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Table 1. Gram-negative Bacterial Isolates in Intensive Care Unit Patients*
Image description not available.
Table 2. Percentage of Decreased Antibiotic Susceptibility Among Gram-negative Isolates From ICU Patients*
Image description not available.
1.
Vincent JL, Bihari DJ, Suter PM.  et al.  The prevalence of nosocomial infection in intensive care units in Europe: results of the European Prevalence of Infection in Intensive Care (EPIC) Study.  JAMA.1995;274:639-644.
2.
Davin-Regli A, Monnet D, Saux P.  et al.  Molecular epidemiology of Enterobacter aerogenes acquisition: one year prospective study in two intensive care units.  J Clin Microbiol.1996;34:1474-1480.
3.
Jarlier V, Fosse T, Philippon A, for the ICU Study Group. Antibiotic susceptibility in aerobic gram-negative bacilli isolated in intensive care units in 39 French teaching hospitals (ICU study).  Intensive Care Med.1996;22:1057-1065.
4.
Verbist L. Incidence of multi-resistance in gram-negative bacterial isolates from intensive care units in Belgium: a surveillance study.  Scand J Infect Dis.1991;78(suppl):45-53.
5.
Shah PM, Asanger R, Kahan FM. Incidence of multi-resistance in gram-negative aerobes from intensive care units of 10 German hospitals.  Scand J Infect Dis.1991;78(suppl):22-34.
6.
Buirma RJA, Horrevorts AM, Wagenvoort JHT. Incidence of multi-resistant gram-negative isolates in eight Dutch hospitals.  Scand J Infect Dis.1991;78(suppl):35-44.
7.
Itokazu GS, Quinn JP, Bell-Dixon C, Kahan FM, Weinstein RA. Antimicrobial resistance rates among gram-negative bacilli recovered from patients in intensive care units: evaluation of a national postmarketing surveillance program.  Clin Infect Dis.1996;23:779-784.
8.
Glupczynski Y, Delmée M, Goossens H, Struelens M. A multicentre survey of antimicrobial resistance in gram-negative isolates from Belgian intensive care units in 1994-1995.  Acta Clin Belg.1998;53:28-38.
9.
Hanberger H, Nilsson LE, and the Swedish ICU Study Group. High frequency of antibiotic resistance among gram-negative isolates in intensive care units at 10 Swedish hospitals.  Clin Microbiol Infect.1997;3:208-215.
10.
Burwen DR, Banerjee SN, Gaynes RP, and the National Nosocomial Infections Surveillance System. Ceftazidime resistance among selected nosocomial gram-negative bacilli in the United States.  J Infect Dis.1994;170:1622-1625.
11.
Emori TG, Culver DH, Horan TC.  et al.  National Nosocomial Infections Surveillance (NNIS) System: description of surveillance methodology.  Am J Infect Control.1991;19:19-35.
12.
Brown DF, Brown L. Evaluation of the E test, a novel method of quantifying antimicrobial activity.  J Antimicrob Chemother.1991;27:185-190.
13.
National Committee for Clinical Laboratory Standards (NCCLS). Minimum Inhibitory Concentration (MIC) Interpretive Standards M7-A4Villanova, Pa: National Committee for Clinical Laboratory Standards; 1997. Document 2.
14.
Archibald L, Phillips L, Monnet D, McGowan JE, Tenover F, Gaynes R. Antimicrobial resistance in isolates from inpatients and outpatients in the United States: increasing importance of the intensive care unit.  Clin Infect Dis.1997;24:211-215.
15.
Livermore DM. Beta-lactamases in laboratory and clinical resistance.  Clin Microbiol Rev.1995;8:557-584.
16.
Chow JW, Fine MJ, Shlaes DM.  et al.  Enterobacter bacteremia: clinical features and emergence of antibiotic resistance during therapy.  Ann Intern Med.1991;115:585-590.
17.
Philippon A, Labia R, Jacoby G. Extended-spectrum beta-lactamases.  Antimicrob Agents Chemother.1989;33:1131-1136.
18.
Livermore DM, Yuan M. Antibiotic resistance and production of extended-spectrum beta-lactamases amongst Klebsiella spp from intensive care units in Europe.  J Antimicrob Chemother.1996;38:409-424.
19.
Tilley PAG, Roberts FJ. Bacteremia with Acinetobacter species: risk factors and prognosis in different clinical settings.  Clin Infect Dis.1994;18:896-900.
20.
Cisneros JM, Reyes MJ, Pachón J.  et al.  Bacteremia due to Acinetobacter baumannii: epidemiology, clinical findings and prognostic features.  Clin Infect Dis.1996;22:1026-1032.
21.
Riley TV, Webb SA, Cadwallader H, Briggs BD, Christiansen L, Bowman RA. Outbreak of gentamicin-resistant Acinetobacter baumanii in an intensive care unit: clinical, epidemiologic and microbiological features.  Pathology.1996;28:359-363.
22.
Goetz A, Yu VL. The intensive care unit: the hottest zone.  Curr Opin Infect Dis.1997;10:319-323.
23.
Meyer KS, Urban C, Eagan JA, Berger BJ, Rahal JJ. Nosocomial outbreak of Klebsiella infection resistant to late-generation cephalosporins.  Ann Intern Med.1993;119:353-358.
24.
Jacobson KL, Cohen SH, Inciardi JF.  et al.  The relationship between antecedent antibiotic use and resistance to extended-spectrum cephalosporins in group I beta-lactamase-producing organisms.  Clin Infect Dis.1995;21:1107-1113.
25.
Goldmann DA, Weinstein RA, Wenzel RP.  et al.  Strategies to prevent and control the emergence and spread of antimicrobial-resistant microorganisms in hospitals.  JAMA.1996;275:234-240.
Caring for the Critically Ill Patient
January 6, 1999

