INFECTIOUS DISEASES: A Review
Host Factors in Defense
I. Host-Parasite Interactions
-infection process: adherence, colonization, multiplication (survive phagocytosis; nutrition), penetration
-acquisition: aerosols, contact with colonized materials, human-to-human, animal-to-animal, ingestion of contaminated food and drink, fomites (contaminated inanimate objects) and vectors
-carriers (the colonized)
-opportunistic infections (immunosuppressed are more susceptible)
-nosocomial infections (hospital-acquired)
II. Indigenous Flora
-skin (stratum corneum, upper hair follicles): staphylococcus
-conjunctiva
-nose and sinuses
-urogenital tract
-oral cavity: streptococcus
-blood and internal tissues are usually sterile
III. Natural Barriers to Infection
-mechanical barriers: skin, hair, mucous coating, shedding of keratinized cells, sneezing, coughing, vomiting, diarrhea
-chemical inhibition: sweat, tears, acid pH
-immunological barriers: humoral response (antibody), cell-mediated response (phagocytotic cell), genetic barriers
IV. Immunology
-ability to recognize antigens
-humoral immunity from antibodies, which have heavy and light chains
-antibody binding improves phagocytotic ability (opsonization), inactivates toxins, activates complement system, prevents attack of host cells
-cell-mediated immunity: lymphokines activate macrophages, which are directed to infected areas
-T lymphocytes: promote and regulate antibody synthesis (helper T, suppressor)
-B lymphocytes: carry out antibody synthesis
-tolerance to self-antigen circumvented by auto-immunity
-natural, artificial, active, passive
Streptococcus: pyogenes (A), bovis, pneumoniae
I. Description
-Gram-positive, non-motile, in chains or cells, fermentative
-catalase-negative facultative anaerobe
-within 15% of humans without signs of infection, attacks when immune down
II. Symptoms
-pharyngitis (strep throat), scarlet fever (rash), cellulitis, necrosis, myositis, toxic shock syndrome, edema, sepsis, endocarditis, impetigo
-can be accompanied by rheumatic fever, glomerulonephritis
III. Treatment
-penicillin G, erythromycin
-resistant to tetracyclines
Staphylococci: aureus, epidermidis, saprophyticus
I. Description
-Gram-positive, non-motile, in clusters
-catalase-positive facultative aerobe, but can be anaerobe
-pathogenic species produces coagulase, have a capsule
II. Symptoms
-aureus: folliculitis, carbuncles, scalded skin syndrome, food poisoning from enterotoxins, bacteremia, endocarditis, meningitis, pneumonia, osteomyelitis, toxic shock syndrome
-epidermidis: endocarditis; saprophyticus: UTIs
III. Treatment
-methicillin, nafcillin, cloxacillin; vancomycin
-resistant to penicillin, tetracycline, neomycin, chloramphenicol, erythromycin, gentamicin and kanamycin (aureus one of top ten resistant microbes)
Neisseria meningococci (meningitis)
I. Description
-Gram-negative cocci, in pairs, capsulated, detectable in spinal fluid
-inhabits nasopharynx, spreads through droplet inhalation
-highly contagious, attacks late winter, early spring � �campus disease�
II. Symptoms
-bacteremia, colonization of meninges, shaking, chills, prostration and petechial rash, can progress to fever, puerperal fever, vasomotor collapse, shock and death
-meningitis: headache, stiff neck, vomiting, coma
III. Treatment
-penicillin G-IV, though some are now resistant; rifampin; ceftriazone, chloramphenicol; cefotaxine; vaccines
Neisseria gonococci (gonorrhea)
I. Description
-Gram-negative cocci, in pairs, capsulated, pili formation
-many asymptomatic carriers, very common infection, STD
-can change antigens; has proteases that cleave IgA
II. Symptoms
- gonococcemia, arthritis, opthalmitis, perihepatitis, endocarditis
-urethritis, epididymitis, prostatitis, cervicitis, salpingitis, vulvovaginitis
III. Treatment
-normal immunity, ceftriaxone, cefixime, spectinomycin; resistant to penicillin
Bacillus anthracis (anthrax)
I. Description
-Gram-positive, rods in chains, aerobes, forms spores
