbiological distribution of offending pathogens and their pattern of susceptibility to antibiotics are continuously changing. New mechanisms of resistance in both Gram-negative and -positive bacteria have emerged. Guidelines and general statements should always be considered with the local epidemiology.

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 have certain advantages over beta-lactam monotherapy.

OBJECTIVES

We compared clinical outcomes for beta lactam-aminoglycoside combination therapy versus beta lactam monotherapy for sepsis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library, Issue 3, 2004); MEDLINE (1966 to July 2004); EMBASE (1980 to March 2003); LILACS (1982 to July 2004); and conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (1995 to 2003). We scanned citations of all identified studies and contacted all corresponding authors.

SELECTION CRITERIA

We included randomized and quasi-randomized trials comparing any beta-lactam monotherapy to any combination of one beta-lactam and one aminoglycoside for sepsis.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause fatality. Secondary outcomes included treatment failure, superinfections, colonization, and adverse events. Two authors independently collected data. We pooled relative risks (RR) with their 95% confidence intervals (CI) using the fixed effect model. We extracted outcomes by intention-to-treat analysis whenever possible.

MAIN RESULTS

We included 64 trials, randomizing 7586 patients. Twenty trials compared the same beta-lactam in both study arms, while the remaining compared different beta-lactams using a broader spectrum beta-lactam in the monotherapy arm. In studies comparing the same beta-lactam, we observed no difference between study groups with regard to all-cause fatality, RR 1.01 (95% CI 0.75-1.35) and clinical failure, RR 1.11 (95% CI 0.95-1.29). In studies comparing different beta-lactams, we observed an advantage to monotherapy: all cause fatality RR 0.85 (95% CI 0.71-1.01), clinical failure RR 0.77 (95% CI 0.69-0.86). No significant disparities emerged from subgroup and sensitivity analyses, including the assessment of patients with Gram-negative and Pseudomonas aeruginosa infections. We detected no differences in the rate of resistance development. Adverse events rates did not differ significantly between the study groups overall, although nephrotoxicity was significantly more frequent with combination therapy, RR 0.30 (95% CI 0.23-0.39). We found no heterogeneity for all comparisons. We included a small subset of studies addressing patients with Gram-positive infections, 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 fatality rates are unchanged. Combination treatment carries a significant risk of nephrotoxicity.

Effect of Aminoglycoside and β‐Lactam Combination Therapy versus β‐Lactam Monotherapy on the Emergence of Antimicrobial Resistance: A Meta‐analysis of Randomized, Controlled Trials

BACKGROUND

The addition of an aminoglycoside to a beta -lactam therapy regimen has been suggested to have a beneficial effect in delaying or preventing the development of antimicrobial resistance. We studied the effect of aminoglycoside/ beta -lactam combination therapy versus beta-lactam monotherapy on the emergence of resistance.

METHODS

We performed a meta-analysis of randomized, controlled trials (RCTs) that compared aminoglycoside/ beta-lactam combination therapy with beta-lactam monotherapy and that reported data regarding the emergence of resistance (primary outcome) and/or development of superinfection, treatment failure, treatment failure attributable to emergence of resistance, treatment failure attributable to superinfection, all-cause mortality during treatment, and mortality due to infection. Data for this meta-analysis were identified from the PubMed database, Current Contents database, Cochrane central register of controlled trials, and references in relevant articles.

RESULTS

A total of 8 RCTs were included in the analysis. Beta -lactam monotherapy was not associated with a greater emergence of resistance than was the aminoglycoside/ beta-lactam combination (odds ratio [OR], 0.90; 95% confidence interval [CI], 0.56-1.47). Actually, beta -lactam monotherapy was associated with fewer superinfections (OR, 0.62; 95% CI, 0.42-0.93) and fewer treatment failures (OR, 0.62; 95% CI, 0.38-1.01). Rates of treatment failure attributable to emergence of resistance (OR, 3.09; 95% CI, 0.75-12.82), treatment failure attributable to superinfection (OR, 0.60; 95% CI, 0.33-1.10), all-cause mortality during treatment (OR, 0.70; 95% CI, 0.40-1.25), and mortality due to infection (OR, 0.74; 95% CI, 0.46-1.21) did not differ significantly between the 2 regimens.

CONCLUSIONS

Compared with beta-lactam monotherapy, the aminoglycoside/ beta-lactam combination was not associated with a beneficial effect on the development of antimicrobial resistance among initially antimicrobial-susceptible isolates.

