Ohgun Kwon

Macrolide Resistance Trends in beta-Hemolytic Streptococci in a Tertiary Korean Hospital

Purpose Erythromycin-resistant β-hemolytic streptococci (BHS) has recently emerged and quickly spread between and within countries throughout the world. In this study, we evaluate the antimicrobial susceptibility patterns and erythromycin resistance mechanisms of BHS during 2003-2004. Materials and Methods The MICs of seven antimicrobials were determined for 204 clinical isolates of BHS from 2003 to 2004. Resistance mechanisms of erythromycin-resistant BHS were studied by the double disk test as well as by polymerase chain reaction (PCR). Results Compared with our previous study, resistance among Streptococcus pyogenes isolates to a variety of drugs decreased strikingly: from 25.7% to 4.8% in erythromycin; 15.8% to 0% in clindamycin; and 47.1% to 19.0% in tetracycline. The prevalent phenotypes and genotypes of macrolide-lincosamide-streptograminB (MLSB) resistance in Streptococcus pyogenes isolates have been changed from the constitutive MLSB phenotype carrying erm(B) to the M phenotype with mef(A) gene. In contrast with Streptococcus pyogenes, resistance rates to erythromycin (36.7%), clindamycin (43.1%), and tetracycline (95.4%) in Streptococcus agalactiae isolates did not show decreasing trends. Among the Streptococcus dysgalactiae subsp. equisimilis isolates (Lancefield group C, G), resistance rates to erythromycin, clindamycin, tetracycline and chloramphenicol were observed to be 9.4%, 3.1%, 68.8%, and 9.4%, respectively. Conclusion Continual monitoring of antimicrobial resistance among large-colony-forming BHS is needed to provide the medical community with current data regarding the resistance mechanisms that are most common to their local or regional environments.

Acute promyelocytic leukemia relapsing as secondary acute myelogenous leukemia with translocation t(3;21)(q26;q22) and RUNX1–MDS1–EVI1 fusion transcript

Acute promyelocytic leukemia (APL) is a subtype of acute myelogenous leukemia (AML) that is characterized by peculiar clinical and biologic features, including severe hemorrhagic diathesis, specific recurrent chromosomal aberration, and distinct morphologic features with predominant pathologic promyelocytes. A reciprocal translocation involving chromosomes 15 and 17, t(15;17)(q22;q21), is a characteristic feature of APL that represents approximately 5-8% of AML. The rearranged gene created by this translocation encodes a chimeric protein PML-RARA that is a transcriptional repressor. In contrast to other AML subtypes, APL is particularly sensitive to treatment with all trans-retinoic acid (ATRA) combined with chemotherapy, converting this once fatal leukemia to a highly curable disease. Nonetheless, therapy-related myelodysplastic syndrome-acute myelogenous leukemia (t-MDS/AML) has been reported as a rare complication of chemotherapy in APL. Of 30 APL cases described as t-MDS/AML in the literature, only 1 case relapsed as acute leukemia with t(3;21)(q26;q22). Here we describe a rare case of APL relapsing as secondary AML with t(3;21)(q26;q22) and clinically characterize this patient using the RUNX1 (previously AML1)-MDS1-EVI1 fusion transcript (with follow-up for 55 months), and review the relevant literature.

Antimicrobial Susceptibility Patterns and Macrolide Resistance Genes of β-Hemolytic Viridans Group Streptococci in a Tertiary Korean Hospital

The aim of this study was to investigate antimicrobial susceptibilities and macrolide resistance mechanisms of β-hemolytic viridans group streptococci (VGS) in a tertiary Korean hospital. Minimum inhibitory concentrations (MICs) of seven antimicrobials were determined for 103 β-hemolytic VGS isolated from various specimens. The macrolide resistance mechanisms of erythromycin-resistant isolates were studied by the double disk test and polymerase chain reaction (PCR). The overall resistance rates of β-hemolytic VGS were found to be 47.5% to tetracycline, 3.9% to chloramphenicol, 9.7% to erythromycin, and 6.8% to clindamycin, whereas all isolates were susceptible to penicillin G, ceftriaxone, and vancomycin. Among ten erythromycin-resistant isolates, six isolates expressed a constitutive MLSB (cMLSB) phenotype, and each of the two isolates expressed the M phenotype, and the inducible MLSB (iMLSB) phenotype. The resistance rates to erythromycin and clindamycin of β-hemolytic VGS seemed to be lower than those of non-β-hemolytic VGS in our hospital, although cMLSB phenotype carrying erm(B) was dominant in β-hemolytic VGS.

