Single versus combined antibiotic therapy for gram-negative infections

Combination antibiotic therapy versus monotherapy in the treatment of acute exacerbations of chronic obstructive pulmonary disease: an open-label randomized trial

Background

The role of antibiotics in the treatment of chronic obstructive pulmonary disease (COPD) exacerbations and their effectiveness in combination have not been clearly established. To determine whether using a combination of fluoroquinolones and beta-lactams improves the clinical and microbiological efficacy of antibiotics on day 20 of treatment, we conducted an open-label randomized trial based on clinical outcomes, microbiological clearance, spirometry tests, and signs of systemic inflammation in patients hospitalized with acute exacerbations of COPD.

Methods

We enrolled 139 subjects with COPD exacerbations, defined as acute worsening of respiratory symptoms leading to additional treatment. Patients were divided randomly into two groups: 79 patients using beta-lactam antibiotics alone and 60 using beta-lactam antibiotics plus fluoroquinolones. Clinical and microbiological responses, spirometry tests, symptom scores, and serum C-reactive protein (CRP) levels were evaluated.

Results

Clinical success, lung function, and symptoms were similar in patients with or without fluoroquinolone administration on days 10 and 20. Combination therapy was superior in terms of microbiological outcomes and reduction in serum CRP value. Although equivalent to monotherapy in terms of clinical success, the combination showed superiority in terms of microbiological success and a decrease in CRP. The combination therapy group had a higher microbiological success rate with gram-negative bacteria than the monotherapy group with Pseudomonas aeruginosa (100% vs. 33.3%, respectively) and Acinetobacter baumanii (100% vs. 20%, respectively) (P < 0.05).

Conclusions

Concomitant use of fluoroquinolone and beta-lactam antibiotics for bacterial infections during COPD exacerbations caused by gram-negative bacteria appear to be effective and should be applied in clinical practice.

Antibiotic sensitivity in correlation to the origin of secondary peritonitis: a single center analysis

Despite improvements in diagnosis, intensive-care medicine and surgical technique, the mortality of patients with secondary peritonitis is still high. Early and aggressive empiric antibiotic treatment has strong impact on the outcome. This retrospective study investigates bacterial and fungal pathogens and their antibiotic sensitivity in patients with secondary peritonitis. All patients that underwent emergency laparotomy due to secondary peritonitis at the Department of Surgery, University Medical Center Hamburg-Eppendorf between 2005 and 2015 were reviewed and overall 414 patients were included. We correlated the intra-abdominal localization of the organ perforation with intraoperative microbiological findings and corresponding sensitivities to relevant antibiotics. Overall, the most common findings were Escherichia coli (39%) and other Enterobacterica (24%). Depending on the location of the perforation, Cefuroxime/Metronidazole and Cefutaxime/Metronidazole were effective (based on in vitro susceptibility testing) in only 55–73% of the patients, while Meropenem/Vancomycin was able to control the peritonitis in more than 98% of the patients; independent of the location. Besides early source control, appropriate empiric treatment plays a pivotal role in treatment of secondary peritonitis. We are able to show that the frequently used combinations of second or third generation Cephalosporins with Metronidazole are not always sufficient, which is due to the biological resistance of the bacteria. Further clinical studies are needed to determine whether calculated use of broad-spectrum antibiotics with a sensitivity rate > 99%, such as Carbapenem plus Vancomycin, can improve overall survival rates in critically ill patients with secondary peritonitis.

Microbial findings, sensitivity and outcome in patients with postoperative peritonitis a retrospective cohort study

BACKGROUND

Acute postoperative peritonitis resulting from previous abdominal surgery is still a severe and potentially fatal disease, which is associated with high morbidity and mortality. The aim of the present study was to evaluate patients' outcome after postoperative peritonitis and identify the most effective empiric antibiotic regimes.

METHODS

422 patients with acute postoperative peritonitis as a result to earlier abdominal operation (e.g. anastomotic leakage) were analyzed retrospectively focusing on the origin of the peritonitis, microbial flora and resistance patterns. Furthermore, mortality was estimated according to sensitivity results of the tested antibiotics.

