Infection and Bacterial Virulence Factors PDF

INFECTION AND BACTERIAL VIRULENCE FACTORS SHILPA.K MICROBIOLOGY TUTOR AIMSRC INFECTION  INFECTION VS DISEASE Asymptomatic Symptomatic In...

INFECTION AND BACTERIAL VIRULENCE FACTORS SHILPA.K MICROBIOLOGY TUTOR AIMSRC INFECTION  INFECTION VS DISEASE Asymptomatic Symptomatic Infection Hos t Multiplication in host Disea se  WHAT IS INFECTIOUS DISEASE? It applies when an interaction with a microbe causes damage to host and the associated damage or altered physiology results in clinical sign or symptoms of host resulting from infection. SIGNS AND SYMPTOMS?? Signs are objective changes such as rash or fever that a physician can observe. Symptoms are subjective changes in the body functions such as pain or loss of appetite that are experienced by the patient..  TYPES OF HOST ObOlBg i LIaGtAeTE HOS PRPIMriAmRYTary HOS SECONDA TRANSPORT RY T Transpo Seconda rt  CHAIN OF INFECTION Portal of Infectious Portal of Mode of entry agent exit transmission Susceptible Reservoir host  FACTORS INFLUENCING THE OCCURENCE OF INFECTION 1. PORTAL OF ENTRY 2. PORTAL OF EXIT 3. VIRULENCE OF ORGANISM –extent /degree of pathogenicity 4. INFECTIVE DOSE 5. DEFENSIVE POWERS OF THE HOST 6. PRESENCE OF VECTORS/ CARRIER 7. RESERVOIR 8. HYGIENE 9. MALNUTRITION 10. SMOKING AND ALCOHOLISM 11. PREGNANCY 12. EDUCATIONAL BACKGROUND 13. CULTURE  Portal of Entry 1. Mouth (Oral) 2. Anus 3. Ears 4. Nose 5. Eyes 6. Intact skin 7. Open wound 8. Percutaneous bites 9. Vaginal opening 10.Urinary orifice (urethral meatus)  Portal of Exit 1. Mouth (Oral) 2. Anus 3. Ears 4. Nose 5. Eyes 6. Intact skin 7. Open wound 8. Percutaneous bites 9. Vaginal opening 10.Urinary orifice (urethral meatus)  Primar y Colonization Reinfection Latent infection Secondary Levels of infection Sub – cilinical Cross infection infection Iatrogenic infection Nosocomial infection Opportunistic infection  TYPES OF INFECTION ACCORDING TO TIME OF OCCURENCE 1. PRIMARY INFECTION – the first and original infection that makes a person ill. 2. SECONDARY INFECTION – the second infection that follows as a complication of the original infection. 3. INTERCURRENT INFECTION – two different primary infections occurs simultaneously. 4. MIXED INFECTION – two or more infections occurring with a primary and a secondary infection.  TYPES OF INFECTION ACCORDING TO THE EXTENT OF DISTRIBUTION OF EFFECTS IN THE BODY 1. LOCAL/ LOCALIZED INFECTION – occurs when a pathogen remains in a particular site. 2. SYSTEMIC/ GENERALIZED INFECTION – the pathogen or its products is spread in the body through the circulation. 3. FOCAL INFECTION – original site of pathogen remains in an area from which it spreads to other parts and set-up another focus/ center of action.  TYPES OF INFECTION ACCORDING TO SEVERITY 1. CHRONIC INFECTION – infection that has a slow evolution of the disease and usually cures at a longer period. 2. ACUTE – infection with a swift and rapid or severe course of development that usually recovers fast. 3. LATENT INFECTION – infection held in check by the by the defensive forces of the body. 4. SUBCLINICAL/ INAPPARENT INFECTION – type of infection where the signs and symptoms are so mild that it remains undetected or undiagnosed. 5. TERMINAL INFECTION –a complicating infection leading to death  TYPES OF INFECTION ACCORDING TO THE DISTRIBUTION 1. SPORADIC 2. ENDEMIC 3. EPIDEMIC 4. PANDEMIC EPIDEMOLOGICAL BASIS OF DESCRIPTION AND EXAMPLES INFECTION Epidemic infection Epizoonotic & Epornithic (from birds). e.g - Cholera. Endemic infection Hyperendemic (high incidence) Holoendemic (all individuals are affected) (eg. Anthrax, Brucellosis, Tick typhus) Pandemic infection E.g., Influenza pandemic of 1918 and 1957 Sporadic infection Irregular, haphazardly, and time to time Exotic infection Imported to a country where it does not exist COURSE OF INFECTIOUS DISEASE/ STAGES OF DEVELOPMENT OF INFECTION 1. INCUBATION PERIOD – interval between the time the pathogen is received and the appearance of the disease S/S. 2. PRODROMAL PERIOD – a short interval described by such ill-defined symptoms as headache 3. INVASION PERIOD – dse. reaching its full development and maximum intensity either rapid (acute) or insidious (chronic). 