Current Status of Staphylococcal Cassette Chromosome mec (SCCmec).
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ABSTRACT:
SUBMITTER: Uehara Y
PROVIDER: S-EPMC8772726 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:ObjectivesTo describe a new subclass of mec class B complex identified in Staphylococcus epidermidis.MethodsFour S. epidermidis isolates obtained from bloodstream infections in patients at University Medical Center Groningen (UMCG) were analysed by phenotypic antibiotic susceptibility testing and WGS.ResultsSequence analysis revealed a new staphylococcal cassette chromosome mec (SCCmec) structure in isolate UMCG335. In this structure, plasmid pUB110 was found to be integrated into SCCmec IVc, creating a new SCCmec subtype, IVUMCG335. SCCmec IVc and a copy of plasmid pUB110 were found in other isolates, UMCG364 and UMCG341, respectively, indicating a probability that SCCmec IVUMCG335 could have evolved at the UMCG. SCCmec of UMCG337 contained a new genetic organization of the mec complex (IS431-ΔmecR1-mecA-IS431-pUB110-IS431-ψIS1272) that we have named B4. This new subclass of mec class B complex originated by IS431-mediated inversion of the DNA segment encompassing the plasmid and most of the genes of the mec complex with the exception of IS1272. As the SCCmec organization in UMCG337 differed by the inversion of an ∼10 kb sequence compared with SCCmec IVUMCG335, we have named it SCCmec subtype IVUMCG337. Isolates UMCG335 and UMCG337 carrying SCCmec IVUMCG335 and IVUMCG337, respectively, were associated with a restriction-modification system and a CRISPR-Cas system, creating a composite island of almost 70 kb.ConclusionsOur findings highlight the importance of IS431 in the evolution of the SCCmec region. The increasing genetic diversity identified in the SCCmec elements imposes a great challenge for SCCmec typing methods and highlights possible difficulties with the SCCmec nomenclature.
| S-EPMC8283725 | biostudies-literature
Project description:Several lines of evidence indicate that the most primitive staphylococcal species, those of the Staphylococcus sciuri group, were involved in the first stages of evolution of the staphylococcal cassette chromosome mec (SCCmec), the genetic element carrying the ?-lactam resistance gene mecA However, many steps are still missing from this evolutionary history. In particular, it is not known how mecA was incorporated into the mobile element SCC prior to dissemination among Staphylococcus aureus and other pathogenic staphylococcal species. To gain insights into the possible contribution of several species of the Staphylococcus sciuri group to the assembly of SCCmec, we sequenced the genomes of 106 isolates, comprising S. sciuri (n = 76), Staphylococcus vitulinus (n = 18), and Staphylococcus fleurettii (n = 12) from animal and human sources, and characterized the native location of mecA and the SCC insertion site by using a variety of comparative genomic approaches. Moreover, we performed a single nucleotide polymorphism (SNP) analysis of the genomes in order to understand SCCmec evolution in relation to phylogeny. We found that each of three species of the S. sciuri group contributed to the evolution of SCCmec: S. vitulinus and S. fleurettii contributed to the assembly of the mec complex, and S. sciuri most likely provided the mobile element in which mecA was later incorporated. We hypothesize that an ancestral SCCmec III cassette (an element carried by one of the most epidemic methicillin-resistant S. aureus clones) originated in S. sciuri possibly by a recombination event in a human host or a human-created environment and later was transferred to S. aureus.
| S-EPMC5444190 | biostudies-literature
Project description:Macrococcus is a bacterial genus that is closely related to Staphylococcus, which typically is isolated from animal skin and products. The genome analysis of multidrug-resistant Macrococcus caseolyticus strain JCSC5402, isolated from chicken, previously led to the identification of plasmid pMCCL2, which carries a transposon containing an unusual form of the Macrococcus mec gene complex (mecA(m)-mecR1(m)-mecI(m)-blaZ(m)). In M. caseolyticus strain JCSC7096, this mec transposon containing the mec gene complex (designated Tn6045 in this study) was found integrated downstream of orfX on the chromosome. Tn6045 of JCSC7096 was bracketed by the direct repeat sequences (DR) specifically recognized by cassette chromosome recombinase (CCR). A non-mecA-containing staphylococcal cassette chromosome (SCC) element, designated SCC(7096), was integrated next to the mec transposon and separated from the latter by a DR. Nested PCR experiments showed that the mec transposon not only was excised singly but also coexcised with SCC(7096) from the chromosome at the DRs. The coexcised elements formed the extrachromosomal closed circular DNA of the SCCmec-like element. SCCmec is known to be the mobile element conveying methicillin (meticillin) resistance in staphylococci. However, its origin has been unknown. Our observation revealed a potential mechanism of the generation of a new SCCmec-like element in M. caseolyticus, a commensal bacterium of food animals.