Evaluation of a Clinical Pathway for Ventilator-Associated Pneumonia: Changes in Bacterial Flora and the Adequacy of Empiric Antibiotics over a Three-Year Period

BACKGROUND

Evaluation of causative pathogens is vital for optimizing empiric antibiotic therapy of ventilator-associated pneumonia (VAP). Based on previous data (Ann Surg 1998;227:743-755), empiric antibiotics for our VAP clinical pathway were modified to target early and late occurring pathogens (ampicillin/sulbactam during the first week of hospitalization; cefepime plus vancomycin afterwards). The objectives of this study were to compare organisms causing VAP over a three-year period to previous data, and to determine the adequacy of the empiric antibiotic regimens.

METHODS

A total of 299 critically ill trauma patients with VAP over a three-year period were studied retrospectively. The incidence of pathogens causing VAP in the study period were compared to a previously published study of a two-year period in our intensive care unit (ICU). Sensitivities of Pseudomonas aeruginosa and Acinetobacter baumannii were evaluated over the study period. The adequacy of empiric antibiotic therapy for each episode of VAP was determined. Therapy was considered to be adequate if one or more antibiotics had in vitro activity against the organism causing VAP.

RESULTS

Statistically significant changes in pathogens included increased Staphylococcus aureus (incidence 17% vs. 11%, p = 0.024) and decreased Acinetobacter baumannii (11% vs. 22%, p < 0.001). Susceptibility patterns were statistically unchanged except for increased resistance of P. aeruginosa to extended-spectrum penicillins (p = 0.016). Empiric therapy was adequate in 76% of VAP episodes.

CONCLUSIONS

The clinical pathway's empiric antibiotic regimen was associated with only modest changes in organisms causing VAP and provided a high rate of adequate empiric coverage.

Antimicrobial therapy for patients with severe sepsis and septic shock: an evidence-based review

OBJECTIVE

In 2003, critical care and infectious disease experts representing 11 international organizations developed management guidelines for antimicrobial therapy for patients with severe sepsis and septic shock that would be of practical use for the bedside clinician, under the auspices of the Surviving Sepsis Campaign, an international effort to increase awareness and improve outcome in severe sepsis.

DESIGN

The process included a modified Delphi method, a consensus conference, several subsequent smaller meetings of subgroups and key individuals, teleconferences, and electronic-based discussion among subgroups and among the entire committee.

METHODS

The modified Delphi methodology used for grading recommendations built on a 2001 publication sponsored by the International Sepsis Forum. We undertook a systematic review of the literature graded along five levels to create recommendation grades from A to E, with A being the highest grade. Pediatric considerations to contrast adult and pediatric management are in the article by Parker et al. on p. S591.

CONCLUSION

Since the prompt institution of therapy that is active against the causative pathogen is one of the most important predictors of outcome, clinicians must establish a system for rapid administration of a rationally chosen drug or combination of drugs when sepsis or septic shock is suspected. The expanding number of antibacterial, antifungal, and antiviral agents available provides opportunities for effective empiric and specific therapy. However, to minimize the promotion of antimicrobial resistance and cost and to maximize efficacy, detailed knowledge of the likely pathogens and the properties of the available drugs is necessary for the intensivist.

A rational approach to the evaluation and treatment of the infected patient in the intensive care unit

Critically ill patients are at increased risk of acquiring nosocomial infections. A thorough clinical evaluation and the selection of appropriate diagnostic techniques are important elements in the evaluation of these patients. Nonetheless, this selection process can be difficult because of the wide spectrum of disease that is seen in the ICU and the lack of standardized studies that have evaluated the different diagnostic methods that are available. Many different antimicrobials are available for the treatment of ICU-acquired infections. Most antimicrobial regimens have not been evaluated in large-scale, prospective, randomized trials. Until this information is available, the clinician must make an effort to be familiar with the different clinical and epidemiologic variables that can be used to stratify patients at the moment of selecting antimicrobial therapy. The information provided in this article, used in association with good clinical judgment, will help the critical care physician provide optimal initial management of the infected patient in the ICU.

Beta-lactam versus beta-lactam-aminoglycoside combination therapy in cancer patients with neutropaenia

BACKGROUND

Chemotherapy treated cancer patients are prone to neutropaenia and life-threatening infections. Early, empirical antibiotic treatment is therefore administered routinely to febrile neutropaenic patients. Currently, either beta-lactam-aminoglycoside combination treatment or beta-lactam monotherapy are recommended.

OBJECTIVES

We compared beta-lactam monotherapy versus beta-lactam-aminoglycoside combination therapy for cancer patients with fever and neutroepaenia.

