Review of studies of the impact on Gram-negative bacterial resistance on outcomes in the intensive care unit. Crit Care Med. 2009;37:1463-1469. [PMID: 19242341 DOI: 10.1097/ccm.0b013e31819ced02]

Rewiring Gram-Negative Bacteria Cell Surfaces with Bio-Orthogonal Chemistry via Liposome Fusion

The ability to tailor bacteria cell surfaces with non-native molecules is critical to advance the study of bacteria communication, cell behavior, and for next-generation therapeutics to improve livestock and human health. Such modifications would allow for novel control over cell behavior, cell-cell interactions, biofilm formation, adjuvant conjugation, and imaging. Current methods to engineer bacteria surfaces have made major advances but rely on complicated, slow, and often expensive molecular biology and metabolic manipulation methods with limited scope on the type of molecules installed onto the surface. In this report, we introduce a new straightforward method based on liposome fusion to engineer Gram-negative bacteria cells with bio-orthogonal groups that can subsequently be conjugated to a range of molecules (biomolecules, small molecules, probes, proteins, nucleic acids, ligands, and radiolabels) for further studies and programmed behavior of bacteria. This method is fast, efficient, inexpensive, and useful for installing a broad scope of ligands and biomolecules to Gram-negative bacteria surfaces.

Colonization and infection with extended-spectrum β-lactamase-producing Enterobacteriaceae in ICU patients: what impact on outcomes and carbapenem exposure?

OBJECTIVES

It remains uncertain whether colonization and infection with ESBL-producing Enterobacteriaceae (ESBL-PE) affect the outcomes for ICU patients. Our objectives were to measure the effects of ESBL-PE carriage and infection on mortality, ICU length of stay (LOS) and carbapenem exposure in this population.

METHODS

A cause-specific hazard model based on prospectively collected data was built to assess the impact of ESBL-PE colonization and infection on competing risks of death and ICU discharge at day 28 in a multicentre cohort of ICU patients. Carbapenem exposure during the ICU stay was compared between infected carriers, uninfected carriers and non-carriers.

RESULTS

Among the 16,734 included patients, 594 (3.5%) were ESBL-PE carriers, including 98 (16.4%) with one or more ESBL-PE infections during the ICU stay. After adjustment for baseline and time-dependent confounders, ESBL-PE infections increased the probability of death at day 28 [adjusted cause-specific hazard ratio (aCSHR), 1.825, 95% CI 1.235-2.699, P = 0.0026] and the ICU LOS (aCSHR for discharge alive at day 28, 0.563, 95% CI 0.432-0.733, P < 0.0001). ESBL-PE carriage without infection extended the LOS (aCSHR, 0.623, 95% CI, 0.553-0.702, P < 0.0001), without affecting mortality (aCSHR, 0.906, 95% CI, 0.722-1.136, P = 0.3916). Carbapenem exposure increased in both infected and uninfected carriers when compared with non-carriers (627, 241 and 69 carbapenem days per 1000 patient days, respectively, P < 0.001).

CONCLUSIONS

ESBL-PE infections increased carbapenem consumption, LOS and day 28 mortality. ESBL-PE infections were rather infrequent in carriers; however, even ESBL-PE carriage without infection increased carbapenem exposure and delayed discharge, thereby amplifying the selective pressure and the colonization pressure in the ICU.

Trends of 9,416 multidrug-resistant Gram-negative bacteria

OBJECTIVE

a resistance of hospital-acquired bacteria to multiple antibiotics is a major concern worldwide. The objective of this study was to investigate multidrugresistant (MDR) bacteria, clinical specimens, origin of specimen and trends, and correlate these with bacterial sensitivity and consumption of antimicrobials.

METHODS

9,416 bacteria of nosocomial origin were evaluated in a tertiary hospital, from 1999 to 2008. MDR was defined for Gram-negative bacteria (GNB) as resistance to two or more classes/groups of antibiotics.

RESULTS

GNB MDR increased by 3.7 times over the study period (p<0.001). Acinetobacter baumannii was the most prevalent (36.2%). Over the study period, there were significant 4.8-fold and 14.6-fold increases for A. baumannii and K. pneumoniae (p<0.001), respectively. Sixty-seven percent of isolates of MDR GNB were isolated in intensive care units. The resistance of A. baumannii to carbapenems increased from 7.4 to 57.5% during the study period and concomitant with an increased consumption.

CONCLUSION

that decade showed prevalence of GNB and a gradual increase in MDR GNB. There was an increase in carbapenem resistance of 50.1% during the study.

Influence of Colistin Dose on Global Cure in Patients with Bacteremia Due to Carbapenem-Resistant Gram-Negative Bacilli

The increasing prevalence of multidrug-resistant (MDR) nosocomial infections accounts for increased morbidity and mortality of such infections. Infections with MDR Gram-negative isolates are frequently treated with colistin. Based on recent pharmacokinetic studies, current colistin dosing regimens may result in a prolonged time to therapeutic concentrations, leading to suboptimal and delayed effective treatment. In addition, studies have demonstrated an association between an increased colistin dose and improved clinical outcomes. However, the specific dose at which these outcomes are observed is unknown and warrants further investigation. This retrospective study utilized classification and regression tree (CART) analysis to determine the dose of colistin most predictive of global cure at day 7 of therapy. Patients were assigned to high- and low-dose cohorts based on the CART-established breakpoint. The secondary outcomes included microbiologic outcomes, clinical cure, global cure, lengths of intensive care unit (ICU) and hospital stays, and 7- and 28-day mortalities. Additionally, safety outcomes focused on the incidence of nephrotoxicity associated with high-dose colistin therapy. The CART-established breakpoint for high-dose colistin was determined to be >4.4 mg/kg of body weight/day, based on ideal body weight. This study evaluated 127 patients; 45 (35%) received high-dose colistin, and 82 (65%) received low-dose colistin. High-dose colistin was associated with day 7 global cure (40% versus 19.5%; P = 0.013) in bivariate and multivariate analyses (odds ratio [OR] = 3.40; 95% confidence interval [CI], 1.37 to 8.45; P = 0.008). High-dose colistin therapy was also associated with day 7 clinical cure, microbiologic success, and mortality but not with the development of acute kidney injury. We concluded that high-dose colistin (>4.4 mg/kg/day) is independently associated with day 7 global cure.

Microbiologic characteristics and predictors of mortality in bloodstream infections in intensive care unit patients: A 1-year, large, prospective surveillance study in 5 Italian hospitals

BACKGROUND

Bloodstream infections (BSIs) from multidrug-resistant (MDR) bacteria cause morbidity and mortality in intensive care unit (ICU) patients worldwide. This study investigated the incidence of BSIs in 5 adult general ICUs in Rome, Italy, and evaluated the mortality rate and risk factors associated with these infections.

METHODS

Over a 12-month period, 1,318 patients were enrolled. Demographic characteristics, Simplified Acute Physiology Score II (SAPS II), comorbidities, and BSI isolate data were collected. After stratification for the outcome, statistical analysis was performed to assess the impact of patient risk factors on in-hospital mortality.

RESULTS

There were 324 BSIs in 175 patients recorded, with an in-hospital mortality rate of 46%. Univariate analysis revealed that SAPS II, cardiac comorbidity, and Klebsiella pneumoniae BSI were significantly associated with a higher risk of death. Having a K pneumoniae BSI and cardiac illness at admission were both confirmed to be associated with death by multivariate analysis (P = .0162 and P = .0158, respectively). Most of the K pneumoniae isolates showed high resistance rates to carbapenems.

CONCLUSION

BSIs caused by K pneumoniae and cardiovascular comorbidity in ICU patients are associated with a higher risk of death. Thorough surveillance for MDR pathogens and stratification of the patients' risk on admission into the ICU are key to improving the outcomes of these infections.