-cutaneous/GI/inhalation anthrax, contact with infected animal/products
-lethal and edema toxins made of protective antigen and edema or lethal factor
II. Symptoms
-necrotic ulcers/lesions with black eschar, edema, fever, malaise, headache, ascites, bloody diarrhea, dysphagia, lymphadenopathy, erythema
-inhalation: pleural effusions, sepsis, bowel ulceration, hemorrhagic meningitis, necrosis, myalgia, hemorrhagic lymphadenitis
-GI uncommon, so abdominal pain, vomiting, bloody stool uncommon
III. Treatment
-penicillin, streptomycin, gentamicin, doxycycline, erythromycin, ciprofloxacin
-anthrax human and animal vaccines
Clostridium: botulinum (botulism), tetani (tetanus), difficile (diarrhea)
I. Description
-Gram-positive, motile, rods, anaerobes, usually in spores
-botulinum: types A, B and E; in packed foods eaten w/o cooking, blocks Ach
-tetani: in soil and animal feces, enters at injured point � tetanospasmin
-difficile: produces entero and cytotoxins
II. Symptoms
-botulinum: visual disturbance, speech difficulty, inability to swallow, gradual respiratory paralysis or cardiac arrest, no fever, �floppy baby�
-tetani: muscular spasms that spread throughout and halt respiration, much pain
-difficile: watery or bloody stool, abdominal cramps, fever, colon plaques
III. Treatment
-botulinum: trivalent (A,B,E) antitoxin reduces mortality rate, ventilation
-tetani: antitoxin and penicillin, muscle relaxants, sedation, removal of necrotic tissue, ventilation, active prevention, amoxicillin
-difficile: stop antibiotic use
Enterobacteriaceae: e. coli, shigella, salmonella
I. Description
-Gram-negative, 25 significant species, rods in colonies, facultative anaerobes
-e. coli: causes most UTIs, makes different enterotoxins and verotoxins, pilus, can cause gas by process of lactose, through contaminated food and drink too
-shigella: 40 serotypes, non-motile, highly communicable, exotoxin in GI tract, do not ferment lactose
-salmonella: do not ferment lactose or sucrose, form acid and sometimes gas (sulfurous), 2400 serotypes, oral route through contaminated food and drink
II. Symptoms
-e. coli: urinary frequency, dysuria, hematuria, pyuria, diarrhea, colitis, sepsis, meningitis, disease close to shigellosis
-shigella: abdominal pain, fever, watery and sometimes bloody diarrhea, dehydration, acidosis
-salmonella: fever, malaise, headache, constipation, bradycardia, mylagia, enlarged liver and spleen, low WBC, necrosis, hepatitis, organ inflammation, bacteremia, enterocolitis
III. Treatment
-e. coli: prevention, and treatments like for salmonella, quinolone for UTI
-shigella: ciprofloxacin, ampicillin, tetracycline, chloramphenicol
-salmonella: ampicillin, cephalosporin, and cholecystectomy
Chlamydia: trachomatis, pneumoniae, psittaci
I. Description
-obligate intracellular parasites; possess shared group antigens
-attacks eyes, genital tract, and respiratory tract
II. Symptoms
-trachomatis: nongonococcal urethritis, high white and red blood cell count, epididymitis, urethritis, cervicitis, pelvic inflammatory disease, sterility, ectopic pregnancy; conjunctivitis; papules on genitalia (in lymphogranuloma venereum)
-pneumoniae: pharyngitis, sinusitis
-psittaci: malaise, fever, headache, sore throat, pneumonia
III. Treatment
-sulfonamides, erythromycin, doxycycline, azithromycin, clarithromycin, good hygiene, safe sex
Rickettsia: prowazekii, typhi, rickettsii, akari (typhus, Rocky Mountain)
I. Description
-Gram-negative, rods, grow in embryonated eggs
-prowazekii: life cycle in humans and lice, also flying squirrel
-typhi: rat fleas; rickettsii: ticks; akari: mites on house mice
II. Symptoms
-prowazekii: epidemic typhus, fever, headache, malaise, prostration, rash
-typhi: endemic typhus, much milder
-rickettsii: Rocky Mountain spotted fever, like typhus but more rashes
-akari: Rickettsial pox, like chicken pox, but papules become eschars
III. Treatment
-prevention (delousing, rat-proofing, clearing vegetation, pasteurization of milk, vaccination), chloramphenicol, tetracyclines, no sulfonamides
