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A total of 209 clinical isolates of Pseudomonas (193 Pseudomonas aeruginosa, 10 P. putida, 4 P. stutzeri, and 2 P. fluorescens isolates) with reduced susceptibilities to imipenem and/or ceftazidime were subjected to PCR assays with primers specific for bla IMP-1 , bla IMP-2 , bla VIM-1 , and bla VIM-2 and sequence analysis to identify the metallo-␤-lactamases (MBLs) prevalent among these organisms in Taiwan; and 21 isolates gave positive results. Five isolates including two P. putida and three P. stutzeri isolates were found to carry bla IMP-1 , and six isolates including five P. putida and one P. stutzeri isolates harbored bla VIM-2 . The remaining 10 isolates were P. aeruginosa, and all were found to carry a novel variant of bla VIM-2 , designated bla VIM-3 . There are only two nucleotide differences between bla VIM-2 and bla VIM-3 , leading to two amino acid alterations. Our findings indicate that VIM-2 and its variant have become the most prevalent metalloenzymes in Pseudomonas in Taiwan. Southern hybridization with the bla VIM-2 -, bla VIM-3 -, and bla IMP-1 -specific probes revealed that only two VIM-2-producing P. putida isolates appeared to carry the MBL gene on plasmids. Pulsed-field gel electrophoresis showed that six VIM-3-producing P. aeruginosa isolates and two IMP-1-producing P. stutzeri isolates were genetically related, suggesting that the spread of these MBL genes in Taiwan could be due to clonal dissemination as well as genetic exchange between different clones.Carbapenems are often used as antibiotics of last resort for the treatment of infections caused by gram-negative bacteria resistant to other ␤-lactam agents because of their broad spectra of activity and stability to hydrolysis by most ␤-lactamases including extended-spectrum ␤-lactamases (4,12,26,27). The mechanisms of resistance to carbapenems in Pseudomonas aeruginosa often result from reduced levels of drug accumulation or increased levels of expression of pump efflux (8,15,17). The resistance is occasionally due to production of metallo-␤-lactamases (MBLs), which can be either chromosomally encoded or plasmid mediated (8,13,22,28,32). IMP-1 was the first MBL identified in P. aeruginosa (28,29). The enzyme has also been described in other nonfastidious, gram-negative nonfermenters and members of the family Enterobacteriaceae (9,10,20,29). Several novel MBLs were identified recently, including VIM-1 from P. aeruginosa and IMP-2 from Acinetobacter baumannii in Italy (13, 25), VIM-2 from P. aeruginosa in France (22), and IMP-3 from Shigella flexneri in Japan (11). The spread of MBLs in gram-negative rods has been described in several other countries and is becoming an emerging threat , abstr. 2003, p. 123, 2000). It remains unknown whether these MBLs have appeared in Taiwan. Thus, the purpose of the present study was to determine the IMP-and VIM-type MBLs prevalent among clinical isolates of the genus Pseudomonas in Taiwan. MATERIALS AND METHODSBacterial strains. The isolates studied were selected from clinical isolates of Pseudomonas ...

This study was conducted to evaluate the relationship between antimicrobial resistance and antimicrobial use in a university hospital in Taiwan. Disk susceptibility data of Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Proteus spp., Pseudomonas aeruginosa, Acinetobacter spp., Stenotrophomonas maltophilia and other non-fermentative Gram-negative bacilli causing nosocomial infections were evaluated. Data on annual patient-days and annual consumption (defined daily dose (DDD) per 1000 patient-days) of extended-spectrum cephalosporins (cefotaxime, ceftriaxone, ceftazidime, flumoxef, cefepime and cefpirome), beta-lactam-beta-lactamase inhibitor combinations (ticarcillin/clavulanic acid and piperacillin/tazobactam), carbapenems (imipenem and meropenem), aminoglycosides (amikacin, gentamicin and tobramycin), fluoroquinolones (ciprofloxacin (oral and injectable) and oral levofloxacin and moxifloxacin) from 1991 to 2003 were analysed. Increasing trends of incidences of several of these bacteria causing all nosocomial infections or nosocomial bloodstream infections were noted from 1991 to 2003. The annual patient-days of the hospital significantly increased, from 360210 in 1991 to 672676 in 2002 (linear regression analysis, P < 0.05), but slightly decreased in 2003 (629168) owing to the severe acute respiratory syndrome epidemic in Taiwan. The rise in cefotaxime-resistant or ciprofloxacin-resistant E. coli and meropenem-resistant P. aeruginosa was significantly correlated with increased consumption of extended-spectrum cephalosporins, beta-lactam-beta-lactamase inhibitor combinations, carbapenems, fluoroquinolones and aminoglycosides (for ciprofloxacin-resistant E. coli and meropenem-resistant P. aeruginosa only) in the hospital (Pearson's correlation coefficient, r > 0.72 (or < -0.72) and P-value < 0.05). Increased ciprofloxacin-resistant K. pneumoniae and meropenem-resistant Acinetobacter spp. was significantly associated with the increased usage of extended-spectrum cephalosporins but not with the other four classes of antibiotics. This 13-year study in a hospital demonstrated significant changes in antimicrobial use, which may have affected antimicrobial resistance in certain Gram-negative bacteria at the hospital.

SummarySerratia marcescens SS-1 produces at least four N -acylhomoserine lactones (AHLs) which were identified using high-resolution mass spectrometry and chemical synthesis, as N-(3-oxohexanoyl) homoserine lactone (3-oxo-C6-HSL), N -hexanoyl-(C6-HSL), N -heptanoyl (C7-HSL) and N -octanoyl-(C8-HSL) homoserine lactone. These AHLs are synthesized via the LuxI homologue SpnI, and regulate via the LuxR homologue SpnR, the production of the red pigment, prodigiosin, the nuclease, NucA, and a biosurfactant which facilitates surface translocation. spnR overexpression and spnR gene deletion show that SpnR, in contrast to most LuxR homologues, acts as a negative regulator. spnI overexpression, the provision of exogenous AHLs and spnI gene deletion suggest that SpnR is de-repressed by 3-oxo-C6-HSL. In addition, long chain AHLs antagonize the biosurfactantmediated surface translocation of S. marcescens SS-1. Upstream of spnI there is a gene which we have termed spnT . spnI and spnT form an operon and although database searches failed to reveal any spnT homologues, overexpression of this novel gene negatively affected both sliding motility and prodigiosin production.

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