Clonal Spread of Colistin-Resistant Klebsiella pneumoniae During Extensive Use of Colistin for Multiresistant Bacteria Treatment

ARDUINO SONIA; QUIROGA MARÍA PAULA; RELLOSO SILVIA; GARCIA D.; RAMÍREZ MARÍA SOLEDAD; NICOLA FEDERICO; CENTRÓN DANIELA; BONVEHI PABLO; SMAYEVSKY JORGELINA

Philadelphia, Pennsylvania, Estados Unidos.

Encuentro; 47th Annual Meeting of the Infectious Diseases Society of America (IDSA); 2009

Infectious Diseases Society of America (IDSA)

Background. Infections due to multidrug-resistant (MDR) gram-negative pathogens have increased in our hospital in the last years. Due to the high number of Acinetobacter baumannii MDR isolates, the patients at the intensive care units (ICUs) are often treated with the old antimicrobial colistin. We investigated the emergence of colistin-resistant K. pneumoniae (CRKp) in the ICUs of a teaching hospital in Buenos Aires, Argentina.Methods. All CRKp isolated in clinical samples from ICU patients during the period 2008-9 were recorded along with patients’ data. Colistin susceptibility was tested by E test and microdilution method; resistance was defined as MIC >4 mg/l. To establish the clonal relationship between isolates, repetitive extragenic palindromic (REP) PCR was done to all CRKp and 4 colistin-sensitive K. pneumoniae obtained in the same period.Results. Twelve CRKp were isolated from 11 patients over a 16 month period. Susceptibility testing revealed that the CRKp were resistant to multiple antimicrobials. The isolates were implicated as pathogens in bacteremias (2), ventilator-associated pneumonia (1), soft tissue infections (2) and urinary infections (7). Six patients had received colistin for a long period (range14-51 days) while 4 patients never received treatment with colistin. REP PCR showed that 8 out of 12 isolates belonged to the same clone indicating horizontal transmission between patients, including those who never received colistin.Conclusions. Selective pressure due to extensive colistin use may lead to the emergence of CRKp isolates. Once selected, these isolates can be easily transmitted from patient to patient in critical areas independently of the antimicrobial treatment of each patient. It is very important not only to establish a prudent use of colistin to avoid colistin-resistant isolates selection in the hospital but also the continuous surveillance of these isolates in order to prevent the emergence of clonal outbreaks.