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SCCmec, or staphylococcal cassette chromosome mec, is a mobile genetic element of Staphylococcus bacterial species. This genetic sequence includes the mecA gene coding for resistance to the antibiotic methicillin and is the only known way for Staphylococcus strains to spread the gene in the wild by horizontal gene transfer. [1]
The mecA gene, which confers resistance to a number of antibiotics, is always present in MRSA and usually absent in MSSA; however, in some instances, the mecA gene is present in MSSA but is not expressed. Polymerase chain reaction (PCR) testing is the most precise method for identifying MRSA strains. Specialized culture media have been ...
It also served a purpose in the laboratory to determine the antibiotic sensitivity of Staphylococcus aureus to other penicillins facing β-lactam resistance; this role has now been passed on to other penicillins, namely cloxacillin, as well as genetic testing for the presence of mecA gene by PCR. [citation needed]
Meca or MECA may refer to: Biology. mecA, responsible for methicillin resistance in MRSA; Meca, a snout moth genus in the subfamily Pyralinae; Places Meca ...
Molecular methods, like MALDI-TOF [24] and qPCR primers, [25] are the gold standard for accurately identifying the presence of the mecA gene, which confers resistance to beta-lactam drugs. However, methicillin resistance can still be identified reliably using biochemical or phenotypic methods, such as disc diffusion.
Genetic testing, such as via polymerase chain reaction (PCR), DNA microarray, and loop-mediated isothermal amplification, may be used to detect whether bacteria possess genes which confer antibiotic resistance. [9] [23] An example is the use of PCR to detect the mecA gene for beta-lactam resistant Staphylococcus aureus. [9]
Antibiotic resistance can be introduced artificially into a microorganism through laboratory protocols, sometimes used as a selectable marker to examine the mechanisms of gene transfer or to identify individuals that absorbed a piece of DNA that included the resistance gene and another gene of interest. [162]
This resistance mechanism underscores the importance of the structural integrity of the β-lactam ring for the antibiotic's function. [24] The color change from colorless or light yellow to amber or even red in an aqueous solution of a β-lactam antibiotic can denote β-lactamase hydrolysis of amide bonds in the β-lactam ring.