2. Skin Salt inhibits microbes. Lysozyme hydrolyzes peptidoglycan. Fatty acids inhibit some pathogens. Defensins are antimicrobial peptides. Figure 21.1
3. Mucous Membranes Line body cavities. The epithelial cells are attached to an extracellular matrix. Cells secrete mucus. Some cells have cilia.
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5.
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7. Normal Microbiota of the Skin Gram-positive, salt-tolerant bacteria Staphylococci Micrococci Diphtheroids Malasseziafurfur Figure 14.1a
8. Microbial Diseases of the Skin Exanthem: Skin rash arising from another focus of the infection. Enanthem: Mucous membrane rash arising from another focus of the infection.
43. Streptococcus pyogenes Local infections Impetigo Erysipelas Cellulitis Necrotizing fasciitis (flesh-eating bacterium) Systemic effect Streptococcal toxic shock-like syndrome (STSS) Spe (similar to TSS by S. aureus) Scarlet fever (pyrogenic toxin by lysogenized ) Post-infection Rheumatic fever (associated with pharyngitis) Glomerulonephritis
44. Invasive Group A Streptococcal Infections M protein Streptokinases Hyaluronidase Exotoxin A, superantigen Cellulitis Necrotizing fasciitis Figure 21.8
54. Infections by Pseudomonads Pseudomonas aeruginosa Gram-negative, aerobic rod Pyocyanin produces a blue-green pus Pseudomonas dermatitis Otitis externa Post-burn infections
71. NOTE:Large rectangular gram-positive bacilli NOTE:Double zone of hemolysis Inner beta-hemolysis = θ toxin Outer alpha-hemolysis = α toxin Micro & Macroscopic C. perfringens
72. Alpha toxin Treatment Debridement and excision Antibiotics (prevent further spreading) Hyperbaric oxygen therapy Inhibit or kill the anaerobic bacteria
73.
74. Enzootic in certain foreign countries (e.g., Turkey, Iran, Pakistan,and Sudan)
87. Cutaneous Anthrax Bacilllusanthracis G+ and spore forming Farm animals are major reservoir Inhalation, GI, cutaneous Virulence factors: Capsules Edema factor Lethal factor Vaccine Toxoid (protective antigen) Effective in short term but not long term Day 4 Day 5 Day 7 Day 12
94. Other Skin and Mucus Membrane Infections Staphylococcus epidermidis Catheters and prostheses Vibriovulnificus From shellfish and salt water Obligate anaerobes (usually polymicrobic and foul smelling) Puncture wounds Deep wounds Impaired blood supply Gram negative bacteria Decubitus ulcer (bed sores) After intestinal “spill” Pseudomonas aeruginosa Catheters and prostheses Burns and Surgical wounds
103. Poxviruses Smallpox (variola) Smallpox virus (orthopox virus) Variola major has 20% mortality Variola minor has <1% mortality Monkeypox Prevention by smallpox vaccination Figure 21.9
105. Distinguishing features of Smallpox from other rashes Note in this slide that the density of the rash is greater on the face than on the body. Pocks are usually present on the palms of the hands and on the soles of the feet.
107. Monkeypox – an indigenous virus of equatorial Africa Although not a virus of humans, the clinical symptoms are indistinguishable from smallpox. Lethality is only slightly less than smallpox. Although not as efficient as smallpox, Human to human transmission has been well documented Monkeypox should perhaps be considered a bioterrorist agent
108. In smallpox, fever is present for 2 to 4 days before the rash begins, while with chickenpox, fever and rash develop at the same time.All the pocks of the smallpox rash are in the same stage of development on any given part of the body and develop slowly. In chickenpox, the rash develops more rapidly, and vesicles, pustules, and scabs may be seen at the same time.
