Seungjun Lee, Seong Chun Kim, Sunjoo Kim
Ann Clin Microbiol 2007 April, 10(1): 1-5. Published on 20 April 2007.
RNA interference (RNAi) is a gene-silencing technology by which small double-stranded RNAs are used to target the degradation of RNA with complementary sequence. RNAi is found in a wide variety of organisms (Caenorhabditis elegans, insects, plants, microorganisms and animals). With RNAi, we have harnessed the gene function to be explored, revolutionized our ability to perform large-scale genetic screens, and even therapeutic potential.
[in Korean]
Ji-Young Moon, Yung-Bu Kim, Chulhun L. Chang
Ann Clin Microbiol 2007 April, 10(1): 6-13. Published on 20 April 2007.
Background: Salmonella enterica serovars often have a broad host range and cause some gastrointestinal and systemic diseases. The diagnosis of typhoid fever or paratyphoid fever is made by ordinary culture methods and biochemical tests. However, a more rapid and alternative method of diagnosing these diseases is in need since the classical diagnostic method requires several days for a result. Some researchers have already reported serovar Typhi detection methods with PCR using the fliC-d gene and the Vi capsular antigen gene.
Methods: Thirty-six Salmonella strains isolated at Pusan National University Hospital from 1997 to 2004 were used for a rapid identification of S. enterica serovars Typhi and Paratyphi A with multiplex PCR that uses the O (rfbE, rfbS), H (fliC-d, fliC-a), and Vi (viaB) antigen genes. To further characterize these Salmonella strains, we used PCR to detect genes (invA and enterotoxin) for proposed virulence factors and performed antimicrobial susceptibility testing, serotyping and pulsed-field gel electrophoresis for epidemiological characteristics.
Results: Most strains were resistant to ampicillin. By PCR, tyv, prt, fliC-d and viaB genes were detected in serovar Typhi, whereas only fliC-a and prt genes were found in serovar Paratyphi A. In addition, invA and enterotoxin genes were detected in both strains.
Conclusion: This method enabled us to identify and differentiate serovars Typhi and Paratyphi A by only a single PCR assay. That is, clinically important human pathogens were more rapidly and specifically detected and identified with multiplex PCR.
[in Korean]
Han-Sung Kim, Jae-Seok Kim, Wonkeun Song, Hee Jung Kang, Kyu Man Lee
Ann Clin Microbiol 2007 April, 10(1): 14-18. Published on 20 April 2007.
Background: TT virus (TTV) infection is highly prevalent in the general population and in the patients infected with hepatitis B virus (HBV) or hepatitis C vius (HCV). The aim of the present study was to assess the positive rates of TTV DNA using different PCR primer sets in healthy and HBV or HCV-infected individuals in Korea.
Methods: TTV DNA was investigated in serum samples of 69 healthy individuals and 59 HBV-infected and 34 HCV-infected individuals by nested PCR assays using primers from N22 region, 5′-untranslated region (UTR), and 3′ UTR of viral genome.
Results: TTV DNA was detected in 43% of total study populations using N22 primers, in 69% using 5′ UTR primers and, in 64% using 3′ UTR primers. No significant difference was observed in the positive rates of TTV DNA between healthy and HBV or HCV- infected individuals.
Conclusion: The PCR assays for TTV DNA using 5′ UTR primers and 3′ UTR primers exhibited higher positive rates than that of the assay using N22 primers without any significant difference between healthy and HBV or HCV-infected individuals.
[in Korean]
Young Ree Kim, Jung-Sik Huh, Sung-Ha Kang
Ann Clin Microbiol 2007 April, 10(1): 19-24. Published on 20 April 2007.
Background: In order to provide a guideline for empirical treatment of urinary tract infections, we studied a change in causative organisms and antimicrobial susceptibility in our region of an island.
Methods: We reviewed the results of antimicrobial susceptibility and the hospital charts of 3,064 patients with a significant bacteriuria (more than 105 colony forming unit/mL in urine cultures); the patients had been admitted to or seen at the out-patient clinic of Cheju University Hospital during the period from January 2002 to December 2005.
Results: The most common pathogens were Escherichia coli (44.9%), Klebsiella spp. (8.1%), and Pseudomonas spp. (7.0%). In E. coli, the mean percent resistance to ampicillin, trimethoprim-sulfamethoxazole, and ciprofloxacin during the 4-year period was 69.0%, 32.5%, and 24.7%, respectively.
Conclusion: An increasing resistance of common urinary pathogens to known empirical agents such as ampicillin, trimethoprim-sulfamethoxazole, and ciprofloxacin caused a need for a more updated guideline in our region of an island.
