AHFAD University Microbiology Course Session 14 PDF

AHFAD UNIVERSITY FOR WOMEN School of Health Sciences Microbiology Course Session 14  Session 14 Genera of Medically Important Microbial Families BACTERIAL FAMILIES ENTEROBACTERIACEAE...

AHFAD UNIVERSITY FOR WOMEN School of Health Sciences Microbiology Course Session 14  Session 14 Genera of Medically Important Microbial Families BACTERIAL FAMILIES ENTEROBACTERIACEAE Domain: Bacteria, Kingdom: Eubacteria, Phylum: Proteobacteria, Class: Gammaproteobacteria, 1 Order: Enterobacteriales, Family: Enterobacteriaceae The Enterobacteriaceae are a large, heterogeneous group of Gram-negative rods whose natural habitat is the intestinal tract of humans and animals. Enterobacteriaceae currently has 53 genera (and over 170 named species). Morphology and General Characteristics: − Facultative anaerobe (bacteria that can grow in the presence or absence of oxygen). − Gram-negative, non-sporing, rod-shaped bacteria − Motility is by peritrichous flagella (except Shigella & Klebsiella are not motile). − Grow on bile-containing media (MacConkey agar) − Many are normal inhabitants of the intestinal tract of man and other animals. − Some are enteric pathogens and others are urinary or respiratory tract pathogens. − Differentiation is based on biochemical reactions and differences in antigenic − structure. − Causing 3 million deaths/year, and 4 billion infections worldwide. The family genera are: 1. Escherichia 2. Shigella 3. Citrobacter 4. Klebsiella 5. Hafnia 6. Enterobacteriaceae 7. Providencia 8. Edwardsiella 9. Pectinobacterium 10. Salmonella 11. Morganella 12. Enterobacter 13. Serratia 14. Proteus 15. Yersinia 16. Erwinia Mycobacteriaceae 2 The family Mycobacteriaceae has a single genus, Mycobacterium. Organisms belonging to this genus are quite diverse in their ability to cause disease in humans; some are strict pathogens, while others are opportunistic or nonpathogenic. Morphology and General Characteristics − Obligate aerobic organisms. − They do not take up stain well in the Gram-staining procedure but are considered Gram-positive. − Non-motile. − Rod-shaped bacteria with fastidious growth requirements. − These bacteria are characterized by their ability to form unique cell walls rich in mycolic acids, contributing to their resistance to many antibiotics and disinfectants. − These long-chain (C-60 to C-90) fatty acids in the cell wall make all mycobacterial species “acid-fast” as they resist acid-alcohol decolorization following staining with phenicated dyes like fuchsine, enabling their microscopic detection. Diseases caused by the species of the family are: Pseudomonadaceae Domain: Bacteria, Kingdom: Eubacteria, Phylum: Proteobacteria, Class: Gammaproteobacteria, Order: Pseudomonadales, Family: Pseudomonadaceae The Pseudomonadaceae are a family of bacteria which includes the genera: − Frateuria − Pseudomonas (the type genus) − Xanthomonas 3 − Zoogloea Morphology and General Characteristics − Gram-negative, rod-shaped, and polar-flagellated bacteria − Aerobic, non-fermentative bacteria − They are chemoorganotrophic with some species being chemolithotrophic using hydrogen or carbon dioxide for energy sources. − Species of these genera are common saprophytes in both fresh and marine waters and soil and are pathogenic to plants, animals, and humans. − Many members produce derivatives of the fluorescent pigment pyoverdine − The presence of oxidase and polar flagella and the inability to carry out fermentation differentiate pseudomonads from Enterobacteriaceae. Pseudomonas aeruginosa is the most common human pathogen. FUNGI FAMILIES Debaryomycetaceae Pathogen: Candida albicans 4 Morphology and General Characteristics − Candida albicans is a common commensal fungus that colonizes the oropharyngeal cavity, gastrointestinal and vaginal tract, and healthy individuals' skin. − Causes opportunistic infection in immunocompromised people. − Small, oval, measuring 2-4 µm in diameter. − Yeast form, unicellular, reproduces by budding asexually and doesn’t perform meiosis − Encapsulated and diploid, also form true hyphae. − Polymorphic fungus (yeast and pseudohyphal form) − 80-90% of the cell wall is carbohydrate Tremellaceae Pathogen: Cryptococcus neoformans 5 Morphology and General Characteristics − Found in the environment growing as unicellular yeast and they reproduce by budding. − Exists as a saprophytic and encapsulated yeast-like. − The yeast cells are dry, and light, making them easy to aerosolize. − Undergoes sexual reproduction forming dikaryotic hyphae and basidiospores supported by a club-shaped basidium with hyphae that have a complex septate. − Characterized by the presence of a polysaccharide capsule, the formation of melanin, and urease activity, which all function as virulence determinants. − Affect immunocompetent persons but more often in patients with HIV/AIDS, tuberculosis, hematogenous malignancies, and hospitalized patients majorly those with invasive devices causing meningitis. VIRAL FAMILIES Coronaviridae Pathogen: Coronavirus [Severe acute respiratory syndrome coronavirus-2 (SARS- CoV-2)] Realm: Riboviria Kingdom: Orthonavirae Phylum: Pisuviricota Class: Pisoniviricetes Order: Nidovirale Suborder: Cornidovirineae Family: Coronaviridae 6 Subfamily: Orthocoronavirinae Genus: Alpha-coronavirus ; Beta-coronavirus; Gamma-coronavirus; Delta-coronavirus Morphology and General Characteristics − Coronaviruses are enveloped, positive single-stranded RNAs. − They are spherical virions with a core-shell and a surface that resembles a solar corona based on its surface protein projections, hence their name (Latin: corona = crown). − There are four main genera; alpha-, beta-, gamma-, and delta- coronaviruses. − Alpha- and beta-coronaviruses originate from mammals, mainly bats, and are thought to cause more severe and fatal diseases in humans. − Gamma- and delta-viruses mainly originate from birds and pigs and are thought to cause asymptomatic or mild disease in humans. − Beta-coronaviruses have three important envelope proteins: Spike (S) protein, Membrane (M) protein, and Envelope (E) protein. − S protein mediates viral attachment to the cell membrane receptor, membrane fusion, and ultimately viral entry into the host cell. − M protein, the most abundant membrane protein, together with E protein are responsible for the coronavirus membrane structure. − Another component of the beta-coronavirus is the N protein, which is the protein component of the helical nucleocapsid that includes the genome RNA. Hepatitis Viruses 7 Morphology and General Characteristics: − Morphology is icosahedral either naked or enveloped, except HBV has three types of particles that include: 1, the 42 nm Dane particles (infectious virus); 2, the 22 nm HBsAg particles; 3, the 22 nm (diameter) HBsAg filaments. − These viruses cause Hepatitis, an inflammation of the liver. − There are 5 main hepatitis viruses, referred to as types A, B, C, D and E. − These 5 types are of greatest concern because of the burden of illness and death they cause and the potential for outbreaks and epidemic spread. − In particular, types B and C lead to chronic disease in hundreds of millions of people and, together, are the most common cause of liver cirrhosis and cancer. − Hepatitis A and E are typically caused by ingestion of contaminated food or water. − Hepatitis B, C and D usually occur as a result of parenteral contact with infected body fluids.