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We evaluated the clinical significance of the cefazolin inoculum effect (CIE) in methicillin-susceptible Staphylococcus aureus (MSSA) isolates. In total, 146 isolates were recovered from patients with MSSA bacteremia at 9 hospitals in Korea. The CIE was observed in 16 MSSA isolates, and while type A was the only detected β-lactamase in MSSA isolates exhibiting the CIE, no strains expressing type B, C, or D β-lactamases exhibited this effect. The CIE was only observed in agr group III and I isolates and was significantly more common in isolates with agr dysfunction than in those with functional agr ( P < 0.001). Even among isolates producing type A β-lactamase, the CIE was also prevalent in isolates with dysfunctional agr than in isolates with functional agr ( P = 0.025). This study demonstrates an association between the CIE of MSSA isolates and agr dysfunction, in addition to those between the CIE and type A β-lactamase. [ABSTRACT FROM AUTHOR]

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]

Abstract: CALPHAD XXXIX (May 23–28, 2010) was held in Jeju, Korea, organized by Byeong-Joo Lee, Chang-Seok Oh, Joonho Lee, Jae-Hyeok Shim and Hyuck Mo Lee. 125 registered participants presented 73 oral contributions and 52 posters, including 5 invited talks by experimental researchers from various materials research fields in a specially inserted session named “experiments that need thermodynamic analysis”. Poster sessions were held on the evening of Monday and Tuesday. A “Young Calphadian Meeting” was also organized on Tuesday evening after the poster session with A. Pelton, B. Sundman and J. Ågren as invited speakers. There was a conference excursion to the Jeju forkvillage during Wednesday afternoon. The Best Paper Award for papers published in 2009 in the CALPHAD journal and a Best Poster Award for one of the conference’s posters were conferred during the conference dinner on Wednesday evening. The abstracts and titles of oral presentations and titles of poster presentations are summarized in this report. [Copyright &y& Elsevier]

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.

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.