Jeongsook Yoon, Heewon Moon, and Miae Lee
Ann Clin Microbiol 2006 June, 9(1): 1-6. Published on 20 June 2006.
Background: Pseudomonas aeruginosafrequently causes nosocomial infection. Recently, there have been reports of infection with multidrug-resistant P. aeruginosa. The purpose of this study was to evaluate the in vitro effect of antimicrobial combination against multidrug-resistant P. aeruginosa.
Methods: Twenty isolates of imipenem and/or cefepime resistant P. aeruginosa were collected from the microbiology laboratory of Ewha Womans Unversity Mokdong Hospital. Checkerboard titration method was used to assess the activity of ceftazidime or cefepime in combination with amikacin, gentamicin or aztreonam, and colistin in combination with ceftazidime or rifampin.
Results: All isolates were resistant to more than 12 antimicrobial agents including imipenem and/ or cefepime by broth microdilution method; however, no isolates were resistant to colistin. Most of the isolates showed high level resistance to ceftazidime, cefepime and meropenem, with MIC90 of 128, 512 and 64 μg/mL, respectively. The MIC90 of colistin was 2 μg/mL, which is within the susceptible range. Synergistic effect was not detected by the checkerboard titration method with any antimicrobial combinations. However, a partial synergy was observed in 40% of the isolates with the combination of ceftazidime and amikacin, 65% with ceftazidime and gentamicin, 45% with cefepime and amikacin, and 75% with cefepime and gentamicin. Other antimicrobial combinations showed indifference against most strains, and antagonism was not observed.
Conclusion: Multidrug-resistant P. aeruginosa isolates were all susceptible to colistin. The combined regimens of ceftazidime with amikacin or gentamicin and cefepime with amikacin or gentamicin revealed a partially synergistic effect in 40-75% of the isolates.
[in Korean]
Woon Bo Heo, Nan Young Lee, Kyu Young Jeong, and Won Kil Lee
Ann Clin Microbiol 2006 June, 9(1): 7-12. Published on 20 June 2006.
Background: TT virus (TTV), isolated initially from a Japanese patient with posttransfusion hepatitis of unknown etiology, was suggested to be a new causative agent of hepatitis. However, it has been found to infect both healthy and diseased individuals and numerous studies have raised questions about its pathogenic role in hepatitis. In order to study its prevalence and clinical impact on hepatitis, we assessed the frequency of TTV DNA.
Methods: Serum samples were obtained from 60 cases of the controls, 77 cases of chronic liver diseases, 44 cases of hemodialyzed patients, and 65 cases of transfused patients. TTV DNA was detected using nested polymerase chain reaction and alanine aminotransferase (ALT), aspartate aminotransferase (AST), and hepatitis B surface antigen (HBsAg) were measured.
Results: TTV DNA was detected in 41.7% of the controls, 51.9% of patients with chronic liver diseases, 68.2% of hemodialyzed patients and 61.5% of transfused patients. Comparison between patients with or without TTV revealed no significant differences in AST, ALT, and HBsAg test results.
Conclusion: The prevalance of TTV infection in patients with chronic liver diseases was similar to that in the controls. TTV infection was not related to abnormal liver function findings and HBsAg positivity. We found no relationship between TTV infection and chronic liver diseases.
[in Korean]
Sun Min Lee, Eun Joo Song, Eun Kyoung Yang, Il Kwon Bae, Seok Hoon Jeong, Jeong Man Kim, Eun Yup Lee , and Chulhun L. Chang
Ann Clin Microbiol 2006 June, 9(1): 13-17. Published on 20 June 2006.
Background: As clinical isolates of Staphylococcus aureus with reduced inhibition zone of arbekacin in disk diffusion susceptibility tests are observed frequently, we examined their susceptibility to the antibiotic by comparing the results of the agar dilution testing with those of disk diffusion testing.
Methods: During the period of May through July, 2004, 88 isolates of methicillin-resistant and 11 methicillin-susceptible S. aureus were collected from clinical specimens in Pusan National University Hospital and Kosin University Gospel Hospital. Minimal inhibitory concentrations (MICs) of arbekacin were determined by the agar dilution method, and inhibition zones by the disk diffusion method.
Results: All of the 99 isolates were tested susceptible to arbekacin by the agar dilution method (MIC≤8mg/L). By the disk diffusion method, however, 5 isolates (5.1%) were intermediate (minor error) and 2 isolates (2.0%) resistant (major error).
Conclusion: All isolates were susceptible to arbekacin, but the disk diffusion method showed 7 per cent of minor or major errors.
