Antibiotic therapy for multidrug-resistant nosocomial infections (Pseudomonas spp., Acinetobacter spp., and Enterobacteriaceae)

Pathogenic bacteria have increasingly been resisting to antimicrobial therapy. Re-
cently, resistance problem has been relatively much worsened in Gram-negative
bacilli. Acinetobacter spp. are typical nosocomial pathogens causing infections
and high mortality, almost exclusively in compromised hospital patients. Acineto-
bacter spp. are intrinsically less susceptible to antibiotics than Enterobacteriaceae,
and have propensity to acquire resistance. A surveillance study in Korea in 2009
showed that resistance rates of Acinetobacter spp. were very high: to fluoroquino-
lone 67%, to amikacin 48%, to ceftazidime 66% and to imipenem 51%. Carbape-
nem resistance was mostly due to OXA type carbapenemase production in A. bau-
mannii isolates, whereas it was due to metallo-β-lactamase production in non-
baumannii Acinetobacter isolates. Colistin-resistant isolates were rare but started
to be isolated in Korea. Currently, the infection caused by multidrug-resistant A.
baumannii is among the most difficult ones to treat. Analysis at tertiary care hospi-
tal in 2010 showed that among the 1,085 isolates of Acinetobacter spp., 14.9% and
41.8% were resistant to seven, and to all eight antimicrobial agents tested, respec-
tively. It is known to be difficult to prevent Acinetobacter spp. infection in hospi-
talized patients, because the organisms are ubiquitous in hospital environment. Ef-
forts to control resistant bacteria in Korea by hospitals, relevant scientific societies
and government agencies have only partially been successful. We need concerted
multidisciplinary efforts to preserve the efficacy of currently available antimicrobi-
al agents, by following the principles of antimicrobial stewardship.