Antibiotic Susceptibility Among Aerobic Gram-negative Bacilli in Intensive Care Units in 5 European Countries

Author Affiliations

Author Affiliations: Departments of Infectious Diseases (Dr Hanberger) and Clinical Microbiology (Dr Nilsson), University Hospital, Linköping, Sweden; and the Department of Microbiology, University Hospital, Salamanca, Spain (Dr Garcia-Rodriguez); Department of Microbiology, Hospital Le Fe, Valencia, Spain (Dr Gobernado); Department of Microbiology, University Hospital, Antwerp, Belgium (Dr Goossens); and Department of Microbiology, University of Brussels Hospital Erasme, Brussels, Belgium (Dr Struelens). A complete list of the members of the ICU Study Groups appears at the end of this article.

 

Caring for the Critically Ill Patient Section Editor: Deborah J. Cook, MD, Consulting Editor, JAMA. Advisory board: David Bihari, MD; Christian Brun-Buisson, MD; Timothy Evans, MD; John Heffner, MD; Norman Paradis, MD.

JAMA. 1999;281(1):67-71. doi:10.1001/jama.281.1.67
Context

Context Surveillance of antibiotic resistance is especially important in intensive care units (ICUs) because the infection rates are much higher there than in other hospital wards and most epidemics with multiresistant bacteria originate in ICUs.

Objective To evaluate the incidence of decreased antibiotic susceptibility among aerobic gram-negative bacilli isolated from patients in ICUs.

Design Consecutive specimens collected on clinical indications from ICU patients were cultured and tested. Minimum inhibitory concentrations for amikacin, ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, piperacillin, and piperacillin-tazobactam were determined using E test.

Setting Eighteen hospitals in Belgium, 40 in France, 20 in Portugal, 30 in Spain, and 10 in Sweden.

Subjects A total of 9166 gram-negative strains were initially isolated from 7308 patients between June 1994 and June 1995.

Main Outcome Measures The incidence of decreased susceptibility, defined as the sum of resistant and intermediate categories with use of the minimum inhibitory concentration break points recommended by the National Committee for Clinical Laboratory Standards.

