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Running head: METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) Methicillin-Resistant Staphylococcus Aureus (MSRA) Name Date 1 METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 2 TABLE OF CONTENTS Content Page no Introduction 3-4 History 4-5 Transmission 5-7 Predisposing factors 7-9 Causes 10-11 Symptoms 11-14 Diagnosis 15-16 Prevention and control 16-19 Treatment and cure 19-20 Recent research on MRSA References 20 21-22 METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) Introduction The (MRSA) Methicillin-Resistant Staphylococcus aureus is a microorganism specifically a bacterium; which is responsible for several departures from the body’s physiological function. The bacterium is also referred to as (ORSA) Oxacillin-Resistant Staphylococcus aureus (Carferkey, 1992). Any strain of bacteria Staphylococcus aureus that has through the process of resistance and natural selection developed is known as MRSA. According to Zimmerli, the strains are resistant to Penicillins such as Dicloxacillin, Oxacillin, Methicillin and Nafcillin; the bacteria are also resistant to cephalosporin antibiotics. Staphylococcus aureus that is not resistant to these antibiotic drugs is referred to as (MSSA) Methicillin-Sensitive Staphylococcus aureus. The resistance of such strains of bacteria does not render them to be highly infectious than the rest of the strains of Staphylococcus aureus; which are not resistant to drugs (Mendez, 2013). The resistance only makes the Methicillin-Resistant Staphylococcus aureus infections more cumbersome to treat; they with standard antibiotics and thus more perilous. The infections are very common in populated areas such as prisons, maternity, and other health care institutions where people have weak body immunity than in unpopulated areas and 3 METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 4 therefore the risk of nosocomial diseases is higher; this is because most of the MRSAs cause infections on the skin. The infections caused by MRSA vary in intensity from mild skin infection such as a boil or a sore to severe infections in the skin, surgical wounds, lungs, urinary tract infection, and or infection in the blood stream (Carferkey, 1992). The infections can also be acquired from livestock. MRSA image For healthy people, the bacteria may reside in the nose and on their skin, without causing an infection. They are though the most common causes of nosocomial diseases; infections acquired from the hospital or health care institutions (Rohde, 2011). The beddings and the rings around staircases are the primary carriers of these bacteria in the hospitals; whenever patients come into contact with the bacteria by holding the ring on the stairs or sleep on or under sheets or blankets that carry the MRSA, they get infected. History According to Mendez, the bacterium was discovered in the 1880s when Staphylococcus aureus infections were very common; they caused skin conditions that were either painful or soft. These included scalded skin syndrome, impetigo, and boils. Other dangerous conditions resulting from the bacteria Staphylococcus aureus include bacteria in the blood stream of an individual, METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) pneumonia and food poisoning caused by Staphylococcus aureus bacteria found in improperly cooked food or poorly stored food. The diseases were very common during this era. Increased conditions caused by Staphylococcus aureus led to discovery and invention of antibiotic drugs in the 1940s, which included penicillin. Overuse and misuse of the antibiotics helped bacteria to evolve naturally becoming resistant to the antibiotics (Mendez, 2013). The Staphylococcus aureus changed, and penicillin was unable to treat the infections it caused, leading to the introduction of methicillin that aimed at countering the increased cases of penicillin-resistance by S.aureus. The drug was efficient and very standard in the treatment of infections caused by the Staphylococcus aureus till 1961 when a scientist from Britain came across the first strain of Staphylococcus aureus a bacterium that was not treatable with Methicillin; this marked the birth of Methicillin-Resistant Staphylococcus aureus. In the U.S, the first case was reported in 1968; new strains of staphylococcus aureus have developed subsequently and are resistant to methicillin and antibiotics that are closely related to methicillin (Carferkey, 1992). Transmission The infections by these Staphylococcus aureus can be transmitted through several ways: 5 METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 6 Nosocomial diseases The methicillin-resistant Staphylococcus can infect individuals in healthcare institutions or the hospitals. Health Care-MRSAs are the most common; it can be patient-patient, patientvisitor, or patient-provider (Rohde, 2011). The healthcare providers are at a higher risk of contracting the infections especially if they do not necessarily wash their hands; after attending to a patient and before