The Human Body in Health and Illness, 4th edition Barbara Herlihy Chapter 5: Microbiology Basics

Lesson 5-1 Objectives Define disease and infection. Describe the types of bacteria by shape and staining characteristics. List the characteristics of the different types of pathogens. Not all diseases are caused by pathogens, but this chapter focuses on infectious diseases. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lesson 5-1 Objectives (cont’d.) Define portals of exit and portals of entry. List common ways in which infections are spread. Identify the microbiological principles described in six germ-laden stories. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

What is Disease? Disease: Failure of the body to function normally Pathogens: Disease-producing microorganisms Infection: Invasion of the body by a pathogen Localized: Restricted to a small area Systemic: More widespread; usually spread through blood A disease includes more than infection, although that is the focus of this chapter. What are three examples of noninfectious diseases? Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Microorganisms and Multicellular Pathogens Bacteria Viruses Fungi Protozoa Worms Arthropods Microorganisms can be discussed in these major groups.   Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Looking at Bacteria Single cell Have cell wall Often grouped by shapes, clusters Bacteria may or may not be pathogenic. In hostile environments, some bacteria form spores. Subgroups of cocci are staphylococci, streptococci, and diplococci. Subtypes of curved rods are Vibrio, Spirillum, and spirochete. One famous spirochete (Treponema pallidum) causes syphilis. Rickettsiae and chlamydiae are also classified as bacteria, even though they cannot reproduce independently. The latter causes a common STD. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Shapes of Bacteria 1. Coccus (round) Diplococci – arranged in pairs Streptococci – arranged in chains Staphylococci – bunches of grapes 2. Bacilli (long and slender) 3. Curved rods a. vibrio – slight curve and resemble a comma b. spirillum – long cell that coils like a corkscrew c. spirochete – tightly coiled spirilla capable of waving and twisting motions Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Images of Bacteria cocci Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Bacteria bacilli Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Vibrio, Spirillum, Spirochete Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Viruses, Fungi, Protozoa: Single Cell Organisms Virus consists of DNA or RNA with a protein shell. Viruses reproduce only within a host. Fungi cause mycotic infections. Protozoa are animal-like microbes. Viruses cannot act reproduce independently, but depend on the host organism. In this, they act as parasites. A virus has no cell wall. Most antibiotics function by destroying the cell wall of a bacterium, so they are ineffective against viruses. The subsets of protozoa are amebas, ciliates, flagellates, and sporozoa. Malaria is a mosquito-borne disease caused by Plasmodium malariae; it results in over 3 million deaths a year. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Protozoans Four main types Amebas Ciliates Flagellates Sporozoa Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Arthropods and Worms: Multicellular Organisms Round or flat Transmission by fecal-oral route Arthropods Animals with jointed legs Ectoparasites (mites and lice) and vectors (mosquitoes, biting flies, fleas, and ticks) Parasitic worms are called helminths. Most are transmitted through the fecal-oral route. Ectoparasites–like mites and ticks in humans—live on the surface of the body, causing itching. Arthropods such as mosquitoes, flies, and ticks are vectors for disease. Discuss the distinction between biological and mechanical vectors. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Identifying Bacteria in the Lab Staining Gram stain Gram-positive (purple or blue) Gram-negative (pink or red) Acid-fast stain (retains red stain) Culture: Pathogen sample collected and grown in a medium Because most bacteria are either gram-positive or gram-negative, Gram staining is an important first step in identifying the organism causing an infection. Cultured pathogens can be tested for their susceptibility to various antibiotics (culture and sensitivity test), matching the bug with the drug. In clinical settings, it is important that samples collected for laboratory analysis remain free of contamination. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Spread of Infection Portals of entry Respiratory tract Gastrointestinal tract Genitourinary tract Eyes Skin Parenteral route-injuries that penetrate the skin or mucous membrane Portals of entry are how microorganisms enter the body. Knowing the portal of entry helps with prevention of infection. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Spread of Infection (cont’d.) Portals of exit Respiratory tract Gastrointestinal tract Genitourinary tract Eyes(tears) Skin Breasts(milk) Portals of exit are how microorganisms leave the body. Knowing the portal of exit helps with prevention of infection. Ask students about how current infection control practices use this knowledge? Examples are washing and cooking food well to avoid E. coli infection, safe sex practices to avoid STDs, handwashing, and safe sneezing to avoid H1N1. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Spread of Infection (cont’d.) Modes of transmission Person-to-person Vector – living or nonliving object that transfers a pathogen from one organism to another Fomite – a nonliving vector Environment-to-person Contact with contaminated water, air, food, or soil Tiny animals-to-person Biological vector – responsible for part of the life cycle of the pathogen Mechanical vector – just carries the pathogen Ask students to give examples of each mode of transmission. Person-to-person contact involves droplet contact from a sneeze or cough and touching objects that were contaminated by another person. Environment to person contact involves coming into contact with contaminated air, water, food, or soil. “Tiny animal” to person contact includes insects in the spread of disease through bites (as in malaria) or direct contamination by depositing germs on your food. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Dr. Semmelweis screams, “Wash those Mitts!” Read the story of Dr. Semmelweis. What does the story tell us about nosocomial infection? Identify current parallels. H1N1 flu MRSA If using the six germ-ridden stories as the basis of small group discussion, provide each group with a photocopy of its slide and then view slides 13-18 as a class after the discussion. Each group can supply key points about the story and the instructor can amplify these points as needed. Use discussion of this story to emphasize points about nosocomial infection and handwashing. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Rick, Nick, and the Sick Tick Read the story of the sick tick. What does the story tell us about animal vector, reservoir of infection and zoonosis? How does the story illustrate the difference between a communicable disease and a contagious disease? Use this story to discuss vectors and contagious disease vs. communicable disease. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Flora and Her Vaginal Itch Read Flora’s story. What does this story tell us about normal flora, antibiotics, and superinfection? Use this story to emphasize points about normal flora, antibiotics, and superinfection. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Why Typhoid Mary Needed to Lose her Gallbladder Read Mary’s story. How does this famous historical event illustrate the concepts of carriers and reservoirs of infection? Use this story to emphasize points about reservoir of infection, carriers, and fecal-oral route of transmission. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

A Pox News Alert Read the account of the various uses of the term pox. Describe the range of conditions described as poxes, and identify the most important contemporary and historical examples. Use this slide to distinguish between the historical use of the term pox, a skin lesion, and contemporary medical focus on the type of virus causing a pox. Important contemporary examples: Varicella-zoster and its relationship to shingles; chickenpox “parties.” Historical example: The “great pox” or syphilis is not a pox at all because it is caused by a spirochete called Treponema pallidum. These more general concepts can also be pointed outvectors, portals and exit, and portals of entrance. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Chief of Staph Reports... Read the account of Staphylococcus-induced conditions. Name important resistant strains and explain what the story suggests about resistance. Use this story to emphasize the problems posed by resistant strains of microorganisms and the misuse of antibiotics. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.