Production of extended-spectrum -lactamases and plasmid-mediated AmpC enzymes was investigated among 291 Escherichia coli and 282 Klebsiella pneumoniae isolates that showed decreased susceptibilities to extended-spectrum cephalosporins from seven Taiwanese medical centers. CTX-M-type and SHV-type enzymes were the most prevalent extended-spectrum -lactamases. CMY-2-like and DHA-1-like -lactamases were the most prevalent AmpC-type enzymes.The increasing prevalence of extended-spectrum -lactamases (ESBLs) and plasmid-mediated AmpC -lactamases in members of the family Enterobacteriaceae is a matter of great concern worldwide (1, 2, 10). In Taiwan, TEM-, SHV-, and CTX-M-type ESBLs and CMY-and DHA-type AmpC -lactamases have been reported in Escherichia coli and Klebsiella pneumoniae isolates from a few individual institutions (3,(17)(18)(19)(20). The present multicenter study was conducted to determine the distribution of ESBLs and AmpC -lactamases among clinical isolates of E. coli and K. pneumoniae that showed decreased susceptibilities to extended-spectrum cephalosporins in Taiwan.Isolates that were suspected of ESBL production by the CLSI (formerly NCCLS) screening method (8) with disks of ceftazidime, cefotaxime, ceftriaxone, aztreonam, and/or cefpodoxime were considered to exhibit decreased susceptibilities to extended-spectrum cephalosporins and consecutively collected between March and August 2003 from seven medical centers in Taiwan. These hospitals were chosen because they represent the largest referral medical centers in each region of Taiwan. A total of 291 E. coli and 282 K. pneumoniae isolates were obtained (Table 1). Each isolate came from a unique patient.All isolates were tested for ESBL production by the CLSIrecommended disk diffusion confirmatory test (8), and 171 E. coli and 260 K. pneumoniae isolates were considered ESBL producers. All putative non-ESBL producers were tested further by the double-disk synergy test with ceftazidime, cefotaxime, aztreonam, and cefepime disks placed 20 mm from an amoxicillin-clavulanate disk (13). The method has been shown to be capable of detecting false negatives which are caused by coproduction of different classes of -lactamases in the CLSI method (20). Five E. coli and five K. pneumoniae isolates gave a positive result in the double-disk synergy test. Thus, ESBL production was detected in 176 (60.5%) of the 291 E. coli isolates and 265 (94.0%) of the 282 K. pneumoniae isolates.The expression of -lactamases was detected by isoelectric focusing as described previously (6,18). PCR was performed with the previously reported oligonucleotide primers to detect bla TEM (5), bla SHV (9), and bla genes related to bla CTX-M-1 (12), bla CTX-M-9 (12), bla CMY-1 (17), bla CMY-2 (16), bla DHA-1 (4), and bla . The PCR-NheI method was used to discriminate between bla SHV-ESBL and bla SHV-non-ESBL genes (9).Overall, the production of ESBLs and AmpC-like enzymes was confirmed in 60.5% (176 isolates) and 43.6% (127 isolates), respectively, of the 291 E. coli isolates, and ...
The aim of the investigation was to describe the incidence of Aeromonas bacteremia in a city with a population of about 1.87 million inhabitants, located in southern Taiwan, between 2008 and 2010. Such data were compared with the incidences of Vibrio and Salmonella bacteremia in the same period and the incidence of Aeromonas bacteremia in other countries in the literature. The data revealed the average annual incidences of bacteremia due to Aeromonas, Vibrio, and Salmonella species were 76, 38, and 103 cases/million inhabitants, respectively. The incidence of Aeromonas bacteremia was higher than those in Western countries.
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.
This study demonstrated the occurrence of qnrB2 and qnrS1 in Salmonella for the first time in Taiwan and characterized their genetic structures.
The feasibility of sequence analysis of the ribosomal 16S-23S intergenic spacer region (ITS) was evaluated for identification of 24 species of Streptococcus, one species of Abiotrophia, 18 species of Enterococcus and three species of Granulicatella. As GenBank currently lacks ITS sequence entries for many species of these four genera, the ITS sequences of 38 type strains were first sequenced and submitted to GenBank to facilitate species identification of these genera. Subsequently, the ITS sequences of 217 strains (84 reference strains and 133 clinical isolates) were determined and species identification was made by BLAST search for homologous sequences in public databases. Species other than Streptococcus contained multiple ITS fragments and only the shortest fragment was analysed. A total of 25 isolates (11.5 %) produced discrepant identification by ITS sequencing. The 25 discordant strains were analysed further by sequencing of the 16S rRNA gene for species clarification, and 21 were found to be identified correctly by ITS sequence analysis. The correct identification rate by ITS sequencing was 98.2 % (213/217). Several closely related enterococcal and streptococcal species/subspecies contained specific ITS signature sequences that were useful for differentiating these bacteria. In conclusion, ITS sequencing provides a useful approach towards identifying this group of pathogens on a molecular platform alongside 16S rRNA gene sequencing.
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