英文版-Indiana-University-Purdue-University-Fort-Wayne微生物学授课讲义-lecture-10课件.ppt

1、Lecture 10BIOL 5331Staphylococci and StreptococciBIOL 533Lecture 10Medical MicrobiologyLecture 10BIOL 5332Staphylococci 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 Relative

2、ly heat-resistant;temperature range of 18-40 CLecture 10BIOL 5333Staphylococci 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%NaClLecture 10

3、BIOL 5334Staphylococci Relationship to disease(only 3 important)S.aureuscauses a number of diseasesS.epidermidispresent in normal flora(normally benign,except when introduced via catheters,etc.)S.saprophyticuscauses uninary tract infectionsLecture 10BIOL 5335Staphylococci Microbial physiology and st

4、ructure 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 responseLecture 10BIOL 533

5、6Pathogenesis of S.aureus Features typical of staphylococci infections:Initial lesion is normally mild and localized Results in a boilnormally,it is self-limiting Can result in systemic infectionLecture 10BIOL 5337Pathogenesis of S.aureus Stage I:encounterhumans are major reservoir for S.aureus Colo

6、nize nose and are found in about 30%of individuals Transiently found on skin,oropharynx,and feces Transmitted via:Hand contact Aerosols from pneumonia patientsLecture 10BIOL 5338Pathogenesis of S.aureus Stage I,continued Certain occupations are more prone to colonization Physicians,nurses,hospital w

7、orkers Certain classes of patients are more prone to colonization Diabetics,hemodialysis patients,and drug abusersLecture 10BIOL 5339Pathogenesis of S.aureus Stage II:entrynot normally through unbroken skin Can enter if large numbers have accumulated through poor hygieneLecture 10BIOL 53310Pathogene

8、sis 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 defeatedLecture 10BIOL 53311Pathogen

9、esis 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 tissuescellulitisLecture 10BIOL 53312Pathogenesis of S.aureus Stage IV,continued De

10、velopmentinvolves both host and bacterial factors Acute inflammatory reaction Proportion of bacteria survive and are capable of lysing neutrophils that engulfed them Outpouring of lysosomal enzymes that damage surrounding tissues Inflammatory area surrounded by fibrin clotLecture 10BIOL 53313Virulen

11、ce Factors of S.aureus Stage IV,continued Virulence factorsmost designed to avoid phagocytosis or survive once ingested Wall components Surrounded by capsule:not as effective as pneumococcus or meningococcus Cell wall murein activates complement by alternative pathway Teichoic acid also activates an

12、d involved in adherence Protein A interferes with opsonization by binding with Fc region of Abcomplement activated primary pathwayLecture 10BIOL 53314Virulence Factors of S.aureus Stage IV,continued Secretion of enzymes Catalasehydrogen peroxide to water and oxygen(all staphylococci produce)Coagulas

13、emakes fibrin clot(wbc penetrate badly;only S.aureus)Hylauronidasedegrades connective tissues(facilitates spread;90%of S.aureus strains)Fibrinolysin(staphylokinase)dissolve fibrin clots(virtually all S.aureus)Lecture 10BIOL 53315Virulence Factors of S.aureus Stage IV,continued Secretion of enzymes L

14、ipasesrequired for invasion into cutaneous and subcutaneous tissues(found in all S.aureus and 30%of others)Nucleaseheat stable(role is uncertain;S.aureus)PenicillinaseLecture 10BIOL 53316Virulence Factors of S.aureus Stage IV,continued Secretion of toxins Cytolytic(membrane-damaging by pores)Alpha,b

15、eta,(sphingomyelinase C),delta,gamma,leukocidin(cannot lyse red blood cells)Others lyse rbc and leukocytes(referred to previously as hemolysins)Cause lysis of neutrophils leading to massive lysosomal enzyme secretionLecture 10BIOL 53317Virulence Factors of S.aureus Stage IV,continued Secretion of to

16、xins Exfoliative toxin(scalded skin syndrome)extrachromosomal Toxic Shock Syndrome toxin-1(enterotoxin F)exotoxin secreted during growth Some produce enterotoxin B instead(role not clear)Lecture 10BIOL 53318Virulence Factors of S.aureus Stage IV,continued Secretion of toxins Enterotoxins(A-E)found i

17、n both S.aureus and S.epidermidis Resistant to hydrolysis by gastric and jejunal enzymes Stable to heating at 100C for 30 minutes Mechanism of toxin activity not understood;no satisfactory animal model Stimulate intestinal peristalsis and have CNS effect;intense vomitingLecture 10BIOL 53319Pathogene

18、sis of S.aureus Treatment Antibiotics Types:Methicillin,oxacillin,nafcillin,and dicloxacillin(semisynthetic penicillins resistant to-lactam hydrolysis)Majority of patients can be treated,but 10-15%S.aureus and 40%coagulase-negative staphylococci are resistant;treat with vancomycinLecture 10BIOL 5332