Results The most frequently isolated organisms were Enterobacteriaceae (59\%) followed by Pseudomonas aeruginosa (24\%). The main sources were respiratory tract (42\%), urine (26\%), blood (14\%), abdomen (11\%), and skin and soft tissue (7\%). Decreased antibiotic susceptibility across all species and drugs was highest in Portuguese ICUs followed by French, Spanish, Belgian, and Swedish ICUs. The highest incidence of resistance was seen in all countries among P aeruginosa (up to 37\% resistant to ciprofloxacin in Portuguese ICUs and 46\% resistant to gentamicin in French ICUs), Enterobacter species, Acinetobacter species, and Stenotrophomonas maltophilia, and in Portugal and France among Klebsiella species.

Conclusion The high incidence of reduced antibiotic susceptibility among gram-negative bacteria in these ICUs suggests that more effective strategies are needed to control the selection and spread of resistant organisms.

More than 20% of patients admitted to European intensive care units (ICUs) develop an ICU-acquired infection.1 A high prevalence of decreased antibiotic susceptibility among gram-negative bacilli has been reported from ICU patients in France,2,3 Belgium,4 Germany,5 and the Netherlands during 1990 and 1991,6 the United States between 1990 and 1993,7 and Belgium8 and Sweden9 during 1994 and 1995.

The National Nosocomial Infections Surveillance System of the Centers for Disease Control and Prevention monitors secular trends of antibiotic resistance rates of nosocomial pathogens in US hospitals.10,11 No corresponding international surveillance system is operational in Europe. The aim of this study was to conduct a cross-country comparison of the incidence of antibiotic resistance among aerobic gram-negative bacilli from patients in ICUs in Belgium, France, Portugal, Spain, and Sweden using determination of minimum inhibitory concentration.

METHODS
Study Design and Bacterial Sampling

Multicenter susceptibility testing was performed using aerobic gram-negative bacilli isolated from patients admitted to ICUs between June 1994 and June 1995. The number of hospitals included was 18 in Belgium, 40 in France, 20 in Portugal, 30 in Spain, and 10 in Sweden, and these hospitals were chosen to represent different geographic areas of each country. Intensive care unit–acquired infections and ICU mortality have been the topic of a large, international, European epidemiological study.1 Consecutive specimens collected on the basis of clinical indications were cultured and tested. A total of 11,249 gram-negative bacterial strains were isolated from 7308 ICU patients. Of these, 9166 were initial isolates (first recovered during ICU admission) and 2083 were repeat isolates of the same species from the same patients. Repeat isolates were not included in this analysis. The number of initial isolates and patients in the various countries were as follows: Belgium, 1435 isolates from 1029 patients; France, 2988 isolates from 2205 patients; Portugal, 2067 isolates from 1882 patients; Spain, 2174 isolates from 1845 patients; and Sweden, 502 isolates from 347 patients; for a total of 9166 isolates from 7308 patients in all countries. Decreased antibiotic susceptibility was analyzed for pathogens collected from all sites and for blood isolates alone.

Susceptibility Testing

Minimum inhibitory concentrations for amikacin (except in Sweden), ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, piperacillin, and piperacillin-tazobactam were determined using the E test (AB BIODISK, Solna, Sweden).12 All laboratories performed quality control using reference strains of Escherichia coli ATCC 35218 and Pseudomonas aeruginosa ATCC 27853 to confirm consistency of materials, methods, and results. Decreased susceptibility (ie, resistant and intermediate categories) was defined using the minimum inhibitory concentration break points recommended by the National Committee for Clinical Laboratory Standards.13 The break points for susceptible and resistant categories were as follows: imipenem, 4 mg/L or less and 16 mg/L or more; ceftazidime, 8 mg/L or less and 32 mg/L or more; ceftriaxone, 8 mg/L or less and 64 mg/L or more; piperacillin, 16 mg/L or less and 128 mg/L or more (except P aeruginosa, ≤64 mg/L and ≥128 mg/L); piperacillin-tazobactam, 16/4 mg/L or less and 128/4 mg/L or more (except P aeruginosa, ≤64/4 mg/L and ≥128/4 mg/L); gentamicin, 4 mg/L or less and 16 mg/L or more; amikacin, 16 mg/L or less and 64 mg/L or more; and ciprofloxacin, 1 mg/L or less and 4 mg/L or more.13

RESULTS
Body Sites

The main sources of isolates were respiratory tract (42%), urine (26%), blood (14%), abdomen (11%), and skin and soft tissue (7%).

