Hung-Mo Chen

Decreased activity of erythromycin against Streptococcus pyogenes in Taiwan.

A total of 78 clinical isolates of Streptococcus pyogenes were collected from January 1992 through December 1993 from patients in southern Taiwan. The in vitro activities of 10 antimicrobial agents were determined by the agar dilution method. Penicillin, cephalothin, cefotaxime, vancomycin, and ofloxacin were shown to be active against S. pyogenes isolates, with MICs at which 90% of isolates are inhibited (MIC90s) being < or = 0.03, < or = 0.13, < or = 0.13, < or = 0.13, and < or = 0.25 microgram/ml, respectively. Erythromycin and azithromycin both had poor activities (MIC50s, 16 and >128 micrograms/ml, respectively; MIC90s, >128 and >128 micrograms/ml, respectively). The activities of tetracycline, clindamycin, and chloramphenicol against a significant number of these isolates were also limited. As the MICs of clindamycin and chloramphenicol for the isolates increased, the MICs of the two macrolides also increased. Clindamycin, chloramphenicol, and the two macrolides were less potent against isolates recovered form throat swab samples than against those from blood or other sources. Isolates of the T12 and T1 serotypes accounted for 53.8% of all isolates. The majority (87.5%) of the isolates recovered from throat swab samples were of the T12 serotype, whereas 19.2% of the isolates recovered from blood were of the T12 serotype. In contrast, 66.7% of the isolates of the T1 serotype were derived from blood but none were derived from throat swab samples. Of the 33 T12 serotype isolates, erythromycin MICs for 78.8% of the isolates were >128 micrograms/ml. Because of the poor activities of erythromycin and azithromycin against S. pyogenes isolates from patients in southern Taiwan, these drugs should no longer be considered the drugs of choice for the management of group A streptococcal infections among patients who live in this area.

Emergence of Qnr determinants in human Salmonella isolates in Taiwan

OBJECTIVES The aim of this study was to determine the prevalence and characteristics of qnr-carrying Salmonella isolates from humans in southern Taiwan. METHODS A total of 446 Salmonella isolates collected between 2003 and 2006 were screened for qnrA, qnrB and qnrS by PCR experiments. Genetic structures of qnr were determined by PCR-based methods or direct sequencing of plasmid DNA. RESULTS qnrB2 and qnrS1 were detected in two serovar Enteritidis isolates and two serovar Typhimurium isolates, respectively. One qnrS1-positive isolate was found to produce the CMY-2 AmpC enzyme. qnrS1 was identified on a 10 kb plasmid, which exhibited >99% nucleotide sequence identity with plasmid TPqnrS-1a reported from the UK. qnrB2 was found in a complex sul1-type class 1 integron on a >100 kb plasmid. CONCLUSIONS This study demonstrated the occurrence of qnrB2 and qnrS1 in Salmonella for the first time in Taiwan and characterized their genetic structures.

Prevalence and Characteristics of Ertapenem-Resistant Klebsiella pneumoniae Isolates in a Taiwanese University Hospital

This study was conducted to investigate the prevalence and characteristics of ertapenem-resistant (ETP-R) Klebsiella pneumoniae isolates at a Taiwanese hospital. The disk-diffusion tests revealed that the rate of ertapenem resistance among all isolates collected in 2008 was 13.5%, and the resistance rate among bloodstream isolates increased from 0% to 13.6% between 2001 and 2008. Eighty-two nonduplicate ETP-R isolates collected in 2008 were examined. Seventy-four (90.2%) isolates of them had extended-spectrum β-lactamases (CTX-M- and SHV-type), AmpC enzymes (DHA-1 and CMY-2), and IMP-8 metallo-β-lactamase alone or in combination, and an extremely high prevalence of fluoroquinolone resistance (95.1%) and plasmid-mediated quinolone resistance determinants (90.2%) were also observed. Eighteen ETP-R but imipenem-susceptible isolates were selected and compared with 18 imipenem-nonsusceptible isolates collected before 2008. Sequence analyses revealed genetic disruptions of OmpK36 in 11 imipenem-nonsusceptible and 6 imipenem-susceptible isolates, respectively, and OmpK35 disruptions in 10 isolates for both groups. For the isolates with intact ompK36, sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggests decreased expression of OmpK36 in 5 of 7 imipenem-nonsusceptible isolates and 3 of 12 imipenem-susceptible isolates. In conclusion, the increasing prevalence of ertapenem resistance that was predominantly attributed to noncarbapenemase-mediated resistance mechanisms in K. pneumoniae is becoming a serious treat to patients in Taiwan.

Metallo-β-lactamase-producing Enterobacteriaceae isolates at a Taiwanese hospital: lack of distinctive phenotypes for screening

Liao I‐C, Chen H‐M, Wu J‐J, Tsai P‐F, Wang L‐R, Yan J‐J. Metallo‐β‐lactamase‐producing Enterobacteriaceae isolates at a Taiwanese hospital: lack of distinctive phenotypes for screening. APMIS 2011; 119: 543–50.

Characterization of the modified Hodge test-positive isolates of Enterobacteriaceae in Taiwan.

BACKGROUND/PURPOSE The modified Hodge test is a phenotypic test to detect KPC-type carbapenemase producers among Enterobacteriaceae, as recommended by the Clinical Laboratory Standards Institute. However, false positive results were reported. In this study, we aimed to large-scale investigate the characterization of the modified Hodge test-positive isolates of Enterobacteriaceae collected between 2006 and 2010 in Taiwan. METHODS Fifty-six isolates, including 24 Enterobacter cloacae, 17 Escherichia coli, 10 Klebsiella pneumoniae, and 5 Citrobacter freundii, tested positive with the modified Hodge test. The in vitro activities of 10 antimicrobial agents were determined by the agar dilution method. Boronic acid combined-disk test was used to further confirm the KPC producers. Phenotype of ESBL, AmpC, class B carbapenemases, and profile of outer membrane proteins were investigated by the confirmatory test, boronic acid disk method, 2-mercaptopropionic acid double-disk method, and urea/sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), respectively. β-lactamase genes were examined by PCR and sequencing. RESULTS These isolates were resistant to ceftazidime (100%), aztreonam (82.1%), ertapenem (64.3%), gentamicin (53.6%), ciprofloxacin (50%), levofloxacin (48.2%), cefepime (19.6%), imipenem (16.1%), meropenem (12.5%), and amikacin (8.9%). Phenotypic testing among isolates revealed the production of ESBLs, metallo-β-lactamases (MBLs), and AmpC in 10 (17.9%), 16 (28.6%), and 12 (44.4%) isolates, respectively. Carbapenemase and non-carbapenemase β-lactamase genes bla(TEM-1), bla(SHV), bla(CTX-M), bla(IMP-8), bla(CMY-2), and bla(DHA-1) were found in 32 (57.1%), 19 (33.9%), 4 (7.1%), 16 (28.6%), 14 (25%), and 5 (8.9%) of the strains, respectively. No class A and D carbapenemase genes were detected. Outer membrane protein profile showed obviously decreased expression in 49 (87.5%) isolates with positive result of modified Hodge test. CONCLUSIONS Our data show that ESBLs, AmpC, and imipenemase-8 (IMP-8) carbapenemase coupled with decreased expression of outer membrane protein were prevalent in Enterobacteriaceae isolates testing positive for the modified Hodge test in Taiwan.