Colonization Rate, Serotypes, and Distributions of Macrolide-Lincosamide-StreptograminB Resistant Types of Group B Streptococci in Pregnant Women

GBS in the different culture media was S-THB (96.3%), NGM-B (92.6%), NGM-H (88.9%), and NGM-T (85.2%). The distribution of GBS serotypes was as follows: III (29.6%), V and VI (22.2%), Ib and II (11.1%), and Ia (3.7%). 33.3% of GBS isolates were resistant to erythromycin and 44.4% to clindamycin. Among the nine erythromycin-resistant isolates, eight were serotype V and VI, which are erm(B) positive serotypes. Conclusion: The colonization of pregnant women by GBS, and the incidence of resistance of the GBS isolates to erythromycin and clindamycin were higher than those previously reported. Serotypes V and VI, GBS serotypes that carry the erm(B), are novel serotypes that have not previously been identified in pregnant Korean women. (Korean J Clin Microbiol 2009;12:174-179)

Distributions of Macrolide-Lincosamide-Streptogramin B Resistance Phenotypes in Clinical Isolates of Staphylococi

Background: Increased resistance rates to macrolide-lincosamide-streptogramin B (MLSB) antibiotics among clinical isolates of staphylococci are considered as a consequence of an expanded use of these antibiotics in the treatment of Gram-positive infections. The proportion of MLSB resistance phenotypes of staphylococci is quite different by geographical variations and study periods. The aim of the present study was to determine the distribution of MLSB resistance phenotypes among clinical isolates of staphylococci in a university hospital. Methods: The MLSB resistance phenotypes of clinical isolates of staphylococci were investigated by the double-disk diffusion test using erythromycin and clindamycin disks. Results: Of 7,916 isolates, 55.7% exhibited a constitutive resistance phenotype (cMLSB) whereas 8.1% expressed an inducible resistance phenotype (iMLSB). Among 3,419 coagulase-negative staphylococci (CNS), 32.6% and 10.0% exhibited cMLSB and iMLSB resistance phenotypes, respectively. Of 4,497 Staphylococcus aureus isolates, 73.1% and 6.8% were cMLSB and iMLSB resistance phenotypes, respectively. cMLSB was detected among 90.2% of methicillin-resistant S. aureus (MRSA), 46.5% of methicillin-resistant CNS (MRCNS), 3.2% of methicillin-susceptible CNS (MSCNS), and 2.2% of methicillin-susceptible S. aureus (MSSA). iMLSB was detected among 16.5% of MSSA, 11.5% of MRCNS, 6.7% of MSCNS, and 4.4% of MRSA. Conclusion: MLSB resistance was more prevalent among S. aureus isolates than CNS strains. Although cMLSB was the most frequently detected resistance phenotype among the total staphylococcal isolates, methicillin-susceptible strains exhibited somewhat higher iMLSB resistance rates compared with methicillin-resistant strains. (Korean J Clin Microbiol 2008; 11:78-83)

A Case of Brain Abscess due to Parvimonas micra

is a non-spore-forming anaerobic gram-positive coccus, widely distributed as normal flora in the skin, vagina and mucosa, and able to cause opportunistic infections, particularly endocardi-tis and brain abscess following dental manipulations. A 49-year-old woman was hospitalized due to fever and headache. She had been diagnosed with perio-dontitis at the beginning of fever. A brain abscess was noted in the right temporal lobe on the brain CT, and she was treated with ceftriaxone, isepamicin and metronidazole. In the next day, abscess was as-pirated and drained by a surgical procedure. An or-ganism was isolated from an anaerobic culture of the abscess aspirate, and was identified as

Frequency and Clinical Characteristics of Urinary Tract Infections Caused by Staphylococcus saprophyticus

