Incompatibility Groups and the Classification of fi ⁻ Resistance Factors

Abstract

Incompatibility between R factors has been reported by several authors, and four incompatibility groups have already been described by Datta and Hedges among Rfifactors. The stability of 12 plasmids in pairs was studied after 116 crosses, and five new groups were found, designated 5, 6, 7, 8, and 9. Each plasmid studied belongs to one single group. Incompatibility between plasmids in pairs is a clear-cut phenomenon, is easy to observe, and can provide a reliable method for recognizing and classifying resistance factors, and for tracing their spread among bacterial species. Previous studies on drug resistance factors have shown that these plasmids can be classified in two groups, Rfi-and Rfi-, according to their effects on the fertility of male strains of Escherichia coli (Watanabe et al., 26). Rfi+ factors, when present in an Hfr strain, are also able to prevent the lysis of this strain by malespecific phages. This property is frequently used to distinguish Rfiand Rfifactors, and it was shown by Egawa and Hirota (9) that Rfi' factors repress the synthesis of F pili by male strains of E. coli. Bacteria carrying transmissible R factors synthetize external appendages called R pili. On the basis of morphological studies of these pili, it was suggested that Rfipili were related to F pili and Rfi-pili to I pili (i.e., pili synthetized by bacteria carrying a ColI factor). Consequently Rfifactors were also called "Flike" or "R(f)," and Rfifactors "I-like" or "R(i)." These facts have been extensively discussed by Meynell, Meynell and Datta (15) and by Novick (17). However, it was observed

Plasmids and Evolutionary Rescue by Drug Resistance

“…Groups of mutually incompatible plasmids can be experimentally described (Chabbert et al. ; Thomas and Smith ), and it is reasonable to assume that incompatibility will reduce the possibility that a bacteria with a resident plasmid can receive another plasmid from the same incompatibility group via conjugation. The precise details of this effect will likely be complex, with the processes that mediate incompatibility varying between incompatibility groups, and from one bacterial species to another.…”

Survey of Klebsiella pneumoniae producing extended-spectrum beta-lactamases: prevalence of TEM-3 and first identification of TEM-26 in France

“…Conjugation experiments were performed by mixing equal volumes (1 ml) of exponentially growing cultures of K. pneumoniae RIC and Escherichia coli K-12 J53-2 resistant to rifampin or E. coli K-12 C600 resistant to nalidixic acid, as previously described (4). Transconjugants were selected on plates supplemented with ceftazidime (4 g/ml) and rifampin (250 g/ml) or nalidixic acid (50 g/ml).…”

Incompatibility Reactions of R Plasmids Isolated from Escherichia coli of Animal Origin

“…Since in some cases this affects only one marker out of four, the molecular nature of these plasmids will have to be carefully investigated. Although such multiple incompatibility was not envisaged in early reports on R-plasmid incompatibility grouping (2,9), recently similar observations have been made by at least two groups of workers (25,12). These observations of multiple incompatibility have implications, however, for the significance of incompatibility grouping in R plasmid classification.…”