Notes - Bacterial Diseases.docx

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Department
Microbiology
Course
MICB 202
Professor
Tracy Kion
Semester
Winter

Description
Bacterial Diseases 6 Case Studies: To Go Pick Chilled Strawberries and Bananas. 1. Tuberculosis 2. Gonorrhea - MAIA 3. Pneumonia - ALPhA 4. Cholera - TFT 5. Salmonella - LACTIc 6. Bordetella – PALATe  symbiosis – cohabitation  ex: body and normal flora  mutualism – body and normal flora benefit from symbiosis  commensalism – symbiotic relationship beneficial only to normal flora  commensal – bacteria of normal flora Host and Normal Flora Relationship Outcomes - PlaCID  Pass through body harmlessly  Colonize body and establish as normal flora  establish infection in body  establish infection in body and cause disease  infection – invasion of the body with a pathogenic microorganism  disease – damage done to the body impairing function  strain – bacteria colony descending from one cell Host and Microorganism Relationship Influences  pathogenicity of microorganism – ability of pathogen to cause disease  resistance/susceptibility of host – adaptive and innate immune responses 1. Pathogenicity  qualitative  genetic component  normal flora and opportunistic pathogens lack inherent ability to cause disease  pathogen – capable of causing harm to normal host  opportunistic pathogen – capable of causing harm to compromised host 2. Virulence  quantitative  virulence – measure of pathogenicity - # of cells needed to induce a pathogenic response within a certain period of time  property of organism that determines extent of disease  correlated w/ ability of pathogen to multiply within host  affected by factors  route of entry  general health/susceptibility of host 3. Infection Classifications  primary – initial, acute infection  secondary – opportunistic infection  subclinical – no apparent symptoms  nosocomial – consequence of hospitalization  invasiveness – ability to invade beyond original point of entry  local – restricted to relatively small area  non-invasive organism  systemic/general – spread throughout the body  invasive organism  focal – originating in restricted area and spreads throughout the body 4. Host Susceptibility – PAUSInG  poor nutrition  age  underlying conditions  stress  immunosuppressant therapy  genetics  normal flora – same bacterial species colonizing same anatomical sites in all people Host and Normal Flora Mutualistic Relationship 1. Normal Flora Benefit  stable environment  source of nutrients  mode of transport 2. Host Benefit  microbial antagonism  takes up space  uses nutrients  produces inhibitory by-products  affects conditions: pH and O2  nutritional synergism  synthesis/excretion of excess vitamins  steroid metabolism  organic acid production  glycosidase reactions  stimulate immune system  induce antibody response  antibody response cross react to related to pathogens instead of flora 3. normal flora microorganisms adapted to host  physical association  bacterial surface compounds – ligands or adhesins  host cell – molecular structures 4. Normal Flora Harmful  pathogenic potential  normal flora introduced to other locations  production of intestinal gas  large intestine food fermentation  CO ,2H ,2NH ,3and H S2 Normal Flora Chronology and Source 1. passage through birth canal 2. exposure to humans/pets 3. inhalation/ingestion Normal Flora Composition Factors  diet  infection – temporary increase in pathogen  oral antibiotic therapy – temporary decrease in normal GI tract flora Normal Flora Location  location – hospitable vs inhospitable – found in 1 location and never another  essential growth factor vs stomach acids, bile salts, and lysozyme  location – binding sites – specific bacterial ligands vs host receptor locations  capsules, cell wall, fimbria vs specific host locations  biofilms – mixture of microorganisms  tissue surface, implants, or other biofilms Vaccines  prevent disease but not infection  administered before or after exposure  administered before onset of disease  active immunization – injecting vaccine to induce specific immune response  whole society or population  passive immunization – injecting pre-formed antibodies against specific bacteria  infected individual Materials in Vaccines - TAKO  toxoids  avirulent mutants  killed virulent bacteria  outermost components Case Study: Mycobacterium tuberculosis Tuberculosis  infection of lungs  inflammatory reaction → phagocytic cells  bacteria survive/multiply in macrophages → further spread  survive in dormant state → reactivation  person to person  Prevalence  highest number of deaths attributed to single infectious agent  Treatment  ~9-12 month treatment w/ multiple antibiotics  Vaccination  Mycobacterium bovis BCG  cell mediated immune response Isolation and Identification  isolate and identify causative agent of infectious disease within 48 hours o minimize severity and duration of disease o identify most suitable antibiotic for treatment o identify causative agent of disease outbreak in hospital setting 1. Microscopy 2. Growth-Dependent Identification Methods  general purpose media  blood  supports most aerobic and facultative anaerobic