The relationship between antimicrobial resistance and patient outcomes: mortality, length of hospital stay, and health care costs

Prevention and treatment of health care-acquired infections

Health care-acquired infections present a tremendous challenge to the care of hospitalized patients. Unfortunately, the risk of acquiring a health care-associated infection (HAI) is rising. The vast majority of HAI are of four types: urinary tract infections, surgical site infections, bloodstream infections, and pneumonia. This chapter aims to provide current data and strategies relating to the prevention of HAIs among hospitalized patients.

Evaluation of an antimicrobial stewardship program at a pediatric teaching hospital

BACKGROUND

Thirty to 50% of hospitalized patients receive antimicrobial therapy. Previous data suggest that inappropriate use results in higher mortality rates, longer lengths of stay, and increased medical costs. Antimicrobial Stewardship Programs (ASPs) reduce the improper use of antimicrobials and improve patient safety. Despite increased awareness about the benefits of these programs, few pediatric ASPs exist and fewer comprehensive studies evaluate their effects.

METHODS

A prospective observational study was conducted to describe the use and impact of a pediatric ASP. Data were collected on the clinician's request for targeted antibiotics and the interventions made by the ASP. Retrospective chart review was performed to assess outcomes and compliance on empiric antimicrobial therapy decisions and recommendations to discontinue antimicrobial therapy.

RESULTS

During the 4-month study period, calls were placed to the ASP for 652 patients. Forty-five percent of those calls required an intervention by the ASP. These interventions included: (1) Targeting the known or suspected pathogens (20%); (2) Consultation (43%); (3) Optimize antimicrobial treatment (33%); and (4) Stop antimicrobial treatment (4%). Three of the 84 (3.5%) patients recommended to receive alternative therapy developed an infection not covered by the ASP recommendations or the antimicrobial initially requested by the clinician.

CONCLUSIONS

Our data demonstrate that an ASP improves the appropriate use of antimicrobial medications in hospitalized children. In addition, the ASP plays an integral role in providing guidance to clinicians and ensures that the appropriate antimicrobial agents are used.

Antimicrobial-resistant pathogens: an emerging pediatric threat

The clinical impact of these three bacterial threats is readily apparent to any who practice pediatrics. The potential virulence of CA-MRSA and MDR pneumococci and the threat of failed antimicrobial options for MDRGN pose enormous challenges now and in the near future. With careful attention to antimicrobial stewardship, however, and knowledge of the clinical and epidemiologic factors of these organisms, one can hope to mitigate the impact on patient care and outcomes while awaiting ongoing discovery of new antimicrobial options. Most important, however, will be careful and thoughtful management of any new antimicrobial products to protect their efficacy for the future.

Effect of communication errors during calls to an antimicrobial stewardship program

OBJECTIVE

To determine how inaccurate communication of patient data by clinicians in telephone calls to the prior-approval antimicrobial stewardship program (ASP) staff affects the incidence of inappropriate antimicrobial recommendations made by ASP practitioners.

DESIGN

A retrospective cohort design was used. The accuracy of the patient data communicated was evaluated against patients' medical records to identify predetermined, clinically significant inaccuracies. Inappropriate antimicrobial recommendations were defined having been made if an expert panel unanimously rated the actual recommendations as inappropriate after reviewing vignettes derived from inpatients' medical records.

SETTING

The setting was an academic medical center with a prior-approval ASP.

PATIENTS

All inpatient subjects of ASP prior-approval calls were eligible for inclusion.

RESULTS

Of 200 ASP telephone calls, the panel agreed about whether or not antimicrobial recommendations were inappropriate for 163 calls (82%); these 163 calls were then used as the basis for further analyses. After controlling for confounders, inaccurate communication was found to be associated with inappropriate antimicrobial recommendations (odds ratio [OR], of 2.2; P=.03). In secondary analyses of specific data types, only inaccuracies in microbiological data were associated with the study outcome (OR, 7.5; P=.002). The most common reason panelists gave for rating a recommendation as inappropriate was that antimicrobial therapy was not indicated.