19、0Pathogenesis of S.aureus Treatment Antibiotics Resistance:Plasmid-borne(hydrolysis of-lactam ring)Chromosomalchange in structure of penicillin-binding proteinsLecture 10BIOL 53321Streptococci Fermentative(oxygen tolerant)Gram+cocci in chains Sensitive to penicillins Human reservoirpassed from perso

20、n to personLecture 10BIOL 53322Streptococci Properties of Lancefield Groups(CHO antigens on wallsee handout)Group A:cross-reaction can lead to:Rheumatic fever GlomerulonephritisLecture 10BIOL 53323Streptococci Recent Group A Streptococcus virulence factors M-like proteinsbind IgM IgG(protease inhibi

21、tor)and alpha2 macroglobulin F proteinadherence to epithelial cells C5a peptidasedegrades C5A pyrogenic exotoxins;previously called erythrogenic toxinsLecture 10BIOL 53324Staph and Strep ToxinsS.aureus toxic shock TSST-1S.pyogenes toxic shock TSSL-1S.pyogenes scarlet feverSPE-1 (children,not adults;

22、immunity)Lecture 10BIOL 53325Staph and Strep ToxinsS.aureus:Toxic Shock Syndrome Fever,diffuse rash Exfoliation of skin on palms and soles of feet Normally doesnt compete well in relatively anaerobic vaginal areaLecture 10BIOL 53326Staph and Strep ToxinsS.aureus:Toxic Shock Syndrome Super-absorbent

23、tampon:Created aerobic pockets Removed Mgproducing toxin After removed tampon,cases declined;did not disappear Still associated with wounds,rare nasal surgeryLecture 10BIOL 53327Staph and Strep ToxinsS.pyogenes:Toxic Shock-Like Syndrome Skin or wound infection-bloodstream Death rate 30%;over 10-fold

24、 higher than TSST Seen in immunocompromised people Also other infections occurred:soft tissue infection with influenza symptoms High fatality rate because rapid development of shock and multiple organ failureLecture 10BIOL 53328Staph and Strep ToxinsS.pyogenes:Toxic Shock-Like Syndrome Features in c

25、ommon with scarlet fever Occur in healthy people Both associated with high fatality rate Produce same exotoxin:streptococcal pyrogenic exotoxin(Spe)Similar in mechanism to TSST-1Lecture 10BIOL 53329Staph and Strep Toxins Comparing TSLS-1 and TSST-1:Rash,fever,shock,multiple organ failure;resemble en

26、dotoxin septic shock Both toxins superantigens Same mechanisms of action Limited similarity at amino acid sequence levelLecture 10BIOL 53330Staph and Strep Toxins TSLS-1 related to erythrogenic toxin(scarlet fever;SpeA)Serotypes:Spe ATSLS or invasive S.progenes Spe B Spe C Some strains dont produce

27、Spe A,so Spe B or Spe C also has roleLecture 10BIOL 53331Staph and Strep Toxins How do TSST-1 and SPE cause shock and multiple organ failure?Hypotheses not mutually exclusiveLecture 10BIOL 53332Shock and Organ Failure First Hypothesis:same as LPS triggering release cytokines IL1,TNF Consistent with

28、role as superantigen Promote association between macrophage and helper T cellsproliferation of T cells producing high IL2 level Secondarily produce IL1 TNF Inject TSST-1 into rabbits;elevated levels IL1 TNFLecture 10BIOL 53333Shock and Organ Failure Second hypothesis:increase bodys sensitivity to LP

29、S;consistent with:Acts synergistically with LPS to amplify toxic effects in vitro and in animals Conceivablelow levels leaching into blood due to lysis of resident microflora Normally no effect Presence of Spe or TSST-1 causes an effectLecture 10BIOL 53334Shock and Organ Failure Evidence to support

30、role for LPS in TSST and TSLS Injecting TSST-1 or Spe is lethal to rabbits Injecting exfolatin and concanavalin A not lethal to rabbits Both elicit T cell proliferation,but dont enhance sensitivity to LPSLecture 10BIOL 53335Shock and Organ Failure Evidence to support role for LPS in TSST and TSLS TS

31、ST-1 not lethal to gnotobiotic animals Wouldnt expect leakage,but still T cell response Therefore,both suggest T cell proliferation not as important as synergy of LPS Not conclusive;difficult to prove same level T cell stimulation,proliferation occurred in all casesLecture 10BIOL 53336Shock and Orga

32、n Failure Third hypothesis:TSST-1 can act directly on endothelial cells Damage causes malfunction in circulatory system,which creates hypotension Data:swelling associated with massive leakage of fluid from capillaries is marked symptom of both TSST and TSLS Could also be result of action of blood ve

33、ssels by cytokines,coagulation,or complement cascadeLecture 10BIOL 53337Staph and Strep Toxins Mortality of S.pyogenes vs.S.aureus TSLS higher than TSS TSLS strains enter bloodstream TSS,only the toxin circulatesS.pyogenes known to be invasive;killed by PMNs and macrophage if ingestedLecture 10BIOL

