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Characterization of a new SCCmec element in Staphylococcus cohnii.

Zong Z, Lü X - PLoS ONE (2010)

Bottom Line: This element is flanked by 8-bp perfect inverted repeats and is similar to type III SCCmec in S. aureus and a SCCmec in S. pseudintermedius but with different J1 and J3 regions.WC28 SCCmec was arranged in tandem with an additional SCC element with ccrC, SCC(WC28), but the two elements might have integrated independently rather than constituted a composite.This study adds new evidence of the diversity of SCCmec in CoNS and highlights the need for characterizing the 'non-typable' SCCmec to reveal the gene pool associated with mecA.

View Article: PubMed Central - PubMed

Affiliation: Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, China. zongzhiyong@gmail.com

ABSTRACT

Background: Many SCCmec elements of coagulase-negative staphylococci (CoNS) could not be typed using multiplex PCR. Such a 'non-typable' SCCmec was encountered in a Staphylococcus cohnii isolate.

Methodology/principal findings: The SCCmec type of methicillin-resistant S. cohnii clinical isolate WC28 could not be assigned using multiplex PCR. Newly-designed primers were used to amplify ccrA and ccrB genes. The whole SCCmec was obtained by three overlapping long-range PCR, targeting regions from left-hand inverted repeat (IRL) to ccrA/B, from ccrA/B to mecA and from mecA to orfX. The region abutting IRL was identified using inverse PCR with self-ligated enzyme-restricted WC28 fragments as the template. WC28 SCCmec had a class A mec gene complex (mecI-mecR1-mecA). The ccrA and ccrB genes were closest (89.7% identity) to ccrA(SHP) of Staphylococcus haemolyticus strain H9 and to ccrB3 (90% identity) of Staphylococcus pseudintermedius strain KM241, respectively. Two new genes potentially encoding AAA-type ATPase were found in J1 region and a ψTn554 transposon was present in J2 region, while J3 region was the same as many SCCmec of Staphylococcus aureus. WC28 SCCmec abutted an incomplete SCC element with a novel allotype of ccrC, which was closest (82% identity) to ccrC1 allele 9 in Staphylococcus saprophyticus strain ATCC 15305. Only two direct target repeat sequences, one close to the 3'-end of orfX and the other abutting the left end of WC28 SCCmec, could be detected.

Conclusions/significance: A new 35-kb SCCmec was characterized in a S. cohnii isolate, carrying a class A mec gene complex, new variants of ccrA5 and ccrB3 and two novel genes in the J1 region. This element is flanked by 8-bp perfect inverted repeats and is similar to type III SCCmec in S. aureus and a SCCmec in S. pseudintermedius but with different J1 and J3 regions. WC28 SCCmec was arranged in tandem with an additional SCC element with ccrC, SCC(WC28), but the two elements might have integrated independently rather than constituted a composite. This study adds new evidence of the diversity of SCCmec in CoNS and highlights the need for characterizing the 'non-typable' SCCmec to reveal the gene pool associated with mecA.

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Related in: MedlinePlus

A proposed model for double crossover-mediated exchange between two SCCmec.When two different SCCmec (not to scale) contain two sequences of homology, exemplified by ccrB3 and IS431 here, two homologous recombination events (the upper panel) occurring between the two sequences can result in exchange of the intervening components (lines of different thicknesses) between the two SCCmec (the lower panel).
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pone-0014016-g002: A proposed model for double crossover-mediated exchange between two SCCmec.When two different SCCmec (not to scale) contain two sequences of homology, exemplified by ccrB3 and IS431 here, two homologous recombination events (the upper panel) occurring between the two sequences can result in exchange of the intervening components (lines of different thicknesses) between the two SCCmec (the lower panel).

Mentions: As a whole, the WC28 SCCmec is very similar to that of S. pseudintermedius KM241 except at both ends (Figure). Based on characteristics of the mec and ccr gene complexes, the WC28 and KM241 SCCmec should be considered together as a new type, while the different J1 and J3 regions suggest that these two SCCmec are of two distinct subtypes. The WC28, KM241 and type III (S. aureus 85/2082) SCCmec share a similar “core” including the ccr and mec gene complexes and the J2 region suggesting a possible common origin. The divergent J1 and J3 regions in these three SCCmec might have resulted from two recombination events occurring in two regions of homology, one of which appears to be IS431 downstream of mecA and another might be ccrB3 or adjacent sequences (a proposed scheme is shown in Figure 2). The similarity and divergence between SCCmec in CoNS and those in S. aureus highlights the need to characterize SCCmec elements in CoNS, particularly those not identified by PCR-based typing schemes. The information generated is essential for revealing the potential reservoir of components that could allow formation of diverse elements carrying mecA and for appreciating the origin and the evolution of SCCmec.


