2Manifestations of infectious disease ClassicSignsFever, swelling, rashes, vomiting, diarrheaSkin signs: lesions, erythema, papule (pimple), vesicles, pustule, ulcer or erosion or abscessSymptomsPain, headache, nausea, malaisInflammationResult of Immune reactionsHematologic ( leukocytosis, anemia )Cardiac (tachycardia to heart failure)Respiratory (hyperventilation)RenalHepaticUpper GI bleeding
3Manifestations of infectious disease Table 1 Types of skin lesionsFlat lesions (in the plane of the skin)Elevated lesions (above the plane of the skin)Depressed lesions (below the plane of the skin)Macule IInfarct Sclerosis• Telangiectasis†Vesicle and bulla Pustule Abscess‡ Cyst‡ Papule Wheal plague Nodule‡ Vegetation Keratosis Desquamation (scales) Exudate• (crusts) LichenificationAtrophy§ Sclerosis§ Erosion Excoriation Scar† Ulcer Sinus‡ Gangrene§• May also be below the plane of skin † May also be above the plane of skin ‡ May also be in or below the plane of skin § May also be in the plane of skinClassicSignsFever, swelling, rashes, vomiting, diarrheaSkin signs: lesions, erythema, papule (pimple), vesicles, pustule, ulcer or erosion or abscessSymptomsPain, headache, nausea, malaiseInflammation
4Flat lesionMACULEA macule is a change in the color of the skin. It is flat, if you were to close your eyes and run your fingers over the surface of a purely macular lesion, you could not detect it. A macule greater than 1 cm. may be referred to as a patch.
5Elevated lesion PAPULE is a solid raised lesion that has distinct borders and is less than 1 cm in diameter. Papules may have a variety of shapes in profile (domed, flat-topped, umbilicated) and may be associated with secondary features such as crusts or scales.
6Elevated lesionTUMORis a solid mass of the skin or subcutaneous tissue; it is larger than a nodule.
7Elevated lesion PAPULE is a solid raised lesion that has distinct borders and is less than 1 cm in diameter. Papules may have a variety of shapes in profile (domed, flat-topped, umbilicated) and may be associated with secondary features such as crusts or scales.
8Depressed lesion ATROPHY Atrophy is thinning or absence of the epidermis or subcutaneous fat.
9Depressed lesion EROSION Erosions are slightly depressed areas of skin in which part or all of the epidermis has been lost
10Depressed lesion ULCERATION occur when there is necrosis of the epidermis and dermis and sometimes of the underlying subcutaneous tissue.
11FEVER1. Fever increases the environmental temperature above the optimum growth temperature for many microorganisms. If the microorganisms are growing more slowly, the body's defenses have a better chance of removing them all.2. Fever leads to the production of heat shock proteins that are recognized by some intraepithelial T-lymphocytes (delta gamma T-cells) resulting in the production of inflammation-promoting cytokines.3. Fever elevates the temperature of the body increasing the rate of enzyme reactions, and speeding up metabolism within the body.can increase the production and activity of phagocytes,speed up the multiplication of lymphocytes,increase the rate of antibody and cytokine production,increase the rate at which leukocytes are released from the bone marrow into the bloodstream, and speed up tissue repair. Too high of a body temperature, however, may cause damage by denaturing the body's enzymes.
12FEVER Fever may have certain signs in relation to its course. Fever in infectious diseases usually is of short durationLong duration (weeks or months) is always a very serious problem. If it is not possible to determine the cause of fever at the beginning, it is called the fever of unknown origin (FUO). This term is used to describe fever lasting at least 2 weeks, reaching temperatures above 38,2 , and the cause of the origin is uncertain.Fever may last long in some infections with subacute or chronic course.