SEARCH STRATEGY

We searched the Cochrane Cancer Network Register (searched July, 2000), the Cochrane Controlled Trials Register (Cochrane Library Issue 4, 2001), EMBASE (January 1980 to December 2000), LILACS (January 1982 to August 2001), MEDLINE (January 1966 to August 2001), and ICAAC conference proceedings (1995 to 2000). We scanned references of all included studies, pertinent reviews, and contacted the first author of each included trial and the pharmaceutical companies.

SELECTION CRITERIA

Randomised controlled trials comparing any beta-lactam antibiotic monotherapy to any combination of a beta-lactam and an aminoglycoside antibiotic, for the initial, empirical treatment of febrile neutropaenic cancer patients.

DATA COLLECTION AND ANALYSIS

Data concerning mortality, treatment failure (including treatment modifications), superinfections, adverse effects and study quality measures were extracted independently by two reviewers. Relative risks with their 95% confidence intervals (CI) were estimated. Outcomes were extracted by intention-to-treat analysis whenever possible.

MAIN RESULTS

Forty-six trials and 7642 patients were included. All cause mortality was the primary outcome assessed. For all mortality comparisons, no significant difference between monotherapy and combination therapy was seen, relative risk 0.85 (95% CI 0.72-1.02) for all studies combined. Treatment failure was the outcome reported in all included trials. No significant difference between study groups was shown for studies comparing the same beta-lactam, relative risk 1.12 (95% CI 0.96-1.29). A significant advantage to monotherapy was observed for studies comparing different beta-lactams, relative risk 0.86 (95% CI 0.80-0.93). Bacterial and fungal superinfections developed with similar frequencies in the monotherapy and combination treatment groups. Adverse events were significantly more common in the combination treatment group, relative risk 0.83, (95% CI 0.72-0.97). These included events associated with significant morbidity, primarily renal toxicity. Results were consistent for subgroup and sensitivity analyses.

REVIEWER'S CONCLUSIONS

We have shown an advantage to broad-spectrum beta-lactam monotherapy over beta-lactam-aminoglycoside combination therapy for febrile neutropaenia. This advantage comprises of 1) a similar, if not better, survival, 2) a significantly lower treatment failure rate, 3) comparable probability for secondary infections and, 4) most importantly, a lower rate of adverse events associated with significant morbidity. Monotherapy can be regarded, therefore, as the standard of care for febrile neutropaenic patients.

Comparison of ampicillin-sulbactam and imipenem-cilastatin for the treatment of acinetobacter ventilator-associated pneumonia

Acinetobacter organisms, which are a common cause of ventilator-associated pneumonia (VAP) in some health care centers, are becoming more resistant to such first-line agents as imipenem-cilastatin (Imi-Cil). Sulbactam has good in vitro activity against Acinetobacter organisms; thus, ampicillin-sulbactam (Amp-Sulb) may be a viable treatment alternative. The outcomes for critically ill trauma patients with Acinetobacter VAP treated with either Amp-Sulb or Imi-Cil were compared retrospectively. A total of 77 episodes in 75 patients were studied. Fourteen patients were treated with Amp-Sulb, and 63 patients were treated with Imi-Cil. Treatment efficacy was similar in the Amp-Sulb and Imi-Cil groups (93% vs. 83%, respectively; P>.05). No statistically significant differences between groups were noted with regard to associated mortality, duration of mechanical ventilation, or length of stay in the intensive care unit or hospital. However, adjunctive aminoglycoside therapy was used more often in the Amp-Sulb group. Patients generally received Amp-Sulb because of imipenem resistance. Amp-Sulb was effective in treating a small number of patients with Acinetobacter VAP; however, more data are needed.

Changing pattern of bacterial susceptibility to antibiotics in hematopoietic stem cell transplant recipients

Adequate infection prophylaxis and empirical antibiotic therapy are of critical importance after hematopoietic stem cell transplantation (HSCT). We examined the evolution of bacterial susceptibility to antibiotics in 492 patients (198 allografts and 294 autografts) transplanted between 1982 and 1999 and evaluated whether ciprofloxacin prophylaxis and an empirical antibiotic regimen (glycopeptide + third-generation cephalosporin) were still valid. We collected all susceptibility tests performed during the initial hospitalization on blood cultures as well as routine surveillance cultures and analyzed susceptibility to ciprofloxacin and to major antibiotics used in our unit. Gram-positive cocci rapidly became resistant to ciprofloxacin (susceptibility around 70% in 1990 to less than 20% in 1998) but sensitivity to glycopeptides remained unaltered. There was a rapid decline in the number of patients colonized with Gram-negative bacilli in the early years of ciprofloxacin prophylaxis. However, susceptibility to ciprofloxacin fell sharply from around 90% in 1990 to around 30% in 1999. In parallel, susceptibility to ceftazidime also decreased to less than 80% in recent years. Piperacillin (+/- tazobactam) did not show any variation over time and its efficacy remained too low (about 60%). Imipenem as well as recently introduced cefepim and meropenem showed stable and excellent profiles (>90% susceptibility).