CONCLUSIONS

Inaccurate communication of patient data, particularly microbiological data, during prior-approval calls is associated with an increased risk of inappropriate antimicrobial recommendations from the ASP. Clinicians and ASP practitioners should work to confirm that critical data has been communicated accurately prior to use of that data in prescribing decisions.

Clinical and molecular epidemiology of community-onset, extended-spectrum beta-lactamase-producing Escherichia coli infections in Thailand: a case-case-control study

BACKGROUND

Extended-spectrum beta-lactamase (ESBL)-producing organisms, first identified in Germany in 1983, are now widely recognized as clinically relevant causes of infections in community.

METHODS

Our objective was to evaluate the clinical and molecular epidemiology of community-onset, extended-spectrum beta-lactamase (CO-ESBL)-producing Escherichia coli infections. We used a case-case-control study undertaken in a 450-bed, tertiary care hospital. Patients included case group (CG) I, which had confirmed CO-ESBL-producing E coli infections (n=46). Case group (CG) II (n=46) included patients with CO-non-ESBL-producing E coli infections. Controls (n=138) were patients without infections.

RESULTS

By multivariate analysis, diabetes (95% confidence interval [CI]: 1.9-13.2, P< .001), prior ESBL E coli colonization (<90 days) (95% CI: 1.2-67.8, P< .001), recent receipt of antibiotics (<90 days) (95% CI: 4.2-44.2, P= .004), and previous exposure to third-generation cephalosporins (95% CI: 2.2-16.4, P= .001) and fluoroquinolones (95% CI: 1.4-18.3; P= .003) were associated risks among CG I. Diabetes (95% CI: 1.6-15.4, P= .005), stroke (95% CI: 1.5-17.1, P= .001), and diarrhea (95% CI: 3.8-65.8, P= .001) were risks among CG II. Patients with CO-ESBL in CG I versus controls were more likely to die (30% vs 0%, respectively; P< .001), had prolonged hospital length of stay (8 vs 5 days, respectively; P< .001), and had higher hospitalization costs (median, US $528 vs $108, respectively; P< .001). The plasmid carrying the CTX-M-15 gene was identified in 13 of 25 (52%) available CO-ESBL-producing E coli isolates.

CONCLUSION

CO-ESBL-producing E coli is an emerging multidrug-resistant microorganism in Thailand. Patients with prior ESBL colonization and recent antibiotic exposures, especially to third-generation cephalosporins and fluoroquinolones, were at risk for CO-ESBL-producing E coli infection.

Physicians' perceptions, beliefs, attitudes, and knowledge concerning antimicrobial resistance in a Brazilian teaching hospital

This cross-sectional survey assessed physicians' perceptions, knowledge and practices concerning antimicrobial resistance. Ninety-nine percent of participants reported that they perceived antimicrobial resistance as an important problem, and 86.7% agreed that antimicrobials are overprescribed, but only 2.9% rated "practicing antimicrobial control" as the most important strategy for preventing resistance. The results of this study warrant educational programs on antimicrobial resistance and the distribution of information regarding local antimicrobial susceptibility testing.

Increasing prevalence of gastrointestinal colonization with ceftazidime-resistant gram-negative bacteria among intensive care unit patients

BACKGROUND

The occurrence of nosocomial infections due to third-generation cephalosporin-resistant gram-negative bacteria is increasing. Gastrointestinal colonization is an important reservoir for antibiotic-resistant bacteria, and it often precedes clinical infection.

OBJECTIVE

To estimate the prevalence of gastrointestinal colonization with ceftazidime-resistant gram-negative bacteria among intensive care unit (ICU) patients at a university-affiliated tertiary-care hospital during 2 distinct periods and to assess whether, at any time during the index hospitalization, colonized patients had a clinical culture positive for the same organism that was recovered from surveillance culture.

SETTING

Two ICUs at the University of Maryland Medical Center, a 656-bed tertiary-care hospital located in Baltimore, Maryland. Both ICUs provide care to adult patients.

METHODS

We performed a cross-sectional study of adult patients admitted to the medical ICU or the surgical ICU from June 14 to July 14, 2003, and from June 14 to July 14, 2006. Perirectal swab samples were obtained for surveillance culture on admission to the intensive care unit, weekly thereafter, and at discharge. Each culture sample was plated onto MacConkey agar supplemented with ceftazidime.

