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Selected Diesease in Humans. Bacterial Diseases Viral Diseases Fungal Diseases Protozoan Diseases. Bacterial Diseases. Pathogenic bacteria typically enter through a specific portal of entry and begin as a localized infection; some bacteria have more than one portal

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selected diesease in humans
Selected Diesease in Humans
  • Bacterial Diseases
  • Viral Diseases
  • Fungal Diseases
  • Protozoan Diseases
bacterial diseases
Bacterial Diseases
  • Pathogenic bacteria typically enter through a specific portal of entry and begin as a localized infection; some bacteria have more than one portal
  • Many bacterial pathogens can spread from the initial site to other areas of the body
  • Many bacterial infections have been effectively treated with antibiotics; evolution of drug resistance in some strains have made them difficult to treat
  • Several important pathogens are curtailed through the use of vaccines
bacterial diseases3
Bacterial Diseases
  • Selected airborne bacterial pathogens
    • Streptococcus pyogenes
      • Gram + cocci, Lancefield serological group “A”, catalase negative, beta hemolytic
      • Associated with streptococcal pharyngitis, scarlet fever (with erythrogenic toxin-producing strains), systemic infections, immune-related complications such as rheumatic fever and glomerulonephritis, and a skin infection called erysipelas
bacterial diseases4
Bacterial Diseases
  • Selected airborne bacterial pathogens
    • Neisseria meningitidis
      • Gram negative diplococcus; fastidious; cultured on chocolate agar
      • Highly contagious
      • Generally begins as an upper respiratory tract infection; may spread into bloodstream and then to the meninges
      • Symptoms of meningitis: “stiff neck,” headache, dizziness, disorientation, seizures, coma, death
bacterial diseases5
Bacterial Diseases
  • Selected airborne bacterial pathogens
    • Mycobacterium tuberculosis
      • Acid-fast rods, grows very slowly in culture
      • Detected by acid-fast stains of sputum, lung x-ray, culture
      • Tuberculin skin test determines if someone has been exposed to M. tuberculosis, but doesn’t necessarily mean the person has tuberculosis
      • Symptoms: Cough; destruction of lung tissue; tubercle formation in lungs; spread to other areas of the body with tissue damage
bacterial diseases6
Bacterial Diseases
  • Selected airborne bacterial pathogens
    • Legionella pneumophila
      • Gram negative aerobic rods; natural habitat is highly aerated aquatic environments such as streams
      • May contaminate bulding ventilation systems, water faucets, or other moist surface and is transmitted to humans who come into aerosols created from these sources
      • Symptoms: Mild to severe pneumonia (lung infection with fluid buildup in the lungs)
bacterial diseases7
Bacterial Diseases
  • Selected foodborne bacterial pathogens
    • Clostridium botulinum
      • Gram + anaerobic rods; forms spores; found in soil
      • Can contaminate raw or underprocessed foods; toxin forms in food before it is consumed, so it is a foodborne intoxication
      • Secretes botulinum toxin, a deadly neurotoxin that blocks nerve impulses at motor neuron end plate synapses and causes flaccid paralysis
      • Symptoms begin as soon as the toxin begins to be absorbed in the stomach
      • Death is due to respiratory and cardiac failure
bacterial diseases8
Bacterial Diseases
  • Selected foodborne bacterial pathogens
    • Staphylococcus aureus food poisoning
      • Gram + cocci; catalase and coagulase positive; common skin flora
      • Some strains of Staph. Aureus produce an enterotoxin that can be secreted in contaminated food; toxin forms in food before it is consumed, so it is a foodborne intoxication
      • The toxin causes mild to moderate cramping and diarrhea; symptoms appear a few hours after consuming the food and usually last only a few hours
bacterial diseases9
Bacterial Diseases
  • Selected foodborne bacterial pathogens
    • Salmonella species
      • Gram negative rods; facultatively anaerobic; a member of Enterobacteriaceae
      • Transmitted in contaminated foods, especially meat, poultry, & dairy products
      • A foodborne infection: Bacteria must colonize the intestinal tract to cause symptoms
      • Cramping, nausea, diarrhea
      • Salmonella typhi causes typhoid fever: intestinal ulceration, invasiveness, rose-colored rash on abdomen, less diarrhea but very high fever
bacterial diseases10
Bacterial Diseases
  • Selected foodborne bacterial pathogens
    • Helicobacter pylori
      • Gram negative microaerophilic spirillum
      • Groes underneath the mucous layer in the stomach
      • A major cause of stomach ulcers
bacterial diseases11
Bacterial Diseases
  • Selected soilborne bacterial pathogens
    • Bacillus anthracis
      • Gram + facultatively anaerobic rods; forms spores
      • Found in contaminated soil or animals (livestock)
      • May either be transmitted through skin contact (cutaneous anthrax), oral ingestion (intestinal anthrax), or inhalation (pulmonary anthrax)
      • Lesions & tissue destruction occur at the affected sites
      • Pulmonary anthrax has close to a 100% fatality rate
bacterial diseases12