IN CONCLUSION

(1) quinolone prophylaxis has now lost most of its value; (2) the choice of a third-generation cephalosporin for empirical antibiotic therapy may no longer be the best because of the emergence of Gram-negative strains resistant to beta-lactamases, such as Enterobacter sp. More appropriate regimens of empirical antibiotic therapy in HSCT recipients may be based on the use of a carbapenem or fourth-generation cephalosporin.

In vitro synergistic activities of tobramycin and selected beta-lactams against 75 gram-negative clinical isolates

The microdilution checkerboard technique was utilized to distinguish synergistic activity between tobramycin and four beta-lactams: piperacillin-tazobactam, ticarcillin-clavulanate, ceftazidime, and ceftriaxone. Beta-lactam-aminoglycoside combinations were tested against 75 clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumanii, Citrobacterfreundii, Serratia marcescens, and Enterobacter cloacae. Despite in vitro susceptibilities, all isolates demonstrated either synergism or indifference; no antagonism was observed. Against pathogenic gram-negative nosocomial isolates, a greater percentage of synergy was consistently observed with combination regimens containing tobramycin and piperacillin-tazobactam or ticarcillin-clavulanate than with the cephalosporin-containing regimens.

Antibiotic selection in the treatment of endophthalmitis: the significance of drug combinations and synergy

Emerging resistance of organisms to standard antibiotic therapy has forced clinicians to continually evaluate the best intraocular antibiotics for the treatment of endophthalmitis. Early diagnosis and appropriate treatment with intraocular antibiotics are important factors in the successful management of endophthalmitis. Although drug combinations are necessary to cover the full range of bacteria causing endophthalmitis, antimicrobial synergy is probably less important in endophthalmitis treatment because of the high intravitreal concentration of individual antibiotics achieved by intravitreal injection. In the treatment of bacterial endophthalmitis, the combination of intravitreal vancomycin (1 mg/0.1 cc) and ceftazidime (2.25 mg/ 0.1 cc) is a reasonable alternative to the combination vancomycin and amikacin (0.4 mg/ 0.1 cc).

Monotherapy with meropenem versus combination therapy with ceftazidime plus amikacin as empiric therapy for fever in granulocytopenic patients with cancer. The International Antimicrobial Therapy Cooperative Group of the European Organization for Research and Treatment of Cancer and the Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto Infection Program

Combinations of beta-lactams plus aminoglycosides have been standard therapy for suspected infections in granulocytopenic cancer patients, especially those with profound long-lasting granulocytopenia. With the advent of new broad-spectrum bactericidal antibiotics such as extended-spectrum cephalosporins or carbapenems, the need to combine beta-lactams with aminoglycosides became more controversial. The objective of this prospective randomized multicenter study was to compare the efficacy, safety, and tolerance of meropenem monotherapy with those of the combination of ceftazidime plus amikacin for the empirical treatment of fever in granulocytopenic cancer patients. Of 1,034 randomized patients, 958 were assessable in the intent-to-treat analysis for response to antibacterial therapy, including 483 in the meropenem group and 475 in the ceftazidime-plus-amikacin group. The median durations of neutropenia were 16 and 17 days, respectively. A successful outcome was reported in 270 of 483 (56%) patients treated with monotherapy compared with 245 of 475 (52%) patients treated with the combination group (P = 0.20). The success rates in the monotherapy group and the combination group were similar by type of infection (single gram-negative bacteremia, single gram-positive bacteremia, clinically documented infection, and possible infection). The occurrence of further infections assessed in patients for whom the allocated regimen was not modified did not differ between the two groups (12% in both groups). Mortality due to the presenting infection or further infection was relatively low (8 patients treated with the monotherapy compared with 13 patients treated with the combination). A total of 1,027 patients were evaluable for adverse events; the proportion of those who developed adverse effects was similar between the two groups (29% in both groups), and only 19 (4%) patients in the monotherapy group and 31 (6%) in the combination group experienced an adverse event related or probably related to the study drug. Allergic reactions were the only reason for stopping the protocol antibiotic(s) (3 and 5 patients, respectively). This study confirms that monotherapy with meropenem is as effective as the combination of ceftazidime plus amikacin for the empiric treatment of fever in persistently granulocytopenic cancer patients, and both regimens were well tolerated.

