Evidence for a disseminated erythromycin resistance determinant mediated by Tn917-like sequences among group D streptococci isolated from pigs, chickens, and humans

Rollins, Larry D.; Lee, L N; LeBlanc, Donald J.

doi:10.1128/aac.27.4.439

Cited by 45 publications

(26 citation statements)

References 15 publications

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“…The ermB gene was found on plasmids in only nine of the isolates examined, suggesting that dissemination of the gene via plasmids was not likely. This does not discount the presence of transposable elements, such as Tn917, that could disseminate ermB among the isolates, but it suggests the probability is low (18). Although the plasmids have not been fully characterized, the presence of similar-sized plasmids from two separate farms does suggest that the plasmids may be the same but have yet to be widely distributed to other enterococcal isolates.…”

Section: Discussionmentioning

confidence: 99%

Effects of Tylosin Use on Erythromycin Resistance in Enterococci Isolated from Swine

Jackson

Fedorka–Cray

Barrett

et al. 2004

Appl Environ Microbiol

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The effect of tylosin on erythromycin-resistant enterococci was examined on three farms; farm A used tylosin for growth promotion, farm B used tylosin for treatment of disease, and farm C did not use tylosin for either growth promotion or disease treatment. A total of 1,187 enterococci were isolated from gestation, farrowing, suckling, nursery, and finishing swine from the farms. From a subset of those isolates (n ‫؍‬ 662), 59% (124 out of 208), 28% (80 out of 281), and 2% (4 out of 170) were resistant to erythromycin (MIC > 8 g/ml) from farms A, B, and C, respectively. PCR analysis and Southern blotting revealed that 95% (65 out of 68) of isolates chosen from all three farms for further study were positive for ermB, but all were negative for ermA and ermC. By using Southern blotting, ermB was localized to the chromosome in 56 of the isolates while 9 isolates from farms A and B contained ermB on two similar-sized plasmid bands (12 to 16 kb). Pulsed-field gel electrophoresis revealed that the isolates were genetically diverse and represented a heterogeneous population of enterococci. This study suggests that although there was resistance to a greater number of enterococcal isolates on a farm where tylosin was used as a growth promotant, resistant enterococci also existed on a farm where no antimicrobial agents were used.

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Section: Discussionmentioning

confidence: 99%

Effects of Tylosin Use on Erythromycin Resistance in Enterococci Isolated from Swine

Jackson

Fedorka–Cray

Barrett

et al. 2004

Appl Environ Microbiol

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“…Furthermore, all of these erm(B)-containing strains were also positive for the detection of a Tn916-Tn1545 element. In this context, it should be mentioned that erm(B) genes in enterococci can also occur on other mobile elements, such as conjugative multiresistance plasmids (47) or members of the Tn917 family (41).…”

Section: Resultsmentioning

confidence: 99%

Prevalence and Molecular Characterization of Tetracycline Resistance in Enterococcus Isolates from Food

Huys

D'Haene

Collard

et al. 2004

Appl Environ Microbiol

194

112

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In the present study, a collection of 187 Enterococcus food isolates mainly originating from European cheeses were studied for the phenotypic and genotypic assessment of tetracycline (TC) resistance. A total of 45 isolates (24%) encompassing the species Enterococcus faecalis (n ‫؍‬ 33), E. durans (n ‫؍‬ 7), E. faecium (n ‫؍‬ 3), E. casseliflavus (n ‫؍‬ 1), and E. gallinarum (n ‫؍‬ 1) displayed phenotypic resistance to TC with MIC ranges of 16 to 256 g/ml. Eight of these strains exhibited multiresistance to TC, erythromycin, and chloramphenicol. By PCR detection, TC resistance could be linked to the presence of the tet(M) (n ‫؍‬ 43), tet(L) (n ‫؍‬ 16), and tet(S) (n ‫؍‬ 1) genes. In 15 isolates, including all of those for which the MIC was 256 g/ml, both tet(M) and tet(L) were found. Furthermore, all tet(M)-containing enterococci also harbored a member of the Tn916-Tn1545 conjugative transposon family, of which 12 erythromycin-resistant isolates also contained the erm(B) gene. Filter mating experiments revealed that 10 E. faecalis isolates, 3 E. durans isolates, and 1 E. faecium isolate could transfer either tet(M), tet(L), or both of these genes to E. faecalis recipient strain JH2-2. In most cases in which only tet(M) was transferred, no detectable plasmids were acquired by JH2-2 but instead all transconjugants contained a member of the Tn916-Tn1545 family. Sequencing analysis of PCR amplicons and evolutionary modeling showed that a subset of the transferable tet(M) genes belonged to four sequence homology groups (SHGs) showing an internal homology of >99.6%. Two of these SHGs contained tet(M) mosaic structures previously found in Tn916 elements and on Lactobacillus and Neisseria plasmids, respectively, whereas the other two SHGs probably represent new phylogenetic lineages of this gene.As lactic acid bacteria, enterococci are natural inhabitants of the gastrointestinal systems of mammals, but they are also known to occur in soil and fecally polluted surface waters and on plants and vegetables (26,31,35). Because of their high prevalence in the gastrointestinal tracts of many food animals, it is often unavoidable that these organisms enter the human food chain via contamination of raw milk or raw meat. For many years, the presence of enterococci in foods has been highly controversial. On the one hand, Enterococcus strains can harbor specific biochemical traits that are essential in the manufacturing of various fermented milk products, and some strains are technologically exploited as functional starters or probiotics (12, 17). On the other hand, enterococci have also been implicated in the spoilage of processed meats (14, 51) and include strains that have been recognized as emerging human pathogens mostly in nosocomial but also in community-acquired infections (for a review, see reference 29).Triggered by the apparent duality between their beneficial and harmful properties, a lot of research has focused on the potential role of food enterococci as reservoirs and/or vehicles of antibiotic resistance (AR) and viru...

