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A chloramphenicol-resistant strain of Salmonella enterica serovar Typhi was first noted in Korea in 1992, when a resistant isolate was detected in a returned traveler. Continued isolation of multidrug-resistant (MDR) strains thereafter in other settings prompted a retrospective analysis of laboratory records and phenotypic and genotypic analyses of 12 chloramphenicol-resistant isolates. Among these, one isolate was resistant only to chloramphenicol, and the other isolates were also resistant to ampicillin and co-trimoxazole. MDR was transferred by conjugation from 9 of the 11 isolates. PCR showed that all isolates had an incompatible group HI1 plasmid, and oriT was detected in 10 isolates, which included strains with an unsuccessful transfer of resistance. All of the ampicillin-resistant isolates had a beta-lactamase band of pI 5.4 and bla(TEM) alleles. A PCR amplicon from an isolate showed that the sequences were identical to those of bla(TEM-1), suggesting that all isolates had a TEM-1 beta-lactamase. All isolates had class 1 integrons: 10 isolates had integrons of ca. 1.2 kb with dhfr7 gene cassettes, and 1 isolate had an integron of ca. 2.3 kb with aacA4 and bla(OXA-1)-like gene cassettes. The pulsed-field gel electrophoresis patterns of 7 of 11 MDR isolates were identical and indistinguishable from those reported for isolates in India and Indonesia. In conclusion, some of the MDR strains in Korea are related to those in other Asian countries. Susceptibility testing became necessary for selection of antimicrobial agents for the optimal treatment of patients with the emergence of MDR Salmonella serovar Typhi in Korea.

Metallo-beta-lactamase (MBL)-producing Pseudomonas spp. and Acinetobacter spp. were prevalent in Korean hospitals. In this study, the prevalence and presence of MBL-producing isolates among imipenem-nonsusceptible and imipenem-susceptible isolates, respectively, were screened. The genetic and phenotypic characteristics of MBL-producing isolates were determined. Among imipenem-nonsusceptible isolates, 52 (11.1%) of 467 Pseudomonas spp. were blaVIM-like allele-positive, and 33 (15.1%) of 218 Acinetobacter spp. were either blaVIM- or blaIMP-like allele-positive. One blaVIM-like allele-positive isolate of Acinetobacter spp. was detected among 84 imipenem-susceptible Acinetobacter isolates. The minimum inhibitory concentration for 90% of isolates of imipenem was higher (>128 microg/mL) for Pseudomonas spp. than Acinetobacter spp. (16 microg/mL), although both had blaVIM-like allele. The source of MBL-producing isolates was mostly the sputum and urine of patients in the intensive care unit. Pulsed-field gel electrophoresis analysis suggested the intra- and inter-hospital spread of MBL-producing strains at some hospitals. In conclusion, blaVIM-like allele-positive P. aeruginosa remained highly prevalent, and the proportion of blaIMP-like allele-positive Acinetobacter spp. has increased significantly in most Korean hospitals.

