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MICROBIOLOGY 2 MARKS
IMMUNOLOGY – INFECTION
1. SAPROPHYTES:
Free-living microbes that subsist on dead or decaying organic matter Found in soil and water Play an important role in degradation of organic materials in nature Incapable of multiplying on living tissues
- PARASITES: Microbes that can establish themselves and multiply in host May either be pathogens or commensals
- PATHOGENS: pathos – suffering,gen – produce = disease producing microorganisms that are capable of producing disease in the host
- COMMENSALS: Microbes living in complete harmony with the host without causing any damage to it Normal bacterial flora of the body consists of commensals They behave as facultative pathogens when host resistance is lowered
- INFECTION: The lodgement and multiplication of a parasite in or on the tissues of host
- PRIMARY INFECTION: Initial infection with a parasite in a host
- RE-INFECTION: Subsequent infections by the same parasite in the host
- SECONDARY INFECTION: A new parasite sets up an infection in a host whose resistance is lowered by a pre-existing infectious disease
- FOCAL INFECTION: Focal sepsis A condition where, due to infection or sepsis at localized sites such as appendix or tonsils, generalized effects are produced
- CROSS INFECTION: In a patient already suffering from a disease, a new disease is set up from another host or another external source
- NOSOCOMICAL INFECTION: nosocomion – hospital cross-infections occurring in hospitals
- IATROGENIC INFECTION: Physician-induced infections resulting from investigative, therapeutic or other procedures
- ENDOGENOUS or EXOGENOUS INFECTIONS: Depending on the source of infection, within or outside the host’s own body respectively
- INAPPARENT INFECTION: Synonym: subclinical infection Here, the clinical effects are not apparent
15. ATYPICAL INFECTION:
The typical or characteristic clinical manifestations of the particular infectious disease are not present
- LATENT INFECTION: Following an infection, some parasites may remain in the tissues in a latent or hidden form, proliferating and producing clinical disease when the host resistance in lowered
- CARRIER: A person who harbors the pathogenic microorganism without suffering any ill effects because of it
- HEALTHY CARRIER: One who harbors the pathogen but has never suffered from the disease caused by the pathogen
- CONVALESCENT CARRIER: One who has recovered from the disease and continues to harbor the pathogen in his body
- TEMPORARY CARRIER: The duration of carriage lasts less than a period of six months
- CHRONIC CARRIER: The duration of carriage may last for several years and even for the rest of one’s life
- CONTACT CARRIER: A person who acquires the pathogen from a patient
- PARADOXICAL CARRIER: A carrier who acquires the pathogen from another carrier
- RESERVOIR HOSTS: Many pathogens are capable of infecting both human beings and animals The animals serve to maintain those parasites in nature and acts as the reservoir of human infections They are reservoir hosts
- ZOONOSES: Infectious diseases transmitted from animals to human beings May be bacterial (plague-rats), viral (rabies-dogs), fungal (dermatophytes- cats&dogs)
- ARTHROPOD-BORNE DISEASES: Diseases caused by blood sucking insects that transmit pathogens to human beings Common vectors: mosquitoes, ticks, mites, flies, fleas, lice
- MECHANICAL VECTORS: The mode of transmission is mechanical e.g. Transmission of dysentery or typhoid bacilli by domestic fly
- BIOLOGICAL VECTORS: In the body of the vector, the pathogen multiplies and undergoes a part of its developmental cycle in it They transmit infection only after the pathogen has multiplies in them sufficiently or has undergone a developmental cycle e.g. Aedes aegypti in yellow fever, Anopheles in malaria
- EXTRINSIC INCUBATION PERIOD:
Generally formed by G+ bacteria but may also be produced by some G- organisms such as Vibrio cholera, E. coli,..
- ENDOTOXINS: Heat stable lipopolysaccharides that form an integral part of the cell wall of G- bacteria They are secreted outside the bacterial cell and are released only by the disintegration of the cell wall Active only in large doses
- PLASMIDS: Extranuclear genetic elements consisting of DNA Cytoplasmic carriers of genetic information Also known as Episomes Genes coding for some virulence characteristics may be plasmidborne
- COMMUNICABILITY: Ability of a parasite from one host to another This property has no influence in the production of the disease but determines the survival and distribution of a parasite in a community
- BACTERIAL PRODUCTS: Products other than toxins contribute to virulence by inhibiting the mechanism of host resistance e.g. coagulase, leucocidins, etc.