Evaluating state-specific antibiotic resistance measures derived from central line-associated bloodstream infections, national healthcare safety network, 2011

DISCLOSURE The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention or the Agency for Toxic Substances and Diseases Registry. OBJECTIVE Describe the impact of standardizing state-specific summary measures of antibiotic resistance that inform regional interventions to reduce transmission of resistant pathogens in healthcare settings. DESIGN Analysis of public health surveillance data. METHODS Central line-associated bloodstream infection (CLABSI) data from intensive care units (ICUs) of facilities reporting to the National Healthcare Safety Network in 2011 were analyzed. For CLABSI due to methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum cephalosporin (ESC)-nonsusceptible Klebsiella species, and carbapenem-nonsusceptible Klebsiella species, we computed 3 state-level summary measures of nonsusceptibility: crude percent nonsusceptible, model-based adjusted percent nonsusceptible, and crude infection incidence rate. RESULTS Overall, 1,791 facilities reported CLABSIs from ICU patients. Of 1,618 S. aureus CLABSIs with methicillin-susceptibility test results, 791 (48.9%) were due to MRSA. Of 756 Klebsiella CLABSIs with ESC-susceptibility test results, 209 (27.7%) were due to ESC-nonsusceptible Klebsiella, and among 661 Klebsiella CLABSI with carbapenem susceptibility test results, 70 (10.6%) were due to carbapenem-nonsusceptible Klebsiella. All 3 state-specific measures demonstrated variability in magnitude by state. Adjusted measures, with few exceptions, were not appreciably different from crude values for any phenotypes. When linking values of crude and adjusted percent nonsusceptible by state, a state's absolute rank shifted slightly for MRSA in 5 instances and only once each for ESC-nonsusceptible and carbapenem-nonsusceptible Klebsiella species. Infection incidence measures correlated strongly with both percent nonsusceptibility measures. CONCLUSIONS Crude state-level summary measures, based on existing NHSN CLABSI data, may suffice to assess geographic variability in antibiotic resistance. As additional variables related to antibiotic resistance become available, risk-adjusted summary measures are preferable.

Antibiotic Resistance of Pseudomonas aeruginosa in Pneumonia at a Single University Hospital Center in Germany over a 10-Year Period

BACKGROUND

Pseudomonas aeruginosa is a common cause of community-acquired and nosocomial-acquired pneumonia. The development of resistance of P. aeruginosa to antibiotics is increasing globally due to the overuse of antibiotics. This article examines, retrospectively, the antibiotic resistance in patients with community-acquired versus nosocomial-acquired pneumonia caused by P. aeruginosa or multidrug-resistant (MDR) P. aeruginosa.

METHODS

Data from patients with community-acquired and nosocomial-acquired pneumonia caused by P. aeruginosa and MDR P. aeruginosa were collected from the hospital charts at the HELIOS Clinic, Witten/Herdecke University, Wuppertal, Germany, between January 2004 and August 2014. An antibiogram was created from all study patients with community-acquired and nosocomial-acquired pneumonia caused by P. aeruginosa or MDR P. aeruginosa.

RESULTS

A total of 168 patients with mean age 68.1 ± 12.8 (113 [67.3% males and 55 [32.7%] females) were identified; 91 (54.2%) had community-acquired and 77 (45.8%) had nosocomial-acquired pneumonia caused by P. aeruginosa. Patients with community-acquired versus nosocomial-acquired pneumonia had a mean age of 66.4 ± 13.8 vs. 70.1 ± 11.4 years [59 vs. 54 (64.8% vs. 70.1%) males and 32 vs. 23 (35.2% vs. 29.9%) females]. They included 41 (24.4%) patients with pneumonia due to MDR P. aeruginosa: 27 (65.9%) community-acquired and 14 (34.1%) nosocomial-acquired cases. P. aeruginosa and MDR P. aeruginosa showed a very high resistance to fosfomycin (community-acquired vs. nosocomial-acquired) (81.0% vs. 84.2%; 0 vs. 85.7%). A similar resistance pattern was seen with ciprofloxacin (35.2% vs. 24.0%; 70.4% vs. 61.5%), levofloxacin (34.6% vs. 24.5%; 66.7% vs. 64.3%), ceftazidime (15.9% vs. 30.9; 33.3% vs. 61.5%), piperacillin (24.2% vs. 29.9%; 44.4% vs. 57.1%), imipenem (28.6% vs. 27.3%; 55.6% vs. 50.0%), piperacillin and tazobactam (23.1% vs. 28.6%; 44.4% vs. 50.0%), tobramycin (28.0% vs. 17.2%; 52.0% vs. 27.3%), gentamicin (26.4% vs. 18.2%; 44.4% vs. 21.4%), and meropenem (20.2% vs. 20.3%; 42.3% vs. 50.0%). An elevated resistance of P. aeruginosa and MDR P. aeruginosa was found for cefepime (11.1% vs. 23.3%; 25.9% vs. 50.0%), and amikacin (10.2% vs. 9.1%; 27.3% vs. 9.1%). Neither pathogen was resistant to colistin (P = 0.574).

CONCLUSION

While P. aeruginosa and MDR P. aeruginosa were resistant to a variety of commonly used antibiotics, they were not resistant to colistin in the few isolates recovered from patients with pneumonia.

Instant Typing Is Essential to Detect Transmission of Extended-Spectrum Beta-Lactamase-Producing Klebsiella Species

BACKGROUND

Infections with multidrug-resistant (MDR) microorganisms are an increasing threat to hospitalized patients. Although rapid typing of MDR microorganisms is required to apply targeted prevention measures, technical barriers often prevent this. We aimed to assess whether extended-spectrum beta-lactamase (ESBL)-producing Klebsiella species are transmitted between patients and whether routine, rapid typing is needed.

METHODS

For 43 months, the clonality of all ESBL-producing Klebsiella isolates from patients admitted to Erasmus MC University Medical Center in Rotterdam, the Netherlands was assessed with Raman spectroscopy. A cluster was defined as n ≥ 2 patients who had identical isolates. Primary patients were the first patients in each cluster. Secondary patients were those identified with an isolate clonally related to the isolate of the primary patient.

RESULTS

Isolates from 132 patients were analyzed. We identified 17 clusters, with 17 primary and 56 secondary patients. Fifty-nine patients had a unique isolate. Patients (n = 15) in four out of the 17 clusters were epidemiologically related. Ten of these 15 patients developed an infection.

CONCLUSIONS

Clonal outbreaks of ESBL-producing Klebsiella species were detected in our hospital. Theoretically, after Raman spectroscopy had detected a cluster of n ≥ 2, six infections in secondary patients could have been prevented. These findings demonstrate that spread of ESBL-producing Klebsiella species occurs, even in a non-outbreak setting, and underscore the need for routine rapid typing of these MDR bacteria.

Adipose Tissue-Derived Mesenchymal Stem Cells Attenuate Pulmonary Infection Caused by Pseudomonas aeruginosa via Inhibiting Overproduction of Prostaglandin E2

RATIONALE

New strategies for treating Pseudomonas aeruginosa pulmonary infection are urgently needed. Adipose tissue-derived mesenchymal stem cells (ASCs) may have a potential therapeutic role in P. aeruginosa-induced pulmonary infection.

METHODS

The therapeutic and mechanistic effects of ASCs on P. aeruginosa pulmonary infection were evaluated in a murine model of P. aeruginosa pneumonia.