Organisms

The distribution of bacterial species is shown in Table 1. The most frequently isolated organisms in all countries were Enterobacteriaceae (59%) followed byP aeruginosa (24%). The most frequent species of Enterobacteriaceae were E coli, Enterobacter species, Klebsiella species, Serratia species, Proteus species, Morganella morganii, and Citrobacter species. The species included in Table 1 constituted 97% of the total strains in Belgium, 96% in France, 98% in Portugal, 98% in Spain, and 95% in Sweden.

Decreased Antibiotic Susceptibility

The incidence of decreased antibiotic susceptibility by species and country is shown in Table 2, indicating significant differences for some drug-pathogen combinations between countries.

COMMENT

In summary, we found that the percentage of decreased antibiotic susceptibility across all species and drugs was highest in Portuguese ICUs, followed by French, Spanish, Belgian, and Swedish ICUs. The highest incidence of resistance was seen in all countries among P aeruginosa, Enterobacter species, Acinetobacter species, and Stenotrophomonas maltophilia. In Portugal and France, there also was a high (20%-34%) level of decreased susceptibility to ceftazidime among Klebsiella species. The most active agents were amikacin and imipenem (Table 2). This is similar to findings from a large North American ICU study conducted between 1990 and 1993 of antibiotic resistance among gram-negative isolates.7

The high incidence of decreased susceptibility among gram-negative bacteria seen in France (Table 2) was similar to the findings of a French study performed during 1991.3 The overall resistance to most antibiotics found in Belgium8 (Table 2) was similar to that found in 1990 in studies performed in Belgium,4 Germany,5 and the Netherlands.6 However, because the methods of this and previous studies were different, a direct comparison of the findings is difficult. The high bacterial inoculum (108 colony-forming units [CFUs] per milliliter) provided by E test that was used in this study is a sensitive tool for detecting resistant subpopulations that may cause development of resistance during therapy. In previous studies, a microdilution method with a lower inoculum (104 CFUs/mL)36 was used that may not detect resistant subpopulations as easily as the E test.

The lower resistance levels found in Swedish ICUs compared with Belgium, France, Portugal, and Spain (Table 2) may be due to several different factors. These include prudent use of antibiotics, lower total antibiotic administration, and better compliance with infection control measures, such as hand disinfection and barrier precautions by health care workers.

Because our data represent all consecutive gram-negative isolates initially recovered from patients in the participating ICUs, they include pathogens isolated from patients with community- and hospital-acquired infections. No analysis was done to determine whether the isolates tested caused infection or only colonized these critically ill patients. The isolates from specimens other than blood may reflect colonization; however, colonization is often a prerequisite for infection. We found similarly high levels of decreased susceptibility among blood isolates compared with isolates from all sites (Table 2).

Bacterial resistance to ceftazidime is a serious emerging problem. Approximately 40% of Enterobacter cloacae were resistant to ceftazidime, according to studies of ICU isolates in the United States between 1987 and 199110 and between 1994 and 1995,14 which corresponds to the findings in our study (Table 2). This is probably related to production of stably derepressed chromosomal class-1 β-lactamase, which hydrolyzes β-lactam antibiotics other than carbapenems.15 Previous use of third-generation cephalosporins is more likely to cause the selection of resistance to β-lactams in blood isolates of Enterobacter species, which is associated with higher mortality.16 An increased ciprofloxacin resistance among Enterobacter species was seen in Belgium and France (Table 2) compared with previous studies performed in 19904 and 1991.3

In Portugal and France, 36% and 26%, respectively, of Klebsiella pneumoniae showed decreased susceptibility to ceftazidime (data not shown). This was probably caused by the production of extended-spectrum β-lactamases15,17 and is concordant with a study by Livermore and Yuan.18 According to Jarlier et al,3 decreased susceptibility to ceftazidime among K pneumoniae in French ICUs was 36% in 1991. In the United States, resistance to ceftazidime among K pneumoniae in ICU isolates increased from 3.6% in 1990 to 14.4% in 1993.7 Markedly lower resistance rates of Klebsiella species to all β-lactam antibiotics was observed in this study in Belgium compared with a previous study performed in 1990 (Table 2).

