Microbio E1 Chap 1-13

What is a prokaryote?

What is a prokaryote?

simple, single-celled organism that lacks a nucleus and membrane bound organelles

What substance forms many bacterial walls and consists of glycosaminoglycan chains interlinked with short peptides?

peptidoglycan

What structure does penicillin target to disrupt the integrity of the bacterial cell wall?

peptide cross-links

What is a bacterial chromosome?

single, large, circular, double-stranded DNA molecule that contains all the genetic information required by the cell

What is a plasmid?

small, circular, double-stranded DNA; not essential to growth or metabolism; duplicated and passed down to offspring

Where are plasmids and the bacterial chromosome located?

in the nucleoid

What is transcription?

synthesis of mRNA from DNA

What is translation?

synthesis of proteins from mRNA

Why can transcription and translation occur simultaneously?

cell lacks membrane bound nucleus: all components need are in the cytoplasm

Which bacterial genres produce endospores?

bacillus and clostridium

Which bacteria is known to cause outbreaks of diarrhea in hospitals and nursing homes?

C. diff

Which type of bacteria has a thick layer of peptidoglycan that forms a single layer around the cell? What color will this turn during a gram stain?

Gram +; purple

Steps of a gram stain:

Flood slide with crystal violet x10 sec then rinse → flood with Gram’s iodine x 10 sec then rinse → decolorize with 95% ethanol until thinnest parts are colorless then rinse → flood with safranin (pink) x10 sec then rinse → air dry or blot with absorbent paper

When viewed under a microscope, which G+ bacteria appear as cocci in clusters “bunches of grapes”?

staphylococcaceae

When viewed under a microscope, which G+ bacteria appear as cocci in pairs or chains?

Streptococcus

How does listeria look after a gram stain when viewed through a microscope. Does it produce spores?

G+; purple, linked rods; non-spore forming

Define pleomorphism.

present in different sizes and shapes due to variations in cell wall

What are the 6 I’s of culturing microbes?

inoculation, incubation, isolation, inspection, information gathering, identification

Which of the 6 I’s of identification introduces the sample into a container of sterile media?

inoculation

Which of the 6 I’s of identification provides conditions for optimal growth?

incubation

Which of the 6 I’s of identification getting a pure culture of the microbe?

isolation

Which of the 6 I’s of identification looking at colonies and microscopic characteristics?

inspection

Which of the 6 I’s of identification involves biochemical, immunologic, and genetic testing?

information gathering

Which of the 6 I’s of identification assigns a specific name to the microbe?

identification

What factors affect microbial growth?

nutrients, temperature, pH and presence of water, atmospheric gases (O2, CO2, N2)

Which form of media contains pure organic and inorganic compounds in an exact chemical formula?

synthetic

Which form of media contains at least one ingredient that is not chemically definable (organic extracts)?

non-synthetic

Which form of media grows on a broad range of microbes, usually non-synthetic, nutrient agar and broth, peptone water, etc?

general purpose

Which form of media contains complex organic substances such as blood, serum, Hgb, or special growth factors required by fastidious microbes?

enriched

Which form of media contains one or more agents that inhibit growth of some microbes and encourage growth of the desired microbes?

selective

Which form of media allows growth of several types of microbes and displays visible differences among desired and undesired microbes?

differential

Which specific medium would be best to isolate pathogenic Staphylococci?

selective

Why is the growth curve in a bacterial culture closed?

nutrients and space are finite: no mechanism for the removal of waste products

What is the average period it takes to complete the entire bacterial growth curve?

period of 4 days

What are the four phases of the microbial growth curve?

lag, exponential growth, stationary, death

Which G+ bacteria stain like G-? Why does this happen?

actinomyces, corynebacterium, mycobacterium, and propionibacterium due to their walls being sensitive to breakage during cell division

Which bacteria respond best to acid-fast staining?

mycobacteria

Which groups of bacteria are considered obligate intracellular parasites? How are they different from non-obligate intracellular bacteria?

Rickettsia and Chlamydia: cannot survive or multiply outside of a host cell; cannot carry out metabolism on their own

What are the four main fungal divisions?

zygomycota, ascomycota, basidiomycota, chytridiomycota

Which division of fungus does not cause human disease?

chytridiomycota

What are the two morphologies in which microscopic fungi exist?

yeast and hyphae (mold)

Which division of fungus makes bread mold?

zygomycota

Which division of fungus makes yeast, penicillium, ringworm, candida albicans, and black mold?

ascomycota

Which division of fungus contributes to crypto neoformans?

basidiomycota

What is the difference between primary and opportunistic fungal pathogens? What is an example of each?

primary: exist in yeast and mold forms (dimorphic) -histoplasma, blastomyces

opportunistic: happen secondary to a weakened immune system -cryptococcus, candida

What are the two protozoan stages?

trophozoite (feeding) and cyst (resistant)

What types of marine life can cause food poisoning?

red tide, paralytic shellfish, ciguatera fish

What are the protozoan groups based on?

locomotion and reproduction

What protozoan pathogens are associated with the mastigophra group?

trypanosoma cruzi (chagas), leishmania, giardia lamblia, trich vaginalis

What are the two groups of parasitic helminths?