RESULTS

In 50% of the patients, anastomotic leakage was located in the colon. The predominantly cultured microorganisms were Escherichia coli and Enterobacteriaceae. The combination of meropenem and vancomycin was effective in 96% of these microbes. The frequently used combinations of piperacillin/sulbactam and cefotaxime/metronidazole were effective in only 67% and 43%, respectively.

CONCLUSIONS

We were able to show that the currently used antibiotic regimes with piperacillin/sulbactam and cefotaxime/metronidazole are ineffective in a relevant number of patients with anastomotic leakage. Only meropenem or meropenem/vancomycin cover most of the microbes predominant in postoperative peritonitis.

Utility of Combination Antimicrobial Therapy in Adults with Bloodstream Infections due to Enterobacteriaceae and Non-Fermenting Gram-Negative Bacilli Based on In Vitro Analysis at Two Community Hospitals

This study examined the utility of combination therapy for bloodstream isolates of Enterobacteriaceae and non-fermenting Gram-negative bacilli (NFGN) from adults at two community hospitals from January 2010 through to June 2015. Changes to in vitro antimicrobial susceptibilities by adding ciprofloxacin or gentamicin to third-generation cephalosporins (3GC) were examined overall and in patients with risk factors for 3GC resistance. Overall ceftriaxone susceptibility among Enterobacteriaceae was 996/1063 (94%) and 247/295 (84%) in patients with 3GC resistance risk factors. Susceptibilities increased marginally by adding ciprofloxacin or gentamicin (mean difference 2.4% (95% CI 1.5, 3.4) and 3.0% (95% CI 2.0, 4.0), respectively, overall and 5.4% (95% CI 2.8, 8.0) and 7.1% (95% CI 4.2, 10.1), respectively, in patients with risk factors). Eighty-three of 105 (79%) NFGN were susceptible to ceftazidime overall and 20/29 (69%) in patients with prior beta-lactam use. Overall mean increase in susceptibilities was 15.2% (95% CI: 8.3, 22.2) and 17.1% (95% CI: 9.8, 24.5) for ciprofloxacin and gentamicin combinations, respectively; and 27.6% (95% CI: 10.3, 44.9) for either one with recent beta-lactam use. In this setting, empirical combination therapy had limited utility for Enterobacteriaceae bloodstream isolates but provided significant additional antimicrobial coverage to ceftazidime for NFGN, particularly in patients with prior beta-lactam use.

Recovery rates of combination antibiotic therapy using in vitro microdialysis simulating in vivo conditions

Microdialysis is a technique used to measure the unbound antibiotic concentration in the interstitial spaces, the target site of action. In vitro recovery studies are essential to calibrating the microdialysis system for in vivo studies. The effect of a combination of antibiotics on recovery into microdialysate requires investigation. In vitro microdialysis recovery studies were conducted on a combination of vancomycin and tobramycin, in a simulated in vivo model. Comparison was made between recoveries for three different concentrations and three different perfusate flow rates. The overall relative recovery for vancomycin was lower than that of tobramycin. For tobramycin, a concentration of 20μg/mL and flow rate of 1.0μL/min had the best recovery. A concentration of 5.0μg/mL and flow rate of 1.0μL/min yielded maximal recovery for vancomycin. Large molecular size and higher protein binding resulted in lower relative recoveries for vancomycin. Perfusate flow rates and drug concentrations affected the relative recovery when a combination of vancomycin and tobramycin was tested. Low perfusate flow rates were associated with higher recovery rates. For combination antibiotic measurement which includes agents that are highly protein bound, in vitro studies performed prior to in vivo studies may ensure the reliable measurement of unbound concentrations.

Combination therapy vs. monotherapy for Gram-negative bloodstream infection: matching by predicted prognosis

