Pyogenic Coccus

The Staphylococci

Morphology & Identification Gram positive Facultative anaerobes Grape like-clusters Catalase positive Major components of normal flora skin nose

Gram Positive cocci - staphylococci Pus

Catalase test（过氧化氢酶） (-) (+)

Pathogenesis & Immunity of Staphylococcus aureus

Antigenic Structure

Protein A inhibits phagocytosis PHAGOCYTE Fc receptor immunoglobulin Protein A BACTERIUM

Toxins & Enzymes Catalase Coagulase Hyaluronidase and Lipase Hemolysin or sphingomyelinase C Leukocidin Exfoliative Toxin Toxic Shock Syndrome Toxin (superantigen) Enterotoxins

Pathogenesis

Pathogenesis of staphylococcal infections Stye:麦粒肿 Carbuncle:痈 Impetigo：脓疱疮

Infections associated with indwelling devices

Superantigens and the non-specific stimulation of T cells

Clinical Findings- Suppurative A. (Skin) Furuncle; Protein A, Leukocidin, Hemolysin Stye; lipase Impetigo; contagious Epidermal necrolysis Exfoliative Dermatitis (6,7,8); Exfoliative toxin Mastitis Abscess (deep tissue); granulation; coagulase, hyaluronidase (burn, wound) B. Systemic : Bactermia (from abscess, wound, burn) , Osteomyelitis (tibia) ,Pneumonia

Clinical Findings- Food poisoning not a human infection food contaminated from humans growth enterotoxin onset and recovery both occur within few hours Vomiting/ nausea/ diarrhea/ abdominal /pain

Toxic shock syndrome fever scarlatiniform rash desquamation vomiting diarrhea myalgias

S. aureus babies scalded skin syndrome exfoliatin

Pseudomembranous Colitis

Laboratory A. Direct examination; Gram Stain B. Primary media; BAP C. Differential Tests. Mannitol Salts Coagulase DNase D. Phage typing E. Antibiotic Sensitivity (plasmid, B lactamase) penicillin /methicillin/vancomycin

S. aureus on BAP

Mannitol Salt Agar

DNase test 0.1% Toluidine blue O (+): Pink 1N HCl (+) :

S. aureus on potassium tellurite agar

Lysostaphin test Staphylococcus Micrococcus

API STAPH Kit

Staphylococcus epidermidis major component skin flora opportunistic infections less common than S.aureus nosocomial infections heart valves Identification Non-hemolytic (sheep blood agar) Does not ferment mannitol Non-pigmented Coagulase-negative

Staphylococcus saprophyticus urinary tract infections coagulase-negative not differentiated from S. epidermidis

The Streptococcus

Streptococcus

Morphology & Identification facultative anaerobe Gram-positive Chains or pairs Catalase negative (staphylococci are catalase positive)

Cell surface structure of S pyogenes and extracellular substances

S. pyogenes lipoteichoic acid F-protein fibronectin epithelial cells

M protein major target strain variation re-infection natural immunity antigenicity re-infection occurs with different strain

M protein IMMUNE Complement IgG M protein NON-IMMUNE peptidoglycan fibrinogen r

Capsules Anti-phagocytic mucoid strains

Streptococci Lancefield groups one or more species per group surface antigens

groupable streptococci A, B and D most important C, G, F rare

Non-groupable S. pneumoniae viridans streptococci pneumonia e.g. S. mutans dental caries

Toxins & Enzymes

Hemolysis alpha beta gamma

Classofication of Streptococci of Particular Medical Interest

Pathogenesis of S pyogenes infections.

Group A streptococcal infections affect all ages peak incidence at 5-15 years of age

S. pyogenes -suppurative non-invasive pharyngitis skin infection, impetigo invasive bacteremia toxic shock-like syndrome "flesh eating" bacteria pyrogenic toxin

Pyrogenic toxin superantigen T cell mitogen activates immune system

Scarlet fever rash erythrogenic toxin

non-suppurative rheumatic fever inflammatory disease life threatening chronic sequalae fever heart joints rheumatic NOT rheumatoid arthritis

Rheumatic fever -etiology M protein cross-reacts heart myosin autoimmunity cell wall antigens poorly digested in vivo persist indefinitely

Rheumatic fever

Acute glomerulonephritis immune complex disease of kidney

Group B streptococcus neonatal meningitis septicemia transmission vaginal flora

Group B streptococcus - identification  hemolysis hippurate hydrolysis CAMP reaction increases  hemolysis of S. aureus

Group D streptococcus Growth on bile esculin agar black precipitate 6.5% saline grow enterococci no growth non-enterococci

Enterococci distantly related to other streptococci genus Enterococcus gut flora urinary tract infection fecal contamination opportunistic infections particularly endocarditis most common E. (S.) faecalis

