Global pandemic: Of the Purple Cocci

March 1st 2014

Abstract
Hard to believe that a very common bacterium that is nearly present on everyone’s skin has been the cause of thousands of deaths every year. It has gained virulence that helps it survive a host’s immune system and many common antibiotics. This bacterium produces biofilms and toxins which allows it to survive in a host’s body. This bacterium has increasingly new strains that have evolved genetically. With new genetic strains it because more resistant to many different antibiotics.
Global pandemic: Of the Purple Cocci
Bacteria are living organisms and just like any other living organism, it wants to live and survive, even when it’s trying to be killed. It is this survival instinct that has lead certain bacterial strains to evolve and grow, to become a global pandemic. Methicillin-resistant Staphylococcus aureus or MRSA is a group of bacteria leads to thousands of deaths every year. In order to understand MRSA, you first need to know about the bacteria’s original characteristics, and then you learn about this bacterium’s evolution over the years, and finally learn the current way in which MRSA is treated with antibiotics.
S. aureus is a very common bacterium that lives on or in people; it usually lives on the skin, inside your nostrils, stomach and intestines. Many people are carrying it and are totally unaware that it is colonizing in or on them. Colonization is the establishment and growth of pathogens without causing signs or symptoms of it being there (Lilley, Collins, Harrington & Snyder, 2011, p. 584). S. aureus is normally harmless, however it does cause problems if it is able to enter the body and the body’s immune system is unable to kill it. 82% of patients in a study of bacteremia of S. aureus infections indicated the infections are usually caused by the identical colonizing strains in their nasal cavity (Gordon & Lowy, 2008, p. s350). S. aureus can be spread easily by contact with an infected person or contact with objects, like clothing, dressings, and medical equipment which came into contact with an infected area or person even weeks later.
S. aureus has many different ways of causing severe diseases and has been shown to cause toxic shock syndrome and cause infections of the skin, joints, and heart, all of which if untreated properly can lead to death. According to a 2009 report more than 90,000 life-threatening illnesses and nearly 19,000 deaths associated with MRSA occur yearly in the United States (Jarnagin, 2010).
Every pathogen has its own virulence or capability to cause disease (Tortora, Funke, & Case, 2013, p. G-17). “When S. aureus is able to grow on the tissues it attached to, it can form biofilms, a slime-like substance. It is also able to form small-colony variants (SCVs); SCVs are able to “hide” in host cells without causing significant host-cell damage (Gordon & Lowy, 2008, p. s351).” Both of these characteristics allows S. aureus bacteria to evade host immune system and defenses. These characteristics of S. aureus are the ones known to result in recurring infections and the infections of joints and the heart. S. aureus is able to produce many chemicals, or enzymes, that have their own way of avoiding the immune cells in the host. These numerous chemicals, enable it to invade and destroy host tissues and metastasize to other sites. S. aureus is also capable of producing septic shock by interacting with and activating the host immune system and coagulation pathways (Gordon & Lowy, 2008, p. s350).
MRSA’s beginning starts in the 1940s in Europe when it was discover that S. aureus had made an enzyme called penicillinase which was resistant to the antibiotic penicillin and within a decade this resistant bacteria lead to a pandemic in hospitals and the community (Otto, 2012, p. 1513). Penicillinase is a type of bacterial resistant enzyme, beta-lactamase, can that break the chemical bond between the carbon and nitrogen atoms in the structure of the beta-lactam ring (Lilley et al., 2011, p. 590). Methicillin-resistant S. aureus (MRSA) came about in 1960s after methicillin, a semisynthetic antibiotic, was introduced a hope to overcome the pandemic of penicillin-resistant S. aureus (Otto, 2012, p. 1513). It was discovered not only was this bacteria resistant to Methicillin but also was resistant from the entire class of beta-lactam antibiotics; this high resistance to methicillin is no longer used in the United States (Tortora et al., 2013, p. 568). Beta-lactam antibiotics, including penicillins, cephalosporins, carbapenems, and monobactams, use their beta-lactam ring structure to inhibit the synthesis of the peptidoglycan cell wall of a variety of gram-positive bacteria (Lilley et al., 2011, p. 590). After twenty of MRSA being a pandemic for Europe it became a worldwide pandemic that is still continuous problem today.
Bacteria are able to pick up virulence factors by genetic recombination. Genetic recombination refers to the sharing of genes between to DNA molecules to form new combinations of genes on a chromosome (Tortora et al., 2013, p. 231). Bacteria can pass DNA by contact to other living bacteria or in some cases can pick up the DNA from lysed bacteria. Once bacteria has received the new donated DNA it makes it part of its own and then passes it on every time the chromosomes are duplicated (Tortora et al., 2013, p. 232-233). “Methicillin resistance in staphylococci is due to the acquisition of a mobile genetic element (MGE) called the staphylococcal cassette chromosome mec (SCCmec) which is a DNA fragment (Otto, 2012, p. 1514).” The SCCmec types and the numbers of SCCmec is increasing, all of these have the mecA gene; the mecA gene encodes for the low affinity penicillin-binding protein PBP2a, allowing the beta-lactam antibiotics to be so ineffective to S. aureus (Otto, 2012, p. 1514). With resistance to these antibiotics, the bacteria have been able to continuously grow and clone itself.
Because MRSA is resistant to a number of different commonly used beta-lactam antibiotics, it is harder to treat and there are only a few treatments available. The drug of choice against MRSA is Vancomycin, which is primarily used to treat gram-positive bacteria. Qinuinupristin/dalfopristin is a combination drug is approved for intravenous treatment of complicated skin and skin structure infections caused by S. auerus including MRSA (. Lilley et al., 2011, p. 615). “A new class of antibiotics known as lipopeditdes, binds to the gram-positive cells in a calcium-dependent process and disrupts the cell membrane potential. Daptomycin currently is the only drug of this class used to treat complicated skin and soft tissue infections caused by gram-positive bacteria including MRSA (Lilley et al., 2011, p. 616).” For the skin there is a topical antibiotic called bacitracin used. “Bacitracin inhibits the synthesis of the cell wall; it does this by inferring with the synthesis of the linear strands of peptidoglycan (Tortora et al., 2013, p. 569).”
Over the past seventy years S. aureus has been able to change its genetics, learning how to gain resistance too many antibiotics being used against it. These resistant bacteria stains started in Europe and now are a global pandemic. With new antibiotics coming out and with S. aureus ability to adapt there may be no end to these bacteria’s pandemic effects.