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BIOM 250 Week 9

by: Davis Notetaker

BIOM 250 Week 9 BIOM 250

Davis Notetaker
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About this Document

These notes are on material covered in week 9: viruses, prions, host-microbe relationships and microbial control
Micro Hlth Sci: Infect Disease
Kari Cargill
Class Notes
Microbiology, virus, prion, microbe




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This 8 page Class Notes was uploaded by Davis Notetaker on Friday April 1, 2016. The Class Notes belongs to BIOM 250 at Montana State University taught by Kari Cargill in Winter 2016. Since its upload, it has received 16 views. For similar materials see Micro Hlth Sci: Infect Disease in Biology at Montana State University.


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Date Created: 04/01/16
Mon 3/28  Announcements:  Fri 4/01 No Class, Watch NARRATED LECTURE on D2L: Microbial Control Part 1  EC opportunity: +10 pts, Case Study  EC due Wed 4/20  Viruses  Viruses & Teratogenesis  TORCH series  ● Screening test during pregnancy (if a problem is suspected)  ● T​xoplasma,​ther transplacental infections(chicken pox, syph​ubella  , R virusCMV,​ ​V  ● Detects antibodies to teratogens  ● TORCH may also be used on newborns showing birth defects  Provirus  ● Viral DNA inserts into host cell DNA, then replicates along with host cell DNA  Ex: HIV  ● Fun fact:Some human DNA portions, historically called “junk DNA” due to unknown  purpose, are actually pieces of ancient viral DNA  Viruses & Cancer  ● ~10% cancers are virally induced  ● Oncogenic virus ­ has extremely high correlation to cancer  ○ Causes uncontrolled cell growth (tumor)  ● Ex: human papilloma viruses (HPV) ­> cervical cancer  Hepatitis B virus (HBV) ­> liver cancer    Genital HPV  ~30 types are primarily genital (~100 total)  75­80% sexually active people become exposed  Most asymptomatic    Ex:  Condyloma ­ genital warts  ● Have the most overt signs  ● Don’t cause cancer  ● Treated with physical methods of removal  ● Most clear over time without treatment    1%of HPV types become malignant  13 types cause 99% of cervical cancers  Also can cause penile and anal cancers  Recent: link to oral/throat cancers and HPV infections    HPV Vaccine  ● 3 doses  ● Recommended for females & males age 9­26 (most likely age group to develop   serious problems)  ● Ex: Gardasil vaccine for  ○ HPV types 16 & 18 (behind 70% of cervical cancers)  ○ 6&11 (cause 90% warts)  ● 30% of cervical cancers and 10% of genital warts not covered by vaccination  Prevention techniques still include safe sex practices, pap tests    Prions  Infectious proteins  ● Historically thought to be very small viruses, but no genetic material has   been detected  ● Not fully understood yet  ● “Misfolded” protein that causes healthy host proteins to fold into prion form    Neurological diseases: transmissible spongiform encephalopathies (TSE)  ● Microscopic holes in the brain, caused by misfolded brain proteins, are   characteristic of prion infections    Mode of transmission to humans:  ● Rare genetic disorder OR  ● Ingested prion (infected meat, animal to animal uncertain)    Symptoms  ● Wasting (emaciation), loss of coordination, psychiatric effects, dementia,   Death (invariably fatal after symptoms begin)  ● Seen in a variety of animals  Ex:  ● First seen animal prion infection: scrapie in sheep  ● Also, “mad cow’ in cattle  Technical name is BSE ­ bovine spongiform encephalopathy  ● Chronic wasting disease (CWD) in deer/elk     In humans  ● Creutzfeldt­Jakob disease (CJD) ­ genetic  ● Variant CJD (vCJD) ­ not genetic  ○ Increase of cases seen in Great Britain  ○ Eventually connected breakout to consumption of beef infected with “mad  cow disease”  ● First human form known: kuru  “Laughter disease”  Came from ritualistic cannibalism    General  ● Practices such as including dead animals in livestock feed lead to outbreaks  ● Prion proteins are very hard to destroy, can’t be killed by thoroughly cooking  meat  ● No treatment exists for the infection    Wed 3/30  Host­Microbe Relationships  Terminology  Contamination ­ means that microbes are present. Can refer to: inanimate objects, skin, etc.  Infection ­ multiplication of m/o’s in or on the body (overgrowth)  Disease ­ an infection that disrupts the normal body functions    Ex:  Needle becomes contaminated with HIV, new user becomes infected with contaminant,  infection leads to the disease    Normal flora  m/o’s that live in/on the human body, but don’t cause disease  In fact, these are generally beneficial via microbial antagonism  Microbial antagonism ­ outcompete potential pathogens  Pathogen ­ causes disease  Opportunist ­ normal flora that cause illness in a vulnerable host (e.g. immunocompromised,  presence of cut/lesion, etc)        Opportunistic Disease: UTI  disease/infection  Urinary Tract Infections (UTI)  etiologic agent  Escherichia coli­ 80% of cases  (caused by: name, type of m/o,  other characteristics)  reservoir (​where it is harbored  Natural human flora  naturally)  mode of transmission to  Fecal­oral route (contaminated food, water)  humans ​ (& susceptible  people)  pathogenesis ​ (progression of  Urine in bladder is normally sterile  disease within body, virulence  Urethritis ­ infections of urethra  factors)  Cystitis ­ bladder infection  Pyelonephritis ­ kidney infection (known by many other  names)  symptoms  pain/burning when urinating  More frequent urination  Kidney pain (you might feel this in your back or abdomen)\  treatment/prevention/control  Diagnosis:  Urine culture         Preliminary microscopic examination to identify the #         and type of m/o  Culture & identify m/o   Antibiotic susceptibility testing to determine which antibiotic  is most effective (exdisk diffusion