1、Introduction to infectious diseases,Gang XINDepartment of Microbiology and I18923912518,terms,Infectiology,Infection,Infectious diseases,Infectiologist,Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi; the disease can be spread directly or in
2、directly, form one person to another.,Infectious diseases,Communicable diseases,Wound infection,lung infection,pathogen,host,Outline,PathogenHost Pathogenesis of infectionClassification of infectionClinical manifestationsLaboratory diagnosis of infectious diseasesTreatment and prevention,pathogen,Ty
3、pes of pathogens,eu-, Good; well; true,pro-, before,karuo-, nut or cell nucleus,Types of pathogens,Subcelluar,Prokaryotic,Viruses, prion,Bacterial, chlamydiae, rickettsiae, mycoplasmas,Eukaryotic,Protozoa, fungi, helminthes, arthropods,prion,A prion is an infectious agent composed of protein in a mi
4、sfolded form,Disease:Bovine spongiform encephalopathy,Madcow disease(MCD),Viruses,The term virion (plural 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 infec
5、tious agent that can replicate only inside the living cells of organisms.,Bacteria (singular: bacterium),chlamydiae,chlamyd-, mantle,(a cloak),Chlamydia infection,chlamydia conjunctivitis,or trachoma,rickettsiae,The genus Rickettsia is named after H. T. Ricketts (18711910), who studied Rocky Mountai
6、n spotted fever, and eventually died of typhus after studying that disease.,rickets, vitamin D deficiency,Disease:spotted fever, typhus and scrub typhus,Tick hemolymph cells infected with R. rickettsii. From the CDC.,Symptoms of Scrub typhus,feverheadachemuscle paincoughgastrointestinal symptomshemo
7、rrhaging and intravascular coagulation.maculopapular rash, eschar（焦痂）, splenomegaly and lymphadenopathies are typical signs.,http:/ (fungus) and plasma (formed),Spirochete,syphilis,Saddle nose,Fungi (singular: fungus),Tinea (=ringworm ) of skin,Tinea pedis,Tinea manus,Tinea cruris,Group of extremely
8、 small single cell (unicellular) or acellular organisms that are found in moist soil or water. They tend to exist as parasites, living off other life forms.,Protos (First) and zoon (animal),protozoa (singular: protozoon),helminths are worm-like organisms (Parasitic worms) that live and feed off livi
9、ng hosts, receiving nourishment and protection while disrupting their hosts nutrient absorption, causing weakness and disease.,helminths,Helmins = worm,Hookworms attached to the intestinal mucosa.,arthropods,Greek arthron, joint, and pods foot, which together mean jointed feet”,Pathogen factors,path
10、ogenicity,virulence,is the ability of a pathogen to produce an infectious disease in an organism.,The virulence factors of bacteria,Methods by which bacteria cause disease,Adhesion,Colonization,Invasion,Immune response inhibitors,Toxins,12345,The virulence factors of bacteria,Adhesion. Many bacteria
11、 must first bind to host cell surfaces. Colonization. Some virulent bacteria produce special proteins that allow them to colonize parts of the host body. Invasion. Some virulent bacteria produce proteins that either disrupt host cell membranes or stimulate endocytosis into host cells. These virulenc
12、e factors allow the bacteria to enter host cells and facilitate entry into the body across epithelial tissue layers at the body surface. Immune response inhibitors. Many bacteria produce virulence factors that inhibit the hosts immune system defenses. Toxins. Many virulence factors are proteins made
13、 by bacteria that poison host cells and cause tissue damage.,Methods by which bacteria cause disease,invasion,minimum lethal dose (MLD) the smallest amount of toxin that will kill an experimental animal.,Minimum infective dose,median infective dose (ID50) the amount of pathogenic microorganisms that
14、 will cause infection in 50 per cent of the test subjects.,infective dose that amount of pathogenic organisms that will cause infection in susceptible subjects.,Host factors,susceptibility,disposition,Immune system,Antibody, immunoglobulin,Iceberg concept of infection,Infectious disease spectrum,If
15、a large number of individuals are equally exposed to an infectious agent, they do not all respond in the same manner. 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 sy