attending to the next patient. According to Cafferkey, inpatients admitted to the hospital and outpatients visiting the hospital obtain these infections from the beddings and other hospital facilities; such as toilets and rings on the hospital pavements. A person comes into skin contact with surfaces where a patient with MRSA infection had previously contaminated, and he or she also gets infected with the MRSA. Patients in the burn section are even at a higher risk and require a lot of care to prevent them from contracting these resistant bacteria; they are very vulnerable due to the wounds on their bodies (Zimmerli, 2009). Community-based transmission Crowded environs such as prisons, military camps or barracks, and children’s home are areas where the chances of infections by MRSA are high. Cases of such infections were first reported in America and are still witnessed currently. There are high chances that people in theses environs do not observe hygiene and thus, risk of contracting the infections are very high (Mendez, 2013). METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 7 Due to crowding, the bacteria spread very quickly causing infections to the inhabitants of the area. The bacteria are known to reside in the nose or on the skin; the moment an individual is wounded, they will be infected and pass the Staphylococcus aureus to most of their inmates, families and or colleagues. This form of transmission also involves athletes and students who contract the MRSAs from lockers, desks, and doors; they obtain the bacteria immediately they come to contact with infected surfaces on the cabinets, door knobs, and desks (Carferkey, 1992). Livestock transmission Livestock also transmits a type of MRSA, which is most often asymptomatic in animals producing food i.e. meat and milk products. The strain though does not affect animals is dangerous to human beings. The Staphylococcus aureus bacteria are transmitted to humans when they eat insufficiently cooked meat, milk and dairy products that are not pasteurized, and or improperly boiled or unfrozen milk or meat. In this case, the livestock is the intermediate host while human beings are the definitive host (Rohde, 2011). Predisposing Factors Several factors expose individuals to the Methicillin-Resistant Staphylococcus aureus: 1. Age factor The elderly and infant children are at a higher risk of contracting infections caused by MRSA; this is because of their developing immunity (for infant children), and the depressed immunity resulting from reduced body activities due to age (for elderly or the aged). The poor protection from diseases in the two age groups (infant and the old) renders the individuals more METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 8 susceptible to Methicillin-Resistant Staphylococcus aureus bacterial infections. Middle-aged and mature youths have stronger immunity than the aged and the infant, and they are at a relatively lower risk of contracting the diseases (Mendez, 2013). 2. Underlying diseases An individual with diseases like HIV, anemia, hypertension, TB, and other underlying diseases will contract MRSA infections easily compared to a healthy person when the two are exposed to these infections. The exposure is due to lowered immunity by the underlying diseases; individuals with HIV are weak in immunity, and they are prone to most infections. Any departure (physiological) of the body from its normal functioning will interfere with an individual’s immunity; the Methicillin-Resistant Staphylococcus aureus will, therefore, have fewer difficulties causing an infection, because the body does not fight back effectively. Diseases will, therefore, render the body cells very susceptible to infection by MRSA (Carferkey, 1992). 3. Skin break or wounds People with wounds such as surgical or traumatic wounds, intravenous lines on hospital patients, body piercing, burns, tattoos, or ulcers on the skin are at risk of contracting MRSA infections. Simply because most of these infections are skin infections; they enter the body through abrasions or openings on the human skin, causing either mild or severe conditions (Rohde, 2011). The MRSA can reside on the skin or in the nose of an individual harmlessly; without causing any infection (Etinger, 2009). The moment they penetrate through the skin into the body, which in most cases will only happen through a wound; they cause infections in different parts of METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 9 the body. These include the bloodstream, the urinary tract, and or the skin itself; where a patient has sores, boils and other more severe forms of skin infections. 4. Medication Individuals under medication, especially use of antibiotics are at a greater risk of having Methicillin-Resistant Staphylococcus aureus. General use of antibiotics whether proper use, misuse or underuse may expose one to resistant strains of bacteria (Mendez, 2013). Bacteria that survive the attack by antibiotics tend to evolve or mutate forming resistant strains of the bacteria. Staphylococcus aureus that survives medication of beta-lactam antibiotics will lead to Methicillin-Resistant Staphylococcus aureus infections. 