13Stages in the Progression of Disease No signs or symptomsProdormal illnessMild signs or symptomsSome chilling occurAcute identifiable signs and symptomsIntermittent feverRecoveryAction of immune systemAction of antibioticsConvalescence
17Manifestations of infectious disease Result of Immune reactionsHematologic ( leukocytosis, anemia )Cardiac (tachycardia to heart failure)Respiratory (hyperventilation)RenalHepaticUpper GI bleeding
18Case study 1 S. T. was seen by you in the Emergency Room in December 23 y/o medical student in Southern Californiac/o sudden onset of fever, chills, malaise, headache, myalgia, sore throat, runny nose, sneezingRoom-mate has same symptomsExam: erythematous, inflammed tonsils,no pharyngeal exudatesThroat culture: Group A streptococci
20Case study 2 P. A. is a patient in the Intensive Care Unit 65 y/o man Intubated, on respirator: good oxygenationNurse says that he hasn’t had fever or purulent sputumExam: clear breath sounds, no rhonchi nor ralesCXR: clear without infiltrates or effusionsSputum Gram stain: mixed flora with Gram positive cocci; thin, long Gram negative rodsSputum culture: normal respiratory flora, Pseudomonas aeruginosa
21Case study 3 T. M. was referred to you by the Public Health Department 38 y/o womanPrivate cook in ManhattanIn the past 10 years, 7 of the 8 families she has worked for have had outbreaks of illness:Fever, malaise, headache, myalgia, maculopapular rash, bradycardia, constipation, bloody diarrheaT. M. denies h/o similar illness and denies current symptoms“But, Doctor, I’m not sick!”
23Disease state: complex interaction between pathogen and host 1. If a bacterium is present, is it causing disease?a. Normal florab. Colonizationc. Carrier stated. Infection:i. Asymptomaticii. Symptomatic2. Is the bacterium capable of causing disease?a. Nonpathogenb. Opportunistic pathogenc. Primary pathogen
24Case study 1: Viral pharyngitis + Group A strep normal respiratory flora S. T. was seen by you in the Emergency Room in December23 y/o medical student in Southern Californiac/o sudden onset of fever, chills, malaise, headache, myalgia, sore throat, runny nose, sneezingRoom-mate has same symptomsExam: erythematous, inflammed tonsils,no pharyngeal exudatesThroat culture: Group A streptococci
25Case study 2: Colonization with Pseudomonas aeruginosa P. A. is a patient in the Intensive Care Unit65 y/o manIntubated, on respirator: good oxygenationNurse says that he hasn’t had fever or purulent sputumExam: clear breath sounds, no rhonchi nor ralesCXR: clear without infiltrates or effusionsSputum Gram stain: mixed flora with Gram positive cocci; thin, long Gram negative rodsSputum culture: normal respiratory flora, Pseudomonas aeruginosa
26Case study 3: Typhoid Mary Salmonella typhi carrier T. M. was referred to you by the Public Health Department38 y/o womanPrivate cook in ManhattanIn the past 10 years, 7 of the 8 families she has worked for have had outbreaks of illness:Fever, malaise, headache, myalgia, maculopapular rash, bradycardia, constipation, bloody diarrheaT. M. denies h/o similar illness and denies current symptoms“But, Doctor, I’m not sick!”
30Virulence Factors that Promote Colonization and Invasion Virulence factors that damage the hostExotoxinsEndotoxinsAbility to resist innate immunityAbility to evade adaptive immunityAbility to induce autoimmune response
31Virulence Factors that Promote Colonization and Invasion Basic requirements: receptor + adhesinReceptorSpecific carbohydrate or peptide residues on the cell surfaceAdhesin or adherence factorA macromolecular component of the bacterial cell surface interacting to the receptor
32Virulence Factors that Promote Colonization and Invasion Surface proteins called adhesins in the bacterial cell wall bind to receptor molecules on the surface of a susceptible host cell enabling the bacterium to make intimate contact with the host cell, adhere, colonize, and resist flushing.
