CMT-type beta-lactamase TEM-125, an emerging problem for extended-spectrum beta-lactamase detection.

The clinical strain Escherichia coli TO799 was resistant to penicillin-clavulanate combinations and ceftazidime and was not reproducibly detected as an extended-spectrum beta-lactamase (ESBL) according to the standards of the Clinical Laboratory Standards Institute (CLSI; formerly NCCLS) and the national guidelines of the French Society for Microbiology (Comité de l'Antibiogramme de la Société Française de Microbiologie). A novel beta-lactamase, designated TEM-125, was responsible for this phenotype. TEM-125 harbors a complex association of mutations previously described in the ESBL TEM-12 and in the inhibitor-resistant beta-lactamase TEM-39. TEM-125 is the first complex mutant TEM to present hydrolytic activity against ceftazidime (kcat, 3.7 s(-1)) together with a high level of resistance to clavulanate (50% inhibitory concentration, 13.6 microM). The discovery of such an ESBL, which is difficult to detect by the usual ESBL detection methods, confirms the emergence of a complex mutant TEM subgroup and highlights the need to evaluate detection methods so as to avoid possible therapeutic failures.

Risk of emergence of Pseudomonas aeruginosa resistance to beta-lactam antibiotics in intensive care units.

OBJECTIVE: The emergence of Pseudomonas aeruginosa resistance to antimicrobial drugs is frequent in intensive care units and may be correlated with the use of some specific drugs. The purpose of our study was to identify a relationship between the use of various beta-lactam antibiotics and the emergence of resistance and to characterize the mechanism of resistance involved. DESIGN: We conducted an open prospective study over a 3-yr period by including all patients in whom P. aeruginosa had been isolated from one or more specimens: bronchial aspiration, blood cultures, catheters, and urinary cultures. SETTING: General intensive care unit. PATIENTS: One hundred and thirty-two intensive care unit patients. INTERVENTIONS: The antibiotics studied were amoxiclav, piperacillin-tazobactam, cefotaxime, ceftazidime, cefepim, and imipenem. The mechanisms of resistance studied were production of penicillinase or cephalosporinase, nonenzymatic mechanisms, and loss of porin OprD2. Analysis was performed using Cox proportional-hazard regression with time-dependant variables. MEASUREMENTS AND MAIN RESULTS: Forty-two strains became resistant, 30 to one antibiotic, nine to two, and three to three, leading to the study of 57 resistant strains. Imipenem (hazard ratio 7.8; 95% confidence interval, 3.4-18.1), piperacillin-tazobactam (hazard ratio 3.9; 95% confidence interval, 1.3-11.9), and cefotaxim (hazard ratio 9.3; 95% confidence interval, 2.9-30.2) were strongly linked to the emergence of resistance. The use of imipenem (p<.0001) was associated with the loss of porin OprD2. Thirty-six strains from nine patients, assayed by pulsed-field gel electrophoresis, showed that for any one patient, all the strains were genetically related. CONCLUSIONS: Our results show that there is a high risk of the emergence of drug resistance during treatment with cefotaxime, imipenem, and piperacillin-tazobactam. This has to be taken into account in the therapeutic choice and in the patient's surveillance.

Successful treatment of Staphylococcus epidermidis hip prosthesis infection with oral linezolid.

OBJECTIVE: To report a case of Staphylococcus epidermidis infection of a hip prosthesis successfully treated with oral linezolid. CASE SUMMARY: A 46-year-old woman developed methicillin-resistant S. epidermidis (MRSE) infection of her prosthetic hip. She received oral linezolid 600 mg twice daily for one month; after that time, the biological inflammatory markers returned to normal. DISCUSSION: One of the most serious complications of arthroplasty is joint prosthesis infection. It is mainly caused by gram-positive bacteria, in particular those of the genus staphylococcus. The increasing prevalence of gram-positive cocci that are resistant to antimicrobial agents has complicated the treatment of serious infections. CONCLUSIONS: Oral linezolid appears to be an effective and well-tolerated treatment option for hip prosthesis infections due to MRSE.