《微生物学》课程PPT课件讲稿（英文版）Lecture 10 Staphylococci and Streptococci

Staphylococci Important human pathogen Causes both relatively minor and serious diseases One of the hardiest of the non sporeforming bacteria Can exist on dry surfaces for a long period Relatively heat-resistant; temperature range of18°-40°C BIOL 533 Lecture 10

BIOL 533 2 Lecture 10 Staphylococci • Important human pathogen – Causes both relatively minor and serious diseases • One of the hardiest of the non￾sporeforming bacteria – Can exist on dry surfaces for a long period – Relatively heat-resistant; temperature range of 18° - 40° C

Staphylococci Morphology Gram+ grape-like cluster, but in clinical specimens, can be a single cocci or diplococci General physiological characteristics Nonmotile Facultatively anaerobic Catalase Grows in media containing 10% Nacl BIOL 533 Lecture 10

BIOL 533 3 Lecture 10 Staphylococci • Morphology – Gram+ grape-like cluster, but in clinical specimens, can be a single cocci or diplococci • General physiological characteristics – Nonmotile – Facultatively anaerobic – Catalase + – Grows in media containing 10% NaCl

Staphylococci Relationship to disease (only 3 important s, aureus- causes a number of diseases -S. epidermidis-present in normal flora (normally benign, except when introduced via catheters, etc.) S. saprophyticus-causes uninary tract infections BIOL 533 Lecture 10

BIOL 533 4 Lecture 10 Staphylococci • Relationship to disease (only 3 important) – S. aureus—causes a number of diseases – S. epidermidis—present in normal flora (normally benign, except when introduced via catheters, etc.) – S. saprophyticus—causes uninary tract infections

Staphylococci Microbial physiology and structure Capsule may not be found growing on media, but it is usually present in vivo Teichoic acids are phosphate containing polysaccharides bound to both peptidoglycan and cytoplasmic membrane Species specific Poor immunogens but when bound to peptidoglycan, get an antibody response BIOL 533 Lecture 10

BIOL 533 5 Lecture 10 Staphylococci • Microbial physiology and structure – Capsule may not be found growing on media, but it is usually present in vivo – Teichoic acids are phosphate containing polysaccharides bound to both peptidoglycan and cytoplasmic membrane • Species specific • Poor immunogens, but when bound to peptidoglycan, get an antibody response

Pathogenesis of s aureus Features typical of staphylococci infections Initial lesion is normally mild and localized Results in a boil-normally, it is self-limiting Can result in systemic infection BIOL 533 Lecture 10

BIOL 533 6 Lecture 10 Pathogenesis of S. aureus • Features typical of staphylococci infections: – Initial lesion is normally mild and localized – Results in a boil—normally, it is self-limiting – Can result in systemic infection

Pathogenesis of s aureus Stage I: encounter-humans are major reservoir for s, aureus Colonize nose and are found in about 30% of individuals Transiently found on skin, oropharynx, and feces Transmitted via e Hand contact Aerosols from pneumonia patients BIOL 533 7 Lecture 10

BIOL 533 7 Lecture 10 Pathogenesis of S. aureus • Stage I: encounter—humans are major reservoir for S. aureus – Colonize nose and are found in about 30% of individuals – Transiently found on skin, oropharynx, and feces – Transmitted via: • Hand contact • Aerosols from pneumonia patients

Pathogenesis of s aureus Stage I, continued Certain occupations are more prone to colonization Physicians, nurses, hospital workers Certain classes of patients are more prone to colonization DiabeticS, hemodialysis patients, and drug abusers BIOL 533 Lecture 10

BIOL 533 8 Lecture 10 Pathogenesis of S. aureus • Stage I, continued – Certain occupations are more prone to colonization • Physicians, nurses, hospital workers – Certain classes of patients are more prone to colonization • Diabetics, hemodialysis patients, and drug abusers

Pathogenesis of s aureus Stage II: entry--not normally through unbroken skin Can enter if large numbers have accumulated through poor hygiene BIOL 533 Lecture 10

BIOL 533 9 Lecture 10 Pathogenesis of S. aureus • Stage II: entry—not normally through unbroken skin – Can enter if large numbers have accumulated through poor hygiene

Pathogenesis of s aureus Stage III: spread and multiplication Survival depends on ● Number of organisms ● Site involved Speed with which inflammatory response is mounted Immunological competence of host If inoculum is small and host immunologically competent: infection normally defeated BIOL 533 Lecture 10

BIOL 533 10 Lecture 10 Pathogenesis of S. aureus • Stage III: spread and multiplication – Survival depends on • Number of organisms • Site involved • Speed with which inflammatory response is mounted • Immunological competence of host – If inoculum is small and host immunologically competent: infection normally defeated

Pathogenesis of s aureus Stage IV: damage Local infection leads to formation of abscess (collection of pus) In skin boils or furuncles Interconnected abscesses are called carbuncles May also spread in subcutaneous or submucosal tissues--cellulitis BIOL 533 Lecture 10

BIOL 533 11 Lecture 10 Pathogenesis of S. aureus • Stage IV: damage – Local infection leads to formation of abscess (collection of pus) • In skin, boils or furuncles • Interconnected abscesses are called carbuncles – May also spread in subcutaneous or submucosal tissues—cellulitis