Gram-negative bacilli with acquired metallo-␤-lactamase (MBL) production have been increasingly reported in some countries, necessitating their detection. The aim of this study was to evaluate the performance of the Hodge test and those of the imipenem (IPM)-EDTA, ceftazidime (CAZ)-mercaptopropionic acid (MPA), and CAZ-sodium mercaptoacetic acid (SMA) double-disk synergy tests (DDSTs). The efficiencies of testing CAZ-resistant and IPM-nonsusceptible isolates were also compared. Strains used for the evaluation were known IMP-1 and VIM-2 MBL-producing isolates and consecutive and CAZ-nonsusceptible isolates of pseudomonads and acinetobacters. The performance of the Hodge test was improved by addition of zinc sulfate (140 g/disk) to an IPM disk. In DDSTs, EDTA (ca. 1,900 g) disks were better at detecting MBL-producing strains among pseudomonads, while MPA (3 l) and SMA (3 mg) disks performed better for acinetobacters. EDTA (ca. 750 g)-plus-SMA (ca. 2 mg) disks performed better than EDTA, MPA, or SMA disks with both organisms. CAZ-SMA DDSTs failed to detect 22 of 80 (28%) MBL-producing acinetobacters. In conclusion, use of an IPM disk and an EDTA (750 g)-plus-SMA (2 mg) disk improves performance, and testing IPMnonsusceptible isolates rather than CAZ-resistant isolates could reduce screening work. Further evaluation of the test is required for the detection of other types of MBL-producing gram-negative bacilli.

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We recently observed the emergence of fluconazole-resistant Candida parapsilosis bloodstream isolates harboring a Y132F substitution in Erg11p in South Korea. These Y132F isolates had a higher propensity to cause clonal transmission than other fluconazole-resistant isolates and persisted within hospitals for several years, as revealed by microsatellite typing.

e Three clinical Pseudomonas aeruginosa isolates (WCH2677, WCH2813, and WCH2837) isolated from the Women's and Children's Hospital, Adelaide, Australia, produced a metallo-␤-lactamase (MBL)-positive Etest result. All isolates were PCR negative for known MBL genes. A gene bank was created, and an MBL gene, designated bla AIM-1 , was cloned and fully characterized. The encoded enzyme, AIM-1, is a group B3 MBL that has the highest level of identity to THIN-B and L1. It is chromosomal and flanked by two copies (one intact and one truncated) of an ISCR element, ISCR15. Southern hybridization studies indicated the movement of both ISCR15 and bla AIM-1 within the three different clinical isolates. AIM-1 hydrolyzes most ␤-lactams, with the exception of aztreonam and, to a lesser extent, ceftazidime; however, it possesses significantly higher k cat values for cefepime and carbapenems than most other MBLs. AIM-1 was the first mobile group B3 enzyme detected and signals further problems for already beleaguered antimicrobial regimes to treat serious P. aeruginosa and other Gram-negative infections.T he continuing increase in antibiotic resistance in Gram-negative bacteria is of concern, not least because of the increasing lack of therapeutic options available to treat infections caused principally by Pseudomonas aeruginosa and Acinetobacter baumannii (3,17,21). This phenomenon has been exacerbated by the dissemination of metallo-␤-lactamases (MBLs) that can confer resistance to nearly all ␤-lactams, with the exception of aztreonam (4,5,43).Like many resistance mechanisms, MBLs can be encoded by either genes ubiquitously carried on the chromosome or mobile genes (39). The latter genes now include the following subgroups: IMP (15), VIM (26), SPM-1 (36), GIM-1, SIM-1, KMH-1 (25), , and the recently described NDM-1 (44). So far, they all belong to MBL subgroup B1. MBL genes are often embedded in class 1 integrons and are carried as gene cassettes. It has also been shown that while many MBL genes are plasmid mediated, some are carried on the chromosome and can be associated with Tn21-like transposons or Tn402 transposons (30, 34). However, SPM-1 is not associated with a standard integron but is flanked by two genetic elements, designated ISCR4 (18). ISCR elements are IS91-like mobile elements and can potentially mobilize and duplicate bla SPM-1 via rolling-circle replication (33, 37).The B3 subgroup MBLs have hitherto been reported for environmental bacteria, only some of which can cause opportunistic infections. These include Stenotrophomonas maltophilia (L1) (42), Janthinobacterium lividum (THIN-B) (23), Chryseobacterium meningosepticum (GOB-1) (1), Legionella gormanii (FEZ-1) (2), Caulobacter crescentus (CAU-1) (10), CAR-1 from Erwinia carotovora (29), POM-1 (32), and the recently reported ISCR1-associated SMB-1 (38). The MBL genes carried by these environmental bacteria encode subgroup B3 MBLs that are not closely related to the mobile B1 members (43). They are often GC rich and 2 to 3 kDa larger than the B1 subgroup members...