Staphylococci The Staphylococci

Morphology & Identification  Gram positive  Facultative anaerobes  Grape like-clusters  Catalase positive  Major components of normal flora  skin  nose Catalase test （过氧化氢 酶） (-) (+)

Staphylococcus aureus

Antigenic Structure

Pathogenesis Catalase Coagulase ipaseHyaluronidase and Lipase sphingomyelinase CHemolysin or sphingomyelinase C Leukocidin Exfoliative Toxin Toxic Shock Syndrome Toxin (superantigen) Enterotoxins Protein A immunoglobulin Fc receptor BACTERIUM PHAGOCYTE

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

Suppurative SkinSkin  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) SystemicSystemic Bactermia (from abscess, wound, burn), Osteomyelitis (tibia),Pneumonia Bactermia (from abscess, wound, burn), Osteomyelitis (tibia),Pneumonia

Food poisoningFood poisoning Toxic shock syndromeToxic shock syndrome babiesbabies –scalded skin syndrome *Exfoliatin feverfever scarlatiniform rashscarlatiniform rash desquamationdesquamation vomitingvomiting diarrheadiarrhea myalgiasmyalgias not a human infectionnot a human infection food contaminated from humansfood contaminated from humans – growth – enterotoxin onset and recovery both occur within few hoursonset and recovery both occur within few hours Vomiting/ nausea/ diarrhea/ abdominal /painVomiting/ nausea/ diarrhea/ abdominal /pain

Infections associated with indwelling devices

Laboratory A. Direct examination; Gram Stain B. Primary media; BAP C. Differential Tests. 1.Mannitol Salts 2.Coagulase 3.DNase D. Phage typing E. Antibiotic Sensitivity (plasmid, B lactamase) : penicillin /methicillin/vancomycin API STAPH Kit

Staphylococcus epidermidis major component skin floramajor component skin flora opportunistic infections opportunistic infections – less common than S.aureus nosocomial infections nosocomial infections – heart valves IdentificationIdentification – 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 anaerobefacultative anaerobe Gram-positiveGram-positive Chains or pairsChains or pairs Catalase negativeCatalase negative (staphylococci are catalase positive) (staphylococci are catalase positive)

Cell surface structure of S pyogenes and extracellular substances Lancefield groupsLancefield groups *one or more species per group *surface antigens: M, T, R streptococci groupable streptococci A, B and DA, B and D –most important C, G, FC, G, F –Rare Non-groupable S. pneumoniaeS. pneumoniae –pneumonia viridans streptococciviridans streptococci –e.g. S. mutans *dental caries

Lipoteichoic Acid and F-protein fibronectin lipoteichoic acid F-protein epithelial cells

M protein major targetmajor target –natural immunity strain variationstrain variation –antigenicity re-infectionre-infection –occurs with different strain

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

Toxins & Enzymes

Hemolysis alpha beta gamma

Classofication of Streptococci of Particular Medical Interest

Pathogenesis of S pyogenes infections.

. pyogenes (Group A) -suppurative S. pyogenes (Group A) -suppurative affect all ages peak incidence at 5-15 years of ageaffect all ages peak incidence at 5-15 years of age non-invasivenon-invasive –pharyngitis –skin infection, impetigo invasive bacteremiainvasive bacteremia –toxic shock-like syndrome –"flesh eating" bacteria –pyrogenic toxin

Scarlet feverScarlet fever  rash  erythrogenic toxin rheumatic feverrheumatic fever  inflammatory disease  life threatening  chronic sequalae  fever  Heart  Joints  rheumatic NOT rheumatoid arthritis Acute glomerulonephritis immune complex disease of kidneyAcute glomerulonephritis immune complex disease of kidney Rheumatic fever -etiology  M protein –cross-reacts heart myosin –autoimmunity  cell wall antigens – poorly digested in vivo –persist indefinitely Post-infectious diagnosis (serology) antibodies to streptolysin O antibodies to streptolysin O important if delayed clinical sequelae occur important if delayed clinical sequelae occur superantigensuperantigen T cell mitogen T cell mitogen activates immune systemactivates immune system

Group B streptococcus - identification neonatal meningitisneonatal meningitis septicemiasepticemia transmissiontransmission – vaginal flora  hemolysis  hemolysis hippurate hydrolysishippurate hydrolysis CAMP reactionCAMP reaction –increases  hemolysis of S. aureus

