RESUMO
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. enterica serovar Paratyphi B dT(+) strains increased during the next few years and occurred sporadically in all states of Australia. Several molecular criteria were used to show that the early isolates are very closely related to one another and to strains isolated during the following few years and in 2000 and 2003 from home aquariums and their owners. Early isolates from travelers returning from Indonesia shared the same features. Thus, they appear to represent a true clone arising from a single cell that acquired SGI1. Some minor differences in the resistance profiles and molecular profiles also were observed, indicating the ongoing evolution of the clone, and phage type differences were common, indicating that this is not a useful epidemiological marker over time. Three isolates from 1995, 1998, and 1999 contained a complete sul1 gene but were susceptible to sulfamethoxazole due to a point mutation that creates a premature termination codon. This SGI1 type was designated SGI1-R. The loss of resistance genes also was examined. When strains were grown for many generations in the absence of antibiotic selection, the loss of SGI1 was not detected. However, variants SGI1-C (resistance profile SmSpSu) and SGI1-B (resistant to ApSu), which had lost part of the integron, arose spontaneously, presumably via homologous recombination between duplications in the In104 complex integron.
Assuntos
Farmacorresistência Bacteriana Múltipla , Ilhas Genômicas , Salmonella paratyphi B/efeitos dos fármacos , Salmonella paratyphi B/genética , Tartaratos/metabolismo , Elementos de DNA Transponíveis , Eletroforese em Gel de Campo Pulsado , Salmonella paratyphi B/metabolismoRESUMO
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.
Assuntos
Integrons , Plasmídeos , Salmonella enterica/genética , Animais , Sequência de Bases , Conjugação Genética , Humanos , Dados de Sequência Molecular , SuínosRESUMO
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. Instead, tnpR was found to be adjacent to S044, and the integron is located 6.9 kb away, within S023. In both SGI1 and SGI2, the 25-bp inverted repeats that mark the outer ends of class 1 integrons are flanked by a 5-bp duplication of the target, indicating that incorporation of the integron was by transposition. A small number of differences between the sequences of the backbones of SGI1 and SGI2 were also found. Hence, a class 1 integron has entered two different variants of the SGI backbone to generate two distinct lineages. Despite this, the integron in SGI2 has a complex structure that is very similar to that of In104 in SGI1. Differences are in the cassette arrays and in the gene which encodes the chloramphenicol and florfenicol efflux protein. The CmlA9 protein, encoded by InEmek, is only 92.8% identical to FloRc (also a CmlA family protein) from SGI1. A variant form of SGI2, SGI2-A, which has lost the tet(G) and cmlA9 resistance determinants, was found in one strain.
Assuntos
Ilhas Genômicas , Salmonella enterica/genética , Sequência de Bases , Mapeamento Cromossômico , DNA Bacteriano/genética , Farmacorresistência Bacteriana/genética , Evolução Molecular , Variação Genética , Genoma Bacteriano , Humanos , Integrons , Dados de Sequência Molecular , Salmonella enterica/classificação , Salmonella enterica/efeitos dos fármacos , Salmonella enterica/isolamento & purificação , Especificidade da EspécieRESUMO
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. The mer module is a hybrid of those found in Tn501 and Tn21. This mer region and a further uncharacterized segment of at least 10 kb appear to have been incorporated between IRt and the SGI1 backbone. These findings demonstrate that the multidrug resistance region in SGI1 can incorporate new DNA segments in the same way as multiple antibiotic resistance regions in plasmids.
Assuntos
Farmacorresistência Bacteriana Múltipla/genética , Ilhas Genômicas/genética , Salmonella enterica/genética , Sequência de Bases , Southern Blotting , Mapeamento Cromossômico , DNA Bacteriano/química , DNA Bacteriano/genética , Genoma Bacteriano/genética , Integrons/genética , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Salmonella enterica/efeitos dos fármacos , Análise de Sequência de DNA , Homologia de Sequência do Ácido NucleicoAssuntos
Proteínas de Bactérias/genética , Integrons/genética , Macrolídeos/metabolismo , Nucleotidiltransferases/genética , Salmonella enterica/genética , Sequência de Aminoácidos , Sequência de Bases , Farmacorresistência Bacteriana Múltipla , Humanos , Lincosamidas , Macrolídeos/farmacologia , Dados de Sequência Molecular , Nucleotidiltransferases/química , Nucleotidiltransferases/metabolismo , Salmonella enterica/classificação , Salmonella enterica/efeitos dos fármacosRESUMO
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.
Assuntos
Genes Bacterianos , Integrons , Salmonella enterica/genética , Tetra-Hidrofolato Desidrogenase/genética , Sequência de Aminoácidos , Animais , Anti-Infecciosos Urinários/farmacologia , Sequência de Bases , Gatos , Galinhas , Cães , Farmacorresistência Bacteriana Múltipla/genética , Antagonistas do Ácido Fólico/farmacologia , Testes de Sensibilidade Microbiana , Dados de Sequência Molecular , Salmonella enterica/classificação , Salmonella enterica/efeitos dos fármacos , Salmonella enterica/isolamento & purificação , Homologia de Sequência de Aminoácidos , Sorotipagem , Trimetoprima/farmacologia , Resistência a Trimetoprima/genéticaRESUMO
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. Paratyphi B dT+.
Assuntos
Reservatórios de Doenças/microbiologia , Farmacorresistência Bacteriana Múltipla , Abrigo para Animais , Salmonella paratyphi B/efeitos dos fármacos , Salmonella paratyphi B/isolamento & purificação , Microbiologia da Água , Animais , Peixes , Ilhas Genômicas/genética , Humanos , Febre Paratifoide/epidemiologia , Febre Paratifoide/microbiologia , FenótipoRESUMO
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. Two new variants, SGI1-I and SGI1-J, both of which include the dfrA1-orfC cassette array, were identified.
Assuntos
Antibacterianos/farmacologia , Ilhas Genômicas/efeitos dos fármacos , Salmonella enterica/genética , Salmonella typhi/efeitos dos fármacos , Animais , Austrália , Resistência a Múltiplos Medicamentos/genética , Humanos , Integrons , Dados de Sequência Molecular , Infecções por Salmonella/microbiologia , Salmonelose Animal/microbiologia , Salmonella typhi/genética , Esgotos/microbiologiaRESUMO
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.