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.
Ruimy
Raymond
R
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
Meziane-Cherif
Djalal
D
Momcilovic
Sonia
S
Arlet
Guillaume
G
Andremont
Antoine
A
Courvalin
Patrice
P
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