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Abstract: We investigated the characteristics of 48 carbapenem-resistant Acinetobacter baumannii isolates collected from 5 tertiary care hospitals in Korea by multilocus sequencing typing, pulsed-field gel electrophoresis, and polymerase chain reaction amplification of the antimicrobial resistance determinants. We identified 2 distinct main clones of carbapenem-resistant A. baumannii isolates, which showed different antimicrobial resistance profiles and are also differentiated by the kinds of oxacillinase (OXA) carbapenemases and Acinetobacter-derived cephalosporinase (ADC) β-lactamases. One main clone, ST22:A, had 27 carbapenem-resistant isolates (56.3%), showed high polymyxin B and colistin resistances (33.3% and 37.0%, respectively), and contained both bla OXA-51–like and bla OXA-23–like genes and the bla ADC-29 or bla ADC-30 gene. In contrast, the other main clone, ST28:B, included 15 isolates (31.3%), showed complete susceptibilities to polymyxin B and colistin, and contained only the bla OXA-51–like gene and bla ADC-31 or bla ADC-32 genes. The distribution of these main carbapenem-resistant A. baumannii clones did not relate to locality, indicating that they are widespread in Korean hospitals. In addition, we found new types of PER β-lactamases, PER-6. [Copyright &y& Elsevier]

Recent changes in healthcare systems have changed the epidemiologic paradigms in many infectious fields including bloodstream infection (BSI). We compared clinical characteristics of community-acquired (CA), hospital-acquired (HA), and healthcare-associated (HCA) BSI. We performed a prospective nationwide multicenter surveillance study from 9 university hospitals in Korea. Total 1,605 blood isolates were collected from 2006 to 2007, and 1,144 isolates were considered true pathogens. HA-BSI accounted for 48.8%, CA-BSI for 33.2%, and HCA-BSI for 18.0%. HA-BSI and HCA-BSI were more likely to have severe comorbidities. Escherichia coli was the most common isolate in CA-BSI (47.1%) and HCA-BSI (27.2%). In contrast, Staphylococcus aureus (15.2%), coagulase-negative Staphylococcus (15.1%) were the common isolates in HA-BSI. The rate of appropriate empiric antimicrobial therapy was the highest in CA-BSI (89.0%) followed by HCA-BSI (76.4%), and HA-BSI (75.0%). The 30-day mortality rate was the highest in HA-BSI (23.0%) followed by HCA-BSI (18.4%), and CA-BSI (10.2%). High Pitt score and inappropriate empirical antibiotic therapy were the independent risk factors for mortality by multivariate analysis. In conclusion, the present data suggest that clinical features, outcome, and microbiologic features of causative pathogens vary by origin of BSI. Especially, HCA-BSI shows unique clinical characteristics, which should be considered a distinct category for more appropriate antibiotic treatment.

To investigate the antimicrobial resistance, extended-spectrum beta-lactamases (ESBLs) and clones of Klebsiella pneumoniae isolates causing bacteraemia or urinary tract infection (UTI) in Korea, a total of 406 K. pneumoniae isolates from patients with bacteraemia (221 isolates) and UTI (185 isolates) were collected from 10 tertiary-care Korean hospitals from July 2006 to October 2007. In vitro antimicrobial susceptibility testing was performed for all isolates and ESBL production was tested. Multilocus sequence typing (MLST) analyses were performed to characterize genotypes of ESBL-producing K. pneumoniae isolates. PFGE was performed for sequence type 11 (ST11) isolates. Forty-seven UTI isolates (25.4 %) produced ESBLs, while 30 bacteraemia isolates (13.6 %) produced ESBLs (P=0.002). Among 77 ESBL-producing isolates, thirty-two (41.6 %) produced SHV-type ESBLs. bla(CTX-M) genes such as bla(CTX-M-14) and bla(CTX-M-15) were detected in 36.4 %. MLST and PFGE analyses showed that ST11 was dominant in ESBL-producing K. pneumoniae isolates causing UTI (57.4 %) and in those causing bacteraemia (70.0 %) and has been prevalent in Korean hospitals. ST11 isolates harbour a combination of different ESBL genes. The ST11 clone of ESBL-producing K. pneumoniae isolates prevails in Korea, but most isolates might acquire ESBL genes independently or several different clones might be distributed in Korea.

Seventy-three liver abscess isolates of serotype K1 Klebsiella pneumoniae from a nationwide collection in Korea were genotypically characterized using pulsed-field gel electrophoresis and multilocus sequence typing. We found that serotype K1 K. pneumoniae strains that caused liver abscesses in Korea were genotypically related and that most were sequence type 23.

