Three-year experience with amikacin sulfate as an exclusive surgical aminoglycoside in a large acute-care hospital

Impact of aminoglycoside cycling in six tertiary intensive care units: prospective longitudinal interventional study

AIM

To determine the effect of aminoglycoside cycling in six tertiary intensive care units (ICU) on the rates of sepsis, aminoglycoside resistance patterns, antibiotic consumption, and costs.

METHODS

This was a prospective longitudinal interventional study that measured the effect of change from first-line gentamicin usage (February 2002-February 2003) to amikacin usage (February 2003-February 2004) on the aminoglycoside resistance patterns, number of patients with gram-negative bacteremia, consumption of antibiotics, and the cost of antimicrobial drugs in 6 tertiary care ICUs in Zagreb, Croatia.

RESULTS

The change from first-line gentamicin to amikacin usage led to a decrease in the overall gentamicin resistance of gram-negative bacteria (GNB) from 42% to 26% (P<0.001; z-test of proportions) and netilmicin resistance from 33% to 20% (P<0.001), but amikacin resistance did not change significantly (P=0.462), except for Acinetobacter baumanni (P=0.014). Sepsis rate in ICUs was reduced from 3.6% to 2.2% (P<0.001; chi(2) test), with a decline in the number of nosocomial bloodstream infections from 55/100 patient-days to 26/100 patient-days (P=0.001, chi(2) test). Furthermore, amikacin use led to a 16% decrease in the overall antibiotic consumption and 0.1 euro/patient/d cost reduction.

CONCLUSION

Exclusive use of amikacin significantly reduced the resistance of GNB isolates to gentamicin and netilmicin, the number of GNB nosocomial bacteremias, and the cost of total antibiotic usage in ICUs.

[Impact of initial antibiotic therapy on the course of resistance to fluoroquinolones and aminoglycosides in Gram-negative bacilli isolated from intensive care patients]

OBJECTIVE

To evaluate the effect of the initial antibiotic therapy associating a betalactam antibiotic (BLA) with either an aminoglycoside (AG) or a fluoroquinolone (FQ) on the development of resistance of gram-negative bacilli in an intensive care unit.

STUDY DESIGN

Prospective bacteriological surveillance study.

PATIENTS

The study included 51 patients experiencing a second infection with gram-negative organisms, eight days or more after a first infection.

METHOD

The incidences of bacterial infection and the antimicrobial susceptibility have been assessed.

RESULTS

The first-choice therapy was based either on BLA + AG (51%), or on BLA + FQ in the others (46%). The causative organisms were Enterobacteriaceae (57%) and Pseudomonas aeruginosa (31%). The second infection occurred 23 +/- 11 days after the first. The main organisms involved were Pseudomonas aeruginosa (51%) and Enterobacteriaceae (41%). In the group treated initially with an AG, only the antibiotic susceptibility for amikacin decreased significantly (72 vs 36%, p < 0.05). The latter was the most prescribed antibiotic (56%). In the FQ group, there was a significant decrease of susceptibility for ciprofloxacin, pefloxacin, netilmicin and tobramycin. The decrease was not significant for gentamicin and amikacin.

CONCLUSIONS

In intensive care patients, the use of FQ in association with a BLA increases the resistance to AG and FQ. Therefore it seems preferable to administer an AG in association with a BLA. Amikacine should only be prescribed when justified for a given case.

The aminoglycosides

Despite the introduction of newer, less toxic antimicrobial agents, the aminoglycosides continue to serve a useful role in the treatment of serious enterococcal, mycobacterial, and gram-negative bacillary infections. Gentamicin, because of its low cost, remains the aminoglycoside of choice in hospitals with low levels of resistance among Enterobacteriaceae and Pseudomonas aeruginosa. Typically, it is administered in combination with beta-lactam antibiotics, but it may also be used as monotherapy for urinary tract infections or tularemia. Amikacin is useful against gentamicin-resistant gram-negative bacilli and also in the treatment of infections caused by susceptible Nocardia and nontuberculous mycobacteria. Streptomycin serves an important role in the treatment of multidrug-resistant tuberculosis and may be useful in the treatment of some gentamicin-resistant enterococcal infections. Despite an alarming increase in aminoglycoside-resistant enterococci, most institutions have noted little change in patterns of resistance among gram-negative bacilli. Although the development of newer, less toxic aminoglycosides is unlikely in the near future, single daily dosing regimens have been proposed as a convenient, cost-effective strategy. In selected patients, this novel approach seems to be as safe and effective as traditional, multidose regimens.