RESULTS

ASCs exhibited protective effects against P. aeruginosa pulmonary infection, evidenced by reduced bacterial burdens, inhibition of alveolar neutrophil accumulation, decreased levels of myeloperoxidase, macrophage inflammatory protein-2 and total proteins in broncho-alveolar lavage fluid (BALF), and attenuated severity of lung injury. ASCs had no effects on BALF and serum levels of keratinocyte growth factor or Ang-1. ASCs had no effects on the levels of insulin growth factor 1 (IGF-1) in BALF, but increased IGF-1 levels in serum. ASCs inhibited the overproduction of prostaglandin E2 (PGE2 ) by decreasing the expression of cyclooxygenase-2 (COX2) and enhancing the expression of 15-PGDH. In addition, the addition of exogenous PGE2 with ASCs abolished many of the protective effects of ASCs, and administrating PGE2 alone exacerbated lung infection. By inhibiting production of PGE2 , ASCs improved phagocytosis and the bactericidal properties of macrophages. Furthermore suppressing PGE2 signaling by COX2 inhibition or EP2 inhibition exhibited protective effects against pulmonary infection as well.

CONCLUSIONS

In a murine model of P. aeruginosa pneumonia, ASCs exhibited protective effects by inhibiting production of PGE2 , which subsequently improved phagocytosis and the bactericidal properties of macrophages. ASCs may provide a new strategy for managing pulmonary infection caused by P. aeruginosa.

Resistance Rates of Intra-Abdominal Isolates from Intensive Care Units and Non-Intensive Care Units in the United States: The Study for Monitoring Antimicrobial Resistance Trends 2010-2012

BACKGROUND

Enterobacteriaceae (3,235 isolates), Pseudomonas aeruginosa (476 isolates), and Acinetobacter baumannii (106 isolates) from inpatient intra-abdominal infections (IAIs) were collected for the 2010-2012 Study for Monitoring Antimicrobial Resistance Trends (SMART) program in the United States. This report evaluates the in vitro activity of several antimicrobial agents recommended for treatment of IAIs and compares profiles of isolates from intensive care units (ICUs) and non-intensive care units (non-ICUs).

METHODS

Gram-negative bacilli from hospitalized patients with IAIs were obtained each year from 2010-2012 from hospitals in the United States and tested for susceptibility to 12 antibiotics according to 2012 Clinical and Laboratory Standards Institute (CLSI) guidelines.

RESULTS

The most active agents against members of the Enterobacteriaceae family from both ICUs and non-ICUs were amikacin, ertapenem, and imipenem-cilastatin, whereas the least active agent was ampicillin-sulbactam. Amikacin was the only agent with good activity against P. aeruginosa, whereas none of the agents tested exhibited substantial activity against A. baumannii. Amikacin, ceftazidime, ceftriaxone, ciprofloxacin, levofloxacin, and imipenem-cilastatin were significantly less active against Enterobacteriaceae from ICU patients, whereas cefepime and ceftazidime were significantly less active against P. aeruginosa from ICU patients. Intensive care unit isolates were more likely to be multi-drug-resistant than non-ICU isolates, although there was no difference in extended-spectrum β-lactamase (ESBL) production rates between the two patient groups.

CONCLUSIONS

Despite increasing resistance trends, in this study amikacin, ertapenem, and imipenem-cilastatin were shown to have good in vitro activity against the most frequently isolated gram-negative bacilli from IAIs in ICU and non-ICU settings.

Antibiotics against Pseudomonas aeruginosa for COPD exacerbation in ICU: a 10-year retrospective study

SUMMARY

Chronic obstructive pulmonary disease (COPD) is a frequent source of hospitalization. Antibiotics are largely prescribed during COPD exacerbation. Our hypothesis is that large broad-spectrum antibiotics are more and more frequently prescribed. Our results confirm this trend and highlight that the increase in large broad-spectrum use in COPD exacerbation is largely unexplained.

BACKGROUND

Acute COPD exacerbation (AECOPD) is frequently due to respiratory tract infection, and the benefit of antipseudomonal antibiotics (APA) is still debated. Health care-associated pneumonia (HCAP) was defined in 2005 and requires broad-spectrum antibiotherapy. The main objectives are to describe the antibiotic use for AECOPD in intensive care unit and to identify factors associated with APA use and AECOPD prognosis.

METHODS

We conducted a monocentric, retrospective study on all AECOPDs in the intensive care unit treated by antibiotics for respiratory tract infection. Treatment failure (TF) was defined by death, secondary need for mechanical ventilation, or secondary systemic steroid treatment. A multivariate analysis was used to assess factors associated with APA prescription and TF.

RESULTS

From January 2000 to December 2011, 111 patients were included. Mean age was 69 years (±12), mean forced expiratory volume 38% of theoretic value (±13). Thirty-five (31%) patients were intubated, and 52 (47%) were treated with noninvasive ventilation. From 107 patients, 8 (7%) cases of Pseudomonas aeruginosa were documented. APAs were prescribed in 21% of patients before 2006 versus 57% after (P=0.001). TF prevalence was 31%. Risk factors for P. aeruginosa in COPD and HCAP diagnosis did not influence APA, whereas the post-2006 period was independently associated with APA prescription (odds ratio 6.2; 95% confidence interval 1.9-20.3; P=0.0013). APA did not improve TF (odds ratio 1.09; 95% confidence interval 0.37-3.2).

CONCLUSION

HCAP guidelines were followed by an increase in APA use in AECOPD, without an improvement in prognosis. HCAP prevalence cannot account for the increasing APA trend. Time effect reveals a drift in practices. The microbiological effect of such a drift must be evaluated.

The costs of nosocomial resistant gram negative intensive care unit infections among patients with the systemic inflammatory response syndrome- a propensity matched case control study

Background

Infections due to multi-drug resistant gram negative bacilli (RGNB) in critically ill patients have been reported to be associated with increased morbidity and costs and only a few studies have been done in Asia. We examined the financial impact of nosocomial RGNB infections among critically ill patients in Singapore.

Methods

A nested case control study was done for patients at medical and surgical ICUs of a tertiary university hospital (August 2007-December 2011) matched by propensity scores. Two groups of propensity-matched controls were selected for each case patient with nosocomial drug resistant gram negative infection: at-risk patients with no gram negative infection or colonization (Control A) and patients with ICU acquired susceptible gram negative infection (SGNB) (Control B). The costs of the hospital stay, laboratory tests and antibiotics prescribed as well as length of stay were compared using the Wilcoxon matched-pairs signed rank test.

Results

Of the 1539 patients included in the analysis, 76 and 65 patients had ICU acquired RGNB and SGNB infection respectively. The median(range) total hospital bill per day for patients with RGNB infection was 1.5 times higher than at-risk patients without GNB infection [Singapore dollars 2637.8 (458.7-20610.3) vs. 1757.4 (179.9-6107.4), p0.0001]. The same trend was observed when compared with SGNB infected patients. The median costs per day of antibiotics and laboratory investigations were also found to be significantly higher for patients with RGNB infection. The length of stay post infection was not found to be different between those infected with RGNB and SGNB.

Conclusion

The economic burden of RGNB infections to the patients and the hospital is considerable. Efforts need to be taken to prevent their occurrence by cost effective infection control practices.

Stress responses as determinants of antimicrobial resistance in Pseudomonas aeruginosa: multidrug efflux and more

Pseudomonas aeruginosa is a notoriously antimicrobial-resistant organism that is increasingly refractory to antimicrobial chemotherapy. While the usual array of acquired resistance mechanisms contribute to resistance development in this organism a multitude of endogenous genes also play a role. These include a variety of multidrug efflux loci that contribute to both intrinsic and acquired antimicrobial resistance. Despite their roles in resistance, however, it is clear that these efflux systems function in more than just antimicrobial efflux. Indeed, recent data indicate that they are recruited in response to environmental stress and, therefore, function as components of the organism's stress responses. In fact, a number of endogenous resistance-promoting genes are linked to environmental stress, functioning as part of known stress responses or recruited in response to a variety of environmental stress stimuli. Stress responses are, thus, important determinants of antimicrobial resistance in P. aeruginosa. As such, they represent possible therapeutic targets in countering antimicrobial resistance in this organism.

