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93 Cards in this Set
- Front
- Back
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What were some of the major discoveries/insights in medical microbiology?
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invention of microscope, smallpox vaccine discovery, development of the germ theory, connection between hand washing and disease prevention, discovery of penicillin
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Over what time period did the major discoveries in medical microbiology occur?
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microscope discovered in mid-1600's, mid- to late 1800's was the boom of information, some important discoveries made in early 1900's
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What are Koch's (classical) postulates?
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-The microorganism should be in all cases of suffering animals but not in healthy animals
-It should be isolated from the sick and grown in pure culture -When innoculated into a healthy animal it should cause the same disease -It should be re-isolated in pure culture from this experimental animal |
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What are Koch's (molecular) postulates?
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-The phenotype in question is associated with the pathogenic members of a genus/strain of a species
-Inactivation of suspect virulence gene(s) should decrease pathogenicity -Reversion or allelic replacement should restore pathogenicity |
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What are the major differences between prokaryotes and eukaryotes that can be exploited to combat disease?
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-lack of cell wall in eukaryotes
-prokaryotic chromosome is circular -lack of membrane bound organelles in prokaryotes -reproduction by binary fission in prokaryotes |
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gram positive envelop structure
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capsule-->thick peptidoglycan layer-->plasma membrane
-peptidoglycan layer connected by pentaglycine bridge -teichoic acids protruding from peptidoglycan |
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gram negative envelop structure
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capsule-->outer membrane with LPS on outer leaf-->thin peptidoglycan layer in periplasmic space-->inner membrane
-contains porins |
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What is peptidoglycan?
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A component of the cell wall made of peptide and carbohydrate. Prevents osmotic rupture of the cell. Thick in gram +, thin in gram -
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3 compartments of cell wall synthesis
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-Cytoplasm: basic peptide formation
-Inner membrane: carbohydrate residue added -Periplasmic space/outside cell: subunit produced is added to existing cell wall components |
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what general group of bacteria produce endotoxin (lipid A)?
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Gram negative. Endotoxin is a component of LPS
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What is the toxic component of endotoxin?
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Fatty acid residue in the lipid A structure
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What are the physiological effects of endotoxin on the host?
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Septic shock (release of CKs when large numbers of bacteria are lysed) due to imbalance of pro- and anti-inflammatory mediators
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What is the function of A and G proteins?
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These proteins provide a form of host mimicry by causing immunoglobulins to bind "backward" on the bacterial cell (Fc portion binds instead of Fab)
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What are A/B toxins?
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2 subunit toxins
examples: Shigella toxin, E. coli heat labile toxin |
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Which component of A/B toxins confers the toxicity?
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A is the toxic component
B is the binding component |
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What is the purpose of a siderophore?
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Iron acquisition
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define normal flora
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the microorganisms present on or in a host that do not produce a pathology
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pathogenicity
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The ability of a microorganism to cause disease in a host. Qualitative description
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virulence
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The strength of a microorganisms ability to cause disease in a host. Quantitative descritpion
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What is the framework for describing host-microbe interactions?
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Encounter, Entry, Spread, Multiplication, Damage, Outcome
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What are the 3 possible outcomes of a host-microbe interaction?
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host wins--microbe is removed
microbe wins--host is killed co-existence--neither host nor microbe is harmed |
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infection
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establishment of a host-pathogen interaction
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disease
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an alteration of body organs to the point that normal body functions are disturbed
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plasmid
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extrachromosomal DNA fragments in circular form only found in bacteria
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Which is better at separating particles based on size during electrophoresis: agarose gel or polyacrylamide gel?
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Polyacrylamide gel. It has smaller spaces between molecules, so it better separates particles
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Real time PCR
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quantitative study of how much of a product is replicated over time
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restriction fragment length polymorphism (RFLP)
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Use of restriction enzymes to fragment DNA before gel electrophoresis
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Pulsed field gel electrophoresis (PFGE)
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use of alternating current during electrophoresis to separate large fragments from small
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Polymerase Chain Reaction
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method for amplification of DNA
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Random amplified polymorphic DNA (RAPD)
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short random primers used in PCR. useful for comparisons between isolates
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Amplified fragment length polymorphism (AFLP)
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short random PCR primers are used in conjunction with restriction enzymes. Useful for comparisons between isolates
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ribotyping
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use of 16s rRNA and Southern blot to determine differences/similarities between isolates
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What are the physical methods used to control microbial growth?