RESULTS

In 2003, a total of 33 (18.8%) of 176 patients were colonized with ceftazidime-resistant gram-negative bacilli; in 2006, 60 (31.4%) of 191 patients were (P<.01). This increase was largely driven by an increase in ceftazidime-resistant Klebsiella isolates (which accounted for 6.4% of isolates in 2003 and for 22.8% in 2006; P<.01). In 2003, a total of 16 (48.5%) of 33 colonized patients had a clinical culture positive for the same organism that was recovered from the perirectal surveillance culture, compared with 22 (36.6%) of 60 colonized patients in 2006 (P=.28).

CONCLUSION

Our data suggest that gastrointestinal colonization with ceftazidime-resistant gram-negative bacilli is common, that its prevalence is increasing, and that colonization may result in clinical cultures positive for these bacilli.

Perioperative Management of Multidrug-Resistant Organisms in Health Care Settings

Guidelines for managing multidrug-resistant organisms (MDROs) in health care settings were published by the Healthcare Infection Control Practices Advisory Committee (HICPAC) in October 2006. These guidelines outline appropriate strategies to help prevent MDRO cross transmission. Perioperative nurses should be prepared to implement these strategies in an effort to protect their surgical patients from contracting MDRO infections. The HICPAC recommends elevating contact precautions to "intensified interventions" in facilities with endemic outbreaks of MDROs. Perioperative nurses should participate in these efforts by adhering to infection control practices, championing these practices with other health care personnel, and providing clinical support and leadership.

‘My five moments for hand hygiene’: a user-centred design approach to understand, train, monitor and report hand hygiene

Hand hygiene is a core element of patient safety for the prevention of healthcare-associated infections and the spread of antimicrobial resistance. Its promotion represents a challenge that requires a multi-modal strategy using a clear, robust and simple conceptual framework. The World Health Organization First Global Patient Safety Challenge 'Clean Care is Safer Care' has expanded educational and promotional tools developed initially for the Swiss national hand hygiene campaign for worldwide use. Development methodology involved a user-centred design approach incorporating strategies of human factors engineering, cognitive behaviour science and elements of social marketing, followed by an iterative prototype test phase within the target population. This research resulted in a concept called 'My five moments for hand hygiene'. It describes the fundamental reference points for healthcare workers (HCWs) in a time-space framework and designates the moments when hand hygiene is required to effectively interrupt microbial transmission during the care sequence. The concept applies to a wide range of patient care activities and healthcare settings. It proposes a unified vision for trainers, observers and HCWs that should facilitate education, minimize inter-individual variation and resource use, and increase adherence. 'My five moments for hand hygiene' bridges the gap between scientific evidence and daily health practice and provides a solid basis to understand, teach, monitor and report hand hygiene practices.

Antimicrobial resistance among Gram-negative bacilli causing infections in intensive care unit patients in the United States between 1993 and 2004

During the 12-year period from 1993 to 2004, antimicrobial susceptibility profiles of 74,394 gram-negative bacillus isolates recovered from intensive care unit (ICU) patients in United States hospitals were determined by participating hospitals and collected in a central location. MICs for 12 different agents were determined using a standardized broth microdilution method. The 11 organisms most frequently isolated were Pseudomonas aeruginosa (22.2%), Escherichia coli (18.8%), Klebsiella pneumoniae (14.2%), Enterobacter cloacae (9.1%), Acinetobacter spp. (6.2%), Serratia marcescens (5.5%), Enterobacter aerogenes (4.4%), Stenotrophomonas maltophilia (4.3%), Proteus mirabilis (4.0%), Klebsiella oxytoca (2.7%), and Citrobacter freundii (2.0%). Specimen sources included the lower respiratory tract (52.1%), urine (17.3%), and blood (14.2%). Rates of resistance to many of the antibiotics tested remained stable during the 12-year study period. Carbapenems were the most active drugs tested against most of the bacterial species. E. coli and P. mirabilis remained susceptible to most of the drugs tested. Mean rates of resistance to 9 of the 12 drugs tested increased with Acinetobacter spp. Rates of resistance to ciprofloxacin increased over the study period for most species. Ceftazidime was the only agent to which a number of species (Acinetobacter spp., C. freundii, E. aerogenes, K. pneumoniae, P. aeruginosa, and S. marcescens) became more susceptible. The prevalence of multidrug resistance, defined as resistance to at least one extended-spectrum cephalosporin, one aminoglycoside, and ciprofloxacin, increased substantially among ICU isolates of Acinetobacter spp., P. aeruginosa, K. pneumoniae, and E. cloacae.