[in Korean]
Hyun-Ju Jung , Eun-Ha Koh , Sunjoo Kim , Kook-Young Maeng, and Sung-Ha Kang
Ann Clin Microbiol 2006 June, 9(1): 18-23. Published on 20 June 2006.
Background: T typing has been used as a screening test for epidemiologic studies of group A streptococci (GAS) infections or carriers, and M typing has been performed for virulence studies. However, M typing is difficult to perform in routine laboratories. Recently, genotyping of the emm gene, which encodes the M protein, has become available. We investigated which T antigen is closely associated with a certain emm genotype.
Methods: GAS were collected from the children in Jinju who were asymptomatic carriers (N=349) or had acute pharyngitis (N=122) during the 3 year-period from 2002 through 2004. T typing was performed by a slide aggulutination, and emm genotyping by PCR and DNA sequencing.
Results: More than 90% of T1, T3, T6, T12, T25, and T5/27/44 antigens were associated with emm1, emm3, emm6, emm12 and 22, emm75, and emm44/61 genotypes, respectively; however, other T antigens, such as T2, T4, T7, T11, and B3264, were not associated with any particular emm genotypes.
Conclusion: Several T antigens are so closely associated with particular emm genotypes that one could predict emm genotypes based on the result of T typing.
[in Korean]
Jeong Man Kim, Kyeong Hee Kim, Eun Ju Song, Sun Min Lee, Eun Yup Lee, Eun Hee Park, and Chulhun L. Chang
Ann Clin Microbiol 2006 June, 9(1): 24-29. Published on 20 June 2006.
Background: The frequent outbreak of legionellosis makes it critical to identify infection sources for the prevention and blockade of transmission of the disease.
Methods: Thirty-one strains of Legionella pneumophila isolated from the cooling towers of big buildings in Busan and Gyungsangnamdo Province areas, 12 strains of L. pneumophila from patients in Japan, and one type strain (L. pneumophila ATCC 33152) were used for molecular strain typing by using an infrequent-restriction-site polymerase chain reaction (IRS-PCR).
Results: Each strain revealed to have 7-16 bands of 200-1000 bp size. All 44 strains showed band patterns different from each other, except two strains sharing 90% homology.
Conclusion: The molecular typing of Legionella by IRS-PCR is an excellent and rapid method for discriminating strains; therefore, it should be useful in demonstrating the identity of possible outbreak strains.
[in Korean]
Myung Hee Lee
Ann Clin Microbiol 2006 June, 9(1): 30-35. Published on 20 June 2006.
Background: Urine culture is still the standard laboratory procedure for definitive diagnosis of urinary tract infection. The author investigated the feasibility of eliminating the costs and time expended in examination of negative urine cultures by combining the Sysmex UF-100 (Toa Medical Electronics, Kobe, Japan) urine flow cytometer and urine strips to predict the outcome of urine cultures.
Methods: Seven hundred eighty one specimens were obtained from 661 males and 120 females (mean age, 66 years; range, 4~93 years). Urine cultures were performed with 10,000 colony forming units (CFU)/mL as the positive criterion. Each sample was analyzed by Clinitek Atlas (Bayer Co., Elkhart, IN, USA) using N-multistix SG urine strips, followed by identification and quantification of the formed elements on the Sysmex UF-100.
Results: Of the 781 urine specimens examined, 402 (51.5%) yielded positive cultures. The diagnostic performance of the UF-100 results for bacteria or WBC vs the urine strip results for leukocyte esterase or nitrite in comparison with the urine culture results were as follows: sensitivity 0.88 vs 0.80, specificity 0.77 vs 0.77, positive predictive value 0.80 vs 0.78, and negative predictive value 0.85 vs 0.79. The highest sensitivity (0.91) and the lowest false negative (0.05) were obtained when any one of the four tests was positive.
Conclusion: The use of Sysmex UF-100 flow cytometer and urine strip results, seperately or in combination, does not accurately predict the outcome of urine cultures.
[in Korean]
Young Uh, Ohgun Kwon, Kap Jun Yoon, Gyu Yul Hwang, and Hyo Youl Kim
Ann Clin Microbiol 2006 June, 9(1): 36-41. Published on 20 June 2006.
Background: The association of Streptococcus bovis biotypes with the type of clinical infection and underlying malignancies and data on antimicrobial susceptibility of S. bovis have rarely been reported in Korea. The aim of this investigation was to characterize the clinical features of patients with S. bovis bacteremia, and to determine the antimicrobial susceptibility of S. bovis strains isolated from blood cultures.
Methods: The clinical data of 67 S. bovis isolates between May 1998 and April 2005 at Wonju Christian Hospital were retrospectively analyzed. The organism was identified by API Strep 32 kit and, for blood isolates, antimicrobial susceptibility testing was performed by the disk diffusion method and penicillin MICs were determined by E test.
