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37 Cards in this Set
- Front
- Back
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Staphylococci
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- Common inhabitant of the skin and mucous membranes
- Spherical cells arranged in irregular clusters - Gram-positive - Lack spores and flagella - May have capsules - 31 Species |
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Staphylococcus Aureus
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- Grows in large, round, opaque colonies
- Optimum growth temperature of 37 degrees Celsius - Facultative anaerobe - Withstands high salt, extremes in pH, and high temperatures - Carried in nasopharynx and skin - Produces many virulence factors |
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Coagulase
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Coagulates plasma and blood; produced by 97% of human isolates, diagnostic
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Hyalouronidase
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Digests connective tissue
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Staphylokinase
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Digests blood clots
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DNase
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Digests DNA
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Lipases
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Digest oils; enhance colonization on skin
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Penicillinase
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Inactivates penicillin
(Neutralizes the effect of antibiotics) |
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Hemolysins
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Lyse (kill) red blood cells
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Leukocidin
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Lyses neutrophils and macrophages
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Enterotoxin
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Induce gastrointestinal distress
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Exfoliative Toxin
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Separates the epidermis from the dermis
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Toxic Shock Syntrome Toxin
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Induces fever, vomiting, shock, systemic organ damage
(Women) |
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Localized Cutaneous Infections
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Invade skin through wounds, follicles, or glands
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Folliculitis
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Superficial inflammation of hair follicle; usually resolved with no complications but can progress (can become abscess)
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Furuncle
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Boil; inflammation of hair follicle or sebaceous gland progresses into abscess or pustule
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Carbuncle
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Larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles
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Impetigo
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Bubble-like swellings that can break and peel away; most common in newborns.
- Hair is NOT involved, microorganisms can gain entrance through the pores. |
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Systemic Infections - Osteomyelitis
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Infection is established in the metaphysis; abscess forms
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Systemic Infections - Bacteremia
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Primary organ is bacteria from another infected site or medical devices; endocarditis possible
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General Characteristics of Streptococci
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- Gram-positive, spherical/ovoid cocci arranged in long chains, commonly in pairs.
- Non-spore-forming, non-motile - Can form capsules and slime layers - Facultative anaerobes - Do not form catalase, but have a peroxidase system - Most parasitic forms are fastidious and require enriched media - Small, non-pigmented colonies - Sensitive to drying, heat and disinfectants - 25 Species |
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Human Streptococcal Pathogens
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- S. pyogenes
- S. agalactiae - Viridans streptococci - S. pneumoniae - Enterococcus faecalis |
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S. pyogenes
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Most serious streptococcal pathogen.
- Strict parasite - Inhabits throat, nasopharynx, and occasionally the skin |
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Virulence Factors of Beta Hemolytic S. pyogenes (Surface antigens)
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Produces surface antigens:
- C-carbohydrates - protect agaisnt lysozyme - Fimbriae - adherance - M-protien - contributes to resistance to phagocytosis - Hyalournic acid capsule - provokes no immune response |
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Virulence Factors of Beta Hemolytic S. pyogenes (Extracellular Toxins)
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Extracellular Toxins:
- Streptolysins - Hemolysins, streptolysin O (SLO) and stretpolysin S (SLS). Both cause cell and tissue injury - Pyogenic Toxin (Ertythrogenic) - Induces fever and typical red rash - reaches to hypothalamus and re-sets the body temperature - Superantigens - Strong monocyte and lymphocytes stimulants, cause the release of tissue necrotic factor |
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Systemic Infections
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- Scarlet Fever - strain of S. pyogenes carrying a prophage that codes for pyrogenic toxin; can lead to sequelae - A virus has to enter the bacterial cell and become a part of the bacterial chromosome.
- Septicemia - Pneumonia - Streptococcal toxic shock syndrome |
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Rheumatic Fever
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Follows overt or sub-clinical pharyngitis in children; carditis with extensive valve damage possible, arthritis, chorea, fever
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Acute Glomerulonephritis
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Nephritis, increased blood pressure, occasionally heart failure, ; can become chronic leading to kidney failure
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Streptococcus pneumoniae
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- Causes 60-70% of all bacterial pneumonias
- Small, lancet-shaped cells arranged in pairs and short chains - Culture requires blood or chocolate agar - Growth improved by 5-10% C02 - Lack catalase and peroxidases - cultures die in oxygen. (Rats, Griffith - led to discovery of DNA) |
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S. pneumoniae Epidemiology and Pathology
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- 5% to 50% of all people carry it as normal flora in the nasophayrnx; infections are usually endogenous
- Very delicate, does not survive long outside of its habitat - Young children, elderly, immune compromised, those with other lung diseases or viral infections, persons living in close quarters are predisposed to pneumonia - Pneumonia occurs when cells are aspirated into the lungs of susceptible individuals - Pneumococci multiply and induce an overwhelming inflammatory response - Gains access to middle ear by way of esutachian tube |
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Neisseria gonorrhoeae - Virulence Factors
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- Pili, other surface molecules for attachment, slows phagocytosis
- Pilli (transfers plasmid DNA from host to recipient) - IgA protease - cleaves secretory IgG |
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Neisseria gonorrhoeae - Infection
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Infection is asymptomatic in 10% of males and 50% of females
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Neisseria gonorrhoeae - Males
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Urethritis, yellowish discharge and infertility
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Neisseria gonorrhoeae - Females
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Vaginitis, urethritis, salpingitis (PID), mixed anaerobic abdominal infection, common cause of sterility and ectopic tubal pregnancies
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Neisseria gonorrhoeae - Extragenital Infections
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Anal, pharyngeal, conjunctivitis, septicemia, arthritis
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Neisseria meningitidis - Virulence Factors
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- Capsule
- Pili - IgA protease - Endotoxin |
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Neisseria meningitidis - Epidemiology and Pathogenesis
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- Prevalent cause of meningitis; sporadic or epidemic
- Human reservoir - nasopharynx; 3-30% of adult population higher in institutional settings - High risk individuals are thos living in close quarters, children 6 months - 3 years, children and young adults 10 to 20 years - Disease begins when bacteria enter bloodstream, pass into cranial circulation, and multiply in meninges - Very rapid onset, neurological symptoms; endotoxin causes hemorrhage and shock; can be fatal |
