What is the significance of each of the following stages of bacterial growth?

Why are each of the following media used by microbiologists?

How does a gram-positive bacterial cell envelope differ from that of a gram-negative bacterial cell envelope?

Clinical Science Exam 1 Study Questions 1. Describe the function of the following bacterial/prokaryotic cell structures: capsule, cytoplasmic membrane, peptidoglycan layer, periplasmic space, fimbriae, glycocalyx, We also discuss several other topics like ∙ How does Seligman define the good life?
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pili, flagella. (See Microbiology, Chapter 4, pp 91-94) ● Capsule o Protects cell from phagocytosis ● Cytoplasmic membrane o Structure: Phospholipids & Proteins o Function: ▪ Selective permeability & transport ▪ Electron transport & oxidative phosphorylation ▪ Excretion of some enzymes ▪ Essential enzymes, carrier molecules ▪ Receptors, proteins of chemotactic system ● Peptidoglycan layer o The cell walls of most bacteria gain their relative strength and stability ● Periplasmic space o Between inner & outer membrane o Between cellular membrane and peptidoglycan layer o 20-40% of cell volume o Contains enzymes ● Fimbriae o Aggregate and proliferate o Small, bristlelike fibers emerging from the surface of many bacterial cells ● Glycocalyx o Develops as a coating of macromolecules to protect the cell and, in some cases, help it adhere to its environment ● Pili o Rigid surface of protein o Adherence to host o Attachment of donor & recipient cells in bacteria conjugation (pass DNA) o Allow for proliferation of organism ● Flagella o Structure: Thread-like appendages of protein (H antigen) o Organs of Motility 2. How does a gram-positive bacterial cell envelope differ from that of a gram-negative bacterial cell envelope? ● The Gram-Positive Cell Envelope o Cytoplasmic membrane o Thick​ peptidoglycan layer (cell wall) o Some have outer capsule o Outer layer of envelope and the size of that layer o Does not have outer membrane o More water solule o Cytoplasmic membrane, thick peptidoglycan layer(responsible for retaining crystal violet dyes during staining), may have a capsule o Special components: teichoic acids(water soluble polymers and major surfaceantigens) and polysaccharides ● The Gram-Negative Cell Envelope o Cytoplasmic membrane (Cell membrane) o Single sheet peptidoglycan o Complex outer membrane layer (cell wall) ▪ One layer ▪ Then lipid layer o May have outer capsule ▪ Better able to live in hostile environments ▪ Makes it easier to survive o Endotoxins (lipopolysaccharide)** ▪ Endotoxins if cell is lysed ▪ If you kill cell and patient has infection, they are released and can be toxic to individual ▪ Bacterial infection→toxic ▪ Makes gram negative dangerous o More suitable for lipids because of phospholipid bilayer ▪ Lipid soluble o Naturally resistant to penicillin o Outer membrane: protects cell from biles salts; special pores allow hydrophilic compounds to pass o LPS: endotoxin of gram neg; major surface antigen of bacteria; stabilizes outer membrane; barrier to hydrophobic molecules o Periplasmic space: between inner and outer membrane; contains enzymes 3. Why are each of the following media used by microbiologists? Enriched media, general-purpose media, transport media, selective media, differential media (blood agar, chocolate agar). (See Microbiology, Chapter 3) ● Enriched media o Contains complex organic substances such as blood, serum, hemoglobin, or special growth factors that certain species must be provided in order to grow o Organic compounds such as vitamins and amino acids that the microbes cannot synthesize themselves ▪ General purpose media o Designed to grow a broad spectrum of microbes that do not have special growth requirements o Nonsynthetic (complex) and contain a mixture of nutrients that could support the growth of a variety of bacteria and fungi o Nutrient agar and broth, TSA ▪ TSA is a complex medium that contains partially digested milk protein (casein), soybean digest, NaCl, and agar ▪ Transport media o Used to maintain and preserve specimens that have to be held for a period of time before clinical analysis or to sustain delicate species that die rapidly if not held under stable conditions o Contain buffers and absorbants to prevent cell destruction but will not support growth ● Selective mediao Contains one or more agents that inhibit the growth of a certain microbe or microbes but not another o This difference favors the one that it can’t inhibit and allows it to grow by itself o Important in primary isolation of a specific type of microorganism from samples containing mixtures of different species ▪ Feces, saliva, skin, water, and soil o Hasten isolation by suppressing the unwanted background organisms and allowing growth of the desired ones ● Differential media o Blood sugar o Chocolate agar o Grow several types of microorganisms