Results: Of the 67 S. bovis isolates, 18 (27%) were biotype I and 49 (73%) were biotype II. Isolation rates by specimen type were, in decreasing order, wound. 37%; blood, 19%; and urine, 12%. Of the 13 S. bovis bacteremias, 2 were caused by biotype I and 11 were by biotype II; liver diseases (46%) were the most common underlying diseases; none of the 13 patients had gastrointestinal malignancies; one and three isolates were intermediate and resistant to penicillin, respectively; eleven were resistant to erythromycin; two and five were intermediate and resistant to clindamycin, respectively.
Conclusion: Most of the S. bovis isolates from blood were biotype II. Liver diseases were the most common underlying diseases. S. bovis isolates from blood displayed a high rate of resistance to erythromycin and clindamycin.
[in Korean]
Gyun Yeol Ahn, Sook jin Jang, Sung Hyun Lee, Ok Yeon Jeong, Bidur Prasad Chaulagain, Dae Soo Moon, and Young Jin Park
Ann Clin Microbiol 2006 June, 9(1): 42-50. Published on 20 June 2006.
Background: Blood culture is an important procedure for the determination of the etiologic agent of septicemia. Analysis of the blood culture results can provide clinicians with very important information for the empirical treatment of patients.
Methods: In this study the blood cuture results at Chosun University Hospital during the years 2002 to 2005 were analysed to determine the species and antimicrobial susceptibility of the isolates. Blood culture bottles were incubated in BACTEC 9240 blood culture system; the isolates were identified by VitekⅡ, and antimicrobial susceptibility was tested by VitekⅡ system or the NCCLS disk diffusion method.
Results: Positive blood cultures were obtained from 1,520 (18.5%) patients. Among the microorganisms isolated from blood culture, 97.0% were aerobic and facultative anaerobic bacteria and 2.8% were fungi. Frequently isolated organisms in decreasing order were coagulase-negative staphylococci (CNS), Escherichia coli, Staphylococus aureus, Stenotrophomonas maltophilia, Serratia marcescens, and Klebsiella pneumoniae. The proportion of Pseudomonas aeruginosa isolates resistant to ceftazidime and imipenem was increased during the study period.
Conclusion: E. coli was the most frequent etiologic agent of bacteremia except CNS, common contaminants of skin, at Chosun University Hospital. It seems to be necessary to enhance infection control measures to cope with an increasing number of the resistant bacteria to various antibiotics.
[in Korean]
Eun-Ha Koh, Kook Young Maeng, Sunjoo Kim, Hyun ju Jeong, and Nam Yong Lee
Ann Clin Microbiol 2006 June, 9(1): 51-57. Published on 20 June 2006.
Background: The erythromycin (EM) resistance rates and emm genotypes of Streptococcus pyogenes could vary by geographical location and study period. The purpose of this study, involving a large number of children, was to determine EM resistance rate and its resistance mechanism of S. pyogenes, and to compare these results with those of previous studies performed at the same area.
Methods: Throat cultures were taken from 2,351 healthy children of four elementary schools from October through December, 2004 in Jinju. A total of 328 strains of S. pyogenes were isolated. Antimicrobial susceptibility test was performed by the agar dilution method against six antimicrobial agents. The phenotypes of EM resistance were evaluated by the double-disk diffusion test and the frequency of ermB and mefA genes was determined by polymerase chain reaction.
Results: Resistance rates of S. pyogenes to EM, clindamycin and tetracycline were 9.8%, 8.8% and 18.3%, respectively. Almost all isolates were susceptible to ofloxacin, levofloxacin and chloramphenicol. Constitutive resistance (CR) was observed in 87.5%, M phenotype in 9.4%, and inducible resistance only in 3.1%. The ermB and mefA genes were present in 90.6% and 9.4% of the isolates, respectively.
Conclusion: The resistance rate to EM of S. pyogenes was 9.8% in 2004, which was a large drop from the 51% shown in 2002. CR with the ermB gene was predominant, suggesting that most of the EM resistant isolates have a high level of resistance.
[in Korean]
Kyung Ran Jun, Hong Seon Jeon, Heungsup Sung, and Mi-Na Kim
Ann Clin Microbiol 2006 June, 9(1): 58-63. Published on 20 June 2006.
Background: We evaluated the BD Phoenix Automated Microbiology System (Phoenix) for its ability to detect methicillin resistant Staphylococcus aureus(MRSA) and compared the results to those obtained by the Clinical and Laboratory Standards Institute (CLSI) agar dilution method, a mecA gene PCR method, and the MicroScan WalkAway 96 System (MicroScan).