16、mptoms Some become infected and develop severe symptoms Some die as a result of their infection,Pathogenesis of infection,Clinical manifestations of infectious diseases,Non-specific,Organ system-based,FeverAnorexiaFatigueMuscle achesSkin rash,a state of physical and/or mental weakness,Loss of appeti
17、te,Mary Mallon was an asymptomatic carrier of typhoid fever. Over the course of her career as a cook, she infected 53 people, three of whom died.,Host-Pathogen Interactions: Symbiotic Relationships,MutualismCommensalismParasitismNeutralism,A symbiotic relationship in which both species benefit,A sym
18、biotic relationship in which one organism derives benefit and the other is unharmed,A symbiotic relationship in which one 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
19、organism,airborne infection droplet infectionvector-borne infection waterborne infectionbloodborne infection,Mode of infection,Sneezing 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
20、dust particles.droplet infection infection due to inhalation of respiratory pathogens suspended on liquid particles exhaled 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, l
21、ouse, fly, or tick.waterborne infection infection by microorganisms transmitted in water.,Classification of infections 1,Type of the pathogen,Degree of involvement,Bacterial, viral, fungal, parasitic,Local/focal, generalized,Manner acquired,Community, hospital/nosocomial,Classification of infections
22、 2,Type of occurrence,Endogenous vs. exogenous,Autoinfection vs. cross-infection,Superinfection vs. reinfection,sepsis,Opportunistic infection,an infection caused by an infectious agent that is already present in the body, but has previously been inapparent or dormant.,an infection that develops fro
23、m bacteria normally outside the body that have gained access to the body,an infection caused by a disease agent that is already present in the body,an infection by an organism that does not ordinarily cause disease but becomes pathogenic under certain circumstances (e.g., impaired immune responses).
24、,the transmission of a communicable disease from one person to another because of a poor barrier protection,an infection following a previous infection, especially when caused by microorganisms that have become resistant to the antibiotics used earlier,a second infection by the same microorganism, e
25、ither after recovery or during the original infection,12345678,a bacterial infection in the bloodstream or body tissues,Cross-infectionExogenous infectionEndogenous infectionOpportunistic infectionReinfectionSuperinfectionAutoinfection Sepsis,Laboratory diagnosis of infectious diseases,Gold standard
26、 test,procedures,Microscopy and Staining proceduresCulture and sensitivitySerologic test,Staining procedures,Urinalysis and fecalysisSpecimen smear (blood, stool)Gram StainingZeihl-Neelson stainKOH (potassium hydroxide) test for fungi,Gram Staining,Gram stain a staining procedure in which microorgan
27、isms are stained with crystal violet, treated with strong iodine solution, decolorized with ethanol, and counterstained with a contrasting dye; those retaining the stain are gram-positive, and those losing the stain but staining with the counterstain are gram-negative.,Zeihl-Neelsen stain,The Ziehl-
28、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
29、in 10% KOH and examined directly under the microscope,KOH (potassium hydroxide) test for fungi,Culture and sensitivity,Serologic test,any laboratory test involving serologic reactions, especially any such test measuring serum antibody titer.,Treatment and prevention,Medical treatment,prophylaxis,Pre
30、- and post-exposurePharmacologicalImmunization,antibiotics,vaccination local treatment of the woundadministration of rabies immunoglobulin,Pre- and post-exposure prophylaxis,A young girl infected with smallpox (1973). Due to the development of the , the disease was officially eradicated in 1979.,smallpox vaccine,Outline,PathogenHost Pathogenesis of infectionClassification of infectionClinical manifestationsLaboratory diagnosis of infectious diseasesTreatment and prevention,LEARN MORE, BE MORE,