flatworms and roundworms

What group of helminths do tapeworms and flukes belong to?

flatworms

What group of helminths do pinworms belong to?

roundworms

What is the difference between an enveloped and naked virus?

enveloped has an envelope/covering around the capsid, naked do not

What are the six stages of virus replication?

adsorption, penetration, uncoating, duplication/synthesis, assembly, release

What cytopathic effects are caused by viruses?

damage to host cells that alters their appearance (cell lysis, alter DNA, change shape, fuse, damage)

What type of infections do prions cause?

transmissible spongiform encephalopathies (TSEs)

How do prion diseases spread?

direct contact, contaminated foods → form holes in nervous tissue

What is the name of the rapidly progressive neurodegenerative human prion disease?

Cruetzfeldt-Jakob disease

Which microbes have the highest resistance to control?

bacterial endospores

What is the goal of sterilization?

destroying endospores (kills all microbial life)

Which microbicidal agent is considered a sterilizing agent?

sporicide

What process temporarily prevents microbes from multiplying?

microbiostatic

What process or chemical agent kills pathogenic organisms?

microbicide

Which type of cleaning process is defined as any cleansing technique that mechanically removes microbes? Ex: dishwashing

sanitization

What type of cleaning process reduces the number of microbes on the human skin? Ex: surgical hand scrub

degermation

What type of cleaning process uses chemical agents on the skin to destroy or inhibit vegetative pathogens? Ex: antibacterial soap, preoperative iodine

antisepsis

What type of cleaning process destroys vegetative pathogens (not endospores) on inanimate objects? Ex: 5% bleach, boiling water

disinfection

What is microbial death?

permanent loss of reproductive capability, even under optimum growth conditions

What factors can affect an antimicrobial agent’s mechanism of action?

number of microbes, nature of microbes in the population, temperature and pH of environment, concentration of agent, mode of action of the agent, presences of solvents, organic matter, or inhibitors

What are the four cellular targets that antimicrobial agents aim to destroy?

cell wall, cell membrane, cellular synthetic process of proteins and nucleic acids: DNA and RNA, proteins structure and function

What antimicrobial agents are most effective at targeting the cell wall?

antibiotics, detergent, alcohol

What antimicrobial agents are most effective at targeting the cell membrane?

surfactants

What antimicrobial agents are most effective at targeting the cell synthetic process of proteins and nucleic acids?

antibiotics, chemicals, radiation

What antimicrobial agents are most effective at targeting the proteins structure and function?

heat, chemicals

Which form heat is most effective for microbial control? Ex: autoclave

moist heat

What is desiccation? Is it an effective method of sterilization?

gradual removal of water from cells → metabolic inhibition; NO

What is ionizing radiation?

“cold” deep penetrating, breaks DNA; gamma rays, x-rays

What is non ionizing radiation?

little penetrating, used to disinfect/sterilize air, water and solid surfaces

What is filtration?

mechanical removal of microbes by passing a gas or liquid through a filter

Which heavy metals are used for antimicrobial control?

silver and mercury

What is silver sulfadiazine ointment commonly used for?

burn patients

Which type of antibiotics are effective on a small range of microbes and target specific cell components?

narrow spectrum

Which type of antibiotics have the greatest range of activity and contain tart components common to most pathogens?

broad spectrum

What is the mechanism of action of beta-lactam antimicrobials?

interfere with cell wall synthesis

What are the most used beta-lactams?

penicillins and cephalosporins

Which form of penicillin does not penetrate the outer membrane, are less effective against G- bacteria, and considered narrow spectrum?

natural

Which form of penicillin crosses the cell walls of G- bacteria and are broad spectrum?

semisynthetic

Is carbapenem (a beta-lactam drug) narrow or broad spectrum? give examples

broad; imipenem, meropenem

Is monobactam (a beta-lactam drug) narrow or broad spectrum? give examples

narrow; aztreonam, only work on G-

What root names are associated with all generic cephalosporin medications?

-cef, ceph, or kef

How has each successive generation of cephalosporins expanded its coverage?

all cover G+; each group is more effective against G- than before

What antimicrobials can disrupt cell membrane function?

polymyxins, daptomycins, amphotericin B, nystatin

Which antimicrobials affect nucleic acid synthesis?

fluoroquinoles and antiviral drugs that are analogs of purines and pyrimidines

How do fluroquinoles stop DNA replication and repair?

bind and inhibit DNA gyrase and topoisomerases, stopping DNA replication and repair

What should you warn you patient about if you prescribe fluoroquinolone?

tendinosis and cardiac conduction issues

Which ribosomal subunit do aminoglycosides target to disrupt protein synthesis?

30S

What type of drug are aminoglycosides?

broad spectrum antibiotics

What other class of antibiotics target the 30S ribosomal subunit?

tetracyclines

Which antimicrobial interfere with protein synthesis by targeting the 50S ribosomal unit?

chloramphenicol, erythromycin, azithromycin, clarithromycin

Which antimicrobials interfere with protein synthesis by targeting both the 30S and 50S ribosomal units?

oxazolidinone