Musculoskeletal and Skin Infections PDF

MUSCULOSKELETAL and SKIN INFECTIONS * What is a Musculoskeletal Infection? * A musculoskeletal infection is an infection that affects the muscles, bones, joints, or connective tissues. These infections can be caused by bacteria, viruses, fungi, or parasites. * Most musculoskeletal in...

MUSCULOSKELETAL and SKIN INFECTIONS * What is a Musculoskeletal Infection? * A musculoskeletal infection is an infection that affects the muscles, bones, joints, or connective tissues. These infections can be caused by bacteria, viruses, fungi, or parasites. * Most musculoskeletal infections are usually caused by bacteria. Infection in the bones, joints, or muscles may occur at any age  Types of Musculoskeletal Infections Some of the types of musculoskeletal infections include the following: ❖ Septic arthritis: Septic arthritis, also known as infectious arthritis, is a painful infection of the joint. The infection can occur from bacteria that spread through the bloodstream from another area of the body. Septic arthritis can also occur due to a penetrating injury that delivers germs directly into the joint. Infants and older adults are most likely to develop septic arthritis. Knees are most commonly affected, but septic arthritis also can affect hips, shoulders, and other joints. ❖ Aseptic arthritis (Rheumatoid arthritis): Is an autoimmune disease caused by chronic inflammation of the joints or synovial membrane. ❖ Septic bursitis: Septic bursitis is a painful condition that affects the joints. Bursa are fluid-filled sacs that act as a cushion between bones, tendons, joints, and muscles. When these sacs become inflamed due to infection, usually with bacteria, it is called septic bursitis.  Th e pathogenesis of bacterial infections * The pathogenesis of bacterial infection includes initiation of the infectious process and the mechanisms that lead to the development of signs and symptoms of disease. Characteristics of bacteria that are pathogens include Virulence factors. * * Virulence factors : The quantitative ability of an agent to cause disease. Virulent agents cause disease when introduced into the host in small numbers. Virulence involves transmissibility, adherence to host cells, persistence, invasion of host cells and tissues, toxigenicity, and the ability to evade or survive the host’s immune system. * Resistance to antimicrobials and disinfectants can also contribute to virulence , or an organism’s capacity to cause disease.  Symptoms of Musculoskeletal Infections * Some of the common symptoms associated with musculoskeletal infections include: 1. Pain and tenderness 2. Swelling 3. Fever 4. Difficulty moving the limbs 5. Difficulty in weight-bearing 6. Abscess formation  Complications of Musculoskeletal Infections * Some of the common complications associated with musculoskeletal infections include: ❖ Fractures ❖ Arthritis ❖ Growth deformity ❖ Joint dysfunction ❖ Long-term morbidity  Diagnosis of Musculoskeletal Infections * Doctor will conduct a thorough physical examination to carefully observe the areas around the affected limb as well as feel for pain. Further diagnostic tests may also be ordered, such as: * Laboratory tests to check for infection * X-rays to look for changes in the bone * MRI for detailed images of the structures * Ultrasound for detailed images of the soft tissue structures * Bone scan to check the condition of the bones  Treatment for Musculoskeletal Infections * Antibiotics are the first-line of treatment for musculoskeletal infections. Bone infections are normally treated with antibiotics for 4 to 6 weeks, whereas joint and muscle infections are usually treated for 3 weeks. Once the infection is controlled in the hospital, most patients can receive treatment at home with oral antibiotics. * Surgery may be required to remove infected material (pus) from the area of infection. This reduces pressure and inflammation and improves blood flow, which makes it easier for the antibiotics to reach the infected area. During surgery to drain the infection, your surgeon cleans the inside of the tendon sheath to wash away pus and germs and may remove damaged or dead tissue to allow remaining tissue to heal. * In