Failure of meropenem therapy for hospital-acquired multiple-resistant Klebsiella pneumoniae urinary tract infection

Abstract number: P1699

Hamouda A., Dancer S., Amyes S.

Objectives: Carbapenem resistance among the Enterobacteriaceae is of great concern as these compounds are considered the last resort for treating infections caused by these bacteria. The purpose of this study was to investigate meropenem-resistance mechanism in a Klebsiella pneumoniae collected from urinary tract infections.

Methods: Two K. pneumoniae strains K1 and K2 were collected from urine on 8th and 13th May 2008 respectively from a septic and catheterised 71-year-old man from Hairmyres Hospital, Lanarkshire treated with meropenem. MICs of antibiotics were performed according to the BSAC guidelines. Isolates found resistant to cefotaxime and ceftazidime were considered as potential ESBL producer and were subsequently subjected to confirmatory tests. ESBL production was confirmed by double and combination disk methods. The blaTEM, blaSHV, blaCTX-M, blaOXA, and blaKPC and metallo-b-lactamses genes were screened by PCR and multiplex PCR respectively and confirmed by sequencing. Pulsed-field gel electrophoresis (PFGE) typing was performed using XbaI restriction endonuclease.

Results:K. pneumoniae strain K2 was resistant to all antibiotics tested except colistin. The MICs (mg/L) were: amikacin (32), gentamicin (>32), tobramycin (>32), ampicillin (>64), aztreonam (>64), cefotaxime (>256), ceftazidime (>256), cefoxitin (>64), cefpirome (>64), ertapenem (128), imipenem (4), meropenem (8), piperacillin (>64), piperacillin/tazobactam (>64), sulbactam (>2), cefotaxime/cloxacillin (>256), colistin (0.5), ciprofloxacin (>8), minocycline (32) and tigecycline (2). K. pneumoniae strain K1 was resistant to ertapenem (16) but susceptible to imipenem and meropenem with MICs of 1 and 0.25 mg/L respectively. ESBL confirmatory tests were positive for both isolates and the presence of blaTEM-1, blaSHV-1, blaCTX-M-15, blaOXA-1 was confirmed by DNA sequencing analysis. No metallo-b-lactamases nor KPC b-lactamases were found. The two K. pneumoniae strains were considered to belong to the same PFGE type.

Conclusion: A case of failed meropenem treatment for hospital-acquired multiply-resistant Klebsiella pneumoniae urinary tract infection producing CTX-M-15 is reported. Resistance to all major antibiotics including tigecycline is consistent with permeability changes including porin loss and upregulated efflux. No carbapenemase could be detected.