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heat
radiation filtration |
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What is the mechanism of heat on control of microbial growth?
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denaturation of proteins
collapse membranes create ssDNA breaks |
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Why is moist heat more effective than dry heat?
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Moist heat can reach higher temperatures than dry heat based on the ability to increase pressure:
PV = nRT |
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What makes pasteurization different from other forms of heat sterilization?
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low temperatures over a long period of time kill bacteria without denaturing too many proteins--flavor is preserved
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What forces/phenomena allow for the success of filtration in removing microbes?
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Van der Waals
random entrapment in pores adhesion to previously trapped items |
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Name 2 types of radiation
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UV (sunlight)
ionizing |
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what is the mechanism of UV disinfection?
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UV excitation of DNA causes pyrimidine molecules to bind together thus changing shape of the molecule which will inhibit DNA replication
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what is the mechanism of ionizing radiation?
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ionization of water molecules permanently removes an electron thus creating a free radical
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what mechanisms are used in chemical methods of control of microbial growth?
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damage to membranes,
modification of protein and nucleic acid functional groups |
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Which chemical agents control growth by causing damage to cell membranes?
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surface-acting disinfectants (quaternary ammonia compounds), alcohols, phenolic compounds (hexachloropene)
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Which chemical agents control growth by modifying proteins and nucleic acid functional groups?
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oxidative agents (halogens, H2O2)
alkylating agents (aldehydes, ethylene oxide) |
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sterilization
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inactivation of organism's ability to reproduce
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disinfection
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removing the heath hazard of pathogenic organisms
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bacteriacidal
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killing of bacteria
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bacteriastatic
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bacteria are inhibited from growth or prevented from multiplying. organisms are not killed
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how does an animal host encounter Pasteurella or Mannhiemia?
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these are commensal bacteria that becomes pathogenic when host is immunocompromised. Animal-to-animal transfer is possible. Mannhiemia may be aspirated into the lungs.
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Diseases caused by P. multocida
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-Atrophic rhinitis in swine
-fowl cholera -ruminant hemorrhagic septicemia -bite wound abcess |
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Which bacterial species are required for creating an atrophic rhinitis in swine?
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Pasteurella multocida AND Bordetella bronchiseptica. Both are required
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what are the possible virulence factors of P. multocida in atrophic rhinitis?
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PMT (P.mult toxin)
colonization of upper respiratory tract capsular serotypes iron uptake mechanisms |
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What is the main disease caused by Mannheimia haemolytica?
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Bovine pneumonic pastuerellosis (Shipping Fever)
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Which M. haemolytica serotypes are responsible for disease in cattle? in sheep?
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A1: Cattle
A2: sheep |
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What are the possible virulence factors of M. haemolytica?
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Leukotoxin
Capsular serotype colonization degradative enzymes |
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E. coli identification (i.e. simple tests used and results)
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Gram - rod
catalase + oxidase - lactose utilization is variable |
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serogroup
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broad groups that describe the antigenicity of LPS type (O group), capsule type (K), flagella type (H), and fimbriae type (F)
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serotype
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specific combination of serogroup factors to describe the specific antigenicity of a bacterial strain
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ETEC (enterotoxigenic)
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very important in vet med
affects many species Hypersecretory diarrhea |
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AEEC (adhesion-effacing)
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affects swine and cattle
malabsorptive diarrhea |
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EHEC (enterohemorrhagic)
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most important in human med
affects cattle, humans malabsorptive diarrhea |
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EPEC (enteropathogenic)
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affects swine
malabsorptive diarrhea |
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APEC (avianpathogenic)
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affects birds
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EAggEC (entero aggregative)
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affects swine
malabsorptive diarrhea |
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CTEC (cytotoxic)
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affects puppies and kittens
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EIEC (enteroinvasive)
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invades M-cells in gut then migrates into enterocytes
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What is ADP-ribosylation?
