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PA Microbiology 1
Bacterial morphology, growth genetics, human flora, pathogenesis, antibiotics
| Question | Answer |
|---|---|
| What are the 3 types of phenotypic classification? | 1. Biotyping 2. Serotyping 3. Susceptibility |
| Biotyping does identifies WHAT by WHAT METHOD? | Biotyping identifies SPECIFIC BACTERIA by identifying BIOCHEMICAL MARKERS |
| What is the special feature and identification method of Serotyping? | Special Feature: Rapid identification Identification Method: Detects unique surface antigens |
| What technique/test is used to determine bacterial susceptibility? | Kirby Bauer Test |
| What is the basis of the Kirby Bauer Test? | diameter/ measure zone of inhibition |
| What is an antibiogram? | A report of antibiotic susceptibilities of various bacteria |
| Which bacterial classification method is the most precise? | Genotyping |
| What laboratory technique is utilized in genotyping? How does it work? | PCR- amplifies genes/DNA for sequencing and matching to a specific bacterium |
| What are the 6 classes of bacterial shapes? | 1. Coccus 2. Bacillus 3. Coccobacillus 4. Vibrio 5. Spirillum 6. Spirochete |
| What is the definition of a coccus-shaped bacteria? | Round/Sphere |
| What is the definition of a bacillus-shaped bacteria? | Rod |
| What is the definition of a coccobacillus-shaped bacteria? | Short rod |
| What is the definition of a vibrio-shaped bacteria? | Curved rod |
| What is the definition of a spirillum-shaped bacteria? | Rigid, spiral-shaped rod |
| What is the definition of a spirochete-shaped bacteria? | Flexible, thin, spiral-shaped rod |
| What is the difference between Spirillum and Spirochete shapes? | Spirillum is a RIGID, spiral-shaped rod. Spirochete is a FLEXIBLE, THIN, spiral-shaped rod |
| Different bacterial structural arrangements are typically associated with what shape? | Coccus |
| What are the 4 different morphological arrangements of bacteria? | 1. Diplo 2. Strepto 3. Staphylo 4. Tetrad |
| What is the definition of a bacteria with a diplo arrangement? | Pair (2) |
| What is the definition of a bacteria with a Strepto arrangement? | Chain |
| What is the definition of a bacteria with a Staphylo arrangement? | Grape-like cluster |
| What is the definition of a bacteria with a Tetrad arrangement? | pack of 4 cells |
| What is a major difference between human cell membranes and most bacterial cell membranes? | Lack of sterols/cholesterol in bacterial cell membranes |
| Which bacteria contain sterols/cholesterol in their cel membranes and are therefore similar to human cell membranes? | Mycoplasma and Ureaplasma = Respiratory and Urogenital infections |
| What are the 6 functions of bacterial cell membranes? | 1. Regulate transport 2. Synthesize cell wall components 3. Attachment site for chromosomes during cell division 4. Secrete proteins 5. Site of Cellular Respiration and ATP production 6. Anchors flagella |
| What is the main structural component of bacterial cell walls? | Peptidoglycan |
| What is the structural components of Peptidoglycan backbone? | Repeating NAG and NAM disaccharides |
| What is the linking of the disaccharides in the peptidoglycan backbone called? | Transglycosylation |
| What is the cross-linking of the peptides in the peptidoglycan backbone called? | Transpeptidation |
| Why is the cell wall an antimicrobial target? | It is not present in humans... aka it is unique to bacteria |
| What is the primary stain in a gram stain? | Crystal Violet (Purple/blue in color) |
| What is the Counterstain in a gram stain? | Safranin (Pink/Red in color) |
| What color does a G+ bacteria stain, and what is the reason for this? | Blue/Purple... thick peptidoglycan layer of cell wall retains the Crytal Violet stain |
| What color does a G- bacteria stain, and what is the reason for this? | Pink/Red...thin peptidoglycan layer of cell wall does not retain Crystal Violet stain, but retains Safranin stain |
| The G- cell envelope contains which structures not found in G+ cell envelopes? | Periplasmic space, and outer membrane |
| What notable structure is found in the outer membrane of G- cells? | LPS... aka endotoxin |
| Name the 3 parts that make up the LPS/Endotoxin structure? | 1. Lipid A 2. Core Polysaccharide 3. O Antigen |
| What role does Lipid A play in the function of LPS endotoxin? | Lipid A is the virulence factor... elicits a toxic response from the immune system= it is the endotoxin |
| What is the function of the core polysaccharide in the LPS/Endotoxin of G- bacteria? | Links Lipid A to the O Antigen |
| What is the function of the O Antigen, a component of the LPS/Endotoxin of G- bacteria? | It is composed of carbohydrates; it's structure is species and strain specific, which makes it useful in identifying bacterial strains (Serotyping) |
| What causes the onset of Systemic Inflammatory Response Syndrome (SIRS)? | Release of cytokines due to the release of LPS/Endotoxin |
| What are the 4 clinical manifestations of Systemic Inflammatory Response Syndrome (SIRS)? | 2 or more of: 1. Temperature >38*C or <36*C 2. Tachycardia >100 bpm 3. Tachypnea >20 breaths/min 4. Leukocytosis >12,000/mm^3 or Leukopenia <4,000/mm^3 |
| Why is it important not to kill G- bacteria too quickly? | Cell lysis causes release of Lipid A/Endotoxin. Lots of Lipid A may induce SIRS, which can lead to Septic Shock or Multiple Organ Dysfunction Syndroms (MODS) |
