Resistance in Gram-Negative Bacteria: Enterobacteriaceae
Section snippets
Overview of resistance trends and outcomes
Third-generation cephalosporins were originally developed as β-lactams able to overcome resistance caused by common β-lactamases. When first introduced, third-generation agents like ceftriaxone, cefotaxime, and ceftazidime were stable in the presence of common β-lactamases. However, within a few years, hospital-acquired gram-negative bacilli like Klebsiella pneumoniae and others began producing mutated versions of these β-lactamases that made them resistant to third-generation cephalosporins
General Issues and Nomenclature
Infections caused by ESBL-producing Enterobacteriaceae are serious concerns in the current environment. Many ESBLs represent enzymes that have evolved from class A β-lactamases—namely, TEM-1, TEM-2, and SHV-1, which are frequently expressed in gram-negative bacteria and which confer resistance to ampicillin, amoxicillin, and other penicillins, as well as to early- but not later-generation cephalosporins. ESBLs arose when mutations of the genes encoding TEM-1, TEM-2, or SHV-1 gave rise to new
Antibiotic resistance in Enterobacter species
Enterobacter spp are significant causes of nosocomial infection and are intrinsically resistant to aminopenicillins, cefazolin, and cefoxitin due to production of constitutive chromosomal AmpC β-lactamases.42 Moreover, β-lactam exposure is capable of inducing expression of AmpC β-lactamases in Enterobacter spp—with consequent resistance to third-generation cephalosporins—and mutations may result in permanent hyperproduction and persistent resistance. Treatment of Enterobacter infections with
Quinolone Resistance
Quinolones are used widely for the treatment of serious E coli UTIs and may also be used to treat other infections caused by other members of the Enterobacteriaceae family.52, 53 Hence, quinolone resistance in Enterobacteriaceae may lead to treatment failures and is a significant concern, as is the recent emergence of plasmid-mediated resistance to quinolones. According to the 2004 NNIS report, means of 7.3% and 8.2% of E coli isolates from US patients in both ICUs and non-ICU areas of
Summary
Enterobacteriaceae are significant causes of serious infections, and many of the most important members of this family are becoming increasingly resistant to currently available antibiotics. This is a troubling trend, and one that requires vigilance and intensified measures to control the further spread of resistance by these important gram-negative pathogens. Although improvements in antibiotic stewardship and infection control are discussed in greater detail by others in this supplement, it
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