Fungi

General Characteristics

- Members of plant kingdom

- Devoid of leaves, stems/roots

- Lack chlorophyll: Require external carbon source (heterotrophic), Carbon derived as saprophytes by adhering to/decomposing nonliving organic matter, Carbon derived as parasites by invading living plants and animals

Fungi

General Characteristics Continued

- Eukaryotic: Posess nucleus, nuclear membrane, ER, Golgi app, and mitochondria.  Also posess a rigid cell wall comp. of chitin which absorbs several dyes and this helps aid in ID

- Yeasts: single celled fungal forms

- Molds: multiple cells forming a fliamentous mycellium

- Spores: fungi reproduce by spores via sexual/asexual production, morphology, arrangement/mode of derivation of spores serve as criteria for genus and species ID

- Habitat: Fungi are found in nearly every habitat on earth where organic materials exist

Fungi

Colonization

Superficial Mycoses

- Candidiases (thrush, vaginal)

- Dermatophytes (athlete's foot, tinea capitis, jock itch, nails, etc.)

- Sporotrichosis (gardener's hazard)

- Blastomyces (skin)

Fungi

Colonization

Intermediate Mycoses

- Aspergillus: lungs, gut-ingested spores, fungal ball

- Candidiases: children and immuno-comp

- Cryptococcus: pulmonary, cerebral

- All dimorphics: any organ

- Mucormycosis: rhinocerebral, pulmonary, GI, fungal ball

Fungi

Colonization

Systemic Mycoses

- Mucormycoses: necrotizing, rapic, fulminating

- Aspergillosis

- Candidiasis

- Cryptococcus

- All dimorphics

Fungi

Human Food Supply Destruction

- Dutch Elm Disease: Ceratocystis ulmi

- Wheat rust: Puccinia graminis

- Potato blight: Phytophthora infestans

Fungi

Positive Effects

- Common mold (neurospora crassa) has been used for genetic/biochemical studies

- Yeasts have been genetically engineered to produce: Human insulin, growth hormone, somatostatin, vaccine against viral hepatitis

Fungi

Diagnosis

- Direct Observation: Skin scrapings, tissue imprints/sections (special stains)

- Media:

Non-selective (Sabouraud's dextrose),

Selective (Mycobiotic, Sabouraud's w/antibiotic PCN, Streptomycin, Gent, Chloro), Cyclohexamide (prevents overgrowth by mold contaminants),

Enriched (brain hearth infusion with blood, potato dextrose agar, sporulation)

Fungi

Identification

- Prelim isolate observations:

Yeast-like (creamy, pasty to mucoid)

Mold (cottony to wooly)

Rate of growth

Colony pigmentation

Growth on media containing antifungal agents

Dimorphic growth

Fungi

Identification: Molds

- Mount preps (molds)

Tease mount (lactophenal aniline blue)

Scotch tape mount (lactophenol aniline blue)

Microslide culture

- Subculture/biochemical/DNA techniques to aid in ID

Fungi

Identification: Yeasts

- Germ tube: Candida albicans

- Corn meal agar preps looking for:

Hyphae

Blastoconidia (sandy beaches)

Chlamydoconidia (blastoconidia in clusters on pseudohyphae)

Arthoconidia (true hyphae breaking off)

- Manufactured yeast ID kits

VITEK

RapID Yeast Plus System

API 20C

BactCard Candida test

Fungi

Identification: Serological Diagnosis

- Immunodiffusion/complement fixation

Histoplasma

Blastomyces

Coccidiodes

Aspergillus

- Latex agglutination (Candida)

- Cryptococcal antigen assay (species-specific monoclonal antibodies)

- Enzyme immunoassay (EIA)

- Nucleic acid probes

Viruses

General Characteristics

- Viron: consists of nucleic acid surrounded by protective protein coat (capsid)

- Very small in size: smallest virus = 20nm, largest = 300 nm (E.coli = 1000nm)

Contain very few genes due to small size (4-200 vs. 3000 for E.coli)

- Contain either DNA or RNA, never both

DNA/RNA can be either single/double stranded

Most DNA viruses contain all their genetic info on a single linear molecule

RNA viruses can be linear or contain segmented viruses which have several dif. RNA molecules in their capsid (each one carrying the same/different genetic info)

Viruses

General Characteristics Continued

- Viruses lack cellular components necessary to generate energy/synthesize proteins

- Contain few enzymes: Only those involved w/entry into cells/replication of their own nucleic acid (viruses can only multiply inside living cells)

- Contain min. amt of genetic info: Info to make special protein coat, assure replication of its own chromosome, move virons in/out of host cell

Viruses

Shape and Functions

- Shape of virus = capsid shape (helical/spherical)

- Each capsid comp of many identical units (capsomeres), which serve as the morphologic unit

- Some viruses have only out coat and the viron (naked capsid)

- Some viruses have an additional lipid membrane (envelope), which is usually acquired from cytoplasmic membrane of infected cell (similar structure w/dbl layer of lipids) - Just inside lipid envelope is protein matrix - Spikes project from envelope/attach viron to host cell (protein, glycoprotein)

Viruses

Replication

- Attachment: Phages attach to host cell receptors

- Penetration: Viral nucleic acid enters host cell - Lysozyme (located on tip of tail) lyses cell wall, tip of tail opens and linear DNA in head passes through channel, injected through cell wall into interior of cell, only nucleic acid, not the entire viron enters cell

- Transcription/Translation: Phage DNA is transcribed leading to production of specific proteins. Part of DNA is transcribed in mRNA which is translated into proteins that are specific for infecting cell (phage induced proteins)

