Serotyping and Antimicrobial Susceptibility of Salmonella Isolated in Korea in 2015 / 대한임상미생물학회지

BACKGROUND: Salmonella is an important pathogen that causes gastroenteritis and sepsis in humans. Recently, changes in serotype prevalence and an increase in antimicrobial resistance have been reported. This study investigated the distribution of Salmonella serotypes and determined the antimicrobial susceptibility of various strains. METHODS: We collected 113 Salmonella isolates other than Salmonella serotype Typhi from 18 university hospitals in 2015. The serotypes were identified by Salmonella antisera O and H according to the Kauffman White scheme. Antimicrobial susceptibility tests for 12 antibiotics were performed using the disk diffusion method or E-test. RESULTS: We identified 22 serotypes. Serotype group B (44.2%) was the most common, followed by groups C (34.5%) and D (21.2%). Salmonella I 4,[5],12:i:- (23.0%), S. Enteritidis (16.8%), and S. Typhimurium (12.4%) were the most common species. Resistance rates for ampicillin, chloramphenicol, ceftriaxone, and trimethoprim/sulfamethoxazole were 46.9%, 18.5%, 8.8%, and 5.3%, respectively. The intermediate resistance rate to ciprofloxacin was 29.2%. Six isolates were extended-spectrum β-lactamase (ESBL) producers, including 5 bla(CTX-M-15) and 1 bla(CTX-M-55). CONCLUSION: There have been changes in the serotype prevalence and antimicrobial resistance of Salmonella in Korea, with a high prevalence of CTX-M 15-positive strains. Continuous monitoring of Salmonella serotypes and antimicrobial resistance is warranted.

Diagnostic Accuracy and Detection Rate of Real-Time PCR for Detection of Group B Streptococcal Colonization in Pregnant Women: Systemic Review of Literature and Meta-Analysis / 대한임상미생물학회지

BACKGROUND: Group B streptococcus (Streptococcus agalactiae, GBS) was reported as a major cause of neonatal infection and death. To prevent vertical transmission, CDC recommended that all women in week 35-37 of pregnancy should receive the GBS colonization test. We conducted a systematic review and meta-analysis to evaluate diagnostic accuracy and detection rate of real-time PCR for GBS in pregnant women. METHODS: The literature review for GBS using real-time PCR was done including KoreaMed, Ovid-MEDLINE, Ovid-EMBASE, and Cochrane Library on November 3, 2015. 443 articles were collected. Two authors select articles and evaluated the quality of studies using Scottish Intercollegiate Guidelines Network tool independently. RESULTS: Diagnostic accuracy of the real-time PCR was assessed by meta-analysis through 34 articles (13,516 for real-time PCR, 1,815 for culture and other comparison test). The GBS colonization was assessed through 34 articles, which reported varying values of 2.0–69.2% using real-time PCR. The real-time PCR for GBS was shown to have overall sensitivity of 0.93 (95% CI 0.92–0.94, I2=86.3%), overall specificity of 0.96 (95% CI 0.96–0.96, I2=90.2%), SROC AUC of 0.99. CONCLUSION: Real-time PCR is an effective test for detecting GBS colonization in pregnant women, resulted in preventing the infection in a new born baby.

In Vitro Synergistic Effects of Antimicrobial Combinations on Extensively Drug-Resistant Pseudomonas aeruginosa and Acinetobacter baumannii Isolates