33Virulence Factors that Promote Colonization and Invasion Specific adherence of bacteria to cell and tissue surfacesTissue tropismStrep mutans in dental plaque but not in the tongueSpecies specificityNeisseria gonorrheae limited to humansGenetic specificity within a speciesMechanism of specific adherenceReversible attachment – “docking”Non-reversible attachment – “anchoring”
34Virulence Factors that Promote Colonization and Invasion: Example (Tabulate according to the ff:Bacterium:Adherence Factor:Receptor (optional):Attachment Site: Disease)Streptococcus pyogenes:Protein FAminoterminus of fibronectinPharyngeal EpitheliumSore Throat
36Virulence Factors that Promote Colonization and Invasion: FimbriaeAdhesinsProtein FCapsulesInvasinsCleaves secretory IgA (Glycosyl transferase)Spreading factors:Hyaluronidase – attacks the interstitial cement of connective tissue by depolymerizing hyaluronic acidCollagenaseNeuraminidaseStreptokinase and staphylokinaseSiderophoresLow molecular weight compounds that chelate iron with very high affinityCompeting for iron and other nutrients
37Virulence Factors that Promote Colonization and Invasion
38Virulence Factors that Promote Colonization and Invasion
39Virulence Factors that Promote Colonization and Invasion GlycocalyxPolysaccharide or peptide slimeCapsuleSlime layerFunctions:Resists phagocytosisEnhanced attachment
40Virulence Factors that Promote Colonization and Invasion A proposed model for invasion of epithelial cells of the colon. 1) The Shigella first cross the mucosa by passing through specialized cells called M cells. The M cell passes the Shigella on to a macrophage from which it subsequently escapes - possibly by inducing apoptosis, a programmed cell suicide. 2) The Shigella then uses its invasins to enter the mucosal epithelial cells from underneath. The invasins cause actin polymer rearrangements in the cell's cytoskeleton resulting in the bacterium being engulfed and placed in an endocytic vesicle in a manner similar to phagocytic cells. Once inside, the Shigella escape from the vacuole into the cytoplasm and multiply. 3) The Shigella are able to move through the host cell and spread to adjacent host cells by a unique process called actin-based motility. In this process, actin filaments polymerize at one end of the bacterium, producing comet-like tails that propel the Shigella through the cytoplasm of the host cell. 4) When they reach the boundary of that cell, the actin filaments push the Shigella across that membrane and into the adjacent cell.Shigella Passing Through the Mucous Membrane and Invading Mucosal Epithelial Cells
41Virulence Factors that Promote Damage to the Host: EXOTOXINS PropertiesSecreted during exponential growthProtein toxinsHigh biological activityExhibits specificity of actionComponentsA = activeB = binding
43Binding and Entry of an A-B Toxin A-B toxins consist of two parts, an A (active) component and a B (binding) component. The B component of the exotoxin binds to a receptor on the surface of a susceptible host cell. The exotoxin now enters the host cell, in this case by endocytosis, and causes harm by inactivating a host cell target protein through ADP-ribosylation.
44Virulence Factors that Promote Damage to the Host: EXOTOXINS Based on structureA-B prototypeBotulinum toxin, diphtheria toxin, shiga toxin, tetanus toxinMembrane disrupting toxinLacks A & BPore formingPhospholipaseSuperantigens
45Superantigens 1. Some exotoxins are superantigens 2. Produced by bacteria and viruses3. Action: polyclonal stimulation of subset of lymphocytes to divide and produce cytokines4. Best known example: Staph Toxic Shock Syndrome Toxin-1 (TSST-1)5. Also Strep exotoxins6. Pyrogenic toxins cause fever (unlike other exotoxins)
462-subunit A-B exotoxin Neurotoxin: Clostridium botulinum Murray, P.R. et al. Medical Microbiology, 3rd edition, 1998, p. 156
47Botulism Exotoxin Blocking Acetylcholine Release The botulism exotoxin binds to the presynaptic neuron and blocks its release of acetylcholine. This causes a flaccid paralysis, a weakening of the involved muscles.
49Virulence Factors that Promote Damage to the Host: EXOTOXINS Based on modes of actionBreaks down cellsAlpha toxins, hemolysins, leukocidinsEnhance microbial spreadSpreading factors: hyaluronidase, mucinase etcInterfere in cellular metabolismTetanus toxin, botulinum toxin
50Virulence Factors that Promote Damage to the Host: EXOTOXINS 3 ways this can contribute to the progression of disease:Ingestion of preformed toxinColonization of wound or mucosal surface followed by exotoxin productionColonization of wound followed by local exotoxin production