34、53338S.pyogenes Invasiveness Strategies for evading phagocytosis;(1):M protein binds H factor better than factor B Leads to degradation of C3b Therefore,prevents opsonization by C3b and formation of C3 convertaseLecture 10BIOL 53339S.pyogenes Invasiveness Strategies for evading phagocytosis Data sup

35、porting:M mutants yield more susceptible to phagocytosis;less virulent than wild type Ab against M protective 80 serotypes of M;possibly evades host antibodies by changing serotype;however,no data to support this hypothesisLecture 10BIOL 53340S.pyogenes Invasiveness Strategies for evading phagocytos

36、is;(2):Protease cleaves C5a Chemoattractant stimulates oxidative burst Some activation of complement could occur in spite of M protein because Lysis releases wall components that activate complement Streptococci could protect themselves-C5a peptidase Data supporting:C5a mutants less virulent that wi

37、ld type in animalsLecture 10BIOL 53341S.pyogenes Invasiveness Strategies for evading phagocytosis;(3):M like proteins Sequence and structural similarity to M COOH embedded;NH2 exposed Most similar to M and each other at carboxy end These proteins bind Fc portion of IgG and IgALecture 10BIOL 53342S.p

38、yogenes Invasiveness Strategies for evading phagocytosis M like proteins;possible roles Coat with host proteinless likely detected as invader by complement and immune system Adherence for body cells that contain Ab on surface Also can bind host protease inhibitor such as 2 macroglogulin Host uses pr

39、otease inhibitor to protect against proteases released by phagocytesLecture 10BIOL 53343S.pyogenes Invasiveness Strategies for evading phagocytosis;(4):F proteinbinds fibronectin Adherence of bacteria to tissues Evasion of immune system Summary of invasiveness No direct evidence M-like proteins invo

40、lved in virulence Found in impetigo strains,not always in severe invasive strains Need mutant studies to answer questionsLecture 10BIOL 53344S.pyogenes Virulence Regulation of S.pyogenes virulence genes Expression M,C5a peptidase,and some M-like proteins;regulated at transcriptional level Responds t

41、o CO2 levels Increased CO2 causes increased productionLecture 10BIOL 53345S.pyogenes Virulence Regulation of S.pyogenes virulence genes Regulatory gene mry transcriptional activator;sequence analysis shows it is part of two-component system Sensornot found Activator Also known that speA gene on temp

42、erate phageLecture 10BIOL 53346S.pyogenes Pathogenesis Treatment and prevention TSST,TSLS are medical emergencies Surgical debridement of wounds prevents further production of toxin Antibiotics;penicillin Toxic effects TSST-1 countered by intravenous rehydration;counter hypotensionLecture 10BIOL 533

43、47Streptococcal Treatment Prevention Vaccine possible Target against M Possible problems#serotypes,but severe invasive disease caused by few AB against M cross-reacts with heartLecture 10BIOL 53348Streptococcal Sequellae Hypotheses First:Autoimmune theory Epitopes that cross react with epitopes on c

44、ardiac myosin and sarcolemmal membrane proteins Thus,T cells or antibodies could attack tissue Inflammatory response damages heart valvesLecture 10BIOL 53349Streptococcal Sequellae Hypotheses Glomerulonephritis High levels Ab to streptococcal Ag circulating in blood stream causes AgAb complexes to a

45、ccumulate in kidney Inflammatory response attacks kidney interfering with kidney functionLecture 10BIOL 53350Streptococcal Sequellae Hypotheses Data supporting Ag-Ab complexes visible in people with glomerulonepheritisglomeruli Decrease in C3 and other complement components also seen;supports hypoth

46、esis that inflammatory response is occurring Second:Toxins cause sequellaeLecture 10BIOL 53351Streptococcal Sequellae Hypotheses Main argument against Time lag between initial infection and development of rheumatic fever(RF;several weeks)or glomerulonephritis(10 days)Normally,if due to toxin,within

47、a week Candidates for toxin most likely to cause glomerulonephritis:streptococcal O,streptokinase,or SpeLecture 10BIOL 53352Glomerulonephritis Hypotheses Streptococcal O cytotoxin Mechanism and aa sequence similarity to pneumolysin Pore-forming toxin Injected into lab animals;damages heart Therefore

48、,may have role in RF Also,very immunogenic;maybe Ab damageLecture 10BIOL 53353Glomerulonephritis Hypotheses Streptokinase Plasminogenplasmin Therefore causes symptoms similar to glomerulonephritis in animals Interesting,but not provenLecture 10BIOL 53354Rheumatic Fever Hypotheses Spe RF strains prod

49、uce Spe;others dont Enhances cardiotoxicity caused by Streptococcal O in animals Havent explained long time lagLecture 10BIOL 53355Rheumatic Fever Hypotheses Mysterious feature of RF unexplained Treated with antibiotics for as late as 9 days after symptoms,still protected against RF After 9 days,tox

50、ic products should be circulating and immune response underway Recurrence of disease Normally,infection results from different strain Some result from same strain RF symptoms take as long to develop as in originalLecture 10BIOL 53356Rheumatic Fever Hypotheses Mysterious feature of RF unexplained If