Abstract
We describe polyclonal spread of colistin-resistant Klebsiella pneumoniae in an acute general hospital in Italy. Between June and December 2011, 58 colistin-resistant K. pneumoniae isolates were recovered from 28 patients admitted to different wards, but mainly in the intensive care units. All isolates were tested for drug susceptibility and the presence of beta-lactamase (bla) genes. Clonality was investigated by repetitive extragenic palindromic (rep)-PCR and multilocus sequence typing (MLST). Fifty-two isolates had minimum inhibitory concentrations (MICs) for colistin of 6-128 mg/L, carried bla(KPC3) and were attributed to sequence type ST258. The remaining six isolates were susceptible to carbapenems, exhibited MICs for colistin of 3-32 mg/L, and belonged to two different types, ST15 and ST273. Rep-PCR included all isolates in three clusters, one containing all ST258 KPC-3-producing isolates and two containing ST15 and ST273 isolates.Cross-transmission containment measures and intensification of staff and environmental hygiene could not stop the outbreak. Selective pressure and horizontal transmission probably contributed to emergence and spread of three different strains of colistin-resistant K. pneumoniae in the hospital. Strict implementation of the above measures and a wider awareness of the antimicrobial resistance threat are crucial to preserve the last therapeutic options of the multidrug-resistant Gram-negative infections.
Highlights
Infections caused by Gram-negative pathogens resistant to carbapenems are emerging as a consequence of the intensive use of these compounds [1]
Selective pressure by the increased use of colistin and clonal expansion through horizontal transmission have generated clusters of cases infected with multiresistant K. pneumoniae strains that have been generally attributed to the international epidemic clone ST258 [4,7]
The index case was a patient staying in the I intensive care unit (ICU), from whom a colistin-resistant K. pneumoniae isolate was identified on 8 June 2011
Summary
Infections caused by Gram-negative pathogens resistant to carbapenems are emerging as a consequence of the intensive use of these compounds [1]. Polimyxins are considered as the last resort for treatment of infections with carbapenem-resistant Gram-negative bacteria. Resistance to these compounds has begun to emerge, infrequently [4,5,6,7,8]. Selective pressure by the increased use of colistin and clonal expansion through horizontal transmission have generated clusters of cases infected with multiresistant K. pneumoniae strains that have been generally attributed to the international epidemic clone ST258 [4,7]
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