Comparison of the BD GeneOhm VanR assay to culture for identification of vancomycin-resistant enterococci in rectal and stool specimens

Active screening for vancomycin-resistant enterococci (VRE) in rectal and stool specimens has been recommended to limit the spread of antimicrobial resistance within certain high-risk populations. Directly from 502 rectal swabs and stool specimens, we evaluated the diagnostic performance of the BD GeneOhm VanR assay (BD GeneOhm, San Diego, CA), a rapid real-time PCR test that detects the presence of vanA and/or vanB genes. The VanR assay was compared to culture consisting of both bile-esculin-azide agar with 6 mug/ml vancomycin (BEAV agar) (BD Diagnostics, Sparks, MD) and BEAV broth with 8 mug/ml vancomycin (Hardy Diagnostics, Santa Maria, CA). Enterococci were identified to the species level using standard biochemical tests and a Phoenix automated microbiology system (BD Diagnostics, Sparks, MD). The susceptibility of the enterococci to vancomycin and teicoplanin was determined using an Etest (AB Biodisk, Solna, Sweden). VRE were initially isolated from 147 cultures, and the VanR assay detected 142 of the 147 positive cultures for a sensitivity of 96.6%. The specificity was 87.0% (309/355) largely due to false positives seen with the vanB portion of the assay. The sensitivity when testing rectal swabs was 98.3%, and the sensitivity for stool samples was 95.4% (P = 0.643). The specificity of rectal swabs was comparable to that of the stool specimens (87.5% and 86.5%, respectively). When used only to detect VanA resistance, the VanR assay was 94.4% (136/144) sensitive and 96.4% (345/358) specific, with positive and negative predictive values of 91.3% and 97.7%, respectively. In summary, the BD GeneOhm VanR assay is a good screening test for VRE in our population of predominantly vanA-colonized patients. However, patient samples testing only vanB positive should be confirmed by another method for the presence of VRE.

Antimicrobial susceptibility among Acinetobacter calcoaceticus-baumannii complex and Enterobacteriaceae collected as part of the Tigecycline Evaluation and Surveillance Trial

OBJECTIVE

To measure the in vitro activity of a panel of antimicrobial agents against gram-negative pathogens collected from the nine census regions of the USA.

METHODS

Isolates were collected from 76 centers between January 2004 and September 2005. In vitro activity was assessed using CLSI guidelines and CLSI or FDA interpretive criteria.

RESULTS

The lowest overall antimicrobial susceptibilities for Acinetobacter calcoaceticus-baumannii complex isolates (n=851) were detected in the Middle Atlantic and East South Central regions. Overall, 29.3% of A. calcoaceticus-baumannii complex isolates were multidrug-resistant (resistant to > or =3 antimicrobial classes). Tigecycline (2 microg/mL) had the lowest MIC90 against this organism. Imipenem, tigecycline, and levofloxacin had low MIC90s (0.25-4 microg/mL) against Enterobacter spp. (n=1557), although the MIC90 for levofloxacin was elevated for East South Central region isolates (> or = 16 microg/mL). Susceptibility to levofloxacin among the E. coli isolates (n=1785) ranged from 71.7% (Pacific) to 88.5% (New England). The prevalence of ESBL-producing K. pneumoniae (126/1460) varied from 1.7% of isolates (Pacific) to 21.2% (Middle Atlantic). ESBL-producing K. pneumoniae MICs were lowest for imipenem and tigecycline.

