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Management of bacteraemia due to carbapenem resistant non-carbapenemase-producing Klebsiella pneumoniae

Abstract number: R2430

Tascini C., Mugnaioli C., Santi S., Gemignani G., Leonildi A., Segantini R., Rossi M., Rossolini G., Menichetti F.

Background: Carbapenem resistance in K. pneumoniae is still uncommon, but may emerge due to several mechanisms. Here we report on two cases of bacteraemia caused by multidrug-resistant (MDR) K. pneumoniae producing an Extended-Spectrum Beta-Lactamase (ESBL) and showing resistance or reduced susceptibility to carbapenems.

Methods: MICs and MBCs of carbapenems were determined as recommended by the CLSI. Susceptibility to other agents was determined by disk diffusion. Serum bacteriostatic (SBA) and bactericidal (SBC) activity against the K. pneumoniae isolated from the same patient were determined according to CLSI. Carbapenemase production was assessed by spectrophotometric assay. Genes encoding ESBLs and outer membrane K35, K36 and K35 proteins were investigated by PCR and sequencing.

Results: Two patients admitted to the same surgical ward developed a post-surgical bacteremic infection due to an MDR K. pneumoniae which was susceptible to imipenem (MIC, 2 mg/L – MBC, 8 mg/L), but intermediate to meropenem (MIC, 8 mg/L – MBC, 16 mg/L) and resistant to ertapenem (MIC, 32 mg/L). Concerning other agents, the isolates were only susceptible to amikacin, tigecycline and polymyxin B. Carbapenemase production was not detectable, while both isolates produced an ESBL (CTX-M-15) plus two broad-spectrum b-lactamases (TEM-1 and SHV-1) and were deficient in OmpK36 due to insertional inactivation of the gene. Before isolation of the MDR klebsiellae, one patient received empiric therapy with ceftriaxone (5 days) and, susbsequently, piperacillin/tazobactam (4 days), while the other patient received meropenem (5 days). When the results of blood cultures were available, one patient was treated with imipenem 1g tid plus amikacin 1g od, and the other with imipenem 1g tid plus tigecycline 50 mg bid. Both regimens were able to resolve fever and bacteraemia, in 36 and 24 hours respectively. At the steady state, peak and through SBA were 1:2 or higher in either case.

Conclusion: Infections due to noncarbapenemase-producing MDR K. pneumoniae producing multiple b-lactamases associated with porin loss retaining susceptibility to imipenem, were successfully treated with imipenem in combination with either amikacin or tigecycline.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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