Group D streptococcus Growth on bile esculin agarGrowth on bile esculin agar –black precipitate 6.5% saline6.5% saline grow grow – enterococci no growthno growth – non-enterococci

Enterococci distantly related to other streptococcidistantly related to other streptococci genus Enterococcusgenus Enterococcus gut floragut flora –urinary tract infection fecal contaminationfecal contamination –opportunistic infections particularly endocarditisparticularly endocarditis most common E. (S.) faecalismost common E. (S.) faecalis resistant to many antibioticsresistant to many antibiotics –including vancomycin terminal D-ala replaced by D-lactateterminal D-ala replaced by D-lactate

Viridans streptococci diverse speciesdiverse species oraloral dental cariesdental caries  hemolytic and negative for other tests  hemolytic and negative for other tests non-groupable.non-groupable. includes S. mutansincludes S. mutans –endocarditis –tooth extraction

Streptococcus pneumoniae S. pneumoniae - diplococci capsule:capsule: pneumolysin:pneumolysin: Surface protein adhesinand secretory IgA protease.Surface protein adhesinand secretory IgA protease. Teichoic acid and the Peptidoglycan fragment, phosphorylchorine.Teichoic acid and the Peptidoglycan fragment, phosphorylchorine. leading cause pneumonialeading cause pneumonia –particularly young and old –after damage to upper respiratory tract *e.g. following viral infection bacteremiabacteremia meningitismeningitis middle ear infections (otitis media)middle ear infections (otitis media)

Streptex antiserum Latex agglutination - streptococci Quellung reaction using antiserausing antisera capsule "fixed"capsule "fixed" visible microscopicallyvisible microscopically Not optochin sensitiveoptochin sensitive Bile solubility test

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

Gram negative Gram negative diplococci (pairs of cocci) diplococci (pairs of cocci) oxidase positive oxidase positive Culture: 5-10% CO 2Culture: 5-10% CO 2 Thayer Martin. Thayer Martin. – selective – chocolate agar * heated blood Neisseria Neisseria

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

Neisseria gonorrhoeae Using the Gram stain in patient specimens, the organisms are most often observed in polymorphonuclear leukocytes Gram stain of pure cultureUrethral exudate After 2-14 days After 2-14 days Found only in manFound only in man Gonorrhea: second most common venereal disease Gonorrhea: second most common venereal disease

Pili = key in anchorage of organisms to mucosal epithelium. Nonpiliated gonococci are avirulent 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 OUTER MEMBRANE PROTEINS

Bartholin’s Duct Urethritis

Disseminated gonococcal infection (DGI). Fever, polyarthritis (or monoarticular septic arthritis), and/or dermatitis (pustules on a hemorrhagic base). Purulent conjunctivitis/Ophthalmia neonatorum Infection in newborns during vaginal delivery

Smear polymorphonuclear cellpolymorphonuclear cell Gram negative cocciGram negative cocci many in cells many in cells CultureCulture  lactamase-resistant cephalosporin  lactamase-resistant cephalosporin – e.g. ceftriaxone resistant strains resistant strains – common – produce  lactamases – destroy penicillin Antibiotic therapy

N. meningitidis N. meningitidis (the "meningococcus")

Neisseria meningitidis resides in man onlyresides in man only usually sporadic cases usually sporadic cases – mostly young children outbreaks outbreaks – adults – crowded conditions *e.g. army barracks 1-4 days1-4 days Second most common meningitis Second most common meningitis – pneumococcus, most common Fatal if untreated Fatal if untreated Responds well to antibiotic therapy Responds well to antibiotic therapy – penicillin Upper respiratory tractinfection Upper respiratory tract infection – adhesion pili Bloodstream BloodstreamBrain Meningococcal meninigitis

Diagnosis spinal fluidspinal fluid – Gram negative diplococci within polymorphonuclear cells within polymorphonuclear cells – meningococcal antigens Culture Culture – Thayer Martin agar capsulecapsule – inhibit phagocytosis anti-capsular antibodies anti-capsular antibodies – stop infection antigenic variationantigenic variation – serogroups vaccine vaccine –multiple serogroups Prevention