Chapter 14 Principles of Disease PDF

Chapter 14 Principles of Disease  Principles of Disease Pathology: study of disease – Pathogen: disease-causing micro-organism – Etiology: cause of disease – Pathogenesis: manner in which a disease develops – Structural and functional changes Infection: invasion of the body by...

Chapter 14 Principles of Disease  Principles of Disease Pathology: study of disease – Pathogen: disease-causing micro-organism – Etiology: cause of disease – Pathogenesis: manner in which a disease develops – Structural and functional changes Infection: invasion of the body by a pathogen Disease: results in change from a state of health Not all microbes cause disease!!  Normal Microbiota At birth: lactobacilli in intestine E. coli acquired from food (reside in intestine) 1013 cells AND 1014 bacteria! (1013 human cells) Human Microbiome Project Table 14.1 for a list (pg. 392) – ON YOUR OWN: for each body region, know the “Comments” section of the table Transient microbiota: here and then gone  Factors that Affect Your Normal Microbiota Nutrients (carbon source) Physical Factors (temp, O2) Chemical factors (salinity, pH) Host defenses (immune reactions) Mechanical factors (chewing, mucous) Can’t We All Just Get Along? How do organisms get along with their host? What benefit do they provide?  Our Welcomed Guests!! Skin Tongue Esophagus Can’t We All Just Get Along? How do organisms get along with their host? – Prevent overgrowth of harmful microbes (microbial antagonism) (Ex. C. ablicans, oral strep) – Bacteriocins: proteins produced by some bacteria that inhibit the growth of other bacteria – Clostridium difficile – gastrointestinal infections What benefit do they provide? Symbiosis – Commensalism – Mutualism (probiotics?) Find 2 primary literature articles and give a brief overview of the results (1-2 sentences) One supporting the use and one showing other results  Opportunistic Organisms When a normal flora gains access to alternative regions of the body Common features 1. Present in large numbers 2. Found in places of the body that are protected from the host defenses 3. Resistance to antibiotics (ex?) Normal symbiotic pathogens – Echoviruses (stands for…) – Neisseria meningitidis – Streptococcus pneumoniae – Others? Come up with a list….  Etiology of Disease Koch’s postulates: Restate again!!! Etiology of Disease Koch’s postulates: Same pathogen in every case Pathogen must be isolated and cultured Pathogen from culture must cause disease Pathogen must be isolated again and shown to be identical to the original Fig. 14.3  Exceptions to the Rule 1. Unique culture requirements (M. leprae, T. pallidum) 2. Not all signs and symptoms are caused by one single pathogen (ex. nephritis, pneumonia, meningitis, peritonitis) 3. Pathogens can cause several disease conditions 4. Ethical considerations concerning intentional inoculation (HIV) Classifying Infectious Diseases 1. Pathogenesis 2. Occurrence 3. Severity or duration 4. Extent of host involvement  1. Pathogenesis Evidence: – Symptoms: subjective, not apparent (pain) – Signs: objective, measurable (temperature) – Syndrome: specific sign/symptoms characteristic of a particular disease Behavior in a host: – Communicable disease – host to host Contagious: easily spread – Noncommunicable disease – organism resides outside the body  2. Occurrence of Diseases Fig. 14.4 Occurrence: – Incidence - # of people in a population who develop a disease during a particular time period (new cases) – Prevalence - # of people in a population who develop a disease at a specified time, regardless of when it first appeared (all cases) – EXAMPLE: AIDS in 2012 – incidence=55,400; prevalence=117,000 Frequency of Occurrence of a Disease  Sporadic – occasional  Endemic – constant holoendemic  Epidemic – lots in a little time  Pandemic – world-wide epidemic  Occurrence of Disease *Move the cursor over the image, and click on the Play arrow on the bottom left.*  3. Severity of Diseases Acute – rapid but gone quickly Chronic – slow, less severe, longer Subacute – sort of both Latent – inactive, and then “bang” All determined by the host’s immune system – Can boost immunity by immunizations – Herd immunity  4. Host Involvement in Disease Local – small area of the body Systemic – through the body (get in your internal organs) Focal – start at one place, travel and stay put Bacteremia vs. septicemia? Know these Toxemia vs. viremia? on your own… Primary vs. secondary infection? Subclinical/asymptomatic  Patterns of Disease Sequence of events 1. Source of pathogen 2. Pathogen gets to host 3. Invasion in host and pathogen multiplies 4. Injury to host (pathogenesis) Predisposing factors: makes body susceptible to infection – Gender and age - Nutrition – Genetic background - Lifestyle – Climate/weather - Occupation – Medical illness - Chemotherapy  Development of Disease 1. Incubation period – infection to signs 2. Prodromal period – mild symptoms 3. Period of illness – immune system will generally overcome the pathogen 4. Period of decline – still vulnerable to 2o 5. Period of convalescence – regain strength Fig. 14.5 A person can serve as a reservoir during illness, as well as incubation+ convalescence!  