RAHN-2, a chromosomal extended-spectrum class A beta-lactamase from Rahnella aquatilis.
OBJECTIVE
Rahnella aquatilis is an environmental enterobacterial species with a chromosomal bla(RAHN-1) gene encoding extended-spectrum class A beta-lactamase RAHN-1. We describe the diversity of bla(RAHN) genes from two groups of strains, G1 and G2, isolated from raw fruits and vegetables, and the new class A beta-lactamase RAHN-2.


METHODS
MICs were determined by Etest. bla(RAHN) genes were amplified by PCR, sequenced, and cloned to produce RAHN-1 and RAHN-2 proteins whose kinetic parameters were determined.


RESULTS
All strains had similar beta-lactam resistance patterns. However, isolates of G1 were at least 2-fold more susceptible to piperacillin, amoxicillin, piperacillin/clavulanic acid, piperacillin/tazobactam and cefotaxime. Sequences of bla(RAHN) from G1 had <82.9% identity with that of bla(RAHN-1), whereas those of G2 were >92% identical. The RAHN-2 beta-lactamase was 89.8% identical to RAHN-1, 5-fold more efficient than RAHN-1 in hydrolysing ticarcillin and 2.5-fold more efficient in cefotaxime and cefuroxime hydrolysis. However, the specific activity of RAHN-1 was 2-fold higher than that of RAHN-2 suggesting that the bla(RAHN) genes are regulated differently.


CONCLUSIONS
The new class A beta-lactamase RAHN-2 is phenotypically difficult to detect and requires MIC determination.
EA 3964, Université Paris Diderot, Centre National de Référence de la Résistance aux Antibiotiques, Hôpital Bichat Claude Bernard, APHP, 75018 Paris, France. raymond.ruimy@bch.aphp.fr
Raymond
R
Ruimy
Djalal
D
Meziane-Cherif
Sonia
S
Momcilovic
Guillaume
G
Arlet
Antoine
A
Andremont
Patrice
P
Courvalin
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005638:Fruit / Q000382:microbiology; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D020638:Rahnella / Q000187:drug effects / Q000201:enzymology*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014675:Vegetables / Q000382:microbiology; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D047090:beta-Lactams / Q000378:metabolism / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D047090:beta-Lactams; D001618:beta-Lactamases