Prospective randomized comparison of imipenem monotherapy with imipenem plus netilmicin for treatment of severe infections in nonneutropenic patients

Nosocomial pneumonia and sepsis, as well as severe diffuse peritonitis, must be treated early in order to prevent complications such as septic shock and organ dysfunctions. With the availability of new broad-spectrum and highly bactericidal antibiotics, the need of combining beta-lactams with aminoglycosides for the treatment of severe infections should be reassessed. A prospective randomized controlled study was performed to compare imipenem monotherapy with a combination of imipenem plus netilmicin in the empiric treatment of nosocomial pneumonia, nosocomial sepsis, and severe diffuse peritonitis. A total of 313 patients were enrolled, and 280 were assessable. The antibiotic treatment was successful in 113 of 142 patients (80%) given the monotherapy and in 119 of 138 patients (86%) given the combination (P = 0.19). The failure rates for the most important type of infection, i.e., pneumonia, were similar in the two groups, as well as the number of superinfections. While creatinine increase was associated with factors not related to antibiotic therapy for all eight patients of the monotherapy group, no factor other than the antibiotics could be found for 6 of the 14 cases of nephrotoxicity observed in the combination group (P = 0.014). Finally, the emergence of Pseudomonas aeruginosa resistant to imipenem occurred in 8 monotherapy patients and in 13 combination therapy patients. In conclusion, imipenem monotherapy appeared as effective as the combination of imipenem plus netilmicin for the treatment of severe infection. The addition of netilmicin increased nephrotoxicity, and it did not prevent the emergence of P. aeruginosa resistant to imipenem.

Infections in cancer patients: some controversial issues

Despite more than two decades of clinical research into the management of infections in the neutropenic cancer patient, many patients still develop serious morbidity from infection and all too many still die. A number of controversies surround (a) the use of combination versus monotherapy for initial empiric administration; (b) the use of vancomycin as part of the initial regimen; (c) the origin of Staphylococcus epidermidis infections (i.e., mostly from vascular catheters or mostly from the alimentary canal); (d) the use of acyclovir for herpes simplex prophylaxis during remission induction for acute leukemia patients not undergoing bone marrow transplantation; (e) the use of alimentary canal microbial suppression or reverse isolation in a room with laminar air flow, or both, as infection prevention techniques. Current recommendations and observations include the following. (a) Monotherapy with ceftazidime or imipenem is effective and appropriate for patients with moderate granulocytopenia at limited risk for infection with a resistant organism. Combination therapy is recommended for patients with profound, persistent granulocytopenia who are at high risk for gram-negative bacteremia; such bacteremic patients have a better prognosis with combined-modality therapy. (b) Vancomycin need not be included in the initial regimen although some centers may choose to do so because of the high prevalence of gram-positive bacteremias. (c) Despite the ubiquitous presence of indwelling vascular catheters, most S. epidermidis infections among neutropenic patients originate from along the alimentary canal. (d) Herpes simplex infection is much more common following standard remission induction chemotherapy than previously recognized. Acyclovir will reduce these infections and concurrently probably reduce the likelihood of resultant bacterial/fungal co-infections and superinfections. (e) Selective microbial suppression is appropriate for patients expected to experience prolonged (more than 2 weeks) or profound (below 100 granulocytes/microliters) granulocytopenia. Agents chosen should suppress aerobic but not anaerobic flora (maintain colonization resistance) and need to have an effect on both the oral cavity and esophagus as well as the intestines.