CONCLUSIONS

Antimicrobial susceptibility varies among the census regions of the USA. The broad-spectrum in vitro activity of tigecycline may make it a suitable candidate for use in the empiric treatment of serious infections.

Redesigning β-lactams to combat resistance: summary and conclusions

The relentless emergence and spread of antimicrobial resistance warrant an increased awareness of the problem and improved coordination and standardisation of surveillance systems, as well as resistance control strategies. Moreover, this underscores the urgent need for new antibiotics active against the emerging resistant pathogens. Ceftobiprole is a new beta-lactam molecule engineered for bactericidal activity against methicillin-resistant staphylococci that also exhibits an extended broad spectrum of activity covering the most clinically important Gram-positive (methicillin-susceptible staphylococci, penicillin-susceptible and -resistant pneumococci, other streptococci and ampicillin-susceptible enterococci) and Gram-negative (Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter spp., Haemophilus spp. and Moraxella spp.) pathogens. Results from studies with experimental infections and from clinical trials support a role for ceftobiprole in treating complicated skin and skin structure infections caused by Gram-positive pathogens, including methicillin-resistant staphylococci, and suggest a potential role for this drug in treating other types of serious infection caused by Gram-positive and Gram-negative pathogens.

Clinical validation of the molecular BD GeneOhm StaphSR assay for direct detection of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus in positive blood cultures

The rapid detection of Staphylococcus aureus bacteremia and a swift determination of methicillin susceptibility has serious clinical implications affecting patient mortality. This study evaluated the StaphSR assay (BD GeneOhm, San Diego, CA), a real-time PCR assay, for the identification and differentiation of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) from 300 positive blood cultures. The BD GeneOhm StaphSR assay was performed and interpreted according to the manufacturer's recommendations. Positive blood cultures (containing predominantly gram-positive cocci in clusters) were subcultured on 5% sheep blood agar plates. After 18 to 24 h of incubation, isolates morphologically consistent with S. aureus were presumptively identified by latex agglutination (Staphaurex Plus; Remel, Lenexa, KS). Susceptibility testing was initially performed with the Phoenix automated microbiology system (BD Diagnostics, Sparks, MD). Additional susceptibility testing of samples with discrepant results was done using BBL oxacillin screen agar (BD Diagnostics, Sparks, MD), oxacillin and cefoxitin Etests (AB Biodisk, Solna, Sweden) on Mueller-Hinton agar, an immunoassay for penicillin binding protein 2' (Denka Seiken Co., Tokyo, Japan), and mecA PCR. The sensitivity, specificity, and positive and negative predictive values of the BD GeneOhm StaphSR assay for MSSA detection were 98.9, 96.7, 93.6, and 99.5%, respectively. For the detection of MRSA, the BD GeneOhm StaphSR assay was 100% sensitive and 98.4% specific; positive and negative predictive values for MRSA detection were 92.6 and 100%, respectively. Inhibition was seen with only one sample, and the issue was resolved upon retesting. The BD GeneOhm StaphSR assay appears to be a valuable diagnostic tool for quickly differentiating bacteremia caused by MSSA and MRSA from that caused by other gram-positive cocci.

Antimicrobial resistance predicts death in Tanzanian children with bloodstream infections: a prospective cohort study

Background

Bloodstream infection is a common cause of hospitalization, morbidity and death in children. The impact of antimicrobial resistance and HIV infection on outcome is not firmly established.

Methods

We assessed the incidence of bloodstream infection and risk factors for fatal outcome in a prospective cohort study of 1828 consecutive admissions of children aged zero to seven years with signs of systemic infection. Blood was obtained for culture, malaria microscopy, HIV antibody test and, when necessary, HIV PCR. We recorded data on clinical features, underlying diseases, antimicrobial drug use and patients' outcome.

Results

The incidence of laboratory-confirmed bloodstream infection was 13.9% (255/1828) of admissions, despite two thirds of the study population having received antimicrobial therapy prior to blood culture. The most frequent isolates were klebsiella, salmonellae, Escherichia coli, enterococci and Staphylococcus aureus. Furthermore, 21.6% had malaria and 16.8% HIV infection. One third (34.9%) of the children with laboratory-confirmed bloodstream infection died. The mortality rate from Gram-negative bloodstream infection (43.5%) was more than double that of malaria (20.2%) and Gram-positive bloodstream infection (16.7%). Significant risk factors for death by logistic regression modeling were inappropriate treatment due to antimicrobial resistance, HIV infection, other underlying infectious diseases, malnutrition and bloodstream infection caused by Enterobacteriaceae, other Gram-negatives and candida.