4. FASTIGIUM / ACME – dse. at its height 5. DEFERVESCENCE – period of decline either in crisis (fast) or lysis (gradual/ slow) 6. CONVALESCENCE – period of recovery Depending on the mode of transmission it can be, Contagious disease – A disease that is transmitted through physical contact. Examples - rabies, leprosy, trachoma, sexually transmitted disease. Communicable disease – It is an illness due to specific infectious agents or its toxic products capable of being directly or indirectly transmitted from man to man, animal to animal or from the environment (through air, dust, soil, food, water etc) to man or animal.  TRANSMISSION OF INFECTION Three main components that play an important role in successful transmission of microbial disease –  Reservoir  Mode of transmission  Susceptible host The source of infection: It is defined as the person, animal, object or substances from which an infectious agent passes or is disseminated from the host. It is of types: SOURCE DESCRIPTION EXAMPLES Exogeneous source The source of infection is Human, animals, insect, food, from outside host’s water body. Endogeneous The source of infection E.Coli present as normal flora source is the normal flora of the intestine may cause present in the human urinary tract infection in body. same host  RESERVOI R Defined as any person, animal, arthopod, plant, soil or substances (or combination of those) in which an infectious agent multiplies on which it depends primarily for survival or it produces itself in such a manner that it can be transmitted to susceptible host, i.e, reservoir is the natural inhabitants in which organisms multiplies, replicates. Reservoir can be – Human, Animal or Non living object (food, water) Homologous – It is applied when another member of the same species is victim. Examples – Man – V.cholerae Heterologous – When the infections is derived from a  WHO IS CARRIER A carrier is defined as an infected persons or animals that harbours a specific infectious agent in the absence of discernible clinical disease and serve as a potential source of infection for others THE ELEMENTS IN CARRIER STATE:  The presence of disease agent in the body.  The absence of recognizable symptoms and signs of the disease.  The shredding of the disease agent in the discharge or excretion this acting as a source of infection for other person. Examples: Typhoid Mary is a classic examples of carrier.  CARRIER CAN BE CLASSIFIED IN FOLLOWING WAYS Based on type: Based on duration:  Incubatory carrier – Measles,  Temporary carriers – Incubatory, Polio, Pertussis and Convalscent and healthy Influenza carriers  Convalescent carrier -  Chronic carriers – Tyhoid fever, Typhoid Dysentry, Cerebrospinal fever meningitis and Gonorrhoea, syphilis  Healthy carrier ANIMAL RESERVOIR – ZOONOTIC INFECTIONS Bacterial zoonoses Plague, Anthrax, Bovine tuberculosis Viral zoonoses Rabies, Japanese encephalitis Fungal zoonoses Dermatophytic infections Parasitic zoonoses Toxoplasmosis, Cysticercosis Insect vectors – Mosquitoes, Flies, Mites and Ticks Mechanical vector Domestic flies carry enteric bacteria on their leg Biological vector Biological vector ( e.g- rat fleas, female anophales mosqitoes that transmit Plague, Malaria respectively)  MODE OF TRANSMISSION DIRECT MODE EXAMPLES Direct contact. Common cold, Staphylococcal infection, Syphilis, AIDS Inhalation of droplet Tuberculosis, Pertussis. Contact with