Penicillins. A current review of their clinical pharmacology and therapeutic use

The penicillins are a large group of bicyclic ring compounds which contain a 4-membered beta-lactam ring (penams) fused to a 5-membered thiazolidine ring. Benzylpenicillin (penicillin G) was the first natural penicillin with potent activity against all Gram-positive pathogens, Gram-negative cocci and some spirochaetes and actinomycetes. For the last 50 years benzylpenicillin has been the mainstay of therapy for serious pneumococcal, streptococcal, meningococcal and gonococcal infections. However, the past decade has seen the emergence of resistance in certain parts of the world, initially among the gonococci, and more recently among the pneumococci and meningococci. Discovery of the 6-aminopenicillinamic acid nucleus has led to considerable manipulation of the basic ring structure, resulting initially in the synthesis of ampicillin, and subsequently the other aminopenicillins, analogues, esters and prodrugs. These drugs have the advantages of improved oral bioavailability and superior activity against Haemophilus influenzae, certain Gram-negative bacilli, salmonellae, enterococci and Listeria monocytogenes, making these agents popular in the treatment of upper and lower respiratory tract infections and urinary tract infections. The increasing spread of bacterial resistance, particularly among Enterobacteriaceae and H. influenzae, has curtailed the usefulness of these drugs in these clinical settings. To counteract this problem, a number of agents combining a penicillin and a beta-lactamase inhibitor (e.g. clavulanic acid, tazobactam and sulbactam) have been developed. These inhibitors have no intrinsic antibacterial activity, but combining them with a penicillin (e.g. amoxicillin/clavulanic acid) confers greater stability to beta-lactamases and hence a broader spectrum of activity. The emergence of penicillinase-producing staphylococci that rendered benzylpenicillin ineffective also stimulated the search for penicillinase-resistant penicillins--methicillin and nafcillin, followed by the acid-stable isoxazolyl penicillins. These agents are now the principle antistaphylococcal treatment. Methicillin-resistant coagulase-negative staphylococci are currently a major cause of hospital sepsis, and are resistant to these latter agents. Enteric Gram-negative bacilli have been the predominant cause of serious hospital infections during the last 30 years. Further manipulation of the penicillin structure has resulted in compounds with broader activity against Gram-negative bacilli, particularly Pseudomonas aeruginosa, while retaining activity against Gram-positive pathogens. The carboxypenicillins were the first step in this direction, but have been largely superseded by the ureidopenicillins. These agents have better activity against P. aeruginosa, and are still effective against Gram-negative and Gram-positive bacteria, including enterococci and anaerobic organisms.(ABSTRACT TRUNCATED AT 400 WORDS)

Spectrum and treatment of bacterial infections in cancer patients with granulocytopenia

Bacterial infections remain a frequent cause of morbidity and mortality in cancer patients with granulocytopenia. In recent years the proportion of patients with gram-positive infections, caused mainly by coagulase-negative staphylococci and viridans streptococci, has increased markedly in many institutions. The precise reasons for this recent change in the epidemiology of infection in cancer patients are as yet not fully ascertained. Although less prevalent, gram-negative infections are still the major threat, since they are associated with higher mortality. What constitutes the optimal empirical antibiotic therapy remains a controversial issue. One should however recognize that the results of one particular study may not be relevant to other institutions where the predominant pathogens and the pattern of antibiotic resistance may be different. In addition, the results of studies using various antibiotic regimens should be compared with caution. However, with these limitations in mind, the results of the most recently published studies support the following recommendations: in patients with nonmicrobiologically documented infections, monotherapy with a third-generation cephalosporin or a carbapenem is a safe alternative to combination therapy. For gram-negative bacteremia, combined therapy with an extended-spectrum beta-lactam antibiotic and an aminoglycoside appears preferable. For gram-positive infections, a specific anti-gram-positive antibiotic is not needed in every patient and can safely be added upon identification of the pathogen in those patients not responding to empirical therapy.

Empiric treatment of infection during granulocytopenia

Results from clinical trials conducted over the past 15 years suggest the following: a) Early empiric therapy with broad-spectrum antibiotics directed against Gram-negative bacillary bacteremia is necessary in febrile granulocytopenic cancer patients; b) The level and dynamics of the granulocyte count are extremely important in determining the outcome of bacteremia; c) Most empiric antimicrobial regimens will require therapeutic modifications; these alterations are necessary and contribute to a high overall success rate; d) Only microbiologically documented infections and especially bacteremias are useful for comparison of initial response to antimicrobial regimens; e) The response rate of Gram-negative bacillary bacteremia is clearly influenced by the susceptibility of the causative pathogen to the beta-lactam component of the empiric regimen; emergence of resistance to some beta-lactam antibiotics is quite common and necessitates successive modifications of empiric regimens with time; f) The combination of an anti-pseudomonal beta-lactam with an aminoglycoside is recommended as the standard for empiric therapy in febrile granulocytopenic cancer patients, especially in those with severe and persistent granulocytopenia who are suspected of having Gram-negative bacillary bacteremia; less neutropenic and/or asymptomatic patients may do well with monotherapy; g) Gram-positive pathogens have become a common cause of bacteremia in granulocytopenic cancer patients; the response rate to empiric regimens may be suboptimal but the associated mortality is low; h) Patients with severe granulocytopenia and protracted fever whose blood cultures remain negative are at high risk for contracting fungal infections; in these patients, empiric antifungal agents are probably indicated.

