Aminoglycoside Resistance in ICUs: Are We Running out of Drugs, for Bad Bugs

Many classes of antibacterial drugs are currently available for physicians to use, however the plan of antibiotic development has slowed during the last decade. The World Health Organization (WHO) has identified antimicrobial resistance as one of the 3 most important problems for human health. Antimicrobial resistance is a growing problem worldwide, especially in hospitals, where resistant organisms are often first detected in ICU (Intensive Care Unit). It is demonstrated that resistant bacteria are more isolated from ICUs compared with other hospital wards and outpatient clinics, and ICU stay may be an independent risk factor for acquiring multidrugresistant strains infection. Moreover, it must be considered that ICUs patients are often colonized with multidrugresistant strains, which often spread to other wards. Resistance to the current antibiotics is a serious problem in the whole world including our country, Iran. New antibiotics that have been discovered and introduced into clinical practice in the last few years are mostly active against Gram-positive organisms, forcing us to consider aminoglycosides and polymixins. As Infections caused by gram-negative bacteria are at the top causes of morbidity and mortality in critically ill patients; the knowledge of these organisms antibiotic resistance is crucial for ICU practitioners. Recently, increased resistance has been observed against third-generation cephalosporins for Gramnegative bacilli, but aminoglycosides are a class of antibiotics that their use has been associated with less increase in microbial resistance over the years when compared with β lactam antibiotics. The aminoglycoside antibiotics have been used for treating gram-negative bacillary infections in critically ill patients in the 1940s and resistance to these agents was initially described in the 1960s. Nine aminoglycosides (gentamicin, tobramycin, amikacin, streptomycin, neomycin, kanamycin, paromomycin, netilmicin, and spectinomycin) are approved by the Food and Drug Administration (FDA) for clinical use in the United States. Of them, gentamicin, tobramycin, amikacin, and netilmicin are the main aminoglycosides still in use. The incidence of antibiotics resistance in hospital-acquired infections varies among bacterial species, clinical settings, and even countries, and may be related to local epidemic spread of a few colonies. In some reports approximately 75% of Klebsiella pneumoniae, 87% of Enterobacter spp, 55% of Pseudomonas aeruginosa, and 75% of methicillin-resistant Staphylococcus aureus (MRSA) strains were drug-resistant to at least three different classes. Although, in Gerding et al study, resistance to aminoglycosides were at the lowest level in 10 years, and only Pseudomonas aeroginosa strains exibit resistance to gentamicin. Although, in some centers, amikacin has been effective against organisms resistant to gentamicin and tobramycin. Aminoglycoside resistance to Gram-negative bacteria has different pattern among countries. For example amikacin resistance is increasingly progressive in Turkey. In southern europe aminoglycoside resistance is higher than in central europe and northern europe. Unfortunatelly, in one study performed in Iran, the rate of aminoglycoside resistance was found to be high. One specific organism regard to aminoglycoside resistance is Entrococci which is intrinsically Copyright © 2011 by School of Pharmacy Shaheed Beheshti University of Medical Sciences and Health Services Iranian Journal of Pharmaceutical Research (2011), 10 (3): 391-392