Human Immunodeficiency Virus (HIV)

Transcription

1 The Microbial Size

2 The Viruses

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5 Human Immunodeficiency Virus (HIV)

6 Human Cytomegalovirus (HCMV)

7 Electron Micrograph Images of Viruses Influenza virus (RNA virus) Rotavirus (RNA virus)

8 Adenovirus, showing its icosahedral nature

9 A partially lysed cell of Vibrio cholerae with attached virions of phage CP-T1.

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15 Major groups of viruses DNA Viruses Virus family Envelope present Capsid symmetry Particle size (nm) DNA structure * Medically important viruses Adenoviridae No Icosahedral ds linear Adenoviruses Hepadnaviridae Yes Icosahedral 42 Ds incomplete, circular Hepatitis B virus Herpesviridae Yes Icosahedral 100** Ds linear Herpes simplex virus varicella-zoster virus cytomegalovirus Poxviridae Yes Complex 250x300 Ds linear Smallpox virus

16 Major groups of viruses RNA Viruses Virus family Envelope present Capsid symmetry Particle size (nm) RNA structure * Medically important viruses Picornaviridae No Icosahedral RNA structure Ss linear, nonsegmented, +ve Flaviviridae Yes? ssrna, +ve sense Retroviridae Yes Icosahedral Ss linear, 2 segments, >+ve sense Coronaviridae Yes Helical Ss linear, nonsegmented, +ve sense Paramyxoviridae Yes Helical Ss linear, nonsegmented, -ve sense Orthomyxoviridae Yes Helical Ss linear, 8 segments, -ve sense Poliovirus, rhinovirus hepatitis A virus enteroviruses Yellow fever virus heptitis C virus dengue virus West Nile virus HIV types 1 and 2 Coronavirus, SARS Measles, mumps, Respiratory syncytial virus Influenza virus

17 The Bacteria

18 Antony van Leeuwenhoek ( ) French biologist Louis Pasteur ( ).

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23 gram-positive Staphylococcus aureus Streptococcus pyogenes Streptococcus pneumoniae (diplococci)

24 MacConkey agar plate inoculated with Escherichia coli (red) and Klebsiella pneumoniae (pink) using the streak plate technique. (Mary Allen, Hartwick College)

25 Gram negative Rods E. coli Neisseria gonorrhoeae Spirillum minus

26 E. coli Campylobacter jejui

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28 NUTRITION All pathogenic bacteria are heterotrophic In aerobic metabolism (i.e. aerobic respiration), complete utilization of an energy source such as glucose produces 38 molecules of ATP. Anaerobic metabolism utilizing an inorganic molecule other than oxygen as the final hydrogen acceptor (anaerobic respiration) is incomplete and produces fewer ATP molecules than aerobic respiration. Anaerobic metabolism utilizing an organic final hydrogen acceptor (fermentation) is much less efficient and produces only two molecules of ATP.

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30 Bacterial growth and division are important targets for antimicrobial agents Antimicrobials that target the processes involved in bacterial growth and division include: Quinolones (nalidixic acid and norfloxacin), which inhibit the unwinding of DNA by DNA gyrase during DNA replication; The many inhibitors of peptidoglycan cell wall synthesis (e.g. beta-lactams such as the penicillins, cephalosporins and carbapenems, and glycopeptides such as vancomycin).

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36 Rickettsia Is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci (0.1 µm in diameter), rods (1-4 µm long) or thread-like (10 µm long) Obligate intracellular parasites, the Rickettsia depend on entry, growth, and replication within the cytoplasm of eukaryotic host cells (typically endothelial cells) Cannot live in artificial nutrient environments and are grown either in tissue or embryo cultures (typically, chicken embryos are used). The majority of Rickettsia are susceptible to antibiotics of the tetracycline group Carried by ticks, fleas, and lice, and cause diseases such as typhus, Rocky Mountain spotted fever, and endemic typhus

37 The Fungi

38 Three types of infection (mycoses) are recognized superficial mycoses where the fungus grows at the body surface on skin or hair; cutaneous and subcutaneous mycoses where nails and deeper layers of the skin are involved; systemic or deep mycoses with involvement of internal organs. This category includes the opportunistic fungi that cause disease in patients with compromised immune systems.

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42 Cryptococcus neoformans

43 KEY FACTS Fungi are distinct from plants and animals, have a thick chitinous cell wall, and grow as filaments (hyphae) or single-celled yeasts. Species causing disease may be acquired from the environment or occur as part of the normal flora. Infections may be located superficially, in cutaneous and subcutaneous sites, or in deep tissues. Infections are most serious in immunocompromised individuals

44 Prions

45 Prions are unusual infectious agents associated with a number of diseases in which there are degenerative changes in the brain Prions lack a nucleic acid genome and are highly resistant to all conventional forms of disinfection processes They are small proteinaceous particles, thought to be modified forms of a normal cellular protein, and cause disease by converting normal protein into further abnormal forms Transmission of prions in humans is by ingestion of contaminated material

46 Prions are unique infectious agents: There are a number of human and animal diseases-the spongiform encephalopathieswhose pathology is characterized by the development of large vacuoles in the CNS These include kuru and Creutzfeldt-Jakob disease (CJD) in humans Bovine spongiform encephalopathy (BSE) in cattle and scrapie in sheep

47 Their characteristics include: small size (< 100 nm, therefore filterable); lack of a nucleic acid genome; extreme resistance to heat, disinfectants and irradiation (but susceptible to high concentrations of phenol, periodate, sodium hydroxide, sodium hypochlorite); slow replication, diseases having a long incubation period and usually appearing late in life; incubation periods of up to 35 years in humans; cannot be cultured in the laboratory; do not elicit immune or inflammatory responses

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49 KEY FACTS Prions are unusual infectious agents, causing diseases characterized by changes in the brain (spongiform encephalopathies) and motor disturbances. Prions are host-derived glycoproteins and lack a nucleic acid genome. They are extremely resistant to disinfection procedures. Transmission of prions is usually by ingestion of contaminated tissues, but can occur via medical procedures. Diseases caused by prions include kuru, Creutzfeldt- Jakob disease (CJD), new variant CJD and bovine spongiform encephalopathy (BSE).