1. Microbiology Basics Chapter 5 Lisa Ochs BSN, RN 2008
Modified from Elsevier’s TEACH manual
Lisa Ochs BSN, RN 2008

2. What is Disease?
Disease is the failure of the body to function normally
Pathogen- a disease producing microorganism
Infection- invasion of the body by a pathogen
Localized infection: restricted to one area
Systemic infection: more widespread, usually spread through the blood

3. Disease Not all diseases are caused by a pathogen Diseases can be
Genetic (inherited) conditions
Birth defects
Autoimmune disorders
Metabolic disorders
Cancerous diseases
Degenerative diseases
Disorders caused by environmental toxins, trauma or nutritional deficiencies

4. Key Microbiological Terms
Definition
Antibiotics
Chemicals used to treat bacterial infections
Communicable disease
Any disease that can be spread from one host to another
Epidemic disease
Disease acquired by many people in a given area over a short period of time
Epidemiology
Study of occurrence and distribution of a disease in a population
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5. Key Microbiological Terms (cont’d.)
Definition
Incubation period
Lapsed period of time from exposure to a pathogen to the development of the symptoms of the disease
Normal flora
Group of microorganisms that colonize a host without causing disease
Nosocomial infection
Hospital-acquired infection
Reservoir of infection
Continual source of infection
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6. Key Microbiological Terms (cont’d.)
Definition
Resistance
Ability to ward off disease
Sterilization
Process that destroys all living organisms
Vector
Carrier of pathogens from host to host
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7. Copyright © 2007 by Saunders, an imprint of Elsevier Inc.
Types of Pathogens
Bacteria
Viruses
Fungi
Protozoa
Worms
Arthropods
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8. Microorganisms (Microbes)
Bacteria: single-celled organisms
Have a cell wall, not just a cell membrane like human cells
Form spores to survive in harsh environments
Normal flora: organisms that harmoniously live in body without causing disease
Pathogenic bacteria cause damage by:
Entering and growing in cells
Releasing toxins that damage cells 8 8

9. Microorganisms (Microbes) (cont’d.)
Three shape groups of bacteria:
Cocci (round): diplococci, streptococci, staphylococci
Bacilli (rod-shaped)
Curved rods: vibrios, spirilla, spirochetes
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10. Anthrax Bacteria

11. E. Coli Bacteria

12. (methicillin-resistant Staphylococcus aureus)
MRSA
(methicillin-resistant Staphylococcus aureus)

13. Staphylococcus aureus

14. Clostridium difficile
(c. diff)

15. Microorganisms (Microbes) (cont’d.)
Rickettsiae and chlamydiae
Parasites classified as bacteria but smaller than bacteria
Reproduce within living cells
Viruses
Smallest pathogens, formed from DNA or RNA surrounded by a protein shell
Difficult to kill without damagin host’s cells

16. Virus

17. Influenza virus

18. Human immunodeficiency virus (HIV)

19. Microorganisms (Microbes) (cont’d.)
Other microbes include
Fungi
Protozoa
Parasitic worms (helminths)
Arthropods

20. Fungi

21. Protozoa

22. Helminth (parasitic worm)

23. Identifying Pathogens
Bacteria can be identified by staining with a dye
Gram Stain
Gram Positive (purple or blue)
Gram Negative (pink or red)
Acid Fast Stain
Retains red stain
Culture: pathogen sample collected and grown on a medium in a laboratory

24. Gram positive bacilli

25. Gram negative cocci
(Neisseria gonorrhoeae)

26. Mycobacterium tuberculosis

27. Appearance of bacteria as seen in Gram stains.
From Crowley
Appearance of bacteria as seen in Gram stains.

28. From Crowley
Sensitivity test, illustrating antibiotic-impregnated filter paper disks on surface of culture plate.

29. From Crowley
Closer view of two antibiotic-impregnated filter paper disks on culture plate.

30. The Spread of Infection
Portals of entry: where pathogens enter
Respiratory tract
Gastrointestinal tract
Genitourinary tract
Eyes
Skin
Parenteral route (penetration of skin or mucous membranes)

31. The Spread of Infection (cont’d.)
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32. The Spread of Infection (con’t)
Portals of exit: how pathogens leave the body
Respiratory tract
Gastointestinal tract
Genitourinary tract
Eyes
Breasts (breastmilk)

34. The Spread of Infection (con’t)
Handwashing is the most important procedure to prevent the spread of infection
Wearing gloves when handling blood or body fluids is extremely important

35. The Spread of Infection (con’t)
Pathogens spread through:
Person-to-person contact; either directly or by way of a contaminated object (fomite)
Environment-to-person contact (coming into contact with contaminated air, water, food, or soil)
“Tiny animal”-to-person contact (includes insects through bites or direct contamination by depositing germs on your food or person)

36. FYI
Results from a 2008 study published in Proceedings of the National Academy of Sciences:
Females have a higher diversity of bacteria on their hands than males perhaps due to a slightly higher skin pH in women, or perhaps the mix of sebum, sweat, and lotions, or maybe even hormonal differences they couldn't really say for sure at this point
Females have more bacteria living under the surface film of skin than males
4, 742 different species of bacteria were found in the whole group of subjects

37. FYI
The species each of has on our hands is a rather unique mix--only 5 (out of 4,742) species were found on every hand in the group
Most of the 150 or so different species of bacteria found on skin of an individual hand are beneficial or harmless only a small minority are pathogenic
The diversity of bacteria differs between a person's right hand and left hand
Hand washing (as practiced in this group) did not remove many of the bacteria (or the populations recovered rapidly after washing)
From Fierer, Hamady,Lauber & Knight (2008), The influence of sex, handedness, and washing on the diversity of hand surface bacteria, doi: /pmas

38. Remember- wash your hands!