Carbapenem resistant Gram-negative bacteremia in an Indian intensive care unit: A review of the clinical profile and treatment outcome of 50 patients

BACKGROUND

Growing antimicrobial resistance and limited therapeutic options to treat carbapenem-resistant bacteremia prompted us to evaluate the clinical outcomes associated with healthcare-associated bacteremia.

METHODS

This was a retrospective observational study of carbapenem-resistant Gram-negative bacteremia performed at a tertiary care facility in Chennai, India between May 2011 and May 2012.

RESULTS

In our study, patients had mean 11.76 days of intensive care unit (ICU) care and mean time to onset of bacteremia was 6.4 days after admission. The commonest organism was Klebsiella pneumoniae (44%). Patients with combination treatment had lower mortality (44.8%) compared with colistin monotherapy (66.6%); (P = 0.35).

CONCLUSION

Carbapenem resistant bacteremia is a late onset infection in patients with antibiotic exposure in the ICU and carries a 30 days mortality of 60%; K. pneumoniae is the most common organism at our center. Two drug combinations appear to carry a lower mortality compared with monotherapy.

De-escalation of antimicrobial treatment in neutropenic patients with severe sepsis: results from an observational study

BACKGROUND

In severe sepsis, guidelines recommend de-escalating the empirical antimicrobial treatment as soon as the microbiological results are available. We aimed to determine the rate of de-escalation of the empirical antimicrobial treatment in neutropenic patients with severe sepsis. The characteristics of antimicrobial treatment associated with de-escalation and its impact on short- and long-term survival were also determined.

METHODS

In the intensive care unit (ICU) of a cancer referral center, we prospectively collected observational data related to the antimicrobial management in neutropenic patients who developed severe sepsis and were admitted to ICU for at least 48 h. De-escalation of antimicrobial therapy consisted either of deleting one of the empirical antibiotics of a combined treatment, or, whenever possible, to use a betalactam antibiotic with a narrower spectrum of activity. Multivariate logistic regression was conducted to determine the factors associated with de-escalation, while a Cox proportional hazards model with a time-dependent covariate was fitted to assess the effect of de-escalation on 30-day survival. Finally 1-year survival after ICU discharge was compared across de-escalation groups.

RESULTS

Cumulative incidence of de-escalation of the empirical antimicrobial treatment among the 101 patients of the cohort was 44%, [95% confidence interval (CI) 38-53%], including 30 (68%) patients with ongoing neutropenia. A microbiological documentation was available in 63 (63%) patients. Factors associated with de-escalation were the adequation of the empirical antimicrobial treatment in ICU [OR = 10.8 (95% CI 1.20-96)] for adequate documented treatment versus appropriate empirical treatment, the compliance with guidelines regarding the empirical choice of the anti-pseudomonal betalactam [OR = 10.8 (95% CI 1.3-89.5)]. De-escalation did not significantly modify the hazard of death within the first 30 days [HR = 0.51 (95% CI 0.20-1.33)], nor within 1 year after ICU discharge [HR = 1.06 (95% CI 0.54-2.08)].

CONCLUSION

Our data suggest that, in ICU, de-escalation of the empirical antimicrobial treatment is frequently applied in neutropenic cancer patients with severe sepsis. No evidence of any prognostic impact of this de-escalation was found.

A multicenter point-prevalence survey of antibiotic use in 13 Chinese hospitals

BACKGROUND

The use of antibiotics is considered a major determinant of the development of resistance in organisms. This study assessed current patterns of antibiotic prescription and provides background for quality improvement in general hospitals in Hubei, China.

METHODS

A point-prevalence study was performed in November 2008. All inpatients on the day of the survey were included in the analysis.

RESULTS

On the day of the study, 6904 patients (56%) were receiving antibiotic therapy; the highest rate occurred in the ICU (90%), and the lowest occurred in the medical wards (39%). The most commonly used antibiotics were β-lactam antibiotics, including cephalosporins (40%) and piperacillin (19%), followed by fluoroquinolones (14%).

CONCLUSIONS

Our data indicated a high rate of antibiotic use in Chinese hospitals. These findings suggest important areas for intervention and the implementation of antibiotic stewardship policies in Chinese hospitals. A multi-faceted strategy should be implemented at the national level in China and should include education, regulation, and greater financial support from the government.

The impact of multidrug resistance on outcomes in ventilator-associated pneumonia

Multidrug-resistant (MDR) organisms in ventilator-associated pneumonia were found in 49 of 107 patients and were associated with home antibiotics, pre-ventilator-associated pneumonia hospital stay, and health care exposure. Overall, MDR organisms were associated with increased mortality (P = .006). On multivariate analysis, MDR status was modulated by organism class. In nonfermenting gram-negative rods, no association between MDR and mortality was found, but, in all other organisms, MDR was associated with increased mortality risk (hazard ratio, 6.15; 95% confidence interval: 1.80-21.05, P = .004).

Prevalence of antibiotic resistance in US hospitals

The percentage of isolates resistant to essential antibiotics among clinically significant bacterial pathogens was evaluated using data from 80089 qualifying admissions in 19 US hospitals (2007-2010). Percentage resistant was highest for the following pathogen/antibiotic pairs: Enterococcus faecium/vancomycin (87.1% [95% CI 86.0-88.1] of 4024 isolates), Staphylococcus aureus/oxacillin-methicillin (56.8% [56.1-57.4] of 23477 isolates), S. aureus/clindamycin (39.7% [39.1-40.4] of 21133 isolates), Pseudomonas aeruginosa/fluoroquinolones (32.6% [31.8-33.5] of 10982 isolates), and Escherichia coli/fluoroquinolones (31.3% [30.8-31.8] of 30715 isolates). The percentage resistant was 3.9% (3.2-4.9) for E. faecium/daptomycin (n = 2029 isolates). While these results are consistent with those from earlier studies in many respects, the percentage of E. faecium isolates resistant to daptomycin, while still small, is higher than has been reported to date.

Surveillance and management of multidrug-resistant microorganisms

Multidrug-resistant organisms are an established and growing worldwide public health problem and few therapeutic options remain available. The traditional antimicrobials (glycopeptides) for multidrug-resistant Gram-positive infections are declining in efficacy. New drugs that are presently available are linezolid, daptomicin and tigecycline, which have well-defined indications for severe infections, and talavancin, which is under Phase III trial for hospital-acquired pneumonia. Unfortunately the therapies available for multidrug-resistant Gram-negatives, including carbapenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae, are limited to only colistin and tigecycline. Both of these drugs are still not registered for severe infections, such as hospital acquired pneumonia. Consequently, as confirmed by scientific evidence, a multidisciplinary approach is needed. Surveillance, infection control procedures, isolation and antimicrobial stewardship should be implemented to reduce multidrug-resistant organism diffusion.

Trends in bacterial resistance in a tertiary university hospital over one decade

The objective of this study was to investigate bacterial resistance trends, infection sites and the relationship between resistance and admittance to the intensive care unit (ICU). A total of 53,316 bacteria identified between 1999 and 2008 were evaluated. Multidrug resistance was characterized when gram-negative bacilli (GNB) presented resistance to two or more classes of antibiotics. Gram-positive cocci (CPC) were assessed for resistance to penicillin, oxacillin and vancomycin. GNB were the most common (66.1%) isolate. There was a 3.7-fold overall increase in multidrug resistant GNB over the study period; Acinetobacter baumanii and Staphylococcus aureus were the most prevalent. Highest increases were recorded for Klebsiella pneumoniae (14.6-fold) and enterococci (73-fold). The resistance rates for GNB and GPC were 36% and 51.7%, respectively. Most multidrug resistant GNB and GPC were recovered from ICU patients (p-value < 0.001). Vancomycin-resistant enterococci were isolated during this decade with an increase of 18.7% by 2008. These data confirm the worldwide trend in multidrug bacterial resistance.