soil Tetanus, Mycosis Inoculation into skin or mucosa Rabies virus, HIV infection Trans placental infection Treponema pallidum, Rubella, Cytomegalo virus, Toxoplasma gondii. INDIRECT MODE EXAMPLES Vehicle borne Typhoid fever, Cholera Vector borne  Mechanical  Biological (Propagative, Plague bacilli in rat fleas, Malaria Cyclopagative, Cyclo development) parasite in mosquito, Microfilarae in mosquito. Air borne (by droplet nuclei or dust) Tuberculosis, Coccidiomycosis, Q fever. Fomite borne Diphtheria, Typhoid fever. Uncleaned hands and fingers Streptococci, Staphylococcal infection, Typhoid fever, Dyssentery. The pathogen can be transmitted either by vertical or horizontal transmission. Vertical transmission Breast milk Passage through birth Transplacental canal Ex: Group B Streptococci and Listeria monocytogenes cause neonatal sepsis, Staphylococci cause skin and oral infection. Horizontal infection Person to person Contact with air, water, food and Vectors Ex:. Polio, Influenza, Typhoid  SUMMARY OF MODE OF TRANSMISSION OF INFECTION MODE OF DISEASE CAUSATIVE MECHANISM TRANSMISSION ORGANISM HUMAN TO HUMAN A. Direct contact Gonnorrhea N. gonorrhoea Intimate contact. B. Indirect contact Dyssentry Shigella dysenteriae Fecal-oral route C. Trans-placental Congenital syphillis Treponema pallidum Across placentra D. Blood borne Syphillis Treponema Through transfused Blood and intravenous pallidum drug abuse NONHUMAN TO HUMAN A. Animal source Cat stratch fever Bartonella lenselae Bacteria enter in catscratch B. Via insect vector Lyme disease Borrelia Bacteria enter in tick bite C. Through animal Haemolytic uremetic burgdoferri E.coli excreta syndrome. Bacteria in cattle faeces O.157 are ingested in undercooked food  ROUTE OF ENTRY OF MICROBIAL PATHOGEN PORTAL OF BACTERIA VIRUS FUNGUS ENTRY Skin and mucous Clostridium tetani Hepatitis B virus, Dermatophytes membrane Leptospira HIV Respiratory Streptococcus Rhinovirus, Cryptococcus tract pneumoniae, Respiratory neoformans, Neisseria syncytical virus, Histoplasma meningitidis, Influenza virus capsulatum Mycobacterium tuberculosis. Gastro-intestinal tract Shigella sp, Hepatiis A or E Candida albicans salmonella sp,Vibrio virus, Polio virus sp. Genital tract Neisseria HIV, Human Candida albicans gonorrhoea, papilloma virus. Treponema pallidum. http://www.slideshare.net/ Mans Manchester/virulence-123 07872  Depending on duration Acute Chronic infection infection Pattern in the presentation of pathology of infection PATTERN EXAMPLES Toxin mediated disease Diphtheria, Tetanus. Acute pyogenic infection Staphylocccal pharyngitis, Staphylococcal abscess. Sub-acute infection Sub – acute bacterial endocarditis, Atypical pneumonia Chronic granulomatus infection Tuberculosis, Brucellosis BACTERIAL VIRULENCE FACTORS  VIRULENCE FACTORS These are the molecules expressed and secreted by the bacteria May be encoded on chromosomal, plasmid, transposon or temperate bacteriophage DNA Virulence factor genes - integrate into the bacterial chromosome.  - Siderophores Enterotoxin e-_ (diarrhea).....,... - Type1 - fimbriae (adherence) Endotoxin in.. LPS layer (fever) , inv encoded surface appendage; adherence Anti-phagocytic proteins induced \byoxyR Virulence plasmid - - - ,_ Cytotoxin (inhibits host cell protein Vi capsule synthesis; O anligeny Flagellum antigen; calcium influx (inhibits (motility) inhibits H antigen into host; phagocyte complement adherence) killing) (adherence; binding inhibits  TYPES OF VIRULENCE FACTORS  Adherence factors.  Invasion factors.  Capsule.  Toxins.  Iron acquisition. ADHERENCE OR COLONIZATION FACTORS Pathogens and potentially pathogenic commensals adhere to the mucous membrane surfaces with considerable selectivity  Fimbriae.  Slime layer.  Glyco-calyx.  Membrane protein.  Cell bound protein.  