Chapter 37 Introduction to Microbiology Microbiology Unit 7 Chapter 37 Introduction to Microbiology Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Microbiology Basics A basic understanding of the characteristics of bacteria, fungi, and viruses will aid the veterinary technician in collection, handling, and evaluation of samples Identification of bacterial, fungal, and viral pathogens is the primary purpose of microbiologic examinations Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Bacterial Cell Morphology Prokaryotic – no nuclear membrane Most cellular organelles are absent, except cell walls, plasma membranes, and ribosomes Some may contain capsules and flagella and can develop endospores Small – 0.2 to 2.0 mcg Have requirements for temperature, pH, oxygen tension, and nutrition Considered when collecting and preparing samples Used to help identify samples Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Oxygen Requirements Obligate aerobes – require O2 to survive Obligate anaerobes – growth inhibited or killed in the presence of O2 Facultative anaerobes – can survive in O2 but growth is limited Microaerophilic – prefer reduced O2 tension Capnophilic – require high levels of carbon dioxide Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Other Requirements pH – most live in the range of 6.5 to 7.5 Nutritional Fastidious microbes – strict nutritional requirements Agar medium Temperature Mesophiles – nearly all pathogenic bacteria in animals grow best at 20° to 40° C Psychrophiles – lower temperatures Thermophiles – higher temperatures Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Morphology Classified by shape and arrangement Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Morphology (cont.) Classified by arrangement Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Spores Some genera of bacteria have endospores Resistant to heat, desiccation, chemicals, and radiation Location in cell helps classify Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Bacterial Growth Contain a single DNA strand and reproduce primarily by binary fusion 4 phases Initial – lag phase – adapting to new media Exponential – doubling or rapid growth Continues until nutrients are used up, waste products accumulate, or space is limited Stationary – no net increase or decrease Final – death phase Spore formation occurs during this phase Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Bacterial Growth (cont.) Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Fungal Characteristics Heterotrophs Parasitic or saprophytic (decomposers) Most multicellular – except yeast Eukaryotic cells with cell walls of chitin Large webs (mycelium) of slender tubes (hyphae) Grow toward food sources Digest food internally – enzymes Yeasts reproduce by budding Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Fungi Reproduction Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Pathogenic Fungal Organisms Based on type of reproductive structures Basidiomycetes – mushrooms or club fungi Ascomycetes – cup fungi Zygomycetes – molds Deuteromycetes – fungi imperfecti No known sexual stage occurs Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Virology Most testing done in specialized laboratories Include histopathologic and serologic, electron microscopy, and attempted isolation of the virus Many viral diseases are diagnosed on clinical and pathologic grounds Serologic tests Paired serum samples collected 2 to 3 weeks apart Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Virology (cont.) Isolation is expensive and time consuming Testing May provide a diagnosis after death or recovery In some instances, ID should be attempted Not seen before Public health issue Epizootic Testing Collect aseptically, keep a 4° C, and take to laboratory ASAP Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Cell Culture Viruses need living cells to grow and replicate Animals’ cells grown in vitro Continuous cell lines and a single cell type Fetal kidney, embryonic trachea, skin from laboratory animals Inoculated into the primary culture from the same species from which the specimen was taken Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Immunologic and Molecular Diagnostics Examination Clinical signs and cell culture may identify the virus to a family level and maybe genus and species level, but definitive ID requires serologic procedures In-house tests are available for some viral pathogens Molecular testing – PCR is also used to ID pathogens Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Summary Bacterial morphologic characteristics are based on shape and arrangement of cells Bacteria vary in requirements for oxygen, temperature, and nutrients Some bacteria have specialized structures that can aid in identification Different fungal groups produce different spores Yeasts reproduce by budding – not spores Fungi are classified by reproductive structures Viral culture is performed in specialized laboratories Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.