| What is the location and function of porins in G- cell envelopes? | Porins are 3-part proteins found in the OUTER MEMBRANE that control diffusion of small metabolites (sugars, amino acids, ions) |
| What Cell Envelope component(s) is/are unique to G+ bacteria? | Teichoic/Lipoteichoic acids in the peptidoglycan/Cell Wall |
| What is the function/purpose of teichoic acid in the G+ cell wall? | Allows bacteria to adhere/attach to other cells |
| What is the function/purpose of lipoteichoic acid in the G+ cell wall? | They are anchored to the cell membrane |
| What action of G+ bacteria causes a release of inflammatory cytokines in humans? | Shedding of the cell wall containing teichoic/lipoteichoic acids = virulence factors |
| Which antibiotics target the bacterial cell wall to inhibit peptidoglycan synthesis/transpeptidation? | Beta lactams (Penicillin, cephalosporins) and Vancomycin |
| What is the target of antibiotics such as Beta lactams (Penicillin and cephalosporins) and Vancomycin? | Peptidoglycan synthesis/transpeptidation |
| What are 4 antibiotics/classes of antibiotics that target the cell wall? | 1. Beta lactams (Penicillin, cephalosporins) 2. Vancomycin 3. Bacitracin 4. Cycloserine |
| What effect does a lysozyme have on bacteria? | Lysozymes are lytic enzymes that degrade the glycan backbone/peptidoglycan of bacterial cell wall |
| Lysozymes function under which class of immune system: Innate or Adaptive? | Innate |
| Where are lysozomes found in humans? | Tears, saliva, mucus, WBC lysosomes |
| What Cell Envelope structural feature is unique to Acid-Fast bacteria? | Mycolic Acid layer (outermost layer) |
| What is the purpose/function of the mycolic acid layer in Acid-Fast bacteria? | Mycolic Acid creates a waxy coat, enabling the bacterial cell to resist desiccation, some antibiotics, and phagocytosis |
| What is the Ziehl-Neelsen or Kinyoun Stain used to identify? | Acid-Fast Bacteria |
| What color do Acid-Fast bacteria stain in Ziehl-Neelsen or Kinyoun Stains? | Red... retains primary stain of Carbol fuchsin |
| What color do non-acid fast bacteria stain in Ziehl-Neelsen or Kinyoun Stains? | Blue...cell retains methylene blue counterstain |
| Where is the glycocalyx of bacteria located? | Outside the cell wall |
| In which bacterial classifications is the glycocalyx found? | G+ and G- |
| What important structure does the Glycocalyx contain? | K antigen (*serotyping) *E. coli K12 |
| What are 4 important functions of the glycocalyx? | 1. Protect against desiccation 2. Acts as a barrier to toxic hydrophobic molecules (antibiotics) 3. Inhibits phagocytosis 4. Promotes adherence to other cells (bacterial/host, etc.) |
| What bacterial structural component is responsible for biofilm formation? | Glycocalyx- Slime layer |
| What are the 2 forms of glycocalyx? | 1. Slime layer 2. Capsule |
| What are the differentiating characteristics between the slime later glycocalyx and capsule glycocalyx? | Slime layers are loose, non-uniform, and diffuse **Partake in biofilm formation Capsules are rigid, uniform, and closely surround cell |
| What are the 3 common locations of biofilm formation? | 1. Catheters 2. Teeth 3. Mucous membranes of GI Tract |
| What is the Quellung test used for? | To identify a capsule glycocalyx |
| ?Which 4 bacteria are known to have a capsule glycocalyx? | 1. Streptococcus 2. Haemophilus 3. Klebsiella 4. Neisseria |
| What is the source of the H antigen? | Flagella. Used in serotyping |
| What are the 2 different arrangements of flagella? | 1. Polar 2. Peritrichous |
| What is the meaning of peritrichous? | Flagella is positioned laterally/over entire cell surface |
| What is the function of fimbria(e)? | To adhere to other bacteria/host cells |
| What is the arrangement of fimbriae on a bacterial cell? | Peritrichous |
| What is the function of a Pilus (pili)? | Attach and bring other bacterial cells close for DNA transfer |
| What 3 types of Pili are there? | 1. Sex pilus 2. F pilus 3. Conjugation pilus |
| What is the unique ribosomal structure of bacteria? | 70S ribosomes *30S and 50S subunits (odd digits) |
| What is the ribosomal structure of eukaryotes? | 80S ribosomes *40S and 60S subunits (even digits) |
| Which 2 antibiotics classes target the 70S ribosomes of bacteria? | 1. Aminoglycosides (streptomycin) 2. Macrolides (erythromycin) |
| What is a unique feature of bacterial nuclear/DNA-containing region? | There is no nuclear membrane |
| What 2 benefits does lack of a nuclear membrane offer bacteria? | 1. Faster protein synthesis (Transcription and translation are coupled) 2. Coupled T&T plus polysomes allow quick enzyme/structural protein responses to changing environments |
| What are the benefits to bacteria of producing endospores? | They are in a dormant, protective stage that is resistant to harsh environments (heat, disinfectants, acids, etc.) |
| ?What are 3 G+ bacterial genera that produce endospores? | Bacillus (G-?) and Clostridium |
| What are the 4 phases of bacterial growth? | 1. Lag phase = metabolically active but not dividing 2. Log/Exponential phase = Rapid division at a constant rate 3. Stationary phase = rate of cells dividing equals rate of cells dying 4. Decline/Death phase = Cells die at a log rate |
| What is a clinical application of acute bacterial infections? | They have a short doubling time... they require only short-term treatment |
| What is a clinical application of chronic bacterial infections? | They have a long doubling time... they require long-term treatment |
