[Characteristic of fluoroquinolone resistant clinical isolates of K. pneumoniae, P. mirabilis and E. coli producing ESBL and AmpC beta-lactamases]

Magdalena Rzeczkowska, Katarzyna Piekarska, Rafał Gierczyński
Medycyna Doświadczalna i Mikrobiologia 2012, 64 (4): 285-95

INTRODUCTION: Extended-spectrum beta-lactamases (ESBLs) are the predominant mechanism for acquired antibiotic resistance in Enterobacteriaceae. During the past few years, increasing occurrence of plasmid-mediated AmpC beta-lactamases (pAmpCs) particularly in K. pneumonia, P. mirabilis and E. coli was reported. Therefore, the aim of our study was to analyse of the diversity of plasmid-mediated beta-lactamases such as pAmpCs and ESBLs among clinical K. pneumonia, P. mirabilis and E. coli strains in Poland.

METHODS: A total of 19 clinical Enterobacteriaceae strains (E. coli, n = 9; K. pneumoniae, n = 7; P. mirabilis, n = 3) resistant to third-generation cephalosporin were selected from collection of fluoroquinolone resistant isolates recovered during a 6-months period in regular hospital in Warsaw, Poland. ESBLs and AmpCs were detected by using phenotypic methods: double-disc tests (DDSTs), MAST ID D68C test, sensitivity to cefoxitin, disk potentiation test (DPT) and Tris-EDTA test. Polymerase chain reaction (PCR) amplification of the bla(AmpC), bla(CTM-M), bla(TEM), and bla(SHV), genes. PCR-products for these genes were sequenced. To determine the possible clonality of the tested isolates PFGE with the XbaI was performed.

RESULTS: Nine of 19 fluoroquinolone-resistant strains tested produced extended-spectrum beta-lactamases of TEM, SHV and CTX-M families. These ESBLs were most commonly detected in E. coli. AmpC beta-lactamases were produced by 6 tested strains, including 3 isolates of P. mirabilis. The AmpC found in our study belonged to CMY and DHA families, Furthermore, 4 isolates of K. pneumoniae were found to co-produce both ESBL and AmpC beta-lactamases. XbaI-PFGE profiles pointed significant differences of tested strains.

CONCLUSION: Horizontal transfer of genes encoding for acquired beta-lactamases such ESBL and AmpC seem to play primary role in dissemination of these resistance traits among fluoroquinolone-resistant clinical strains of Enterobacteriaceae in Poland.

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