Effect of Overnight Storage of Blood Culture Bottles on Bacterial Detection Time in the BACTEC 9240 Blood Culture System

BACKGROUND/PURPOSE Identifying the pathogens present in blood stream infections is crucial to initiate appropriate antimicrobial therapy and avoid morbidity and mortality. The aim of this study was to evaluate the effect of overnight storage of aerobic and anaerobic BACTEC 9240 blood culture bottles on the detection time for common pathogens. METHODS From November 2007 to July 2008, a total of 2,105 isolates were positively detected using the BACTEC 9240 system. The time to positive detection (TTD) was calculated by subtracting the time of receipt in the laboratory from the time required to detect a positive culture. The mean TTD values were calculated using the TTD value of the first positive culture bottle only. Overnight delay at the National Cheng Kung University Hospital, Taiwan was 15 hours (from 5 pm to 8 am). RESULTS Of the 2,105 total isolates, 972 (46.1%) were Gram-positive bacteria, 1,024 (48.6%) were Gram-negative bacteria and 109 (5.1%) were fungi. Among the top 10 pathogens, 24.7% grew only in the aerobic bottle and 15.1% in the anaerobic bottle, including Staphylococcus spp., Enterococcus faecium, Enterobacteriaceae, and Gram-positive bacilli. Due to the overnight delay in loading a blood culture bottle into the instrument, for most of the pathogens (including Staphylococcus spp. and Enterobacteriaceae), a decrease in TTD by <or= 4.4 hours was observed. An increase in TTD by 20.8 hours was observed for Gram-positive bacilli. We also found that the difference between TTD in aerobic versus anaerobic bottles during the day was higher in coagulase-negative staphylococcus (12 hours) and lower in Escherichia coli and Staphylococcus aureus (< 2 hours). TTD was longer than 72 hours in 20.5% of Gram-positive bacilli and 7.3% of Candida albicans. CONCLUSION No difference in the TTD of major pathogens was observed in bottles processed during the day and after overnight delay, suggesting that the delayed entry of the blood culture bottle into the instrument may affect the detection time. Since high numbers of facultative anaerobes were detected in anaerobic bottles only, use of a single aerobic bottle might have a detrimental effect on the clinical therapy outcome.

Automated segmentation for patella from lateral knee X-ray images

X-ray image segmentation is an important issue in medical image analysis. Due to inconsistent X-ray absorption, the intensities are usually unevenly distributed and noisy in the processed organ, thus the object segmentation becomes difficult. In this paper we propose a new segmentation method for patella from the lateral knee X-ray images based on the active shape model (ASM). At first, a patella shape model is constructed by principal component analysis (PCA) of corresponding landmarks obtained from a set of training shape. As the knee X-ray image usually contains many anatomical structures, we design a strategy based on edge tracing to place the initial shape model as close to the patella boundary as possible. Then, the shape model is deformed and fitted to the patella boundary by using a dual-optimization approach that includes a genetic algorithm (GA) to get the global geometric transform and ASM to deform the shape model iteratively. Consequently, the proposed method can cope with different knee X-ray images and can segment the patella in an automatic procedure. In the experiment, 20 images were tested and promising results are obtained by the proposed method. This method is found useful for the clinical evaluation and biomechanical study of knee.

Evaluation of the capability of the VITEK 2 system to detect extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates, in particular with the coproduction of AmpC enzymes.

A total of 317 Klebsiella pneumoniae and 291 Escherichia coli nonduplicate isolates were tested by the VITEK 2 system to evaluate its capability to detect extended-spectrum β-lactamases (ESBLs) among putative ESBL-producing isolates, in particular those with the coproduction of AmpC enzymes. β-lactamases produced by the test isolates had been characterised. The sensitivity and specificity for ESBLs were 98.9% and 98.5%, respectively. Ninety of the isolates were AmpC (CMY-2, CMY-8 or DHA-1) and ESBL (SHV and/or CTX-M) coproducers, and 74 isolates (82.2%) of them were flagged as ESBL producers. Our study indicates that the VITEK 2 system is an acceptable tool for ESBL detection among K. pneumoniae and E. coli isolates for laboratories where both imported AmpC and ESBLs are prevalent.