Emergence and evolution of multiply antibiotic-resistant Salmonella enterica serovar Paratyphi B D-tartrate-utilizing strains containing SGI1.

The first Australian isolate of Salmonella enterica serovar Paratyphi B D-tartrate-utilizing (dT(+)) that is resistant to ampicillin, chloramphenicol, florfenicol, streptomycin, spectinomycin, sulfonamides, and tetracycline (ApCmFlSmSpSuTc) and contains SGI1 was isolated from a patient with gastroenteritis in early 1995. This is the earliest reported isolation globally. The incidence of infections caused by these SGI1-containing multiply antibiotic-resistant S.

Unusual class 1 integron-associated gene cassette configuration found in IncA/C plasmids from Salmonella enterica.

IncA/C plasmids carrying an unusual cassette configuration in a class 1 integron and five further shared resistance genes, aacC4, aphA1, hph, sul2, and tetA(D) were found in Salmonella enterica serovars Senftenberg and Ohio. A deletion formed using a short region of homology in the 5' conserved segment and the orfF cassette created an array with only part of orfF followed by the aadA2 cassette. The IncA/C plasmids were not recoverable by conjugation, but additional conjugative resistance plasmids were present in some strains.

SGI2, a relative of Salmonella genomic island SGI1 with an independent origin.

Multiply antibiotic-resistant Salmonella enterica serovar Emek strains isolated in Australia and the United Kingdom had similar features, suggesting that they all belong to a single clone. These strains all contain SGI2 (formerly SGI1-J), an independently formed relative of Salmonella genomic island SGI1. In SGI2, the complex class 1 integron which includes all of the resistance genes is not located between tnpR (S027) and S044 as in SGI1 and SGI1 variants.

SGI1-K, a variant of the SGI1 genomic island carrying a mercury resistance region, in Salmonella enterica serovar Kentucky.

A multiple-antibiotic-resistant Salmonella enterica serovar Kentucky strain was found to contain SGI1-K, a variant form of the Salmonella genomic island 1 (SGI1) with an In4-type class 1 integron that contains only one cassette array, aacCA5-aadA7, and an adjacent mercury resistance module. Part of the 3'-conserved segment (3'-CS) of the integron, together with the inverted short segment from the right-hand end of the integron transposition module normally found between the 3'-CS and IS6100 in In4 family integrons, has been removed by an IS6100-mediated deletion. IRt, the right-hand inverted repeat found at the outer end of the integron, abuts a mercury resistance region instead of the usual SGI1 backbone segment.

New integron-associated gene cassette encoding a trimethoprim-resistant DfrB-type dihydrofolate reductase.

A sixth gene cassette containing a dfrB-type gene, dfrB6, was found in a dfrB6-aadA1 cassette array in class 1 integrons. This array was isolated from several multiply antibiotic-resistant Salmonella enterica serovar Infantis strains that appear to be clonally related. The DfrB6 dihydrofolate reductase conferred resistance to trimethoprim.

Aquariums as reservoirs for multidrug-resistant Salmonella Paratyphi B.

Multidrug-resistant Salmonella enterica serovar Paratyphi B dT+ isolates from patients with gastroenteritis were identical with isolates from their home aquariums. Matched isolates had identical phage types, XbaI and IS200 profiles, and Salmonella genomic island 1 (SGI1). Ornamental fish tanks are reservoirs for SGI1-containing S.

The genomic island SGI1, containing the multiple antibiotic resistance region of Salmonella enterica serovar Typhimurium DT104 or variants of it, is widely distributed in other S. enterica serovars.

The global dissemination of the multiply-antibiotic-resistant Salmonella enterica serovar Typhimurium DT104 clone with the resistance genes located in a class 1 integron, here designated In104, within genomic island SGI1 is a significant public health issue. Here, we have shown that SGI1 and variants of it carrying different combinations of resistance genes are found in several Salmonella enterica serovars. These are serovars Cerro, Derby, Dusseldorf, Infantis, Kiambu, and Paratyphi B dT(+) isolated from human infections and serovar Emek from sewage effluent.

New integron-associated gene cassette encoding a 3-N-aminoglycoside acetyltransferase.

A fifth gene cassette containing an aacC gene, aacCA5, was found in an aacCA5-aadA7 cassette array in a class 1 integron isolated from a multiply drug resistant Salmonella enterica serovar Kentucky strain. The AacC-A5 or AAC(3)-Ie acetyltransferase encoded by aacCA5 is related to other AAC(3)-I enzymes and confers resistance to gentamicin.