5. Hospital environment According to Estinger, both individuals working in the hospital and those visiting the inpatients are at risk of contracting Methicillin-Resistant Staphylococcus aureus; most of the MRSA are nosocomial diseases. People should take precaution such as washing their hands and avoiding direct contact with patients’ wounds. They should also avoid contact with objects that may be contaminated with the bacteria such as the pavement rings in the hospital. Patients admitted to hospitals for a long time are at a greater risk of contracting the methicillin-Resistant Staphylococcus aureus, their weak immunity and exposure to an environment with the causatives of these infections increases their risk of contracting the diseases (Rohde, 2011). METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 10 Causes of MRSA infections a. Overuse or misuse of antibiotic drugs Patients who have recently overused or misused antibiotics; taking under-dose, overdose or late dosage may render Methicillin-Sensitive Staphylococcus aureus bacteria to turn resistant; meaning that bacteria whose infection could have been treated using beta-lactam antibiotics, becomes resistant to these antibiotics causing MRSA. The patient then transmits the bacteria to other individuals through the several transmission methods discussed (Carferkey, 1992). b. Insufficiently cooked or unfrozen food Certain forms of MRSA referred to as Livestock-associated MRSA are transmitted by eating meat from livestock i.e. pigs, cattle and or poultry, which is not sufficiently cooked. Drinking unpasteurized milk and dairy products such as cheese obtained from animals with the resistant Staphylococcus aureus bacteria (Kolendi, 2010). The MRSA are asymptomatic in livestock but very dangerous to human; they are cumbersome to treat. These forms of infection can be prevented by sufficiently cooking meat, boiling milk, freezing and or taking pasteurized dairy products. c. Naturally occurring (Garden variety) Methicillin-Resistant Staphylococcus aureus A third of the world’s population has these bacteria in their noses or on their skin. The condition of having the Staphylococcus aureus bacteria on the skin or in the nose, which does not cause an infection, is referred to as being colonized by the bacteria. The condition turns fatal and peril when the bacteria enter the body through a wound on the skin; causing a departure from the METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 11 body’s physiological functioning; either on the skin, bloodstream or in the urinary tract (Mendez, 2013). d. Transmission from infected persons Individuals can contract infections caused by Methicillin-Resistant Staphylococcus aureus from suffering patients through contact with their wounds; the bacteria then enters the body of these people causing infections (Kolendi, 2010). Physicians attending to MRSA patients in the hospital may also contract the diseases if they come into contact with the wounds or droplets from the patient’s body; therefore, people handing or visiting these patients should wear protective gears to avoid contracting the disease. Signs and symptoms of MRSA The signs and symptoms of MRSA depend on the affected body part; different parts of the body might have a varying range of symptoms. The infections also vary in intensity causing different symptoms at various stages of the MRSA infection. On skin and soft tissue On the upper layer of the skin, the methicillin-resistant Staphylococcus aureus may show the following symptoms during its early stages of infection: a) Boils When an individual is infected with Methicillin-Resistant Staphylococcus aureus, furuncles can develop on his or her skin. The boils form at any place on the skin but are most likely to develop at infection site; they affect the hair follicle resulting in an infection full of pus on the follicle. These in most cases develop on areas where hair, sweat and friction combine; the METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 12 conflict leads to wearing of the skin surface resulting in an opening that allows entry of the resistant staphylococcus bacteria (Mendez, 2013). According to Espinosa, the boils may grow big in size and become more painful; this is due to the accumulation of pus which over time bursts out and drains away leaving no scar. Several boils may crowd together forming a dome shaped infection, which in most cases will occur at the back of the thighs or the neck. b) Abscesses Abscess refers to an infection (pus collection) under the skin which results from the death of tissues as the white blood cells attack the resistant Staphylococcus aureus bacteria. A hole, which fills with pus (a mixture of leucocytes, dead tissues, and bacteria) forms; it is seen as a swelling under the skin (Carferkey, 1992). METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) c) 13 Rash A rash refers to areas that are red, irritated and