- BACTERIAL APPENDAGES: The appendages like capsules, surface antigens help bacteria to withstand phagocytosis and the lytic activity of complements e.g. Vi antigen of S.Typhi, Capsules of pneumococci, etc.
- BIOFLIMS: Well organized microcolonies of bacteria enclosed in self-produced extracellular polymer matrices (glycocalyx) Separated by water channels that remove water and deliver nutrients Classification: > Adherent > Clinging > Submerged Types based on no.: Monomicrobial and polymicrobial biofilms
- PATHOGENESIS: The mechanism or the stages involved in the progression of a disease e.g. Free-floating bacteria come in contact with the medical devices, attach to them with pili then aggregate, multiply, secrete extracellular polymers and are encased
- INFECTING DOSE: The adequate no. of bacteria required to cause successful infections in host Dosage estimation: minimum infecting dose MID or minimum lethal dose MLD are the minimum no. of bacteria required to produce clinical evidence of infection or death respectively in a susceptible animal under standard conditions
- BACTEREMIA: Spread of bacteria from the site of entry through the bloodstreamresulting in infection
- SEPTICEMIA: A condition where the circulating bacteria multiply in the blood, form toxic products and cause high, swinging type of fever
51. PYEMIA:
A condition where pyogenic bacteria produce septicemia with multiple abscesses in the internal organs such as the spleen, liver and kidneys
- ENDEMIC DISEASE: Disease which is constantly present in a particular area e.g. Typhoid fever in India
- EPIDEMIC DISEASE: Disease that spread rapidly, involving many persons in an area at the same time e.g. Influenza in cold countries
- PANDEMIC DISEASE: An epidemic that spreads through many areas of the world involving very large numbers of people within a short period e.g. Cholera, Plague, Influenza
- PROSODEMIC DISEASE: Epidemics vary in the rapidity of spread Water borne diseases like cholera cause explosive outbreaks, while disease that spread by person to person contact evolve slowly Such creeping and smoldering epidemics,as that of cerebrospinal fever are termed as prosodemic diseases
- FUNCTIONS OF B-CELLs: Bone marrow is the site of B cell origin and development B cells undergo maturation in different stages as pro-, pre-, immature and mature B cells On contact with its specific antigen, the mature cell undergoes clonal proliferation to form long-lived memory cells or plasma cells As memory cells, they are responsible for recall phenomenon on subsequent contact with same antigen As plasma cells, they are antibody secreting cells
- NULL CELLS: Circulating lymphocytes possessing neither T-cell nor B-cell markers Types: > Natural Killer (NK) cells > Antibody dependent cytotoxic cells (ADCC) > Lymphokine activated killer (LAK) cells
- HISTOCOMPATIBLITY ANTIGENS: Cell surface antigens that induce an immune response leading to rejection of allografts coding for three different classes of proteins (Class I, II, III)
- ELISA: Enzyme Linked Immuno Sorbent Assay Sensitive and specific Detect IgM and IgG antibodies separately Useful for differentiation between acute and chronic infection
- COOMBS TEST Antiglobulin test Devised by Coombs, Mourant and Race (1945) Employed for the detection of anti-Rh antibodies Useful for demonstration for any type of incomplete or non-agglutinating antibody (e.g. as in brucellosis) Types: Direct and Indirect Coombs test
Protects against fungi, viruses and facultative intracellular bacterial pathogens, participate in the rejection of homografts and graft versus, host reactions provides immunological surveillance and immunity against cancer. Mediates the pathogenesis of delayed hypersensitivity and certain autoimmune diseases. 70.HYPERSENSITIVITY: Hypersensitivity reactions are pathologic processes that result from exaggerated specific interactions between antigens and either between humoral antibodies (or) sensitized lymphocytes resulting in tissue injury. TYPES: - 1.BASED ON DURATION: Immediate hypersensitivity Delayed hypersensitivity 2.BASED ON COMPONENT: Antibody mediated Cell mediated 3.BASED ON CELL: TYPE 1, 2, 3, 4 & 5. 71.AUTOIMMUNE DISEASE: Serum component (or) components is decreased in many autoimmune diseases such as systemic lupus erythromatosis and rheumatoid arthritis. Complement also plays a major role in pathogenesis of autoimmune hemolytic anemia. 72.IMMUNO DEFICIENCY DISEASE: Immuno deficiency disease are conditions where the defense mechanism of the body are impaired, leading to repeated microbial infection of varying severity and sometimes enhanced susceptibility to malignancies. 73.ANAPHYLAXIS: This is the classical immediate hypersensitivity reaction antigens and haptens can induce anaphylaxis. There should be an interval of at least 2-3 weeks between sensitizing dose and shocking dose. The clinical features of anaphylaxis are same with any antigen but vary between species. The clinical effects are due to smooth muscle contraction and vascular permeability. 74.ALLOGRAFT: a. The primary function of immune system is the recognition and elimination of foreign cells and antigens enter the body, tissues and organ grafted from individual to another member of same species. b. An allograft will be accepted if the host is rendered immunologically tolerance. Adaptive immunization is the process of transferring immunity by means of lymphoid cells. 75.MHC (Major Histocompatibility Complex):
