Multiplex PCR for Rapid Detection of Genes Encoding Class A Carbapenemases

In recent years, there have been increasing reports of KPC-producing Klebsiella pneumoniae in Korea. The modified Hodge test can be used as a phenotypic screening test for class A carbapenamase (CAC)-producing clinical isolates; however, it does not distinguish between carbapenemase types. The confirmation of type of CAC is important to ensure optimal therapy and to prevent transmission. This study applied a novel multiplex PCR assay to detect and differentiate CAC genes in a single reaction. Four primer pairs were designed to amplify fragments encoding 4 CAC families (SME, IMI/NMC-A, KPC, and GES). The multiplex PCR detected all genes tested for 4 CAC families that could be differentiated by fragment size according to gene type. This multiplex PCR offers a simple and useful approach for detecting and distinguishing CAC genes in carbapenem-resistant strains that are metallo-beta-lactamase nonproducers.

The Evaluation of Integrated Test as an Antenatal Screening Test for Down's Syndrome in Korea

BACKGROUND: Antenatal screening for Down's syndrome has been developed and improved over the past 20 yr. Recently, integrated test, which combines the first and second trimester markers has shown the highest detection rate (DR) and lowest false positive rate (FPR) among Down's syndrome screening tests currently in use. The purposes of this study were to evaluate the screening performance of integrated test and to compare the results with triple test studies in Korea. METHODS: The study population consisted of Korean pregnant women who underwent triple or integrated test between April 2005 and December 2008. Triple test was performed using measurements of alpha-fetoprotein (AFP), unconjugated estriol (uE3), and human chorionic gonadotropin (hCG) in the second trimester. Integrated test was performed using nuchal translucency (NT) by ultrasonography and pregnancy-associated plasma protein A (PAPP-A) from maternal serum in the first trimester, and AFP, uE3, hCG, and inhibin-A in the second trimester. The screening performance of each test was evaluated by DR and FPR. RESULTS: Twenty-seven Down's syndrome pregnancies were confirmed in women screened by triple (N=6,736) or integrated test (N=7,688). At 1:100, 1:270, and 1:300 of risk cutoff, triple test showed 45%, 73%, and 73% of DR and 4.7%, 11.2%, and 12.4% of FPR, respectively. At 1:100, 1:150, and 1:300 of risk cutoff, integrated test showed 63%, 69%, and 75% of DR and 1.5%, 1.9%, and 3.0% of FPR, respectively. CONCLUSIONS: Integrated test showed higher DR and lower FPR, demonstrating better screening performance than triple test.

Comparison of 3 Phenotypic-detection Methods for Identifying Plasmid-mediated AmpC beta-lactamase-producing Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis Strains / 대한진단검사의학회지

BACKGROUND: Plasmid-mediated AmpC beta-lactamases (PABLs) have been detected in the strains of Escherichia coli, Klebsiella spp., Proteus mirabilis, and Salmonella spp. PABLs may be difficult to detect and might interfere in the therapeutic and infection-control processes. Although several PABL-detection methods based on phenotypes have been reported, the Clinical and Laboratory Standards Institute currently does not recommend a routine detection method for PABLs. The aim of this study is to compare the performances of 3 phenotypic PABL detection methods. METHODS: Total 276 non-duplicated clinical isolates of E. coli (N=97), K. pneumoniae (N=136), and P. mirabilis (N=43) were collected from 14 hospitals in Korea between April and June 2007 in a non-consecutive and non-random manner. Multiplex PCR was performed to detect the PABL genes. Further, 3 phenotypic detection methods-cephamycin-Hodge test, Tris-EDTA (TE) disk test, and combination-disk test with 3-aminophenylboronic acid (BA)-were performed using cefoxitin and cefotetan disks. RESULTS: PABL genes were detected by multiplex PCR in 122/276 isolates, including 14/97 E. coli, 105/136 K. pneumoniae, and 3/43 P. mirabilis isolates. The combination-disk test with BA showed higher sensitivity (98.4%), specificity (92.2%), and efficiency (96.3%) than the cephamycin-Hodge (76.2%, 96.1%, and 88.6%, respectively) and the TE-disk (80.3%, 91.6%, and 87.9%, respectively) tests. CONCLUSIONS: The combination-disk test with BA is a simple, efficient, and interpretable test that can be applicable in clinical laboratories involved in the detection of PABLs in clinical isolates of E. coli, K. pneumoniae, and P. mirabilis.

Two Cases of Independent Infection by Leclercia adecarboxylata / 감염과화학요법

Leclercia adecarboxylata is a facultative gram negative bacillus of the Enterobacteriaceae family. It has been previously reported as a rarely isolated opportunistic pathogen, mainly in the form of mixed infection with other organisms. We report two cases of independent infection by L. adecarboxylata. One strain of L. adecarboxylata was isolated from Baker's cyst in an immunocompetent patient and the other strain from dialysate in a patient on continuous ambulatory peritoneal dialysis.

Two Cases of Independent Infection by Leclercia adecarboxylata / 감염과화학요법

Leclercia adecarboxylata is a facultative gram negative bacillus of the Enterobacteriaceae family. It has been previously reported as a rarely isolated opportunistic pathogen, mainly in the form of mixed infection with other organisms. We report two cases of independent infection by L. adecarboxylata. One strain of L. adecarboxylata was isolated from Baker's cyst in an immunocompetent patient and the other strain from dialysate in a patient on continuous ambulatory peritoneal dialysis.