Bacterial biofilms. TYPES OF ADHESION MECHANISM EXAMPLES Pillus adhesion These are the main E.coli, Neisseria gonorrhoea, mechanism by which Vibro cholerae. Fimbriae bacteria adhere to host cell. A) Mannose sensitive These are the fibers that fimbriae extends from bacterial surface, mediate attachment B) Mannose-resistant of bacteria to specific fimbriae receptor on host cell TYPES OF NON- ORGANISMS INVOLVED PILLUS ADHESION Haemaglutinin ( filament- Bordetella pertusis, Helicobacter pylori, Salmonella ous , mannose resistant, typhimureum fibrillar) Biofilm CONS, Staphylococci, E.coli, Viridans group of streptococci Curli (surface protein) E. coli, Salmonella, Shigella Fibronectin Streptococcus pyogenes Exopolysaccharide Streptococcus mutans  BIO - FILMS Bio-films are communities of microorganisms in a matrix that joins them together and to living or inert substrates. They are surface-attached communities of bacteria, encased in an extracellular matrix of secreted proteins, carbohydrates, and/or DNA, that assume phenotypes distinct from those of planktonic cells STEPS IN BIOFILM FORMATION  INVASIO N Cell invasion refers to describe the entry of bacteria into host cells, ability to avoid humoral host defense mechanisms and potentially provides a niche rich in nutrients and devoid of comperition from another host. Invasion of the tissue is enhanced by following factors: (1) Invasin; (2) Enzymes; (3) Antiphagocyic factor; (4) Intra-cellular survival. INVASIN: It is the bacterial surface protein that affect physical proportion of tissue matrices , intracellular spaces, thereby promoting the spread of pathogens.  Enzymes: Play an imporant role in-flammatory process. ENZYMES ORGANISMS INVOLVED MECHANISM OF ACTION 1. Hyaluronidase Staphylococci; Group A, B,G Hydrolyse hyaluronic acid thereby streptococci, Clostridium spreading bacteria to spread through perfringenes subcutaneous tissue 2. Collagenase Clostridium perfringenes Hydrolyse collagen thereby spreading bacteria to spread through subcutaneous tissue 3.Coagulase Staphylococcus aureus It convert fibrinogen to fibrin clot, thereby protect bacteria from phagocytosis. 4. Streptokinase Group A, C, G streptococci. Bind to plasminogen and activate the production of plasmin to dissolve blood clot 5. Staphylokinase Staphylococcus aureus Prevent formation of fibrin clot. 6. Lecithinase Clostridium perfringenes Hydrolyse lecithin.desrtoys the integrity of the cytoplasmic membrane of many cells 7. Phospholipase Staphylococcus aureus Lyse red blood cells  ENZYMES ORGANISMS INVOLVED EXAMPLES 8. IgG A1 proteae Staphylococcus aureus Cleaves IgA at specific pro-ser or pro-thr bonds in he hinge region into Fab and Fc fragments (an antibody) 9. Leukocidins Streptococcus pneumoniae, These poreforming exotoxin cause Neisseria sp, Haemophilus degranulation of lysosomes within leukocyte influenzae 10. Porins Staphylococci, Streptococci , Inhibit phagocyosis by activating adenylate pneumococci cyclase system. 11. Protein A Staphylococcus aureus Binds to IgA by its Fc end thereby preventing complement from interacting with bound IgG 12. Dnase Staphylococci; Group A, Lowers viscosity of exudates, giving the streptococci, Clostridium pathogen more mobility. perfringenes 13. Hemolysins Staphylococci, streptococci, Lyse erythrocte, make iron available for E. coli microbial growth 14. Pyogenic Group A streptococci degrades protein. exotoxin B 15. Elastin, Pseudomonas aeruginosa Cleaves laminin associated with basement alkaline protease membrane.  INTRACELLULAR SURVIVAL A few mechanisms that are suggested or the intra – cellular survival of bacteria include – inhibition of phago – lysosome fusion, resisance to action of lysosomal enzymes, adaption to cytoplasmic replication.  