Objectives: To define the genetic characteristics and resistance mechanisms of clinical isolates of Salmonella enterica serovar Typhi (S. Typhi) and S. enterica serovar Paratyphi A (S. Paratyphi A) exhibiting high-level fluoroquinolones resistance. Methods: Three S. Typhi and two S. Paratyphi A ciprofloxacin-resistant isolates (MICs > 4 mg/L) were compared with isolates with reduced susceptibility to ciprofloxacin (MICs 0.125–1 mg/L) by PFGE, plasmid analysis, presence of integrons and nucleotide changes in topoisomerase genes. Results: In S. Typhi and Paratyphi A, a single gyrA mutation (Ser-83!Phe or Ser-83!Tyr) was associated with reduced susceptibility to ciprofloxacin (MICs 0.125–1 mg/L); an additional mutation in parC (Ser-80!Ile, Ser-80!Arg, Asp-69!Glu or Gly-78!Asp) was accompanied by an increase in ciprofloxacin MIC ( 0.5 mg/L). Three mutations conferred ciprofloxacin resistance: two in gyrA (Ser-83!Phe and Asp-87!Asn or Asp-87!Gly) and one in parC. This is the first report of parC mutations in S. Typhi. Ciprofloxacin-resistant S. Typhi and S. Paratyphi A differed in their MICs and mutations in gyrA and parC. Moreover S. Typhi harboured a 50 kb transferable plasmid carrying a class 1 integron (dfrA15/aadA1) that confers resistance to co-trimoxazole and tetracycline but not to ciprofloxacin. PFGE revealed undistinguishable XbaI fragment patterns in ciprofloxacin-resistant S. Typhi as well as in S. Paratyphi A isolates and showed that ciprofloxacin-resistant S. Typhi have emerged from a clonally related isolate with reduced susceptibility to ciprofloxacin after sequential acquisition of a second mutation in gyrA.

Molecular characterization of ciprofloxacin-resistant Salmonella enterica serovar Typhi and Paratyphi A causing enteric fever in India / Gaind, R; Paglietti, B; Murgia, M; Dawar, R; Uzzau, Sergio; Cappuccinelli, Pietro Antonio; Deb, M; Aggarwal, P; Rubino, Salvatore. - In: JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY. - ISSN 0305-7453. - 58:6(2006), pp. 1139-1144. [10.1093/jac/dkl391]

Molecular characterization of ciprofloxacin-resistant Salmonella enterica serovar Typhi and Paratyphi A causing enteric fever in India

Paglietti B;UZZAU, Sergio;CAPPUCCINELLI, Pietro Antonio;RUBINO, Salvatore
2006-01-01

Abstract

Objectives: To define the genetic characteristics and resistance mechanisms of clinical isolates of Salmonella enterica serovar Typhi (S. Typhi) and S. enterica serovar Paratyphi A (S. Paratyphi A) exhibiting high-level fluoroquinolones resistance. Methods: Three S. Typhi and two S. Paratyphi A ciprofloxacin-resistant isolates (MICs > 4 mg/L) were compared with isolates with reduced susceptibility to ciprofloxacin (MICs 0.125–1 mg/L) by PFGE, plasmid analysis, presence of integrons and nucleotide changes in topoisomerase genes. Results: In S. Typhi and Paratyphi A, a single gyrA mutation (Ser-83!Phe or Ser-83!Tyr) was associated with reduced susceptibility to ciprofloxacin (MICs 0.125–1 mg/L); an additional mutation in parC (Ser-80!Ile, Ser-80!Arg, Asp-69!Glu or Gly-78!Asp) was accompanied by an increase in ciprofloxacin MIC ( 0.5 mg/L). Three mutations conferred ciprofloxacin resistance: two in gyrA (Ser-83!Phe and Asp-87!Asn or Asp-87!Gly) and one in parC. This is the first report of parC mutations in S. Typhi. Ciprofloxacin-resistant S. Typhi and S. Paratyphi A differed in their MICs and mutations in gyrA and parC. Moreover S. Typhi harboured a 50 kb transferable plasmid carrying a class 1 integron (dfrA15/aadA1) that confers resistance to co-trimoxazole and tetracycline but not to ciprofloxacin. PFGE revealed undistinguishable XbaI fragment patterns in ciprofloxacin-resistant S. Typhi as well as in S. Paratyphi A isolates and showed that ciprofloxacin-resistant S. Typhi have emerged from a clonally related isolate with reduced susceptibility to ciprofloxacin after sequential acquisition of a second mutation in gyrA.
2006
Molecular characterization of ciprofloxacin-resistant Salmonella enterica serovar Typhi and Paratyphi A causing enteric fever in India / Gaind, R; Paglietti, B; Murgia, M; Dawar, R; Uzzau, Sergio; Cappuccinelli, Pietro Antonio; Deb, M; Aggarwal, P; Rubino, Salvatore. - In: JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY. - ISSN 0305-7453. - 58:6(2006), pp. 1139-1144. [10.1093/jac/dkl391]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11388/45754
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