Analysis of gene cassettes of streptomycin-spectinomycin resistance of Hungarian Salmonella enterica serotype Typhimurium strains

Abstract

By PCR using the ant(3")-Ia primer pair the aadA gene was detected in 34 streptomycin-and spectinomycin-resistant Salmonella enterica serotype Typhimurium strains. Out of them 12 belonged to DT104 and 22 to non-DT104 phage type. Using different primer combinations it was demonstrated that this gene was integron-associated in all cases: in the DT104 strains it was generally contained by a 1 kb integron while in the majority of the non-DT104 strains by a 2.05 kb (less often by a 1.9 or 1 kb) integron. In the case of integrons carrying multiple cassettes the cassette containing the aadA gene was located closer to the 3' end of the integron. The aadA genes of DT104 and non-DT104 strains were different: in the former group the aadA2 gene, while in the latter group (constituted by strains of five different phages types as well as unclassifiable and untypable strains) the aadA1 gene could be identified. The RH50/RH51 primer pair described by Collis and Hall (1992) proved to be suitable for rapid discrimination between the aadA1 and aadA2 genes on the basis that the RH51 primer bound exclusively to the aadA2 gene.Key words: Salmonella Typhimurium, streptomycin/spectinomycin resistance, aadA gene cassettes, sequencing Salmonella enterica serotype Typhimurium (S. Typhimurium) phage type DT104 has great epidemiological importance in Europe and in the United States (Threlfall et al., 1994;Low et al., 1997;Besser et al., 1997) and is usually characterised by the high prevalence of multidrug resistance to ampicillin (Amp), chloramphenicol (Chl), streptomycin (Sm), spectinomycin (Spc), sulphonamides (Su) and tetracycline (T) (Threlfall et al., 1996;Glynn et al., 1998;Ridley and Threlfall, 1998 Acta Veterinaria Hungarica 51, 2003 it had become the dominant phage type already by 1991 (Szmollény et al., 2000;Pászti et al., 2001). Within the DT104 phage type, only in Felix and Callow's (1951) phage type 2 group did the incidence of multiresistant strains substantially exceed the average level, while in the phage type 2c group it did not (Pászti et al., 2001).The aadA gene responsible for Sm/Spc resistance is the commonest integron-associated gene among isolates of Enterobacteriaceae in Europe (MartinezFreijo et al., 1999). Its variants constitute a gene family the two most important members of which are aadA1 sequenced by Hollingshead and Vapnek (1985), Fling et al. (1985) and Sundström et al. (1988), and aadA2 sequenced by Tait et al. (1985) and Bito and Susani (1994). Further variants (aadA3-A8, aadAsc) have been described from E. coli, Pseudomonas aeruginosa and Salmonella choleraesuis isolates (Leung et al., 1992;Naas et al., 1999;Adrian et al., 2000;Mazel et al., 2000;White et al., 2000;Peters et al., 2001). The integron nature of the aadA gene and the plasmid-and/or transposon-associated location of the integrons may have played a role in the excessive horizontal spread of aadA.In both of the above two groups of the DT104 strains analysed in this study, Sm/Spc resistance was closely associated with the presence of a 1 k...

<p>Carbapenem-Resistant <em>Enterobacter hormaechei</em> ST1103 with IMP-26 Carbapenemase and ESBL Gene <em>bla</em>_SHV-178</p>

“…44 In recent years, the transfer of integrons harboring multiple drug-resistant gene cassettes or the joint transfer of two or more integrons into one isolate appears to be the basis for the rapid growth of MDR isolates. 45 Our conjugative plasmid pEHZJ1 possesses two class 1 integrons and an array of drug resistance genes, which may well pose a threat for the treatment of nosocomial infection. Previous reports showed that bla IMP-26 has high genetic similarity to bla IMP-4 , with only one position substitution at 145 (G-to-T change), 13 moreover, bla IMP-26 and bla IMP-4 were generally carried by a class 1 integron.…”

Salmonella Genomic Island 1 (SGI1) and genetic characteristics of animal and food isolates of Salmonella Typhimurium DT104 in Hungary

“…It was also described in other serovars (S. Agona and S. Newport), although with different resistance phenotypes (Boyd et al, 2002). DT104 S. Typhimurium strains were also found and characterised for their origin, for antibiotic resistance and for their integron content in Hungary (Szmollény et al, 2000;Pászti et al, 2001;Nógrády et al, 2003) but so far the occurrence of SGI1 has not been reported among Hungarian Salmonella strains. Therefore we identified and collected recent SGI1-positive Salmonella isolates and analysed their genetic relationships in relation to their origin.…”

Antibiotic resistance and class 1 integron patterns of non-typhoidal human Salmonella serotypes isolated in Hungary in 2002 and 2003

“…The appearance and spread of penta-resistant Salmonella Typhimurium definitive phage type 104 (DT 104) strains of human and animal origin in Hungary has been reported recently [6,7]. Preliminary data on the relationship of antibiotic resistance and integron carriage of S. Typhimurium strains have also been published on a collection of 105 strains isolated in 1998 [8,9]. However, there are no data at all on the antibiotic resistance and integron carriage of the other commonly isolated human Salmonella serotypes such as S. Enteritidis, S. Infantis, S. Hadar and S. Virchow from Hungary.…”