but are designed to bring out visible differences among those microorganisms o Differences show up as variations in colony size or color, in media color changes, or in the formation of gas bubbles and precipitates o These variations come from the types of chemicals contained in the media and the ways that microbes react to them o The simplest differential media show two reaction types such as the use or nonuse of a particular nutrient or a color change in some colonies but not in others o Several newer forms of differential media contain artificial substrates called chromogens that release a wide variety of colors, each tied to a specific microbe 4. What is the significance of each of the following stages of bacterial growth? Lag phase, stationary phase, exponential phase, decline phase. (See Microbiology, Chapter 7) ● Lag phase o Flat period on graph when population is not growing or is growing at a slow rate ▪ Could be adjusting, population is sparse, or they are not multiplying at the maximum yet ● Stationary phase o Survival mode where cells stop growing or grow slowly o Rate of cell inhibition or death balances out the rate of multiplication ● Exponential phase o Infection proliferates quickly o Maximum cell division ● Decline phase (convalescent) o Infection goes away o Cells die at exponential rate and are unable to multiply 5. What environment is favored by each of the following? Aerobic bacteria, anaerobic bacteria, facultative bacteria, microaerophilic bacteria. ● Aerobic bacteria o Most oxygen and some carbon dioxide ● Anaerobic bacteria o Can not grow in the presence of oxygen, oxygen is toxic for them ● Facultative bacteria o Versatile organisms, capable of growth under both aerobic and anaerobic conditions ● Microaerophilic bacteria o Low oxygen but not no oxygen o Can grow in reduced oxygen and increased carbon dioxide 6. Compare and contrast the following terms: bacteriostatic, bacteriocidal ● Bacteriostatico Inhibits bacteria growth, can resume if conditions are right ▪ Putting food in the fridge, urine, blood, stool ● Inhibit additional proliferation, putting it back in room temperature would make it proliferate ● Bacteriocidal o Irreversibly kills bacteria ▪ Not a sporocide or tuberculocide ▪ Use spray not classified as disinfectant, reduces number of microbes 7. Why are gram-negative cells more difficult to kill with antibiotics and disinfectants? ● Endotoxins if cell is lysed ● If you kill cell and patient has infection, they are released and can be toxic to individual 8. Which of the following are capable of sterilization (i.e. kills spores)? Autoclaving, filtration, UV radiation, alcohol, ethylene oxide, irradiation. ● Autoclaving o (Saturated steam under pressure): Most common method in hospitals ▪ High heat and pressure steam ▪ Surgical tools ▪ Completely sterilizing ● Gamma radiation o Stronger, ionizing, target DNA strands of bacteria, effectively sterilize ● Ethylene oxide o Second most common method in hospitals (sterilization) ▪ Things that can’t withstand heat in a hospital ● Plastic 9. Differentiate between endotoxins and exotoxins in terms of where and how the toxin is produced and what the toxin does to the infected host. ● Endotoxin o Attach to cell wall, release if cell is lysed o Cannot be made into vaccine o Causes fever, leukopenia, hypotension, disseminated intravascular coagulation (DIC) o Gram negative cell is lysed: always make endo, but can also make exo o Once released, not infectious to vegetative cell in sight, now it is in central ▪ Harder to treat, need an antitoxin to break down toxin ● Exotoxin o Cell produces & excretes o Used to make vaccines (e.g.. Causes symptoms of TB, Tetanus, Botulism, Toxic Shock Syndrome) o Can be made by gram negative cells, not always o Less susceptible to heat ▪ Can ingest toxin (not vegetative cell) to cause poisoning o Target specific areas of body ▪ GI tract ▪ Particular organ system o General term that creates other toxins ▪ Neurotoxins, enterotoxins o Target organs are damaged; heart, muscles, blood cells, intestinal tract show dysfunctions 10. Compare and contrast the following terms: pathogen, symbiont, mutualist, opportunist. ● Pathogeno Organism capable of causing disease ● Symbiont o Relationship between two species ● Mutualist o A relationship between individuals of different species in which both individuals benefit ● Opportunist o Organism only causes disease when host defenses are impaired ▪ Can harbor on human host for life and they never become sick ▪ Could be colonized with MRSA ● Staph infections, medication resistant ▪ Competitive inhibition of the organisms, no overgrowth, could get perforation or reduction in immune system and infection could occur 11. Define the following terms: fomite, biological vector, and droplet nucleus. ● Fomite o Virtually any inanimate object an infected individual has contact with that can serve as a vehicle for the spread of