[in Korean]
Ji-Hyun Cho, Hye-Soo Lee, Key-Earn Lee, Do-Sim Park, Young-Jin Lee, Hyung-Bae Moon, Chang-Soo Choi, Eun-Young Cho, Haak-Cheoul Kim
Ann Clin Microbiol 2007 April, 10(1): 25-31. Published on 20 April 2007.
Background: As oral antiviral treatment for chronic hepatitis B increases, quantitation of viral load has become an essential test for HBV management, and assays using real-time PCR principles have been introduced recently.
Methods: We analysed the analytical performance (precision, linear range, and sensitivity) of RealArt HBV LC PCR Reagents (Artus GmbH, Hamburg, Germany), its correlation with COBAS AMPLICOR HBV MONITOR Test (Roche Diagnostics, Mannheim, Germany), and distribution of viral load in the patients’ sera according to antiviral treatment and presence of HBeAg.
Results: Variation of intra-assay and inter-assay were 39.7% and 78.1% at 103 copies/mL of viral load, 18.1% and 73.2% at 104 copies/mL, and below 10% and below 15% between 105～109copies/mL. Linear range was with 5×103～2.3×109 copies/mL. Correlation with Amplicor was y=0.9211x+0.607 (R2=0.7801, P＜0.001) and the median concentration in the patients without any treatment was 6.3×107 copies/mL (HBeAg positive) and 3.1×103copies/mL (HBeAg negative).
Conclusion: RealArt reagent using principles of real-time PCR, would be an appropriate laboratory method for HBV management.
[in Korean]
Jae-Mann Lee, Kyoung Wha Hwang, Seung Jegal
Ann Clin Microbiol 2007 April, 10(1): 32-36. Published on 20 April 2007.
Background: We monitored the prevalence of antimicrobial resistance and the pattern of multiple drug resistance in Escherichia coli isolated from healthy people in the community.
Methods: We performed antimicrobial susceptibility testing on 491 isolates of E. coli from 692 healthy people in Incheon from February to July in 2006. The results were interpreted according to the CLSI guidelines.
Results: The highest rate of resistance was observed against tetracycline (46.6%), ampicillin (41.1%), ticarcillin (37.9%), streptomycin (31.0%), and nalidixic acid (23.6%). Twenty six percent of isolates were observed to be resistant to five or more of the antimicrobials tested.
Conclusion: In order to maintain a low level of antimicrobial use and resistance, the surveillance of antimicrobial resistance in the community would be very important, as it provides epidemical data to set up and control antibiotic guidelines and serves as an early warning for resistance in pathogenic bacteria.
[in Korean]
Young Uh, Gyu Yul Hwang, Kap Jun Yoon, Hyo Youl Kim, Hong Sun Uh, O Kab Kwon
Ann Clin Microbiol 2007 April, 10(1): 37-43. Published on 20 April 2007.
Background: It is well-known that silver ions and silver compounds are broad-spectrum antimicrobial agents effective against gram-positive and gram-negative bacteria, and yeasts. Thus, silver ions, as an antibacterial agent, have been used in the components of materials used in medical devices or coatings. Recently, advances in nanotechnology have enabled manufacturers to develop silver particles of a nanometer size with a safer and more effective antimicrobial activity. So, we evaluate the antimicrobial activity of nanoSilver-coated gauze against clinical isolates.
Methods: Three kinds of nanoSilver-coated gauzes (100Å, 800Å, and 1,500Å) were tested for antimicrobial activity by the disk diffusion method. The organisms tested included clinical isolates of nonfermentative gram-negative bacilli (143 isolates), aerobic gram- negative bacteria (188), aerobic gram-positive bacteria (397), anaerobic bacteria (46), and yeasts (161), and three reference ATCC strains.
Results: The susceptible rates to NanoSilver of nonfermentative gram-negative bacilli (NFB), aerobic gram- negative bacteria and aerobic gram-positive bacteria were 87%, 87% and 78%, respectively. Antimicrobial activity of NanoSilver against imipenem-resistant NFB, extended spectrum β-lactamase (ESBL) producing Enterobacteriaceae, and methicillin-resistant Staphylcoccus aureus (MRSA) was similar to that against imipenem-sensitive NFB, ESBL non-producing Enterobacteriaceae, and methicillin-susceptible S. aureus.
Conclusion: NanoSilver-coated gauze exhibits broad spectrum antimicrobial activities to a large number of gram-negative and gram-positive bacteria including imipenem-resistant NFB, ESBL producing Enterobacteriaceae, and MRSA.
[in Korean]
Sollip Kim, Heungsup Sung, Hong Sun Jeon, Suk Ja Park, Sang-Hyuk Park, Mi-Na Kim
Ann Clin Microbiol 2007 April, 10(1): 44-48. Published on 20 April 2007.