a. Gore identified two blood group antigen systems in mice: antigen1 was common to all strains; antigen2 was found only in some strains and appeared to be responsible for allograft rejection. This was called the H-2 antigen. b. The histocompatibility antigens are cell surface antigens that induce an immune response leading to rejection of allografts. The H-2 antigen system was found to be the major histocompatibility antigen for mice and to be coded for by a closely linked multiallelic cluster of genes, called the major histocompatibility complex. 76.FUNCTIONS OF TCELLS: The function of Tcells is to perform a variety of immune response in the body. T cells are one of 2 types of white blood cells that help immune functions. Functions of T cells include direct attacks on bacteria, viruses and foreign tissues and producing substances called cytokines that direct response and activities in other immune cells. 77.HOMOGRAFT: A graft of tissue between individuals of the same species but of disparate genotypes, types of donor are cadaveric, living and living unrelated called homograft. 78.BACTERIAL GROWTH CURVE: When the bacterium is seeded into a suitable liquid medium and incubated its growth follows a definite course. If bacterial counts are made at interval after inoculation and plotted in relation to time a growth is obtained. It shows the following phases: 1.LAG PHASE 2.LOG PHASE 3.STATIONARY PHASE 4.DECLINE PHASE 79.OXIDATIVE PHOSPORYLATION: Energy is provided by production of energy rich phosphate bonds and the conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP). This process is known as oxidative phosphorylation. 80.DIS-INFECTION: Dis infection is the destruction removed of all pathogenic organisms (or) organisms capable of giving the infection. 81.DECONTAMINATION: It is the process of rendering an article or area free form contaminants, including microbial, chemical, radioactive and other hazards. 82.BACTERIOSTATIC AGENTS: Bacteriostatic agents prevent the multiplication of bacteria which may remain alive it chemical which is bactericidal at a particular concentration may only be bacteriostatic at a higher dilution. 83.STERILISATION:
Bacteria and blue green algae are prokaryotes. They do not contain chlorophyll. They are unicellular and do not show true branching except the higher bacteria. 90.TYPES OF MICROSCOPE: Optical (or) light microscope Phase contrast microscope Darkfield / ground microscope Electron microscope 91.GRAM STAINING: a. It is a method of staining bacteria in tissues. b. Gram positive cells have more acidic protoplasm, which may account for their retaining the basic primary dye more strongly than gram negative bacteria. c. The peptidoglycan of gram positive bacteria is thick and thus able to retain the dye iodine complex. d. The high lipid content of gram negative bacteria makes them permeable to secondary dye after decolourisation with organic solvents like acetone. 92.NEGATIVE STAINING: Indian ink (or) nigrosin is emulsified with the sample (or) organism to provide a uniformly coloured back ground against which the unstained bacteria stand out in contrast. Very slender bacteria such as spirochete that are not demonstrable by simple staining methods can be viewed by negative staining. 93.ACID FAST STAINING: a. The smear is stained by a strong solution of carbon fuchsin with application of heat. b. It is then decolourised with 20% sulphuric acid and counterstained with a contrasting dye such as methylene blue. c. The acid fast bacteria retain the fuchsin (red) colour, while the others take the counterstain. Mycobacterium leprae resists decolourisation with 5% sulphuric acid. 94.VOLUTIN GRANULES: a. It is otherwise called METACHROMATIC (or) BABES-ERNST GRANULES. b. These are highly refractive, strongly basophilic bodies consisting of polymetaphosphate. They appear reddish when stained with polychrome methylene blue or toluidine blue. Special staining techniques such as Albert’s (or) Neisser’s demonstrate the granules more clearly. 95.SPORES: a. Some bacteria, particularly members of the genera bacillus and clostridium have the ability to form highly resistant during resting stages called spores. b. Each bacterium forms one spore, which on germination forms a single vegetative cell. c. As bacterial spores are formed inside the parent cell, they are called endospores. d. Sporulation is initiated by the appearance of a clear area, usually one end of the cell, which gradually becomes more opaque to form the forespores.