| What are the 3 classes of bacteria whose growth is affected by pH? | 1. Acidophiles: pH <5.4 2. Neutralophiles: pH b/w 5.4-8.5* 3. Alkaliphiles: pH >8.5 |
| What pH class is the greatest threat to humans? | Neutralophiles |
| What are the 3 classes of bacteria whose growth is affected by temperature? | 1. Psychrophiles: 15-20*C 2. Mesophiles: 25-40*C 3. Thermophiles: 50-60*C |
| What temperature class of bacteria is the greatest threat to humans? | Mesophiles |
| What is the definition of obligate? | obligated/requires; Physically and biochemically limited to one specific habitat |
| What is the definition of facultative? | able to adapt to specific environmental conditions and can survive under a range of conditions; physically and biochemically able to adapt to more than onehabitat |
| Bacteria are divided into which 5 groups according to their oxygen requirements? | 1. Obligate Aerobes 2. Obligate Anaerobes 3. Facultative Anaerobes 4. Microaerophiles 5. Aerotolerant Anaerobes |
| What is the oxygen requirement of obligate aerobes? | MUST have O2 present. *Mycobacterium tuberculosis |
| What is the oxygen requirement of obligate anaerobes? | O2 must NOT be present. *Clostridium botulinum |
| What is the oxygen requirement of facultative anaerobes? | They can grow with or without O2. They prefer O2 = aerobic metabolism, but can use fermentation without O2. *E. coli |
| What are the 2 products of bacterial fermentation? | 1. Lactic Acid 2. H2 gas |
| What product of bacterial fermentation is responsible for dental caries? | Lactic Acid |
| What product of bacterial fermentation is responsible for gangrene? | H2 gas |
| Lactic acid production from bacterial fermentation can cause what health problem in humans? | Dental caries |
| H2 gas production from bacterial fermentation can cause what health problem in humans? | Gangrene |
| What is the oxygen requirement of microaerophiles? | Require small amounts of O2 *Treponema pallidum |
| What is the oxygen requirement of aerotolerant anaerobes? | Survive in the presence of O2 but do not utilize O2 *Lactobacillus acidophilus |
| What is the importance of Superoxidase dismutase (SOD)in certain bacteria? | It converts superoxide O2 to H2O2 = antioxidant = neutralizes O2 radicals |
| What is the importance of Peroxidase or Catalase in certain bacteria? | They decompose H2O2 |
| What enzymes do obligate anaerobes lack that make their exposure to oxygen lethal? | Superoxidase dismutase (SOD), Catalase, and Peroxidase |
| What environment are halophiles adapted to survive in? | High salt. *Vibrio cholerae *S. aureus |
| What is the difference between Fastidious and Nonfastidious nutritional requirements in bacteria? | Nonfastidious bacteria can grow in standard lab media Fastidious bacteria require specific nutrients for survival |
| Clostridium- growth requirements | C. botulinum = obligate anaerobe |
| Bacillus | |
| E. coli- gram class, defining structural features, growth requirements | G-, Have H and O antigens (=flagella and LPS/Endotoxin/identifiable by serotyping), facultative anaerobe |
| S. aureus- gram class, growth requirements | G+, Facultative Halophile, Coagulase + |
| S. pyogenes- infection, defining structural feature | Cause acute infection = short treatment, streptococcus have capsule glycocalyx, Beta hemolysis |
| Antibiotic resistance is transferrable between bacteria via what structure? | Plasmid |
| What are the 3 processes bacteria use for genetic exchange? | 1. Transformation 2. Conjugation 3. Transduction |
| What does the process of transformation entail? | Naked DNA released from a lysed cell is uptaken by a COMPETENT bacteria. |
| What does the process of conjugation entail? | Sex pilus brings two bacterial cells into contact, where DNA is exchanged b/w cells *plasmids or chromosome segments |
| What are the 3 ratings used to describe effects of acquiring new genes in bacteria? | 1. Positive = gene is beneficial 2. Negative = inserted gene causes inactivation 3. Null = no change in gene |
| What does the process of transduction entail? | Injection of DNA into a bacterium by a bacteriophage/virus |
| What are the 2 types of transduction? | 1. Generalized 2. Specialized |
| What is the process of Generalized Transduction? | A virulent phage (intent to kill) infects a bacterial cell, replicates, &bacterial DNA (fragments) is packaged into a newly-formed viral capsid rather than viral DNA=defective phage. The lytic cycle is induced from start & utilized to release new phages. |
| What is the process of Specialized Transduction? | A temperate phage (stays dormant in cell until lytic cycle induced) infects a host bacterial cell, inserts viral DNA into chromosome = prophage. When lytic cycle is induced, bacterial DNA near viral DNA is packaged into a capsid. |
| What are the 4 parameters that regulate the type of bacteria in a flora population? | 1. Physiology 2. Age 3. Geographic habitat/location 4. Diet |
| What are 4 benefits provided by normal bacterial flora? | 1. Induce cross-reacting antibodies to stimulate an immune response in pathogenic bacteria 2. Produce K and B vitamins 3. Compete with pathogens for nutrients 4. Produce substances that inhibit/kill pathogens |
| Describe the concept of tissue tropism. | The physiological/environmental factors specific to certain tissues/areas of the body select for/against specific flora/bacteria |