52Evasion of host immune response: IgA protease 1. Cleaves IgA, which is important for mucosal immunity2. An enzyme produced by Neisseria gonorrhoeae, Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae
53Requirement for iron 1. Most iron in the body is intracellular In hemoglobin and myoglobin2. There is very little free ironExtracellular iron is bound to transferrin (in plasma) and lactoferrin (in milk and other secretions)3. Some bacteria produce siderophores to capture iron e.g. Escherichia coliSiderophores bind iron with high affinity
54Virulence Factors that Promote Damage to the Host: ENDOTOXINS Outer membrane of the gram negative cell wallLipid A:polysaccharide:O antigenToxicity is associated with Lipid AImmunogenicity is associated with the polysaccharide componentLess potent, less specificDoes not form antitoxinReleased when the bacterial cell is damaged
58Bacterial Pathogenesis 1. Microbial pathogens and their hosts have often co-evolved2. Clinical diseasea. Non-adapted host/pathogenb. May promote pathogen’s survival and transmissionc. Can result from host response to pathogen3. Extracellular bacteria produce toxins and enzymes
59Bacterial Pathogenesis 4. Bacteria secrete proteins into host cells to modify host cell function5. Intracellular bacteria must bind, enter and survive inside host cells6. Pathogenic bacteria can evade the host immune response and have mechanisms for antibiotic resistance7. Expression of virulence factors is often regulated in response to the environment and other signals
60Bacterial Pathogenesis: Concepts 1. Virulence genes that encode virulence factorsA virulence gene confers on a bacterium the ability to cause diseasePathogenic strains have acquired virulence genes that allow them to exploit the host as an environmental nicheExamples of virulence factors are toxins, enzymes, type III secreted proteins, adhesins, siderophoresVirulence factors are obvious targets for prevention or treatment strategies
61Bacterial Pathogenesis: Concepts 2. Bacteria have found many way to modulate host cell functionExotoxins and type III secreted proteins are virulence factors with specific functions such as to kill host cells or induce the uptake of bacteria by the host cellKnowledge of these mechanisms can help explain the clinical disease caused by a particular bacterium, and the basis for prevention and treatment strategies
62Bacterial Pathogenesis: Concepts 3. Toxins vs. toxoids vs. antitoxin (antitoxoid)Toxins are made by bacteria and have harmful effects on host cellsA toxoid is the inactivated form of an exotoxin that can be used as a vaccine to elicit an immune responseToxoids were traditionally inactivated by heat or formaldehyde, but now can be genetically engineeredAntitoxin is the antisera produced in response to the toxoid (can be from animals or humans) and can be given as treatment
63Bacterial Pathogenesis: Concepts 4. Mechanisms of pathogenesis are conserved among bacteriaVirulence genes that provide a selective advantage are spread among different bacterial genera and species by horizontal transferThese virulence genes are often located on mobile DNA elements such as plasmids or bacteriophages
65AntibioticsAntibiotics and vaccines are among the biggest medical advances since (Culver Pictures)For lecture onlyBC Yang
66A brief history of antibiotics 1495, mercury to treat syphilis.1630, quinine (chinchona tree) for malarial fever by South American Indians.1889, Buillemin defined antibiosis.1910, Paul Ehrlich developed arsenical compound (Salvarsan) for syphilis, term: the chemical knife.1929, Alexander Fleming found penicillin.1935, Gerhard Domagk showed the value of sulfonamides.1940, Ernst Chain and Howard Flory demonstrated the effect of penicillin., then searching for new antibiotics~ recent year: modifying old drugs, finding new discipline in antibacterial combatsEarly time in war: thanks penicillin, we can go home nowNow a day……….Oh eh?!
67Thanks to work by Alexander Fleming ( ), Howard Florey ( ) and Ernst Chain ( ), penicillin was first produced on a large scale for human use in At this time, the development of a pill that could reliably kill bacteria was a remarkable development and many lives were saved during World War II because this medication was available.E. ChainH. FloreyA. Fleming
68A tale by A. FlemingHe took a sample of the mold from the contaminated plate. He found that it was from the penicillium family, later specified as Penicillium notatum. Fleming presented his findings in 1929, but they raised little interest. He published a report on penicillin and its potential uses in the British Journal of Experimental Pathology.
