Contribution of enhanced efflux to reduced susceptibility of Salmonella enterica serovar Choleraesuis to fluoroquinolone and other antimicrobials.
We examined antimicrobial susceptibility and efflux systems in laboratory-derived mutants of Salmonella enterica serovar Choleraesuis selected by culture on fluoroquinolone-containing plates. The mutants exhibited decreased susceptibilities to quinolones and several other antimicrobials. Mutations in the gyrA gene were not always found in the mutants. Accumulation assays revealed that intracellular enrofloxacin concentrations were significantly lower in the mutants compared with parent isolates. Increased expression of acrB mRNA can explain the decreased susceptibilities to several antimicrobials but not in the case of carbonyl cyanide m-chlorophenylhydrazone (CCCP). Decreased susceptibility to CCCP may result from the increased expression of emrA mRNA. These results suggest that the enhancement of multiple efflux pumps is responsible for decreased susceptibilities to several antimicrobials in the laboratory-derived mutants.
Ministry of Agriculture, Forestry and Fisheries, Tokyo, Japan. usuima@nva.maff.go.jp
Masaru
M
Usui
Mariko
M
Uchiyama
Kotaro
K
Baba
Hidetaka
H
Nagai
Yoshimi
Y
Yamamoto
Tetsuo
T
Asai
D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology* / Q000627:therapeutic use; D027081:DNA Gyrase / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D024841:Fluoroquinolones / Q000494:pharmacology* / Q000627:therapeutic use; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D009154:Mutation; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012481:Salmonella Infections, Animal / Q000188:drug therapy / Q000201:enzymology / Q000382:microbiology*; D019779:Salmonella enterica / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013552:Swine; D013553:Swine Diseases / Q000188:drug therapy / Q000382:microbiology*
D000890:Anti-Infective Agents; D004269:DNA, Bacterial; D024841:Fluoroquinolones; D027081:DNA Gyrase