| What are two factors that facilitate the concept of tissue tropism? | 1. Growth factors availability varies depending on habitat/tissue type 2. Receptor sites for microbe attachment vary depending on habitat/tissue type |
| What 2 conditions may cause normal flora to cause disease? | 1. Displacement Ex:Endocarditis when oral bacteria enter bloodstream, or UTI when intestinal bacteria enter urinary tract 2. Prolonged antibiotic use causing species overgrowth. Ex: C. albicans = yeast; C. difficile |
| What is the function of coagulase? | Converts fibrinogen to fibrin. Forms clots that prevents WBC access/phagocytosis |
| What genus is the coagulase test used to differentiate? | Staph |
| Which species tests positive for coagulase? | Staph aureus |
| What is the function of hemolysin? | Lyses RBC membranes. *Hemolysis test uses blood agar |
| What genus is the hemolysis test used to differentiate? | Streptococci |
| Complete/Beta hemolysis is produced by what bacteria, and what results are seen? | Strep pyogenes, and Strep agalactiae produce a white colony with a clear halo. |
| Partial/Alpha hemolysis is produced by what bacteria, and what results are seen? | Strep mutans produce a gray/green colony with a partial halo. |
| What 2 structures in the skin are responsible for inhibiting most bacterial and fungi growth? | Sebaceous glands = fatty acids, Sweat glands = salt |
| What are 3 bacterial genus/species that are resident flora of dry skin, and what is their gram-type? | Gram Positive 1. Staph epidermidis 2. Proprionibacterium acne 3. Corynebacterium spp. |
| What are the oxygen requirements, coagulase activity, and salt tolerance of the dry skin resident Staphylococcus epidermidis? | Gram positive Facultative anaerobe Coagulase negative Halophile |
| A Mannitol salt agar turns from red to yellow with the growth of a bacteria. What might the identity of the bacteria be? | Staphylococcus epidermidis... Staph. |
| In addition to Staph epidermidis, Propionibacterium acnes, and Diphtheroids found as resident flora on dry skin, what 2 other bacteria reside on moist skin, and what is their gram type? | Gram negative 1. E. coli 2. Acinetobacter sp. |
| What transient skin resident is commonly found in the nose? | Staph aureus |
| What transient skin resident is commonly found around the perineum and thighs of diabetics, and is also associated with gas gangrene? | Clostridium perfringens |
| What is the predominant resident 2 bacteria found in the mouth, and what is their gram type? | Gram positive 1. Viridans Streptococci 2. Strep mutans |
| What bacterial species is responsible for formation of dental plaque and caries? | Strep mutans |
| What 5 bacteria are commonly found in the eye/conjunctiva, and what are their gram types? | Gram Positive: 1. Staph epidermidis 2. Staph aureus *rare 3. Streptococcus pneumoniae Gram Negative: 4. Neisseria spp. 5. Moraxella catarrhalis |
| What 2 types of bacteria are comon in the naso- and oropharynx of the upper respiratory tract, and what is their gram type? | Gram positive 1. viridans streptococci 2. Strep. pneomoniae |
| What 6 G- bacteria are common in the upper respiratory tract, and what are their shapes? | Diplococci 1. Moraxella catarrhalis 2. Neisseria meningitidis Bacilli 3. E. coli 4. Klebsiella sp. 5. Proteus sp. Pleomorph 6. Maemophilus influenzae |
| Which structures in the body should be relatively sterile when healthy? | Sinuses, lower respiratory tract, synovial fluid, bladder urine, spinal fluid, bone, muscle, blood, connective tissue, kidneys, bladder |
| What two components of the GI tract help to control bacterial populations? | Acidic pH, and bile |
| What are the two bacterial species common in the stomach, and what are their gram types? | Gram positive 1. Lactobacillus sp. Gram negative 2. Helicobacter pylori |
| What 2 bacterial species are common in the duodenum and jejunum and what is their gram type? | Gram Positive 1. Lactobacillus sp. 2. Enterococcus faecalis |
| What 2 bacterial species are common in the colon, and what are their gram types? | ANAEROBES Gram positive: 1. Bifidobacterium sp. **breast fed infants Gram negative: 2. Bacteroides sp. **Meat-lovers |
| What is the predominant microbe in the vagina during child-bearing years, and what is its gram type? | Gram Positive: Lactobacillus acidophilus |
| What vaginal-residing microbe can cause neonatal meningitis and should be screened for in pregnant women? | Gram Positive Streptococcus agalactiae |
| What are the 4 points of Koch's Postulates? | 1. Same bug found in diseased-of-interest ppl, but not in healthy ppl 2. Bug isolated and grown in culture 3. Isolated bug must cause original disease when inoculated in healthy person 4. Bug re-isolated from new victim |
| What are 2 potential problems with Koch's Postulates? | 1. Not all microorganisms grow well in labs/mediums 2. The disease may be a result of bacterial co-infection |
| What is the difference between opportunistic and virulent pathogens? | Opportunistic pathogens can be a part of normal flora, & do not produce disease in their normal habitat. Also if the patient's defenses are down: trauma, defective immune system, preexisting condition. Virulent pathogens are always associated with diseas |
| Name 6 examples of opportunistic pathogens and their gram type. | 1. Staph aureus (G+) 2. E. Coli (G-) 3. Candida albicans (acid fast) 4. Clostridium difficile (G+) 5. Pseudomonas aeruginosa (G-) *burn victims/cystic fibrotic lungs 6. Nocardia asteroides (G+) *lungs in immuno-compromised ppl |
