2250. Effect of the cyclic octasaccharide octakis(6-deoxy-6-amino)cyclomaltooctaose (am8γCD) on the sensitivity of carbapenem-resistant Klebsiella pneumomiae to complement-mediated killing.
Session: Poster Abstract Session: New Antibiotics in Development
Saturday, October 29, 2016
Room: Poster Hall
  • Mediavilla IDWeek poster #2250.pdf (1.1 MB)
  • Background: The global spread of carbapenem resistance and the recent identification of plasmid-encoded colistin resistance in Gram-negative Enterobacteriaceae have dramatically limited effective treatment options, thereby prompting a call for novel approaches that circumvent antibiotic resistance. A recent study (Kong et al., 2013) demonstrated that the cyclodextrin octakis(6-deoxy-6-amino)cyclomaltooctaose (am8γCD) interferes with K30 capsular polysaccharide (CPS) export by Escherichia coli efflux channel Wza, and enhances sensitivity to complement-mediated killing. We extended these studies to Klebsiella pneumoniae, a clinically important multidrug-resistant pathogen which possesses a similar Wzy-dependent CPS biosynthesis pathway.

    Methods: Wza sequences from 183 clinical K. pneumoniae strains were aligned, and 50 representative strains corresponding to 18 K. pneumoniae multilocus sequence types were selected for complement-mediated killing assays in the presence and absence of am8γCD. Assays were conducted in triplicate with 104-fold dilutions of overnight culture. Test conditions included: a) RPMI medium, b) 40% (pooled) human serum, c) 40% human serum with 0.1 mM am8γCD, d) 40% human serum with 1 mM am8γCD, and e) 40% deactivated human serum. Mixtures were incubated at 37ºC for 1 hour and plated overnight for colony-forming units.

    Results: Of the 50 strains, 32 were sensitive (64.0%), 10 (20.0%) displayed intermediate sensitivity, and 8 (16.0%) were resistant to both serum and am8γCD. Among the sensitive strains, 6 were highly sensitive to both serum and am8γCD, 4 were sensitive to am8γCD only, and 1 was sensitive only to 1 mM am8γCD. Strains with identical Wza sequences generally exhibited similar phenotypes, with few exceptions (n=7). Further experiments with knock-out mutants (Δwza, Δwzy) resulted in complete sensitivity, with resistance restored after complementation of wild-type wza and wzy.

    Conclusion: Our findings demonstrate that K. pneumoniae strains exhibit different cyclodextrin-dependent responses to human complement, with most displaying sensitive phenotypes. These differences may be further exploited to identify novel molecules that interfere with capsular biosynthesis, offering an alternative approach to antibacterial intervention.

    Jose R. Mediavilla, MPH, MBS1, Ruchi Pandey, PhD1, Scott S. Walker, PhD2, Christopher M. Tan, PhD2 and Barry N. Kreiswirth, PhD1, (1)Public Health Research Institute, Rutgers University, Newark, NJ, (2)Merck Research Laboratories, Kenilworth, NJ


    J. R. Mediavilla, None

    R. Pandey, None

    S. S. Walker, None

    C. M. Tan, Merck: Employee and Shareholder , Salary

    B. N. Kreiswirth, None

    Findings in the abstracts are embargoed until 12:01 a.m. CDT, Wednesday Oct. 26th with the exception of research findings presented at the IDWeek press conferences.