In this episode, I have discussed in detail about the detection and treatment of MRSA infections. The basic traditional microbiology techniques include gram staining, selective media approach, biochemical assay in combination with antimicrobial susceptibility testing. Advanced detection techniques to detect the MRSA is PCR of mecA gene, monoclonal antibody, and bacteriophage-based techniques. I have also discussed the antimicrobial agents effective against MRSA and very importantly how to prevent the MRSA infection.
In basic traditional microbiology, techniques include gram staining, selective media approach, biochemical assay in combination with antimicrobial susceptibility testing. Gram staining of the sample will be performed to check if there is a gram-positive (purple) round-shaped grape-like structure under the microscope.
Further samples will be plated on selective media for staphylococcus. Mannitol salt agar or MSA is a commonly used selective and differential growth medium in microbiology. It encourages the growth of a group of certain bacteria while inhibiting the growth of others.
This medium is important in medical laboratories as one method of distinguishing pathogenic microbes in a short period of time. It contains a high concentration (about 7.5%-10%) of salt (NaCl), making it selective for Gram-positive bacteria (Staphylococcus and Micrococcaceae) since this level of salt is inhibitory to most other bacteria.
It is also a differential medium for mannitol-fermenting staphylococci, containing carbohydrate mannitol and the indicator phenol red, a pH indicator for detecting acid produced by mannitol-fermenting staphylococci. [3] Staphylococcus aureus produces yellow colonies with yellow zones, whereas other coagulase-negative staphylococci produce small pink or red colonies with no color change to the medium
Further using the help of biochemical assay the bacterial genus and species are confirmed. SA is DNase positive, mannitol positive,
And it cause Alpha hemolysis. It is coagulase positive. Rest of the biochemical assays you can see on your computer screen. I will make future presentations on these selected tests and explain the science behind these tests.
After confirmation, the antimicrobial susceptibility testing is performed and the resistance of the bacteria against methicillin antibiotic is confirmed. AST can also tell us about the other antibiotics that can kill the MRSA bacteria and that will be very useful for the physician to prescribe the treatment of the patients.
Another method to detect the MRSA is the PCR of the mecA gene. The polymerase chain reaction is the technique in molecular biology that can detect and identify the bacteria by their DNA so if you have the facility you can directly do the PCR of sample and look for the gene. The mecA gene is a gene found in bacterial cells which allows a bacterium to be resistant to antibiotics such as methicillin, penicillin and other penicillin-like antibiotics
There are monoclonal antibodies based detection of the MRSA where monoclonal antibodies are produced against the MRSA surface proteins and then antibodies bind to the bacteria and provide the signal for the presence of the bacteria. Please watch episode-7 know more about monoclonal antibodies.
Another interesting technique is a bacteriophage-based technique to detect MRSA infection. Bacteriophage cocktail can be used to kill the bacteria and an increase in the bacteriophage population can represent the indirect identification of MRSA.
How to prevent MRSA infections:
• Ways to prevent MRSA infections:
• Wash your hands.
• Keep wounds covered.
• Keep personal items personal.
• Shower after athletic games or practices.
• Don't inject illicit drugs
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Basic Science Series English
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3 авг 2024