| Name 2 examples of virulent bacteria and their gram type. | 1. Mycobacterium tuberculosis (acid fast) 2. Neisseria gonorrheae (G-) |
| What are 4 mechanisms by which bacteria cause disease? | 1.Metabolic by-products destroy tissues 2. Invasins damage local tissues/cells to help pathogen grow/spread 3. Adhesins allow bacteria to attach to host cell/tissue receptors 4. Toxins |
| Streptococcus mutans uses which pathogenic mechanism to cause dental caries? | Production of lactic acid as a metabolic byproduct |
| What are the 4 types of invasins used by pathogens to help their spread/growth? | 1. Hyaluronidase destroys hyaluronic acid in connective tissue *flesh-eating 2. Collagenase breaks down collagen in muscles 3. Neuraminidase degrades neuraminic acid within cells 4. Streptokinase/Staphylokinase break down blood clots- fibrinolysins |
| What are the 3 targets for adhesins of pathogens to bind? | 1. Glycoproteins/carbohydrates *biofilms 2. Fimbriae/pili 3. Afimbrial adhesins/proteins on cell envelope |
| What are the 3 types of toxins utilized by pathogenic bacteria? | 1. Exotoxins are secreted into ECF and bind host cell receptors 2. Enterotoxins bind host cell receptors and are commonly associated with GI symptoms 3.Superantigens activate T cells in antigen absence and cause massive cytokine release |
| What are the 2 important components of exotoxins and their functions? | 1. B subunit binds toxin to the host cell 2. A subunit attacks cell |
| Name 2 diseases caused by toxins. | 1. Tetanus 2. Botulism |
| What is a toxoid? | A denatured toxin that provokes an immune response; used in vaccines |
| What is a functional exotoxin? | An active toxin that elicits an immune response and is deadly at very low concentrations |
| How does a membrane-active exotoxin function, and what are 3 examples? | They attack the cell membrane of host cells. Ex: 1. Proteases 2. Lipases 3. Hemplysins *targets RBCs and phagocytes. *Strep pyogenes |
| What is an example of a condition caused by a superantigen? | Toxic Shock Syndrome- Staph aureus |
| What is an example of an endotoxin? | LPS in (G-)... Lipid A is the toxic component |
| Name 2 methods by which bacteria evade an immune response. | 1. Encapsulation with poorly antigenic polysaccharide, deters phagocytosis 2. Intracellular growth to escape detection |
| What are the 5 stages of disease? | 1. Incubation 2. Prodromal 3. Acute 4. Decline 5. Covalescent |
| Describe the signs and symptoms, immune system activity, pathogen, and whether the stage is contagious in the Incubation stage. | Signs and Symptoms: None Immune Response: Not Activation Pathogen: dose must be infectious Contagious: No |
| Describe the signs and symptoms, immune system activity, pathogen, and whether the stage is contagious in the Prodromal stage. | Signs and Symptoms: Early s&s begin, non-specific Immune Response: Innate immune system activated Pathogen: Numbers increased since incubation Contagious: yes |
| Describe the signs and symptoms, immune system activity, pathogen, and whether the stage is contagious in the Acute stage. | Signs and Symptoms: Characteristic of disease Immune System: Acquired immune system is now activated, either pathogen or immune system is winning Pathogen: Stationary numbers +/- Contagious: Yes |
| Describe the signs and symptoms, immune system activity, pathogen, and whether the stage is contagious in the Decline stage. | Signs and Symptoms: Dwindling Immune System: Reduced activity, antibodies have been formed Pathogen: cleared from host Contagious: only if host becomes a carrier |
| Describe the signs and symptoms, immune system activity, pathogen, and whether the stage is contagious in the Convalescent stage. | Signs and Symptoms: None Immune System: Not active toward pathogen Pathogen: Cleared from host Contagious: No... no pathogen present |
| What is the difference between bactericidal and bacteriostatic antibiotics? | Bactericidal antibiotics kill the target organisms. Bacteriostatic antibiotics inhibit growth of target organisms. |
| In what patient population should bacteriostatic drugs not be used? | Immunocompromised |
| What is one major difference between eukaryotes and prokarytoes that allow for selective toxicity? | Ribosomes : 70S in prokaryotes, 80S in eukaryotes |
| What structure is very similar between eukaryotes (humans/fungi) that make selective toxicity difficult? | Cholesterol in human cell membranes, and ergosterol in fungal cell membranes have very similar structures. |
| What are 7 important properties in an effective antibiotic? | 1. Soluble in bodily fluids 2. Selective toxicity 3. Toxicity not easily altered 4. Nonallergenic 5. Stable, degraded/excreted slowly 6. Resistance not easily acquired 7. Reasonable cost |
| What are the 5 classes of antibiotics, separated according to their target? | 1. Cell wall synthesis inhibitors 2. Disrupt cell membrane function 3. Inhibit protein synthesis 4. Inhibit nucleic acid synthesis 5. Acts as an antimetabolite |
| What is the mechanism of action of cell wall inhibitors (antibiotics)? | They interfere with peptidoglycan synthesis *G+ and G-. *Bactericidal |
| Which antibiotics function as cell wall inhibitors? | Beta lactams Vancomycin Cycloserine Bacitracin |
| What compound is responsible for beta lactam resistance? | Beta lactamase |