disease ● Biological vector o A carrier, like an animal, that transfers an infective agent from one host to another ● Droplet nucleus o The dried residue of fine droplets produced by mucus and saliva sprayed while sneezing and coughing. Droplet nuclei are less than 5 µm in diameter (large enough to bear a single bacterium and small enough to remain airborne for a long time) and can be carried by air currents. Droplet nuclei are drawn deep into the air passages 12. What effect does each of the following virulence factors have on an infected host? Hyaluronidase, streptokinase, erythrogenic toxin, enterotoxin. ● Hyaluronidase o Breaks down hyaluronic acid, an important component of connective tissue o Allows organism to spread ● Streptokinase o Causes fibrin to be digested o Used to treat pulmonary emboli and coronary thrombosis ● Erythrogenic toxin o Causes rash in scarlet fever o An exotoxin produced by lysogenized group A strains of b-hemolytic streptococci that is responsible for the severe fever and rash of scarlet fever in the nonimmune individual. Also called a pyrogenic toxin. ● Enterotoxin o A bacterial toxin that specifically targets intestinal mucous membrane cells. Enterotoxigenic strains of Escherichia coli and Staphylococcus aureus are typical sources. 13. Which areas of the body have an acid pH as a natural host defense? (See Chapter 13) ● Mouth ● Stomach ● Intestines 14. Which areas of the body are normally free of microorganisms? (See Chapter 13) ● Internal organs and tissues and fluids o Lung o Sinuso Kidney o Blood o Fetus 15. Describe how wounds should be cultured ● Swab Culture o Difficult to obtain without contaminating specimen o Prepackaged sterile culture tube (with medium) USE 2 Calcium alginate swab o If eschar (eskar) (hardened necrotic tissue, esp. burns) present, need to debride (dabreed) first o Avoid touching swab to intact skin at wound edges o Send to lab within 1-2 hrs max ● Aspiration Culture (MD or APRN) o Prep site with alcohol o Use 3 ml syringe, 22 gauge needle, take 1 ml fluid ● Tissue Biopsy (surgery, burn wounds) - damages tissue 16. What is the significance of finding squamous epithelial cells in a lab specimen taken for a bacterial culture? ● If there are squamous cells, it is a bad specimen o Should not be processed 17. Which organism(s) can cause endocarditis following dental work in individuals with prosthetic heart valves or a history of rheumatic fever? ● Gingivitis ● Staphylococcus epidermis causes endocarditis 18. What is the most likely cause (organism) of diarrhea in a patient who has been on long-term (1 month) antibiotic therapy? Give examples of antibiotics that can cause this. ● C. difficile ● Penicillins o Amoxixillin 19. What patient characteristics place them at risk for developing methicillin resistant Staphylococcus aureus and vancomycin resistant enterococcus? ● MRSA o Multiple antibiotic treatment o Broad-spectrum agents o Prolonged antibiotic therapy o Poor nutrition status o 50% of colonized pts develop infection o Trauma, burns, aged, immunocompromised o Now can be community acquired! o Being hospitalized, catheters, long-term care facility ● VRE o Resistance to cephalosporins, penicillins, & aminoglycosides o Hospitalized with long periods of antibiotics o Weak immune system ▪ ICU ▪ Cancer ▪ Transplant wards ▪ Surgery o Catheters 20. Which organism is the most common bacterial cause of community-acquired (i.e. acquiredoutside the hospital) pneumonia? ● Streptococcus pneumoniae 21. What is the mechanism of post-streptococcal acute glomerulonephritis? ● Can develop 3 weeks after untreated infection ● Due to antigen - antibody complexes ● Inflammation 22. Know the gram stains and shape of each organism we discussed in class. (E.g. a gram-negative diplococcus is Neisseria.) ● Staphylococci - Gram positive, not crystallizing ● Streptococci - Gram positive, spherical shape ● Neisseriacea - Gram negative, Cocci in pairs (diplococci) 23. List 3 organisms that can cause nosocomial infections in hospitalized patients. Explain how each is acquired. If transmission is possible, how can transmission be prevented? ● Staphylococcus aureus ● Pseudomonas aeruginosa ● E. coli ● Selected by therapy w/ cephalosporins ● Transmitted between patients / staff via hands 24. Who should be given a Streptococcus pneumoniae vaccine? ● Appropriate for day care kids, those with sickle cell, age >50 or 60 (there are 2), debilitated, immunosuppressed o Older adults-pneumovac ● All children 22-23 months of age need to be vaccinated 25. What hospital items may be reservoirs for multiple drug resistant staph. aureus (MDRSA) and VRE? ● Staff ● Patients ● Beds ● Linens ● Utensils ● Colonize in o Wounds o Nostrils o Armpit o Groin 26. What are the early symptoms of necrotizing fasciitis arising from a wound infected with Streptococcus pyogenes? ● Small place where skin is broken down, excessive pain ● Top of the cut looks bruised