The lower susceptibility of P aeruginosa to imipenem compared with ceftazidime was consistent across all 5 countries in this study. The mechanism of resistance to imipenem among P aeruginosa (mainly decreased penetration through outer membrane) is well investigated and may occur more readily than development of resistance to ceftazidime (mainly related to hyperproduction of class 1 β-lactamases).15

Acinetobacter species (Table 2) and S maltophilia (data not shown) were the most resistant pathogens to all investigated drugs. Although not the most virulent gram-negative pathogen, Acinetobacter is an increasingly infectious threat, especially for patients receiving broad-spectrum antimicrobial therapy and requiring life support.1921 A Spanish study20 has shown that Acinetobacter isolates, usually acquired in the ICU, are multiresistant and may cause severe infections associated with a high mortality rate. Riley et al21 recently described the failure to stop the spread of gentamicin-resistant Acinetobacter baumannii in an Australian ICU despite infection control measures.

The high levels of decreased susceptibility among most species of gram-negative bacilli to ceftazidime, ceftriaxone, piperacillin, piperacillin-tazobactam, gentamicin, and ciprofloxacin in Belgium, Portugal, France, and Spain (Table 2) further limits use of these drugs for empirical monotherapy. Spread of multiresistant bacteria in the ICU can be minimized with infection control measures such as rigorous hand disinfection between patient contacts, barrier precautions, and isolation of patients infected with resistant isolates. We suggest that hospitals should have an active program for online antibiotic resistance surveillance of common drugs, using quantitatively accurate minimum inhibitory concentration methods, to constantly evaluate antibiotic administration and pharmacy formulary options. These measures have the potential to minimize morbidity and mortality associated with infections caused by multiresistant bacteria in critically ill patients.18,2225 However, studies to develop and evaluate the most effective strategies to minimize selection and spread of resistant organisms in the ICU are sorely needed, as are investigations to better quantify their clinical and economic consequences.