Conclusion

Bloodstream infection was less common than malaria, but caused more deaths. The frequent use of antimicrobials prior to blood culture may have hampered the detection of organisms susceptible to commonly used antimicrobials, including pneumococci, and thus the study probably underestimates the incidence of bloodstream infection. The finding that antimicrobial resistance, HIV-infection and malnutrition predict fatal outcome calls for renewed efforts to curb the further emergence of resistance, improve HIV care and nutrition for children.

Clinical and economic impact of multidrug resistance in nosocomial Acinetobacter baumannii bacteremia

OBJECTIVE

To investigate the impact of antimicrobial resistance on clinical and economic outcomes among hospitalized patients with multidrug-resistant (MDR) Acinetobacter baumannii bacteremia.

DESIGN

A retrospective, matched-cohort study.

SETTING

A tertiary care university teaching hospital.

METHODS

A matched case-control (1 : 1) study was conducted to compare the differences in clinical and economic outcomes of patients with MDR A. baumannii bacteremia and patients with non-MDR A. baumannii bacteremia. Case patients were matched to control patients on the basis of sex, age, severity of underlying and acute illness, and length of hospital stay before onset of bacteremia.

RESULTS

Forty-six (95.8%) of 48 cases with MDR A. baumannii bacteremia were eligible for the study and matched with appropriate controls. The sepsis-related mortality rate was 34.8% among cases and 13.0% among controls, for an attributable mortality rate of 21.8% (adjusted odds ratio, 4.1 [95% confidence interval, 1.1-15.7]; P=.036). After the onset of bacteremia, cases and controls had a significantly different length of hospital stay (54.2 vs 34.1 days; P=.006), hospitalization cost (US$9,349 vs US$4,865; P=.001), and antibiotic therapy cost (US$2,257 vs US$1,610; P=.014). Thus, bacteremia due to MDR A. baumannii resulted in 13.4 days of additional hospitalization and US$3,758 of additional costs, compared with bacteremia due to non-MDR A. baumannii.

CONCLUSIONS

Patients with MDR A. baumannii bacteremia had a higher mortality rate and incurred greater medical costs than patients with non-MDR A. baumannii bacteremia.

Predictors of mortality in patients with bloodstream infections caused by extended-spectrum-beta-lactamase-producing Enterobacteriaceae: importance of inadequate initial antimicrobial treatment

Bloodstream infections (BSI) caused by extended-spectrum beta-lactamase (ESBL)-producing organisms markedly increase the rates of treatment failure and death. We conducted a retrospective cohort analysis to identify risk factors for mortality in adult in-patients with BSI caused by ESBL-producing Enterobacteriaceae (ESBL-BSI). Particular attention was focused on defining the impact on the mortality of inadequate initial antimicrobial therapy (defined as the initiation of treatment with active antimicrobial agents >72 h after collection of the first positive blood culture). A total of 186 patients with ESBL-BSI caused by Escherichia coli (n = 104), Klebsiella pneumoniae (n = 58), or Proteus mirabilis (n = 24) were identified by our microbiology laboratory from 1 January 1999 through 31 December 2004. The overall 21-day mortality rate was 38.2% (71 of 186). In multivariate analysis, significant predictors of mortality were inadequate initial antimicrobial therapy (odds ratio [OR] = 6.28; 95% confidence interval [CI] = 3.18 to 12.42; P < 0.001) and unidentified primary infection site (OR = 2.69; 95% CI = 1.38 to 5.27; P = 0.004). The inadequately treated patients (89 of 186 [47.8%]) had a threefold increase in mortality compared to the adequately treated group (59.5% versus 18.5%; OR = 2.38; 95% CI = 1.76 to 3.22; P < 0.001). The regimens most commonly classified as inadequate were based on oxyimino cephalosporin or fluoroquinolone therapy. Prompt initiation of effective antimicrobial treatment is essential in patients with ESBL-BSI, and empirical decisions must be based on a sound knowledge of the local distribution of pathogens and their susceptibility patterns.