A randomised trial of empirical antibiotic therapy in febrile neutropenic patients with hematological disorders: ceftazidime versus azlocillin plus amikacin

One hundred and two patients with neutropenia (less than 1 x 10(9)/L) secondary to primary hematological disorders or chemotherapy for hematological malignancies were prospectively randomised, upon the development of fever or other signs of infection, to receive empirical antibiotic treatment with either ceftazidime (+/- flucloxacillin) (n = 52) or azlocillin plus amikacin (+/- flucloxacillin) (A&A, n = 50). The two groups were equivalent with respect to clinical and laboratory parameters prior to antibiotic therapy and flucloxacillin was added to approximately 25% of the patients in each group on the clinical suspicion of Gram positive infection. When assessed at 96 hours, the complete response rates were 59.6% for the ceftazidime treated patients and 44% for A&A treated patients. Partial response rates were 17% and 20% respectively. This difference was not statistically significant. Eight patients died whilst on the trial, three of those initially randomised to ceftazidime and five initially randomised to A&A. Moderate to severe hypokalemia was encountered significantly less often in the ceftazidime treated group (p less than 0.01), whilst other parameters of toxicity were equivalent. No primary or acquired resistance to ceftazidime was encountered. Separate analysis of those patients who did not receive flucloxacillin yielded identical results. We conclude that ceftazidime (+/- flucloxacillin) is as efficacious as azlocillin plus amikacin (+/- flucloxacillin) in the empirical antibiotic management of such patients and is associated with a lower incidence of moderate to severe hypokalemia.

A review of chemoprophylaxis and therapy of bacterial infections in neutropenic patients

Gram-negative infections in neutropenic patients frequently originate from the intestinal flora. Attempts to decrease the incidence of these infections include several regimens for gastrointestinal decontamination, some of which have proved to be clinically useful. The orally administered nonabsorbable antibiotics such as aminoglycosides and polymyxins can decrease the incidence of Gram-negative sepsis during neutropenia. However, tolerance of these agents, with the possible exception of netilmicin, is very poor, and patient compliance is low. Cotrimoxazole (trimethoprim/sulfamethoxazole) has been widely used for prophylaxis of infections in neutropenic patients with variable clinical results. Its efficacy is clearly related to epidemiologic patterns of resistance to cotrimoxazole from potential pathogens in the population under study. More recently, the quinolones, which are well tolerated and inhibit most Enterobacteriaceae, have been associated with the virtual eradication of Gram-negative infections in neutropenic patients. These results are paralleled by an increase in the frequency of Gram-positive infections, for which the mortality rate is fortunately much lower than that seen in Gram-negative sepsis. In addition, quinolone antibiotics are absorbed systematically and this might help to explain their efficacy as chemoprophylaxis during neutropenia. Synergy, as demonstrated in vitro, and adequate bactericidal activity in the serum both correlate with improved clinical effectiveness in severe infections that occur during granulocytopenia. Whereas empiric antimicrobial therapy in febrile granulocytopenic cancer patients has become accepted medical practice, controversy still remains as to the optimal therapeutic regimen that should be used.

Randomized trial using piperacillin versus ampicillin and amikacin for treatment of premature neonates with risk factors for sepsis

Premature infants with risk factors for early onset sepsis who were less than seven days of age were blindly randomized to receive either piperacillin and placebo (200 infants) or ampicillin and amikacin (196 infants). One of 30 treated infants developed positive blood cultures. The overall mortality in the two groups was 8.5% for piperacillin/placebo and 13.8% for ampicillin/amikacin (p = 0.11). Serum creatinine elevation above 100 mumol/l (1.131 mg/dl) during treatment was similar in the two groups. The effectiveness of piperacillin/placebo is similar to that of ampicillin/amikacin for empiric treatment of premature newborns with risk factors for early onset sepsis.

Efficacy of ciprofloxacin alone and in combination with azlocillin in experimental endocarditis due to Pseudomonas aeruginosa

The efficacy of ciprofloxacin alone and in combination with azlocillin was compared with that of azlocillin plus tobramycin in a rat model of aortic valve endocarditis due to Pseudomonas aeruginosa. MICs against the infecting strain of ciprofloxacin, azlocillin and tobramycin were 0.125, 8, and 0.5 mg/l, respectively. Antimicrobials were administered 24 h after bacterial challenge and for six days. Mean peak/trough serum levels for ciprofloxacin (50 mg/kg i.v. q 12 h), azlocillin (500 mg/kg i.v. q 12 h) and tobramycin (6.5 mg/kg i.v. q 12 h) were: 10.5/0.2, 386/less than 16, and 6.2/less than 0.6 mg/l, respectively. Ciprofloxacin alone was more effective than the combination azlocillin-tobramycin in increasing survival (p less than 0.05), sterilizing blood (p less than 0.05) and valves (p less than 0.001), and in reducing bacterial titers in vegetations (p less than 0.001). Ciprofloxacin-azlocillin combination was not more effective than ciprofloxacin alone. Drug resistance was not encountered in post-treatment isolates with any therapy regimen.