| S-EPMC2849352 | biostudies-literature
Project description:Excision and integration of staphylococcal cassette chromosome mec (SCCmec) are mediated by cassette chromosome recombinases (Ccr), which play a crucial role in the worldwide spread of methicillin resistance in staphylococci. We report a novel ccr gene, ccrC2, in the SCCmec of a Staphylococcus aureus isolate, BA01611, which showed 62.6% to 69.4% sequence identities to all published ccrC1 sequences. A further survey found that the ccrC2 gene was mainly located among coagulase-negative staphylococci (CoNS) and could be found in staphylococcal isolates from China, the United States, France, and Germany. The ccr gene complex harboring the ccrC2 gene was designated a type 9 complex, and the SCCmec of BA01611 was considered a novel type and was designated type XII (9C2). This novel SCCmec element in BA01611 was flanked by a pseudo-SCC element (?SCCBA01611) carrying a truncated ccrA1 gene. Both individual SCC elements and a composite SCC were excised from the chromosome based on detection of extrachromosomal circular intermediates. We advocate inclusion of the ccrC2 gene and type 9 ccr gene complex during revision of the SCCmec typing method.
| S-EPMC4649182 | biostudies-literature
Project description:Staphylococcal cassette chromosome mec (SCCmec) is a mobile genetic element composed of the mec gene complex, which encodes methicillin resistance, and the ccr gene complex, which encodes the recombinases responsible for its mobility. The mec gene complex has been classified into four classes, and the ccr gene complex has been classified into three allotypes. Different combinations of mec gene complex classes and ccr gene complex types have so far defined four types of SCCmec elements. Now we introduce the fifth allotype of SCCmec, which was found on the chromosome of a community-acquired methicillin-resistant Staphylococcus aureus strain (strain WIS [WBG8318]) isolated in Australia. The element shared the same chromosomal integration site with the four extant types of SCCmec and the characteristic nucleotide sequences at the chromosome-SCCmec junction regions. The novel SCCmec carried mecA bracketed by IS431 (IS431-mecA-DeltamecR1-IS431), which is designated the class C2 mec gene complex; and instead of ccrA and ccrB genes, it carried a single copy of a gene homologue that encoded cassette chromosome recombinase. Since the open reading frame (ORF) was found to encode an enzyme which catalyzes the precise excision as well as site- and orientation-specific integration of the element, we designated the ORF cassette chromosome recombinase C (ccrC), and we designated the element type V SCCmec. Type V SCCmec is a small SCCmec element (28 kb) and does not carry any antibiotic resistance genes besides mecA. Unlike the extant SCCmec types, it carries a set of foreign genes encoding a restriction-modification system that might play a role in the stabilization of the element on the chromosome.
| S-EPMC434217 | biostudies-literature
Project description:The aim of this study was to identify optimized sets of genotyping targets for the staphylococcal cassette chromosome mec (SCCmec). We analyzed the gene contents of 46 SCCmec variants in order to identify minimal subsets of targets that provide useful resolution. This was achieved by firstly identifying and characterizing each available SCCmec element based on the presence or absence of 34 binary targets. This information was used as input for the software "Minimum SNPs," which identifies the minimum number of targets required to differentiate a set of genotypes up to a predefined Simpson's index of diversity (D) value. It was determined that 22 of the 34 targets were required to genotype the 46 SCCmec variants to a D of 1. The first 6, 9, 12, and 15 targets were found to define 21, 29, 35, and 39 SCCmec variants, respectively. The genotypes defined by these marker subsets were largely consistent with the relationships between SCCmec variants and the accepted nomenclature. Consistency was made virtually complete by forcing the computer program to include ccr1 and ccr5 in the target set. An alternative target set biased towards discriminating abundant SCCmec variants was derived by analyzing an input file in which common SCCmec variants were repeated, thus ensuring that markers that discriminate abundant variants had a large effect on D. Finally, it was determined that mecA single nucleotide polymorphisms (SNPs) can increase the overall genotyping resolution, as different mecA alleles were found in otherwise identical SCCmec variants.