Etiology, extended-spectrum β-lactamase rates and antimicrobial susceptibility of gram-negative bacilli causing intra-abdominal infections in patients in general pediatric and pediatric intensive care units--global data from the Study for Monitoring Antimicrobial Resistance Trends 2008 to 2010

BACKGROUND

Antimicrobial resistance has been increasing for several years and is often higher in intensive care units (ICUs) than in other facilities. The spread of extended-spectrum β-lactamases (ESBLs) in particular has profoundly impacted antimicrobial efficacy and usage. The Study for Monitoring Antimicrobial Resistance Trends has monitored the in vitro activity of ertapenem and several comparators against aerobic gram-negative bacteria from intra-abdominal infections (IAIs) for many years. This report summarizes susceptibility levels and epidemiology for key IAI pathogens cultured from general pediatric medical wards and pediatric ICUs globally.

METHODS

1248 gram-negative bacteria were collected from pediatric IAIs by 113 labs in 40 countries from 2008 to 2010. Susceptibility was determined by Clinical and Laboratory Standards Institute broth microdilution. Susceptibility rates (%S) were determined for species with ≥10 isolates.

RESULTS

Sixty-two percent of isolates came from general pediatric wards and 38% from pediatric ICUs. The overall ESBL-positive rate was 11.0% for Escherichia coli and 38.9% for Klebsiella pneumoniae; the ESBL-positive rate for E. coli was twice as high in ICU as non-ICU. Most study drugs inhibited >90% of ESBL-negative isolates, but only the carbapenems inhibited >90% of ESBL-positive E. coli and only imipenem inhibited >90% of ESBL-positive K. pneumoniae.

CONCLUSIONS

Amikacin, imipenem and ertapenem were the most active against gram-negative bacteria from pediatric IAIs, followed closely by the fluoroquinolones and cefepime. Other cephalosporins were often <90% active. ESBL rates were 38.9% for K. pneumoniae and 11.0% for E. coli. Therapy for pediatric IAIs should take into consideration local ESBL rates because only carbapenems inhibited most of these pathogens.

Mortality in Emergency Department Sepsis score as a prognostic indicator in patients with pyogenic liver abscess

OBJECTIVES

The purpose of this study was to explore the predictor index of mortality in patients with pyogenic liver abscess (PLA).

METHODS

We performed a retrospective review that enrolled 431 patients 18 years and older hospitalized due to PLA between January 2005 and December 2010. Clinical characteristics, laboratory results, treatments, and outcomes retrieved from medical records were analyzed. Multiple logistic regression and receiver operating characteristic curve analyses were performed.

RESULTS

The mean age of the 431 patients identified with PLA was 56.9 ± 15.0 years. The mean Mortality in Emergency Department Sepsis (MEDS) score on admission was 4.8 ± 4.1 (range, 0-17). During hospitalization, 94 patients (22%) required intensive care. Of the 431 patients, 63 died, yielding a 15% case fatality rate. Multivariate analysis revealed that higher MEDS scores on admission (P < .0001) and the presence of underlying malignancy (P = .006), multiple abscesses (P = .001), anaerobic infections (P < .0001), hyperbilirubinemia (P < .0001), and higher serum creatinine levels (P < .0001) were significantly associated with PLA mortality. The estimated area under the receiver operating characteristic curve for MEDS in predicting PLA mortality was 0.829 (95% confidence interval, 0.791-0.864; P < .0001). The optimal cutoff MEDS value of 7 or higher had a sensitivity of 76% sensitivity and a specificity of 81%, with a 10.7-fold PLA mortality risk (P < .0001) and a 26.2-fold intensive care unit admission risk (P < .0001).

CONCLUSIONS

The MEDS scores on admission represent a significant prognostic indicator for patients with PLA.

Quantitative contributions of target alteration and decreased drug accumulation to Pseudomonas aeruginosa fluoroquinolone resistance

Quinolone antibiotics constitute a clinically successful and widely used class of broad-spectrum antibiotics; however, the emergence and spread of resistance increasingly limits the use of fluoroquinolones in the treatment and management of microbial disease. In this study, we evaluated the quantitative contributions of quinolone target alteration and efflux pump expression to fluoroquinolone resistance in Pseudomonas aeruginosa. We generated isogenic mutations in hot spots of the quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, and parC and inactivated the efflux regulator genes so as to overexpress the corresponding multidrug resistance (MDR) efflux pumps. We then introduced the respective mutations into the reference strain PA14 singly and in various combinations. Whereas the combined inactivation of two efflux regulator-encoding genes did not lead to resistance levels higher than those obtained by inactivation of only one efflux regulator-encoding gene, the combination of mutations leading to increased efflux and target alteration clearly exhibited an additive effect. This combination of target alteration and overexpression of efflux pumps was commonly observed in clinical P. aeruginosa isolates; however, these two mechanisms were frequently found not to be sufficient to explain the level of fluoroquinolone resistance. Our results suggest that there are additional mechanisms, independent of the expression of the MexAB-OprM, MexCD-OprJ, MexEF-OprN, and/or MexXY-OprM efflux pump, that increase ciprofloxacin resistance in isolates with mutations in the QRDRs.

Intercurrent infection predicts mortality in patients with late hepatic artery thrombosis listed for liver retransplantation

Liver retransplantation for late hepatic artery thrombosis (HAT) is considered the treatment of choice for select patients. Nevertheless, there is a paucity of data to aid decision making in this setting. The aims of this single-center study of patients listed for late HAT were (1) to determine variables associated with wait-list mortality, (2) to describe survival after retransplantation, and (3) to determine variables associated with mortality after retransplantation. Seventy-eight patients were diagnosed with late HAT (incidence = 3.9%). Of the 49 patients listed for retransplantation, 9 died on the waiting list and 36 were retransplanted. The estimated 1-year survival after listing for retransplantation was 53.7%. Only multidrug-resistant (MDR) bacteria-positive cultures were predictive of wait-list mortality (P = 0.01). After retransplantation, the estimated 1- and 5-year patient survival was 71.9% and 62.5%, respectively. Increasing Model for End-Stage Liver Disease score (overall P = 0.007), MDR bacteria-positive cultures (P = 0.047), and continued antibiotic therapy (P = 0.001) at the time of retransplantation were risk factors for post retransplant death. In conclusion, patients who undergo liver retransplantation for late HAT have satisfactory outcomes. However, the presence of active infection and MDR bacteria-positive cultures should be taken into account when risk stratifying such patients.

Comparison of antimicrobial resistance in neonatal and adult intensive care units in a tertiary teaching hospital

Intrahospital variations in antimicrobial profiles may be related to many factors. This study compared causative agents of nosocomial bloodstream infections between a neonatal intensive care unit (NICU) that adopted a ward-tailored antibiotic policy and adult intensive care units (ICUs). Data on organisms from blood cultures obtained from the respective wards between 2005 and 2009 were analyzed. Compared with the adult ICUs, the NICU had a higher frequency of Enterobacteriacae and lower frequencies of typical hospital-acquired pathogens (eg, Klebsiella pneumoniae, 17.4% vs 10.0% [P < .001]; Acinetobacter baumannii, 3.9% vs 11.6% [P < .001]). Antibiotic resistance of gram-negative organisms was also significantly lower in the NICU, including resistance to imipenem (5.7% vs 32.1%; P < .001), amikacin (8.8% vs 30.3%), and ceftriaxone (36.1% vs 74.6%; P < .001). This could possibly be due to the ward-tailored antibiotic policy adopted by the NICU but not by the other ICUs.