BACKGROUND: Extensively drug-resistant (XDR) Pseudomonas aeruginosa and Acinetobacter baumannii are a threat to hospitalized patients. We evaluated the effects of antimicrobial combinations on XDR P. aeruginosa and A. baumannii isolates. METHODS: P. aeruginosa and A. baumannii isolates, which were resistant to all antibiotics except colistin (CL), were collected from eight hospitals in Korea. Genes encoding metallo-beta-lactamases (MBLs) and OXA carbapenemases were detected by PCR in eight P. aeruginosa and 30 A. baumannii isolates. In vitro synergy of antimicrobial combinations was tested by using the checkerboard method. RESULTS: Minimum inhibitory concentrations of beta-lactams, aminoglycosides, and fluoroquinolones were very high, while that of CL was low for majority of XDR P. aeruginosa and A. baumannii isolates. Antimicrobial combinations including Imipenem (IPM)-CL, ceftazidime (CAZ)-CL, and rifampin (RIF)-CL exerted only additive/indifferent effects on majority of XDR P. aeruginosa isolates. Proportions of XDR A. baumannii isolates that showed synergistic and additive/indifferent inhibition after treatment with antimicrobial combinations used are as follows: IPM-ampicillin-sulbactam (AMS), 17% and 80% isolates, respectively; IPM-rifampin (RIF), 13% and 81% isolates, respectively; IPM-CL, 13% and 87% isolates, respectively; and RIF-COL, 20% and 73% isolates, respectively. Significant proportion (19%) of XDR P. aeruginosa isolates produced MBLs, and majority (82%) of A. baumannii isolates produced either MBLs or OXA-23. CONCLUSIONS: Our results suggest that combinations of IPM-AMS, IPM-RIF, IPM-CL, and RIF-CL are more useful than individual drugs for treating 13-20% of XDR A. baumannii infections.

Establishing Quality Control Ranges for Antimicrobial Susceptibility Testing of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus: A Cornerstone to Develop Reference Strains for Korean Clinical Microbiology Laboratories

Quality control (QC) processes are being performed in the majority of clinical microbiology laboratories to ensure the performance of microbial identification and antimicrobial susceptibility testing by using ATCC strains. To obtain these ATCC strains, some inconveniences are encountered concerning the purchase cost of the strains and the shipping time required. This study was focused on constructing a database of reference strains for QC processes using domestic bacterial strains, concentrating primarily on antimicrobial susceptibility testing. Three strains (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) that showed legible results in preliminary testing were selected. The minimal inhibitory concentrations (MICs) and zone diameters (ZDs) of eight antimicrobials for each strain were determined according to the CLSI M23. All resulting MIC and ZD ranges included at least 95% of the data. The ZD QC ranges obtained by using the CLSI method were less than 12 mm, and the MIC QC ranges extended no more than five dilutions. This study is a preliminary attempt to construct a bank of Korean QC strains. With further studies, a positive outcome toward cost and time reduction can be anticipated.

Combined Use of the Modified Hodge Test and Carbapenemase Inhibition Test for Detection of Carbapenemase-Producing Enterobacteriaceae and Metallo-beta-Lactamase-Producing Pseudomonas spp

BACKGROUND: We evaluated the combined use of the modified Hodge test (MHT) and carbapenemase inhibition test (CIT) using phenylboronic acid (PBA) and EDTA to detect carbapenemase-producing Enterobacteriaceae (CPE) and metallo-beta-lactamase (MBL)-producing Pseudomonas spp. METHODS: A total of 49 isolates of CPE (15 Klebsiella pneumoniae carbapenemase [KPC], 5 Guiana extended-spectrum beta-lactamase [GES]-5, 9 New Delhi metallo-beta-lactamase [NDM]-1, 5 Verona integron-encoded metallo-beta-lactamase [VIM]-2, 3 imipenem-hydrolyzing beta-lactamase [IMP], and 12 oxacillinase [OXA]-48-like), 25 isolates of MBL-producing Pseudomonas spp. (14 VIM-2 and 11 IMP), and 35 carbapenemase-negative controls were included. The MHT was performed for all isolates as recommended by the Clinical and Laboratory Standards Institute. Enhanced growth of the indicator strain was measured in mm with a ruler. The CIT was performed by directly dripping PBA and EDTA solutions onto carbapenem disks that were placed on Mueller-Hinton agar plates seeded with the test strain. RESULTS: Considering the results of the MHT with the ertapenem disk in Enterobacteriaceae and Pseudomonas spp., the CIT with the meropenem disk in Enterobacteriaceae, and the imipenem disk in Pseudomonas spp., three combined disk tests, namely MHT-positive plus PBA-positive, EDTA-positive, and MHT-positive plus PBA-negative plus EDTA-negative, had excellent sensitivity and specificity for the detection of KPC- (100% sensitivity and 100% specificity), MBL- (94% sensitivity and 100% specificity), and OXA-48-like-producing isolates (100% sensitivity and 100% specificity), respectively. CONCLUSIONS: Combined use of the MHT and CIT with PBA and EDTA, for the detection of CPE and MBL-producing Pseudomonas spp., is effective in detecting and characterizing carbapenemases in routine laboratories.