Mycobacterium tuberculosis interfere with the formation of phagolysome in a phagocyte. They are able to grow intracellularly in alveolar macrophages. http://www.nature.com/nm/journal/v13/n3/fig_tab/nm0307-2 82_F1.html  TOXINS – derived from Greek (Toxicon) – Bow poison Components or products of microorganisms which, when extracted and introduced into host animals, reproduces disease symptoms normally associated with infection Roux and Yersin – Diphtheria  Endotoxin  Exotoxin  ENDOTOXIN (PFEIFFER – 1893) Toxic lipopolysaccharide components – gram negative bacteria Exhibit profound biologic effect on the host Released mainly during the cell lysis and also during multiplication Basic structure: ‘O’ side Core Lipid chain polysacchar A oligosacchar ide Genus or ide Serotype antigens Toxic Genus specific moiety antigens Biologic activities of lipid A component of endotoxin:  Mitogenic effects on B lymphocytes  Induction of gamma interferon production by T lymphocytes  Activation of the complement cascade with the formation of C3a and C5a  Induction of the formation of interleukin-1, Interleukin-2 and other mediators.  Endotoxin – Lipid A Activation of Activates Activates tissue complements factors macrophages IL - 1 Nitric oxide Coagulation Fever cascade - DIC hypotension TNF C3a C5a Fever & Hypotension Neutrophil Hypotension edema chemotaxis  Exotoxin Neurotoxin Cytotoxin Enterotoxin Gram positive and gram negative species - Soluble protein toxins released from viable bacteria during exponential growth phase Are excellent antigens that elicit specific antibodies called antitoxins Enter eukaryotic cells primarily through receptor mediated endocytosis  Protein synthesis inhibition Damage of cell membrane Elongation factors – Exotoxin A – Enzymatic hydrolysis – α toxin of C.diphtheria C.perfringens Ribosomal RNA – Shiga toxin – Pore formation – α toxin of S. S.dysentriae aureus Second messenger pathways ADP – Ribosylation Adenylate cyclase Deamidation Glucosyl transferase Immune system activation Metallo – proteases Include pyrogenic superantigens TSST – 1 Tetanus toxin – Zinc Scarlet fever toxin protease Botulinum neurotoxin Bacterial exotoxin – AB structure – function properties  A domain – Catalytic domain  B domain – receptor binding domain Fragment Fragmen A tB Ex : Diphtheria toxin  ADP RIBOSYLATION DIPHTHERIA TOXIN 1. Toxin binds to Heparin Binding EGF-like molecule Produced - infected with a 2. Internalized into clathrin coated lysogenic tox+ ß phage pit 3. Uncoated pit – Endosome A holotoxin 4. pH in endosome ↓ 5. Movement of catalytic A into 3 functional regions cytosol. - Receptor binding region. 6. A subunit transfers ADP ribose from NAD to amino - Translocation region-B subunit. acid diphthamide on EF2 which is -Catalytic region-A subunit. required for translocation of mRNA. EF-2 + NAD+ ADPR-EF2 + 7. Protein synthesis inhibition and H+ cell death.  CHOLERA TOXIN 1.B subunit binds to GM1 2.A subunit internalized. 3.A1 has ADP ribose Bacteriophage CTXØ encodes - transfer activity. ctx A and ctx B. 4. ↑ intracellular cAMP Phage binds to toxin co-regulated 5.Activates cAMP dependent pilus (tcp). protein kinase CTX gets integrated into Vibrio 6. Watery diarrhea. cholerae genome.  SHIGA TOXIN Produced by Shigella dysenteriae 1.B subunit pentamer type 1. binds to Gb3. Inactivate ribosomal RNA. 2.Receptor mediated Its an AB toxin. endocytosis. Structure similar to 3.In cytosol splits into Cholera toxin. A1 and A2. 4.A has N-glycosidase- Enterohaemorrhagic E.coli, cleaves O157:H7 E.coli, Citrobacter adenine from 28S freundii produce similar toxins called Shiga-like toxins(formerly called verotoxins). 