Management of antimicrobial use in the intensive care unit

Critically ill patients admitted to the intensive care unit (ICU) are frequently treated with antimicrobials. The appropriate and judicious use of antimicrobial treatment in the ICU setting is a constant clinical challenge for healthcare staff due to the appearance and spread of new multiresistant pathogens and the need to update knowledge of factors involved in the selection of multiresistance and in the patient's clinical response. In order to optimize the efficacy of empirical antibacterial treatments and to reduce the selection of multiresistant pathogens, different strategies have been advocated, including de-escalation therapy and pre-emptive therapy as well as measurement of pharmacokinetic and pharmacodynamic (pK/pD) parameters for proper dosing adjustment. Although the theoretical arguments of all these strategies are very attractive, evidence of their effectiveness is scarce. The identification of the concentration-dependent and time-dependent activity pattern of antimicrobials allow the classification of drugs into three groups, each group with its own pK/pD characteristics, which are the basis for the identification of new forms of administration of antimicrobials to optimize their efficacy (single dose, loading dose, continuous infusion) and to decrease toxicity. The appearance of new multiresistant pathogens, such as imipenem-resistant Pseudomonas aeruginosa and/or Acinetobacter baumannii, carbapenem-resistant Gram-negative bacteria harbouring carbapenemases, and vancomycin-resistant Enterococcus spp., has determined the use of new antibacterials, the reintroduction of other drugs that have been removed in the past due to toxicity or the use of combinations with in vitro synergy. Finally, pharmacoeconomic aspects should be considered for the choice of appropriate antimicrobials in the care of critically ill patients.

Bactericidal Activity of Methanol Extracts of Crabapple Mangrove Tree (Sonneratia caseolaris Linn.) Against Multi-Drug Resistant Pathogens

The crabapple mangrove tree, Sonneratia caseolaris Linn. (Family: Sonneratiaceae), is one of the foreshore plants found in estuarine and tidal creek areas and mangrove forests. Bark and fruit extracts from this plant have previously been shown to have an anti-oxidative or cytotoxic effect, whereas flower extracts of this plant exhibited an antimicrobial activity against some bacteria. According to the traditional folklore, it is medicinally used as an astringent and antiseptic. Hence, this investigation was carried out on the extract of the leaves, pneumatophore and different parts of the flower or fruit (stamen, calyx, meat of fruit, persistent calyx of fruit and seeds) for antibacterial activity using the broth microdilution method. The antibacterial activity was evaluated against five antibiotic-sensitive species (three Gram-positive and two Gram-negative bacteria) and six drug-resistant species (Gram-positive i.e. Methicillin-resistant Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium and Gram-negative i.e. Extended-spectrum beta-lactamase-Escherichia coli, multidrug-resistant-Pseudomonas aeruginosa and Acenetobacter baumannii). The methanol extracts from all tested parts of the crabapple mangrove tree exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria, but was mainly a bactericidal against the Gram-negative bacteria, including the multidrug-resistant strains, when compared with only bacteriostatic on the Gram-positive bacteria. Using Soxhlet apparatus, the extracts obtained by sequential extraction with hexane, dichloromethane and ethyl acetate revealed no discernable antibacterial activity and only slightly, if at all, reduced the antibacterial activity of the subsequently obtained methanol extract. Therefore, the active antibacterial compounds of the crabapple mangrove tree should have a rather polar structure.

High-dose, extended-interval colistin administration in critically ill patients: is this the right dosing strategy? A preliminary study

In critically ill patients with otherwise untreatable nosocomial infection due to gram-negative bacteria susceptible only to colistin, a high-dose, extended-interval colistin dosing regimen is, according to the pharmacokinetic/pharmacodynamic behavior of the drug, associated with low renal toxicity and high efficacy.

Background. Gram-negative bacteria susceptible only to colistin (COS) are emerging causes of severe nosocomial infections, reviving interest in the use of colistin. However, consensus on the most effective way to administer colistin has not yet been reached.

Methods. All patients who had sepsis due to COS gram-negative bacteria or minimally susceptible gram-negative bacteria and received intravenous colistimethate sodium (CMS) were prospectively enrolled. The CMS dosing schedule was based on a loading dose of 9 MU and a 9-MU twice-daily fractioned maintenance dose, titrated on renal function. For each CMS course, clinical cure, bacteriological clearance, daily serum creatinine clearance, and estimated creatinine clearance were recorded.

Results. Twenty-eight infectious episodes due to Acinetobacter baumannii (46.4%), Klebsiella pneumoniae (46.4%), and Pseudomonas aeruginosa (7.2%) were analyzed. The main types of infection were bloodstream infection (64.3%) and ventilator-associated pneumonia (35.7%). Clinical cure was observed in 23 cases (82.1%). Acute kidney injury developed during 5 treatment courses (17.8%), did not require renal replacement therapy, and subsided within 10 days from CMS discontinuation. No correlation was found between variation in serum creatinine level (from baseline to peak) and daily and cumulative doses of CMS, and between variation in serum creatinine level (from baseline to peak) and duration of CMS treatment.

Conclusions. Our study shows that in severe infections due to COS gram-negative bacteria, the high-dose, extended-interval CMS regimen has a high efficacy, without significant renal toxicity.

Infections caused by multidrug resistant organisms are not associated with overall, all-cause mortality in the surgical intensive care unit: the 20,000 foot view

BACKGROUND

Resistant pathogens are increasingly common in the ICU, with controversy regarding their relationship to outcomes. We hypothesized that an increasing number of infections with resistant pathogens in our surgical ICU would not be associated with increased overall mortality.

STUDY DESIGN

All ICU-acquired infections were prospectively identified between January 1, 2000 and December 31, 2009 in a single surgical ICU. Crude in-hospital, all-cause mortality data were obtained using a prospectively collected ICU database. Trends in rates were compared using linear regression.

RESULTS

A total of 799 resistant pathogens were identified (257 gram-positive, 542 gram-negative) from a total of 3,024 isolated pathogens associated with 2,439 ICU-acquired infections. The most frequently identified resistant gram-positive and -negative pathogens (defined as resistant to at least 1 major class of antimicrobials) were methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa, respectively. Pathogens were most commonly isolated from the lung, blood, and urine. The crude mortality rate declined steadily from 2000 to 2009 (9.4% to 5.4%; equation for trend y = -0.11x + 8.26). Linear regression analysis of quarterly rates revealed a significant divergence in trends between increasing total resistant infections (equation for trend y = 0.34x + 13.02) and percentage resistant infections (equation for trend y = 0.36x + 18.66) when compared with a decreasing mortality (p = 0.0003, p < 0.0001, respectively).

CONCLUSIONS

Despite a steady rise in the proportion of resistant bacterial infections in the ICU, crude mortality rates have decreased over time. The rates of resistant infections do not appear to be a significant factor in overall mortality in our surgical ICU patients.

Combination antibiotic therapy for empiric and definitive treatment of gram-negative infections: insights from the Society of Infectious Diseases Pharmacists

The widespread emergence of antibiotic-resistant gram-negative organisms has compromised the utility of current treatment options for severe infections caused by these pathogens. The rate of gram-negative multidrug resistance is worsening, threatening the effectiveness of newer broad-spectrum antibiotic agents. Infections associated with multidrug-resistant Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacteriaceae are having a substantial impact on hospital costs and mortality rates. The potential for these resistant gram-negative nosocomial pathogens must always be a primary consideration when selecting antibiotic therapy for critically ill patients. Empiric combination therapy directed at gram-negative pathogens is a logical approach for patients with suspected health care-associated infections, particularly those with risk factors for infections caused by multidrug-resistant pathogens. Although in vitro synergy tests have shown potential benefits of continued combination therapy, convincing clinical data that demonstrate a need for combination therapy once susceptibilities are known are lacking. Thus, deescalation to a single agent once susceptibilities are known is recommended for most patients and pathogens. Use of polymyxins, often in combination with other antimicrobials, may be necessary for salvage therapy.