Background: Staphylococcus saprophyticus is the second most common cause of urinary tract infections (UTIs) in young women. As little is known about the incidence of UTIs caused by this organism in Korea, we examined its frequency and clinical characteristics. Methods: We analyzed the frequency of S. saprophyticus among organisms isolated from urine specimens in Wonju Christian Hospital from July 1996 to June 2008 and reviewed clinical characteristics retrospectively. Results: Of 24,277 strains isolated from urine specimens during the past 12 years, 21 (0.09%) were S. saprophyticus. Outpatients were more common in the S. saprophyticus group than in all patients group (12 of 21, 57% vs 5,098 of 24,277, 21%). The incidence of S. saprophyticus in women was the highest in the group of 15 to 34 years of age. Monthly distributions of isolates were almost constant in all patient groups, while 16 of 21 (76%) cases of the S. saprophyticus group occurred in summer and fall (June to November). Conclusion: The fequencies of S. saprophyticus among organisms isolated from urine specimens in all patient groups and women were 0.09% and 0.17%, respectively, and are much lower than those in other countries. However, we need further studies to examine the prevalence of S. saprophyticus UTIs in other regions of this country. (Korean J Clin Microbiol 2009;12:62-66)

Comparison of the MicroScan® Combo Panel Synergies plus with the MicroScan® Conventional Combo Panel for Diagnostic Performance of Gram-negative and Gram-positive Bacteria

Background: To access the clinical usefulness of MicroScanR Synergies plus Combo Panels (Siemens, USA) for the identification and antimicrobial susceptibility test (AST) of Gram-negative bacteria (GNB) and Gram-positive cocci (GPC), we compared MicroScanR Synergies plus Combo Panels with MicroScanR conventional Combo Panels. Methods: One-hundred four isolates of GNB were simultaneously tested with MicroScanR Synergies plus Neg Combo Type 2 Panel (SINC2) and MicroScanR Neg Combo Panel Type 44 (NC44). One-hundred isolates of GPC were simultaneously tested with MicroScanR Synergies plus Pos Combo 3 Panel (SIPC3) and MicroScanR Pos Combo 1A (PC1A). Results: Of the GNB isolates, agreement rate of identification between SINC2 and NC44 were 92.3% to the species level and 93.3% to the genus level. Of the GPC isolates, agreement rate of identification between SIPC3 and PC1A were 85.0% to the species level and 100% to the genus level. Of the GNB isolates, agreement rate of AST according to antimicrobial agents between SINC2 and NC44 ranged from 86.5% to 100%. Among GPC isolates, agreement rate of AST according to antimicrobial agents between SIPC3 and PC1A were higher than 96.0% with the exception of gentamicin and quinupristin-dalfopristin. Conclusion: Compared with MicroScanR conventional Combo Panels (NC44, PC1A), MicroScanR Synergies plus Combo Panels (SINC2, SIPC3) showed high agreement rate of identification and AST, and had the advantage of more rapid reporting. (Korean J Clin Microbiol 2009;12:193-200)

Use of Boronic Acid Disks for the Detection of Extended-spectrum beta-lactamase and AmpC beta-lactamase in Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca and Proteus mirabilis

Background: Accurate detection of organisms producing extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase is very important for treatment of patients. However, unlike the ESBL confirmatory test, there are no guidelines for detection of organisms producing AmpC β-lactamase. We evaluated a detection method using boronic acid (BA) for ESBL and AmpC β-lactamase. Methods: Clinical isolates of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, and Proteus mirabilis showing intermediate resistance or resistance to cefoxitin (FOX) or positive for ESBL were tested. A ≥5 mm increase in zone diameter of ceftazidime/clavulanic acid/BA (CAZ/CA/BA) and/or cefotaxime/clavulanic acid/BA (CTX/CA/BA) versus CAZ/BA and/or CTX /BA was considered positive for ESBL. Likewise, a ≥5 mm increase in zone diameter of FOX/BA and/or cefotetan/BA (CTT/BA) versus FOX and/or CTT alone was considered positive for AmpC β-lactamase. Results: Among 622 clinical isolates, ESBL positive rates by the CLSI ESBL confirmatory test or by the BA method were 18.1% or 18.4% for E. coli, 38.3% or 40.4% for K. pneumoniae, 8.7% or 8.7% for K. oxytoca, and 14.8% or 14.8% for P. mirabilis, respectively. AmpC β-lactamase positive rates using the BA method were 3.7% for E. coli, 33.3% for K. pneumoniae, 0% for K. oxytoca, and 7.4% for P. mirabilis. The detection rates of coproducing ESBL and AmpC β-lactamase were 2.4% in E. coli 27.1% in K. pneumoniae, and 3.7% in P. mirabilis. Conclusion: The ESBL confirmatory method using BA was found to enhance the detection of ESBLs, even when potentially masked by AmpC β-lactamase. (Korean J Clin Microbiol 2009;12:24-29)