Bacterial Diseases
  • Selected soilborne bacterial pathogens
    • Clostridium tetani
      • Gram + anaerobic rods; forms spores; found in soil
      • May grow in contaminated wounds or cuts, where it produces the toxin tetanospasmin; a neurotoxin that acts as a cholinesterase inhibitor; mainly effects the central nervous system
      • Nerve synapses remain closed because cholinesterase fails to break down the neurotransmitter acetylcholine; this causes rigid paralysis
bacterial diseases13
Bacterial Diseases
  • Selected arthropodborne bacterial pathogens
    • Borrelia burgdorferi
      • Gram negative spirochaete; causative agent of Lyme disease
      • Transmitted through the bite of an infected deer tick (Ixodes)
      • Initial symptoms include fever, congestion, lymph node swelling, “flu-like” symptoms and the developemnt of a large, spreading rash (erythyma chronicum migrans) at the site of the tick bite
      • If untreated, inflammation & damage to joints, arthitis-like symptoms, and damage to the cardiovasular system can result
bacterial diseases14
Bacterial Diseases
  • Selected arthropodborne bacterial pathogens
    • Rickettsia rickettsiae
      • Gram negative rickettsia; a small, irregularly-shaped bacterium that is an obligately intracellular parasite
      • Causative agent of Rocky Mountain Spotted Fever
      • Transmitted through tick bites
      • Symptoms include high fever, a rash that begins as pinpoint spots at the extremities and spreads to the trunk of the body (macropapipular rash), seizures and coma
bacterial diseases15
Bacterial Diseases
  • Selected arthropodborne bacterial pathogens
    • Rickettsia prowasekii
      • Gram negative rickettsia; a small, irregularly-shaped bacterium that is an obligately intracellular parasite
      • Causative agent of epidemic typhus
      • Transmitted through human lice; predominately spread via body lice, not head lice or crab lice
      • Symptoms include high fever, a rash that begins as pinpoint spots on the trunk of the body and spreads to the extremities (macropapipular rash), seizures and coma; has a very high fatality rate
      • Easily spread under conditions of reduced sanitation where lice are likely to spread
bacterial diseases16
Bacterial Diseases
  • Selected bacterial STDs
    • Treponema pallidum
      • Gram negative spirochaete; transmitted via sexual contact or congenitally
      • Initial symptom (primary syphilis) is usually the appearance of a crusted, purple, painless lesion called a hard chancre at the site of infection; lesion usually disappears on its own after a few weeks but the infection remains in the blood
      • Later symptoms include fever, rash, & flu-like symptoms (secondary syphilis) and the formation of lesions called gummae throughout the body (tertiary syphilis), with neurological, cardiovascular, & other damage.
bacterial diseases17
Bacterial Diseases
  • Selected bacterial STDs
    • Neisseria gonorrhoeae
      • Gram negative diplococcus; fastidious; cultured on chocolate agar
      • Transmitted via sexual contact or congenitally
      • Urinary tract symptoms: Urethritis with painful urination & pus discharge; cystitis; kidney infection
      • Male reproductive symptoms: Prostatitis; epididymitis
      • Female reproductive symptoms: Infections of the vagina, cervix, uterus, Fallopian tubes; pelvic inflammatory disease
      • Eye infections (trachoma)
bacterial diseases18
Bacterial Diseases
  • Selected miscellaneous bacterial infections
    • Pseudomonas aeruginosa
      • Gram negative aerobic rod; commonly found in soil or aquatic environments
      • Can contaminate aerated moist surfaces such as faucets, respiratory equipment, etc.
      • A common cause of hospital-acquired (nosocomial) infections
      • Respiratory tract infections, urinary tract infections, and severe infections in burn patients
bacterial diseases19
Bacterial Diseases
  • Selected miscellaneous bacterial infections
    • Staphylococcus aureus infections
      • Gram + cocci; catalase and coagulase positive; common skin flora
      • Infections associated with Staph. aureus include pimples, boils, abscesses, carbuncles, septicemia, scalded skin syndrome in infants, toxic shock syndrome
viral diseases
Viral Diseases
  • Viruses are classified based on
    • nucleic acid structure (DNA or RNA; single- or double-stranded; segmented or nonsegmented)
    • capsid structure (helical, icosahedral, or complex)
    • envelope structure (enveloped or nonenveloped)
    • host (animal, plant, or bacteria)
    • mechanism of replication
    • site of infection (pneumotrophic, dermatotrophic, viscerotrophic, neurotrophic)
viral diseases21
Viral Diseases
  • Influenza
    • Member of Orthomyxovirus family
    • Segmented (8 segments), single-stranded, negative-sense RNA that encode 11 proteins
    • RNA is packaged into helical nucleocapsids and surrounded by an envelope
    • Two envelope proteins: hemagluttinin (H) and neuraminidase (N)
    • Three major types: Influenza A, Influenza B, & Influenza C; of which Influenza A strains are the most virulent in humans
viral diseases22
Viral Diseases
  • Influenza
    • Influenza can be transmitted via human-human airborne contact, or from contact with contaminated birds, swine, or other animals
    • Symptoms