the case of septic arthritis, surgery normally will be required to wash the bacteria out of the joint. * In some cases, septic arthritis may be treated by using a needle to draw the infected fluid out of the joint. * For severe infections, a person may require surgery more than once to completely remove any infection. Campylobacter: Gram –ve comma shape bacilli, slender (0.2 to 0.5 um wide), curved, motile rods , with comma, S, or “gull-wing” shapes , oxidase +ve. V.F: endotoxin and S protein = outer layer(anticomplement, adhesion, and invasion factor). Dis.: C. fetus causes gastroenteritis progressing to septicemia then organs infection(joints). * Yersinia pestis: is a gram-negative, short, oval coccobacilli with rounded ends and convex sides, about 1.5 × 0.7 µm, occurring singly, in short chains or in small groups. In smears stained with Giemsa or methylene blue, it shows bipolar staining (safety pin appearance) with the two ends densely stained and the central area clear. * -LPS (endotoxin activity). * Envelope contains * 1.protein = fraction 1 (anti phagocytic). * 2.V & W antigens (proteins encoded * by plasmid, lack of this plasmid → * A virulent strain used as vaccine). * -Exotoxin (1μg is lethal in mice). Salmonellae: Gram-ve bacilli, non lactose fermenter, oxidase -ve, motile , produce H2 S The bacteria enter via the oral route by contaminated food or drink → produce 3 main types of diseases (enteric or typhoid fever, bacteremia or septicemia or systemic infection & enteritis or enterocolitis). The bacteria enter the lymphatics & bloodstream, the blood carries them to many organs including the intestine →------ bacteria multiply in intestinal lymphoid tissue & excreted in stools. ] Shigellae: Gram –ve bacilli, nonlactose fermenter, nonmotile, no H2 S , oxidase –ve. -causes bacillary dysentery, bacteremia (rare arthritis) -Chlamydia trachomatis: very small organisms, lacks cell wall (iodine stain), obligate intracellular. Dis. : conjunctivitis, ocular trachoma, (arthritis). ❖ Myositis (soft tissue infections): Myositis refers to inflammation of the muscles that can be caused by an infection, injury, or autoimmune disease. There are various types of myositis, the most common being polymyositis and dermatomyositis. Polymyositis : causes muscle weakness, mostly in the muscles nearest to the trunk of the body. Dermatomyositis : causes muscle weakness as well as a skin rash. The main muscles to be affected by myositis are the shoulders, hips, and thighs. ❖ Pyomyositis: is an acute bacterial infection of the skeletal muscle that results in pain and tenderness of the affected muscle and localized abscess formation. ❖ Cellulitis: is a common bacterial infection of the skin and the soft tissues underneath. It occurs when bacteria enter a break in the skin and spreads. It most often affects the skin of the lower legs, although the infection can occur anywhere on your body or face. Without treatment, the infection can spread quickly and may travel to lymph nodes and into the bloodstream leading to a blood infection or permanent damage of lymph vessels. * Abscess: Abscesses are collections of pus in confined tissue spaces, usually caused by a bacterial infection or when germs enter the body through an open wound like a cut. Abscesses can occur in the skin, soft tissue, muscle, or even bones, causing inflammation at the site of infection and a cavity filled with pus. Borrelia burgdorferi: is a bacterial species of the spirochete class of the genus Borrelia. transmitted by tick called Ixodes, cause Lyme Disease -Spiral, highly motile, stained with acid & aniline dyes & by silver impregnation techniques. causes arthritis. -Grows in a complex medium (BSKII medium), seldom used because it takes 6-8 weeks to grow. *Virulence f. : -Have large No. of lipoproteins (Outer Surface Proteins; Osp A-F) → help this organism live in the very different tick & mammalian hosts, and relapsing fever due to antigenic variations (induction of immunopathogenesis).  