e. Some spores have an additional outer covering called “exosporium” which may have distinctive ridges & grooves. 96.SOURCE OF INFECTIONS: a) Human b) Animals c) Insects d) Soil e) water f) food 97.TYPES OF CULTURE METHODS: a) Streak culture b) Stab culture c) Lawn (or) carpet culture d) Pour plate culture e) Stroke culture f) Swab plate culture g) Liquid culture 98.CLONE: A population derived by binary fission from a single cell is called alone. A single bacterial colony represents a clone. Though all the cells in a clone are expected to be identical in all respects, a few of them may show differences due to mutation. 99.EPITOPE: The smallest unit of antigenicity is known as antigenic determinant (or) epitope. The epitope is that small area on the antigen. 100.PLEOMORPHISM: Some species of bacteria exhibit great variation in the shape and size of individual cells. This is known as pleomorphism. It is caused by defective cell wall synthesis. 101.MUTATION: Mutation occurs when a DNA gene is damaged (or) changed in such a way as to alter the genetic TYPES: Substitution, Insertion/frame shift, Deletion, Inversion. 102.PRIMARY INFECTION: Initial infection with a parasite in a host is termed as primary infection. 103.SECONDARY INFECTION: When a new parasite sets up an infection in a host whose resistance is lowered by a pre-existing infectious disease, this is termed as secondary infection. 104.FOCAL INFECTION:
112.CULTURE MEDIA:
A culture medium is a mixture of chemicals/that is able to support the growth of microorganisms. It should contain a source carbon and energy for the organism to be grown. There may also be minerals and other growth factors such as vitamins or serum. All culture media must contain water, to facilitate the growth of organisms. 113.ENRICHED MEDIA: In these media, substances such as blood, serum or egg are added to a basal medium. They are used to grow bacteria which are more exacting in their nutritional needs. 114.ENRICHMENT MEDIA: Enrichment media are liquid media to which substance that have a stimulating effect on those to be suppressed are incorporated in the medium. E.g. tetrathionate broth & selenite f broth. 115.INDICATOR MEDIA: An indicator medium changes the color when a bacterium grows in them. E.g. Wilson-Blair medium S.typhi reduces sulphite to sulphide in the presence of glucose and the colonies of S.typhi have a black metallic salts shown. 116.SELECTIVE MEDIA: Selective media are solid media to which an inhibiting substance is added. E.g. Thayer-Martin medium, Deoxycholate citrate medium for dysentery bacilli. This media enables a greater number of the required bacterium to form colonies that the other bacterium. 117.TRANSPORT MEDIA: A transport media is used for transport of samples containing delicate organisms. For e.g. Stuart’s medium, non-nutrient soft agars gel containing a reducing agent to prevent oxidation and charcoal to neutralize certain bacterial inhibitors for gonococci. 118.TYNDALLIZATION: A single exposure of ninety minutes usually ensures sterilization but for media containing sugar or gelatin and exposure of 100°C for 20 mins. On three successive days is used. This is known as tyndallisation or intermediate sterilization. 119.USES OF AUTOCLAVE: They are used to decontaminate certain biological waste and sterilize media, instruments and lab ware. Regulated medical waste that might contain bacteria, viruses and other biological materials are recommended to be inactivated by autoclaving before disposal. 120.HOLDING TEMPRATURE OF AUTOCLAVE: STERILIZER TEMPERATURE Steam autoclave 121°C Unwrapped items 132°C
Lightly wrapped items 132°C Heavily wrapped items 132°C Dry heat wrapper 170°C Dry heat unwrapped 190°C Dry heat 190°C Chemical vapour 132°C Ethylene oxide Ambient 121.DISADVANTAGES OF HOT AIR OVEN: As they use dry heat instead of moist heat, some organisms like prions may not be liked by them every time. Based on the principle of thermal inactivation by oxidation. They do not require water and there is not much pressure build up within the oven, unlike an autoclave, making them safe to work with. Dry heat penetrates materials slowly and unevenly, and the oven requires continues source of electricity