      • in mild cases include fever, lymph node swelling, congestion, fatigue, primary & secondary pneumonia
      • Highly virulent strains may exhibit hemorrhaging from nose & mouth, ears, eyes, intestine, internal organs
      • Other complications include Guillian-Barre & Reyes syndrome
    • Antigenic variation and genetic recombination in the H & N proteins can lead to new strains of influenza
    • Each year epidemiologists determine the best “combination” vaccine for the year’s prevalent strains
viral diseases23
Viral Diseases
  • Influenza
    • Some important pandemics of influenza
      • H1N1: 1918-1920 “Spanish flu;” estimates of deaths worldwide range from 30 - 100 million people
      • H2N2: 1957-1958 “Asian flu” with 1 - 1.5 million deaths
      • H3N1: 1968-1969 “Hong Kong flu” with about 1 million deaths
      • H5N1: Current “avian flu” threat
        • Genotype first observed in 1959, but evolved into the current highly pathological strain that was discovered in 2004
        • No human to human transmission seen yet; cases have been bird to human contact
        • If human to human transmission were to evolve in this strain, experts have estimated that perhaps 5 - 150 million people could die worldwide
fungal diseases
Fungal Diseases
  • Properties of Fungi
    • Eukaryotic
    • Fungal cell walls with cellulose & usually with chitin
    • Heterotrophic metabolisms
    • Many are saprophytes; a few species are parasitic
    • Morphology: single cells (yeasts) or filaments (hyphae)
    • Most species have both sexual & asexual mechanisms of reproduction
fungal diseases25
Fungal Diseases
  • Candida albicans
    • Grows as a yeast or sometimes as short hyphae (pseudohyphae)
    • Common normal flora in the mouth, intestine, & vaginal tract
    • Competiton with bacterial flora helps keep Candida in check; conditions that reduce bacterial flora (e.g. antibiotic use) or weaken immune system (e.g. AIDS) can cause candidiasis infection to develop
    • Symptoms include oral candidiasis (thrush), intestinal candidiasis, and vaginal candidiasis
fungal diseases26
Fungal Diseases
  • Dermatophytic fungal infections
    • Infections of the hair, skin, nails
    • Several genera of dernmatophytic fungi: Microsporum, Epidermophyton, Trichophyton
    • Symptoms: Scaly, red or raised rash on skin (“ringworm”), discolored and splitting nails, hair loss
    • Often described by the term “tinea” with the name of the area infected: tinea corporis (ringworm of the body); tinea pedis (“athlete’s foot”); tinea unguium (ringworm of the nails); tinea cruris (“jock itch”); tinea barbae (ringworm of the beard)
protozoan diseases
Protozoan Diseases
  • Properties of Protozoa
    • A heterogeneous group of eukaryotic microbes
    • Generally characterized by lack of a cell wall and a heterotrophic metabolism (although one group, Euglena, is photosynthetic
    • Most are free-living; a few are parasitic
    • Classical classification based on mechanism of motility; rRNA data has shown the existance of more phyla than previously suspected
    • Motile by pseudopodia, flagella, cilia, or nonmotile
    • Most reproduce asexually; a few groups have complex sexual & asexual cycles
protozoan diseases28
Protozoan Diseases
  • Giardia lamblia
    • A flagellated parasite of humans and other mammals
    • Actively growing and reproducing form(trophozoite) grows in the intestinal tract of the host
    • In the intestine, trophozoites develop into cysts that are shed in the feces; the disease is transmitted when the next host ingests contaminated food or water and the cysts break open and develop into new trophozoites in the intestine
    • Symptoms: Profuse, foul-smelling diarrhea; dehydration; chronic recurrences
    • Often misdiagnosed; diagnosis requires microscopic or serological ID of trophozoites & cysts in stool or intestinal contents
protozoan diseases29
Protozoan Diseases
  • Toxoplasma gondii
    • Member of the phylum Apicomplexa, a group characterized as parasites with complex lifestyles having both sexual and asexual stages
    • The sexual stage develops only in members of the cat family, with sexual cysts (oocysts) shed in the feces
    • Oocysts are ingested by other animals (e.g. mice, cattle), where they travel to the muscle tissue & develop into asexual cysts (tissue cysts)
    • Cats acquire the parasite by ingesting the infected meat of prey such as mice
    • Humans acquire the parasite via the oral route, through contact with cat feces or ingestion of contaminated meat (often beef)
protozoan diseases30
Protozoan Diseases
  • Toxoplasma gondii (cont)
    • Infections in humans are often asymptomatic, except when the person is immunocommpromised, in which case encephalitis may develop
    • Pregnant women are at risk because the parasite can cross the placental barrier & infect the baby, with the possibility of birth defects or miscarriage
    • The parasite is very prevalent in humans, with estimates of 65% of people worldwide and 33% of people in the US over 12
    • Studies in mice suggest the parasite may actually alter its host’s behavior; e.g., mice exhibit riskier behavior such as less fear of cats. Some studies have suggested effects of the parasite on human behavior as well.
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