Nosocomial Staph Infections
Staphylococcal infections are communicable conditions caused by specific bacteria. Infections from Staphlococcus frequently cause the formation of abscesses. Staph is the leading cause of nosocomial (hospital-acquired) infections in the United States. Staph exists on the skin and/or in the nostrils of 20-30% of healthy people. It is also sometimes found in the breast tissue, the mouth, and also in the genital, urinary, and upper respiratory tracts. Some people carry Staph in throat, vagina, or rectum without ever becoming ill. Staph is normally harmless, but when it gets in the bloodstream through a break in the skin it can cause serious infections and even death. The risk of staph infection is highest in newborns, women who are breastfeeding, intravenous drug users, people with surgical incisions, skin disorders, or people with serious illnesses such as cancer, diabetes, or lung disease. Also, people with compromised immune systems, trauma and burn patients, patients that receive an implanted medical device or prosthetic, long term care patients, kidney dialysis patients, and patients undergoing invasive outpatient procedures are at high risk for an infection. Staphylococcus aureus is gram positive (stains purple to blue on gram stain), forms clusters, is hemolytic (causes lysis of RBCs) on blood agar, and forms yellow colonies on rich media. It is also a facultative anaerobe, which means it can use oxygen (aerobic respiration) or fermentation (yielding lactic acid) to make ATP. S. aureus is oxidase negative which means that it shows negative results on a BBL Dryslide Oxidase test which detects the presence of cytochromes. It can grow at temperatures of 15-45 degrees Celsius. S. aureus is also catalase positive, or it produces catalase which breaks down hydrogen peroxide to water and oxygen. It is non-motile, non-sporeforming, and ferments glucose with the production of lactic acid. S. aureus is coagulase positive-coagulase is an extracellular protein that converts fibrinogen to fibrin, which is involved in blood clotting. It is found in the normal flora of nasal passages, skin, and mucous membranes, without causing ill effects. S. aureus can also cause food poisoning. There are many manifestations of Staph infections. Infections produce pus-filled pockets (abscesses) below the surface of the skin or deep within the body. Abscesses usually burst and the pus that gets on the skin can cause new infections. A localized infection usually consists of a ring of dead or dying white blood cells and bacteria. The skin above the infection usually feels warm to the touch. Part of a localized Staph infection can enter the bloodstream. In children, these invasive infections affect the ends of long bones of the arms and legs, which can cause osteomyelitis, or an infection of the bone or bone marrow. In adults, invasive infections can cause abscesses of the brain, kidneys, heart, liver, lungs and spleen. MRSA stands for methicillin-resistant Staphylococcus aureus. MRSA is resistant to antibiotics called beta-lactams. A beta-lactam is a cyclic amide that inhibits cell wall synthesis of bacteria, and the resistance from MRSA comes from its production of beta lactamase, an enzyme that breaks down beta-lactams. Other beta-lactams include oxacillin, amoxicillin, penicillin, cephalosporins, carbapenems, and monobactams. Only about 1% of people are actually colonized with MRSA. People with potential or active bloodstream infections are treated with Vancomycin, Linezolid, or Daptomycin. There are a few types of infections caused by MRSA. MRSA is most prevalent in hospitals and other healthcare settings. Surgical wound infections, urinary tract infections, bloodstream infections, and pneumonia are most common. These infections seriously increase costs and mortality rates in hospitals. In 2005, hospital studies show that MRSA occurred in nearly one percent of all hospital stays....
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