References
1.
Vincent JL, Bihari DJ, Suter PM.  et al.  The prevalence of nosocomial infection in intensive care units in Europe: results of the European Prevalence of Infection in Intensive Care (EPIC) Study.  JAMA.1995;274:639-644.
2.
Davin-Regli A, Monnet D, Saux P.  et al.  Molecular epidemiology of Enterobacter aerogenes acquisition: one year prospective study in two intensive care units.  J Clin Microbiol.1996;34:1474-1480.
3.
Jarlier V, Fosse T, Philippon A, for the ICU Study Group. Antibiotic susceptibility in aerobic gram-negative bacilli isolated in intensive care units in 39 French teaching hospitals (ICU study).  Intensive Care Med.1996;22:1057-1065.
4.
Verbist L. Incidence of multi-resistance in gram-negative bacterial isolates from intensive care units in Belgium: a surveillance study.  Scand J Infect Dis.1991;78(suppl):45-53.
5.
Shah PM, Asanger R, Kahan FM. Incidence of multi-resistance in gram-negative aerobes from intensive care units of 10 German hospitals.  Scand J Infect Dis.1991;78(suppl):22-34.
6.
Buirma RJA, Horrevorts AM, Wagenvoort JHT. Incidence of multi-resistant gram-negative isolates in eight Dutch hospitals.  Scand J Infect Dis.1991;78(suppl):35-44.
7.
Itokazu GS, Quinn JP, Bell-Dixon C, Kahan FM, Weinstein RA. Antimicrobial resistance rates among gram-negative bacilli recovered from patients in intensive care units: evaluation of a national postmarketing surveillance program.  Clin Infect Dis.1996;23:779-784.
8.
Glupczynski Y, Delmée M, Goossens H, Struelens M. A multicentre survey of antimicrobial resistance in gram-negative isolates from Belgian intensive care units in 1994-1995.  Acta Clin Belg.1998;53:28-38.
9.
Hanberger H, Nilsson LE, and the Swedish ICU Study Group. High frequency of antibiotic resistance among gram-negative isolates in intensive care units at 10 Swedish hospitals.  Clin Microbiol Infect.1997;3:208-215.
10.
Burwen DR, Banerjee SN, Gaynes RP, and the National Nosocomial Infections Surveillance System. Ceftazidime resistance among selected nosocomial gram-negative bacilli in the United States.  J Infect Dis.1994;170:1622-1625.
11.
Emori TG, Culver DH, Horan TC.  et al.  National Nosocomial Infections Surveillance (NNIS) System: description of surveillance methodology.  Am J Infect Control.1991;19:19-35.
12.
Brown DF, Brown L. Evaluation of the E test, a novel method of quantifying antimicrobial activity.  J Antimicrob Chemother.1991;27:185-190.
13.
National Committee for Clinical Laboratory Standards (NCCLS). Minimum Inhibitory Concentration (MIC) Interpretive Standards M7-A4Villanova, Pa: National Committee for Clinical Laboratory Standards; 1997. Document 2.
14.
Archibald L, Phillips L, Monnet D, McGowan JE, Tenover F, Gaynes R. Antimicrobial resistance in isolates from inpatients and outpatients in the United States: increasing importance of the intensive care unit.  Clin Infect Dis.1997;24:211-215.
15.
Livermore DM. Beta-lactamases in laboratory and clinical resistance.  Clin Microbiol Rev.1995;8:557-584.
16.
Chow JW, Fine MJ, Shlaes DM.  et al.  Enterobacter bacteremia: clinical features and emergence of antibiotic resistance during therapy.  Ann Intern Med.1991;115:585-590.
17.
Philippon A, Labia R, Jacoby G. Extended-spectrum beta-lactamases.  Antimicrob Agents Chemother.1989;33:1131-1136.
18.
Livermore DM, Yuan M. Antibiotic resistance and production of extended-spectrum beta-lactamases amongst Klebsiella spp from intensive care units in Europe.  J Antimicrob Chemother.1996;38:409-424.
19.
Tilley PAG, Roberts FJ. Bacteremia with Acinetobacter species: risk factors and prognosis in different clinical settings.  Clin Infect Dis.1994;18:896-900.
20.
Cisneros JM, Reyes MJ, Pachón J.  et al.  Bacteremia due to Acinetobacter baumannii: epidemiology, clinical findings and prognostic features.  Clin Infect Dis.1996;22:1026-1032.
21.
Riley TV, Webb SA, Cadwallader H, Briggs BD, Christiansen L, Bowman RA. Outbreak of gentamicin-resistant Acinetobacter baumanii in an intensive care unit: clinical, epidemiologic and microbiological features.  Pathology.1996;28:359-363.
22.
Goetz A, Yu VL. The intensive care unit: the hottest zone.  Curr Opin Infect Dis.1997;10:319-323.
23.
Meyer KS, Urban C, Eagan JA, Berger BJ, Rahal JJ. Nosocomial outbreak of Klebsiella infection resistant to late-generation cephalosporins.  Ann Intern Med.1993;119:353-358.
24.
Jacobson KL, Cohen SH, Inciardi JF.  et al.  The relationship between antecedent antibiotic use and resistance to extended-spectrum cephalosporins in group I beta-lactamase-producing organisms.  Clin Infect Dis.1995;21:1107-1113.
25.
Goldmann DA, Weinstein RA, Wenzel RP.  et al.  Strategies to prevent and control the emergence and spread of antimicrobial-resistant microorganisms in hospitals.  JAMA.1996;275:234-240.
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