The sul1 Gene in Stenotrophomonas maltophilia With High-Level Resistance to Trimethoprim/Sulfamethoxazole

Emerging resistance to trimethoprim/sulfamethoxazole (SXT) poses a serious threat to the treatment of Stenotrophomonas maltophilia infections. We determined the prevalence and molecular characteristics of acquired SXT resistance in recent clinical S. maltophilia isolates obtained from Korea. A total of 252 clinical isolates of S. maltophilia were collected from 10 university hospitals in Korea between 2009 and 2010. Antimicrobial susceptibility was determined by using the CLSI agar dilution method. The sul1, sul2, and sul3 genes, integrons, insertion sequence common region (ISCR) elements, and dfrA genes were detected using PCR. The presence of the sul1 gene and integrons was confirmed through sequence analysis. Among the 32 SXT-resistant isolates, sul1 was detected in 23 isolates (72%), all of which demonstrated high-level resistance (> or =64 mg/L) to SXT. The sul1 gene (varying in size and structure) was linked to class 1 integrons in 15 of the 23 isolates (65%) harboring this gene. None of the SXT-susceptible isolates or the SXT-resistant isolates with a minimum inhibitory concentration of 4 and 8 mg/L were positive for sul1. Moreover, the sul2, sul3, and dfrA genes or the ISCR elements were not detected. The sul1 gene may play an important role in the high-level SXT resistance observed in S. maltophilia.

A Novel Cytosolic Isoform of Mitochondrial Trans-2-Enoyl-CoA Reductase Enhances Peroxisome Proliferator-Activated Receptor alpha Activity

BACKGROUND: Mitochondrial trans-2-enoyl-CoA reductase (MECR) is involved in mitochondrial synthesis of fatty acids and is highly expressed in mitochondria. MECR is also known as nuclear receptor binding factor-1, which was originally reported with yeast two-hybrid screening as a binding protein of the nuclear hormone receptor peroxisome proliferator-activated receptor alpha (PPARalpha). However, MECR and PPARalpha are localized at different compartment, mitochondria, and the nucleus, respectively. Therefore, the presence of a cytosolic or nuclear isoform of MECR is necessary for functional interaction between MECR and PPARalpha. METHODS: To identify the expression pattern of MECR and the cytosolic form of MECR (cMECR), we performed reverse transcription polymerase chain reaction (RT-PCR) with various tissue samples from Sprague-Dawley rats. To confirm the interaction between cMECR and PPARalpha, we performed several binding assays such as yeast two-hybrid, coimmunoprecipitation, and bimolecular fluorescence complementation. To observe subcellular localization of these proteins, immunocytochemistry was performed. A luciferase assay was used to measure PPARalpha activity. RESULTS: We provide evidence of an alternatively spliced variant of the rat MECR gene that yields cMECR. The cMECR lacks the N-terminal 76 amino acids of MECR and shows uniform distribution in the cytoplasm and nucleus of HeLa cells. cMECR directly bound PPARalpha in the nucleus and increased PPARalpha-dependent luciferase activity in HeLa cells. CONCLUSION: We found the cytosolic form of MECR (cMECR) was expressed in the cytosolic and/or nuclear region, directly binds with PPARalpha, and enhances PPARalpha activity.

