Chapter 13. Topics - Human Host - Progress of an Infection - Epidemiology

Transcription

1 Chapter 13 Topics - Human Host - Progress of an Infection - Epidemiology 1

2 Human Host Acquire resident flora New born exposure 2

3 Acquire resident flora The human body supports a wide range of habitats temperature, ph, nutrient, oxygen tension Wide range of microbes can inhabit Resident flora or microflora Microbes that inhabit but do not harm the host 3

4 Acquire resident flora Beneficial outcome Removed by immune system Microbial antagonism Adverse effects Escape immune system Multiply and disrupt tissue 4

5 The benefits and adverse effects of microbial contact. Fig Association between microbes and humans. 5

6 Locations on the host that harbor normal flora. Table 13.1 Sites that harbor a normal flora 6

7 Types of microbes and the anatomic sites they occupy. Table 13.3 Life on Humans: sites containing well-established flora and representative examples. 7

8 Invasion of normally sterile regions of the body can result in infection and disease. Table 13.2 Sterile (Microbe-free) anatomical sites and fluids 8

9 The absence of normal flora can have harmful effects. Table 13.A Effects of the Germ-free state 9

10 New born exposure Mother s birth canal Mother s breast milk Bottle-feeding People 10

11 Newborns will be exposed to different types of microbes depending on the source as well as their stage of development. Fig The origins of flora in newborns 11

12 Progress of an Infection Pathogenicity Portals of entry Attachment Surviving host defenses Causing disease Process of infections and disease Portals of exit 12

13 Pathogenicity True pathogens Opportunistic pathogens Virulence 13

14 True pathogen Cause disease in healthy individuals Associated with a specific and recognizable disease 14

15 Opportunistic pathogen Cause disease in immune compromised host Gain access (injury) to sterile regions 15

16 Factors that predispose a person to infections. Table 13.4 Factors that weaken host defenses and increase susceptibility to infections 16

17 Virulence Virulence factors Ability to establish itself in the host Cause damage 17

18 Portals of entry Most pathogens have specific portals on entry Skin Gastrointestinal tract Respiratory tract Urogenital Placenta Inoculum size 18

19 Skin Staphylococcus aureus Boils Haemophilus aegyptius Pinkeye 19

20 Gastrointestinal tract Salmonella, Shigella, Vibrio Viruses polio, hepatitis A Protozoan Giardia lamblia Enter via ingestion or the anal route 20

21 Respiratory tract Streptococcus pneumoniae Sore throat, meningitis Fungi Cryptococcus pneumonia 21

22 Urogenital Numerous sexual transmitted diseases (STDs) Virus human papillomavirus Genital warts Can lead to Cervical Cancer Go to Protozoan Trichomonas trichomoniasis Bacteria Neisseriagonorrhoeae Gonorrhea Acquire by intercourse or intimate contact 22

23 Common STDs which include viruses, protozoan, fungi, and bacteria. 23

24 Placenta Some bacteria can penetrate the placenta barrier Syphilis spirochete Birth canal Herpes simplex virus 24

25 A fetus can acquire an infection from the mother via transplacental infections. Fig Transplacental infection of the fetus. 25

26 Inoculum size Infectious dose (ID) minimum number of bacteria required to cause disease Low ID = high virulence 26

27 Attachment Adhesion Binding between specific molecules on both the host and pathogen Structures Capsules Pili or fimbriae Hooks 27

28 Example of how fimbriae and capsules are used to adhere to the host cell. Fig Mechanisms of adhesion by pathogens 28

29 Examples of different microbes, the disease they cause, and the structures used for adhesion. Table 13.6 Adhesion properties of microbes. 29

30 Surviving host defenses Antiphagocytic factors Capsule Prevent phagocytosis Leukocidins Toxic to phagocytes Some microbes survive inside phagocytes 30

31 Causing disease Virulence factors Exoenzymes Toxins Capsule Occurrence of infection Signs and symptoms 31

32 Virulence factors such as enzymes, toxins, and capsules contribute to host tissue damage. Fig Three ways microbes damage the host. 32

33 Exoenzymes Mucinase digest protective coating on mucous membranes Keratinase digest the principal component of skin and hair Collagenase digest the principal fiber of connective tissue Hyaluronidase digest the substance that cements cells together 33

34 Bacterial toxins Exotoxins Gram positive and Gram negative cells Excreted (ex. Hemolysins) Highly toxic in small amounts Endotoxins Gram negative cells Membrane associated Lipopolysaccharide (LPS) Fever associated 34

