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Medical Laboratory Science · 500 Level
This is the complete lecture note for MLS 514 Medical Laboratory Microbiology II, prepared for Medical Laboratory Science students at 500 Level. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: MLS 514 Course title: Medical Laboratory Microbiology II Course credit load: 2 Units Series 1: General Characteristics And Classification Of Fungal Diseases • Part 1.1: General Characteristics Of Fungi • Sub-Part 1.1.1: Morphological features of fungi • Sub-Part 1.1.2: Physiological and ecological properties • Sub-Part 1.1.3: Differences between fungi and other microorganisms • Part 1.2: Classification Of Fungal Diseases • Sub-Part 1.2.1: Basis of classification (site of infection, pathogenicity) • Sub-Part 1.2.2: Major groups of mycoses (systemic, opportunistic, subcutaneous, cutaneous, superficial) • Sub-Part 1.2.3: Examples of fungi associated with each group • Part 1.3: Opportunistic Fungi And Their Significance • Sub-Part 1.3.1: Definition and characteristics of opportunistic fungi • Sub-Part 1.3.2: Common opportunistic fungal pathogens (e.g., Candida, Aspergillus) • Sub-Part 1.3.3: Clinical importance and conditions favouring opportunistic infections • Part 1.4: Recognition And Diagnosis Of Fungal Infections • Sub-Part 1.4.1: General approaches to laboratory identification • Sub-Part 1.4.2: Microscopy, culture, and biochemical methods • Sub-Part 1.4.3: Emerging diagnostic techniques
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Introduction Fungal diseases represent a significant area of medical microbiology because they affect humans in diverse ways, ranging from mild superficial infections to severe systemic conditions. Unlike bacteria and viruses, fungi have unique structural and physiological features that make their study essential for accurate diagnosis and effective treatment. This Series sets the foundation for understanding fungal infections by examining their general characteristics and classification, which are crucial for appreciating the broader scope of medical mycology. The aim of this Series is to introduce you to the fundamental characteristics of fungi and to guide you through the classification of fungal diseases, with particular attention to opportunistic fungi and the methods used for their recognition and diagnosis. We shall commence this Series by exploring the general characteristics of fungi, including their morphology, physiology, and how they differ from other microorganisms. Next, we will move on to the classification of fungal diseases, examining the basis of classification and the major groups of mycoses. Following that, we will consider opportunistic fungi and their clinical significance. Finally, we will wrap up by discussing the recognition and diagnosis of fungal infections, highlighting laboratory approaches and emerging techniques. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 define the morphological, physiological, and ecological characteristics of fungi, • SLO 1.2 explain the differences between fungi and other microorganisms, • SLO 1.3 classify fungal diseases based on site of infection and pathogenicity, • SLO 1.4 identify the major groups of mycoses and provide examples of fungi associated with each group, • SLO 1.5 describe the defining features of opportunistic fungi and analyse their clinical significance, • SLO 1.6 demonstrate general approaches used in the recognition and diagnosis of fungal infections. 1.1 General Characteristics Of Fungi 1.1.1 Morphological features of fungi Fungi are a diverse group of organisms that include yeasts, moulds, and mushrooms. The term morphology refers to the structure and form of an organism. Fungi may exist as unicellular forms such as yeasts, or as multicellular filamentous forms known as moulds. The filaments are called hyphae, and when they are collectively organised, they form a mycelium, which is the vegetative body of the fungus. Some fungi can switch between yeast and mould forms depending on environmental conditions, a property known as dimorphism. Fill in the blank: The vegetative body of a fungus, made up of hyphae, is called the ______.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1: Morphological forms of fungi 1.1.2 Physiological and ecological properties Fungi are eukaryotic organisms, meaning they have a true nucleus enclosed by a membrane. They are heterotrophic, which means they cannot produce their own food but rely on organic matter for nutrition. Many fungi are saprophytic, feeding on dead organic material, while others are parasitic, living on hosts and sometimes causing disease. Fungi reproduce by spores, which may be sexual or asexual, and these spores are often adapted for survival in harsh environments. Fill in the blank: Fungi that feed on dead organic material are described as ______. Plate 1.1: Saprophytic fungi on decaying material
