Investigation of a Nosocomial Outbreak of Imipenem-Resistant Acinetobacter baumannii Producing the OXA-23 β-Lactamase in Korea

Abstract

We investigated an outbreak of Acinetobacter baumannii in an intensive care unit and in the surgery, medicine, neurology, and urology wards of the Kosin University Gospel Hospital in Busan, Korea. The outbreak involved 36 cases of infection by A. baumannii producing the OXA-23 ␤-lactamase over an 8-month period and was caused by a single pulsed-field gel electrophoresis clone. The epidemic isolates were characterized by a modified cloverleaf synergy test. Isoelectric focusing of crude bacterial extracts detected one nitrocefin-positive band with a pI value of 6.65. PCR amplification and characterization of the amplicons by direct sequencing indicated that the epidemic isolates carried a bla OXA-23 determinant. The epidemic isolates were characterized by a multidrug resistance phenotype that remained unchanged over the outbreak, including penicillins, cephamycins, extended-spectrum cephalosporins, carbapenems, monobactams, and aminoglycosides. This study shows that the bla OXA-23 resistance determinant may become an emerging therapeutic problem.Acinetobacter baumannii has emerged as an important nosocomial pathogen in outbreaks of hospital infections and is ranked second after Pseudomonas aeruginosa among nosocomial pathogens of aerobic nonfermentative gram-negative bacilli (17,19). A. baumannii causes respiratory and urinary tract infections, meningitis, endocarditis, burn infections, and wound sepsis, especially in intensive care units (ICUs) (4). A. baumannii infections are often difficult to eradicate due to high-level resistance to many antibiotics as a result of both intrinsic and acquired mechanisms. ␤-Lactamase production is the most important mechanism of acquired ␤-lactam resistance in gram-negative pathogens (21). Carbapenems (e.g., imipenem and meropenem) have become the drugs of choice against Acinetobacter infections in many centers but are being compromised by the emergence of carbapenem-hydrolyzing ␤-lactamase (carbapenemase) of molecular classes B and D (14). Class B carbapenemases found thus far in Acinetobacter spp. include various IMP-and VIM-type metallo-␤-lactamases (http: //www.lahey.org/studies/webt.asp), but most Acinetobacter spp. produce zinc-independent members of ␤-lactamase molecular class D (1). Sequenced carbapenemases of this latter class from that species include the following two distinct clusters: (i) the OXA-23-like cluster (OXA-23 and -27) and (ii) the OXA-24-like cluster . OXA-23 and OXA-27 have 99% amino acid identity, whereas they have only 60% identity with those of OXA-24-like cluster (1,3,6,7).Over an 8-month period from January to August 2003, 193 A. baumannii isolates were isolated from 193 patients hospitalized at the Kosin University Gospel Hospital. The purpose of the present study was to investigate an outbreak of A. baumannii in Korea and to characterize the imipenem resistance mechanism of the outbreak isolates. MATERIALS AND METHODS Bacterial strains and susceptibility tests. A total of 193 nonrepetitive clinical isolates of A. baumannii were isolated from Ja...

Increasing Trend of Imipenem-Resistance Among Acinetobacter baumannii Isolated From Hospital Acquired Pneumonia in Northeast of Iran

“…Today infection with multidrug-resistant (MDR), means that strains of Acinetobacter baumannii that are resistant to 3 current classes of antibiotics as well as strains of Acinetobacter baumannii in addition resistant to 3 common classes of antibiotics are resistant to imipenem as well and, are called extreme drug resistance (XDR) is increasing (24). This has created therapeutic implications and led to difficulties in treatment infections related to this bacterium and led to an increased length of stay, increased health care costs, an unfavorable prognosis and more mortality than sensitive strains (25,26). Carbapenames are a good choice for the treatment of resistant strains, are the class of betalactams that have broad antimicrobial activity, and used as a main choice for the treatment of resistant strains (24,25).…”

Prevalence and diversity of carbapenemases among imipenem-nonsusceptible Acinetobacter isolates in Korea: emergence of a novel OXA-182

“…In addition to the previously known 4 main groups of OXA carbapenemases, a novel OXA-143 was reported in 2009 from a Brazilian A. baumannii isolate (Higgins et al, 2009). In Korea, nosocomial outbreaks of OXA-23-producing A. baumannii were reported first in 2005 (Jeon et al, 2005) and then in 2006 (Jeong et al, 2006). A recent Korean surveillance study showed a high prevalence of bla OXA-23 -and bla OXA-51 -like gene-carrying A. baumannii isolates (Lee et al, 2009b).…”

Genotypic Investigation of Multidrug-Resistant Pseudomonas aeruginosa from Clinical Isolates in Korea, 2010

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