bacteria  enriched media  specific growth factors  supports metabolically fastidious bacteria  selective media  inhibits some bacteria growth but not others  differential media  identification of bacteria through appearance 3. Testing Antibiotic Sensitivity a. zone of inhibition  diffusion rate of antibiotic  degree of sensitivity of microorganism  growth rate of bacteria  sensitive – equal to or greater than standard  resistant – less than standard b. Growth-Independent Identification Methods  detection of bacteria w/o culture is possible  directly detect pathogen presence  detect antibody presence Epidemiology and Disease Spread  epidemiology – study of when, where, and how diseases occur/spread  incidence of disease – fraction of population that contracts disease during period of time  prevalence of disease – fraction of population having symptoms during a period of time  newly acquired and established cases Frequency  sporadic – occasional, may not be related  endemic – continually at relatively low level  disease may not be very virulent  individuals may be immune to pathogen  epidemic – sporadically at elevated level, continuously at low level between outbreaks  pandemic – widely distributed epidemic  disease outbreak – number of disease cases increases in area which previously experience only sporadic cases Disease Transmission  Human Reservoirs  symptomatic – has disease  convalescent – recovering from disease, still harbors infectious agent  carrier – no symptoms of disease, but carries pathogen  acute – transient  chronic – may have recovered from clinical disease, still carry  Animal Reservoirs  zoonoses – disease transferred from animals to humans  Insect Reservoirs  Inanimate Reservoirs – soil and water Mode of Transportation  vector – bug bites  contact – person to person  common vehicle – inanimate objects, food, water, blood, drugs  airborne – droplets or dust Virulence  infectious dose (ID) - # of bacteria required to cause disease  lethal dose (LD) - # of bacteria required to kill  # of bacteria required to kill 50% of population Nosocomial Infections  patients are reservoirs  exposure to pathogens  weakened immune system  contact transmission  endogenous – caused by normal flora  exogenous – transmitted from another person  iatrogenic – doctor induced  surgery, invasive procedures, implants  cardiovascular, cutaneous, respiratory, or urinary infections Case Study: Neisseria gonorrhoeae Gonorrhea  non-motile/non-sporing  Gram-negative  direct contact  virulence factors - MAIA  resistance to MAC attacks  adhesins  iron acquesitions  antigenic variation  STD = human pathogen; does NOT cause disease in animals  asymptomatic carriers – major factor in disease spread Symptoms  men – OFTEN asymptomatic  1-14 days after infection  urethritis – inflammation of the urethra  painful urination  urethral discharge of pus  women - OFTEN asymptomatic  7-21 days after infection  endocervix infection – mucous membrane lining cervical canal  cervical-vaginal discharge, painful urination, abnormal menstrual bleeding, pelvic pain  pelvic inflammatory disease (PID) – cause of sterility in women  transmit bacteria into eyes of infants during birth – opthalmia neonatorum Recovery  fast w/ antibiotics  self-limiting infection – person recovers on own Diagnosis  microscopy – test for urethral or cervical discharge of Gram-negative diplococcic  not typically part of genitourinary tract normal flora  male patients  culture – standard biochemical test (sugar fermentation), oxidase enzyme presence, and cell/colony morphologies  female patients – positive culture result, negative cervical Gram-stain result  DNA – bacterial genes from urine sample or cervical swab Case Study: Streptococcus pneumonia Pneumonia  non-motile/non-sporulating  Gram-positive  cocci: singly, pairs, or short chains  transient member of nasopharynx normal flora  opportunistic pathogen  young and elderly at risk  alcohol and smoking increase risk  direct contact via respiratory droplets  encapsulated organisms pathogenic for humans and animals  virulence factors – ALPhA  anti-phagocytic polysaccharide capsule  LTA – lipoteichoic acid  pneumolysin – toxin binds to cholesterol in host membrane & prevents pore formation  adhesins Symptoms  pneumonia – inflammation of the lungs  bacteremia – bacteria in blood  meningitis – inflammation of membranes surrounding brain and spinal column  otitis media – ear infection Two Forms 1. bronchial pneumonia  infants, young children, and aged adults  alveoli contiguous to larger bronchioles 2. lobar pneumonia  young adults  single lobe of lungs Diagnosis  sputum, blood, or cerebrospinal fluid sample  Gram-positive staining, hemolytic activity, and bile sensitivity  aerobic conditions – alpha hemolysis  anaerobic conditions – beta hemolysis Case Study: Vibrio cholera Cholera  motile  Gram-negative  enterotoxin – type of exotoxin – affect cells lining GI tract causing fluid secretion  exotoxin – secreted proteins made by Gram-positive and Gram-negative bacteria  toxins enter blood circulation and damage far from entry site  3 main categories – NECk  neurotoxin
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