How does MRSA reproduce?
The only way someone can be infected with MRSA is if it gets through the natural defense systems in the human skin. This is either by someone who has a weak immune system that allows it to pass into the body, or by invasive surgery or injury where the skin is penetrated, leaving an open wound for the MRSA to enter the blood stream. Either of these two ways will result in the MRSA bacteria entering the circulatory system. When in the circulatory system the bacteria reproduces within itself (asexual reproduction). It does so by binary fission, where the DNA in the cell replicates and both of the copies attach themselves to the cell membrane (As MRSA is a prokaryote it lacks a nucleus). After that the cells cytoplasm is pulled into two whilst trying to encirculate both of the newly produced seperate DNA molecules. The bacteria then grows to twice its original size before a cell wall begins to form between the two sets of DNA, dividing the original cell into two separate cells (3). This process is called cytokinesis, and takes approximately 20 minuates to occour. Both of the newly reproduced MRSA bacteria then repeat this process, causing 4 overall bacteria, then 8, and so on. Here is a diagram that demonstrates this:
(2)
Why is MRSA resistant to most antibiotics?
The way MRSA reproduces is closely linked with its capability of developing resistance to antibiotics. Prokaryotes, such as MRSA have high mutation rates (4). These mutations are caused by errors in the the reproduction of DNA in prokaryotic cells. It is a very rapid form of natural selection, where the strains of bacteria that are immune to antibiotics tend to survive and continue to reproduce yet more immune bacterium, whilst the bacteria that develop mutations which decrease their immunity are therefore destroyed by antibiotics and the weak bacteria are never able to reproduce again. This, unfortunately for the animal kingdom, leaves only the immune bacteria which will continue to thrive and reproduce until there is a strong population of it. This process is illustrated on the diagram to the left. Therefore a new antibiotic is required to combat the new strain of it. This rapid rate of mutation is what makes MRSA capable of developing a resistance to most antibiotics, helping them to exploit a large variation of environments. Experts have so far descovered 17 different strains of MRSA, with a range of immunity to the effects of various antibiotics. Two particular strains, “EMRSA15” and “EMRSA16”, are thought to be more transmissible than the others, and account for 96 per cent of MRSA bloodstream infections in the UK (11).
(3)
How do antibiotics work?
If the MRSA bacteria does make it past the immune systems and start reproducing inside the body, it is dangerous as the bacteria produce chemicals that can damage or disable parts of the body. This is where antibiotics come into use. Antibiotics usually work by preventing the cell walls of the bacteria from fully developing, therefore preventing it from reproducing. There are Different type of antibiotics, however affect bacteria in different ways. For example, an antibiotic might also inhibit the ability of a bacteria to turn glucose into energy, therefore preventing the stage of reproduction where a MRSA bacteria expands to about twice its original size, before splitting into two separate bacteria. When enough of the MRSA bacteria are desroyed, the immune system is able to recover and destroy the remaining few. However, antibiotics do not destoy because viruses are not live bacteria. They carry DNA, which is injected into a living cell and uses that cell as a “host” to reproduce more of the infective viruses. (13)
How can we prevent MRSA?
As I explained on page 2, only a few antibiotics can kill MRSA, and the rate of mutation of MRSA is so high that immune strains of the bacteria are formed. This causes the current antibiotic to be rendered “useless” and there is a requirement for new antibiotics that can destroy the MRSA. Another method of prevention is through good personal hygeine. Some general tips are; Try not to share personal items like towels or razors, as this will increase the chance of spreading MRSA. Wash your hands thoroughly with soap and water or an alcohol-based hand sanitizer to destroy the bacteria. Cover cuts and scrapes with a clean bandage. This will help the wound heal, as well as preventing you from spreading bacteria to other people. Try not to touch other people's wounds or bandages. If you use any shared equipment, sanitize it before and after you use it. By looking at this advice, it soon becomes clear why there are so many incidents of MRSA inside hospitals, due to the requirement to share and reuse things.
How does MRSA harm someone?
Bacteria, such as MRSA, have the ability to produce harmfull chemicals (generally known as toxins) that can damage or disable parts and functions of the body. When the MRSA bacteria is in the circulatory system and is not reproducing it will be producing toxins. The general strategy of the bacteria is to break down the immune system, allowing it to reproduce quickly and efficiently. There are 4 main groups of toxins manufactured by various strains of MRSA that can be distinguished by the symptoms they create. These are:
- Anthrax Edema Toxins: These toxins are specialized in damaging phagocytes. This greatly reduces the amount of phagocytes attaching to the MRSA, therfore reducing the amount of MRSA that become engulfed and digested by white blood cells. Therefore these toxins create a bipass for the MRSA not to be destroyed by the bodies immune system, causing the reproduction rate to increase (9).
- Super-Antigens: These chemical toxins over stimulate the immune system, causing TSS (toxic shock syndrome). Despite the fact that this type of toxin is uncommon, it is usually fatal due to its ability to cause the immune system to break down, allowing all other types of bacteraemia, viruses and fungi to enter the circulatory system, causing almost certain death.
- Exfoliative Toxins: Effect the staphylococci in skin cells and cause them to produce a poison that causes damage to the skin. When the damaged skin falls off the circulatory system becomes exposed to additional bacteraemia, viruses or fungi (although unlike TSS the affect Is limited to a much smaller surface area of skin).
- PVL (Panton-Valentine leukocidin): Is a toxin that damages the skin by creating pores in the membranes of infected cells. This causes them to function less effectively, causing pneumonia (5).
What are the symptoms of MRSA?