inflamed on the skin surface. d) Impetigo Impetigo, a very contagious skin infection; very common on the neck, hands and face of infants and young children, caused by Staphylococcus aureus and for this case the MRSA. Other symptoms which are also associated with the skin but the deeper layer of the skin include: • Sty Sty refers to a bump, which develops on or in the lid of the eye due to blockage of the glands (Kolendi, 2010). There is swelling, watering of the eye, light sensitivity and pain or discomfort when the eye blinks. • Cellulitis The symptom can be observed on any part of the body, but most often affect the legs. The area turns red, swells, experience high temperature, and becomes very painful. The pain and METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 14 swelling are due to dying tissues as the cells of the blood (leukocytes) fight the MethicillinResistant Staphylococcus aureus bacteria (Mendez, 2013). During late stages or when the MRSA bacteria infect internal body organs, it may cause other more perilous conditions in the body; the following symptoms may be experienced or observed. Rise in temperature A general feeling of unwell Confusion Pain in the muscles Giddiness Swelling, and tenderness in the affected part of the body Chills-a sudden penetrating sense of cold More severe conditions caused on or in internal organs may include lung infection (pneumonia), infection of the valves of the heart (endocarditis), and septic bursitis. Others include infection of the tube that passes urine (UTI), bone infection (osteomyelitis), joint infection (septic arthritis), and blood poisoning which would cause septic shock. The pressure of METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 15 the blood dropping to perilously low level is also a complication that may be caused by MRSA (Kolendi, 2010). Diagnosis of MRSA infections Individuals who suspect that they have diseases that are related to MRSA bacteria should immediately visit and seek the help of a physician. The physician may choose to use any of the following methods or may even combine several to determine whether an individual is suffering from MRSA infections (Mendez, 2013). i) Physical examination The doctor before conducting any tests in the laboratory will examine the skin of an individual, to check for any changes, which may have resulted from infection by the MRSA bacteria. ii) Patients history The physician requires a patient to report chances of previous bacterial infections, and treatment administered, or any exposure to MRSA bacteria such as contact with a wounded person suffering from MRSA infections (Espinoza, 2008). The history helps the doctor to weigh chances of infections by Methicillin-Resistant Staphylococcus aureus; this helps him or her narrow down to the possible cause of the disease; the physician therefore knows what to test in the laboratory. iii) Culturing of biopsy material or body fluid sample Blood, urine, a sample from the skin, pus sample, or tissue sample is cultured to check for Staphylococcus aureus. The sample is placed on a growth media, and if Staphylococcus aureus is METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 16 isolated, the bacteria are exposed to antibiotics (Carferkey, 1992). Bacteria whose growth is not inhibited by the antibiotics (methicillin) are referred to as MRSA. The patient whose test sample had been cultured is, in this case, termed MRSA infected; the doctor thus administers treatment to this patient. In case the bacteria are inhibited by the action of the antibiotic (methicillin), the doctor proceeds to test for other diseases that would have the same symptoms; because the patient has no MRSA. The bacteria, in this case, are said to be MSSA Methicillin-Sensitive Staphylococcus aureus (Etinger, 2009). Prevention and control of MRSA 1. Screening of patients According to Estinger, most of the MRSA infections are obtained in the hospital; the cases of infection can be reduced through screening of patients before admission. The screening will reduce the chances of Methicillin-resistant Staphylococcus aureus in the nursing rooms or wards; the infected patients should be treated before they contaminate the wards where other patients will get the bacteria. 2. Use of protective gears for people working in areas with Staphylococcus aureus Employees working in hospitals, prisons, and other healthcare institutions should use masks when entering the areas with people isolated due to MRSA. The individuals should also use gloves and avoid contact with body fluids of infected patients or persons (Espinoza, 2008). The Methicillin-Resistant Staphylococcus aureus is transmitted through contact with fluid or METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 17 droplets from infected individuals; contact with their wounds, pus and urine on open skin or cuts will contract the MRSA bacteria. 