IS 21-558 Insertion Sequences Are Involved in the Mobility of the Multiresistance Gene cfr

Abstract

During a study of florfenicol-resistant porcine staphylococci from Denmark, the genes cfr and fexA were detected in the chromosomal DNA or on plasmids of Staphylococcus hyicus, Staphylococcus warneri, and Staphylococcus simulans. A novel variant of the phenicol resistance transposon Tn558 was detected on the ca. 43-kb plasmid pSCFS6 in S. warneri and S. simulans isolates. Sequence analysis of a 22,010-bp segment revealed that the new Tn558 variant harbored an additional resistance gene region integrated into the tnpC reading frame. This resistance gene region consisted of the clindamycin exporter gene lsa(B) and the gene cfr for combined resistance to phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A antibiotics bracketed by IS21-558 insertion sequences orientated in the same direction. A 6-bp target site duplication was detected at the integration site within tnpC. Transpositionally active forms of the IS21-558 element, known as minicircles, were detected by PCR and suggest that this insertion sequence is involved in the mobility of the multiresistance gene cfr. Based on the knowledge of the transposition pathways of IS21-like insertion sequences and the sequence features detected, the resistance gene region of plasmid pSCFS6 is believed to have developed via IS21-558-mediated cointegrate formation. The data obtained in this study identified the multiresistance gene cfr not only in three novel host species but also in a novel genetic context whose further analysis suggested that insertion sequences of the type IS21-558 are likely to be involved in the dissemination of cfr.The gene cfr was initially discovered in a bovine Staphylococcus sciuri isolate during a florfenicol surveillance study of staphylococci from animals (19). In 2005, it was shown that the Cfr protein represents a methyltransferase which modifies the 23S rRNA (6). Detailed footprint analysis and mass spectrometric studies showed that the Cfr enzyme adds an additional methyl group at position A2503 (6). This Cfr-mediated modification affected not only the binding of phenicols but also that of members of another four different drug classes to the bacterial ribosome. The corresponding multidrug resistance phenotype was characterized by elevated MICs to phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A (PhLOPS A ) antibiotics, all of which are important antimicrobial agents for the treatment of bacterial infections in humans and/or animals (7). The PhLOPS A phenotype was expressed not only in Staphylococcus aureus but also in Escherichia coli carrying the gene cfr (7).So far, the gene cfr has been detected in six staphylococcal isolates of animal origin, located either on the 17.1-kb plasmid type pSCFS1 or on the 35.7-kb plasmid type pSCFS3 (4). Recently, cfr has also been detected in a methicillin-resistant S. aureus isolate of human origin (8a). In the completely sequenced plasmid pSCFS1, the gene cfr was located in close proximity to other antibiotic resistance genes, such as lsa (B), erm(33)...

Identification of 8-methyladenosine as the modification catalyzed by the radical SAM methyltransferase Cfr that confers antibiotic resistance in bacteria

“…The cfr gene has been found on transposons and in different geographical locations, suggesting that it can be spread within the microbial community Kehrenberg et al 2007). It is alarming that one methyltransferase confers resistance to five different classes of clinically relevant antimicrobial agents.…”

First Report of the Multidrug Resistance Gene cfr in Enterococcus faecalis of Animal Origin

“…Since its initial identification on the multiresistance plasmid pSCFS1 from Staphylococcus sciuri in 2000 (21), several studies have reported the cfr gene in staphylococcal isolates of animal and human origin. In most reports, the cfr gene was located on different plasmids (9,10,16), while in a few cases, it was also detected in the chromosomal DNA (9,14,27). Recently, the first outbreak case of linezolid-resistant, cfr-carrying Staphylococcus aureus was reported in Spain (17), and the cfr gene has also been identified in Panton-Valentine leukocidin-positive sequence type 8 (ST8) methicillin-resistant S. aureus IVa (USA300) (23).…”

Identification and Characterization of the Multidrug Resistance Gene cfr in a Panton-Valentine Leukocidin-Positive Sequence Type 8 Methicillin-Resistant Staphylococcus aureus IVa (USA300) Isolate

“…The larger plasmids pSCFS3 (36 kb) and pSCFS6 (43 kb) also carry the Tn558-associated phenicol resistance gene fexA. In pSCFS3 and pSCFS6, cfr is integrated at different positions within the transposase genes tnpA-tnpB or tnpC of Tn558 (15,18). In some staphylococcal isolates, cfr is located in the chromosomal DNA (15,45).…”

“…It is usually plasmid borne, and three plasmids, pSCFS1, pSCFS3, and pSCFS6 (15,17,18), have been characterized in detail. Plasmid pSCFS1 (17.1 kb) also harbors additional antimicrobial resistance genes, including erm (33), encoding MLS B resistance, or lsa(B), encoding reduced susceptibility to lincosamides (17).…”