Principles of Disease and Epidemiology

1. Principles of Disease and Epidemiology Ch 14

2. Diseases and US • Pathogen : a disease causing microbial growth or toxin. • Disease: an abnormality in which the body or part is not properly adjusted. The body part is overcome by the microbe • Change in the state of health • Infection: is the invasion and growth of a pathogen in the body

3. More words • Host: Is an organism that shelters and supports the growth of pathogens. • Pathology: scientific study of disease • Etiology: cause of a disease • Pathogenesis: development of disease • Is this a type of symbiosis?

4. Normal Microbiota • In some cases it is normal for microbes to be growing.

5. Most mammals germ free in utero, are colonized after birth. • Microbes that establish permanent colonies inside or on outside of the body without causing disease are called normal microbiota. • Transient microbiota are microbes that are stable for a time then disappear.

6. Symbiosis • With normal microbiota, usually both species benefit from this arrangement. • Normal microbiota can prevent infections, may make necessary vitamins in return for nutrients form the host. (is called….. • Opportunistic microbes may cause disease under certain instances. • Probiotics are live microbes applied to or ingested into the body, intended to exert a beneficial effect.

7. Normal Microbiota on the Human Body Table 14.1

9. Propionibacterium acnes Staphylococcus epidermidis Staphylococcus aureus Candida spp Most microbes are transient on skin. Why? Skin

10. Eyes • Basically the same as that found on the skin. • Eyes have lysozyme, few nutrients, washing by tears.

11. S. aureus S. epidermides Streptoccoccus pneumoniae Haemophilus Neisseria Nose and throat

12. Streptoccoccus Lactobacillus Actinomyces Bacteroides Fusobacterium Treponema Cornebacterium Candida Over 200 species Idea environment Is a diverse environment. How do we know what lives in the mouth? Mouth

13. Bacteroides Fusobacterium Lactobacillus Enterococcus Escherichia Enterobacter Proteus Klebsiella Shigella Candida Is essentially a chemostat Has a large resident microbiota Large intestine

14. Staphylococcus epidermidis Enterococcus Lactobacillus Pseudomonas Klebsiella Proteius In urethra Lactobacilli Streptococcus Staphylococcus Bacteroides Clostridium Candida albicans Trichomonas vaginalis in vagina is acidic Urogenital system

15. Koch’s postulates • Same pathogen must be present in every case of the disease • Pathogen must be isolated in pure culture • Pathogen isolated from pure culture must cause the same disease in a healthy, susceptible laboratory animal. • Pathogen must be isolated from this animal

18. Exceptions to Koch’s postulates • Are modified to establish etiologies of diseases caused by viruses and fastidious bacteria, which cannot be grown on defined media. • Some diseases are caused by a variety of microbes. • Some diseases such as S. pyogenes can cause several different diseases.

19. Some diseases can only occur in one organism so we cannot run the full Koch’s postulates. • Why?

20. Disease classification and codification • Vocab • Measurements • Recognition and patterns

21. Symptoms- change in body function • Diagnosis- identification • Sign- a measurable change • Syndrome- a specific group of symptoms or signs that always accompanies a specific disease. • Communicable diseases- transmitted directly or indirectly from one host to another.

22. Contagious disease- is easily spread from one person to another • No communicable diseases- are caused by microbes that normally grow outside the body and are not transmitted from one host to another • Clostridium tetani

23. Where, how bad and how much. Words to describe ID • Incidence- number of people contracting the disease • Prevalence- number of cases at a particular time • Frequency- is in terms of sporadic, endemic, epidemic and pandemic • Acute, chronic, subacute and latent • Herd immunity- is the presence of immunity in most of the population

24. Local infection- affects a small area of the body • Systemic infection- spread throughout the body • Bacteremia- bacteria in the blood • Septicemia- bacteria multiply in blood • Secondary infections- occur after a host is weakened from a primary infection • Subclinical- cannot be measured

25. Severity or Duration of a Disease • Acute disease Symptoms develop rapidly • Chronic disease Disease develops slowly • Subacute disease Symptoms between acute and chronic • Latent disease Disease with a period of no symptoms when the patient is inactive

