Plasmid-mediated resistance to ciprofloxacin and cefotaxime in clinical isolates of Salmonella enterica serotype Enteritidis in Hong Kong.
OBJECTIVE
To characterize the genetic determinants involved in the reduced susceptibility to ciprofloxacin and cefotaxime in Salmonella enterica serotype Enteritidis clinical isolates obtained from four patients in summer 2003 in Hong Kong.


METHODS
Three Salmonella Enteritidis isolates from blood culture and one from stool were collected due to their increased resistance to ciprofloxacin and cefotaxime. PFGE analysis was used to investigate their genetic relatedness. Conjugation experiments were employed to show if the genetic determinants involved were plasmid-mediated. MICs of various antimicrobials were determined by VITEK 2 and Etest. Based on the susceptibility and conjugation experiment results, previously described PCR methods were employed to detect sequences homologous to qnr and bla(CTX-M) suspected to be involved in the reduced susceptibility to ciprofloxacin and cefotaxime, respectively.


RESULTS
PFGE analysis showed that the four Salmonella isolates were clonally unrelated. The presence of a qnr-like gene and the CTX-M allele bla(CTX-M-14) on four different transferable plasmids harboured by the four isolates was confirmed.


CONCLUSIONS
This is the first report of transferable fluoroquinolone resistance due to a new qnr allele, which appeared to be linked to bla(CTX-M-14), in isolates of Salmonella Enteritidis in Hong Kong.
Cheung
Terence Kin Man
TK
Microbiology Division, Public Health Laboratory Services Branch, Centre for Health Protection, Department of Health, Hong Kong SAR, China.
Chu
Yiu Wai
YW
Chu
Man Yu
MY
Ma
Choi Ha
CH
Yung
Raymond Wai Hung
RW
Kam
Kai Man
KM
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002439:Cefotaxime / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D003227:Conjugation, Genetic; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D024841:Fluoroquinolones / Q000494:pharmacology; D006723:Hong Kong; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D012477:Salmonella enteritidis / Q000187:drug effects* / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D024841:Fluoroquinolones; C485385:Qnr protein, Klebsiella pneumoniae; D002939:Ciprofloxacin; C456080:beta-lactamase CTX-M-14; D001618:beta-Lactamases; D002439:Cefotaxime