Emerging colimycin resistance in Gram-negative strains isolated from intensive care unit patients

Abstract number: 1733_1158

Kontopidou F.V., Antoniadou A., Poulakou G., Papadomichelakis E.D., Galani I., Armaganidis A., Giamarellou H.

Background: Infections due to multidrug resistant (MDR) Gram(-) microorganisms in the ICUs has prompted the use of Colimycin (COL) an antibiotic forgotten for decades. The mechanism of COL resistance (COL R) has not been well defined. Until now resistance to COL is uncommon. While emergence of COL R in vivo, has not yet been reported.

Patients and Methods: The study was performed in a new 6-bed general ICU from November 2003 to October 2006. Empirical antimicrobial treatment was guided by weekly active surveillance of patients floras (faecal and respiratory). Resistance of the isolated pathogens prompted COL use as part of empirical antimicrobial regimens or in microbiologically documented infections. COL R was defined as <14 mm diameter by the disk diffusion method and was confirmed as an MIC > 4 mg/mL by the agar dilution and E test method (according to BSAC).

Results: Among 146 patients with more than 10 days hospitalisation, 72% was colonised by A. baumannii, 61% by P. aeruginosa, 50% by K. pneumoniae, 17% by Enterobacter spp., 28% by E. coli, 27% by S. maltophilia. The resistant strains to COL were 3.8%, 4.5%, 32.4%, 4%, 7.3%, 35% respectively. Using REP-PCR six distinct clones were identified among K. pneumoniae Col resistant strains. Most of K. pneumoniae strains were pan-drug resistant, produsing ESBL and MBL susceptible only to tetracyclines or and gentamycin. The majority represented colonisation; only 7 cases of infection were recorded (six with K. pneumoniae and one with Enterobacter sp), all of them with fatal outcome. 83 patients had exposure to colistin, 29 of them harbouring a colistin resistant Gram(-) strain. All patients treated prolonged (>20 d) with Col developed normal floras colonisation with K. pneumoniae, P. aeruginosa, S. maltophilia R to Col plus of intrinsically resistant to Col enterobacteriaceae (ie. Pr. mirabilis, M. morgani, Serratia spp., and Providencia spp.). Colonisation with more than one Col resistant pathogen correlated with length of stay, severity of illness and a significant exposure to colistin.

Conclusions: Selective pressure due to extensive COL use seems to lead to the emergence of COL resistance among Gram(-) strains, jeopardising treatment choices in the ICU, increasing morbidity and mortality. Therefore it is urgent intensivists to avoid unecessar or/and prolonged therapy with colistin.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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