Emergence of CTX-M group 1 extended-spectrum beta-lactamase-producing Klebsiella pneumoniae strains in the community.
OBJECTIVE
Molecular characterization of ESBL-producing K. pneumoniae strains isolated from urine of outpatients in Zagreb region during the last five years.


METHODS
During the five-year study period a total of 2, 651 K. pneumoniae strains were isolated from urine of nonhospitalized patients with significant bacteriuria. ESBL production was detected by double-disk diffusion technique and by > or = 3-dilution reduction in the minimal inhibitory concentration of ceftazidime in the presence of clavulanate. A total of 441 ESBL-producing K. pneumoniae strains (15.5%) were collected and 17 strains were further characterised. Double-disk synergy test was used to detect ESBLs. Minimum inhibitory concentrations (MICs) were determined by broth microdilution method according to CLSI. The transferability of cefotaxime resistance was tested by conjugation (broth mating method). PCR was used to detect alleles encoding ESBL enzymes. The genotypes of the strains were compared by pulsed-field gel electrophoresis (PFGE) of Xba I-digested genomic DNA.


RESULTS
A significant difference in frequencies of ESBL isolates was observed. In the first year of study only 4.9% of isolated strains were ESBL producers, while in the second year 17.% ESBL-positive strains were detected (p < 0.01), and the frequency remained stabile within following years. All strains yielded an amplicon with primers specific for SHV beta-lactamases and CTX-M beta-lactamases. Based on sequencing of bla(CTX-M) genes enzymes of nine strains were identified as CTX-M 15 beta -lactamase and three as CTX-M-14. Isolates were not clonally related.


CONCLUSIONS
The study demonstrated community-associated emergence of CTX-M 1 beta-lactamase-producing K. pneumoniae strains.
Bedenić
Branka
B
Medicinski fakultet Sveucilista u Zagrebu, Hrvatska. branka.bedenic@zg.t-com.hr
Vranes
Jasmina
J
Bosnjak
Zrinka
Z
Marijan
Tatjana
T
Mlinarić-Dzepina
Ana
A
Kukovec
Tamara
T
Knezević
Jasna
J
Anusić
Maja
M
Beader
Natasa
N
Barl
Petra
P
Leskovar
Vladimira
V
Kalenić
Smilja
S
D017714:Community-Acquired Infections / Q000382:microbiology; D006801:Humans; D007710:Klebsiella Infections / Q000188:drug therapy / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D014552:Urinary Tract Infections / Q000188:drug therapy / Q000382:microbiology*; D001618:beta-Lactamases / Q000378:metabolism*
C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases