Molecular characterization of integrons in non-typhoid Salmonella serovars isolated in Japan: description of an unusual class 2 integron.
OBJECTIVE
To characterize class 1 and class 2 integrons among non-typhoid Salmonella enterica serovars in Japan, and also to monitor the spread of the multidrug-resistant S. enterica serovar Typhimurium DT104.


METHODS
A total of 105 Salmonella isolates were included in this study. The broth microdilution method was used to determine the MIC values of a range of antibiotics for these isolates. PCR and DNA sequencing were used for screening and characterization of class 1 and class 2 integrons.


RESULTS
PCR sequencing analysis revealed the presence of seven profiles of class 1 integrons in addition to a new type of class 2 integron. The identified gene cassettes within class 1 integrons were as follows; aadA1, aadA2 and aadA5, which confer resistance to streptomycin and spectinomycin; aadB, which confers resistance to gentamicin, kanamycin and tobramycin; dfrA1 and dfrA17, which confer resistance to trimethoprim; bla(PSE-1), which confers resistance to ampicillin; catB3, which confers resistance to chloramphenicol; and sat1, which confers resistance to streptothricin. Two strains of the multidrug-resistant S. Typhimurium DT104 were characterized in this study. DNA sequencing of class 2 integrons identified one with an unusual array of gene cassettes, sat, sat1 and aadA1.


CONCLUSIONS
In this study, we characterized the antibiotic resistance gene cassettes within class 1 integrons in different isolates of non-typhoid Salmonella serovars, and we also identified a new type of class 2 integron.
Ahmed
Ashraf M
AM
Laboratory of Food Microbiology and Hygiene, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8528, Japan.
Nakano
Hiroyuki
H
Shimamoto
Tadashi
T
D001483:Base Sequence; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D032023:Integrons; D008969:Molecular Sequence Data; D012475:Salmonella / Q000187:drug effects / Q000235:genetics*