Recent Trends in Antimicrobial Resistance in Intensive Care Units in Korea / 병원감염관리

BACKGROUND: In general, higher resistance rates are observed among intensive care unit (ICU) isolates than non-ICU isolates. In this study, resistance rates of isolates from ICUs and non-ICUs were compared using the data generated from 20 hospitals in Korea. METHODS: Susceptibility data were collected from 20 hospitals participating in the Korean Nationwide Surveillance of Antimicrobial Resistance (KONSAR) program. Duplicate isolates were excluded from the analysis. The resistance rates did not include intermediate susceptibility. RESULTS: The most prevalent bacteria in the ICUs were Staphylococcus aureus (21%) and Acinetobacter spp. (19%), and those in non-ICU were Escherichia coli (27%) and S. aureus (14%). The resistance rates were higher in ICUs than in non-ICUs at 84% and 58% for methicillin-resistant S. aureus, 86% and 70% for methicillin-resistant coagulase-negative Staphylcoccus (CNS), 34% and 19% for vancomycin-resistant Enterococcus faecium, 38% and 19% for cefotaxime-resistant E. coli, 45% and 25% for cefotaxime-resistant Klebsiella pneumoniae, 42% and 24% for ceftazidime-resistant Enterobacter cloacae, 29% and 11% for ceftazidime-resistant Serattia marcescens, 83% and 44% for imipenem-resistant Acinetobacter spp., and 32% and 17% for imipenem-resistant Pseudomonas aeruginosa, respectively. CONCLUSION: The most prevalent bacteria in ICUs were S. aureus, CNS, and Acinetobacter spp., and high multi-drug resistance rates were observed in the Acinetobacter isolates. Therefore, infection control should be practiced in ICUs to prevent infections caused by multi-drug resistant bacteria.

Acute Hypoxia Activates an ENaC-like Channel in Rat Pheochromocytoma (PC12) Cells

Cells can resist and even recover from stress induced by acute hypoxia, whereas chronic hypoxia often leads to irreversible damage and eventually death. Although little is known about the response(s) to acute hypoxia in neuronal cells, alterations in ion channel activity could be preferential. This study aimed to elucidate which channel type is involved in the response to acute hypoxia in rat pheochromocytomal (PC12) cells as a neuronal cell model. Using perfusing solution saturated with 95% N2 and 5% CO2, induction of cell hypoxia was confirmed based on increased intracellular Ca2+ with diminished oxygen content in the perfusate. During acute hypoxia, one channel type with a conductance of about 30 pS (2.5 pA at -80 mV) was activated within the first 2~3 min following onset of hypoxia and was long-lived for more than 300 ms with high open probability (Po, up to 0.8). This channel was permeable to Na+ ions, but not to K+, Ca+, and Cl- ions, and was sensitively blocked by amiloride (200 nM). These characteristics and behaviors were quite similar to those of epithelial sodium channel (ENaC). RT-PCR and Western blot analyses confirmed that ENaC channel was endogenously expressed in PC12 cells. Taken together, a 30-pS ENaC-like channel was activated in response to acute hypoxia in PC12 cells. This is the first evidence of an acute hypoxia-activated Na+ channel that can contribute to depolarization of the cell.

Antimicrobial Susceptibility of Stenotrophomonas maltophilia Isolates from Korea, and the Activity of Antimicrobial Combinations against the Isolates

The aim of this study was to determine antimicrobial susceptibility of recent clinical Stenotrophomonas maltophilia isolates from Korea, and to compare the activity levels of several combinations of antimicrobials. A total of 206 non-duplicate clinical isolates of S. maltophilia was collected in 2010 from 11 university hospitals. Antimicrobial susceptibility testing was performed using the Clinical Laboratory Standards Institute agar dilution method. In vitro activity of antimicrobial combinations was tested using the checkerboard method. The susceptibility rates to trimethoprim-sulfamethoxazole and minocycline were 96% and 99%, respectively. The susceptibility rate to levofloxacin was 64%. All of four antimicrobial combinations showed synergy against many S. maltophilia isolates. A combination of trimethoprim-sulfamethoxazole plus ticarcillin-clavulanate was most synergistic among the combinations. None of the combinations showed antagonistic activity. Therefore, some of the combinations may be more useful than individual drugs in the treatment of S. maltophilia infection. Further clinical studies are warranted to validate our in vitro test results.