Impact of imipenem resistance on mortality in patients with Acinetobacter bacteraemia

OBJECTIVES

To investigate the impact of imipenem resistance on the mortality rate among patients with Acinetobacter bacteraemia.

METHODS

A retrospective, pairwise-matched (1:1), risk-adjusted (age, Pitt bacteraemia score) cohort study was performed at three tertiary care hospitals in Korea from January 2000 to June 2005.

RESULTS

Forty patients with imipenem non-susceptible Acinetobacter bacteraemia (INAB group) and 40 matched subjects (1:1 ratio) with imipenem-susceptible Acinetobacter bacteraemia (ISAB group) were included. Both groups had similar clinical features related to the severity of illness. The 30 day mortality rate was higher in the INAB group (57.5%) than the ISAB group (27.5%) (P = 0.007). The rate of discordant antimicrobial therapy was higher in the INAB group (65.0%) than the ISAB group (20.0%) (P < 0.001). The 30 day mortality rate was higher in the patients with discordant antimicrobial therapy (67.6%) than concordant antimicrobial therapy (23.9%) (P < 0.001). Multivariate analysis showed that age, the Pitt bacteraemia score, immunosuppressive status, and discordant antimicrobial therapy were independent risk factors for 30 day mortality among patients with Acinetobacter bacteraemia (P < 0.05). When discordant antimicrobial therapy was excluded in the multivariate analysis, the imipenem resistance was associated with 30 day mortality (P = 0.005).

CONCLUSIONS

Imipenem resistance has a significant impact on the mortality rate among patients with Acinetobacter bacteraemia, and this is mainly attributable to the higher rate of discordant antimicrobial therapy.

De-escalation in lower respiratory tract infections

PURPOSE OF REVIEW

The present article reviews recent data on the de-escalation of empirical antibiotic treatment on pneumonia, with special attention to newer strategies aimed at increasing adequacy and minimizing resistance emergence risks in ventilator-associated pneumonia.

RECENT FINDINGS

A de-escalation strategy is feasible in a large proportion of patients with pneumonia, and at least two reports have associated de-escalation with a significantly better survival. Combined with other strategies, such as using biomarkers (e.g. C-reactive protein or procalcitonin), antibiotic heterogeneity, adherence to local microbiological flora, objective clinical criteria of non-response and of clinical ventilator-associated pneumonia resolution, they contribute to rationalizing and individualizing antimicrobial therapy.

SUMMARY

A patient-based approach with prompt adequate empirical therapy, using broad-spectrum antibiotics based on reliable local microbiological data with streamlining as soon as microbiological data become available, allow outcomes to be improved and the emergence of resistance to be minimized.

Antimicrobial Resistance

Development of antimicrobial resistance is an inevitable consequence of exposure of microorganisms to antimicrobial agents. Although emergence of resistance cannot be prevented, it can be retarded by minimizing use of antimicrobial agents and avoiding selection of relatively resistant pathogenic and nonpathogenic strains caused by exposure to tissue concentrations that confer a competitive advantage. Most attention in veterinary medicine has focused on the emergence of resistance in food-borne pathogens, with relatively little attention being devoted to small companion animals, despite the frequent use of antimicrobial agents in these animals, evidence that resistance is emerging, and potential for transfer of resistance between companion animals and people. To retard further emergence of resistance in small companion animals, it is imperative that surveillance programs be instituted to monitor development of resistance.

Non-inherited antibiotic resistance

In addition to their impressive, well-publicized and well-researched propensity to evolve and acquire genetically determined mechanisms for resistance to antibiotics, bacteria that are inherently susceptible to these drugs can also be phenotypically refractory to their action. This phenomenon of 'non-inherited resistance' to antibiotics has been known since the beginning of the antibiotic era but, relative to inherited resistance, it has been given little attention. Here, we review the in vitro and in vivo evidence for the different forms of non-inherited resistance and the mechanisms responsible. With the aid of a simple mathematical model and computer simulations, we show how non-inherited resistance could extend the duration of antibiotic treatment, cause treatment failure and promote the generation and ascent of inherited resistance in treated patients.

