Molecular epidemiology of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a neonatal intensive care unit.
OBJECTIVE
To investigate the molecular epidemiology of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae in the neonatal intensive care unit of a university hospital in Italy.


METHODS
Antibiotic susceptibility was evaluated by disc diffusion and Etest. ESBLs were identified by isoelectric focusing, PCR and DNA sequencing analysis. Genotyping was performed by PFGE analysis. Conjugation was performed by broth mating.


RESULTS
Molecular typing of K. pneumoniae isolates identified three distinct PFGE patterns. Isolates of PFGE profile A were isolated during an epidemic in 1996, while isolates of PFGE profiles B and C were sequentially isolated from September 2002 to December 2004, when 233 colonizations and 19 infections by K. pneumoniae occurred. All K. pneumoniae strains of different PFGE types were identified as ESBL producers. DNA sequencing of amplified beta-lactamase genes identified a novel bla(TEM) ESBL (bla(TEM-136)) along with bla(SHV-1) in chromosomal and plasmid DNA from K. pneumoniae of PFGE type A, respectively, and bla(TEM-1) and bla(SHV-12) in plasmid DNA from K. pneumoniae of PFGE types B and C. Conjugation experiments demonstrated that resistance to third-generation cephalosporins, along with an approximately 80 kb plasmid containing bla(SHV-12) and bla(TEM-1), was transferred from K. pneumoniae epidemic strains of PFGE types B and C to a susceptible Escherichia coli host at a frequency of 4 x 10(-6) and 1 x 10(-6) cfu/recipient cell, respectively.


CONCLUSIONS
The selection of ESBL-producing clones and the transfer of the bla(SHV-12) ESBL gene between different clones were responsible for the spread of K. pneumoniae in the neonatal intensive care unit.
Dipartimento di Scienze Mediche Preventive, Sezione di Igiene, Università di Napoli Federico II, Napoli, Italy.
Maria
M
Bagattini
Valeria
V
Crivaro
Anna
A
Di Popolo
Fabrizio
F
Gentile
Alda
A
Scarcella
Maria
M
Triassi
Paolo
P
Villari
Raffaele
R
Zarrilli
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial; D006785:Hospitals, University; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D007525:Isoelectric Focusing; D007558:Italy; D007710:Klebsiella Infections / Q000453:epidemiology / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001618:beta-Lactamases