The utility of empirical combination antimicrobial therapy for Gram-negative bloodstream infection (BSI) remains unclear. This retrospective, quasi-experimental matched cohort study examined the impact of empirical combination therapy on mortality in patients with Gram-negative BSI. Hospitalized adults with Gram-negative BSI from 1 January 2010 to 31 December 2013 at Palmetto Health Hospitals in Columbia, SC, USA were identified. Patients receiving combination therapy or beta-lactam monotherapy were matched 1:1 based on age, sex and Bloodstream Infection Mortality Risk Score (BSIMRS). Multivariate Cox proportional hazards regression with propensity score adjustment was used to examine overall 28-day mortality and within predefined BSIMRS categories (<5 and ≥5). A total of 380 patients receiving combination therapy or monotherapy for Gram-negative BSI were included in the study. Median age was 66 years and 204 (54%) were female. Overall, 28-day mortality in patients who received combination therapy and monotherapy was 13% and 15%, respectively (P = 0.51). After stratification by BSIMRS, mortality in both combination therapy and monotherapy groups was 1.1% in patients with BSIMRS <5 (P = 0.98) and 27% and 32%, respectively, in patients with BSIMRS ≥5 (P = 0.47). After adjusting for propensity to receive combination therapy, risk of mortality was not significantly different for combination therapy compared to monotherapy (hazard ratio [HR] 0.90, 95% confidence interval [CI] 0.51-1.60). This finding persisted for both subgroups of BSIMRS <5 (HR 0.96, 95% CI 0.04-24.28) and BSIMRS ≥5 (HR 0.83, 95% CI 0.46-1.48). There is no survival benefit from empirical combination therapy over monotherapy in patients with Gram-negative BSI, regardless of predicted prognosis at initial presentation.

WCK 5107 (Zidebactam) and WCK 5153 Are Novel Inhibitors of PBP2 Showing Potent "β-Lactam Enhancer" Activity against Pseudomonas aeruginosa, Including Multidrug-Resistant Metallo-β-Lactamase-Producing High-Risk Clones

Zidebactam and WCK 5153 are novel β-lactam enhancers that are bicyclo-acyl hydrazides (BCH), derivatives of the diazabicyclooctane (DBO) scaffold, targeted for the treatment of serious infections caused by highly drug-resistant Gram-negative pathogens. In this study, we determined the penicillin-binding protein (PBP) inhibition profiles and the antimicrobial activities of zidebactam and WCK 5153 against Pseudomonas aeruginosa, including multidrug-resistant (MDR) metallo-β-lactamase (MBL)-producing high-risk clones. MIC determinations and time-kill assays were conducted for zidebactam, WCK 5153, and antipseudomonal β-lactams using wild-type PAO1, MexAB-OprM-hyperproducing (mexR), porin-deficient (oprD), and AmpC-hyperproducing (dacB) derivatives of PAO1, and MBL-expressing clinical strains ST175 (bla_VIM-2) and ST111 (bla_VIM-1). Furthermore, steady-state kinetics was used to assess the inhibitory potential of these compounds against the purified VIM-2 MBL. Zidebactam and WCK 5153 showed specific PBP2 inhibition and did not inhibit VIM-2 (apparent K_i [K_iapp] > 100 μM). MICs for zidebactam and WCK 5153 ranged from 2 to 32 μg/ml (amdinocillin MICs > 32 μg/ml). Time-kill assays revealed bactericidal activity of zidebactam and WCK 5153. LIVE-DEAD staining further supported the bactericidal activity of both compounds, showing spheroplast formation. Fixed concentrations (4 or 8 μg/ml) of zidebactam and WCK 5153 restored susceptibility to all of the tested β-lactams for each of the P. aeruginosa mutant strains. Likewise, antipseudomonal β-lactams (CLSI breakpoints), in combination with 4 or 8 μg/ml of zidebactam or WCK 5153, resulted in enhanced killing. Certain combinations determined full bacterial eradication, even with MDR MBL-producing high-risk clones. β-Lactam-WCK enhancer combinations represent a promising β-lactam "enhancer-based" approach to treat MDR P. aeruginosa infections, bypassing the need for MBL inhibition.

AFM probing the mechanism of synergistic effects of the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) with cefotaxime against extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli

Background

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae poses serious challenges to clinicians because of its resistance to many classes of antibiotics.

Methods and Findings

The mechanism of synergistic activity of a combination of (−)-epigallocatechin-3-gallate (EGCG) and β-lactam antibiotics cefotaxime was studied on Extended-spectrum β-lactamase producing Escherichia coli (ESBL-EC), by visualizing the morphological alteration on the cell wall induced by the combination using atomic force microscopy (AFM). Cells at sub-MICs (sub-minimum inhibitory concentrations) of cefotaxime were initially filamentated but recovered to the normal shape later, whereas cells at sub-MICs of EGCG experienced temporal disturbance on the cell wall such as leakage and release of cellular debris and groove formation, but later recovered to the normal shape. In contrast, the combination of cefotaxime and EGCG at their respective sub-MICs induced permanent cellular damages as well as continuous elongation in cells and eventually killed them. Flow cytometry showed that intracellular oxidative stress levels in the cell treated with a combination of EGCG and cefotaxime at sub-MICs were higher than those in the cells treated with either cefotaxime or EGCG at sub-MICs.