Reservoirs of Infection Source of disease-causing microbe – Living or nonliving Different reservoirs: – Human (carriers) – Animal (zoonoses; Table 14.2) – Nonliving WATER (fecal contamination) SOIL (animal feces) FOOD  Transmission of Disease Contact transmission – Direct contact (person to person) - touch, kiss, sex (wear gloves) – Indirect contact (nonliving object= fomite) – tissue, syringe, money, bedding, door knob,etc. – Droplet transmission (mucus droplets; travel short distance) – cough, sneeze, laugh Vehicle transmission – water, food, air by dust Vectors – animals that carry microbe from one host to another (arthropods; Table 4.3) – Mechanical transmission: passive transport – Biological transmission: active transport  Healthcare-Associated Infections (HAI) Nosocomial Infection acquired in the hospital, nursing home or health care facility 5-15% of all patients 2 mill/year; 20K die!!! How do you get one? – Microbes in the hospital – Compromised host – Chain of transmission Fig. 14.9 (host, fomite, etc.)  Microbes in the Hospital Categories of organisms in a hospital: – Opportunistic pathogens – Antibiotic resistant pathogens (R factor) Organisms responsible: Table 14.4 – S. aureus - Enterococcus spp. – E. coli - MRSA – P. aeruginosa - C. difficile**  Compromised Host Resistance to infection is impaired by disease, therapy or burns. Table 14.5 for body sites of HAIs – on your own Broken skin – Burns - Ventilator – Surgical wounds - IV therapy – Injections - Catheters – Invasive procedures Suppressed immune system – T-cells – kill pathogens directly – B-cells (antibodies)  Chain of Transmission Direct? Indirect?  Control of Healthcare Associated Infections Reduce the number of pathogens HOW? – Handwashing – Wash tubs used to bathe patients – Clean respirators/humidifiers – Single-use bandages – Controlled use of antibiotics – Use invasive procedures last – Lower use of immunosuppressive drugs  Epidemiology Studies when, where and how a disease occurred 3 important people: know them on your own (pg. 408) – John Snow – Ignaz Semmelweis – Florence Nightingale  What does an epidemiologist do? 1. Determines the etiology of a disease 2. Identifies other possibly important factors and patterns concerning the affected patients (age, sex, habits, other diseases, etc.) 3. Identifiy methods of controlling disease Several stragegies: chemotherapy, vaccines, control of reservoirs, proper food storage, etc. 4. Provide physician with info to determine prognosis/treatment of disease 5. Evaluate effectiveness of control mechanisms in a community 6. Provide data to help plan health care for a community Example of Data  Covid Tracking https://covid19.ncdhhs.gov/dashboard/cases  Types of Investigations Descriptive – collecting all data that describe the occurrence of the disease; backtracking (retrospective) Analytical – analyzes a disease to determine the cause – Case-control method: factors that precede the disease (compare 2 groups) – Cohort method: 2 populations, one that has contact with organism Experimental – hypothesis and test  Case Reporting Health care workers report a specific list of disease states (Nationally Notifiable Diseases - Table 14.6) Large population infected with disease, may tend to isolate and ID the microbe by biochemical testing Determine chain of transmission Apply control measures: – Elimination of source - Vaccines – Isolation of individ. - Education Table 14.6 Nationally Notifiable Infectious Diseases  Case Reporting Health care workers report a specific list of disease states (Table 14.6) Large population infected with disease, may tend to isolate and ID the microbe by biochemical testing – Isolation vs Quarantine Determine chain of transmission Apply control measures: – Elimination of source - Vaccines – Isolation of individ. - Education  Centers for Disease Control and Prevention (CDC) Central source for epidemiological information in US Weekly report of morbidity (incidence of specific disease) and mortality (number of deaths) (MMWR, www.cdc.gov) – https://www.cdc.gov/mmwr/index.html Notifiable Diseases (Table 14.6)  Emerging Infectious Diseases (EID; BIO/GBS 3350) New or changing diseases caused by microbes (any or all!) Identify EID: – Symptoms that are distinct – Improved diagnostic tests – Change in pattern of the disease Seven (7) factors that contribute to the emergence of EID (pg 413) Plans by CDC and WHO Emerging Infectious Diseases Journal