Do antibiotic combinations prevent the emergence of resistant organisms?

Antibiotic combinations are often used in the therapy of infectious diseases to broaden the antibacterial spectrum and to enhance antimicrobial activity. Another potential reason for combination therapy is to reduce or prevent the emergence of resistant organisms during therapy. Antituberculous chemotherapy provides a classic example in which drug combinations have successfully prevented the emergence of drug-resistant organisms and improved clinical outcome. The purpose of this brief report is to review the success of combination therapy in preventing resistance in more common bacterial infections.

The emergence of resistance during single-drug therapy is a well-documented clinical phenomenon, especially with the broad-spectrum ß-lactams against gram-negative bacilli. As with Mycobacterium tuberculosis, the resistant organisms are generally thought to be naturally occurring mutants selected by drug exposure. Because mutation frequencies appear to vary from 10-6 to 10-8, it is not surprising that emergence of resistant organisms observed clinically occurs primarily at sites of high organism density, such as the respiratory and urinary tracts.

Comparison of once daily ceftriaxone with gentamicin plus cefuroxime for treatment of serious bacterial infections

To compare the efficacy of once daily monotherapy with that of standard combination antibiotic therapy for the initial management of patients suspected of serious bacterial infections, 105 patients were randomised to treatment with ceftriaxone alone (53 patients) or to a combination of cefuroxime and gentamicin (52 patients). There was no difference between the groups in proportions responding to therapy or proportions dying from infection, except when non-evaluable patients were excluded from the group with definite bacterial infection, in which case response was better among those treated with ceftriaxone. The groups did not differ in number of side-effects, but therapy had to be discontinued because of treatment failure, an adverse effect, or death in 1 of 53 patients given ceftriaxone and in 11 of 34 given the combination. Use of ceftriaxone was 107.36 pounds ($182.51) cheaper per patient, and saved 40 minutes of nursing and drug administration time per patient per day. Thus 2 g ceftriaxone given once a day is at least as effective and costs less in time and money than gentamicin plus cefuroxime for the initial treatment of patients with serious systemic bacterial infections.

Antibiotic combinations: should they be tested?

When antibiotic combinations are used to provide a broader spectrum of antimicrobial activity or in an attempt to prevent the emergence of resistant organisms, it is rarely necessary or practical to perform tests of drug interactions in vitro. In vitro testing of combinations may be useful when combinations are used in an attempt to attain synergistic interactions. In some cases, screening methods can be used as substitutes for formal synergy testing. This paper examines the mechanisms of antibiotic interaction leading to synergism or antagonism, surveys attempts to correlate in vitro observations with efficacy in animal models, and reviews clinical data providing evidence for or against a useful role of synergistic antibiotic interactions in the treatment of human infections.

Randomized trial of beta-lactam regimens in febrile neutropenic cancer patients

A three-arm prospective randomized trial was designed to compare the efficacies of piperacillin plus vancomycin, ceftazidime plus vancomycin, or all three drugs as initial therapy for fever in neutropenic cancer patients. The objectives were to determine whether a broad-spectrum penicillin was as effective as a broad-spectrum cephalosporin and whether two beta-lactam antibiotics were more effective than one. Four hundred and seventy of the 519 febrile episodes entered in the study could be evaluated for response. Ceftazidime plus vancomycin was significantly more effective than piperacillin plus vancomycin, considering all febrile episodes (79 percent versus 61 percent, p = 0.001), documented infections (79 percent versus 57 percent, p = 0.004), gram-negative infections (88 percent versus 47 percent, p = 0.001), and bacteremias (81 percent versus 51 percent, p = 0.01). The addition of piperacillin to ceftazidime (piperacillin plus ceftazidime and vancomycin versus ceftazidime plus vancomycin) did not improve the response rate and was associated with a significantly higher incidence of skin rash. Vancomycin plus ceftazidime provides adequate antibiotic coverage for initial treatment of fever in neutropenic patients. This combination was equally effective, less expensive, and less toxic than the double beta-lactam combination used in this study.

Empiric antimicrobial therapy for febrile granulocytopenic cancer patients. Lessons from four EORTC trials

The experience from four EORTC trials on antimicrobial therapy for febrile granulocytopenic cancer patients (GCP) is reviewed. A general conclusion from these trials is that studies of the management of infection in GCP should include sufficient numbers of eligible patients to allow for evaluation of bacteremic patients at highest risk of death. The need for large collaborative studies stems directly from these considerations.