Define the key terms related to microbial control: sterilization, disinfection, antisepsis, degerming, santization, static, and cidal.
Sterilization - the removal of all microorganisms, including endospores. Disinfection - any treatment used on inanimate objects to kill or inhibit the growth of microorganisms; a chemical used is called disinfectant. Antisepsis - a chemical method for disinfection of the skin or mucous membranes; the chemical is called an antiseptic. Degerming - the removal of microorganisms in an area; also called degermation. Santization - the removal of microbes from eating utensils and food preparation areas. Static - treatment that inhibits bacteria but growth might resume. Cidal - kills microorganisms.
Explain how microbial control is affected by the following variables: type of microbe, physiological state of microbe, environmental conditions, time of exposure, concentration or intensity of agent, temperature of agent, and number of cells.
The more microbes there are to begin with, the longer it takes to eliminate the entire population. Chemical antimicrobials often require extended exposure to affect more-resistant microbes or endospores. The presence of organic matter often inhibits the action of chimcal antimicrobials.
Describe the pattern of microbial death and relate the information to the importance of time of exposure and number of cells.
Bacterial populations subjected to heat or antimicrobial chemicals ususally die at a constant rate. Sucha a death curve, when plotted logrithmically, shows this constant death rate as a straight line. The time it takes to kill a microbial population is proportional to the number of microbes. Microbial species and life cycle phases have different susceptibilities to physical and chemical controls. Organic matter may interfere with heat treatments and chemical control agents. Longer exposure to lower heat can produce the same effect as shorter time at higher heat.
Describe the effect of microbial control agents on cellular structures.
The susceptibility of the plasma membrane is due to its lipid and protein components. Certain chemical control agents damage the plasma membrane by altering its permeability. Some microbial control agents damage cellular proteins by breaking hydrogen bonds and covalent bonds. Other agents interfere with DNA and RNA and protein synthesis.
Describe the specific physical methods of microbial control and be able to cite specific examples of their use.
Heat is used to kill microorganisms. Filtrationis the passage of a liquid or gas through a filter with pores small enough to retain microbes. Low Temperatures causes microbes to not reproduce most time. High Pressure denatures proteins in vegetative cells. Desiccation is when microorganisms cannot grow but can remain viable in the absence of water. Osmotic Pressure is when microorganisms in high concentrations of salts and sugars undergo plasmolysis. Radiation effecting microbes depends on the wavelength, intensity, and duration of being exposed to the UV light.
Describe the specific chemical methods of microbial control and able to cite specific examples of their use.
Principles of Effective Disinfection should be paid to the properties and concentration of the disinfectant to be used. Evaluating a Disinfectant by bacterial survival in the manufactures's recommended dilution of a disinfectant. Tyes of Disinfectants are phenol and phenolics, bisphenols, biguanides, halogens, alcohols, heavy metals and their compounds, suface-active agents, chemical food preservatives, antibiotics, aldehydes, chemical sterlization, plasmas, supercritical fluids, and peroxygens and other forms of oxygen.
Distinguish the terms chemotherapeutic agent, antimicrobial agent, antibiotic, semisynthetic antibiotic, synthetic drug.
Chemotherapeutic agent - chemicals that combat disease in the body. Antimicrobial agent - a chemical substance that destroys pathogenic microorganisms with minimal damage to host tissues. Antibiotic - an antimcrobial agent, usually produces naturally by a bacterium or fungus. Semisynthetic antibiotic - ......... Synthetic drug - a chemotherapeutic agent that is prepared from chemicals in a laboratory.
Briefly relate the history of the development of antimicrobial drugs.
Paul Ehrlich developed the concept of chemotherapy to treat microbial diseases; he predicted the development of chemotherapeutic agents, which would kill pathogens without harming the host. Sulfa drugs came into prominence in the late 1930s. Alexander Fleming discovered the first antibiotic, penicillin, in 1929; its first clinical trials were done in 1940.
Compare the terms narrow spectrum and broad spectrum drugs.
Narrow spectrum drugs affect only a select group of microbes - gram-positive cells, for example; broad spectrum drugs affect a more diverse range of microbes.
Distinguish static drugs from cidal drugs - how do they work and how they are prescribed.
Cidal kills the microorganisms. Static inhibits the microorganisms growth.
Define "selective toxicity".
Selective toxicity - the property of some antimicrobial agents to be toxic for a microorganism and nontoxic for the host.
Cite the five methods of action of antimicrobial drugs and be able to relate specific examples in each category.
Some agents, such as penicillin, inhibit cell wall synthesis in bacteria. Other agents, such as chloramphenicol, tetracyclines and streptomycin, inhibit protein synthesis by acting on 70S ribosomes. Antifungal agents target plasma membranes. Some agents inhibit nucleic acid synthesis. Agents such as sulfanilamide act as antimetabolites by competitively inhibiting enzyme activity.
Cite the drugs effective for treating fungal infections.
Polyenes, such as nystatin and amphotericin B, combine with plasma membrane sterols and are fungicidal. Azoles and allylamines interfere with sterol synthesis and are used to treat cutaneous and systemic mycoses. Echinocandins interfere with fungal cell wall synthesis. The antifungal agent flucytosine is an antimetabolite of cytosine. Griseofulvin interferes with eukaryotic cell division and is used primarily to treat skin infections caused by fungi.
