Hsiu-Mei Wu

Outbreak of Infection with Multidrug-Resistant Klebsiella pneumoniae Carrying bla IMP-8 in a University Medical Center in Taiwan

ABSTRACT Klebsiella pneumoniae strains with the transferable carbapenem-hydrolyzing metallo-β-lactamases, which include IMP- and VIM-type enzymes, remain extremely rare. To investigate whether IMP- or VIM-producing K. pneumoniaeisolates had spread at a university medical center in Taiwan, a total of 3,458 clinical isolates of K. pneumoniaeconsecutively collected in 1999 and 2000 were tested by the agar diffusion method, colony hybridization, PCR, and nucleotide sequencing. A total of 40 isolates (1.2%), or 17 nonrepetitive isolates, from 16 patients were found to carry blaIMP-8, a metallo-β-lactamase gene recently identified from a K. pneumoniae strain in Taiwan. Carriage ofblaVIM or otherblaIMP genes was detected in none of the remaining isolates. Of the 17 nonrepetitiveblaIMP-8-positive isolates, 15 isolates (88.2%) appeared susceptible to imipenem (MICs, ≤4 μg/ml) and meropenem (MICs, ≤1 μg/ml), indicating the difficulty in detecting blaIMP-8 in K. pneumoniae by routine susceptibility tests; 14 isolates (82.4%) produced SHV-12 as well; and 14 isolates (82.4%) were also resistant to fluoroquinolones. The organisms caused wound infections in eight patients and bloodstream infections in three patients. They were not directly associated with the death of nine patients. Before the recovery of the blaIMP-8-positive isolates, all 16 patients had undergone various surgical procedures, and 15 patients had been admitted to the surgical intensive care unit, suggesting a nosocomial outbreak. Two major patterns were observed by pulsed-field gel electrophoresis for 14 of the 17 nonrepetitive isolates, indicating that the clonal spread was mainly responsible for the outbreak.

Prevalence of primary fluoroquinolone resistance among clinical isolates of Helicobacter pylori at a University Hospital in Southern Taiwan.

Background:  Fluoroquinolone‐containing therapy is effective in eradicating Helicobacter pylori. However, the resistance rate of H. pylori to fluoroquinolones in Taiwan has not yet been reported. In this study, we aimed to investigate the susceptibility to antibiotics commonly used in eradication schedules and fluoroquinolones in H. pylori.

Emergence of Ceftriaxone-Resistant Salmonella Isolates and Rapid Spread of Plasmid-Encoded CMY-2–Like Cephalosporinase, Taiwan

Of 384 Salmonella isolates collected from 1997 to 2000 in a university hospital in Taiwan, six ceftriaxone-resistant isolates of Salmonella enterica serovar Typhimurium were found in two patients in 2000. The resistance determinants were on conjugative plasmids that encoded a CMY-2–like cephalosporinase. During the study period, the proportion of CMY-2–like enzyme producers among Escherichia coli increased rapidly from 0.2% in early 1999 to >4.0% in late 2000. Klebsiella pneumoniae isolates producing a CMY-2–like β-lactamase did not emerge until 2000. The presence of blaCMY-containing plasmids with an identical restriction pattern from Salmonella, E. coli, and K. pneumoniae isolates was found, which suggests interspecies spread and horizontal transfer of the resistance determinant. Various nosocomial and community-acquired infections were associated with the CMY-2–like enzyme producers. Our study suggests that the spread of plasmid-mediated CMY-2–like β-lactamases is an emerging threat to hospitalized patients and the public in Taiwan.

Complexity of Klebsiella pneumoniae Isolates Resistant to Both Cephamycins and Extended-Spectrum Cephalosporins at a Teaching Hospital in Taiwan

ABSTRACT Among 99 clinical Klebsiella pneumoniae isolates resistant to cefoxitin and extended-spectrum cephalosporins, coexistence of AmpC (DHA-1, CMY-2, or CMY-8) and extended-spectrum β-lactamases (CTX-M and/or SHV) was detected in a total of 35. The remainder produced AmpC (n = 42), extended-spectrum β-lactamases (n = 9), metallo-β-lactamases (n = 2), or none of these enzymes (n = 11). Phenotypic characteristics of these isolates were demonstrated.

