1. Lecture #1-2 Introduction to Microbial Pathogens

2. Fig 20.1. Community water supply in a developing country

4. Recent microbes in the news Severe acute respiratory syndrome (SARS) West Nile virus Viral or bacterial meningitis Human immunodeficiency virus (HIV) Tuberculosis (drug resistant) Cholera and Malaria Bovine sphongiform encephalitis (Madcow disease) Salmonella

5. Microbial infection and pathogenesis Types of microbes - Bacteria, fungi and protozoa - Viruses, viroids, prions Pathogenesis - interactions of molecular events in replication of a microbe and host responses that can result in disease

6. Figs 1.5, 1.7, 1.9

7. Figs 1.10 and 1.11

8. Microbial infection + immune response = pathogenesis Patterns of infection or disease. acute - short-lived. persistent - continuous. latent - reoccurs. subclinical - carrier state, no symptoms

9. Common terms in epidemiology Table 20.1

10. Unifying concepts for replication and pathogenesis Microbe structure (eg. morphology, genome type and size, species or variant) determines how it interacts with -. host or host cells to replicate. the host immune response Knowledge of the interaction of microbe with cells provides insights into: clinical manifestations of infections and how to control or interfere with these

11. Impact of viruses Many discovered in the last 20 years Viral infections cause estimated 50% of all absenteeism from work and school Bacteriophages affect drug resistance and molecular biology eg. restriction enzymes and reverse transcriptase for cloning Study as tools to explore biological processes

13. Three things all microbes must do –1- Make more progeny –2- Spread and transmission –3- Evade host defenses Outcomes of these determine pathogenesis

14. Fig 20.1 Spread of pathogens

15. How do these microbes spread? Severe acute respiratory syndrome (SARS) West Nile virus Viral or bacterial meningitis Human immunodeficiency virus (HIV) Tuberculosis (drug resistant) Cholera and Malaria Bovine sphongiform encephalitis (Madcow disease) Salmonella

16. Reservoirs of infectious agents Carriers (asymptomatic or subclinical) Zoonotic diseases Environmental

17. Fig. 20.01a Reservoirs harbor potentially pathogenic microbes

18. Transmission Modes of transmission to humans - human to human - animal to human - insect to human Infection can be localized or systemic - replicates, remains in local area of entry - replicates, spreads by viremia to other sites

19. Fig. 20.01b Modes of transmission of microbes

20. Modes of transmission to or from a host Sites of microbe entry or shedding – Respiratory (secretions, aerosols) – Oral/enteric (food, water) – Urogenital (sexually transmitted) – Vectors (insects, needles, animals) – Contaminated tissues or body products

21. Fig. 20.01c Portals of entry

22. Some specific modes of virus transmission Skin infections - for most, skin lesions not significant means of transmission - exceptions are HSV in genital herpes, chicken pox from shingles, small pox in dried crusts- infectious for months, up to a year Respiratory tract infections - transmission in air depends on coughing, sneezing or infected secretions

23. Air bourne transmission Figure 20.3

24. Some specific modes of virus transmission (cont.) Semen - HIV - much less for CMV, hepatitis B - Human milk or colostrum - CMV, HTLV by mother to child - not a major transmission mode for hepatitis B, encephalitis viruses, mumps, rubella

25. Some specific modes of virus transmission (cont.) Salivary secretions - EBV, rabies -rare possibility for CMV, hepB -Gastroenteric transmission -stools eg. enteric virus, poliovirus, - rotavirus, hepatitis A - childcare centers, institutions, military camps - contaminated water from poor waste disposal - urine is not a major means of transmission

26. Host factors that affect susceptibility age of host underlying physiological conditions malnutrition genetic determinants gender environmental conditions others eg. stress, personal behavior

27. Trends in disease Reduction and eradication of disease Emerging diseases Epidemiology The study of factors that influence disease frequency and distribution

28. Fig. 20.08 National and worldwide surveillance of infectious diseases is critical

29. Fig. 20.09 Fig 20.9 Child with smallpox, an eradicated disease (polio, bubonic plague)

30. Fig 20.10 World Map of Emerging Diseases

31. Nosocomial infections Figure 20.11

32. Fig. 20.12

33. Nosocomial infections Hospital acquired disease Hospitals are reservoirs of infectious agents Hospitals enable transmission of infectious agents How to prevent nosocomial infections ?

34. Reservoirs Other patients Hospital environment Health care workers Patient’s own normal flora What procedures are used in dentistry?

35. Survival strategies of microbes Gain entry into host Multiply at local site Find suitable niche Overcome or subvert host defenses - outrun - antigenic change - hide in host - mimic host component - inactivate/down-regulate host response

36. ? Questions to consider What is the clinical disease manifestation? What microbe(s) causes the disease(s)? How does the microbe enter or leave the host? What is the target tissue(s) and means of replication? Is there damage from replication or immune response? What are the disease patterns? What are the controls, preventions or therapies? Specific distinguishing features