| What are 3 penicillin analogs given in combination to increase sprectrum activity? | 1. Clavulanic acid (given with amoxicillin or ticarcillin) 2. Sulbactam (given with ampicillin) 3. Tazobactam (Piperacillin) |
| What is the relationship between gram activity and cephalosporin generation? | Higher generations (1 to 4) have increasingly greater G- activity |
| Which Cephalosporin generations are able to cross the BBB? | 4th and some 3rd = meningitis |
| Which cephalosporin generations have an increased resistance to beta lactamase? | 3rd and 4th |
| What antibiotic functions by disrupting the cell membrane? | Polymyxins |
| What is the mechanism of action of cell membrane disrupters/polymyxins? | Act as a cationic detergent and disrupts lipid bilayers |
| Why are cell membrane disrupters/ polymyxins only used on localized, external infections? | They are toxic to the host... not specific to bacteria |
| Which two classes of antibiotics target the 30S ribosome to inhibit protein synthesis? | 1. Aminoglycosides 2. Tetracyclines |
| Are aminoclycosides bacteriostatic or bactericidal? | Bactericidal |
| Are tetracyclines bacteriostatic or bactericidal? | Bacteriostatic |
| What is a major contraindication of tetracycline? | Children/Pregnant women... they chelate Ca = inhibit bone growth |
| What two classes of antibiotics target the 50S ribosome to inhibit protein synthesis? | 1. Chloramphenicol *causes aplastic anemia 2. Macrolides (Erythromycin, Clarithromycin, Azithromycin) |
| What two classes of antibiotics functions by inhibiting nucleic acid synthesis? | 1. Rifamycins (Rifampin) 2. Fluoroquinolones |
| What is the specific target of Rifampin? | Inhibits transcription via inhibiting DNA-dependent RNA polymerase |
| What is the specific target of Fluoroquinolones? | Inhibit DNA gyrase |
| What two classes of antibiotics function by inhibiting folic acid synthesis that is necessary for nucleic acids (aka antimetabolites)? | 1. Sulfonamides 2. Trimethoprim |
| What is the reasoning behind Sulfonamide's mechanism of action as an antimetabolite? | It is an analog of PABA, needed for folic acid synthesis |
| Are sulfonamides bacteriostatic or bactericidal? | Bacteriostatic |
| What is the reasoning behind trimethoprim's mechanism of action as an antimetabolite? | It is an analog of dihydrofolic acid, needed for folic acid synthesis |
| What are 2 genetic-based reasons for development of antibiotic resistance? | 1. Random mutations in DNA allow resistance development = Chromosomal resistance 2. Acquisition of chromosomal/extrachromosomal DNA by transferring plasmids/genes (R factors) |
| What is the reference designated for plasmids carrying antibiotic resistance genes? | R Factor |
| What are 4 specific mechanisms of antibiotic resistance used by bacteria? | 1. Bacteria alter the drug targets (Ribosomes, etc.) = drug can't bind 2. Bacteria alter their membrane permeability or transport drug out of cell 3. Bacteria synthesize enzymes that inactivate antibiotic 4. Bacteria alter their metabolic pathway |
| What are 3 examples of antibiotics that are ineffective due to bacterial alteration of the drug target? | 1. Erythromycin 2. Rifamycin 3. Streptomycin |
| What are 2 examples of antibiotics that are ineffective due to bacterial alteration of membrane permeability or increased drug transport? | 1. Erythromycin 2. Tetracycline |
| What are 2 examples of bacterial structures utilized in the Membrane Permeability Alteration/Drug Transport mechanisms of antibiotic resistance? | 1. Biofilm 2. Efflux pumps |
| What are 4 examples of antibiotics that are ineffective due to bacterial synthesis of enzymes to inactivate the antibiotic? | 1. Beta lactams (by beta lactamases) 2. Chloramphenicol 3. Aminoglycosides 4. Tetracycline |
| What are 2 examples of antibiotics that are ineffective due to bacterial alteration of metabolic pathways? | 1. Sulfonamides 2. Trimethoprim |
| What 3 bacterial species are resistant to all known antibiotics? | 1. Enterococcus faecalis 2. Mycobacterium tuberculosis 3. Pseudomonas aeruginosa |
| What 5 secondary factors are contributing to the development of antibiotic resistance? | 1. Antibiotic use in animals 2. Social factors (poverty, drug overuse, globalization = travel/trade) 3. Inappropriate antibiotic use by pt. 4. Disrupt normal flora 5. Lack of hygiene (hand washing, etc.) |
| What are the 2 fundamental characteristics of viruses? | 1. They are Obligate Intracellular Parasites 2. They are small |
| What is the difference between lytic viruses and non-lytic viruses? | Lytic viruses aim to replicate rapidly at the expense of the host cell while non-lytic viruses remain dormant in the host cell (= prophage), causing no harm to the host until environmental conditions induce lytic stage. |
| What are the 3 main types of infections? | 1. Latent 2. Chronic 3. Transforming |
| Describe the process of a latent viral infection. | Times of acute virus production, mixed with an almost total absence of viral particles. |
| What is an example of a virus that exhibits latent infection? | Herpes Simplex Virus |
| Describe the process of a chronic viral infection. | Non-lytic virus production; high number of viral particles is continually present |
| What is an example of a virus that exhibits chronic infection? | Hepatitis B |
| Describe the process of a transforming viral infection. | Host cells are transformed to suit the needs of virus. "Immortalized". |
| What is an example of a virus that exhibits a transforming infection? | Human Papilloma Virus |
