Characterization of the extended-spectrum β-lactamases and determination of the virulence factors of uropathogenic Escherichia coli strains isolated from children.
OBJECTIVE
The aim of the study was to characterize ESBL-producing uropathogenic Escherichia coli (UPEC) strains isolated in children. That included the investigation of virulence factors and the analysis of the types of β-lactamases at the molecular genetic level.


METHODS
During the 2-year study period, 77 ESBL-producing E. coli strains were recovered from urine samples of febrile children with significant bacteriuria hospitalized at one Croatian hospital. Susceptibility of isolates to bactericidal serum activity was tested by Shiller and Hatch method, while adhesin expression was determined by agglutination methods. Characterization of ESBLs was performed by PCR with specific primers for ESBLs and by sequencing of bla                            (ESBL) genes. Genotyping of the E. coli isolates was performed by pulsed-field gel electrophoresis (PFGE).


RESULTS
Twenty-seven (35.1 %) and 50 (64.9 %) ESBL-producing UPEC strains were isolated in neonates and infants, respectively. Of 70 strains investigated for the presence of virulence factors, adhesins were detected in 48.6 % strains (8.6 % in the neonate and 40 % in the infants group) giving a statistically significant difference in adhesin expression between the two groups (p < 0.01). Hemolysin was produced by 84.3 %, whereas 70 % of strains were serum-resistant. The bla                            (TEM) gene was detected in 22 (28 %) and bla                            (SHV) gene in 57 strains (74 %), whereas bla                            (CTX-M) gene was detected in only two isolates (2.5%). In ten isolates, bla                            (TEM) and bla                            (SHV) were simultaneously detected. Sequencing of bla                            (SHV) genes revealed that SHV-5 β-lactamase was by far the most prevalent and was found in 51 strains (66 %). The strains were clonally related as demonstrated by PFGE and assigned into ten clusters.


CONCLUSIONS
Infection control measures should be employed and the consumption of expanded-spectrum cephalosporins in the hospital should be restricted.
Department of Microbiology, School of Medicine, University of Zagreb, Salata 3, 10000, Zagreb, Croatia. branka.bedenic@zg.t-com.hr
Branka
B
Bedenić
Jasmina
J
Vraneš
Sabine
S
Hofmann-Thiel
Marija
M
Tonkić
Anita
A
Novak
Viljemka
V
Bučević-Popovic
Harald
H
Hoffmann
D002648:Child; D002675:Child, Preschool; D017523:Croatia / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D056689:Uropathogenic Escherichia coli / Q000145:classification / Q000201:enzymology* / Q000302:isolation & purification*; D001618:beta-Lactamases / Q000097:blood* / Q000235:genetics*
D001618:beta-Lactamases