128. Human Herpesviruses Virus Subfamily Disease Site of Latency Herpes Simplex Virus Ia Orofacial lesions Sensory Nerve Ganglia Herpes Simplex Virus IIa Genital lesions Sensory Nerve Ganglia Varicella Zoster Virusa Chicken Pox Sensory Nerve Ganglia Recurs as Shingles Cytomegalovirusb Microcephaly/Mono Lymphocytes Human Herpesvirus 6b Roseola Infantum CD4 T cells Human Herpesvirus 7b Roseola Infantum CD4T cells Epstein-Barr Virus g Infectious Mono B lymphocytes, salivary Human Herpesvirus 8g Kaposi’s Sarcoma Kaposi’s Sarcoma Tissue
129. Herpes Simplex 1 and Herpes Simplex 2 Human herpes virus 1 and HHV-2 Cold sores or fever blisters (vesicles on lips) Herpes gladiatorum (vesicles on skin) Herpes whitlow (vesicles on fingers) Herpes encephalitis (HHV-2 has up to a 70% fatality rate)
130. Herpes Simplex 1 and Herpes Simplex 2 HHV-1 can remain latent in trigeminal nerve ganglia. HHV-2 can remain latent in sacral nerve ganglia. Acyclovir may lessen symptoms.
146. Measles (Rubeola) Measles virus Transmitted by respiratory route. Macular rash and Koplik's spots. Prevented by vaccination. Encephalitis in 1 in 1,000 cases. Subacute sclerosing panencephalitis in 1 in 1,000,000 cases. Figure 21.14
148. Measles induced syncytia Formation of giant cells (syncytia) in measles pneumonia. Notice the eosinophilic inclusions in both the cytoplasm and nuclei. (From Schaechter’s Mechanisms of Microbial Disease; 4th ed.; Engleberg, DiRita & Dermody; Lippincott, Williams & Wilkins; 2007; Fig. 34-3)
149. Measles pathogenesis Mechanisms of spread of the measles virus within the body and the pathogenesis of measles. CMI, Cell-mediated immunity; CNS, central nervous system. (From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 59-3.)
150. Measles time course Time course of measles virus infection. Characteristic prodrome symptoms are cough, conjunctivitis, coryza, and photophobia (CCC and P), followed by the appearance of Koplik's spots and rash. SSPE, Subacute sclerosing panencephalitis. (From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 59-4.)
151. Koplik’s spots Koplik's spots in the mouth and exanthem. Koplik's spots usually precede the measles rash and may be seen for the first day or two after the rash appears. (Courtesy Dr. J.I. Pugh, St. Albans; from Emond RTD, Rowland HAK: A color atlas of infectious diseases, ed 3, London, 1995, Mosby.) (From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 59-5.)
152. Measles rash Measles rash. (From Habif TP: Clinical dermatology: Color guide to diagnosis and therapy, St Louis, 1985, Mosby.) (From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 59-6.)
153. Rubella (German Measles) Rubella virus Macular rash and fever Congenital rubella syndrome causes severe fetal damage. Prevented by vaccination Figure 21.15
163. A 1905 list of skin rashes included (1)measles, (2)scarlet fever, (3)rubella, (4)Filatow-Dukes (mild scarlet fever), and (5)Fifth Disease: Erythema infectiosum Human parvovirus B19 produces milk flu-like symptoms and facial rash. Roseola Human herpesvirus 6 causes a high fever and rash, lasting for 1-2 days.
164. Parvovirus Structure Small (5 kb) linear ssDNA genome, naked capsid Pathogenesis respiratory transmission replication in nucleus, very host dependent, needs S phase cells or helper virus viremia antibody important in immunity targets erythroid lineage cells; fifth disease (symptoms immunological); transient aplastic crisis; hydropsfetalis Diagnosis serology, viral nucleic acid Treatment/prevention none
166. Parvovirus pathogenesis From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 56-3.
167.
168. Parvovirus pathogenesis A "slapped-cheek" appearance is typical of the rash for erythema infectiosum.(From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 56-5.)
173. Cutaneous Mycoses Dermatomycoses: Tineas or ringworm Metabolize keratin Trichophyton:Infects hair, skin, and nails Epidermophyton: Infects skin and nails Microsporum: Infects hair and skin Treatment Oral griseofulvin Topical miconazole
209. Dermatophytid Reaction(ID) Culture skin scrapings from feet Treat the tineapedis The hand lesion (ID phenomenon) will respond to therapy of the foot.