| What are 8 common symptoms associated with gastroenteritis? | Nausea, WATERY diarrhea, vomiting, cramps, malaise, anorexia, myalgia, and headache |
| What is the main feature of gastroenteritis? | Acute, watery diarrhea |
| What are 6 high-risk populations for gastroenteritis? | Hospital wards, daycare centers, nursing homes, immunosuppressed individuals, travelers, military |
| What are the 2 diagnostic tests for gastroenteritis pathogens? | Enzyme immunoassay to detect antigens. *Rotavirus Latex agglutination screen |
| What is the treatment for gastroenteritis? | Replenish water, electrolytes, and sugar. |
| What is the source/epidemiology of Noroviruses? | Raw shellfish, fecally contaminated food = outbreaks |
| What is a preventative method used against Rotaviruses? | Vaccine- Rotateq, Rotarix |
| Is there a vaccine against Noroviruses? | No |
| What 2 viruses are a common cause of endemic severe diarrhea in infants? | Rotavirus, Adenovirus |
| What is interesting about the timing of Rotavirus outbreaks? | Pattern is predictable; outbreaks are common in winter |
| What formerly used Rotavirus vaccine was withdrawn from the US due to increased risk of intestinal intussusception? | Rotashield |
| What is the length of symptoms seen with Rotavirus infection? | 5-7 days |
| What is the length of symptoms seen with Adenovirus? | 5-12 days |
| What are a few potentially distinguishing features between Rotavirus and Adenovirus? | Adenovirus has no obvious seasonality, has an extended symptomatic phase, and is detectable by immunoassay. |
| What diarrhea/vomit-causing virus group is commonly associated with older children and adults? | Caliciviruses/Noroviruses |
| What is the innoculation method of Noroviruses? | Associated with food/shellfish |
| What is the length and severity of symptoms seen with Norovirus? | Mild, self-limited, 24-48 hours |
| How is Norovirus spread during outbreaks? | Person-to-person |
| What is the main feature/sign of cholera infection? | Acute, massive, watery diarrhea. "Rice water" stools |
| "Rice water" stools is a description of diarrhea commonly associated with what bacterial infection? | Vibrio cholerae |
| What are the most worrisome side effects associated with cholera infection? | Rapidly deplete fluids and electrolytes Hypovolemic shock/metabolic acidosis/death |
| Watery diarrhea, muscle cramps, poor skin turgor, wrinkly skin on fingers, sunken eyes, missing pulse in extremities are all symptoms commonly associated with what pathogen? | Vibrio cholerae |
| What is the gram type, shape, oxygen requirements, and mechanism of travel of Vibrio cholerae? | G-, bent rod shape, non-spore forming, facultative anaerobe, motile via polar flagellum |
| Which Cholerae serogroup (O antigen) is the cause of classic epidemic cholera? | O-1 |
| What is a newer Cholerae serogroup (O-antigen) that can cause cholera even after O-1 exposure? | O-139 |
| What is the treatment for cholera? | Replace fluids and electrolytes |
| What is the common method for spreading cholera infection? | Contaminated drinking water and food |
| What is the primary mechanism for cholera prevention? | Sewage control |
| What Vibrio species is a common cause of seasonal, food-borne illness in Japan? | Vibrio parahaemolyticus |
| What Vibrio species is commonly associated with oysters (via ingestion or wound contact) | Vibrio vulnificus |
| An alcoholic (patient debilitation) presents with bullous skin lesions, shock, and history of oyster consumption suspect of what causative organism? | Vibrio vulnificus sepsis |
| Describe the disease process of Enterotoxigenic E. Coli. (ETEC) | Adhere to mucosa of small intestine and release toxin (O antigen/LPS) = induce diarrhea |
| Traveler's diarrhea is commonly associated with what organism? | Enterotoxigenic E. Coli (ETEC) T is for Travel |
| Which E. coli organism is associated with bloody diarrhea? | Enterohemorrhagic E. coli (EHEC) |
| Hemolytic Uremic Syndrome is a potentially fatal result of infection by what organism? | Enterohemorrhagic E. coli (EHEC) |
| Which EHEC serotype cannot ferment sorbitol, and hence grows as while colonies on MacConkey's agar? | O157:H7 |
| What is the key virulence factor (toxin) of EHEC? | Shiga-like toxin |
| What infectious organism is associated with beef and raw milk? | EHEC O157:H7 |
| What newly recognized strain of Enteroaggregative E. coli expresses Shiga toxin and is associated with alfalfa sprouts? | O104:H4 |
| What is the gram type, shape, motility allowance, oxygen requirements, and growth temperature of Campylobacter jejuni? | G-, curved rod, motile, microaerophile, 42*C |
| A patient presents with a prodrome of fever, headache, malaise, and myalgia 12 hours before diarrhea ad RLQ abdominal pain. What is the suspected pathogen? | Campylobacter jejuni |
| What is the common reservoir of Campylobacter jejuni? | Intentinal tract of birds/poultry |
| What pathogen is known for transmission via undercooked chicken/poultry? | Campylobacter jejuni |
| Guillain-Barre is a complication commonly due to what pathogen? | Campylobacter jejuni |
| What is the treatment for Campylobacter jejuni infection? | None- it is self limiting |
| Chronic gastritis and peptic ulceration are consequences of infection by what organism? | Helicobacter pylori |
| What is the gram type, shape, and motility allowance of H. pylori? | G-, curved rod, highly motile |
| What organism stains well with Giemsa? | H. pylori |
