Gene transfers, resistance factors

Bacteroides have a tetracycline resistance factor, which also acts on the ribosomes but is only distantly related to TetM and TetO (less than 40% similarity)- It was named TetQ to distinguish it from the others (25). The resistance gene is embedded in a trans-poson structure (26), which predisposes the resistance factor to be mobilized. Originally, horizontal transfer of TetQ appeared to be confined to Bacteroides (27). However, it was... 

As antibiotics came into widespread use, an unanticipated problem arose in the rapid development of resistance by bacteria. The problem was made acute by the fact that resistance genes are easily transferred from one bacterium to another by the infectious R-factor plasmids.a-d Since resistance genes for many different antibiotics may be carried on the same plasmid, "super bacteria," resistant to a large variety of antibiotics, have developed, often in hospitals. 

Nakaya [224] reported the presence of chloramphenicol acetyl transferase in a strain of Ps. aeruginosa. The enzyme activity was reported to be low and no chloramphenicol esters were detected. R factor mediated resistance to chloramphenicol in pseudomonas strains has been reported by Witchitz and Chabbert [225], However, Ingram, Richmond and Sykes [205] failed to transfer the R factor mediated chloramphenicol resistance gene to Ps. aeruginosa from a strain of Klebsiella aerogenes. 

Genes can also be transferred in vitro into TILs associated with melanoma in an attempt to potentiate the cytotoxicity of these cells. Rosenberg and colleagues were the first to attempt to transduce the gene coding for resistance to neomycin into human TILs. This approach has since been used to transfer the tumor necrosis factor gene into TILs. 

Plasmids are autonomous, circular DNA molecules (from around 1 kilobase pairs (kb) to several hundreds of kb in size) that are capable of self-replication within a bacterial cell (Figure 1). Plasmids contain some genes involved in their own replication and transfer between bacteria, but can also harbor additional genes that can impart such biochemical capabilities as antibiotic resistance, utilization of additional nutrients, production of pathogenic factors, nitrogen fixation, or the production of bacteriocins. 

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