35 Exotoxins are released by the bacterium and directly affect different host organs, while endotoxins are released after the bacterium is lysed. Fig The origins and effects of circulating exotoxins and endotoxins. 35

36 Summary of the different characteristics associated with bacterial exotoxins and endotoxins. Table 13.7 Differential characteristics of bacterial exotoxins and endotoxins 36

37 Process of infections and disease Establishment Signs and symptoms 37

38 Establishment Localized Systemic Focal Mixed Primary and secondary Acute and chronic 38

39 Establishment of infections vary depending on location, type of microbe, and length of time. Fig The occurrence of infections with regard to location, type of microbe and length of time. 39

40 Signs and symptoms Signs - objective evidence of disease based on observation Inflammation edema, granulomas, abscesses Symptoms subjective evidence of disease based on the patient Inflammation fever, pain, soreness, swelling Syndrome sign and symptoms 40

41 Some commons signs and symptoms associated with infectious diseases. Table 13.8 Common signs and symptoms of infectious diseases 41

42 Portal of exit Enables pathogen to spread to other hosts Respiratory Salivary Skin Fecal Urogenital Blood Persistence 42

43 Representation of the different portals of exit. Fig Major portals of exit of infectious diseases. 43

44 Persistence Latency Viral Herpes virus Bacterial Tuberculosis Sequelae long-term damage to tissues or organs 44

45 Epidemiology The study of disease in populations Frequency data Distribution data Center for Disease Control and Prevention (CDC) 45

46 Epidemiology Statistics Strategies Reservoir Carriers Vectors Acquisition and transmission Nosocomial Koch s postulates 46

47 Statistical data can be represented graphically, and can be used to predict trends. Fig Graphical representation o epidemiological data. 47

48 The frequency of a disease in a population can be used to defined endemic, epidemic, sporadic, and pandemic diseases. Fig Patterns of infectious disease occurrence 48

49 Commonly reported diseases that are tracked in the United States. Table 13.9 Reportable disease in the U.S. 49

50 Reservoirs Carriers Vectors Nonliving 50

51 Carriers Asymptomatic Incubation Convalescent Chronic Passive 51

52 Examples of different types of carriers. Fig Carriers 52

53 Vectors Biological Participates in the pathogen s life cycle Infected with the pathogen Transmit by bites, defecation Mechanical Not part of pathogen s life cycle Not infected with the pathogen 53

54 Zoonotic infections are caused by vectors and animal reservoirs spreading their own infections to humans. Table Common zoonotic infections 54

55 A mosquito is a biological vector and the common house fly is a mechanical vector. Fig Two types of vectors. 55

56 Nonliving Reservoirs Soil Transmit bacteria, protozoa, helminths, fungi Transmit spores, cysts, ova, larvae Water similar to soil 56

57 Acquisition and transmission Communicable Non-communicable Patterns of transmission 57

58 Communicable Infected host transmits an infectious agent to another host Receiving host must become infected 58

59 Non-communicable Host acquires infectious agent From self (compromised individual)- microflora Nonliving reservoir - soil 59

60 Patterns of transmission Horizontal Vertical Direct (contact) Indirect 60

61 Horizontal Disease is spread through a population from one infected person to another Kissing, sneezing 61

62 Vertical The disease is transmitted from parent to offspring Ovum, sperm, placenta, milk 62

63 Direct (contact) Kissing, sex Droplets Vertical Vector 63

64 Indirect Contaminated materials Air Food, water, biological products (blood, serum, tissue), fomite (door knobs, toilet seats, etc.) Oral-fecal Droplet nuclei (dried microscopic residue) Aerosols (dust or moisture particles) 64

65 Communicable diseases are acquired by contact and indirect transfer. Fig Summary of how communicable infectious diseases are acquired. 65

66 A sneeze can release enormous amounts of moist droplets, and the dry droplets form droplet nuclei. 66

67 Nosocomial infections Infectious diseases that are acquired or developed from a hospital stay Urinary tract infections Respiratory infections Surgical incisions 67

68 The most common nosocomial infections. Fig Most common nosocomial infections. 68

69 To reduce nosocomial infections, different isolation procedures are used in hospitals. Table Levels of isolation used in clinical settings. 69

70 Koch s postulates Method used to determine the etiologic agent Ex. Toxic shock syndrome, AIDS, Lyme disease, Legionnaires 70

71 Steps associated with Koch s postulates. Fig Koch s postulates: Is this the etiologic agent? 71