Conjugation resistance plasmid transfer

There are several mechanisms by which plasmids can serve as the vehicle to transfer resistance determinants to sensitive bacteria. These include transduction, transformation, and conjugation. Resistance that is acquired by this type of horizontal transfer can become rapidly and widely disseminated. 

S. aureus transposons are small mobile elements that often encode resistance genes (P-lactamase, resistance to erythromycin and tetracycline). All the transposons encode a transposase gene, and the product of this gene catalyses excision and/or replication of the element, as well as integration. Horizontal transfer of transposons to other S. aureus cells is presumably mediated by another MGE that is transferred, most likely a plasmid transferred by transduction or conjugation. Conjugative transposons have also been described in S. aureus. However, it is not clear if native conjugative transposons are found in S. aureus (Novick 1990). 

Resistance transfer factor (RTF) A component of a resistance plasmid that implements transfer by conjugation of the plasmid. 

Yu P-L, Pearce LE (1986) Conjugal transfer of streptococcal antibiotic resistance plasmids into Clostridium acetobutylicum. Biotechnol Lett... 

Fig. 1 Transfer of plasmid by conjugation and generation of a new resistant cell...

Long-term, low-level feeding of penicillin and the tetracyclines promotes, by natural selection from the pool of normal intestinal flora, those enteric (gut) bacteria that contain R-plasmids. R-plasmids, also known as R-factors, are extrachromosomal genetic material which confer antibiotic resistance to host bacteria. These plamids can be transferred between various kinds of bacteria through cell-to-cell contact (conjugation). Simultaneous resistance to several unrelated antibiotics is commonly carried on a single plasmid and therefore is simultaneously transferred from one bacterium to another. 

The transfer of resistance can be achieved by conjugation, transduction, and transformation. There is also a phenomenon of transposition by which resistance determinants pass from one plasmid to another or to a chromosome or to a bacteriophage, thus allowing construction of new plasmids under the pressure of new antibiotic exposure. 

DNA transfer of drug resistance Of particular clinical concern is resistance acquired due to DNA transfer from one organism to another. Resistance properties are usually encoded in extrachro-mosomal R factors (plasmids). These may enter cells by processes such as transduction (phage-mediated), transformation or, most importantly, bacterial conjugation. 

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