Antimicrobial Susceptibility of Stenotrophomonas maltophilia Isolates from a Korean Tertiary Care Hospital

We determined the antimicrobial susceptibility of 90 clinical isolates of Stenotrophomonas maltophilia collected in 2009 at a tertiary care hospital in Korea. Trimethoprim-sulfamethoxazole, minocycline, and levofloxacin were active against most of the isolates tested. Moxifloxacin and tigecycline were also active and hold promise as therapeutic options for S. maltophilia infections.

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 Clinical Significance of Reuse Disposable Instruments for Laparoscopic Surgery / 대한내시경복강경외과학회지

PURPOSE: Laparoscopic instruments have been remarkably developed through many trials. Various studies and experiments on laparoscopic instruments are underway in other countries. Laparoscopic surgery is also very actively applied in Korea. However, research on the use and safety of the instruments is stagnant. Furthermore, reuse of some disposable laparoscopic instruments is frequently observed, but there are only rare studies on the safety of this. Thus, we tried to provide study cases on the safety of repeated use of disposable laparoscopic instruments. METHODS: To investigate the effectiveness of sterilization and a re-package procedure, we divided the laparoscopic instruments that are commonly used in our institution into 10 types. Among all the available instruments, 32 instruments were selected for the simulation experiment. Each instrument was sterilized using ethylene oxide gas or glutaraldehyde 2%, and then packaged. Then, each was observed grossly and microscopically under aseptic conditions and we looked for any remnant foreign body or contaminant. When remnant foreign body or contaminant was found, they were collected and separately cultured. RESULTS: Residual contaminants were found in 15 instruments (46.9%) out of a total of 32 and microorganisms, including coagulase-negative staphylococcus and gamma-hemolytic streptococcus, were cultured from (9.38%), and each had different types of microorganisms. CONCLUSION: It is remarkable that the bacteria were cultured from recycled laparoscopic instruments after sterilization. The reuse of laparoscopic instruments might be cost-effective, but further studies on its safety are required. Moreover, careful inspection on the method of surgical instrument sterilization in each institution will be necessary.

MTHFR C677T Polymorphism as a Risk Factor for Vascular Calcification in Chronic Hemodialysis Patients

Polymorphism of 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T is one of the suggested risk factors for atherosclerosis. However, few studies have reported on the relationship between MTHFR C677T polymorphism and vascular calcification (VC) in chronic hemodialysis patients. We investigated the relationship between the MTHFR C677T polymorphism and VC in 152 chronic hemodialysis patients. Patients with a TT genotype exhibited significantly higher VC scores than patients expressing CC and CT (P = 0.002). The prevalence of peripheral vascular disease increased with the incidence of MTHFR C677T mutations for all patients, and the incidence of cerebrovascular accidents also increased with the presence of mutations for young patients (< or = 60 yr) (P < 0.05). Patients with CT and TT genotypes had adjusted odds ratios for VC of 1.39 and 1.58, respectively (P < 0.05). In summary, these data suggest that the MTHFR C677T polymorphism affects the degree of VC in chronic hemodialysis patients.

Investigation of Toxin Gene Diversity, Molecular Epidemiology, and Antimicrobial Resistance of Clostridium difficile Isolated from 12 Hospitals in South Korea / 대한진단검사의학회지