5.Protein inhibition www.frontiersin. org  BOTULINUM TOXIN Toxin enters bloodstream from mucosal surface or wound Binds to peripheral cholinergic Toxin produced by the nerve bacterium endings Clostridium botulinum Transported to PNS 7 types of toxins (A to G) (Stimulatory motor nerve – toxins A, B, E and F cause endings) illness in humans Inhibits release of Ach The toxin is the most Muscle weakness and Flaccid poisonous substance Paralysis occurs beginning known with cranial nerves and progressing High lethality downward http://pharmatips.doyouknow.in/Articles/Botulinum-T oxin.aspx  CLOSTRIDIUM PERFRINGENS TOXIN Produces a wide array of exo-toxins Gas gangrene – Caused by α-toxin produced commonly in Type A strain of Cl. perfringens – Results from the contamination of wounds as in Tetanus Food Poisoning – Raw meat may contain spores of Cl. perfringens – which when not sterilized and is subsequently kept in room temperature for 2 hrs after cooking, Clostridia multiply – Reaches enormous numbers in the intestine and begin to sporulate – Enterotoxin is released during the sporulation  ANTHRAX TOXIN Toxin produced by Bacillus anthracis Toxin consists of three In humans - cutaneous, pulmonary thermolabile and intestinal anthrax components Factor 1 Factor 2 Edema factor Edema factor Factor 3 Lethal factor They are non toxic individually but yield the following results in combination: PA+LF PA+EF PA+LF+EF LF+EF Lethal activity Edema Edema & inactive necrosis - Lethal  TOXIC SHOCK SYNDROME TOXIN Formerly called Pyrogenic exotoxin. Chromosomally encoded. Massive immune activation and pyrogenicity - Superantigens. Similar mechanism- – Scarlet fever toxin – Staphylococcus enterotoxins http://www.e-biomedicine.com/article/S2211-8020(12)00079-4/images  Toxin Type of Toxin Clinical Manifestation Anthrax Cytotoxin Edematous Papule Enteritis, Bloody Diarrhea Botulinum Neurotoxin Flaccid Paralysis Tetanospasmin Neurotoxin Spastic Paralysis Cholera toxin Enterotoxin Watery Diarrhea Shiga toxin Enterotoxin Dysentry, HUS Diptheria toxin Cytotoxin Pseudomembrane Papule Toxic Shock Syndrome Toxin Superantigens Fever, Hypotension, Erythematous rash, MOF, Hypovolumic Shock Scarlet Fever Toxin Superantigens Erythematous Rash, ‘Strawberry tongue’ Scalded skin syndrome toxin Superantigens Perioral erythema, Cutaneous blisters Staphylococcal  - toxin Cytotoxin Disrupts smooth muscles of blood vessels, Cytotoxic – RBCs, platelets, monocytes, etc  OTHER TOXINS Bacillus cereus Produces two enterotoxins - Gastroenterites Heat stable - causes the emetic form of the disease Heat labile – Stimulates adenylate cyclase - Increase in cAMP concentration - Profuse watery diarrhea Staphylococcal 8 serologically distinct enterotoxins - A-E,G,I enterotoxins 3 subtypes of Enterotoxin C Preformed toxins Enterotoxin A is most commonly associated with disease Enterotoxins C and D – found in contaminated milk Enterotoxin B causes pseudomembranous enterocolitis Inflammatory mediators - vomiting charecteristic of Staphylococcal food poisoning. Clostridium diffi cile 2 toxins A and B – structurally related In vivo only Toxin A has enterotoxic activity Toxin B is cytotoxic only in the presence of Toxin A Alterations of target cell’s cytoskeleton Commonest cause of pseudomembranous colitis  Regulation of virulence factor The signal (enviromental signal often called expression of the virulence genes). Common signal include temperatue, iron availability, osmolarity ,growth phase, pH, specific ions(Ca2+) or other nutrient factors and quorum sensing. REFERENCES 1.: Mandell, G. L., Benett, J. E., Dolin, A. : Molecular prospectives of pathogenecity. In : David A. R., Stanley Fmandell. Editors :Mandell, Douglas and Benett ‘s Principles and practice of infectious diseases ; 7th ed. Philadelphia: Elsevier ; 2010.p 3-14. 2. Levinson, W. : Pathogenesis. Review of medical microbiology and immunology.12th ed. New York: Mc Graw Hills; 2012.p 31-51. 3. Greenwood, D., Slack, B. C. R., : Peutherer. Bacterial pathogenicity. 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