Enterococci resistant to many antibiotics including vancomycin terminal D-ala replaced by D-lactate

Viridans streptococci diverse species oral dental caries  hemolytic and negative for other tests non-groupable. includes S. mutans endocarditis tooth extraction

Diagnostic Laboratory Test

Post-infectious diagnosis (serology) antibodies to streptolysin O important if delayed clinical sequelae occur

Serotyping M T R

S. pneumoniae - diplococci

S. pneumoniae Virulence factors a. capsule: It is antiphagocytic, inhibiting entrapment and phagocytosis where type-specific opsonic antibody is absent. Non-capsulate mutants are avirulent in experimental animals. b. pneumolysin: It suppresses phagocytic oxidative burst. It is a membrane-damaging toxin. Thus it can destroys red blood cells and possibly ciliated epithelial cells. c. Surface protein adhesinand secretory IgA protease: The biologic effects are to help S.pneumoniae for the colonization and migration. d.Teichoic acid and the Peptidoglycan fragment, phosphorylchorine : They can mediate the mobilization of inflammatory cells to the focus of infection and cause the tissue destruction/complement activation

Capsule prominent virulent strains anti-phagocytic carbohydrate antigens vary among strains immunity serotype specific vaccine contains multiple serotypes only for susceptible population

clinic finding leading cause pneumonia particularly young and old after damage to upper respiratory tract *e.g. following viral infection bacteremia meningitis middle ear infections (otitis media)

(-) (+) (Bile solubility test)

Autolysis - identification autolysin Bile teichoic acid -choline peptidoglycan cell membrane lipoteichoic acid

Identification Not optochin sensitive optochin sensitive

Quellung reaction using antisera capsule "fixed" visible microscopically

Streptex antiserum

Latex agglutination - streptococci

Prevention and Treatment Immunity ; 14 capsule types mixed vaccine Most strains susceptible to penicillin , but resistance is common

NEISSERIA Neisseria gonorrhoeae

Neisseria Gram negative diplococci (pairs of cocci) oxidase positive culture Thayer Martin. selective chocolate agar heated blood (brown)

X LPS PILI Capsule N. meningitidis N. gonorrhoeae Virulence Factors Similar, but – Differences in utilization LPS LPS IgA protease Capsule PILI Opacity (OPA) proteins Outer Membrane Proteins Hemolysin IgA protease PILI Opacity (OPA) proteins Outer Membrane Proteins X NO capsule NO hemolysin

N. gonorrhoeae the "gonococcus" After 2-14 days Found only in man Gonorrhea: second most common venereal disease

Neisseria gonorrhoeae Gram stain of pure culture Urethral exudate Using the Gram stain in patient specimens, the organisms are most often observed in polymorphonuclear leukocytes

Neisseria gonorrhoeae

Neisseria gonorrhoeae Pili = key in anchorage of organisms to mucosal epithelium. Nonpiliated gonococci are avirulent OUTER MEMBRANE PROTEINS Porin proteins (Por) = prevent phagolysosome fusion & allow intracellular survival [ also called protein I] Opacity proteins (Opa) = binding of organisms to epithelium [also called protein II] Reduction-modifiable proteins (Rmp) = protection against bactericidal antibodies [ also called protein III]

Neisseria gonorrhoeae Symptomatic infections are notably PURULENT Urethritis

Neisseria gonorrhoeae Symptomatic infections are notably PURULENT Bartholin’s Duct

Neisseria gonorrhoeae Purulent conjunctivitis Ophthalmia neonatorum Infection in newborns during vaginal delivery

Neisseria gonorrhoeae Disseminated gonococcal infection (DGI). Fever, polyarthritis (or monoarticular septic arthritis), and/or dermatitis (pustules on a hemorrhagic base).

Smear polymorphonuclear cell Gram negative cocci many in cells Culture

Antibiotic therapy  lactamase-resistant cephalosporin e.g. ceftriaxone resistant strains common produce  lactamases destroy penicillin

N. meningitidis (the "meningococcus")

N. meningitidis resides in man only usually sporadic cases mostly young children outbreaks adults crowded conditions e.g. army barracks

Neisseria meningitidis upper respiratory tract infection adhesion pili bloodstream brain

Meningococcal meninigitis 1-4 days Second most common meningitis pneumococcus, most common Fatal if untreated Responds well to antibiotic therapy penicillin

Laboratory Diagnosis spinal fluid Gram negative diplococci within polymorphonuclear cells meningococcal antigens Culture Thayer Martin agar

Prevention - Capsule capsule inhibit phagocytosis anti-capsular antibodies stop infection antigenic variation serogroups vaccine multiple serogroups