Conclusions

These results suggest that the synergistic effect of EGCG between EGCG and cefotaxime against ESBL-EC is related to cooperative activity of exogenous and endogenous reactive oxygen species (ROS) generated by EGCG and cefotaxime, respectively.

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.

In vitro activity of ceftaroline alone and in combination against clinical isolates of resistant gram-negative pathogens, including beta-lactamase-producing Enterobacteriaceae and Pseudomonas aeruginosa

Ceftaroline is a novel broad-spectrum cephalosporin that exhibits bactericidal activity against many gram-positive and -negative pathogens. However, the activity of ceftaroline cannot be solely relied upon for eradication of multidrug-resistant gram-negative isolates, such as Pseudomonas aeruginosa and extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, which represent a current clinical concern. As drug combinations might be beneficial by potential synergy, we evaluated the in vitro activity of ceftaroline combined with meropenem, aztreonam, cefepime, tazobactam, amikacin, levofloxacin, and tigecycline. Susceptibility testing was performed for 20 clinical P. aeruginosa isolates, 10 ESBL-producing Escherichia coli isolates, 10 ESBL-producing Klebsiella pneumoniae isolates, and 10 AmpC-derepressed Enterobacter cloacae isolates. Time-kill experiments were performed for 10 isolates using antimicrobials at one-fourth the MIC. Ceftaroline exhibited a MIC range of 0.125 to 1,024 microg/ml and was reduced 2- to 512-fold by combination with tazobactam (4 microg/ml) for ESBL-producing strains. In time-kill experiments, ceftaroline plus amikacin was synergistic against 90% of the isolates (and indifferent for one P. aeruginosa isolate). Ceftaroline plus tazobactam was indifferent for E. cloacae and P. aeruginosa strains but synergistic against 100% of E. coli and K. pneumoniae isolates. Combinations of ceftaroline plus meropenem or aztreonam were also synergistic for all E. coli and E. cloacae isolates, respectively, but indifferent against 90% of the other isolates. Finally, combinations of ceftaroline plus either tigecycline, levofloxacin, or cefepime were indifferent for 100% of the isolates. No antagonism was observed with any combination. Ceftaroline plus amikacin appeared as the most likely synergistic combination. This represents a promising therapeutic option, and further studies are warranted to elucidate the clinical value of ceftaroline combinations against resistant gram-negative pathogens.

Beta-lactam and fluoroquinolone combination antibiotic therapy for bacteremia caused by gram-negative bacilli

The role of combination antibiotic therapy with a beta-lactam and a fluoroquinolone for bacteremia caused by gram-negative bacilli, to our knowledge, has not been previously described. Much of the previous study of combination therapy has included beta-lactams and aminoglycosides. We conducted a large retrospective cohort study to evaluate 28-day all-cause mortality in patients with monomicrobial bacteremia due to aerobic gram-negative bacilli who received either a combination of beta-lactams and fluoroquinolones or beta-lactam monotherapy. We enrolled adult patients admitted to Mayo Clinic hospitals from 1 January 2001 to 31 October 2006 in the study. After stratification of patients by Pitt bacteremia scores, we used Cox regression models to estimate the hazard ratios (HR) for 28-day all-cause mortality after adjusting for the propensity to receive combination therapy. We identified 398 and 304 unique patients with bacteremia caused by gram-negative bacilli who received single and combination antibiotic therapy, respectively. In less severely ill patients with Pitt bacteremia scores of <4, combination therapy was associated with lower 28-day mortality than single therapy (4.2% [9 of 214] versus 8.8% [28 of 319]; adjusted HR, 0.44; 95% confidence interval [CI], 0.20 to 0.98; P = 0.044). In critically ill patients with Pitt bacteremia scores of >or=4, there was no difference in 28-day mortality between combination and single therapy (25.6% [23 of 90] versus 27.8% [22 of 79]; adjusted HR, 0.87; 95% CI, 0.47 to 1.62; P = 0.660). These findings were consistent for 14-day all-cause mortality. In this large cohort, we found for the first time that combination therapy with beta-lactams and fluoroquinolones was associated with a reduction in 28-day all-cause mortality among less severely ill patients with bacteremia caused by gram-negative bacilli.