One such protein is a nuclease that degrades DNA of host cell

Host DNA is not transcribed, only phage DNA

Viruses

Replication Continued

- Phage DNA replicates and phage structural proteins are synthesized separately

- Phage DNA and protein assemble to form mature virons - maturation (some steps involve a self assembly process

- Virons are released from host cell (Lysozyme is coded by phage DNA and digests host cell wall from within, cell lyses and releases up to 200 phage virons)

Viruses

Diagnosis

- Cell culture

- Serological techniques: Detecting antigen and antibodies

- Direct detection of antigen from specimen

- Molecular methods

Immune System

General Characteristics

- Protection against invasion by foreign organisms/substances

- Infectious agents

- Cancers

- Autoimmune diseases

Immune System

Nonspecific

General Characteristics

- First defense to respond

- Not affected by prior contact w/infectious agent or other material involved

- Operates constantly to prevent establishment of infection

- May involve physical/chemical barriers

- Activities of nonspecific may be improved by specific response but are not required

Immune System

Nonspecific

Tissue Barriers etc.

- Tissue barriers and nonspecific factors:

  Physical barriers: Skin, mucous membranes, saliva, tears (may contain antimicrobial secretions or be acidic and inhibit bacteria)

  Urine flow through urinary tract = flushing mechanisms

  Respiratory tract, mucous in nose contains lysozyme and other antimicrobial agents, cilia in upper resp. tract keep mucous away from lungs

Immune System

Nonspecific

Tissue Barriers etc continued

-Antimicrobial (chemical) barriers: Lysozyme, Beta-lysin, Complement system, Peroxidase enzymes, Cytokines

- Inflammation (early reaction to injury): Redness, heat swelling, loss of function

- Phagocytosis: essential to nonspecific defense

Immune System

Nonspecific

Physiological Changes

- Alteration of temp and regulation leading to fever

- Redist. of iron in body so that bacteria do not have access

- Changes in protein and carb. metabolism: Rapid synthesis to increase supply of energy and raw materials to phagocytes

Immune System

Specific

General Characteristics

- Second line of defense; anamnestic/memory response

- Most highly developed in birds/mammals

- Depends on specialized cells (lymphocytes)

- Birds/mammals have efficient circulation to accommodate process

- Takes time to develop/become effective after nonspecific response

- Lymphocytes must multiply extensively to be effective

Immune System

Specific

Antigens/Antibodies

- Antigen: Large, foreign molecules that induce immune response (antibody generator), Smaller molecules become antigenic

- Antibody: Glycoprotein molecules calle immunoglobulins (Recognize antigens successfully, 5 classes: IgM, IgG, IgA, IgD, IgE), Structure consists of Y shaped molecule with 2 light (Fab) and 2 heavy (Fc) held together with disulfide bonds, Antigen binding sites are at end of each arm of the Y

Immune System

Specific

Immunoglobulins

- IgG: 80% of total if >2 yrs, most IgG in circulation, can cross placenta, interacts w/complement to aid in phagocytosis, neutralize toxins, prevent adherence of viruses/microorganisms to host cells

- IgM: First immunoglob. produced after antigen exposure, 5-10% of circulating immunoglob., structure in blood is pentameter of 5 subunits = 10 antigen binding sites, 5x lrgr than IgG, opsonizing antibody that increases phagocytosis, most efficient antibody in interacting with complement to aid phago and very efficient in agglutination, in some cases is only class of antibodies produced against some antigens (eg capsular polysaccharides of bacteria)

Immune System

Specific

Immunoglobulins Continued

- IgA: accounts for 10-13% antibodies, but only small proportion circulate, most associated w/mucous membranes/saliva/breast milk, appear as dimers (secretory IgA), secretory component transports molecule onto surface of mucous membrane/protects it from destruction by proteolytic enzymes, antibodies bind to microorg. and prevent attachment/colonization, secretory IgA in breast milk protects against intestinal pathogens

- IgD: <1% of all immunoglob., similar structure to IgG, Functions during development/maturation of antibody response, fount mostly on surface of B lymphocytes, function not clearly defined

- IgE: barely detectable, responsible for allergic/hypersensitivity rxns, bound to basophils/mast cells and can release potent chems. if specific antigen binds to it

Immune System

Specific

Role of Lymphocytes

- Most lymphocytes are metabolically inactive/merely circulate to reach lymphoid tissue where they're the primary cell

-Become active/divide in lymphoid tissue

- T cells: mature in thymus, important in cellular immune response/as auxillary cells in other responses

- B cells: mature in bone marrow, important in antibody response

Immune System

Specific

Role of Lymphocytes Continued

- Lymphocytic antigens/markers: Found on surface of each lymph cell, B cells are ID by presense of immunoglob., During maturation dif clusters of CD antigens/markers are expressed on cell membrane, CD markers especially useful in ID T cells

- Plasma cells: B cells that have left circulation, gone into lymph tissue, Active-antibody producing cell

Immune System

Specific

Development of Antibody Response

Immne System

Specific

Cell-mediated Immune Response

Immunologic Tolerance/Control

- Specific unresponsiveness to antigen

- Immune response carefully ctrld by several mechanisms to prevent overproduction of antibody or T cells: T supressor cells (some CD8 lymphs, etc)

Vaccination and Immunization

- Immunity can be natural/artificial and active/passive

- Active immunity is induced artificially by giving vaccines: Living, attentuated, Inactivated immunizing agents

- Passive immunity usually involves the transfer of preformed antibodies: Naturally (mother -> fetus) or artificially (immune serum globulin)