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

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

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

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 Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 4 4

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 Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 5 5

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 Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 6 6

Copyright © 2007 by Saunders, an imprint of Elsevier Inc. Types of Pathogens Bacteria Viruses Fungi Protozoa Worms Arthropods Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 7 7

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

Microorganisms (Microbes) (cont’d.) Three shape groups of bacteria: Cocci (round): diplococci, streptococci, staphylococci Bacilli (rod-shaped) Curved rods: vibrios, spirilla, spirochetes Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 9

Anthrax Bacteria

E. Coli Bacteria

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

Staphylococcus aureus

Clostridium difficile (c. diff)

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

Virus

Influenza virus

Human immunodeficiency virus (HIV)

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

Fungi

Protozoa

Helminth (parasitic worm)

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

Gram positive bacilli

Gram negative cocci (Neisseria gonorrhoeae)

Mycobacterium tuberculosis

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

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

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

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)

The Spread of Infection (cont’d.) Copyright © 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved. 31 31

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

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

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)

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

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: 10.1073/pmas0807920105

Remember- wash your hands!