69An ideal antibiotic Broad-spectrum Does not induce resistance Selective toxicity, low side effectsPreserve normal microbial flora
70Definitions Antimicrobial Antibacterial Antibiotic Inhibits growth of micro-organismsAntibacterialInhibits growth of bacteriaAntibioticMade by other micro-organismsUsually extended to include synthetic drugs
71Susceptibility test Tube dilution method Disk diffusion method Minimal inhibitory concentration (MIC): the smallest amount of chemotherapeutic agent required to inhibit the growth of organism in vitroDisk diffusion methodZone of inhibition (ZOI): the correlation of ZOI and MIC has been established by FADETest. This commercially-prepared strip creates a gradient of antibiotic concentration when placed on an agar plate
72Bacteriostatic vs Bactericidal Reversible inhibition of growthWhen the antibiotic is removed, almost all of the bacteria can replicateBactericidalIrreversible inhibition of growthWhen the antibiotic is removed, almost none of the bacteria (10-7 to 10-3) can replicate
73Guidance of antimicrobial therapy Minimum inhibitory concentration: lowest concentration of antibiotic that inhibits visible growthMinimum bactericidal concentration: lowest concentration of antibiotic that kills 99.9% of the inoculumSerum bactericidal title: dilution of serum that kills 99.9% of the inoculumSynergy test: synergistic activity of multiple antibiotics
74Use of antibiotics; is it properly applied? Acute infections in outpatientsAcute infections in hospitalized patientsChronic infection (tuberculosis, AIDS)Agriculture/veterinary medicine
75In vitro: Factors for optimal antibiotic action pH of environment:Nitrofurantoin is more active in acid pH; sulfonamides and aminoglycoside are more active in alkaline pH.Components of medium:Anionic detergents inhibit aminoglycosides, serum proteins bind to penicillin in varying degrees.Stability of drug:Aminoglycosides and chloramphenical are stable for long period in vivo.Size of inoculums:The larger the bacterial inoculum, the greater the chance for resistnat mutant to emerge.Metablic activity of microorganisms:Actively and rapidly growing organisms are more susceptible to drug actionBC Yang
76Affecting factors in vivo Abscess: circulation is blocked off.Foreign bodies: obstruction of the urinary, biliary or respiratory tracts etc.Immunity.
78Modes of action (1)Inhibitors of cell wall synthesis. Penicillins, cephalosporin, bacitracin, carbapenems and vancomycin.Inhibitors of Cell Membrane. Polyenes - Amphotericin B, nystatin, and condicidin. Imidazole - Miconazole, ketoconazole and clotrimazole. Polymixin E and B.Inhibitors of Protein Synthesis. Aminoglycosides - Streptomycin, gentamicin, neomycin and kanamycin. Tetracyclines - Chlortetracycline, oxytetracycline, doxycycline and minocycline. Erythromycin, lincomycin, chloramphenicol and clindamycin.vancomycinAmphotericinAminoglycosidesTetracyclinesFor lecture onlyBC Yang
79Modes of action (2)Inhibitors of metabolites (Antimetabolites). Sulfonamides - Sulfanilamide, sulfadiazine silver and sulfamethoxazole. Trimethoprim, ethambutol, isoniazid.Inhibitors of nucleic acids (DNA/RNA polymerase). Quinolones - Nalidixic acid, norfloxacin and ciprofloxacin. Rifamycin and flucytosine. rifamycinFor lecture onlyBC Yang
80Resistance Natural (inherent) resistance Structural barrel Lack of targetTransport systemAcquired resistanceMutationGene exchange (conjugation in most)
81Transferable antibiotic resistance in bacteria Reduced uptake into cell (chloramphenicol)Active efflux from cell (tetracycline)Modification of antibiotic targets (b-lactam, erythromycin)inactivation of antibiotic by anzymic modification: hydrolysis (b-lactam, erythromycin); derivatization (aminoglycosides)Sequestration of antibiotic by protein binding (b-lactam)Metabolic bypass (sulfonamides)Overproduction of antibiotic target (titration: sulfonamides)
82Spread of resistance In most: Day-care, nursing homes, correctional facilitiesSanitation, animal feeds (fecal-oral)Sexual/ Respiratory transmissionInternational travelImmunosuppression
83Some probable overuse/misuse of antibiotics Prophylatic use before surgeryEmpiric use (blinded use)Increased use of broad spectrum agentsPediatric use for viral infectionsPatients who do not complete course (chronic disease, eg. TB, AIDS)Antibiotics in animal feedsFor lecture onlyBC Yang
84Policy to deal drug resistance (1) Ideally, bacteriological management of clinical infection should involve:Identification of causative organismSensitivity testFollow-up the drug effectMonitor antibiotic level to avoid toxicity.In reality, most patients requiring antimicrobial therapy are treated empirically. In serious infections immediate chemotherapy may be life-saving.
85Policy to deal drug resistance (2) Periodic changes of antibiotics used might change selective pressure and thus avoid the emergence of resistance and retain the therapeutic value of antibiotics over a longer period.The unnecessary prophylactic or animal feeds use should be discouraged.Distribution of information on current/updated infectious microbes (consult microbiologists): use more targeted antibioticsPatient education
86New antibiotics development Pharmaceutical industry putting resources back into discoveryLiaisons with university researchesDiscoveries in microbial physiology and genetics offering new targets, new disciplinesCombinational chemistry (mass screening)For lecture onlyBC Yang