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What Is MRSA? Are We Really in the Post-Antibiotic Age?

Updated on February 5, 2018
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Sherry Haynes is 21 years old, currently pursuing a pharmD. She has a year and a half of experience in clinical and management pharmacy.


Ever heard about antibiotic resistance crisis?

New resistance mechanisms are emerging rapidly leading to a global threat of treatment failure. Most of the drugs are now ineffective making the treatment of various diseases difficult and sometimes impossible. These diseases include pneumonia, gonorrhoea, tuberculosis, blood poisoning and food borne diseases.

History of Emergence of MRSA

When penicillin was first discovered, the bacteria Staphylococcus aureus were susceptible to it and the infections caused by S. aureus were effectively treated. However, after few years S. aureus became resistant to penicillin by producing an enzyme called penicillinase.

In 1959, Methicillin, a modified penicillin became available for treatment at the time penicillin couldn't work anymore. Methicillin was designed in order to resist the Staphylococcus aureus penicillase. Methicillins like other penicillins act by blocking Penicillin binding proteins (PBPs), that are responsible for the construction and maintenance of bacterial cell wall.

Only after about 2 years the first case of Methicillin resistance by Staphylococcus aureus was reported. The resistant strains of S. aureus acquired a protein called PBP2a. This protein was not blocked by Methicillin and could easily replace the functions of other PBPs, helping the S. aureus species survive even in the presence of Methicillin. PBP2a is a protein encoded by the mecA gene which is a characteristic of all Methicillin Resistant Staphylococcus aureus (MRSA).

Presence of PBP2a makes MRSA not only resistant to Methicillin but also to all beta-lactam antibiotics such as Synthetic penicillins, Cephalosporins and Carbapenems. MRSA is now Multi drug resistant (MDR) showing resistance to commonly used antibiotics including Floroquinolones, TetracyclineS, Macrolide, Lincosamides and Aminoglycosides.

Moreover, among the newly approved antibacterial agents such as Quiniprostin, Linezolid, Daptomycin, Tigecycline, Telaracin (a lipoglycopeptide agent) , Ceftcuoline (a new Cephalosporin), resistance to Linezolid, vancomycin, teicoplanim and Daptomycin has already been reported.

Methicillin is thus, no more used. Even in the susceptibility tests it is replaced with oxacillin.

Methicillin Resistant Staphylococcus aureus
Methicillin Resistant Staphylococcus aureus | Source

Community associated-MRSA (CA-MRSA)

It is the occurrence of MRSA infection in individuals who are healthy with no recent hospital exposure.

It is often associated with skin and soft tissue infections.

Many strains of MRSA produce Panton-Valentine leukocidin (PVL), a cytotoxin that is associated with increased virulence.

It is more commonly seen in younger individuals.

Most CA-MRSA strains carry SCCmec type 4 or type 5 gene.

Health Care Associated-MRSA (HA-MRSA)

Occurs on healthcare exposure.

The disease is severe and invasive which include soft tissue and skin infections, blood-stream infections, pneumonia evident in hospitalised patients.

Most HA-MRSA strains carry SCCmec type 2 gene.

Laboratory tests

These tests are usually carried out to investigate the presence of MRSA infection.

  • Broth microdultion test
  • Cefoxitin disk screen test
  • Latex agglutination test for PBP2a

Cutaneous Abscess Caused by MRSA
Cutaneous Abscess Caused by MRSA | Source

Did you ever take an antibiotic for a viral cause?

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Can entering the post-antibiotic era be slowed

Before the introduction of antibiotics for therapeutic use millions of deaths occurred due to minor ailments such as infections.

According to a report Antibiotic resistance threats in the United States, 2013 around 23,000 people die each year in US as a result of antibiotic resistant infections. Moreover 2 million people every year become infected with antibiotic resistant bacteria.

The cause of resistance

The major cause of resistance is overuse and sometimes misuse of antibiotics.

This is called as "irrational use". The factors are responsible for irrational use of antibiotics are.

  • Prescribing antibiotics even before proper diagnosis is done (If the cause is viral, the antibiotic use should be avoided)
  • Prescribing more than needed number of antibiotics
  • Use of antibiotics by patients without prescription from a doctor
  • Improper prophylactic use and inappropriate empirical therapy .

According to a 2015 study which was published in Nature, the global consumption of antibiotics increased by 30% between 2000 and 2010.

Measures to prevent this

  • In 2015, WHO member states involved in a Global Action Plan. Thet plan laid out the solutions and preventivery measures that countries can take to reduce the resistance.
  • CDC is working closely with American hospitals to provide education and guidelines for safe and rational use of antibiotics.
  • National Antimicrobial Monitoring System (NARMS) set up by CDC to monitor the antibiotic resistanthe bacteria in order to know the resistance types and burden of infection which helps in taking further steps by CDC.
  • Many programmes that provide the incentive to encourage the development of many antibiotics.

Pandrug resistance is the resistance to all antibiotics and drugs currently in use. The emergence of the period of pandrug resistance cannot be fearful enough in S. aureus as it's been already cautioned in case of resistance of all Gram negative bacteria in existence.

It is the responsibility of every individual to take an action for the cause of preventing pandrug resistance by making proper use of antibiotics.

Do you think antibiotic resistance can be minimised or brought back to nil again?

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    • RTalloni profile image

      RTalloni 3 weeks ago from the short journey

      Well-written posts like this are extremely useful in creating awareness and finding solutions for this important issue. Good information about antibiotic usage and dangers of overuse is crucial to keep highlighted. I often wonder about whether new attitudes about using antibiotics would develop if people understood their other side-effects.