Defining, treating and preventing hospital acquired pneumonia: European perspective

INTRODUCTION

Many controversies still remain in the management of hospital acquired pneumonia (HAP), and ventilation-acquired pneumonia (VAP), Three European Societies, European Respiratory Society (ERS), European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and European Society of Intensive Care Medicine (ESICM), were interested in producing a document on HAP and VAP with European perspective.

MATERIALS AND METHODS

The scientific committees from each Society designated one chairman; Antoni Torres (ERS), Harmut Lode (ESCMID) and Jean Carlet (ESICM). The chairmen of this Task Force suggested names from each Society to be a member of the panel. They also choose controversial topics on the field and others that were not covered by the last IDSA/ATS guidelines. Each topic was assigned to a pair of members to be reviewed and written. Finally, the panel defined 20 consensual points that were circulated several times among the members of the panel until total agreement was reached. A combination of evidences and clinical-based medicine was used to reach these consensus.

CONCLUSION

This manuscript reviews in depth several controversial or new topics in HAP and VAP. In addition 20 consensual points are presented. This manuscript may be useful for the development of future guidelines and to stimulate clinical research by lying out what is currently accepted and what is unknown or controversial.

Antibacterial and antifungal activities of teucrium royleanum (Labiatea)

The crude methanolic extract and subsequent fractions of Teucrium royleanum (Labiatea) were screened for antibacterial and antifungal activities. Against tested pathogens, crude extract and subsequent fractions demonstrated moderate to excellent antibacterial activities. Highest antibacterial activity was displayed by the ethyl acetate fraction against S. typhi (100%), against E.coli (76.7%) and against P. aerugenosa (70.8%) followed by the chloroform fraction against S. typhi (85.7%). Similarly, the crude extract and its subsequent fractions showed mild to excellent activities in the antifungal bioassay with maximum antifungal activity against M. canis (87%) by the chloroform fraction followed by the ethyl acetate (71%) and n-butanol (70%) fractions.

Pneumonien

Die heute gebräuchlichen Definitionen der unterschiedlichen Formen der Pneumonie haben nicht nur eine begrifflich ordnende Funktion, sondern bezeichnen jeweils spezifische ätiopathogenetische, diagnostische und therapeutische Konzepte. Es kommt ihnen somit ein klinisch handlungsanweisender Wert zu.

Nosocomial pneumonia

PURPOSE OF REVIEW

This review describes the most recent advances in the management and prevention of nosocomial pneumonia. The new ATS guidelines in particular are most likely to affect clinical practice outside the USA.

RECENT FINDINGS

The problem of multidrug-resistant bacteria causing nosocomial pneumonia seems to be increasing. This is particularly true for methicillin-resistant Staphylococcus aureus. While the diagnosis of ventilator associated pneumonia remains a conflictive issue, serial tracheobronchial aspirates may improve the selection of adequate antimicrobial treatment. Combined beta-lactam and aminoglycoside therapy is inferior to beta-lactam monotherapy, both in terms of clinical outcome and in the prevention of resistance during treatment; in addition, it carries an increased risk of nephrotoxicity.

SUMMARY

The updated ATS guidelines will considerably impact clinical approaches to nosocomial and healthcare-related pneumonia. Serial tracheobronchial aspirates can be used to guide selection of antimicrobial treatment in ventilator associated pneumonia. The combination of beta-lactams and aminoglycosides is likely to be abandoned in the future. New potent treatment options for pneumonia due to nonfermenters are urgently needed.