Methods: One hundred seventy S. aureus strains (Group I) isolated from blood and urine cultures were collected from eight university hospitals and 58 strains (Group II) including 20 blood isolates among Group I and 38 isolates from skin lesions of atopic patients were collected from Asan Medical Center. All 208 isolates were tested with Phoenix using PMIC/ID-53 panels, and the tests were repeated when the results were indeterminate. The results by Phoenix were compared to the susceptibility results obtained by reference methods: the CLSI method for oxacillin MIC for Group I strains, and a PCR assay method for detection of the mecA gene and MicroScan tests for oxacillin susceptibility for Group II strains.
Results: One hundred strains (58.8%) in Group I were MRSA and 28 strains (48.3%) were mecA positive in Group II. Compared to the CLSI method, Phoenix showed the sensitivity and specificity of 100% and MIC agreement of 99.4% for Group I strains. The level of agreement between Phoenix and MicroScan for oxacillin MIC and their interpretation were 98.3% and 100%, respectively, for Group II strains. Both MicroScan and Phenix failed to detect one mecA-positive strain: its MIC was shown as 2 μg/mL twice by MicroScan and 2 μg/mL twice and >2 μg/mL once by Phoenix. The frequency of the indeterminate results was 5.5% and the mean time to completion of the tests was 12.8 (10.2 – 16) hours in Phoenix.
Conclusion: Phoenix showed a high level of sensitivity and specificity for the detection of MRSA with an excellent correlation with MicroScan. Further evaluation is required for detection of heterogeneous MRSA.
[in Korean]
Sook-Jin Jang, Jin Hee Kim, Young Sook Kim, Jong Hee Shin, Geon Park, Bidur Prasad Chaulagain, Dae Soo Moon, and Young Jin Park
Ann Clin Microbiol 2006 June, 9(1): 64-70. Published on 20 June 2006.
Background: Rapid detection of pathogens in blood is important in patient management, because the mortality rate associated with bloodstream infections is very high. We evaluated the efficiency of a 16S rDNA PCR assay for the detection of various pathogens in blood culture broth in a clinical laboratory.
Methods: 16S rDNA PCR was performed on 221 blood culture bottles consisting of 99 culturepositive and 122 culture-negative samples. The results were compared with conventional culture methods. We also compared the efficiency of three DNA extraction and purification methods using proteinase K, triton X-100, and benzyl alcohol-guanidine DNA extraction of blood culture broths.
Results: The 16S rDNA PCR method detected 95 (12 Staphylococcus aureus, 27 coagulase negative staphylococci, 10 enterococci, 5 streptococci, 37 gram negative bacilli, 4 corynebacteria) of 99 positive culture bottles. Four false-negative results were obtained for bottles containing 2 Corynebacterium, 1 Escherichia coli, and 1 S. aureus species. All 122 bottles that showed no blood culture growth were negative by 16S rDNA PCR. Overall, the sensitivity, specificity, positive predictive values and negative predictive values of 16S rDNA PCR relative to the culture results were 96.0%, 100%, 100%, and 96.8%, respectively. Among the three DNA extraction methods, the benzyl alcohol-guanidine method was most effective.
Conclusion: The 16S rDNA PCR assay is a rapid and efficient means of detecting various pathogens in the blood and has great potential for use in the clinical microbiology laboratory.
Chang Ki Kim, Injoo Cho, Youn Hee Park, Kyoung Ho Roh, Dongeun Yong, Kyungwon Lee, June Myung Kim, and Yunsop Chong
Ann Clin Microbiol 2006 June, 9(1): 71-75. Published on 20 June 2006.
Haemophilus aphrophilus is a facultative anaerobic, gram-negative coccobacillus or bacillus and its growth is stimulated by 5 to 10% CO2 . Most Haemophilus species require either exogenous X or V factor or both to grow, but H. aphrophilus can grow without these factors. H. aphrophilus rarely causes invasive infections such as endocarditis, septicemia, pneumonia and peritonitis in human. Two cases of infective endocarditis by H. aphrophilus have been reported in Korea. However, there has been no report of polymicrobial endocarditis by H. aphrophilus and other bacteria. We isolated H. aphrophilus and coagulase-negative staphylococci (CNS) from the blood of a 38-year-old woman with prosthetic valve endocarditis. She underwent an emergent operation and a culture of the prosthetic valve grew H. aphrophilus. Brain abscess was developed at hospital day 11. H. aphrophilus was susceptible to all antibiotics tested such as ampicillin and cefotaxime, and CNS was susceptible to oxacillin and vancomycin. The patient responded well to therapy with ceftriaxone, teicoplanin, and gentamicin.
[in Korean]
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