Tn5253, the pneumococcal omega (cat tet) BM6001 element, is a composite structure of two conjugative transposons, Tn5251 and Tn5252

Abstract

that the conjugative transfer of all these elements shares a common mechanism, as the elements are derived from an ancestral element with transfer properties.Tn5253, formerly called the fl(cat tet) element (36), was originally detected as a heterologous insertion in the chromosome of the plasmid-free clinical isolate S. pneumoniae BM6001 (3, 9). By inserting the Escherichia coli vector plasmid pVA891 (22) (which is incapable of autonomous replication in streptococci) at many sites specifically within Tn5253, we were able to clone and recover parts of the element in E. coli (37). Physical analysis of the passenger DNAs from these plasmids made it possible to construct a detailed restriction map of this 65.5-kb element, to localize the drug resistance determinants, and to identify its junction and target regions in the pneumococcal chromosome (36), (Fig. 1)

Caracterización molecular de aislamientos invasores colombianos de Streptococcus pneumoniae serotipo 5 recuperados entre 1994 y 2004.

“…De igual manera, la ausencia de la banda se asoció con aislamientos susceptibles a estos dos antibióticos (5). Este fragmento de 340 Kb contiene los genes tetM y cat (2), que confieren resistencia a tetraciclina y cloranfenicol respectivamente, y que hacen parte del transposón conjugativo Tn5253 (19). La presencia de la banda puede explicarse por la inserción de este transposón en el genoma del neumococo, evento genético que puede alterar los sitios de restricción de la enzima Sma I y generar nuevos patrones electroforéticos (13,20).…”

Molecular mechanisms and epidemiology of resistance in Streptococcus pneumoniae in the Middle East region

“…Cat causes enzymatic modification, which is associated with chloramphenicol acetylation and the generation of inoperative O-acetoxy chloramphenicol products, further hampering its successful binding to ribosomes [84,85]. In S. pneumoniae, the cat gene is carried by Tn5253, a composite transposon identified in 1991 [74]. In 2000, a linearized version of pC194, a cat carrier plasmid originally described in Staphylococcus aureus, was found integrated into the S. pneumoniae chromosome [86].…”

“…This genetic element was first named omega cat-tet or (cat-tet) [73], and was then renamed Tn5253 [74]. Tn5253 is composed of two distinct conjugative transposons, each displaying its own conjugal proprieties: (1) Tn5251 (related to the Tn916 Ala203Val murM Mosaic gene Penicillin and cephalosporin [23] family), the 18 kb tet-carrier transposon inserted within (2) Tn5252, the cat-carrier that comprises the rest of Tn5253 [74]. Moreover, Tn5251 has shown the potential for independent transfer to a variety of bacterial species after excision from Tn5253 and a capacity to combine with other resistance-determinant carriers [75].…”

Mobile genetic elements in the genus Bacteroides, and their mechanism(s) of dissemination

“…Due to their ability to integrate into DNA, it should not be surprising to find chimeric transposons, i.e., a transposon integrated into another transposon. However, to date, there are only two chimeric transposons in which a CTn inserted into another CTn, have been reported, a CTn in grampositive bacteria, the streptococcal Tn5253 76 ; and a CTn in gram negative bacteria, the Bacteroides CTn12256. 77 Although the 188kb CTn12256 was isolated from a clinical isolate in 1977, only recently has its chimeric nature been studied in more detail.…”