Pharmacodynamics: relation to antimicrobial resistance

Antibiotic pharmacodynamics (PD) describes the impact of an antimicrobial agent on a target pathogen and is based on the drug's pharmacokinetics (PK) and microbiologic activity toward that pathogen, together with the pathogen's susceptibility to the drug. Patient or host factors play an important role in antibiotic PD by affecting drug PK and patient susceptibility to infection. The 3 PD parameters commonly used to predict antibiotic efficacy are (1) the ratio of maximum serum concentration to the minimum inhibitory concentration (MIC) (Cmax/MIC); (2) the ratio of the area under the plasma concentration versus time curve (AUC) versus MIC (AUC/MIC) and (3) the duration of the dosing interval that plasma concentrations exceed the MIC (T>MIC). The Cmax/MIC ratio has been shown to predict aminoglycoside efficacy, AUC/MIC best describes fluoroquinolone, glycopeptide, and ketolide efficacy, and T>MIC best describes the efficacy of beta-lactams and macrolides. Traditionally, PK and PD (PK/PD) parameters have been used to predict antibiotic efficacy, but there is now increasing interest in trying to use PK/PD parameters to minimize development of resistance. With respect to fluoroquinolone resistance, the "mutant selection window" hypothesis has been developed to describe how drug exposures below the mutant prevention concentration may create conditions for the selection of resistant bacterial strains. The AUC/MIC ratio has also been used to describe fluoroquinolone drug exposures associated with either increased or decreased risk of resistance emergence. The accessory gene regulator (agr) locus in Staphylococcus aureus-and particularly agr group II-has been associated with reduced susceptibility or resistance of S aureus to vancomycin. Recent experiments suggest that the AUC/MIC ratio may be used to identify vancomycin exposures associated with emergence of resistance in S aureus. More generally, AUC/MIC ratios may be additive, and combination therapies may represent 1 approach to lowering the emergence rate of bacterial resistance associated with antibiotic therapy. But, further work needs to be done before this conclusion can be verified.

Pharmacodynamics: relation to antimicrobial resistance

Antibiotic pharmacodynamics (PD) describes the impact of an antimicrobial agent on a target pathogen and is based on the drug's pharmacokinetics (PK) and microbiologic activity toward that pathogen, together with the pathogen's susceptibility to the drug. Patient or host factors play an important role in antibiotic PD by affecting drug PK and patient susceptibility to infection. The 3 PD parameters commonly used to predict antibiotic efficacy are (1) the ratio of maximum serum concentration to the minimum inhibitory concentration (MIC) (C(max)/MIC); (2) the ratio of the area under the plasma concentration versus time curve (AUC) versus MIC (AUC/MIC) and (3) the duration of the dosing interval that plasma concentrations exceed the MIC (T>MIC). The C(max)/MIC ratio has been shown to predict aminoglycoside efficacy, AUC/MIC best describes fluoroquinolone, glycopeptide, and ketolide efficacy, and T>MIC best describes the efficacy of beta-lactams and macrolides. Traditionally, PK and PD (PK/PD) parameters have been used to predict antibiotic efficacy, but there is now increasing interest in trying to use PK/PD parameters to minimize development of resistance. With respect to fluoroquinolone resistance, the "mutant selection window" hypothesis has been developed to describe how drug exposures below the mutant prevention concentration may create conditions for the selection of resistant bacterial strains. The AUC/MIC ratio has also been used to describe fluoroquinolone drug exposures associated with either increased or decreased risk of resistance emergence. The accessory gene regulator (agr) locus in Staphylococcus aureus--and particularly agr group II--has been associated with reduced susceptibility or resistance of S aureus to vancomycin. Recent experiments suggest that the AUC/MIC ratio may be used to identify vancomycin exposures associated with emergence of resistance in S aureus. More generally, AUC/MIC ratios may be additive, and combination therapies may represent 1 approach to lowering the emergence rate of bacterial resistance associated with antibiotic therapy. But, further work needs to be done before this conclusion can be verified.

Gram-Negative Resistance in the Intensive Care Unit

Gram-negative resistance is an increasingly important consideration when initiating empiric antimicrobial therapy in intensive care units. Infection with a resistant organism has been associated with increased morbidity and mortality as well as increased hospital cost. Gram-negative resistance in intensive care units will likely continue to increase. Clinicians must aggressively manage infections in the intensive care unit while practicing the appropriate steps to minimize future resistance. This review article summarizes the epidemiology, risk factors, mechanisms of resistance, and management of infections due to resistant gram-negative organisms.