Background: Rapid and accurate surveillance is crucial in controlling vancomycin-resistant enterococci (VRE). Culture-based surveillance takes more than 4 days and direct polymerase chain reaction (PCR) is rapid but compromised by a low sensitivity. In this study, we evaluated the performance of an enrichment-PCR method for vanA VRE surveillance.
Methods: In July 2006, 100 fecal specimens were inoculated to Enterococcosel agar (EA) and Enterococcosel broth (EB) containing 6μg/mL vancomycin. After 1 or 2 day-incubation bacterial pellets were obtained from 1 mL of blackened EB and VanA PCR were performed with DNA extract of the pellets (EB+PCR). Blackened EB were also subcultured on EA (EB+ EA). Black colonies on EA were submitted to identification and antimicrobial susceptibility test and, if necessary, they were confirmed with vanA PCR. The electronic medical records were reviewed for previous history of colonization or infection of VRE.
Results: A total of 59 specimens were positive for VRE by at least one method. VanA VRE was detected from 43, 54, and 53 specimens by EA, EB+ PCR, and EB+EA, respectively; 54 EB+PCR positive specimens comprised 43 EA-positive, 7 EA-negative/ EA+EB-positive and 4 EB+PCR-only-positive, and 11 EA-negative/EB+PCR-positive specimens were from the previous VRE-colonizers. The five EB+PCR-negative specimens were EB+EA-positive, suggesting false negativity, probably due to PCR inhibitors. The average turn-around time for EA was 88±35 h, whereas 98% of EB+PCR positive results were obtained at day 1.
Conclusion: Enrichment in EB followed by PCR (EB+ PCR) appears to be a rapid and sensitive method for the detection of vanA VRE in stool specimens. Internal control would be required to detect false negative results.
[in Korean]
Dae Dong Lee, Eun Yup Lee, Seok Hoon Jeong, Chulhun L. Chang
Ann Clin Microbiol 2007 April, 10(1): 49-53. Published on 20 April 2007.
Background: The broth microdilution susceptibility testing method is considered a standard for determining minimum inhibitory concentrations, and the addition of the redox indicator 2,3,5-triphenyltetrazolium chloride (TTC) to the broth microdilution method simplifies and increases its objectivity. The current study evaluated the usefulness of a TTC-modified broth microdilution method for antimicrobial susceptibility test of frequently encountered clinical isolates.
Methods: The minimal inhibitory concentrations (MICs) of 10 antimicrobials for 111 clinical isolates of four bacterial species, Staphylococcus aureus, Escherichia coli, Enterobacter cloacae, and Acinetobacter baumannii, were investigated by a modification of the Clinical and Laboratory Standards Institute (CLSI)-recommended broth microdilution method with the addition of 2,3,5-triphenyltetrazolium chloride (TTC). The inhibitory effects of TTC against 192 strains of 22 bacterial species isolated from clinical specimens were also evaluated.
Results: The number of colonies of all 192 strains of 22 bacterial species grown on TTC-containing Mueller- Hinton agar did not differ from those grown on Mueller-Hinton agar only. The MICs with TTC were within 2 dilutions of those obtained by the CLSI method in 569 (97.6%) of 583 organism-antimicrobial agent combinations.
Conclusions: The colorimetric MIC method using TTC may be a useful surrogate of antimicrobial susceptibility testing for most of the frequently isolated bacteria.
Eun-Ha Koh, Sunjoo Kim
Ann Clin Microbiol 2007 April, 10(1): 54-58. Published on 20 April 2007.
Background: Rapid antigen tests (RAT) of group A streptococci (GAS) are easy to perform and can save two days of bacterial culture time. Performance of SD Bioline Strep A was analyzed in comparison with throat culture.
Methods: Three consecutive throat swabs were taken from 308 healthy elementary schoolchildren. The first two swabs were tested for SD Bioline Strep A and Quidel Quick Vue Dipstick Strep A rapid antigen tests, and the third one was inoculated onto blood agar plate to grow GAS.
Results: Sensitivity, specificity, positive predictive value and negative predictive value of SD Bioline Strep A were 79.3%, 88.9%, 72.2%, and 92.2% respectively. Those of Quidel Quick Vue Strep A were 58.5%, 93.8%, 77.4%, and 86.2% respectively.
Conclusion: SD Bioline Strep A showed a significantly higher sensitivity and a slightly lower specificity compared to Quidel Quick Vue Strep A. SD Bioline Strep A RAT should be useful for the rapid diagnosis of bacterial pharyngitis and the optimum use of antibiotics.