Point prevalence survey of antibiotic use in French hospitals in 2009

OBJECTIVES

To evaluate the feasibility of a point prevalence survey for monitoring antibiotic use in a voluntary sample of French hospitals.

METHODS

Demographic and medical data were collected for all inpatients. Additional characteristics regarding antimicrobial treatment, type of infection and microbiological results were collected only for patients receiving antimicrobials.

RESULTS

Among 3964 patients in 38 hospitals, 343 (8.7%) received antimicrobial prophylaxis and 1276 (32.2%) antimicrobial therapy. The duration of surgical antimicrobial prophylaxis was >1 day in 41 out of 200 (21%) of the cases. Among patients with antimicrobial therapy, 959 (75.2%) received β-lactams (including 34.8% penicillins with β-lactam inhibitors, 22.1% third-generation cephalosporins and 7.8% carbapenems) and 301 (23.6%) received fluoroquinolones (50% orally). A total of 518 (40.6%) patients were treated with more than one drug and 345 (27.2%) were treated for >7 days. Patients treated for hospital-acquired infections (39.2%) were more likely to receive combinations (47.6% versus 34.4%, P < 0.01), carbapenems (14.4% versus 2.6%, P < 0.01), glycopeptides (14.4% versus 3.7%, P < 0.01) and antifungals (17% versus 5.3%, P < 0.01) for a longer duration (7.8 versus 6 days, P < 0.01). Fifty-six patients (4.4%) were treated for >7 days and did not have any microbiological sample drawn. The time allocated for the survey represented 18.3-25.0 h for 100 patients.

CONCLUSIONS

The data provide directions for further interventions, such as better use of diagnostic tools, decreasing the treatment duration and the use of combinations. In addition, the survey shows that, although cumbersome, it is feasible to improve the representativeness of national data in European surveys.

Empiric antibiotic selection strategies for healthcare-associated pneumonia, intra-abdominal infections, and catheter-associated bacteremia

Initial selection and early deployment of appropriate/adequate empiric antimicrobial therapy is critical to minimize the significant morbidity and mortality associated with hospital- or healthcare-associated infections (HAIs). Initial empiric therapy that inadequately covers the pathogen(s) causing a serious HAI has been associated with increased mortality, longer hospital stay, and elevated healthcare costs. Moreover, subsequent modification of initial inadequate therapy, later in the disease process when culture results become available, may not remedy the impact of the initial choice. Because of this, it is important that initial empiric therapy covers the most likely pathogens associated with infection in a particular patient, even if this initial regimen turns out to be unnecessarily broad, based on subsequent culture results. The current paradigm for management of serious HAIs is to initiate empiric therapy with a broad-spectrum regimen covering likely pathogens, based on local surveillance and susceptibility data, and presence of risk factors for involvement of a resistant microorganism. Subsequent modification (de-escalation) of the initial regimen becomes possible later, when culture results are available and clinical status can be better assessed, 2 to 4 days after initiation of empiric therapy. When possible, de-escalation and other steps to modify antimicrobial exposure are important for minimizing risk of antimicrobial resistance development. This article examines the general process for selection of initial empiric antibiotic therapy for patients with HAIs, illustrated through 3 case studies dealing with healthcare-associated pneumonia, complicated intra-abdominal infection, and catheter-associated bacteremia, respectively.

Preventing the spread of multidrug-resistant gram-negative pathogens: recommendations of an expert panel of the German Society For Hygiene and Microbiology

BACKGROUND

Infections with multidrug-resistant gram-negative bacteria are hard to treat and cause high morbidity and mortality. The direct transmission of such pathogens is well documented, and measures to protect other patients would seem indicated. Nonetheless, evidence-based recommendations are not yet available because of insufficient data from clinical trials.

METHODS

An expert panel was convened by two sections of the German Society for Hygiene and Microbiology (the permanent committee on general and hospital hygiene and the special committee on infection prevention and antibiotic resistance in hospitals) to review existing data on the epidemiology and diagnostic evaluation of multidrug-resistant gram-negative pathogens. The panel carried out a selective review of the relevant literature, with special attention to national guidelines.

RESULTS AND CONCLUSION

In this paper, the expert panel presents a definition of multidrug-resistant gram-negative pathogens and recommends measures for presenting the spread of infection from colonized and infected patients in non-outbreak situations. These measures depend on the risk profile of the clinical setting. They are mostly to be considered "expert opinion," rather than "evidence-based."

Antibiotic exposure and resistance development in Pseudomonas aeruginosa and Enterobacter species in intensive care units

OBJECTIVES

We quantified the association between antibiotic exposure and acquisition of antibiotic resistance in Pseudomonas aeruginosa and Enterobacter species in intensive care unit patients.

DESIGN

Prospective cohort study.

SETTING AND PATIENTS

In 1,201 patients, respiratory tract colonization was determined through regular screening on admission, twice weekly, and on discharge. Primary outcome was the acquisition of antibiotic resistance in previous antibiotic sensitive P. aeruginosa and Enterobacter species, with acquisition attributable to cross-transmission excluded based on genotyping and epidemiologic linkage. Cox regression analysis, adjusted for covariates, was performed to calculate hazard ratios of patients exposed to antibiotics compared to patients not exposed to antibiotics.

MEASUREMENTS AND MAIN RESULTS

In total, 194 and 171 patients were colonized with P. aeruginosa and Enterobacter species, respectively. Two or more cultures per episode were available for 126 and 108 patients. For P. aeruginosa, ceftazidime exposure was associated with 6.3 acquired antibiotic resistance events per 100 days of exposure, whereas incidence rates were lower for ciprofloxacin, meropenem, and piperacillin-tazobactam. In multivariate analysis, meropenem, ciprofloxacin, and ceftazidime were significantly associated with risk of resistance development in P. aeruginosa (adjusted hazard ratio, 11.1; 95% confidence interval, 2.4-51.5 for meropenem; adjusted hazard ratio, 4.1; 95% confidence interval, 1.1-16.2 for ciprofloxacin; adjusted hazard ratio, 2.5; 95% confidence interval, 1.1-5.5 for ceftazidime). For Enterobacter, ceftriaxone and ciprofloxacin exposure were associated with most antibiotic resistance acquisitions. No significant associations were found in multivariate analysis.

CONCLUSIONS

Meropenem exposure is associated with the highest risk of resistance development in P. aeruginosa. Increasing carbapenem use attributable to emergence of Gram-negative bacteria producing extended-spectrum β-lactamases will enhance antibiotic resistance in P. aeruginosa.

Appropriate antibiotic dosage levels in the treatment of severe sepsis and septic shock

Antibiotic treatment of critically ill patients remains a significant challenge. Optimal antibacterial strategy should achieve therapeutic drug concentration in the blood as well as the infected site. Achieving therapeutic drug concentrations is particularly difficult when infections are caused by some pathogens, such as Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative rods, because of their low susceptibility to antimicrobials. In sepsis, pharmacokinetics (PKs) of antibiotics are profoundly altered and may result in inadequate drug concentrations, even when recommended regimens are used, which potentially contribute to increased mortality and spread of resistance. The wide inter-individual PK variability observed in septic patients strongly limits the a priori prediction of the optimal dose that should be administered. Higher than standard dosages are necessary for the drugs, such as β-lactams, aminoglycosides, and glycopeptides, that are commonly used as first-line therapy in these patients to maximize their antibacterial activity. However, the benefit of reaching adequate drug concentrations on clinical outcome needs to be further determined.