3. Covering wounds, cuts, burns, or abrasions on the skin According to Weinstein, the MRSA bacteria have been known to reside on the skin of human body harmlessly but the moment there is a wound or an opening on the skin, the bacteria enter the body causing an infection. Covering of wounds reduce the MRSA infections, as they will in most cases require an injury to enter the human body. 4. Observing proper hygiene As the transmission of these diseases relies on contact, wash the hands after a long day of interaction with people, visiting the hospital, visiting the toilet and using other resources such as escalators and elevators. Most people will hold the resources with contaminated hands, and other people will keep contracting the MRSA bacteria from there (Mendez, 2013). Washing hands with soap, which is a disinfectant, kills the staphylococcus bacteria reducing chances of infection. 5. Sanitization of surfaces in hospitals METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 18 Most surfaces in the hospital environment are likely to be contaminated with Staphylococcus aureus bacteria. The bacteria can be found in the human skin including the hands, and anytime a person holds the ring around the pavement, door knobs, presses a button on the lift or holds the handle on the escalator, he or she contaminate that surface (Weinstein, 2002). The laboratory is another place where the Staphylococcus may be found due to the patient samples brought in containing these bacteria. Sanitization of these surfaces by use of disinfectants reduces the MRSA infections. 6. Proper cooking of meat and milk from livestock Fully cooking meat will reduce infections by MRSA that are associated with the animal. Sufficiently cooking meat, adequate pasteurization of milk and dairy products, and efficient freezing of meat at -10 degrees to kill staphylococcus aureus bacteria present in the meat (Mendez, 2013); are practices that can save people from MRSA. 7. Treatment and isolation of infected persons As the infections are easily transmitted in a community, infected people should be treated to avoid infecting other people in the society. Infected individuals should be isolated from the rest of the community till they have recovered from these infections; if allowed to interact with other members of the community, they may end up infecting them with the MRSA (Weinstein, 2002). 8. Creating public awareness Creating awareness will reduce the deaths and complications resulting from MRSA infections; most people observe symptoms of the MRSA infections, but because the infections METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 19 are very mild especially in their early stages, they ignore till they experience severe complications (Carferkey, 1992). Awareness will, therefore, help people to seek diagnosis early enough and get treated; the infections are treatable especially in their early stages. 9. Controlling the use of antibiotics and other medications Use of antibiotics whether proper or misuse may result in certain bacteria developing resistance to antibiotics. Once the bacteria survive an attack by an antibiotic, they develop resistance to that type of bacteria. Treatment of MRSA infections Methicillin-Resistant Staphylococcus aureus infections treatment is generally by use of antibiotics. The bacteria are beta-lactam antibiotics resistant (traditional antibiotics), and they require more advanced antibiotics to treat. The hospital-acquired or nosocomial Methicillin-Resistant Staphylococcus aureus bacteria are resistant to a very wide range of antibiotics and only susceptible to an antibiotic known as Vancomycin (Mendez, 2013). Other antibiotics that can treat the nosocomial MRSA are linezolid, which are newer antibiotics of the class Oxazolidinones, and an antibiotic known as Daptomycin. The drugs recommended for pneumonia caused by MRSA include linezolid, clindamycin, and Vancomycin. MRSA associated with community is treated using several antibiotics as it is also resistant to a variety of antibiotics. These types of MRSA have an antimicrobial susceptibility of a greater spectrum; they can be treated using Tetracyclines, clindamycin, and sulfa drugs, but Vancomycin is the antibiotic that is currently believed to fight or cure MRSA infections METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 20 (Weinstein, 2002). Newer Daptomycin, and Oxazolidinones such as linezolid, are also useful in the treatment of these diseases. Recent research Researchers led by Kim Lewis, who is a professor of biology at the University and a director of an antimicrobial center, realized that the resistant strains of Staphylococcus aureus were evading the action of drugs, by entering a dormant state Mendez, 2013). Which drugs cannot work on as they kill bacteria by targeting active functions of the cell, the antibiotics are rendered useless by the inactive bacteria. According to Rohde, the group deduced that use of a drug that awakens the bacteria (ADEP antibiotic), together with other traditional antibiotics will kill the MRSA. Bacteria that develop resistance towards the ADEP are very susceptible to beta-lactam antibiotics, and this is an important discovery especially now that the utility of antibiotics