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The method used by ETEC (to create pores in the membrane of enterocytes) and Bordetella. Production of enterotoxin interrupts G-protein control of adenylyl-cylase to increase cAMP
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pathotype
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the virulence profile of a bacteria based on how the bacteria produces disease in a specific host
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autogenous bacterin
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the exact bacteria producing a disease are used to prevent infection of others in that immediate environment (i.e. outbreak on farm, bacteria from that farm are used to prevent further illnesses)
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Type III Signal System (TTSS)
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initiation of a signal cascade following binding of bacteria by intimin. Creates cups and pedistals on host cell to facilitate endocytosis. Used by AEEC. No toxins produced. Used to transfer effector proteins into host cells to alter cell function
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How is tetrathionate broth (TTB) an enrichment medium?
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Iodine in the broth inhibits the growth (but does not kill) of many bacteria but not Salmonella. Sulfathiazole supresses growth of Proteus.
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How is blood agar a differential medium?
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Red blood cells in the agar allow for recognition of hemolytic activity of bacterial colonies.
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How is MacConkey agar a selective medium?
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Crystal violet and bile salts in the agar prevent the growth of gram + bacteria
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How is MacConkey agar a differential medium?
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lactose and neutral red pH indicator. If a bacterium can ferment agar, it will produce lactic acid thus changing the pH indicator creating a purple/pink colony
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How is Brilliant Green agar a selective medium?
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brilliant green dye in the agar prevents the growth of gram + and most gram - bacteria
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which gram negative bacterial growth is not inhibited on BG agar?
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Salmonella
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How is brilliant green agar a differential medium?
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lactose, sucrose and phenol red pH indicator. If a bacterium can ferment lactose and sucrose, it will appear yellow-green. If a bacterium cannot ferment the sugars, it will be white with a pinkish color in the medium surrounding it.
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What is phase variation?
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A method used by Salmonella to evade host defenses. Involves the switching of gene transcription between flagella types
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pathogenicity island
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a group of genes that confer an advantage on a bacterium. often the genes are for virulence factors, antibiotic resistance, iron uptake, adhesins
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horizontal gene transfer
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addition of genetic material to a bacterial genome from one bacterium to another that is not the offspring of the first
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What is the mechanism of entry of Salmonella?
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fecal-oral
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Describe the pathogenesis of Salmonella-induced diarrhea
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Bacteria recognizes M-cells with its attachment pili-->invasin genes activated, fimbriae produced-->host cell endocytosis-->down regulation of invasin and fimbriae-->invasion of neighboring enterocytes-->host response leads to destruction of infected cells-->malabsorptive diarrhea
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What types of diseases are caused by Yersinia species?
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Y. enterocolitica: food borne gastroenteritis
Y. pseudotuberculosis: infection of mesenteric lymph nodes, ileitis, septic infections (in birds, rabbits, rodents) Y. pestis: black plague |
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What types of diseases are caused by Shigella species?
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enteritis in primates
S. dysenteriae: most severe enteritis that can progress to hemolytic uremic syndrome (HUS) |
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What does extraintestinal mean?
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Space outside of the gastrointestinal tract
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ExPEC
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Extraintestinal Pathogenic E. coli
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Which extraintestinal infections does E. coli not cause?
a) bovine coliform mastitis b) avian airsacculitis c)meningitis d) UTI in humans and pets e) none of the above |
e) none of the above
ExPEC can cause all the listed diseases |
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Which extraintestinal infections does E. coli not cause?
a) gram negative endotoxemia b) umbilical infection c) yolk sac infection d) pneumonia |
d) pneumonia is listed as a disease caused by extraintestinal Klebsiella pneumoniae
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True or false: ExPEC has been known to cause bovine endometritis.
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True
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Which virulence factor does Klebsiella use to cause disease?
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Capsule antigens (K)
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Match disease to serotype (use K1 or K2) for Klebsiella infections:
sterility in horses UTI meningitis in foals |
sterility in horses: K1
UTI: K2 meningitis in foals: K1 |
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Which motile bacteria swarms on the surface of agar?
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Proteus
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With which diseases has Proteus been associated?
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UTI, pneumonia, septicemia, burn wounds, otitis externa and interna, dermatitis
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What are the genera that fall into the Enterobacteriaceae category?
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Escherichia, Salmonella, Klebsiella, Yersinia, Serratia, Proteus, Citrobacter, Enterobacter, Morganella
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