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chapter+26+fall08 - Chapter 26 Microbial Diseases Skin and...

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Chapter 26 Microbial Diseases Skin and Soft-Tissue Infections Staphylococcus aureus Boils/ pimples—walled off from body with fibrin Impetigo- skin infection “Scalded skin” syndrome- due to exfoliative toxin Can produce hemolysins, superantigen enterotoxin A (food poisoning), coagulase, leukocidin, superantigen TSST (toxic shock syndrome) Can also cause pneumonia and meningitis Treatment with penicillins MRSA—methicillin-resistant S. aureus Horizontal transfer of drug-resistant genes Evolved in environment with high levels of antibiotics Hospitals—nosocomial infections Resistant to all drugs except vancomycin Streptococcus pyogenes 60+ strains strep throat (pharyngitis) – 5~10% of sore throats diagnosis- blood agar: slow;antibody test: rapid infections of the inner ear impetigo- skin infection Scarlet fever – exotoxin superantigen; can follow pharyngitis; pink rash & strawberry tongue Rheumatic fever – autoimmune; antibodies against S. pyogenes react with host tissue – damages heart valves necrotizing fasciitis (“flesh eating”) Many viruses can cause skin rashes Usually infect through respiratory tract Chickenpox caused by Varicella-zoster virus (VZV), a herpesvirus VZV can lay dormant in nerve cells for long periods of time. Shingles is caused by the migration of VZV to the skin; painful blisters Measles/ rubeola caused by a paramyxovirus Symptoms- fever, cough, rash Mumps- inflammation of salivary glands Rubella/German measles Caused by a togavirus symptoms - similar to measles but milder Can be prevented with MMR vaccine Many fungal skin infections Respiratory Tract Infections Most respiratory pathogens are transferred from person to person via respiratory aerosols – coughing, sneezing, talking, breathing Transmission usually occurs over short distances because microorganisms survive poorly in air. Pathogens that can survive dry conditions such as many Gram positive & Mycobacteria are easier to transmit by air Streptococcus pneumoniae- lower repiratory diseases; can also cause meningitis
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pneumococcal pneumonia Inflammatory reaction in alveoli Usually a secondary infection Capsule protects organism from phagocytosis untreated- 30% mortality rate Alveoli become filled with blood, bacteria, & phagocytic cells Symptoms = sudden onset of chills, labored breathing, pleural (chest) pains Pneumonia can also be caused by viruses, other bacteria, or fungi S. pneumoniae is found in respiratory flora in about 40% of healthy people Corynebacterium diphtheriae Childhood upper respiratory infection, diphtheria. Pathogen strains of Corynebacterium diphtheriae produce exotoxin that inhibits protein synthesis Formation of pseudomembrane – damaged host cells & bacterial cells Causes constriction of throat, suffocation Early childhood immunization with diphtheria toxoid (part of DTP) is very effective for prevention of diptheria.
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chapter+26+fall08 - Chapter 26 Microbial Diseases Skin and...

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