| S-EPMC1932536 | biostudies-literature
Project description:Staphylococcus aureus staphylococcal cassette chromosome mec type IV (SSCmec IV) is associated with virulent community-acquired methicillin-resistant Staphylococcus aureus (MRSA) and frequent horizontal transfer among staphylococci. To gain insight into the mechanism of transfer, we studied the ccrA/B type 2 recombinase-mediated excision of SCCmec IV (n = 5 strains) and SCCmec II (n = 2). In SCCmec IV- but not SCCmec II-containing strains, spontaneous excision of the cassette was observed. Introduction of ccrA/B type 2 recombinase genes under control of an S. aureus bacterial phage promoter in the different strains yielded excision of SCCmec II and multiple excision variants of SCCmec IV. Sequencing of the alternatively excised products in SCCmec IV strains identified a 100-bp shortened SCCmec' variant and a 5,877-bp, conserved SCC-like element that lacks mecA and ccrA/B recombinases. Excision of the SCC-like element in wild-type S. aureus was dependent on the presence of SCCmec. The element could be excised separately or as part of a novel composite cassette together with SCCmec. The relative abundance of and variety in SCCmec IV excisions may contribute to the frequency of horizontal transfer and genetic plasticity in SCCmec IV MRSA strains.
| S-EPMC1479121 | biostudies-literature
Project description:Rapid identification and typing of methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) is important for understanding the molecular epidemiology and evolution of MRSA and offers many advantages for controlling transmission in both health care and community settings. We developed a rapid molecular beacon real-time PCR (MB-PCR) assay for staphylococcal cassette chromosome mec (SCCmec) typing. The design of this system is based on the established definition of SCCmec types, namely, the combination of the mec class complex with the ccr allotype. The assay consists of two multiplex panels, the combination of which results in two targets (mec class, ccr) for each SCCmec type. MB-PCR panel I targets mecA, ccrB2, mecI, and the DeltamecR1-IS1272 junction (mec class B); it can definitively identify SCCmec types II and IV. MB-PCR panel II detects ccrC, ccrB1, ccrB3, ccrB4, and the DeltamecR1-IS431 junction (mec class C2) and is therefore capable of identifying SCCmec types I, III, V, and VI in combination with panel I. The method can also detect the recently described novel SCCmec type VIII (ccrAB4 with mec class A). Our assay demonstrated 100% concordance when applied to 162 MRSA strains previously characterized by traditional SCCmec typing schemes. Four geographically and temporally diverse S. aureus collections were also successfully classified by our assay, along with 1,683 clinical isolates comprising both hospital- and community-associated MRSA and methicillin-susceptible S. aureus strains. As many as 96 isolates can be classified easily within 3 to 4 h, including DNA isolation, PCR cycling, and analysis. The assay is rapid, robust, sensitive, and cost-effective, allowing for high-throughput SCCmec typing of MRSA isolates.
| S-EPMC2772623 | biostudies-literature
Project description:Twenty Australian community staphylococci harboring the type V staphylococcal cassette chromosome mec (SCCmec) were found to belong to eight multilocus sequence types. Five were previously unreported novel type V SCCmec elements. The mec complexes were of two types, based on the polymorphisms in the IS431 transposase genes. Five isolates were multiresistant.
| S-EPMC1315930 | biostudies-literature
Project description:We analyzed the staphylococcal cassette chromosome mec (SCCmec) types of 143 fusidic acid- and methicillin-resistant Staphylococcus epidermidis isolates. The most frequent SCCmec type was SCCmec III/SCCHg (53%), followed by SCCmec IV (29%). Clonal spreading of SCCmec III/SCCHg strains contributed to the increased prevalence of SCCmec III. A novel non-mec SCC structure, SCC7684, adjacent to SCCmec III, which carries a new ccrC allotype (ccrC3 allele 1) and contains heavy metal resistance genes, was identified in 14 isolates.
| S-EPMC4958148 | biostudies-literature