Lecture 1: Introduction to Medical Microbiology PDF

# Lecture 1: Introduction to Medical Microbiology ### AlmaaReFa Universiy, College of Medicine, Microbiology & Immunology Unit **Dr. Rasha Mokhtar Elnagar** M.B.B.C, MSc, PhD, MD Medical Microbiology and Immunolgy Associate Professor of Medical Microbiology & Immunolgy Consultant Microbiology &...

# Lecture 1: Introduction to Medical Microbiology ### AlmaaReFa Universiy, College of Medicine, Microbiology & Immunology Unit **Dr. Rasha Mokhtar Elnagar** M.B.B.C, MSc, PhD, MD Medical Microbiology and Immunolgy Associate Professor of Medical Microbiology & Immunolgy Consultant Microbiology & Immunolgy ## Definitions ### Microbiology? **Micro:** very small (needs a microscope to be seen). **Biology:** is the study of living organisms **Microbiology:** The science that study the microorganisms that cannot be seen without the use of a microscope. ## Classification of Microorganisms ### Acellular * They are not cells. * No cell membrane. * It is a nucleic acid protected by a protein coat. * They can live and reproduce only inside a living cell. * Ex. Viruses ### Cellular #### Prokaryotes * **Nucleus, Mitochondria, E.R., Golgi Complexes:** Absent. * **Example:** Bacteria #### Eukaryotes * Have true nucleus. * Many membrane bound organelles. * **Example:** Protozoa, Fungi, Helminths. ## Prokaryotes vs. Eukaryotes | Characteristic | Prokaryotes | Eukaryotes | |---|---|---| | Nuclear membrane, nucleus & nucleoli | No | Yes | | Membrane bound organelles | No | Yes, Mitochondria, Golgi Apparatus, Endoplasmic Reticulum | | Number of chromosomes | One chromosome without histones | Multiple chromosomes with histones | | Energy production | By the cell membrane | By mitochondria | | Ribosomes | 70s ribosome (50s & 30s) | 80s ribosome (60s & 40s) | | Cell wall | Peptidoglycan | Polysaccharide (if present) | | Multiplication | Simple binary fission | Mitosis & meiosis | | Examples | Bacteria | Fungi, Protozoa, Helminths | ## 1- Bacteria ### Classification of Bacteria Bacteria are classified according to their: 1. **Morphology (Shape & Arrangement)** 2. **Staining reaction (Gram stain, Acid fast stain)** 3. **Cell wall** ### 1- Morphological Classification (Shape & Arrangement) #### A) Cocci: Spherical or oval cells. * **Pairs:** diplococci: as Streptococcus pneumoniae, Neisseria species. * **Chains:** as Streptococcus pyogenes. * **Grape like clusters:** Staphylococci as Staphylococcus aureus. #### B) Bacilli: Rod shaped bacteria. * **Curved or Comma shaped**: Vibrio cholerae * **Club shaped**: Corynebacterium * **Coccobacilli**: Haemophilus influenzae #### C) Spirochetes: Long slender, spiral shaped with several coils. * Treponema * Borrelia * Leptospira ### 2- According to staining reaction #### 1- Gram stain * **Gram positive:** (appear violet) * Cocci: Staphylococcus, Streptococcus * Bacilli: Clostridium #### 2- Gram negative: (appear red) * Cocci: Neisseria, Moraxella. * Bacilli: Escherichia coli, Klebsiella, Vibrio, Haemophilus. #### 3- Acid Fast stain (Ziehl-Nielsen stain): * Acid fast bacilli: Mycobacterium tuberculosis ### 3- According to the cell wall * **Three groups:** 1. **Lacking Cell Wall: Mycoplasma.** 2. **Flexible Cell Wall: Spirochetes e.g. Treponema.** 3. **Rigid Cell Wall:** * **Filamentous bacteria:** e.g. Streptomyces (antibiotic producers). * **Simple Unicellular** * **Obligate intracellular bacteria:** e.g. Rickettsia, Chlamydia. * **Free-living bacteria:** ## Medically Important Bacteria An image describing the following: - **Lacking cell wall:** Mycoplasma - **Rigid cell wall:** - Filamentous - Gram positive - Cocci - Rods (bacilli) - Free living - Aerobic and anaerobic - **Flexible cell wall:** Simple unicellular - Obligate intracellular parasite - Gram negative - Cocci - Rods (bacilli) ## Test your understanding 1. Which of these have peptidoglycan in their cell walls? * A. Protozoa * B. Viruses * **C. Gram-positive bacteria** * D. Fungi 2. Which of the following bacteria is an example of Spirochetes ? * A. Vibrio cholera * B. Streptococcus pyogenes * **C. Treponema pallidum** * D. Neisseria species 3. Which of these is a Gram-positive bacteria? * **A. Staphylococcus aureus** * B. Mycobacterium tuberculosis * C. Escherichia coli * D. Neisseria species 4. Which of these is a Gram-negative cocci bacteria? * A. Staphylococcus aureus * B. Mycobacterium tuberculosis * C. Escherichia coli * **D. Neisseria species** ## Reference Lippincott Illustrated Microbiology 4th edition, Chapters: 1 ## Thank You An image with balloons and the text "Thank you"