Fungi * GENERAL PROPERTIES OF FUNGI : * Fungi grow in two basic forms, as yeasts and molds. * Yeast : * the simplest type of fungus is the unicellular budding yeast. Elongation of the cell produces a tubular, thread like structure called hypha. * Hyphae may be septate or non septate. Some hyphae are divided into cells by cross-walls or septa, typically forming at regular intervals during hyphal growth. * Mycelium :A tangled mass of hyphae constitutes the mycelium. Fungi which form mycelia are called molds or filamentous. * Dimorphic fungi: Many fungi pathogenic to man have a yeast form in the host tissue and in vitro at 37°C on enriched media and hyphal (mycelia) form in vitro at 25°C. Examples: Histoplasma capsulatum, Sporothrix schenckii, Blastomyces dermatitidis, Coccidioides immitis, Paracoccidioides brasilie  Coccidioidomycosis The etiological agent is Coccidioides immitis. The infection is endemic in the desert southwestern of US, Maxico and Central and South America. -Approximately 60% of the cases are usually proximately and self-limited respiratory infection. (the infection may become disseminated to meninges ,bone, joint (Desert rheumatism) and skin, dissemination occur most frequently in person with dark skin) - 18 In culture(25C) In tissue (37C)  Histoplasmosis * Histoplasmosis is is a type of fungal infection in lungs. * It is an infection caused by the fungus Histoplasma capsulatum. You get it from breathing in the fungus Histoplasma capsulatum (H. capsulatum). * The fungus lives in the soil in many parts of the world, including the U.S. It’s most commonly found where there are bird or bat droppings (poop) in the soil. * Histoplasmosis often doesn’t cause noticeable symptoms. Rarely, it causes fever, cough and shortness of breath that can go on for a long time or spread to other parts of your body.. It’s estimated that about 75% of adults who live in areas where H. capsulatum is common have been infected before, even if they.never had symptoms  What does histoplasmosis do to body? * The fungus H. capsulatum gets into lungs when you breathe it in from the soil. There, it enters white blood cells and changes from a mold into its infectious form as a yeast, the organism spread widely throughout the body to reticuloendothelial tissues such as liver, spleen, bone marrow and lymph node * M0rphlogical of H. capsulatum in tissue: *. In tissue H. capsulatum occurs as an oval budding yeast inside macrophage.  Treatment * Histoplasmosis is treated with antifungal medications. * Itraconazole. * Amphotericin B (AmB). * Corticosteroids. * If mild symptoms that haven’t gone on for a long time and you’re not at high risk for serious infection, your provider may not treat you right away. Sporothrix schenckii: is a dimorphic fungus that live on vegetation cause sporotrichosis (Gardener’s disease),this fungus is widespread in nature in soil. Infection acquired through trauma (eg. thorn) and is an occupational hazard for people such as farmers and gardeners. A small papule or subcutaneous nodule develop at the site of trauma 1 week to 6 months after inoculation of hyphal fragments, and infection spreads with multiple nodules along the draining lymphatic of extremities. The initial lesion is usually on the extremities but can be found anywhere (children often present in the facial lesions).  Osteomyelitis * Osteomyelitis is an infection and inflammation of the bone or the bone marrow. It can happen if a bacterial or fungal infection enters the bone tissue from the bloodstream, due to injury or surgery. * Around 80 percent of cases develop because of an open wound. Symptoms include deep pain and muscle spasms in the inflammation area, and fever. * Bone infections commonly affect the long bones in the leg and upper arm, the spine, and the pelvis. In the past, it was difficult to treat osteomyelitis, but now, forceful treatment can often save the infected bone and stem the spread of infection. * People who have diabetes may develop osteomyelitis in their feet if they have foot ulcers. Gas gangrene : is a highly lethal infection of soft tissue, caused by Clostridium species, with Clostridium perfringens being the.most common The infection causes toxins to form in the tissues, cells, and blood vessels of the body. These bacteria will release toxins that cause.tissue death and release a gas ? Why Gangrene is death of body tissue due to a lack of blood flow or a serious bacterial