Pathogenic bacteria have increasingly been resisting to antimicrobial therapy. Recently, 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. Acinetobacter 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 fluoroquinolone 67%, to amikacin 48%, to ceftazidime 66% and to imipenem 51%. Carbapenem resistance was mostly due to OXA type carbapenemase production in A. baumannii isolates, whereas it was due to metallo-beta-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 hospital 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, respectively. It is known to be difficult to prevent Acinetobacter spp. infection in hospitalized patients, because the organisms are ubiquitous in hospital environment. Efforts 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 antimicrobial agents, by following the principles of antimicrobial stewardship.
Acinetobacter/classification/*drug effects/genetics/metabolism ; Anti-Bacterial Agents/pharmacology ; Bacterial Proteins/metabolism ; Drug Resistance, Multiple, Bacterial/genetics ; beta-Lactamases/metabolism

BACKGROUND: This study was performed to investigate the prevalence of qnr genes in clinical isolates of Escherichia coli from Korea that produce extended-spectrum beta-lactamases (ESBLs). METHODS: During the period of May to June 2005, we collected clinical isolates of E. coli that were intermediate or resistant to ceftazidime and/or cefotaxime from 11 Korean hospitals. Antimicrobial susceptibility was determined by the disk diffusion and agar dilution methods. ESBL production was confirmed phenotypically by the double-disk synergy test. ESBL and qnr genes were searched for by PCR amplification, and the PCR products were then subjected to direct sequencing. RESULTS: Double-disk synergy tests were positive in 84.3% (118/140) of ceftazidime- and/or cefotaxime-nonsusceptible E. coli isolates. The most prevalent types of ESBL in E. coli isolates were CTX-M-14 (N=41) and CTX-M-15 (N=58). Other ESBLs were also identified, including CTX-M-3 (N=7), CTX-M-9 (N=8), CTX-M-12 (N=1), CTX-M-57 (N=1), SHV-2a (N=2), SHV-12 (N=17) and TEM-52 (N=4). The qnrA1 and qnrB4 genes were identified in 4 and 7 ESBL-producing isolates, respectively. CONCLUSIONS: CTX-M-type enzymes were the most common type of ESBL in E. coli isolates from Korea, and the qnr genes were not uncommon in ESBL-producing E. coli isolates. Dissemination of E. coli containing both ESBL and qnr genes could compromise the future usefulness of the expanded-spectrum antibiotics for the treatment of infections.
Disk Diffusion Antimicrobial Tests ; Escherichia coli/*enzymology/genetics/isolation & purification ; Escherichia coli Proteins/classification/*genetics ; Humans ; Inhibitory Concentration 50 ; Polymerase Chain Reaction ; beta-Lactamases/biosynthesis/genetics/*metabolism

PURPOSE: Coexistence of different classes of beta-lactamases in a single bacterial isolate may pose diagnostic and therapeutic challenges. We investigated a spread of Klebsiella pneumoniae isolates co-producing an AmpC beta-lactamase and an extended-spectrum beta-lactamase (ESBL) in a university hospital. MATERIALS AND METHODS: Over a three-month period, a total of 11 K. pneumoniae isolates, which exhibited resistance to cefotaxime, aztreonam, and cefoxitin, were isolated. These isolates showed positive to ESBLs by double disk tests. Minimal inhibitory concentrations (MICs) were determined by broth microdilution testing. All isolates were examined by isoelectric focusing, PCR and sequence analysis to identify bla(SHV) and bla(DHA), and molecular typing by pulsed-field gel electrophoresis (PFGE). RESULTS: All 11 isolates were highly resistant (MIC, > or = 128microngram/ml) to ceftazidime, aztreonam, and cefoxitin, while they were susceptible (MIC, < or = 2microngram/ml) to imipenem. The bla(SHV-12) and bla(DHA-1) genes were detected by PCR and sequence analysis. PFGE revealed a similar pattern in 10 of the 11 strains tested. CONCLUSION: This is the first outbreak report of K. pneumoniae in Korea which co-produced SHV-12 and DHA-1 beta-lactamase, and we suggest a clonal spread of multidrug-resistant K. pneumoniae at a hospital.
Adult ; Aged ; Aged, 80 and over ; *Disease Outbreaks ; Disease Susceptibility ; *Drug Resistance, Multiple, Bacterial ; Female ; Genotype ; Hospitals ; Humans ; Klebsiella Infections/*epidemiology/*microbiology ; Klebsiella pneumoniae/classification/*enzymology/genetics/isolation & purification ; Korea ; Male ; Middle Aged ; Phenotype ; beta-Lactamases/*classification/genetics/*metabolism