| What human structure is the target of H. pylori | Epithelial cells |
| Cramps, halitosis, nausea, and vomiting are signs/symptoms of what infectious organism? | H. pylori |
| What is the virulence factor of H. pylori? | Urease |
| What are 3 diagnostic tests for H. pylori? | 1. Biopsy sample 2. Culture 3. CLO test to detect urease activity |
| What treatment is offered to treat H. pylori? | Tetracycline/antibiotics plus bismuth-containing drugs (Pepto-Bismol) |
| What are 3 preventative methods of GI infection? | 1. Control fecal excretion 2. Proper food handling/washing 3. Educate travelers on boiling/peeling/cooking water/food. |
| Initial symptoms of fever cramps, vomiting, and water diarrhea, followed by progression to dysentery: blood/mucous in stools, fever, and cramps is indicative of what pathogen? | Shigella |
| What is the gram type, oxygen requirements, motility of Shigella? | G-, facultative anaerobe, non-motile |
| What biotype result distinguishes Shigella from other E. coli? | Shigella is non-lactose fermenting |
| Bloody stool should cause suspect of which 2 organisms? | 1. EHEC 2. Shigella |
| What is the most effective treatment for Shigella? | Fluid replacement |
| What are 2 potential complications of Shigella? | 1. Reiter's syndrome 2. Hemolytic Uremic Syndrome (HUS) |
| Which two species of E. coli should antibiotics be contraindicated in, and why? | O157:H7 and Shigella. Both produce Shiga toxin, which is potentially deadly and may cause dysentery |
| Which two Shigella species are most common in the U.S.? | S. flexneri and S. sonnei |
| Describe the severity among Shigella serotypes A-D. | Group A (S. dysenteriae) is the most sever, group D (S. sonnei) is the least severe |
| What is the gram type, oxygen requirements, and motility in Salmonella? | G-, facultative anaerobe, motile |
| What diagnostic methods are used to identify Salmonella? | Presence of fecal leukocytes under microscope Culture feces/blood/water/food DOES NOT FERMENT LACTOSE |
| Which two bacterial species are known not to ferment lactose? | Shigella and Salmonella |
| What is the treatment for Salmonella infection? | Supportive- fluid and electrolyte maintenance |
| What are the primary reservoirs of Salmonella? | Animals: Eggs, beef, cattle, pigs/pork, dogs, cats, pet reptiles |
| What is a major difference between Salmonella and Shigella (Hint: dose) | Salmonella is a high dose microbe |
| What is an explanation for increasing Salmonella infection? | Animal handling: feeding slaughterhouse remains to chickens... infection spreads to eggs. Must change this process/consumer preferences |
| What is the causative organism of Pseudomembranous colitis? | Clostridium difficile |
| What is a reason for increasing cases of C. difficile infection? | Antibiotic use |
| What is the gram type, shape, oxygen requirements of C. difficile? | G+, rod-shaped, anaerobic **Forms spores |
| What are the diagnostic techniques used for Pseudomembranous colitis by C. difficile? | EIA and latex agglutination to detect toxin in feces Gram stain of stool Culture |
| What is the treatment for pseudomembranous colitis by C. difficile? | Fluid and electrolyte replacement, stop original antibiotic and start new one |
| What are preventative methods for C. difficile? | Wash hands, keep bathrooms clean, quickly identify and treat pts. |
| What is the gram type, motility, and dose and oxygen requirements of Clostridium perfringens? | G+, non-motile, high dose organism, aerotolerant anaerobe, ***Forms spores |
| What is the suspected causative organism that causes moderate-severe diarrhea with complete recovery in one day - FAST course of disease? | Clostridium perfringens |
| What is the method of transmission of C. perfringens, and why is it so worrisome? | Contaminated meat and poultry; Cooking meat does not destroy spores |
| What is the treatment for C. perfringens? | Supportive |
| What is the gram type, shape, oxygen requirements, motility, and spore status of Bacillus cereus? | G+, rod-shaped, aerobic, motile, **FORMS spores |
| What are the two possible clinical manifestations associated with B. cereus? | 1. Emetic form: preformed toxin causes upper GI symptoms: cramping, vomiting, diarrhea 2. Diarrheal form: vegetative cells ingested, will produce toxin: ab. pain, profuse watery diarrhea |
| What source is a common finding of B. cereus spores? | Rice. Also grains and vegetables |
| What is the treatment for B. cereus infection? | Relieve symptoms |
| What is a preventative method for B. cereus transmission? | Refrigerate grains quickly after cooking |
| What organism causes disease by consumption of heat stable, preformed toxins in food? | Staphylococcus |
| What is the suspected causative organism in a person with nausea, vomiting, diarrhea, cramps, and acute salivation 1-6 hours after eating? | Staphylococcus |
| What is the virulence factor of Staph? | Enterotixin A... water soluble, heat stable |
| A person who ate custard-filled baked goods, canned goods, processed meats, or potato salad is at risk for infection by what organism? | Staphylococcus |
| What is the treatment for GI infection of Staph? | Symptomatic- Fast course of disease |
| What are the three bacterial species that cause foodborne disease via toxin production? | Staphylococcus, B. cereus, C. perfringens = ANTIBIOTICS NOT USEFUL |
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mccullough87
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