1、Introduction to infectious diseasesGang XINDepartment of Microbiology and ImmunologygxiermsInfectiology Infection Infectious diseasesInfectiologist Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi; the disease can be spread direc

2、tly or indirectly, form one person to another.Infectious diseasesCommunicable diseasesWound infectionlung infectionOutlinePathogenHost Pathogenesis of infectionClassification of infectionClinical manifestationsLaboratory diagnosis of infectious diseasesTreatment and preventionpathogenTypes of pathog

3、ensSubcelluarProkaryotic Viruses, prionBacterial, chlamydiae, rickettsiae, mycoplasmasEukaryotic Protozoa, fungi, helminthes, arthropodsprionA prion is an infectious agent composed of protein in a misfolded form Disease:Bovine spongiform encephalopathyMadcow disease(MCD)VirusesThe term virion (plura

4、l virions) is also used to refer to a single, stable infective viral particle that is released from the cell and is fully capable of infecting other cells of the same type A virus is a small infectious agent that can replicate only inside the living cells of organisms. Bacteria (singular: bacterium)

5、chlamydiaechlamyd-, mantle (a cloak) Chlamydia infectionchlamydia conjunctivitisor trachoma Symptoms of Scrub typhusfeverheadachemuscle paincoughgastrointestinal symptomshemorrhaging and intravascular coagulation.maculopapular rash, eschar（焦痂）, splenomegaly and lymphadenopathies are typical signs. /

6、news/Detail/13203.htmlSpirochetesyphilisSaddle nose Fungi (singular: fungus)Tinea (=ringworm ) of skinTinea pedisTinea manusTinea crurisGroup of extremely small single cell (unicellular) or acellular organisms that are found in moist soil or water. They tend to exist as parasites, living off other l

7、ife forms. Protos (First) and zoon (animal)protozoa (singular: protozoon)helminths are worm-like organisms (Parasitic worms) that live and feed off living hosts, receiving nourishment and protection while disrupting their hosts nutrient absorption, causing weakness and disease. helminthsHelmins = wo

8、rmHookworms attached to the intestinal mucosa.Pathogen factorspathogenicityvirulenceis the ability of a pathogen to produce an infectious disease in an organism. The virulence factors of bacteria Methods by which bacteria cause disease AdhesionColonizationInvasionImmune response inhibitorsToxins1234

9、5invasionminimum lethal dose (MLD) the smallest amount of toxin that will kill an experimental animal.Minimum infective dosemedian infective dose (ID50) the amount of pathogenic microorganisms that will cause infection in 50 per cent of the test subjects. infective dose that amount of pathogenic org

10、anisms that will cause infection in susceptible subjects.Host factorssusceptibilitydispositionImmune systemAntibody, immunoglobulinIceberg concept of infectionInfectious disease spectrumIf a large number of individuals are equally exposed to an infectious agent, they do not all respond in the same m

11、anner. In fact, there may be a broad range of responses: Some do not become infected at all Some become infected but develop no symptoms Some become infected and develop mild or moderate symptoms Some become infected and develop severe symptoms Some die as a result of their infectionPathogenesis of

12、infectionClinical manifestations of infectious diseasesNon-specificOrgan system-basedFeverAnorexiaFatigueMuscle achesSkin rasha state of physical and/or mental weakness Loss of appetite Mary Mallon was an asymptomatic carrier of typhoid fever. Over the course of her career as a cook, she infected 53

13、 people, three of whom died.Host-Pathogen Interactions: Symbiotic RelationshipsMutualismCommensalismParasitismNeutralismA symbiotic relationship in which both species benefit A symbiotic relationship in which one organism derives benefit and the other is unharmed A symbiotic relationship in which on

14、e species, the parasite, benefits at the expense of the other, the host The state of being neutral; neutrality prefix, a variant of syn- before b, p, and m=Together = Life; living organism airborne infection droplet infectionvector-borne infection waterborne infectionbloodborne infectionMode of infe

15、ctionSneezing can spread the flu virus to other people.airborne infection one that is contracted by inhalation of microorganisms or spores suspended in air on water droplets or dust particles.droplet infection infection due to inhalation of respiratory pathogens suspended on liquid particles exhaled

16、 by someone already infected (droplet nuclei) .vector-borne infection infection caused by microorganisms transmitted from one host to another by a carrier, such as a mosquito, louse, fly, or tick.waterborne infection infection by microorganisms transmitted in water.Classification of infections 1Type

17、 of the pathogenDegree of involvementBacterial, viral, fungal, parasiticLocal/focal, generalizedManner acquiredCommunity, hospital/nosocomialClassification of infections 2Type of occurrenceEndogenous vs. exogenousAutoinfection vs. cross-infectionSuperinfection vs. reinfectionsepsisOpportunistic infe

18、ctionan infection caused by an infectious agent that is already present in the body, but has previously been inapparent or dormant.an infection that develops from bacteria normally outside the body that have gained access to the bodyan infection caused by a disease agent that is already present in t

19、he body an infection by an organism that does not ordinarily cause disease but becomes pathogenic under certain circumstances (e.g., impaired immune responses).the transmission of a communicable disease from one person to another because of a poor barrier protection an infection following a previous

20、 infection, especially when caused by microorganisms that have become resistant to the antibiotics used earlier a second infection by the same microorganism, either after recovery or during the original infection 12345678a bacterial infection in the bloodstream or body tissues Cross-infectionExogeno

21、us infectionEndogenous infectionOpportunistic infectionReinfectionSuperinfectionAutoinfection Sepsis Laboratory diagnosis of infectious diseasesGold standard testproceduresMicroscopy and Staining proceduresCulture and sensitivitySerologic testStaining proceduresUrinalysis and fecalysisSpecimen smear

22、 (blood, stool)Gram StainingZeihl-Neelson stainKOH (potassium hydroxide) test for fungiGram StainingGram stain a staining procedure in which microorganisms are stained with crystal violet, treated with strong iodine solution, decolorized with ethanol, and counterstained with a contrasting dye; those

23、 retaining the stain are gram-positive, and those losing the stain but staining with the counterstain are gram-negative.Zeihl-Neelsen stainThe Ziehl-Neelsen stain, also known as the acid-fast stain, was first described by two German doctors; Franz Ziehl (1859-1926), a bacteriologist and Friedrich Neelsen (1854-1898), a pathologist. It is a special bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria. Specimens mounted