Cite some drugs that are effective in treating mycobacterial infections.
Isoniazid and Ethambutol are two drugs in treating mycobacterial infections.
Explain why it is more difficult to find drugs effective against fungi, protozoans, and viruses than for bacteria.
Eurkaryotes use the same mechanisms to synthesize proteins and nucleic acids as higher animals. This causes it more difficult to find a point of selective toxicity in eukaryotes than in prokaryotes.
Compare the Kirby-Bauer disc diffusion test, the MIC test, and the E-test methods for testing for drug susceptibility.
MIC (minimal inhibitory concentration) - the organism is tested against a series of dilutions of the drug. The smallest concentration of the drug which completely inhibits growth is determined and compared to attainable blood and tissue levels. E-test - a gradient of the drug is impregnated on a plastic strip and put on an agar plate. Useful for organisms that are fastidious and need special media. Kirby-Bauer disc diffusion - a specified concentration of the organism is spread on a plate of Mueller-Hinton agar and filter paper discs with standard concentrations of various drugs are placed on the plate. After incubation, zones of inhibition are measured and compared to table values and interpreted as susceptible, intermediate, or resistant.
Describe some possible mechanisms of drug resistance and discuss current problems associated with the issue and ways to minimize the problem of increasing resistance.
Synthesis of enzyme by bacteria which degrades the drug. An example is beta-lactamase. A new category of drugs has been introduced which use a standard antibiotic plus an inhibitor of beta-lactamase (augmentin = amoxicillin + clavulanate potassium). Altered permeability of the drug - cell prevents drug uptake. Altered target - drug doesn't bind effectively to target such as ribosome.
Cite some problems and contraindications associated with some specific antimicrobial drugs.
They may cause hypersensitivities (skin eruptions), kidney dysfunction, damage to bone marrow, damage to nervous system, liver damage, diarrheas, and superinfections.
Cite some examples of specific antiviral drugs and what diseases they are effective in treating.
Acyclovir, Tamiflu, Alpha Interferon, Ribavirin, Fuzeon, Efavirenz, etc.... are antiviral drugs. The are used in treating T-cell, influenza, Herpes infections, genital warts, respiratory viral infections, HIV/AIDS, and enzyme inhibitors.
Review the terms transcription, translation and replication.
Transcription is the synthesis of a complementary strand of RNA from a DNA template. Translation is the use mRNA as a template in the synthesis of protein. Replication is when one "parental" double-stranded DNA molecule is converted to two identical "daughter" molecules.
Define mutation and give some examples of mutagens. What is the significance of spontaneous mutations?
Mutation is a change in the base sequence of DNA. Chemical mutagens include base-pair mutagens, nucleoside analogs, and frameshift mutagens. Ionizing radiation causes the formation of ions and free radicals that react with DNA; base substitutions or breakage of the sugar-phosphate backbone results. Ultraviolet radiation is nonionizing; it causes bonding between adjacent thymines. Spontaneous mutations occur without the presence of any mutagen.
Describe the Ames test.
Ames test is a procedure using bacteria to identify potential carcinogens. The test is based on the observation that exposure of mutant bacteria to mutagenic substances may cause new mutations that reverse the effect of the original mutation. The test measures the auxotrophs of Salmonella after treatment with a mutagen.
Compare the three methods of genetic recombination: transformation, conjugation, and transduction.
Transformation: is the transfer of DNA from a donor bacterial cell ch has lysed to a recipient competent cell thru d environment.
Conjugation: Genetic material is transferred from one bacteria to its recipient.uses a specialized pili(sexpili)
Transduction: bacteria DNA is transferred from a donor cell to a recipient cell inside a virus that infects bacteria(bacteriophage)
Define plasmid and describe its role in recombinant DNA technology. What do genes on plasmids code for? What are transposons?
Plasmids are self replicating,gene-containing circular pieces of DNA .
Conjugative plasmid(F factor):carries genes for sex pili and for the transfer of the plasmid to another cell.
Dissimilation Plasmids:Code for enzymes that trigger the catabolisim of certain unusual sugars and hydrocarbons.
R Factors: plasmids that have antibiotic resistance. (They carry genes that confer upon their host cell resistance to antibiotics,heavy metals or cellular toxins.
RTF(resistance transfer factor): genes for plasmid replication and conjugation.
R-determinant: resistance genes; it codes for the production of enzymes that inactivate certain drugs or toxic substance
Transposons: are small segments of DNA that can move from one region of a DNA molecule to another.
Insertion sequences( simplest transposons) contain only a gene that codes for enzyme,that catalyzes the cutting and resealing of DNA that occurs in transposition, and recognition sites.
Complex Transposons: carry other genes not connected with d transposition process. eg: bacterial transposons: contain genes for enterotoxin or for antibiotic resistance.
Discuss recombinant DNA technology and cite some current applications in the medical field.