[in Korean]
Hyukmin Lee, Chang Ki Kim, Jongwook Lee, Sung-Hee Lee, Ji Young Ahn, Seong Geun Hong, Yeon Jun Park, Seok Hoon Jeong, Eui-Chong Kim, Wee Kyo Lee, Young Uh, Jong Hee Shin, Tae Yeal Choi, Hyo-Sun Kwak, Kyungwon Lee
Ann Clin Microbiol 2007 April, 10(1): 59-69. Published on 20 April 2007.
Background: Emergence and spread of antimicrobial resistant bacteria make it difficult to treat infections. A rapid increase in antimicrobial-resistant bacteria has become a serious problem in many countries including Korea, and it is important to perform a nationwide study of antimicrobial resistance to obtain some basic data that will help solve these problems. The aim of this study was to determine the nationwide prevalence of resistance among frequently isolated bacterial pathogens in 2005 and 2006 in Korea.
Methods: We collected routine susceptibility data for medically important bacterial pathogens from 12 university and general hospital laboratories in Korea from April to September in 2005 and from January to June in 2006. Collected data was analyzed by patient group.
Results: The proportions of methicillin-resistant Staphylococcus aureus (MRSA) were 65% in 2005 and 72% in 2006, respectively. The resistance rates of Enterococcus faecium to vancomycin were 29% in 2005 and 24% in 2006. The non-susceptible rates of Streptococcus pneumoniae to penicillin were 68% in 2005 and 74% in 2006. The resistant rates of Escherichia coli and Klebsiella pneumoniae to the 3rd generation cephalosporin were 10∼12% and 25∼ 39%, respectively, in 2005 and 11∼15% and 30∼ 34% in 2006. In Citrobacter freundii, Enterobacter cloacae and Serratia marcescens, the resistance rates to 3rd generation cephalosporin were 23∼31%, 32∼ 34%, and 17∼27%, respectively, in 2005 and 21∼ 37%, 37∼43%, and 13∼31% in 2006. The resistance rates to imipenem and meropenem were 21% and 18%, respectively, in Pseudomonas aeruginosa and 18% and 25% in Acinetobacter baumannii in 2005; 29% and 20% in P. aeruginosa and 18% and 23% in A. baumannii in 2006. Cotrimoxazole and levofloxacin resistance rates of Stenotrophomonas maltophilia were 5% and 13%, respectively, in 2005 and 3% and 7% in 2006. There were no isolates resistant to 3rd generation cephalosporin and fluoroquinolone among non-typhoidal Salmonella in 2005.
Conclusion: Antimicrobial resistance of medically important bacteria is still a serious problem in Korea. To manage the problem, a continuous nationwide surveillance and diversified investigation and effort have become more important.
[in Korean]
Ohgun Kwon, Young Uh, Gyu Yel Hwang, Jong In Lee, Hyo Youl Kim, Kap Jun Yoon
Ann Clin Microbiol 2007 April, 10(1): 70-72. Published on 20 April 2007.
Staphylococcus lugdunensis is one of coagulase-negative staphylococci, but rarely causes aggressive and progressive infections similar to Staphylococcus aureus infection. Moreover, agglutination test for clumping factor can be positive, and the colony morphology often resembles that of S. aureus, but S. lugdunensis is usually sensitive to all antimicrobials used against staphylococci. We report a case of septicemia caused by S. lugdunensis in a 71-year-old man with diarrhea, diabetes mellitus, and peripheral neuropathy.
[in Korean]
Kyung Ran Jun, Mi-Sook Jang, Sook Ja Park, Mi-Na Kim, Dong Yoon Kim, Hungwon Tchah, Myoung Joon Kim
Ann Clin Microbiol 2007 April, 10(1): 73-76. Published on 20 April 2007.
Beauveria bassiana is a hyaline Hypomycetes, which is known as an insect pathogen causing infections in silkworm. It is a rare opportunistic pathogen of human accounted for pulmonary infection, keratitis, and deep tissue infection. We report the first case of B. bassiana keratitis in Korea. A 64-year-old man with a 10-year history of herpetic keratitis was referred for the treatment of infectious keratitis in the right eye. Corneal scrapings showed septate hyaline hyphae on calcoflour white-KOH preparation and their cultures grew B. bassiana. At the beginning, the patient was treated empirically with an antiviral and antibiotics, and then the treatment was changed with antifungal agents including voriconazole, when the culture results were available. Since the inflammation had been aggravated despite medical treatments, he underwent a penetrating keratoplasty (PKP). The excised button of cornea showed the hyphae. The treatment with voriconazole was continued until 2 months after PKP, and fungal keratitis did not relapse during a 6-month follow-up period.
[in Korean]
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