Resistance to amikacin and gentamicin among Gram-negative bloodstream isolates in a university hospital between 1989 and 1994

OBJECTIVE: To characterize antimicrobial resistance patterns to amikacin (AN) and gentamicin (GM) among Gram-negative bloodstream isolates and to determine the possible relationship between use of AN and GM and the occurrence of antibiotic resistance during a 6-year period. METHODS: Standard media and techniques of isolation and identification were used. Antimicrobial susceptibility testing was performed with the disk diffusion method and API rapid ATB E strips. Data on consumption of aminoglycosides were collected by the central hospital pharmacy and were expressed as daily defined doses. RESULTS: One thousand nine hundred and four bloodstream isolates were tested for AN and GM susceptibility between 1989 and 1994. Activities of AN and GM remained high during the study period against most isolates of Gram-negative bacteria. No relationship could be observed between the use of AN/GM and the rate of AN/GM resistance. Nosocomial Gram-negative bloodstream isolates showed a higher degree of resistance towards both AN (3.9% of all nosocomial isolates) and GM (7.9%) than community-acquired isolates (1.8% toward AN and 3.1% towards GM, respectively). There was a significant increase (P=0.004) in the risk of GM resistance in patients with nosocomial Gram-negative bacteremia detected more than 14 days after admission. The proportion of GM-susceptible Pseudomonas aeruginosa isolates decreased linearly from 97% for infections acquired between day 3 and day 10 following admission to 80% for bacteremia developing 30 days or more after admission (P=0.008). CONCLUSIONS: AN and GM remain highly active antimicrobial drugs for treatment of GNB in times of growing resistance to cephalosporins and fluoroquinolones.

In vitro activities of cefepime alone and with amikacin against aminoglycoside-resistant gram-negative bacteria

The in vitro activity of cefepime was compared with those of ceftazidime, cefotaxime, and cefpirome against aminoglycoside-resistant gram-negative bacteria. Cefepime was the most active cephalosporin, with a MIC for 90% of strains tested for all non-Pseudomonas aeruginosa species of less than or equal to 4 micrograms/ml. No cefepime resistance was encountered among members of the family Enterobacteriaceae. Of the 40 aminoglycoside-resistant P. aeruginosa isolates, 15% were resistant to cefepime, compared with 18% for ceftazidime, 30% for cefpirome, and 35% for cefotaxime. Synergism between cefepime and amikacin was observed and occurred most frequently in P. aeruginosa strains resistant to cefepime but susceptible to amikacin. In no case did cefepime and amikacin exhibit antagonism against P. aeruginosa.

The aminoglycosides

Despite the introduction of newer, less toxic antimicrobial agents, the aminoglycosides continue to serve a useful role in the treatment of serious enterococcal and gram-negative bacillary infections. Gentamicin, because of its low cost, remains the aminoglycoside of choice in hospitals with low levels of resistance among Enterobacteriaceae and Pseudomonas aeruginosa. Amikacin is useful against gentamicin-resistant gram-negative bacilli and also in the treatment of infections caused by susceptible Nocardia and nontuberculous mycobacteria. An alarming increase in resistance to aminoglycosides among enterococci has been noted, despite little change in susceptibility patterns among gram-negative bacilli. Future efforts will need to be directed toward a better understanding of mechanisms of antimicrobial resistance and toward the prevention of aminoglycoside-induced toxicity.

Aminoglycoside antibiotics in clinical use

Aminoglycosides are among the most used antibiotics despite competitive pressure from newer beta-lactam agents. The activity profile, pharmacology, toxicity potential, and methods of toxicity prevention of aminoglycosides are well appreciated after three decades. Nephrotoxicity, ototoxicity, and the added costs of drug level monitoring limit wider usage, but great activity against highly antibiotic resistant gram negative bacteria often outweigh these disadvantages and will likely keep aminoglycosides available for the foreseeable future.

The aminoglycosides: streptomycin, kanamycin, gentamicin, tobramycin, amikacin, netilmicin, and sisomicin

Despite the introduction of newer, less toxic antimicrobial agents, the aminoglycosides remain useful in the treatment of serious, hospital-acquired, gram-negative bacillary infections, especially those caused by Pseudomonas aeruginosa. Formidable nephrotoxicity and ototoxicity have limited the use of neomycin to topical or oral administration. Widespread antimicrobial resistance among Enterobacteriaceae has restricted the use of streptomycin and kanamycin to a few specific clinical situations. Gentamicin, tobramycin, and amikacin are active against a wide range of Enterobacteriaceae and many P. aeruginosa organisms. In medical centers where gentamicin resistance is prevalent, amikacin is the aminoglycoside of choice. Fortunately, amikacin resistance has not seemed to increase substantially, even in institutions where usage has been extensive for a long period. No new aminoglycoside has proved to be superior to amikacin.

Aminoglycoside antibiotics in infectious diseases. An overview

This article presents an overview of the aminoglycoside antibiotics used in clinical practice. Facts concerning the discovery and properties of the aminoglycosides are followed by information about spectrums of activity and mechanisms of action and resistance. Individual compounds are compared and proposals on the possibilities for their clinical use, both as single drugs and in combination with beta-lactam antibiotics, are made. The importance placed on measuring the serum concentrations of aminoglycoside antibiotics should serve as a remainder that this procedure is important, on one hand, to increase clinical efficacy and, on the other, to reduce the side effects of these antibiotics. Finally, the aminoglycosides are compared briefly with other antibacterial compounds, some of which are very new. There is no doubt that in the future the aminoglycosides will continue to occupy an important place in the treatment of severe infections, although newly developed agents appear to be effective complements.