The usual symptom is inflamed skin, or sore wounds. However singhs can also come in the form of general weakness, lack of energy, slow heart rate, coldness/shivering and lack of immunity. Sometimes, people may carry MRSA without having any symptoms (11). MRSA can also cause multiple infections, by exposing the immune system, allowing additional bacteria, viruses and fungi to enter the body. This causes the blood to enter a stage of bacteraemia, where multiple bacteria strains develop and multiply, causing a harder to treat illness (12). MRSA can also cause pneumonia, meningitis, endocarditis and septicemia.
MRSA in hospitals
MRSA is paticularly common in hospitals because in most hospitals people are in close proximity to each other. This increases the rate of the MRSA being transfered to other patients, through dust paricles in the air, or on cloth, ect. However, by keeping patients in separate rooms the risk of it spreading is lowered. Hospitals offer many opportunities for MRSA bacteria to encounter a wide range of antibiotics and, through genetic change and survival, develop resistance to more of them. According to the seattle times, the number of cases of MRSA in hospital have rapidly increased from 1997 to 2007 (in America)(15).
(4)
Arguments against going to hospital due to the outbreak of MRSA
There are some people who think that the benefits of hospitals are too outweighed by the dangers of MRSA. They may think this because:
1. Approximately 18,650 Americans died of MRSA in 2005. Due to the fact that about 85% of invasive MRSA infections were associated with healthcare, hospital may cause more danger than benefits (8).
2. There is a strong positive correlation in the number of case of hospital patients with MRSA from 1997 to 2007 (15). “Each year, at least 100,000 people who go into hospital get an infection there” - Dr Jeni Worden (11)
Arguments In favor of going to hospital despite the outbreak of MRSA
There are some people who think that the benefits of hospitals outweigh the dangers of MRSA. They may think this because:
1. In 2005 approximately 18,650 Americans died during a hospital stay related to MRSA infections (8). The average hospital death toll for preventable infections (such as MRSA) America from 2000-2002 was about 195,000 (7). So as a rough estimate from 2000-2005 about 0.1% of preventable deaths from infections in hospitals are caused by MRSA. That is only 1 in 1000 cases and is not high enough for too much concern.
2. Recent evidence shows a recent reduction in MRSA cases, as from 2007 to 2008 (14). The number of death certificates in England and Wales which mentioned Meticillin-Resistant Staphylococcus Aureus in them decreased by 37% in 2009 to 781 from 1,230 in 2008. This 37% decrease is probibly due to raised awareness in general hygeine. This means it is becoming less common, and therefore there is a even lower risk of conceding MRSA at a hospital.
3. “There were 836 cases of MRSA infections in April to June of 2008, a 36% drop on the same period in 2007, and a 57% reduction since April to June 2004” - The Health Protection Agency. This evidence improves people’s generall confidence in hospitals, decreasing the dangers on to benefits dangers ratio.
Evaluation of the evidence
My evaluation of this
Conclusion
After evaluating the evidence and refering to the original question “Is going to hospital too much of a risk due to the outbreak of MRSA?” I conclude that hospitals are not too much of a risk despite the outbreak of MRSA. This is because in the evidence section, the benefits of hospitals continuously outweighed the dangers of MRSA. There are only about 1 in 1000 preventable deaths in hospitals are caused by MRSA, concluding that about 99.9% of preventable deaths in hospitals are not caused by MRSA.
Alternative Conclusion
Bibliography
I used information from a variety of sources (internet, OCR GCSE Science Higher Text Book section B2, and non-fictional books) to get a wider spread of data. I had to discredit some sources of information due to the lack of reliability from these resources. A lack of reliabilty may cause an inaccurate conclusion, so I did not use them.
Website References:
(1) tinyurl.com/4yaucmj - The Independent Online – 23/05/08 - James
(2) oxfordradcliffe.nhs.uk//infection_control/mrsa.aspx - ??/01/09 - Oxford Radcliffe Hospitals NHS Trust 2011 – This is a very reliable resource as it is provided by the NHS, which have strict rules regarding the accuracy and of their information.
(3) freewebs.com//
(4) daviddarling.info/encyclopedia/B/binary_fission.html
(5) evolutionguide.blogspot.com/2010_07_01_archive.html – 01/07/10 -
(About half way down the page).
(6) EzineArticles.com/2597805
(7) medicalnewstoday.com/articles/11856.php
(8) cdc.gov//library/index.html
(10) newscientist.com/blogs/nstv/2011/04/copper-wins-out-in-live-battle-against-mrsa.html
(11) bbc.co.uk/health/physical_health/conditions/mrsa.shtml
(12)cqc.org.uk/guidanceforprofessionals/nhstrusts/annualassessments/annualhealthcheck2008/09/qualityofserv/incidenceofmrsabacteraemia.cfm
(13) health.howstuffworks.com/medicine/medication/question88.htm
(14) statistics.gov.uk/cci/nugget.asp?id=1067
(15) scienceblogs.com/digitalbio/2008/11/the_seattle_times_takes_on_hos.php
(16) news.bbc.co.uk/1/hi/7622594.stm
Book References:
(9) Pathogenesis of Bacterial Infections in Animals – Carlton L.Gyles – 2010 - P.97/98
(x) Textbook Reference: OCR GCSE Science Higher Text Book - 2009
Image References:
(1) tinyurl.com/4yaucmj
(2) + (3) tinyurl.com/pathogens78
(4) scienceblogs.com/digitalbio/2008/11/the_seattle_times_takes_on_hos.php
(5) statistics.gov.uk/cci/nugget.asp?id=1067