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.1.3 Differences between fungi and other microorganisms It is important to distinguish fungi from other microorganisms such as bacteria and viruses. Unlike bacteria, fungi are eukaryotic and possess membrane-bound organelles. They also have cell walls composed of chitin, whereas bacterial cell walls are made of peptidoglycan. Viruses, on the other hand, are acellular and cannot reproduce independently, while fungi can grow and reproduce in suitable environments. These differences are crucial for diagnosis and treatment, since antifungal drugs target structures unique to fungi. Fill in the blank: The cell wall of fungi is composed of ______, unlike bacterial cell walls which contain peptidoglycan. Microorganism type Cell structure & wall composition Mode of reproduction Fungi Eukaryotic; chitin cell wall; membrane-bound organelles Reproduce by spores (asexual/sexual), budding, fragmentation Bacteria Prokaryotic; peptidoglycan cell wall; no nucleus Binary fission; some exchange genetic material via plasmids Viruses Acellular; no cell wall; protein capsid ± lipid envelope Require host cells for replication; use host machinery to produce viral particles Box 1.1: Key differences between fungi, bacteria, and viruses Pilot questions 1.1 1. What is the vegetative body of a fungus called? 2. Define dimorphism in fungi. 3. What term describes fungi that feed on dead organic material? 4. What is the main component of fungal cell walls? 5. State one difference between fungi and viruses. 1.2 Classification Of Fungal Diseases 1.2.1 Basis of classification Fungal diseases, also known as mycoses, are classified according to the site of infection and the pathogenicity of the causative fungi. The site of infection may be superficial, cutaneous, subcutaneous, or systemic. Pathogenicity refers to the ability of a fungus to cause disease, which may vary depending on the host’s immune status. Opportunistic fungi, for example, may not cause disease in healthy individuals but can lead to serious infections in immunocompromised patients. Fill in the blank: Fungal diseases are classified based on the site of infection and the ______ of the causative fungi.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.2: Basis of classification of fungal diseases 1.2.2 Major groups of mycoses The major groups of mycoses include: • Systemic mycoses, which affect internal organs and can be life-threatening. • Opportunistic mycoses, which occur mainly in individuals with weakened immunity. • Subcutaneous mycoses, which involve deeper layers of the skin and connective tissue. • Cutaneous mycoses, which affect the skin, hair, and nails. • Superficial mycoses, which are limited to the outermost layers of the skin and hair. Each group has distinct clinical features and requires specific diagnostic approaches. Fill in the blank: Mycoses that affect the skin, hair, and nails are classified as ______ mycoses. Group of mycoses Key description Systemic Affect internal organs; often severe and potentially life-threatening infections Opportunistic Occur in immunocompromised hosts; caused by normally harmless fungi Subcutaneous Involve deeper layers of skin and connective tissue; often follow traumatic implantation Cutaneous Affect skin, hair, and nails; caused by dermatophytes Superficial Limited to outermost skin and hair layers; primarily cosmetic impact Box 1.2: Major groups of mycoses
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.2.3 Examples of fungi associated with each group Examples of fungi associated with each group include: • Systemic mycoses: Histoplasma capsulatum, Blastomyces dermatitidis. • Opportunistic mycoses: Candida albicans, Aspergillus fumigatus. • Subcutaneous mycoses: Sporothrix schenckii, agents of chromoblastomycosis. • Cutaneous mycoses: dermatophytes such as Trichophyton species. • Superficial mycoses: Malassezia furfur, which causes tinea versicolor. Fill in the blank: The fungus Candida albicans is commonly associated with ______ mycoses. Group of mycoses Examples of fungi Systemic Histoplasma capsulatum, Blastomyces dermatitidis Opportunistic Candida albicans, Aspergillus fumigatus Subcutaneous Sporothrix schenckii, chromoblastomycosis agents Cutaneous Trichophyton species Superficial Malassezia furfur Table 1.1: Examples of fungi associated with each group of mycoses Pilot questions 1.2 1. On what basis are fungal diseases classified? 2. Name the five major groups of mycoses. 3. Which group of mycoses affects internal organs? 4. Give one example of a fungus associated with opportunistic mycoses. 5. Which fungus is responsible for tinea versicolor? 1.3 Opportunistic Fungi And Their Significance 1.3.1 Definition and characteristics of opportunistic fungi Opportunistic fungi are organisms that normally do not cause disease in healthy individuals but can become pathogenic when the host’s immune system is weakened. These fungi take advantage of compromised immunity, prolonged antibiotic use, or underlying medical conditions. They are often part of the normal flora or present in the environment, but under favourable conditions they can invade tissues and cause serious infections. Fill in the blank: Opportunistic fungi cause disease primarily in individuals with weakened ______ systems.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.3: Opportunistic fungi
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