Recombinant DNA (rDNA technology) or genetic engineering is the inserting or transfer of genes into cells among unrelated species via laboratory manipulation.
Cloning,maping of the human genome
Describe the Rickettsiae - include significant diseases.
Rickettsia is an obligate intracellular parasites, they are gram-negative rod shaped bacteria or cocobacilli. Responsible for diseases known as the spotted fever group, e.g epidemic typhus,(Rickettsia prowazekii),transmitted by lice, endemic murine typhus(R.typhi )and transmitted by rat fleas Rocky Mountain spotted fever by R. rickettsii transmitted by ticks.
In human rickettsial infections damage the permeability of blood capillaries, xterised by spotted rash.
Describe the Chlamydia - include significant diseases.
Chlamydia are gram-negative coccoid bacteria,transmitted by to humans by interpersonal contact or by airborne respiratory routes.
Chlamydia trachomatis : responsible for trachoma(blindness),primary causative agent of both nongonococcal urethris(common sexually transmitted disease), lymphogranuloma venereum
Chlamydophila psittatci (respiratory disease psittacosis)
Chlamydophilia pneumoniae is the cause of a mild form of pneumonia in young adults.
Describe the Mycoplasma - include significant diseases.
Mycoplasmas- pleomorphic,produce filaments that resmble fungi,small
Spiroplasm:plant pathogens and common parasites of plant-feeding insects
Ureaplasma-urinary tract inspection
Describe the structure of molds and compare them to bacteria.
The thallus(body) of a mold or flesh fungus consists of long filaments of cell joined together. Filamens are called hyphae
Describe briefly the reproductive mechanisms of molds.
....Molds and fleshy fungi have several reproductive strategies. They can reproduce asexually by fragmentation of their hyphae. They can also reproduce both sexually and asexually by the formation of spores. fungican be identified by their spore type...
Describe the structure and reproduction of yeasts.
.Yeasts are unicellular, fungi are multicellular. Yeast, the simplest fungi reproduce asexually by budding or fission
Distinguish between systemic, subcutaneous, superficial-cutaneous and opportunistic mycoses on the basis of mode of entry and site of infection.
Systemic mycoses are fungal infections deep within the body. They are usually transmitted by inhalation of the spores from the soil, such as occurs in coccidioidomycosis. Subcutaneous mycoses occur beneath the skin. through a puncture wound. The puncture allows spores or mycelial fragments to implant directly into the tissue beneath your skin.
Opportunistic Mycoses are caused by fungi that are not pathogenic.
Describe selected fungal pathogens.
.. Pneumocystis is the most common life-threatening infection in AIDS patients.
fungus is Stachybotrys, which has been found growing on water-damaged walls of homes. Its toxic spores can cause fatal pulmonary hemorrhage in infants.
Another opportunistic fungal infection is a yeast infection, also called candidiasis. These are most frequently caused by Candida albicans. Yeast infections may occur in the mouth as thrush or as vulvovaginal candidiasis in females.
Describe the distinctive characteristics of the five groups of protozoans. Include representative pathogens in each group.
Vegetative form: trophozoite
Asexual reproduction is by fission,budding or schizogony.
Sexual reproduction is by conjugation
can produce cyst that provides protection duing adverse environmental condition......
Describe briefly some selected multicellular parasites.
.Multicellular Parasites are
Describe the composition of a trypical virus
Viruses are made of protein(capside) and nucleic acid(RNA or DNA)
What criteria are used to classify viruses.
Virus classification is currently based on five phenotypic characteristics;
1. morphology, or structure of the virus;
2. type of nucleic acid, or the genetic material of the virus;
4. mode of replication; hosts
5.the type of disease they cause.
Describe how obligate intracellular parasites are cultured in the laboratory.
3. In embryonated poultry eggs, from chickens or turkeys
Describe the two patterns of infection possible with a bacteriophage and the clinical relevance of a prophage.
Describe the steps in the replication of an animal virus.
Step 1: The virus attach itself to its host cell (attachment?
Step 2: The virus or its genetic information penetrates the cell.( Endocytosis)
Step 3: The nucleic acid is uncoated which frees the DNA or RNA from its capsomeres or lipid envelope and permits the host cell to read out ( express ) the genetic functions of the virus. (uncoating)
Step 4: Transcription and Translation (biosyntheris)
Step 5: The capsomeres are assembled to form a new shell around the nucleic acid of the virus.(maturation)
Step 6: The mature virus having duplicated its new copies, is released from the infected cell to attack a new cell and repeat this process.(Release)
Differentiate between persistent (slow) virus infections and latent infections.
Persistent viral infections are disease processes that occur over a larg period and generally fatal.
Latent viral infection is one in ch the virus remains in the host cel for along period e.g cold sores and shingles
Discuss briefly the relationship of viruses to cancer. What are "oncogenes"?
An Oncogene is a gene when mutated or expressed at high levels turn a normal cell into a tumor cell.
Oncogenes transform normal cells into cancerous cells.
What is a prion?
prions are infectious proteins,they involve the degeneration of the brain tissues. Prion diseases are the result of an altered protein, the cause can be a mutation in the normal gene for PrPc or contact with an altered protein (PrPsc)