220. Subcutaneous mycoses Tineacorporis Subcutaneous infections - produce chronic inflammatory disease of subcutaneous tissues and lymphatics. sporotrichosis - ulcerated lesions at site of inoculation followed by multiple nodules - caused by a dimorphic fungus: Sporotrixschenckii.
223. Candidiasis Candida albicans (yeast) Candidiasis may result from suppression of competing bacteria by antibiotics. Occurs in skin; mucous membranes of genitourinary tract and mouth. Thrush is an infection of mucous membranes of mouth. Topical treatment with miconazole or nystatin.
227. Candidiasis Thrush Risk factors for candidiasis Post-operative status Cytotoxic cancer Chemotherapy Antibiotic therapy Burns Drug abuse Gastrointestinal damage. Cutaneous
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230. Scabies Sarcoptes scabiei burrows in the skin to lay eggs Treatment with topical insecticides Figure 21.18
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235. Pediculosis Pediculus humanus capitis (head louse) P. h. corporis (body louse) Feed on blood. Lay eggs (nits) on hair. Treatment with topical insecticides. Figure 21.19
236.
237. Macular Rashes A 9-year-old girl with a history of cough, conjunctivitis, and fever (38C) has a mcular rash that starts on her face and neck and is spreading to the rest of her body. Can you identify the cause of her symptoms Measles Rubella Fifth disease Roseola Candidiasis
242. Bacterial Diseases of the Eye Conjunctivitis (pinkeye) Haemophilus influenzae Various microbes Associated with unsanitary contact lenses Neonatal gonorrheal ophthalmia Neisseria gonorrhoeae Transmitted to a newborn's eyes during passage through the birth canal. Prevented by treatment of a newborn's eyes with antibiotics
248. Bacterial Diseases of the Eye Chlamydia trachomatis Inclusion conjunctivitis Transmitted to a newborn's eyes during passage through the birth canal Spread through swimming pool water Treated with tetracycline Trachoma Leading cause of blindness worldwide Infection causes permanent scarring; scars abrade the cornea leading to blindness
253. Viral Diseases of the Eye Conjunctivitis Adenoviruses Herpetic keratitis Herpes simplex virus 1 (HHV-1). Infects cornea and may cause blindness Treated with trifluridine
264. 222 What is MRSA? Easily transmitted and drug resistant, MRSA can survive on hands, clothing, environmental surfaces, and equipment. About 126,000 hospitalized patients develop MRSA infections each year. Over 5,000 of those patients die.
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266. 224 More about MRSA Staphylococcus aureus is commonly carried on healthy people’s skin, nares, and perineum. It may cause superficial skin infections treatable with beta-lactam inhibitors (such as methicillin). Over time, some strains have become resistant. First cases of MRSA in the United States occurred in the 1960s. Today, 46 out of 1,000 patients have MRSA.
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268. 226 Controlling the spread of MRSA in a health care facility Improve hand hygiene. Make fastidious environmental cleaning and disinfection a priority. Consider performing active surveillance cultures. Identify colonized patients and implement contact precautions. Implement and perform all interventions from the central line bundle and the ventilator bundle.
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270. 228 Stopping antimicrobial drug resistance Using antibiotics appropriately is key. Encourage cultures before antibiotics are started, and, if necessary, narrow the spectrum of antibiotics based on culture results. Review all culture reports to ensure that bacteria are sensitive to the prescribed antibiotics. Teach the patient how to use antibiotics: Take as prescribed Finish the course of treatment Don’t take someone else’s prescribed medication
271. 229 Two types of MRSA Community-associated MRSA (CA-MRSA) Causes skin and soft-tissue infections, such as boils, blisters, abscesses, folliculitis, and carbuncles Also, fever and local warmth, swelling, pain, and purulent drainage Health care-associated MRSA More highly drug resistant Causes more invasive infections, such as surgical site infection, endocarditis, osteomyelitis, bacteremia, pneumonia “According to the Centers for Disease Control and Prevention definition, a diagnosis of CA-MRSA requires that the patient have no medical history of MRSA or colonization and no risk factors associated with health care–associated MRSA.”
272. 230 MRSA transmission CA-MRSA Person-to-person by sharing personal items (clothing and towels) Close contact Health care-associated MRSA Contaminated environmental surfaces Staff members