tes)    Treatment  antibiotics    Disk diffusion test­ petri dish with urine sample is sprinkled with evenly distributed antibiotics  (different types). Lab clinicians can then visually determine which type is most effective and  inhibiting the microbial growth        Bacterial Virulence Factors   These are defensive and offensive advantages pathogens might have  Attachment  Via pili or capsule  Invasiveness  Enzymes that break down tissue  Ex: hyaluronidase ­ digests hyaluronic acid (which holds tissues together)  Tissue damage  Enzymes that damage cells  Examples:   ● coagulase ­ clots blood, then microbe can potentially “wall itself off” with  clots  ● Streptokinase ­ dissolves blood clots, which counteracts an immune   response to block off microbes with blood clots  ● Leukocidins ­ destroy WBC’s  ● Hemolysins ­ lyse RBC’s, hypothesized that this enables microbes to  extract iron from blood  Hemolysins are one way to study/identify m/o’s, in conjunction with usin​lood  Agar​:  ● Growth on Blood Agar (BA): agar plate to which blood is added (blood is  usually harvested from sheep)  ● Used to identify types of hemolysin and differentiate species ex:  streptococci  Blood Agar characterization (reactions in blood agar):  ● Alpha­hemolysis (α)   Partial lysis ­ can see a greenish zone   ● Beta­hemolysis (β)  Complete lysis ­ can see a clear zone where RBC’s have been destroyed  Gamma­hemolysis (γ)  No lysis ­ can see no zone      disease/infection  “Strep Throat” ­ streptococcal pharyngitis  etiologic agent  Streptococcal pyogenes  (caused by: name, type of m/o,  other characteristics)  reservoir ​where it is harbored  humans  naturally)  mode of transmission to  Rheumatic fever:  humans ​ (& susceptible  Fever,rash, arthritis  people)  pathogenesis ​ (progression of  Complications (occur w/o treatment)  disease within body, virulence  ~3% of cases progress to rheumatic fever  factors)  Autoimmune reaction  Can lead to damage to heart valve     Prophylactic antibiotics administered before dental work      for susceptible people with heart valve damage  symptoms  Very sore throat, especially swallowing  fever  treatment/prevention/control  Diagnosis  Traditionally: throat swab plated on BA  Incubated overnight, then see beta­homolysis  Rapid test: throat swab ­ detects strep antigens (molecules)  + Indicates strep  ­ Indicates there should be a follow up with BA, to test  for a false negative  Treatment: antibiotics (mostly penicillins)      Fri 4/01 Video lecture on D2L  Microbial Control  Sterilization and Disinfection  Sterilization ­ destruction oal microbes (e.g., endospores, but not prions (must be incinerated))  Disinfection ­ treatment of inanimate items, usually destroys vegetative cells (not endospores)  Antiseptic ­ treatment for external,living tissue  Antibiotic ­ kills bacteria, used internally and topically  Sanitization ­ lowers microbial presence to safe public health levels    Physical Methods  The following physical methods can be used to effectively control m/o growth:  ● Heat (e.g. dry heat, boiling, autoclaving)  ● Filtration (very fine filters)  ● Cold (slow down growth but not necessarily destroy m/o’s)  ● Desiccation (drying)  ● Radiation   Note: Autoclaving, filtration, and gamma ray radiation may achieve sterility    Chemical Methods  The following list describes the m/o’s resistance to chemicals, with the most resistant at the top  and least resistant at the bottom:  1. Prions  2. Bacterial endospores  3. Cysts of protozoa  4. Gram­negative bacteria  5. Fungi, including most fungal spore forms  6. Naked viruses (have no envelope)  7. Gram­positive bacteria  8. Viruses with lipid envelopes   Know the top 3 & bottom 3 for exam      Antimicrobial Therapy (Medication)  Chemotherapeutic Agents  Antibiotic ­ chemical produced by m/o’s that inhibits other m/o’s (naturally occurring chemical   that is harvested and used for medication)  Synthetic drugs ­ chemical compounds produced in a lab    A good antibiotic is selectively toxic ­ it harm’s m/o infection without causing too much harm to  the host    Antibiotics have varying spectrums of efficacy:  ● Broad spectrum ­ antibiotics that are effective against a wide range of bacteria, but may   also be detrimental to host’s friendly bacteria  ● Narrow spectrum ­ antibiotics only effective against specific bacteria     Mode of Action   Mode of action ­ the different mechanisms with which chemicals kill/inhibit m/o’s  ● Damage to cell wall/inhibition of cell wall synthesis  ● Disruption of cell membrane function  ● Inhibit protein synthesis  ● Inhibition of nucleic acid synthesis ­ i.e. impede m/o ability to produce genetic material  ● Act as an antimetabolite ­ e.g. molecular mimicry, where antibiotic mimics a substance  essential for m/o process but does not provide the same functionality    Drug Resistance  Methods that microbes have to counter drug medications:  ● Destruction of the drug, after it has breached the cell wall  ● Adaptation of cell wall so drug is no longer able to penetrate  ● Mechanisms that eject the infiltrated drug  ● Adapt the component being targeted by the drug    How m/o’s develop drug resistance  ● Mutation  ● Acquire new gene from an R plasmid of another bacterium    Antibiotic Misuse  Multiple­drug resistant (MDR) bacteria numbers are increasing, in part due to antibiotic misuse:  ● Used to treat viral infection  ● Use without prescription  ● Use without completing use outlined in prescription  ● Use of someone else’s  leftover meds   ● Overuse, in livestock feedlots  ○ Can lead to runoff (gets into water)  ○ EU has banned this manner of usage    Superinfection ­ resulting from antibiotic overuse, this kind of infection occurs when antibiotics  destroy normal flora, enabling pathogens to flourish 


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