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“…Competent cultures of S. sanguis var. Challis were prepared as described by Rollins et al (23), and DNA was added at a concentration of approximately 1 ,ug/ml. After incubation for 4 h, samples were spread on modified LCM agar containing 10 mM lactose.…”

Section: Materils and Methodsmentioning

confidence: 99%

Molecular and genetic characterization of lactose-metabolic genes of Streptococcus cremoris

Inamine¹,

Lee²,

LeBlanc³

1986

J Bacteriol

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(21), S. mutans (7), S. salivarius (7), and S. sanguis (7).The genetic determinants for lactose metabolism can be either chromosomal, as in S. sanguis (25), or plasmid borne, as in S. cremoris and S. lactis (21). These species also differ in the molecular size and regulation of expression of the p-p-gal enzyme. For example, the 40,000-dalton p-p-gal (25) of S. lactis is synthesized constitutively; the enzyme levels found in cells grown on ribose are the same as in those grown on lactose (12, 13). The synthesis of the 52,000-dalton p-p-gal (25) Martin, unpublished observation). The lac-83 strain is a lactose-insensitive derivative of the lac-8 strain that is Lacdue to mutations in both lac-PTS and p-p-gal (25). The lac-8 and lac-83 strains can be transformed to a Lac' phenotype with S. lactis plasmid DNA (8, 25). The Lac' transformants of the S. sanguis lac-83 strain express the S. lactis genes as judged by the presence of the 40,000-dalton S. lactis plasmid-encoded p-p-gal and by the characteristic galactose/ lactose lac-PTS activity ratio (8,25). Plasmid DNA has not been recovered from any of these transformants (8, 25). S.sanguis Lac' transformants can also be obtained with restriction endonuclease-digested S. lactis plasmid DNA or with purified fragments thereof (9; LeBlanc et al., unpublished observations), suggesting that these transformants have resulted from the integration of S. lactis lac sequences into the S. sanguis chromosome. Integration is not the only mechanism for successful transformation of S. sanguis by S. lactis DNA, because a 23-kilobase-pair (kbp) S. lactis Lac+-encoding plasmid fragment has been subcloned in S. sanguis on a plasmid vector (9).In this laboratory we have studied the lactose-metabolic genes of S. cremoris by transforming S. sanguis Lacmutants with both whole and restriction endonucleasedigested S. cremoris lactose plasmid DNA. As in the S. lactis plasmid studies, S. cremoris plasmid DNA could not be isolated from the Lac' S. sanguis transformants. Attempts were made to clone the lactose-metabolic S. cremoris DNA in S. sanguis with streptococcal plasmid vectors.Although stable Lac' S. sanguis transformants were obtained, recombinant plasmid DNA could not be recovered. These transformation results, together with those obtained with the S. lactis plasmids, suggest that chromosomal integration may be the major mechanism by which S. sanguis can stably maintain and express both S. crentoris and S. lactis lactose-metabolic genes. We sought to clarify this phenomenon by cloning S. cremoris Lac' DNA in a heterologous system with Escherichia coli as the transformation recipient. The same approach was used by Maeda and

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Evidence for a disseminated erythromycin resistance determinant mediated by Tn917-like sequences among group D streptococci isolated from pigs, chickens, and humans

Cited by 45 publications

References 15 publications

Effects of Tylosin Use on Erythromycin Resistance in Enterococci Isolated from Swine

Effects of Tylosin Use on Erythromycin Resistance in Enterococci Isolated from Swine

Prevalence and Molecular Characterization of Tetracycline Resistance in Enterococcus Isolates from Food

Molecular and genetic characterization of lactose-metabolic genes of Streptococcus cremoris

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