Term
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Definition
| Strep and Staph. Are pyogenic (along with some Neisseria species which are gram neg). Activate many PMNs producing pus. |
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Term
| Staphylococcus general characteristics |
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Definition
| Large gram pos cocci (1 micron in diameter) that are usually grouped in clusters and are facultative anaerobes, are all cat pos and can grow in 7.5% salt. Survive for long periods on dry inanimate objects and are thus difficult to eliminate. Common source of hospital acquired infections. |
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Term
| Staph. aureus epidemiology |
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Definition
| Normal flora of skin, nasal pharynx, urethra and eye. Enters body through abrasions and cuts. Hardy and resistant to drying so can be acquired from fomites. Hospital staff and certain patient groups have higher rates of colonization |
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Term
| Staph. aureus pathogenesis |
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Definition
| Large number of virulence factors including: capsule, protein A, catalase, coagulase, hyaluronidase, lipases, proteases and DNAses for digesting tissue, beta lactamase. Toxins include enterotoxins, exfoliatin, toxic shock syndrome toxin (TSST-1, a superantigen), leukocidins and hemolysins. |
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Term
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Definition
| Gram stain first (as usual). This organism is catalase pos, coagulase pos, beta hemolytic, grow on 7.5% NaCl mannitol, and can be identified with nucleic acid tests (used to identify MRSA). |
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Term
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Definition
| Must drain abcess. All staph are resistant to penicillin due to penicillinase. Some strains are methicillin resistant (MRSA), these strains are resistant to all beta lactams. Vancomycin may be used but resistance is developing. |
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Term
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Definition
| Immune response is mediated by opsonizing IgG. Immunity is short-lived and incomplete so multiple infections are possible. Prevention includes handwashing and disinfectant practices. |
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Term
| Staph. honorable mentions: S. epidermidis |
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Definition
| Cat pos, coag neg, non-hemolytic white colonies on blood agar. Normal flora of skin, nose and throat. Only virulence factor is polysacc. slime (a biofilm) that enhances adherence. Causes infection of prosthetic devices, shunts, grafts and catheters. Most common cause of prosthetic valve endocarditis. |
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Term
| Staph. honorable mentions: S. saprophyticus |
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Definition
| Coag neg, non-hemolytic. Common cause of UTIs in healthy young women. |
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Term
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Definition
| Binds Fc portion of Ab, preventing activation of complement and hindering phagocytosis. |
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Term
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Definition
| Hydrolyzes connective tissue enhancing bacterial spreading. |
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Term
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Definition
| Agar w/ sheep RBCs. Growth patterns on these plates can help differentiate between species. |
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Term
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Definition
Gram pos. cocci arranged in chains. Cat neg, facultative anaerobe w/ small translucent colonies. Growth enchanced wit 5 to 10% CO2.
Heterogeneous group causing a variety of diseases. Pyogenic bacteria classified in three ways: 1) serologically (Lancefield grouping), 2) patterns of hemolysis and 3) species. |
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Term
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Definition
Serological grouping of Strep based on major cell wall carb antigens.
Group A (synonymous with S. pyogenes) - cause pharyngitis, scarlet fever
Group B - S. agalactiae, cause neonatal sepsis and meningitis
Group D - S. bovis, cause endocarditis, bacteremia |
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Term
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Definition
Viridans group - S. mutans, S. sanguis, S. salivarius - endocarditis
S. pneumonia - pneumonia, meningitis, otitis media
Peptostreptococcus - strict anaerobes |
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Term
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Definition
| Former group D strep that are normal flora of skin, URT, GI and urogenital tract. Cause infective endocarditis, UTI, bacteremia/septicemia and meningitis. |
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Term
| Classification by Hemolysis |
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Definition
Alpha - colony has green halo (or brown zone) indicating partial lysis of RBCs, includes viridans and S. pneumoniae
Beta - complete hemolysis evidenced by clear zone around colony, S. pyogenes and S. agalactiae
Gamma - non-hemolytic, group D strep and enterococci |
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Term
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Definition
| Group A strep that causes pharyngitis and scarlet fever, beta-hemolytic, bacitracin sensitive. |
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Term
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Definition
| Normal flora of GI and lower genital tracts. Beta-hemolytic, group B, bacitracin resistant. Cause of neonatal disease (infection from mother's vagina) and meningitis. |
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Term
| Viridans group (S. mutans, S. sanguis) |
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Definition
| Alpha-hemolytic, optochin resistant, no Lancefield antigens. Cause endocarditis in patients with damaged heart valves, dental caries. |
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Term
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Definition
| Alpha-hemolytic, optochin sensitive, no Lancefield antigens. Causes pneumonia, bacteremia, meningitis, otitis media. |
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