Characterization of clinical Escherichia coli isolates from China containing transferable quinolone resistance determinants.
BACKGROUND
The categories of recognized transferable quinolone resistance determinants have been increasing sharply. The rapid horizontal transfer of these quinolone resistance genes has caused concern since they bring new dissemination possibilities for quinolone resistance.


METHODS
In total, 579 clinical Escherichia coli isolates were subjected to antimicrobial susceptibility testing, screening for qnr alleles, qepA and aac-(6')-Ib-cr by PCR amplification and DNA sequence analysis. Isolates containing transferable quinolone resistance determinants were further characterized by mutation analysis in the quinolone resistance determining regions (QRDRs) of GyrA and ParC, phylogenetic typing and PFGE to determine their genetic relatedness.


RESULTS
After PCR screening and sequence analysis, transferable quinolone resistance determinants were identified in 74 of 579 E. coli isolates (12.8%). The antimicrobial resistance profiles and phylogenetic groups differed between isolates containing different categories of transferable quinolone resistance determinant. Most of the isolates containing qepA alone were highly resistant to ciprofloxacin (MIC >or= 512 mg/L) and belonged to phylogenetic group D (22/25), while most of the isolates containing aac-(6')-Ib-cr alone belonged to phylogenetic group A (17/35) or D (16/35). Of 74 E. coli isolates containing transferable quinolone resistance determinants, 69 PFGE patterns and 19 clusters were identified.


CONCLUSIONS
The great genetic variation of E. coli hosts containing transferable quinolone resistance determinants demonstrated the high transmission capacity of these mechanisms. It is urgent to characterize and block their transmission routes in order that the utility of quinolones is preserved.
Yang
Jiyong
J
Department of Microbiology, General Hospital of PLA, Beijing, China.
Luo
Yanping
Y
Li
Jingyun
J
Ma
Yue
Y
Hu
Changqin
C
Jin
Shaohong
S
Ye
Liyan
L
Cui
Shenghui
S
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015373:Bacterial Typing Techniques; D002681:China; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004252:DNA Mutational Analysis; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D022761:Gene Transfer, Horizontal; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D015363:Quinolones / Q000494:pharmacology*; D017422:Sequence Analysis, DNA
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D015363:Quinolones