26. Recognition and patterns of disease • Predisposing factors make the body more susceptible to disease they include • Gender • Climate • Age • Fatigue • Nutrition • Lifestyle • Drug treatments

27. What happens when a disease does occur? • Incubation period- is the time between the initial infection and the first appearance of signs and symptoms • Prodromal- period is the first mild signs and symptoms • Illness- is when the disease is at its height • Decline- signs and symptoms decline • Convalescence- time until the body returns to predisease state

28. The Stages of a Disease Figure 14.5

30. Spreading of Infection • Reservoir of infection – provides pathogen with conditions for survival • Human – carriers, asymptomatic or latent • Animal- zoonoses various routes • Nonliving Reservoirs – water, fertilizer ect

31. Transmission of Disease • Contact transmission • Direct person to person transmission • Indirect contact transmission • Fomite a nonliving transfer (1 meter, soiled goods) • Droplet transmission over short distances • Vehicle transmission (water, food, air) • Vectors (mechanical or biological) Transmission of Disease

32. Transmission of Disease Figure 14.6a & 8

33. Portals of entry and Exit • Pathogens have preferred portals of entry and exit. • Most common portals • Respiratory tract • Gastrointestinal tract • Urogenital tract • Blood to blood

34. Transmission of Disease • Vehicle Transmission by an inanimate reservoir (food, water) • Vectors Arthropods, especially fleas, ticks, and mosquitoes • Mechanical Arthropod carries pathogen on feet • Biological Pathogen reproduces in vector

35. Nosocomial (Hospital-acquired) infections • 5-15% get infections while in the hospital. • Microbes in hospital • Chain of transmission • Compromised host • Is a hospital the best place to be if you are sick?

36. Nosocomial (Hospital-Acquired) Infections • Are acquired as a result of a hospital stay • 5-15% of all hospital patients acquire nosocomial infections Figure 14.7, 9

37. Nosocomial Infections ANIMATION Nosocomial Infections: Overview Table 14.5

38. Common Causes of Nosocomial Infections

39. MRSA • USA100: 92% of health care strains • USA300: 89% of community-acquired strains Clinical Focus, p. 422

40. Which Procedure Increases the Likelihood of Infection Most? ANIMATION Nosocomial Infections: Prevention Clinical Focus, p. 422

41. Control of Nosocomial • Aseptic techniques • Hand washing (40% compliance) • Infection control staff

42. Emerging Infectious diseases • Ones that are new or changing • Global warming • Global transportation • Antibiotics • Breakdown in social order • Governance problems • Pesticides • Lack of vaccination • Lack of reporting

43. Epidemiology • Study of transmission incidence and frequency of disease. • Data are collected and analyzed in descriptive epidemiology • Analytical epidemiology- infected comp to uninfected • Controlled experiments • Case reporting • CDC reporting

44. CDC (Centers for Disease Control and Prevention) main source of epidemiologic info in US • Publishes Morbidity and Mortality Weekly Report, reports incidence and deaths.

45. Centers for Disease Control and Prevention (CDC) • Collects and analyzes epidemiological information in the U.S. • Publishes Morbidity and Mortality Weekly Report (MMWR) www.cdc.gov Morbidity: incidence of a specific notifiable disease Mortality: deaths from notifiable diseases Morbidity rate = number of people affected/total population in a given time period Mortality rate - number of deaths from a disease/total population in a given time

46. Epidemiology • The study of where and when diseases occur Figure 14.11

47. New fields of Biological study • Biological crimes? ASM paper

48. Nosocomial outbreak (page 445) • 7 year period 361 patients developed bacteremia • Burkholderia cepacia identified (same strain) • Infection within 36hr of IV • Disappears hrs after IV removed • Cleaning insertion site • Iodine is negative

49. Continued • Not found in povidone-iodine • In alcohol • Alcohol purchase as 90% and diluted in pharmacy. • Used the same 100l container • Used the same tap water • Tap water contaminated

50. How do you prevent this from happening?