Prevalence and characteristics of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in Korean hospitals were assessed. A total of 1484 clinical Enterobacteriaceae isolates were collected from 8 tertiary-care hospitals in various regions of Korea over a 3-month period (June to August) in 2005. Among 546 Klebsiella pneumoniae isolates, 123 isolates (22.4%) showed ESBL-producing activity, and 47 (10.2%) of 460 isolates of Escherichia coli were ESBL producers. Of the Enterobacter cloacae isolates, 16.2% (17/105) evidenced ESBL-producing activity. The most prevalent ESBLs were SHV-12 and CTX-M-14 in K. pneumoniae and E. coli, respectively. In E. cloacae, SHV-12 was also the most prevalent. Prevalence of ESBL production differed among the specimens. Although the K. pneumoniae isolates from urine and aspirates evidenced high ESBL production rates (35.4% and 57.1%, respectively), those from sputum, blood, and pus showed relatively low ESBL production rates (17.0%, 14.8%, and 5.3%, respectively). However, E. coli isolates obtained from sputum showed significantly higher ESBL production rates (37.5%) than were seen in samples obtained from other sources, but those obtained from urine showed lower ESBL production rates (8.3%). These significant differences in ESBL-producing K. pneumoniae and E. coli isolates among the isolated specimens should be examined further, with an eye toward the implications of this research in clinical settings.

Objectives: To analyse the risk factors for nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infections caused by different clonal types., Methods: A total of 134 non-duplicate nosocomial MRSA isolates were analysed for clonal types by molecular typing techniques. The medical records of 90 patients who had documented MRSA infection were evaluated retrospectively., Results: Two predominant MRSA clones of sequence types (STs) ST239 (n = 75) and ST5 (n = 39) accounted for 85% of the isolates. Management of patients in the departments of orthopaedic surgery, neurosurgery and plastic surgery was identified as a risk factor for infection with MRSA of ST239, while the presence of intravascular catheters was a risk factor for infection with ST5. Pulmonary infection was significantly higher in the patients infected with ST239 strains than in the patients infected with ST5 strains (P < 0.05). The overall mean duration of antimicrobial therapy for the patients with ST239 infection was significantly more than that for the patients with ST5 infection (P < 0.05)., Conclusions: ST239 and ST5 were the predominant MRSA clones in the study hospital. Risk factors were significantly different between ST239 and ST5 strains. The results of this study will be of use in designing larger prospective epidemiological studies for MRSA infection based on clonal types.

We tested the in vitro susceptibilities of 603 enterococcal isolates from eight tertiary-care hospitals in Korea. The quinupristin-dalfopristin resistance rate in Enterococcus faecium was very high (25 isolates, 10.0%). It was suggested that both clonal spread and the sporadic emergence of quinupristin-dalfopristin-resistant isolates may explain the high prevalence of quinupristin-dalfopristin resistance in Korea.

Ninety-six methicillin-resistant Staphylococcus aureus (MRSA) isolates from eight Korean hospitals were analyzed by multilocus sequence typing, SCCmec typing, and spa typing. The predominant genotype was ST5-MRSA-II of clonal complex 5, which was found in 36 isolates from six hospitals, but ST239-MRSA-III was also common. Overall, results showed a notable genotypic diversity of MRSA strains circulating in Korean hospitals.

pbp2b gene alterations were analyzed in 102 clinical isolates of Streptococcus pneumoniae (30 penicillin susceptible, 23 intermediate, and 49 resistant) from Korea. On the basis of PBP2B amino acid sequences, penicillin-nonsusceptible isolates of S. pneumoniae belonged to six groups, and 76% of the isolates in groups I to IV showed the same divergent block of amino acid alterations. Thirteen isolates (group II) also possessed a divergent block that was identical to that of Streptococcus oralis. The pbp2b genes of most Korean isolates showed novel mosaic mutations due to horizontal gene transfer. The Thr252 --> Ala substitution, previously thought to be associated only with penicillin-nonsusceptible strains, was also found in three penicillin-susceptible strains. On the basis of their pbp2b nucleotide sequences, all penicillin-nonsusceptible isolates can be detected by multiplex PCR, which can be used as a novel method for detection of antibiotic-resistant pneumococcal strains in clinical specimens.

Background: Human immunodeficiency virus (HIV) infection results in a selective CD4+ T cell depletion and an impairment of T cell regulation. Despite the immune depletion, the progression of HIV infection is accompanied by the stimulation of antibody synthesis. Thus, the prevalence and amplitude of the increase of total serum IgE level and the relationship between the IgE levels and the degree of immunodeficiency were evaluated in patients with HIV infection., Method: Twenty-six Korean adults infected with HIV, in different stages, were evaluated for serum IgE level and CD4+ T cell count. Serum IgG, IgM and IgA levels were also determined. All subjects enrolled in this study denied an individual and familial history of atopic diseases. The possibility of parasitic infestation was also excluded by history and stool examination., Results: The mean serum IgE level was 473.5 IU/L with a standard deviation of 671.4 IU/L (range: 15.9-2000 IU/L) and increased serum IgE levels (> 200 IU/L) were found in 38.5% of the study population. The mean serum IgG, IgA and IgM levels were 1,939.5 +/- 588.6 mg/dL (normal: 751-1,560 mg/dL), 388.9 +/- 216.7 mg/dL (normal: 82-453 mg/dL) and 153.6 +/- 75.3 mg/dL (normal: 46-304 mg/dL), respectively. The CD4+ T cell count was inversely correlated to the serum IgE level (r = -0.429, p < 0.05), but not to the other isotypes of immunoglobulin., Conclusion: Serum IgE levels are increased in adults with HIV infection and could be useful as a marker of disease progression. Further study is needed to elucidate the causes and clinical significance of these findings.