Characterization of a new SCCmec element in Staphylococcus cohnii.

Zong Z, Lü X - PLoS ONE (2010)

A proposed model for double crossover-mediated exchange between two SCCmec.When two different SCCmec (not to scale) contain two sequences of homology, exemplified by ccrB3 and IS431 here, two homologous recombination events (the upper panel) occurring between the two sequences can result in exchange of the intervening components (lines of different thicknesses) between the two SCCmec (the lower panel).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2984492&req=5

pone-0014016-g002: A proposed model for double crossover-mediated exchange between two SCCmec.When two different SCCmec (not to scale) contain two sequences of homology, exemplified by ccrB3 and IS431 here, two homologous recombination events (the upper panel) occurring between the two sequences can result in exchange of the intervening components (lines of different thicknesses) between the two SCCmec (the lower panel).
Mentions: As a whole, the WC28 SCCmec is very similar to that of S. pseudintermedius KM241 except at both ends (Figure). Based on characteristics of the mec and ccr gene complexes, the WC28 and KM241 SCCmec should be considered together as a new type, while the different J1 and J3 regions suggest that these two SCCmec are of two distinct subtypes. The WC28, KM241 and type III (S. aureus 85/2082) SCCmec share a similar “core” including the ccr and mec gene complexes and the J2 region suggesting a possible common origin. The divergent J1 and J3 regions in these three SCCmec might have resulted from two recombination events occurring in two regions of homology, one of which appears to be IS431 downstream of mecA and another might be ccrB3 or adjacent sequences (a proposed scheme is shown in Figure 2). The similarity and divergence between SCCmec in CoNS and those in S. aureus highlights the need to characterize SCCmec elements in CoNS, particularly those not identified by PCR-based typing schemes. The information generated is essential for revealing the potential reservoir of components that could allow formation of diverse elements carrying mecA and for appreciating the origin and the evolution of SCCmec.

Bottom Line: This element is flanked by 8-bp perfect inverted repeats and is similar to type III SCCmec in S. aureus and a SCCmec in S. pseudintermedius but with different J1 and J3 regions.WC28 SCCmec was arranged in tandem with an additional SCC element with ccrC, SCC(WC28), but the two elements might have integrated independently rather than constituted a composite.This study adds new evidence of the diversity of SCCmec in CoNS and highlights the need for characterizing the 'non-typable' SCCmec to reveal the gene pool associated with mecA.

View Article: PubMed Central - PubMed

Affiliation: Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, China. zongzhiyong@gmail.com

ABSTRACT

Background: Many SCCmec elements of coagulase-negative staphylococci (CoNS) could not be typed using multiplex PCR. Such a 'non-typable' SCCmec was encountered in a Staphylococcus cohnii isolate.

Methodology/principal findings: The SCCmec type of methicillin-resistant S. cohnii clinical isolate WC28 could not be assigned using multiplex PCR. Newly-designed primers were used to amplify ccrA and ccrB genes. The whole SCCmec was obtained by three overlapping long-range PCR, targeting regions from left-hand inverted repeat (IRL) to ccrA/B, from ccrA/B to mecA and from mecA to orfX. The region abutting IRL was identified using inverse PCR with self-ligated enzyme-restricted WC28 fragments as the template. WC28 SCCmec had a class A mec gene complex (mecI-mecR1-mecA). The ccrA and ccrB genes were closest (89.7% identity) to ccrA(SHP) of Staphylococcus haemolyticus strain H9 and to ccrB3 (90% identity) of Staphylococcus pseudintermedius strain KM241, respectively. Two new genes potentially encoding AAA-type ATPase were found in J1 region and a ψTn554 transposon was present in J2 region, while J3 region was the same as many SCCmec of Staphylococcus aureus. WC28 SCCmec abutted an incomplete SCC element with a novel allotype of ccrC, which was closest (82% identity) to ccrC1 allele 9 in Staphylococcus saprophyticus strain ATCC 15305. Only two direct target repeat sequences, one close to the 3'-end of orfX and the other abutting the left end of WC28 SCCmec, could be detected.

Conclusions/significance: A new 35-kb SCCmec was characterized in a S. cohnii isolate, carrying a class A mec gene complex, new variants of ccrA5 and ccrB3 and two novel genes in the J1 region. This element is flanked by 8-bp perfect inverted repeats and is similar to type III SCCmec in S. aureus and a SCCmec in S. pseudintermedius but with different J1 and J3 regions. WC28 SCCmec was arranged in tandem with an additional SCC element with ccrC, SCC(WC28), but the two elements might have integrated independently rather than constituted a composite. This study adds new evidence of the diversity of SCCmec in CoNS and highlights the need for characterizing the 'non-typable' SCCmec to reveal the gene pool associated with mecA.

Show MeSH
Related in: MedlinePlus