Yersinia pestis (plague)
I. Description
-Gram-negative, nonmotile, cocci, facultative anaerobes, catalase+, oxidase-
-flea bites, septicemic and pneumonic plague (highly contagious) follow
II. Symptoms
-fever, chills, weakness, buboes (swollen lymph nodes), bacteremia, endotoxic septic shock, subcutaneous hemorrhages, pneumonia, vomiting, diarrhea, hypotension, altered mental status, renal/cardial failure, bloody sputum, meningitis and pharyngitis
III. Treatment
-streptomycin, gentamicin, tetracycline, chloramphenicol
-rat control, insecticide, isolation, plague vaccine
Mycobacterium tuberculosis (TB)
I. Description
-parasite, rods in globi, acid-fastness, obligate aerobes; no capsule or spore
-transmitted by close contact, exposure to droplet nuclei from excretions
II. Symptoms
-exudative lesions, chronic granulomas, chronic cough, spitting of blood, meningitis, UT involvement, fatigue, weakness, weight loss, fever
III. Treatment
-isoniazid, rifampin, pyrazinamide, ethambutol, streptomycin, then kanamycin, capreomycin, ethionamide, cycloserine, ofloxacin, ciprofloxacin
Mycobacterium leprae (leprosy)
I. Description
-parasite, rods in globi, acid-fastness, obligate aerobes; no capsule or spore
-in mice, armadillos and monkeys; most have natural immunity
-transmission not known for sure, probably aerial disbursement
-weakened immune system allows macrophages to become bacteria transport
II. Symptoms
-tuberculoid: pale lesions on cooler tissue of body, loss of sensation, secondary infections, early nerve damage, bacteremia, muscle atrophy, benign
-lepromatous: malign, leonine facies, bacteremia, many lesions, nerve palsies, large bacterial infestation and late nerve damage
III. Treatment
-multi drug therapy: dapsone, rifampicin, and clofazimine
-BCG vaccines, IMMLEP and ICR vaccines
Treponema pallidum (syphilis): Tuskegee Experiment
I. Description
-Gram-negative, rods, motile, no exotoxins, heat-sensitive
-transmitted through sex or placenta
-related to rural Bejel, Yaws and Pinta diseases
II. Symptoms
-chancres, lymphadenopathy, rashes, exudatory infectious lesions, fever, weight loss, sore throat, hair loss, muscle aches, meningitis later, as well as paresis
III. Treatment
-penicillin, erythromycin, tetracyclines
IV. Tuskegee Experiment
-black men at the Tuskegee Institute were given free �treatment� that consisted of injections of syphilis and frequent reobservations as to the results
-these men were recompensated by the US government after it became public knowledge
Severe Acute Respiratory Syndrome (SARS)
I. Description
-established as coronavirus, enveloped RNA virus that infects mucosal surfaces
-spike glycoprotein main marker of pathogenicity
-heavy droplet spread b/c of limited spread, environmental transmission
II. Symptoms
-fever, malaise, headache, myalgia, diarrhea, then nonproductive cough, dyspnea, respiratory failure
III. Treatment
-none, possibly glycyrrhizin or ribavirin; mainly prevention
Prions
I. Description
-proteinaceous infectious particles w/ no structure or nucleic acids
-occur normally, but abnormal form is toxic, and can convert normal to toxic
-elicits no immune response, long incubation periods, resistant to death, all forms are fatal, no cures once in late incubation
-can be acquired through infected food; replicates in spleen and lymph, attacks CNS through PNS; also point mutation in normal protein or spontaneous conversion
II. Symptoms
-scrapie: intense itch, ataxia, biting of limbs, inability to stand, irritability, lip-smacking
-bovine spongiform encephalopathy: nervousness, aggression, ataxia, weight loss
-chronic wasting disease: listlessness, blank expression, excessive drinking and urination, chronic weight loss, repetitive walking
-kuru: headache, joint pain, cerebellar tremor, ataxia, dysphagia, dementia, difficulty with excretion
-gss: ataxia, dementia, deafness, blindness, seizures
-fatal insomnia: insomnia, reduced attention, hallucination, ataxia, sweating
