JAC Advance Access originally published online on June 13, 2009
Journal of Antimicrobial Chemotherapy 2009 64(3):524-528; doi:10.1093/jac/dkp211
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Original research |
Emergence of CTX-M-15-producing Klebsiella pneumoniae of multilocus sequence types 1, 11, 14, 17, 20, 35 and 36 as pathogens and colonizers in newborns and adults
1 Servicio de Bacteriología, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain 2 Hospital Costa del Sol, Málaga, Spain 3 Hospital Universitario Carlos Haya, Málaga, Spain 4 Hospital Universitario La Paz, Madrid, Spain 5 Hospital Puerta del Mar, Cádiz, Spain 6 Consejo Superior de Investigaciones Científicas, Madrid, Spain
Received 18 March 2009; returned 21 April 2009; revised 22 May 2009; accepted 24 May 2009
* Corresponding author. Centro Nacional de Microbiología, Instituto de Salud Carlos III, Carretera Pozuelo a Majadahonda, 28220 Majadahonda, Madrid, Spain. Tel: +34-918-22-3650; Fax: +34-915-09-7966; E-mail: jcampos{at}isciii.es
Objectives: To characterize the population structure and resistance mechanisms of Klebsiella pneumoniae isolates that are highly resistant to third-generation cephalosporins, collected from five Spanish hospitals.
Methods: A total of 162 K. pneumoniae isolates from five hospitals located in three geographical areas of Spain were characterized. The number of isolates from each hospital ranged from 3 to 82. The genetic relationship between isolates was established by PFGE and multilocus sequence typing (MLST). blaESBL types and other antibiotic resistance genes were analysed by PCR and sequencing. Plasmids were classified according to their incompatibility group by a PCR-based replicon-typing scheme.
Results: All 162 isolates carried the blaCTX-15 gene. Fifty-eight isolates (35.8%) caused clinical infections and 104 (64.2%) were colonizers. Sixty-nine (42.6%) isolates were collected from newborns and 93 (57.4%) from adults. Using PGFE, the 162 isolates were grouped into seven clusters that were further identified as members of the MLST types 1, 11, 14, 17, 20, 35 and 36. Two hospitals each had two different clones and the remaining three hospitals had a single CTX-M-15-producing K. pneumoniae clone. All clones carried different antibiotic resistance genes, including blaOXA-1, aac(3)-IIa, aac(6')-Ib-cr, qnrS1 and qnrB. In four of the seven (57.1%) clones the blaCTX-M-15 gene was transferred by conjugation; in all cases plasmids of the incompatibility group IncF were identified by PCR.
Conclusions: This study shows that multiresistant K. pneumoniae producing CTX-M-15 of MLST types 1, 11, 14, 17, 20, 35 and 36 are spreading as pathogens and colonizers among newborns and adult patients in Spain.
Keywords: extended-spectrum β-lactamases , multiresistance , population structure