and is smaller than the amount of pain 27. How can wounds be treated to reduce the risk of developing necrotizing fasciitis? ● Hydrogen peroxide o Catalase negative (all strep is) 28. What are the symptoms of infections from Staphylococcus aureus? ● Purulent exudate, enlarged nodes, high fever ● Wounded skins/ burns result in widespread infection that may progress to cellulitis 29. List 4 diseases caused by spore forming bacteria. What are the symptoms of each? ● Bacillus anthracis: The bacteria can multiply in the blood giving rise to (rapidly fatal) septicemia o If the spores enter shallow skin abrasions they can give rise to localised (andnon-fatal) Cutaneous anthrax  ● Bacillus cereus: growing bacteria leaves a heat stable toxin in the food as it grows, causing anyone who eats it vomiting and diarrhea  ● Clostridium perfringens: small focus of infection, which can spread as the bacteria are able to produce numerous toxins which break down the patient's tissue o If food harbouring C.perfringens is eaten it may give rise to food poisoning o Sometimes fatal ● C. difficile: can be found in comparatively small numbers in many peoples intestines and is easily acquired by those who don't have it when in near contact with those that do (ie hospital) o If someone with this bacteria is treated with a broad spectrum antibiotic many of the more common gut bacteria are killed allowing the C.difficile(which is resistant) to overgrow and become the dominant organism o This in turn disrupts the normal function on the intestine giving rise to diarrhoea and inflammation ● C. tetani: if embedded in a deep wound it can start to grow producing a powerful neurological toxin which causes muscles to contract involuntarily and permanently o This is "Tetanus" (or Lockjaw) can be fatal if the toxin reaches heart or lung muscle  ● C. botulinum: The agent of botulism, a deadly form of food poisoning o Spore-forming anaerobe that commonly inhabits soil and water and, occasionally, the intestinal tract of animals 30. What would you expect to see in a urethral smear that is positive for Neisseria gonorrhea? ● Diplococci o Aggregation in pairs ● Gram negative 31. What are the symptoms of meningitis? ● Fever ● Sore throat ● Headache ● Stiff neck ● Convulsions ● Vomiting 32. What factors increase the risk of developing bacterial meningitis? ● Being in close quarters o Day care o College o Military base ● Time of year o Late winter o Early spring ● Age o 3-36 months o 10-20 years ● Not having the vaccine 33. Compare and contrast the time of onset and symptoms of food poisoning/food infection caused by: Clostridium perfringens, Staphylococcus aureus, Clostridium botulinum. ● Clostridium perfringens o Majority of clostridial soft tissue and wound infections are caused by o Spores of these species can be found in soil, on human skin, and in the humanintestine and vagina o The disease they cause has the common name gas gangrene ▪ In reference to the gas produced by the bacteria growing in the tissue. It is technically termed anaerobic cellulitis or myonecrosis o The conditions that predispose a person to gangrene are surgical incisions, compound fractures, diabetic ulcers, septic abortions, puncture and gunshot wounds, and crushing injuries contaminated by spores from the body or the environment. o Infection requires damaged or dead tissue that supplies growth factors and an anaerobic environment. o The low oxygen tension results from an interrupted blood supply and the growth of aerobic contaminants that deplete oxygen o Due to this interaction, gas gangrene is considered a type of mixed infection. These conditions stimulate spore germination, rapid vegetative growth in the dead tissue, and release of exotoxins. ● Staphylococcus aureus o Food preparer touches face, then food o With time, temp., S. aureus grows, releases toxin ▪ Time, temp affect likelihood of intoxication o Onset is quicker than food borne infection o Ex. egg salad, cream fillings, lime pie ● Clostridium botulinum o The agent of botulism, a deadly form of food poisoning o Ingestion of this potent exotoxin leads to flaccid paralysis. o Home canned or poorly preserved low acid foods o Recent cases involved vacuum-packed food, can be fatal o Spore-forming anaerobe that commonly inhabits soil and water and, occasionally, the intestinal tract of animals o Distributed worldwide but occurs most often in the Northern Hemisphere. The species has eight distinctly different types (designated A, B, Ca and Cb, D, E, F, and G), which vary in distribution among animals, regions of the world, and type of exotoxin produced 34. What is the target organ that is damaged by each of the following clostridial species: C. botulinum, C. difficile, C. tetani, C. perfringens. ● C. botulinum (food poisoning) - paralysis ● C. difficile - can produce toxins that attack the lining of the intestine ● C. tetani (lockjaw) - jaw ● C. perfringens - brain