%0 Journal Article
%T Prevalence of aac(6')-Ib-cr plasmid-mediated and chromosome-encoded fluoroquinolone resistance in Enterobacteriaceae in Italy
%A Ilaria Frasson
%A Antonietta Cavallaro
%A Cristina Bergo
%A Sara N Richter
%A Giorgio Pal¨´
%J Gut Pathogens
%D 2011
%I BioMed Central
%R 10.1186/1757-4749-3-12
%X The aminoglycoside acetyltransferase Aac(6')-Ib-cr variant, an enzyme usually encoded by a plasmid-borne gene, extends its drug targets to include fluoroquinolones (FQs) in addition to aminoglycosides. It is characterized by amino acid changes at codon 102 (Trp¡úArg) and codon 179 (Asp¡úTyr). The Aac(6')-Ib-cr protein is able to specifically acetylate hydrophilic FQs presenting a free piperazinyl amine (i.e. ciprofloxacin and norfloxacin) [1].The aac(6')-Ib-cr gene has spread rapidly among Enterobacteriaceae, and although only conferring a low-level resistance, it may create an environment facilitating the selection of more highly resistant determinants, especially those harbouring topoisomerase mutations. This fact is particularly worrisome at the nosocomial level, where aac(6')-Ib-cr containing strains should be promptly detected and treated with non-hydrophilic FQs, such as levofloxacin or ofloxacin, or other classes of antibiotics to prevent high-level resistance onset and spread.In this work we determined the prevalence of the aac(6')-Ib-cr gene variant among clinical isolates of Enterobacteriacea collected at the teaching Hospital of Padua, Italy. In the time period of March-May 2008, 197 non-duplicate clinical isolates were collected. These displayed the whole range of MIC of ciprofloxacin; in particular, 104 samples were susceptible (MIC ¡Ü 1), 35 intermediate (1 < MIC < 4), and 58 resistant (MIC ¡Ý 4) to ciprofloxacin. Exact MIC values were measured by means of E-test strips (AB Biodisk, Solna, Sweden). Bacterial isolates were: 145 E. coli, 38 K. pneumoniae, 5 Proteus mirabilis, 5 Enterobacter aerogenes, 2 Enterobacter cloacae and 2 Citrobacter freundii. Sample identity and results are reported in Table 1.The presence of the aac(6')-Ib or aac(6')-Ib-cr genes was assessed by PCR amplification and subsequent sequencing with primers: aacF 5'-ATGACTGAGCATGACCTTG-3'; aacR 5'-AACCATGTACACGGCTGG-3'; aacSEQ 5'-CGTCACTCCATACATTGCAA-3' [2].Twenty-five samples out of 197
%K aac(6')-Ib-cr
%K fluoroquinolones
%K plasmid-mediated resistance
%K Gram-negative
%U http://www.gutpathogens.com/content/3/1/12