Continued antimicrobial resistance surveillance can provide valuable information for the empirical selection of antimicrobial agents for patient treatment, and for resistance control. In this 6th annual study for 2002, the susceptibility data at 39 Korean Nationwide Surveillance of Antimicrobial Resistance (KONSAR) hospitals were analyzed. Resistance rates of S. aureus were 67% to oxacillin, and 58% to clindamycin. The ampicillin and vancomycin resistance rates of E. faecium were 89% and 16%, respectively. To penicillin, 71% of S. pneumoniae were nonsusceptible. Resistance rates of E. coli were 11% to cefotaxime, 8% to cefoxitin, and 34% to fluoroquinolone, and those of K. pneumoniae were 22% to ceftazidime, and 16% to cefoxitin. Lowest resistance rates to cephalosporins shown by E. cloacae and S. marcescens were to cefepime, 7% and 17%, respectively. This is the first KONSAR surveillance, which detected imipenem-resistant E. coli and K. pneumoniae. To imipenem, 22% of P. aeruginosa and 9% of Acinetobacter spp. were resistant. Trends of resistances showed a slight reduction in MRSA and in penicillin- nonsusceptible S. pneumoniae, but an increase in ampicillin-resistant E. faecium. Ampicillin-resistant E. coli and H. influenzae remained prevalent. Compared to the previous study, amikacin- and fluoroquinolone- resistant Acinetobacter spp. increased to 60% and 62%, respectively. Ceftazidime- resistant K. pneumoniae decreased slightly, and imipenem- resistant P. aeruginosa and Acinetobacter spp., and vancomycin-resistant E. faecium increased. In conclusion, vancomycin-resistant E. faecium, cefoxitin-resistant E. coli and K. pneumoniae, and imipenem-resistant P. aeruginosa and Acinetobacter spp. increased gradually, and imipenem- resistant E. coli and K. pneumoniae appeared for the first time. Continued surveillance is required to prevent further spread of these serious resistances.

Objectives: This study was performed to examine the cause of the increase in quinolone-resistant Neisseria gonorrhoeae (QRNG) observed in Korea., Methods: The antimicrobial susceptibilities of 190 isolates of gonococci from Korea in 2000 were examined by NCCLS methods, and subsets of these isolates underwent mutation analysis of the quinolone resistance-determining regions (QRDRs) of gyrA and parC. Molecular epidemiological characterization of 25 Korean isolates and 54 isolates from overseas was performed by pulsed-field gel electrophoresis (PFGE) and the results compared., Results: Most (172, 90.5%) of the 190 gonococci tested displayed reduced susceptibility to ciprofloxacin. All strains with high-level ciprofloxacin resistance (ciprofloxacin MIC >/= 4 mg/L) contained a double amino acid alteration at the 91 and 95 positions in the QRDR of GyrA and a single alteration in ParC. PFGE types of high-level QRNG in Korea were mostly different from those of other nearby countries., Conclusions: These results suggest that the observed increase in ciprofloxacin-resistant isolates is due to the mutation and spread of Korean multiclonal isolates rather than importation from overseas.

The 5th year KONSAR surveillance in 2001 was based on routine test data at 30 participating hospitals. It was of particular interest to find a trend in the resistances of enterococci to vancomycin, of Enterobacteriaceae to the 3rd generation cephalosporin and fluoroquinolone, and of Pseudomonas aeruginosa and acinetobacters to carbapenem. Resistance rates of Gram-positive cocci were: 70% of Staphylococcus aureus to oxacillin; 88% and 16% of Enterococcus faecium to ampicillin and vancomycin, respectively. Seventy-two percent of pneumococci were nonsusceptible to penicillin. The resistance rates of Enterobacteriaceae were: Escherichia coli, 28% to fluoroquinolone; Klebsiella pneumoniae, 27% to ceftazidime, and 20% to cefoxitin; and Enterobacter cloacae, > or =40% to cefotaxime and ceftazidime. The resistance rates of P. aeruginosa were 21% to ceftazidime, 17% to imipenem, and those of the acinetobacters were > or =61% to ceftazidime, aminoglycosides, fluoroquinolone and cotrimoxazole. Thirty-five percent of non-typhoidal salmonellae were ampicillin resistant, and 66% of Haemophilus influenzae were beta-lactamase producers. Notable changes over the 1997-2001 period were: increases in vancomycin-resistant E. faecium, and amikacin- and fluoroquinolone-resistant acinetobacters. With the increasing prevalence of resistant bacteria, nationwide surveillance has become more important for optimal patient management, for the control of nosocomial infection, and for the conservation of the newer antimicrobial agents.

In vitro activities of DA-7867, a novel oxazolidinone, were compared to those of linezolid and commonly used antimicrobials. DA-7867 had the lowest MIC for 90% of the aerobic gram-positive bacterial strains tested,

We determined the occurrence of acquired metallo-b-lactamase (MBL)-producing bacteria in Korean hospitals. Among the isolates nonsusceptible to imipenem that were collected from 28 hospitals from 2000 to 2001, 44 (11.4%) of 387 Pseudomonas spp. and 38 (14.2%) of 267 Acinetobacter spp. produced MBL and had alleles of blaVIM-2 or blaIMP-1. MBL-producing isolates were detected in 60.7% of the hospitals.

PER-1, an extended-spectrum beta-lactamase, has been reported only in Europe. We detected PER-1 in 53 of 97 acinetobacters in Korea, mainly in the sputum of intensive care unit patients. Pulsed-field gel electrophoresis analysis suggested that clonal spread had occurred. Only PCR reliably detected PER-1 producers. PER-1 producers may also exist in other Asian countries.

A sudden increase in vancomycin-resistant enterococci (VRE) infections was noted in 1998 in a tertiary care hospital in Korea. All of the VRE isolated in 1998 in the hospital were VanA type and most were multidrug-resistant Enterococcus faecium. The increase in VRE was probably due to the increased use of oral vancomycin to treat Clostridium difficile infections and clonal as well as horizontal spread. More restricted oral vancomycin use and stricter infection control measures are required to achieve a better control of the spread of VRE.

Cefoxitin-resistant Escherichia coli and Klebsiella pneumoniae are widespread in Korea. Significant proportions of them are considered to be CMY-1 producers. For effective screening of CMY-1 producers, the Hodge test was modified by using a cefoxitin disk and the performance was evaluated. The sensitivity and specifity of the test were 100% and 94.9%, respectively. The test was easier to perform than the three-dimensional extract test. This modified test should be suitable for screening CMY-1-producing strains of E. coli and K. pneumoniae., (Copyright 2002 Elsevier Science B.V.)

Rapid detection of metallo-beta-lactamase (MBL)-producing gram-negative bacilli is necessary to prevent their dissemination. The method using a disk with imipenem plus 750 micro g of EDTA differentiated all MBL-producing pseudomonads, and the sensitivity and specificity for acinetobacters were 95.7 and 91.0%, respectively. The imipenem-EDTA disks were stable for 12 and 16 weeks at 4 and -20 degrees C, respectively.

Serratia marcescens is an important nosocomial pathogen which is often resistant to multiple antimicrobial agents. An imipenem-resistant S. marcescens isolate from a urine specimen was found to carry a bla(VIM-2) gene cassette on a class 1 integron. This finding indicates that bla(VIM-2) is presently spreading even to Serratia spp. in Korea, which could compromise the usefulness of carbapenem in the treatment of multi-resistant Gram-negative bacilli infections. Clinical laboratory should be able to detect the VIM-2-producing isolates with even low carbapenem MIC.

To investigate the prevalence of resistance to macrolide, lincosamide and streptogramin (MLS) antibiotics in Gram-positive cocci isolated in a Korean hospital, we tested the antibiotic susceptibility of 1097 clinical isolates of Staphylococcus aureus, coagulase-negative staphylococci (CNS) and enterococci to the macrolides erythromycin, clarithromycin, azithromycin and josamycin, the lincosamide clindamycin and the streptogramin pristinamycin. These three groups of organisms were mostly resistant to macrolides and lincosamide, but were commonly susceptible to pristinamycin. The resistance phenotypes of erythromycin-resistant isolates were determined by the double-disc test with erythromycin and clindamycin, which showed that most exhibited constitutive MLS resistance. In order to determine the prevalence of the resistance genotypes and the resistance mechanisms, the presence of the erm(A), erm(B), erm(C) and mef genes in the erythromycin-resistant isolates was identified by PCR analysis. The resistance was due mainly to the presence of erm(A) in S. aureus (82.5%), erm(B) in enterococci (55%) and erm(C) in CNS (47.2%).