BACKGROUND: The aim of this study was to compare the BD Phoenix (Beckton Dickinson Diagnostic Systems, USA) extended-spectrum beta-lactamase (ESBL) test with the Clinical and Laboratory Standards Institute (CLSI) ESBL phenotypic confirmatory test by disk diffusion (CLSI ESBL test) in Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca and Proteus mirabilis. METHODS: We tested 224 clinical isolates of E. coli, K. pneumoniae, K. oxytoca and P. mirabilis during May 2006 to March 2007. These isolates were examined by the Phoenix and the CLSI ESBL tests simultaneously. For the isolates showing discordant results between the two tests, boronic acid disk test was performed to differentiate AmpC beta-lactamase and ESBL. RESULTS: Among the 224 clinical isolates, 75 and 79 isolates were positive for ESBL by CLSI ESBL test and Phoenix test, respectively. Having detected 4 more isolates as ESBL-producers, Phoenix test showed a 98.2% agreement with a 100% sensitivity and 97.3% specificity compared with CLSI ESBL test. Among the four false positive isolates, three were AmpC-positive but ESBL-negative. CONCLUSIONS: The BD Phoenix ESBL test was sensitive and specific, and can be used as a rapid and reliable method to detect ESBL production in E. coli, Klebsiella species, and P. mirabilis.
Automation ; Bacterial Proteins/classification/*metabolism ; Disk Diffusion Antimicrobial Tests ; Escherichia coli/drug effects/*enzymology/isolation & purification ; Humans ; Klebsiella/*enzymology ; Klebsiella oxytoca/drug effects/enzymology/isolation & purification ; Klebsiella pneumoniae/drug effects/enzymology/isolation & purification ; *Microbial Sensitivity Tests ; Proteus mirabilis/drug effects/*enzymology/isolation & purification ; Reagent Kits, Diagnostic ; Sensitivity and Specificity ; beta-Lactamases/classification/*metabolism

OBJECTIVETo investigate the prevalence and antibiotic resistance of Shigella isolated from children with diarrhea for the guidance of clinical treatment and prevention and control of bacillary dysentery.

METHODA total of 156 strains of Shigella were isolated from feces of children with diarrhea in Zhejiang Xiaoshan Hospital from January 2008 to December 2010. The antimicrobial resistance of the strains was detected by disk diffusion method and the extended-spectrum beta-lactamases (ESBLs) in these isolates were determined using phenotypic confirmatory test; the isolates of ESBLs producing Shigella sonnei were analyzed by REP-PCR.

RESULTAmong 156 strains of Shigella isolated, the most common groups were Shigella sonnei (130 strains, accounting for 83.3%) and Shigella fleaneri (26 strains, accounting for 16.7%), and 81 (51.9%) strains were identified as ESBLs producers, and the positive rates in 2008, 2009 and 2010 were 32.0%, 41.4% and 59.8%, respectively. The results of antibiotic susceptibility test displayed that the resistance rates of ESBLs producing Shigella to ampicillin, cotrimoxazole, cefotaxime, piperacillin were higher than 90%. However, the resistance rates to cefepime, ceftazidime, levofloxacin and ciprofloxacin were low; The resistance of ESBLs producing strains to piperacillin (100% vs. 77.3%), cefotaxime (100% vs. 0), ceftazidime (14.8% vs. 0), cefepime (28.4% vs. 0), cotrimoxazole (95.1% vs. 86.7%) was significantly higher than that of non-ESBLs producing strains (χ(2) = 20.605, 156.000, 12.037, 24.979, 45.040, respectively; P < 0.05). No isolate was resistant to piperacillin/tazobactam and imipenem. There were 7 genotypes among 74 ESBLs producing Shigella sonnei, respectively type A (50), type B (12), type C (8), type D (1), type E (1), type F (1), and type G (1).

CONCLUSIONThe isolation rate of ESBLs-producing isolate was high in Shigella from pediatric patients with diarrhea, and the number is going up year by year, and these ESBLs producing Shigella sonnei strains in genotype A are dominant in recent years, Piperacillin/tazobactam is the drug of choice for children with ESBLs producing Shigella infection.

Adolescent ; Anti-Bacterial Agents ; pharmacology ; Child ; Child, Preschool ; Diarrhea ; drug therapy ; epidemiology ; microbiology ; Drug Resistance, Multiple, Bacterial ; Feces ; microbiology ; Female ; Genotype ; Humans ; Male ; Microbial Sensitivity Tests ; Molecular Epidemiology ; Penicillanic Acid ; analogs & derivatives ; pharmacology ; Piperacillin ; pharmacology ; Polymerase Chain Reaction ; Sequence Analysis, DNA ; Shigella ; classification ; drug effects ; genetics ; isolation & purification ; beta-Lactamases ; genetics ; metabolism