is diminishing. METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 21 Reference Cafferkey, M. T. (1992). Methicillin-resistant Staphylococcus aureus: Clinical management and laboratory aspects. New York: M. Dekker. Ettinger, S. J., & Feldman, E. C. (2009). Textbook of Veterinary Internal Medicine. London: Elsevier Health Sciences. Espinoza, C., Ostrosky, L., Brown, E. L., Slomka, J., & University of Texas Health Science Center at Houston. (2008). Prevalence and risk factors of methicillin-resistant Staphylococcus aureus in critically-ill hospitalized patients in a tertiary care center in Houston, Texas: An active surveillance pilot project. (Masters Abstracts International, 47-1.) Kolendi, C. L. (2010). Methicillin-resistant Staphylococcus aureus (MRSA): Etiology, at-risk populations and treatment. Hauppauge] N.Y: Nova Science Publishers. Méndez-Vilas, A., & International Conference on Antimicrobial Research. (2013).Worldwide research efforts in the fighting against microbial pathogens: From basic research to technological developments. S. l.: Formatex. Rohde, R. E. (2011). Methicillin resistant Staphylococcus aureus (MRSA): Knowledge, learning, and adaptation : I guess everything changes when it happens to you : their stories. Saarbrücken: LAP Lambert Academic Publishing. Weinstein, R. A., & Bonten, M. J. M. (2002). Infection Control in the ICU Environment. Boston, MA: Springer US. METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) Zimmerli, M. (2009). Methicillin-resistant staphylococcus aureus (MRSA) among dental patients: A problem for infection control in dentistry?. S.l.: s.n. 22 METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) Multiple choice questions 1. What does an immunochromatographic assay do? Uses mouse monoclonal IgG Ab's to Influenza A and/or B nucleoproteins to form a complex w/Influenza A and/or B viral antigens 2. What are 6 infections that Staphylococcal bacteria can cause? (doesn't have to be MRSA--any staph) 1. Toxic shock syndrome 2. Respiratory infection 3.Osteomyelitis 4. Food poisoning 5. Endocarditis 6. Skin infections (abscess, furuncle, carbuncle, impetigo, wounds) 3. 3 things that specifically MRSA causes 1.Skin infection 2. Sepsis 3. Necrotizing pneumonia 4. What is a folliculitis? Pyogenic infection in the hair follicle Called a stye if in the base of the eyelid 5. What is a furuncle? Extension of folliculitis Large, painful, underlying dead and necrotic tissue (abscess) 23 METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) 6. What are carbuncles? Multiple interconnected boils that extend into deeper tissues Fever and chills point to systemic spread 7. 3 types of damage Staph aureus can cause Infection Intoxication Infection and Intoxication 8. Why is Levofloxacin used to treat MRSA? It inhbits DNA gyrase (involved in DNA replication) 9. Why are ceftriaxone, penicillin, and methicillin used to treat MRSA? They inhibit cell wall synthesis in the Staph Aureus 10. Why is Trimethoprim used to treat MRSA? It prevents folic acid synthesis 11. Why are Clarithromycin and Erythromycin used to treat MRSA? What type of antibiotics are they? Macrolides They inhibit protein synthesis, specifically the 50S ribosomal subunit 12. What type of bacteria are Staphylococci? How are they arranged? Gram-positive coci Arranged as grape-like clusters 13. What 2 metabolic characteristics do Staphylococci have? Facultative anaerobes Catalase positive 24 METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) What two things comprise the mecA complex? mecA gene and regulatory elements 14. What are ccr genes and what do they do? They are site specific recombinases They can catalyze precise excision and site and orientation specific integration of SCCmec elements 15. Where are the different places that Staph aureus can cause disease? In every organ system (skin, bone, food poisoning, pneumonia, meningitis, sepsis) 16. Why does Staph aureus cause so many diseases? Because it has a variety of virulence factors 17. Why are different strands of Staph aureus different in causing disease? Not all virulence genes are present or expressed the same in every strain 18. The type of disease caused by Staph aureus depends on what 3 things? Location in the body Environment in the host Virulence factors expressed by the strain 19. What are 6 examples of virulence factors that may play a role in the pathogenesis of staphylococcal infections? Protein A Fibronectin-binding protein Cytolytic exotoxins Enzymes 25 METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) Slime production Superantigen exotoxins 20. What two things does the capsule/slime do to help S. aureus in its pathogenesis? Prevents phagocytosis Promotes adherence to cells and prosthetic devices 21. What two things does Protein A do to help S. aureus in its pathogenesis? Binds Fc terminus of IgG Prevents opsonization and Complement activation (classical) 22. What does the Fibronectin binding protein (teichoic acid) do to help S. aureus in its pathogenesis? Promotes binding to mucosal cells and tissue matrices 26