BACKGROUND: Clostridium difficile is a major cause of antibiotic-associated diarrhea. The objective of this study was to characterize clinical isolates of C. difficile obtained from various regions in Korea with regard to their toxin status, molecular type, and antimicrobial susceptibility. METHODS: We analyzed a total of 408 C. difficile isolates obtained between 2006 and 2008 from 408 patients with diarrhea in 12 South Korean teaching hospitals. C. difficile toxin genes tcdA, tcdB, cdtA, and cdtB were detected by PCR. Molecular genotyping was performed by PCR ribotyping. Antimicrobial susceptibilities of the 120 C. difficile isolates were assessed by agar dilution methods. RESULTS: Among 337 toxigenic isolates, 105 were toxin A-negative and toxin B-positive (A-B+) and 29 were binary toxin-producing strains. PCR ribotyping showed 50 different ribotype patterns. The 5 most frequently occurring ribotypes comprised 62.0% of all identified ribotypes. No isolate was susceptible to cefoxitin, and all except 1 were susceptible to piperacillin and piperacillin-tazobactam. The resistance rates of isolates to imipenem, cefotetan, moxifloxacin, ampicillin, and clindamycin were 25%, 34%, 42%, 51%, and 60%, respectively. The isolates showed no resistance to metronidazole or vancomycin. CONCLUSIONS: This is the first nationwide study on the toxin status, including PCR ribotyping and antimicrobial resistance, of C. difficile isolates in Korea. The prevalence of A-B+ strains was 25.7%, much higher than that reported from other countries. Binary toxin-producing strains accounted for 7.1% of all strains, which was not rare in Korea. The most prevalent ribotype was ribotype 017, and all A-B+ strains showed this pattern. We did not isolate strains with decreased susceptibility to metronidazole or vancomycin.

Mechanisms of Selective Antimicrobial Activity of Gaegurin 4

Gaegurin 4 (GGN4), an antimicrobial peptide isolated from a Korean frog, is five times more potent against Gram-positive than Gram-negative bacteria, but has little hemolytic activity. To understand the mechanism of such cell selectivity, we examined GGN4-induced K+ efflux from target cells, and membrane conductances in planar lipid bilayers. The K+ efflux from Gram-positive M. luteus (2.5microgram/ml) was faster and larger than that from Gram-negative E. coli (75microgram/ml), while that from RBC was negligible even at higher concentration (100microgram/ml). GGN4 induced larger conductances in the planar bilayers which were formed with lipids extracted from Gram-positive B. subtilis than in those from E. coli (p<0.01), however, the effects of GGN4 were not selective in the bilayers formed with lipids from E. coli and red blood cells. Addition of an acidic phospholipid, phosphatidylserine to planar bilayers increased the GGN4-induced membrane conductance (p<0.05), but addition of phosphatidylcholine or cholesterol reduced it (p<0.05). Transmission electron microscopy revealed that GGN4 induced pore-like damages in M. luteus and dis-layering damages on the outer wall of E. coli. Taken together, the present results indicate that the selectivity of GGN4 toward Gram-positive over Gram-negative bacteria is due to negative surface charges, and interaction of GGN4 with outer walls. The selectivity toward bacteria over RBC is due to the presence of phosphatidylcholine and cholesterol, and the trans-bilayer lipid asymmetry in RBC. The results suggest that design of selective antimicrobial peptides should be based on the composition and topology of membrane lipids in the target cells.

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.

Diclofenac, a Non-steroidal Anti-inflammatory Drug, Inhibits L-type Ca2+ Channels in Neonatal Rat Ventricular Cardiomyocytes

A non-steroidal anti-inflammatory drug (NSAID) has many adverse effects including cardiovascular (CV) risk. Diclofenac among the nonselective NSAIDs has the highest CV risk such as congestive heart failure, which resulted commonly from the impaired cardiac pumping due to a disrupted excitation-contraction (E-C) coupling. We investigated the effects of diclofenac on the L-type calcium channels which are essential to the E-C coupling at the level of single ventricular myocytes isolated from neonatal rat heart, using the whole-cell voltage-clamp technique. Only diclofenac of three NSAIDs, including naproxen and ibuprofen, significantly reduced inward whole cell currents. At concentrations higher than 3 micrometer, diclofenac inhibited reversibly the Na+ current and did irreversibly the L-type Ca2+ channels-mediated inward current (IC50=12.89+/-0.43 micrometer) in a dose-dependent manner. However, nifedipine, a well-known L-type channel blocker, effectively inhibited the L-type Ca2+ currents but not the Na+ current. Our finding may explain that diclofenac causes the CV risk by the inhibition of L-type Ca2+ channel, leading to the impairment of E-C coupling in cardiac myocytes.

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.