Prevalence of Qnr determinants among bloodstream isolates of Escherichia coli and Klebsiella pneumoniae in a Taiwanese Hospital, 1999–2005

OBJECTIVES To determine the prevalence and characteristics of bloodstream isolates of Escherichia coli and Klebsiella pneumoniae with qnr genes in a Taiwanese hospital. METHODS A total of 2035 E. coli and 1147 K. pneumoniae isolates collected between 1999 and 2005 were screened for qnrA, qnrB and qnrS by PCR and colony hybridization. Beta-lactamase genes, genetic relatedness and transferability were examined by PCR, PFGE and conjugation, respectively. RESULTS The prevalence of qnr genes was 7.8% and 0.6% for K. pneumoniae and E. coli, respectively. The prevalence rates of qnrB2, qnrB4 and qnrS1 genes for K. pneumoniae were 2.3%, 3.6% and 2.8%, respectively, and for E. coli were 0.2%, 0% and 0.4%, respectively. The prevalence of qnrB4 in K. pneumoniae increased remarkably from 0% to 7.6% over the 7 study years. qnrA was not detected. Overall, the SHV-5-related, CTX-M-14, CTX-M-3, CMY-2, DHA-1 and IMP-8 beta-lactamases were detected alone or in combination in 82.0% of qnr-positive K. pneumoniae isolates and 41.7% of qnr-positive E. coli isolates. Notably, all qnrB4-positive isolates possessed the DHA-1 enzyme, and the majority of the qnrB2-positive isolates (E. coli, 100%; K. pneumoniae, 80.8%) produced SHV-5-related beta-lactamases. Genetic diversity was demonstrated by PFGE. Conjugation experiments revealed co-transfer of bla(SHV-12), bla(DHA-1) and bla(SHV-5) with qnrB2, qnrB4 and qnrS1, respectively. CONCLUSIONS qnr genes remained rare in E. coli but appeared to be increasing in K. pneumoniae in our hospital. Horizontal transfer may play a major role in the intra-hospital spread of qnr.

Molecular Analysis of Group A Streptococcal Isolates Associated with Scarlet Fever in Southern Taiwan between 1993 and 2002

ABSTRACT Collected between 1993 and 2002 at a Taiwanese university hospital, 77 group A streptococcus isolates associated with scarlet fever were grouped by emm typing and pulsed-field gel electrophoresis. The predominance of an emm1 clone before 1996 and the presence of genetically diverse emm1 and emm4 strains thereafter were found.

Molecular characterization of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella spp. isolates in Mongolia

BACKGROUND/PURPOSE The aim of this study was to determine the molecular characteristics of β-lactamase genes in extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae isolates from Mongolia. METHODS Fifty-six ESBL-producing Enterobacteriaceae isolates were collected, of which 46 were Escherichia coli, seven were Klebsiella pneumoniae, and three were K. oxytoca. Minimum inhibitory concentrations for selected antibiotics were tested using the agar dilution method, and the β-lactamase genes were determined using polymerase chain reaction combined with sequencing. Pulsed-field gel electrophoresis (PFGE) was used for genotyping all isolates, and phylogenetic grouping was performed on ESBL-producing E. coli isolates. Conjugation tests combined with plasmid digestion assays were used to determine whether there was a horizontal spread in Mongolia. RESULTS Among the 56 ESBL-producing isolates, 43 isolates (76.8%) were resistant to fluoroquinolones, but all isolates were susceptible to carbapenems and amikacin. The polymerase chain reaction sequencing results showed that the dominant CTX-M genotype was CTX-M-15 (19/46, 41.3%) in the ESBL-producing E. coli isolates. By contrast, CTX-M-14 and CTX-M-3 were the major genotypes found in Klebsiella spp. Phylogenetic analysis revealed that 21 ESBL-producing E. coli isolates belonged to group D (21/46, 45.6%), followed by group A (13/46, 28.3%), group B2 (11/46, 23.9%), and group B1 (1/46, 2.2%). Only four E. coli isolates (4/46, 8.7%) belonged to the ST131 clone. PFGE showed that the ESBL-producing Enterobacteriaceae were genetically unrelated. The conjugation assay showed that two plasmids harboring CTX-M-15 in E. coli isolates were genetic unrelated, whereas seven plasmids harboring CTX-M-14 (5/7 and 2/7) and four plasmids harboring CTX-M-55 (4/4) showed genetic relatedness, indicating the dissemination of resistance plasmids in this area.

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.