Fluoroquinolone resistance and gyrA and parC mutations of Escherichia coli isolated from chicken.

Escherichia coli is a common inhabitant of the intestinal tracts of animals and humans. The intestines of animals also represent an ideal environment for the selection and transfer of antimicrobial resistance genes. The aim of this study was to investigate the resistance of E. coli isolated from chicken fecal samples to fluoroquinolones and to analyze the characterization of mutations in its gyrA and parC gene related resistance. One hundred and twenty-eight E. coil isolates showed a high resistance to ciprofloxacin (CIP; 60.2%), enrofloxacin (ENO; 73.4%) and norfloxacin (NOR; 60.2%). Missense mutation in gyrA was only found in the amino acid codons of Ser-83 or Asp-87. A high percentage of isolates (60.2%) showed mutations at both amino acid codons. Missense mutation in parC was found in the amino acid codon of Ser-80 or Glu-84, and seven isolates showed mutations at both amino acid codons. Isolates with a single mutation in gyrA showed minimal inhibitory concentrations (MIC) for CIP (

Biochemical characteristics and antimicrobials susceptibility of Salmonella gallinarum isolated in Korea.

Fowl typhoid (FT) reported since 1992 in Korea is a septicemic disease of domestic birds caused by Salmonella gallinarum (S. gallinarum). The purpose of this study was to investigate the biochemical characteristics and antimicrobials susceptibility of field isolates of S. gallinarum isolated by year in Korea. A total of 258 isolates of S. gallinarum from 1995 to 2001 showed the same pattern in the majority of biochemical test such as IMViC (indole, methyl red, Voges-Proskauer and citrate utilization), carbohydrate fermentation and amino acid decarboxylation, and these results were almost in accordance with the traditional biochemical characteristics of S. gallinarum strain. When the antimicrobial susceptibility test against 258 isolates of S. gallinarum was performed by the disk diffusion method using 12 antimicrobial agents, all isolates from 1995 appeared to be susceptible to all of the antimicrobial agents tested except for tetracycline and oxytetracycline, whereas the vast majority of isolates from 2001 showed the reduced susceptibility to ampicillin (13.0%), gentamicin (43.4%), kanamycin (69.6%), enrofloxacin (6.5%), ciprofloxacin (10.9%), norfloxacin (52.5%) and ofloxacin (82. 6%). The prevalence of the prevalence of completely resistant isolates resistant isolates to one or more drugs rapidly increased from 0% in 1995 to 93.5% in 2001. The minimal concentrations range of the majority of antimicrobial agents to inhibit 50% (MIC50s) against S. gallinarum isolates increased from 0.06 approximately 8 microg/ml in 1997 to 2 approximately 256 microg/ml in 2001. Especially, MIC50s for gentamicin and fluoroquinolones of isolates from 2001 increased over 10-fold than those of isolates from 1997. Therefore, our results indicate that sorbitol fermentation and arginine decarboxylation showed the diversity by isolates and the vast majority of isolates from 2001 showed the reduced susceptibility to antimicrobials tested.