Antimicrobial resistance: factors and outcomes

Antimicrobial resistance in the ICU is characterized by increasing overall resistance rates among gram-negative and gram-positive pathogens and increased frequency of multidrug-resistant organisms. In addition to basic principles of appropriate drug selection for empiric and definitive therapy, other specific strategies that may decrease problems of resistance through improved use of antimicrobials include appropriate application of pharmacokinetic and pharmacodynamic principles to antimicrobial use, aggressive dosing of antimicrobials, use of broad-spectrum and combination antimicrobial therapy for initial treatment, decreased duration of antimicrobial therapy, hospital formulary-based antimicrobial restrictions, use of antimicrobial protocols and guidelines, programs for restriction of target antimicrobials, scheduled antimicrobial rotation, and use of antimicrobial management programs. Combinations of various approaches may offer the best potential for effectively intervening in and reducing the spread of resistant pathogens in critically ill patients.

Antimicrobial activity of cefepime tested against ceftazidime-resistant Gram-negative clinical strains from North American Hospitals: report from the SENTRY Antimicrobial Surveillance Program (1998-2004)

To assess the effect of ceftazidime resistance on the activity of other antimicrobial agents, 3030 ceftazidime-resistant Gram-negative bacilli (GNB) isolates (of a total of 42061 GNB) were tested against a panel of more than 30 agents. Ceftazidime resistance was observed in 40.3% of Acinetobacter spp., 16.9% of Pseudomonas aeruginosa, and 5.7% of Enterobacteriaceae isolates. The highest rates of ceftazidime resistance among the enteric GNB were observed with Enterobacter spp. (20.9%) >Citrobacter spp. (15.3%) > indole-positive Proteae (10.1%). Overall, 90% of ceftazidime-resistant Enterobacteriaceae and 30% of ceftazidime-resistant P. aeruginosa remained susceptible to the "4th-generation" cephalosporin, cefepime. The activities (% susceptible) of other antimicrobials tested against ceftazidime-resistant Enterobacteriaceae and P. aeruginosa, respectively, were as follows: amikacin, 90% and 88%; ciprofloxacin, 63% and 46%; gentamicin, 59% and 67%, imipenem, 99% and 65%; levofloxacin, 69% and 44%; and piperacillin/tazobactam only 40% and 12%. Ceftazidime-resistant GNB exhibited high rates of resistance to other antimicrobials. Cefepime was very active against ceftazidime-resistant enteric GNB (AmpC enzyme producers), especially Enterobacter spp. (94.3% susceptible), Citrobacter spp. (96.7% susceptible), and indole-positive Proteae (89.6% susceptible), and showed activity similar to that of ceftazidime against all P. aeruginosa and Acinetobacter spp. isolated in North American medical centers. Continued resistances surveillance monitoring will be necessary to assess the effectiveness of widely used broad-spectrum antimicrobials as novel resistance mechanisms emerge.

Resistance to Anti-Infective Drugs and the Threat to Public Health

Increasing resistance of pathogens to anti-infective drugs is an urgent public health problem that must be addressed through more prudent use of these drugs in human medicine and in animal husbandry, agriculture, and aquaculture.

[Management of nosocomial pneumonia-state of the art]

Nosocomial pneumonia is among the most frequent infections in the intensive care unit with high morbidity and mortality. The decisive factor for treatment failure is inadequate previous antibiotic treatment. Broad spectrum and sufficiently high dosed initial treatment is crucial.To prevent further resistances, the antibiotic treatment must be evaluated early. Depending on the treatment success, treatment has to be changed or terminated. Deescalation is possible and sensible after three days. A treatment period of seven days should not routinely be exceeded. The treatment recommendations should be adapted to local resistances and the local statistics of frequent pathogens. A further factor for treatment decision-making is the risk analysis of the patient (previous treatment, stays in hospitals or nursing homes, concomitant diseases).