Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae and Streptococcus pyogenes on mannitol salt agar plates (containing 7.5% NaCl, mannitol and phenol red).

staphylococcal food poisoning toxic shock syndrome staphylococcal scalded skin syndrome exfoliatin enterotoxin TSST-1

Streptococci

oral cavity intestinal tract female genital tract anaerobes

Rebecca Craighill Lancefield (1895 –1981) She is most famous for her serological classification of beta-hemolytic streptococcal bacteria, which is based on the carbohydrate composition of bacterial antigens found on their cell walls. Lancefield classification: A serologic classification of hemolytic streptococci, dividing them into groups A to V, 20 groups. Most human pathogens are from Group A, eg. Streptococcus pyogenes.

pyogenic inflammation scarlet fever streptococcal toxic shock syndrome rheumatic heart disease glomerulonephritis

M protein rr r peptidoglycanComplementfibrinogen It is a component of group A streptococci pili that can inhibits phagocytosis. M protein binds fibrinogen in plasma which blocks complement to bind to the underlying peptidoglycan layer.

M protein may have cross antigenecity with some of human tissue such as endocardium and glomerular basement membrane. the bigger problem is …

type III hypersensitivity (most) M protein-Ab immune complex deposition on glomerular basement membrane activation of complement tissue destruction type II hypersensitivity common Ag cross reacts with glomerular basement membrane tissue destruction

Acute glomerulonephritis happens ! a disease of kidney caused by the immune complex during the infection of Group A streptococci (S. pyogenes). In this disease type III hypersensitivity and type II hypersensitivity are involved. Then …

Rheumatic fever happens ! An autoimmune disease caused by the infection of Group A streptococci (S.pyogenes). It affects primarily the heart (rheumatic heart disease) and joints (rheumatic arthritis). Then …

1.Hemolysins: cytolytic. 2.Hyaluronidase (spreading factor): digest hyaluronic acid in connective tissue. 3.Streptokinases: lyse fibrin. 4.Streptodornases: degrade DNA. 5.Pyrogenic exotoxins (Erythrogenic Toxins): encoded by a bacteriophage gene, has protease activity to cause soft tissue necrosis or toxic shock syndrome. What ’ s more, …

pyogenic inflammation scarlet fever streptococcal toxic shock syndrome rheumatic heart disease glomerulonephritis

Local infection: Group A streptococci (S. pyogenes) causes many inflammatory pyogenic inflammation such as impetigo ( 脓泡疹 ), pharyngitis ( 咽喉炎 ), tonsillitis ( 扁桃体炎 ), cellulitis ( 蜂窝织炎 ), and erysipelas (an infection of the skin in legs characterized by massive edema, 丹毒 ), tympanitis ( 中耳炎 ), sinusitis ( 鼻窦炎 ). Systemic infection: Group A streptococci (S. pyogenes) causes pneumonia, osteomyelitis ( 骨髓炎 ), arthritis and meningitis. Pyogenic infections

treat early penicillin G

Streptococcus pneumoniae (the pneumococcus) Streptococcus pneumoniae (the pneumococcus)

colonize respiratory tract The diseases it causes: pneumonia tympanitis (otitis media) meningitis

- + Streptococcus pneumoniae produces autolytic enzymes called as autolysin. Bile salts such as sodium deoxycholate can activate autolysin. Bile Solubility Test: Add bile-salt solution into an established broth culture. Streptococcus pneumoniae positive culture is clear with no turbidity.

Optochin Test: is an assay which is used to identify strains of S. pneumoniae. Optochin disks are placed on inoculated blood agar plates. Because S. pneumoniae is not resistant to optochin, a zone of inhibition will develop around the disk where the bacteria have been lysed. - +

Most strains of S. pneumoniaeare sensitive to penicillin but the resistance is frequent. Most strains of S. pneumoniae are sensitive to penicillin but the resistance is frequent. A vaccine with a mixture of capsule from 14 serotypes is available.

Neisseria

Chocolate blood agar, an enriched, non-selective medium. Contains red blood cells that have been lysed by heating very slowly to 56 °C. Lysed red blood cells provide growth factors, and is the cause for the brown color.

Neisseria meningitidis (the meningococcus)

Colonize upper respiratory tract in human. It can invade bloodstream and finally the brain. The diseases: meningitis epidemic cerebrospinal meningitis

Virulence factors Pilus: adhesion Capsule inhibits phagocytosis Endotoxin the main pathogenic substance

Neisseria gonorrhoeae (the gonococcus)

pyogenic effusion from a patient (acute urethritis)

pyogenic effusion from a newborn’s right eye

Diseases Acute urethritis (male) Pelvic inflammation (female) Ophthalmia neonatorum (infected from the vagina of gonorrhea parturient)

Virulence factors Pilus The gonococci with no pili are avirulent IgA1 protease destroy secretary IgA (S-IgA) Endotoxin Outer membrane protein (OMP) Porin proteins (PI) suppress phagosome-lysosome fusion Opacity proteins (Opa, PII) help the bacterium bind to the epithelium Reduction-modifiable proteins (Rmp, PIII) inhibit activity of the specific antibody

Sample collection: the two pathogens are very fragile. They are extremely sensitive to dryness, heat and coldness. A smear from spinal fluid for cerebrospinal meningitis or pyogenic effusion for gonorrhea may show the presence of Gram-negative diplococci present in polymorphonuclear cells.

Penicillin therapy: Still used for cerebrospinal meningitis and gonorrhea. Resistant strains of gonococcus producing beta-lactamase are very common.

For prevention of ophthalmia neonatorum, 0.1 % silver nitrate solution (AgNO 3 ) is dropped into the eyes after the baby is born.

There are two vaccines of the meningococcus, which are mixture of groups A and C capsule or a mixture of groups A, C, Y and W135 capsule. No gonorrhea vaccine is available.

Summary 1.Diseases and molecular mechanisms of Streptococci 2.Identification of the pneumococcus (diagnosis) 3.Diseases and diagnosis of two species of Neisseria