infection. Gangrene commonly affects the arms and legs, including the toes and fingers, but it can also occur in the muscles and in organs.inside the body, such as the gallbladder  Clostridium species The Clostridia are large anaerobic ,Gram positive -1.1.rods.Motile with peritrichous flagella -2 Spore forming. The spores of clostridia are usually wider -3 than the diameter of rods in which they are formed ,the spores.is placed centrally ,subterminally ,or terminally Many 0f them decompose protiens and form toxins -4.,and some do both Their natural habitat is the soil or the intestinal tract -5.of humans and animal, where lives saprophytes Among the pathogens are the species causing -6 botulism,tetanus,gas gangrene and.pseudomembranous colitis The disease processes initiated by C. perfringens result from a combination of infection with the production of exotoxins.and/or enterotoxins and degradative enzymes Myonecrosis (gas gangrene): Clostridial spores are introduced into tissue, for example, by contamination with soil, Severe and open wounds, such as fractures and other ischemia-producing injuries (car accidents), are a prime.predisposing condition  Pasteurella multocida * Pasteurella multocida: Non-motile, a small, gram-negative, non–spore-forming, coccobacilli with bipolar appearance on stained smears, aerobic or facultative anaerobes, oxidase +, catalase + & encapsulated bacteria. * Part of the normal flora in the mouth of many animals (domestic animals, cats & dogs), transmitted by biting. * capsule is a virulence factor & endotoxin is present in the cell wall. * -Rapid onset of cellulitis at the site of cat bite. After cat bites osteomyelitis developed (because cats teeth sharp pointed implant bacteria under the periosteum). Bacteroides species: Gram negative bacilli non-spore forming, anaerobic bacteria that are predominant components of the bacterial flora of mucous membranes and are therefore a common cause of endogenous infections. Bacteroides infections can develop in all body sites, including the CNS, the head, the neck, the chest, the abdomen, the pelvis, the skin, ,the soft tissues and muscles. Bacillus cereus: Gram +ve spore- forming rods, causes food poisoning , and necrotizing fasciitis and myonecrosis (synergistic necrotizing cellulitis) developed a serious condition due to sepsis and disseminated intravascular coagulation. B. cereus also associated with localized and systemic infections, including endocarditis, meningitis, osteomyelitis, & pneumonia (by medical device or i.v. drug use). Vibrio vulnificus: Gram –ve comma shape (curved)rod. Found in marine & surface water, curved aerobic rods & motile with polar flagellum. Causes sever wound infections (in- immunocompromised persons), bacteremia (in.alcoholism & liver diseases) & gastroenteritis Wound infections may be mild but proceed rapidly (a- few hrs) with development of cellulitis & myositis with.necrosis.Diagnosis by TCBS agar (green colonies)- Fungi: Aspergillus spp. Blastomyces dermatitidis Candida spp. Coccidioides spp. Cryptococcus neoformans, Fusarium spp. Histoplasma capsulatum Pneumocystis jiroveci Candida spp. Candida species are responsible for the frequency encountered opportunistic fungal infections. Candidal infections are caused by various species but Candida albicans is the most frequent etiological agents. Candida albicans and others are a part of normal exogenous microbial flora ,of the skin ,mucous membrane , vaginal and gastrointestinal tract. Candida species colonize the mucosal surface of all humans during or soon after birth 20  morphological features of candida albicans.Morphology of Candida albicans Yeast form, unicellular, reproduce by budding.Single budding of the cells may be seen Candida albicans is termed a dimorphic fungus because it proliferates in either a yeast form or a hyphal form ( Candida albicans can grow in at least.three different morphologies: yeast, pseudohyphae and hyphae) Pathogensis There is no single fungal factor but multiple factors that contribute to their ability to cause infection. The yeast can enter the circulation by crossing the intestinal mucosa from the circulation, Candida infect the kidney, in the joint, eye or other sites. 22