Traffic jam at the bacterial sec translocase: targeting the SecA nanomotor by small-molecule inhibitors

The rapid rise of drug-resistant bacteria is one of the most serious unmet medical needs facing the world. Despite this increasing problem of antibiotic resistance, the number of different antibiotics available for the treatment of serious infections is dwindling. Therefore, there is an urgent need for new antibacterial drugs, preferably with novel modes of action to potentially avoid cross-resistance with existing antibacterial agents. In recent years, increasing attention has been paid to bacterial protein secretion as a potential antibacterial target. Among the different protein secretion pathways that are present in bacterial pathogens, the general protein secretory (Sec) pathway is widely considered as an attractive target for antibacterial therapy. One of the key components of the Sec pathway is the peripheral membrane ATPase SecA, which provides the energy for the translocation of preproteins across the bacterial cytoplasmic membrane. In this review, we will provide an overview of research efforts on the discovery and development of small-molecule SecA inhibitors. Furthermore, recent advances on the structure and function of SecA and their potential impact on antibacterial drug discovery will be discussed.

Does duration of perioperative antibiotic prophylaxis matter in cardiac surgery? A systematic review and meta-analysis

OBJECTIVE

We aimed to compare the efficacy of short-term (<24 hours) versus longer-term antibiotic prophylaxis (≥24 hours) in open heart surgery.

BACKGROUND

The optimal duration of antibiotic prophylaxis for adults undergoing cardiac surgery is unknown and guideline recommendations are inconsistent.

METHODS

We searched MEDLINE, EMBASE, CINAHL, and CENTRAL for parallel-group randomized trials comparing any antibiotic prophylaxis administered for <24 hours to any antibiotic prophylaxis for ≥24 hours in adult patients undergoing open heart surgery. Reference lists of selected articles, clinical practice guidelines, review articles, and congress abstracts were searched. Study selection, data extraction and assessment of risk of bias were performed independently by 2 reviewers.

RESULTS

Of the 1338 citations identified by our search strategy, 12 studies involving 7893 patients were selected. Compared with short-term antibiotic prophylaxis, longer-term antibiotic prophylaxis reduced the risk of sternal surgical site infection (SSI) by 38% (risk ratio 1.38, 95% confidence interval (CI) 1.13-1.69, P = 0.002) and deep sternal SSI by 68% (risk ratio 1.68, 95% CI 1.12-2.53, P = 0.01). There were no statistically significant differences in mortality, infections overall and adverse events. Eleven of the trials were at high risk for bias due to limitations in study design.

CONCLUSIONS

Perioperative antibiotic prophylaxis of ≥24 hours may be more efficacious in preventing sternal SSIs in patients undergoing cardiac surgery compared to shorter regimens. The findings however are limited by the heterogeneity of antibiotic regimens used and the risk of bias in the published studies.

Pseudomonas aeruginosa: resistance to the max

Pseudomonas aeruginosa is intrinsically resistant to a variety of antimicrobials and can develop resistance during anti-pseudomonal chemotherapy both of which compromise treatment of infections caused by this organism. Resistance to multiple classes of antimicrobials (multidrug resistance) in particular is increasingly common in P. aeruginosa, with a number of reports of pan-resistant isolates treatable with a single agent, colistin. Acquired resistance in this organism is multifactorial and attributable to chromosomal mutations and the acquisition of resistance genes via horizontal gene transfer. Mutational changes impacting resistance include upregulation of multidrug efflux systems to promote antimicrobial expulsion, derepression of ampC, AmpC alterations that expand the enzyme's substrate specificity (i.e., extended-spectrum AmpC), alterations to outer membrane permeability to limit antimicrobial entry and alterations to antimicrobial targets. Acquired mechanisms contributing to resistance in P. aeruginosa include β-lactamases, notably the extended-spectrum β-lactamases and the carbapenemases that hydrolyze most β-lactams, aminoglycoside-modifying enzymes, and 16S rRNA methylases that provide high-level pan-aminoglycoside resistance. The organism's propensity to grow in vivo as antimicrobial-tolerant biofilms and the occurrence of hypermutator strains that yield antimicrobial resistant mutants at higher frequency also compromise anti-pseudomonal chemotherapy. With limited therapeutic options and increasing resistance will the untreatable P. aeruginosa infection soon be upon us?

Recommended β-lactam regimens are inadequate in septic patients treated with continuous renal replacement therapy

Introduction

Sepsis is responsible for important alterations in the pharmacokinetics of antibiotics. Continuous renal replacement therapy (CRRT), which is commonly used in septic patients, may further contribute to pharmacokinetic changes. Current recommendations for antibiotic doses during CRRT combine data obtained from heterogeneous patient populations in which different CRRT devices and techniques have been used. We studied whether these recommendations met optimal pharmacokinetic criteria for broad-spectrum antibiotic levels in septic shock patients undergoing CRRT.

Methods

This open, prospective study enrolled consecutive patients treated with CRRT and receiving either meropenem (MEM), piperacillin-tazobactam (TZP), cefepime (FEP) or ceftazidime (CAZ). Serum concentrations of these antibiotics were determined by high-performance liquid chromatography from samples taken before (t = 0) and 1, 2, 5, and 6 or 12 hours (depending on the β-lactam regimen) after the administration of each antibiotic. Series of measurements were separated into those taken during the early phase (< 48 hours from the first dose) of therapy and those taken later (> 48 hours).

Results

A total of 69 series of serum samples were obtained in 53 patients (MEM, n = 17; TZP, n = 16; FEP, n = 8; CAZ, n = 12). Serum concentrations remained above four times the minimal inhibitory concentration for Pseudomonas spp. for the recommended time in 81% of patients treated with MEM, in 71% with TZP, in 53% with CAZ and in 0% with FEP. Accumulation after 48 hours of treatment was significant only for MEM.

Conclusions

In septic patients receiving CRRT, recommended doses of β-lactams for Pseudomonas aeruginosa are adequate for MEM but not for TZP, FEP and CAZ; for these latter drugs, higher doses and/or extended infusions should be used to optimise serum concentrations.

Pseudomonas aeruginosa: resistance to the max

Pseudomonas aeruginosa is intrinsically resistant to a variety of antimicrobials and can develop resistance during anti-pseudomonal chemotherapy both of which compromise treatment of infections caused by this organism. Resistance to multiple classes of antimicrobials (multidrug resistance) in particular is increasingly common in P. aeruginosa, with a number of reports of pan-resistant isolates treatable with a single agent, colistin. Acquired resistance in this organism is multifactorial and attributable to chromosomal mutations and the acquisition of resistance genes via horizontal gene transfer. Mutational changes impacting resistance include upregulation of multidrug efflux systems to promote antimicrobial expulsion, derepression of ampC, AmpC alterations that expand the enzyme's substrate specificity (i.e., extended-spectrum AmpC), alterations to outer membrane permeability to limit antimicrobial entry and alterations to antimicrobial targets. Acquired mechanisms contributing to resistance in P. aeruginosa include β-lactamases, notably the extended-spectrum β-lactamases and the carbapenemases that hydrolyze most β-lactams, aminoglycoside-modifying enzymes, and 16S rRNA methylases that provide high-level pan-aminoglycoside resistance. The organism's propensity to grow in vivo as antimicrobial-tolerant biofilms and the occurrence of hypermutator strains that yield antimicrobial resistant mutants at higher frequency also compromise anti-pseudomonal chemotherapy. With limited therapeutic options and increasing resistance will the untreatable P. aeruginosa infection soon be upon us?