[Mutations in gyrA and gyrB genes among strains of Gram-negative bacilli isolated from Chilean hospitals and their relation with resistance to fluoroquinolones].
BACKGROUND
A progressive frequency of resistance to fluoroquinolones is observed among Gram-negative bacilli.


OBJECTIVE
To investigate the mechanism of resistance to fluoroquinolones mediated by mutations affecting gyrA and gyrB genes in strains of Gram negative bacüli isolated from CMean hospitals.


METHODS
Minimal inhibitory concentration of fluoroquinolones was determined in 91 randomly selected nalidixic acid-resistant strains of Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa, isolated from hospitals of 12 Chilean cities. Quinolone resistance determining region (QRDR) was amplified by PCR and mutations were determined by restriction fragment length polymorphism (RFLP) and DNA sequencing.


RESULTS
Strains with mutation in codon 83 of gyrA showed decreased susceptibility to ciprofloxacin with MICs ranging from 0.25 to 1024 fig/ml. The sequencing of PCR products for gyrA indicated amino acid changes in the QRDR region. One strain ofE. coli presented a double mutation, in codon 83 Ser to Leu as well as in codon 87 Asp to Asn. In strains ofK. pneumoniae, however, the change of codon 83 was Ser to Tyr, in A. baumannii was Ser to Leu and in P. aeruginosa was Thr to He. No strains with mutations affecting gyrB were found.


CONCLUSIONS
Mutations in codon 83 of gyrA is a frequent genetic event involved in the mechanism leading to decreased susceptibility to fluoroquinolone in strains of Gram-negative bacilli.
De la Fuente C
Mery
M
Laboratorio de Antibióticos, Departamento de Microbiología, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile.
Dauros S
Priscila
P
Bello T
Helia
H
Domínguez Y
Mariana
M
Mella M
Sergio
S
Sepúlveda A
Marcela
M
Zemelman Z
Raúl
R
González R
Gerardo
G
D040981:Acinetobacter baumannii / Q000187:drug effects / Q000235:genetics; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D002677:Chile; D003062:Codon / Q000235:genetics; D027081:DNA Gyrase / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D024841:Fluoroquinolones / Q000494:pharmacology*; D005787:Gene Frequency; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000235:genetics; D006761:Hospitals; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003062:Codon; D024841:Fluoroquinolones; D027081:DNA Gyrase