Characterization of IncA/C conjugative plasmid harboring bla TEM-52 and bla CTX-M-15 extended-spectrum ß-lactamases in clinical isolates of Escherichia coli in Tunisia.

To characterize the extended-spectrum ß-lactamases (ESBLs) as well as their genetic environment in different isolates of Escherichia coli from patients with repeated urinary tract infections, large multidrug resistance (MDR) plasmids have been found. Definitive evidence for the presence of an A/C incompatibility complex (IncA/C) plasmid in the MDR isolates was provided by the probing of plasmids extracted from the clinical isolates. Conjugation experiments showed that bla genes were transferred by conjugation from the ten E. coli clinical isolates to E. coli XL1-Blue recipient. A comparative restriction fragment length polymorphism (RFLP) analysis of these plasmids showed that they are genetically similar, while the overall similarity of these plasmids supports the likelihood of recent movements among these E. coli isolates. Polymerase chain reaction (PCR) amplification and sequencing of the amplicons showed that the IncA/C plasmids harbor two ESBLs, identified as TEM-52 and CTX-M-15. Analysis of the plasmid DNA surrounding the bla (CTX-M-15) gene in the clinical isolates under study revealed a partially truncated fragment of ISEcp1 tnpA transposase. This result indicates the variety of genetic events that have enabled associations between ISEcp1 sequences and bla (CTX-M-15) genes in these clinical isolates.

Identification of plasmid-encoded extended spectrum beta-lactamases produced by a clinical strain of Proteus mirabilis.

Emergence and dissemination of multiresistant strain of Proteus mirabilis have made infections treatment more difficult that this bacterium is responsible. The aim of this study is to determine the implication of the enzymatic mechanism and to describe the properties of ESBLs (extended spectrum beta-lactamases). A clinical strain of Proteus mirabilis SM514 isolated in the intensive care unit at the Military hospital in Tunisia during the period 2004 was found to be highly resistant to cephalosporins and penicilins. Cells sonicate of the isolate hydrolysed cefotaxime more efficiently than ceftriaxone and ceftazidime and had three beta-lactamases bands of approximate of isoelectric points (pI) of 5.4; 5.6 and superior to 7.6. The specific activities (AS) vary from 5.26 to 7.77U/mg of protein respectively for cefotaxime and the benzylpenicillin. These activities are inhibited by the clavulanic acid and the sulbactam. The values of the IC(50) are respectively 3.7 and 11.7muM. Only the beta-lactamases of pI 5.4 and superior to 7.6 hydrolyze the cefotaxime. Transformant produces the ESBLs of pI 5.4; 7.45 and greater than 7.6. The genes coding for this enzymes are carried by a transferable plasmids.

WITHDRAWN: [Clinical strain of Proteus mirabilis able to produce a plasmid mediated ceftazidimase.] / Identification d'une ceftazidimase plasmidique produite par une souche clinique de Proteus mirabilis.

Resistance to third generation cephalosporins due to the acquisition and expression of extended spectrum beta-lactamases (ESBLs) enzymes among Gram negative bacteria continue to pose a challenge to infection management worldwide. The aim of this study was to determine the implication of the enzymatic mechanism and to describe the properties of ESBLs from a clinical strain of Proteus mirabilis NC4150 isolated in the intensive care unit at the Military Hospital in Tunisia during the period 2004. The isolate was identified, tested for antimicrobial susceptibility and analysed for presence of ESBL genes. Two beta - lactamases which confers a multirésistance on antibiotics including the oxyimino beta-lactams were identified. Isoelectric points of these two beta-lactamases are 5.4 and 5.7. The specific activities (AS) vary from 0.2 to 36.27 U/mg of protein respectively for ampicilline and the ceftazidime. These activities are inhibited by the clavulanic acid and the sulbactam. The values of the IC 50 are respectively 16 muM and 2.4 mu M. Only the beta - lactamase of pI 5.7 hydrolyze the ceftazidime. Transformant and transconjugant produces only the ESBL (extended spectrum beta-lactamases) of pI 5.7. The gene coding for this enzyme is carried by a transferable plasmid named pNC4150.