-creutzfeld-jakob disease: poor concentration, lethargy, visual disturbance, unsteadiness, ataxia, dysphais, mutism, seizures, agitation, dementia
III. Treatment
-quinicrine, chloropromazine, anti-PrP monoclonal antibodies
Human Papilloma Virus (HPV)
I. Description
-nonenveloped DNA virus, most common STD, infects 80% of sexually active females
-sexual contact or placental transmission, also other direct contact
II. Symptoms
-dysplasia, genital warts, plantar and hand warts, papillomas
III. Treatment
-imiquimod, interferon-alpha, podofilox, 5-fluorouracil, tumor necrosis factor
-vaccine
Congenital Infections
I. Description
-includes rubella, cytomegalovirus, herpes simplex, varicella-zoster (chickenpox), hepatitis B/C, enterovirus, and HIV
II. Symptoms
-disease symptoms, also malformations, fetal death, premature birth, retardation
Legionella pneumophila (Legionnaires� disease)
I. Description
-Gram-negative, aerobe, aerosol inhalation
II. Symptoms
-sometimes asymptomatic; fever, chills, malaise, muscle aches, nonproductive cough, hypoxia, diarrhea, delirium, pneumonia with reduced phlegm, leukocytosis, hyponatremia, hematuria, abnormal liver function; Pontiac fever, with dizziness and confusion
III. Treatment
-erythromycin, clarithromycin, rifampin, shock management
Borrelia burgdorgeri (Lyme disease)
I. Description
-spirochete, transmission through black-legged ticks
II. Symptoms
-skin lesions that expand slowly, flu-like illness, fever, chills, myalgia, headache; then meningitis, facial nerve palsy, cardia disease, arthritis, neck stiffness
III. Treatment
-doxycycline, amoxicillin, penicillin, probenecid; prevention of tick bites
German Measles/Rubella
I. Description
-DNA rubivirus, upper respiratory infection
-mild, self-limited illness
II. Symptoms
-malaise, fever, rash, arthralgia, arthritis, encephalitis
III. Treatment
-immune globulin intravenous
Rabies
I. Description
-RNA rhabdovirus, usually fatal, lyssavirus, with envelope, animal bites
II. Symptoms
-fatal encephalitis, malaise, anorexia, headache, photophobia, nausea, sore throat, fever, hydrophobia, sympathetic overactivity, increased salivation, convulsive seizures, coma, respiratory paralysis
III. Treatment
-rabies vaccines and antibodies
Hantavirus
I. Description
-RNA bunyavirus, mainly the Sin Nombre Virus, rodent-borne
-not cytopathic
-spread to humans through aerosolization from rodent feces
II. Symptoms
-fever, chills, myalgia, headache, GI symptoms, difficulty breathing, dizziness, nausea, abdominal pain, coughing, tachypnea, rales, tachycardia, hypotension
III. Treatment
-none specifically, but ribavirin works though it doesn�t have activity on SNV
Orthopoxvirus variola (Smallpox)
I. Description
-DNA virus with RNA polymerase
-�eradicated� by vaccine made by WHO after Jenner�s cowpox vaccination
-entrance into mucous membranes of respiratory tract
II. Symptoms
-fever, malaise, lesions, hemorrhagic rash
III. Treatment
-vaccinia immune globulin, methisazone
Measles
I. Description
-rubeola virus; gains entry through respiratory tract, spreads to lymphoid tissue
II. Symptoms
-fever, sneezing, coughing, running nose, red eyes, lymphophenia, Koplik�s spots, macopapular rashes, giant cell pneumonia with immune deficiencies
III. Treatment
-Vitamin A, ribavirin, live-virus vaccine
Herpesviruses: herpes simplex virus, varicella-zoster virus, Epstein-Barr
I. Description
-spherical DNA virions, can undergo genome rearrangements, direct contact
-herpes simplex: establish latent infections: type-1 and type-2; sexual contact
-varicella-zoster: highly contagious, infects upper respiratory tract
-Epstein-Barr: targets B lymphocytes, infects through saliva
II. Symptoms
-herpes simplex: usually asymptomatic, latent infection has cold sores; can progress to fever, sore throat, vesicular, genital and skin lesions, edema, gingivostomatitis, anorexia, malaise, keratoconjunctivitis, encephalitis
-varicella-zoster: malaise, fever, chickenpox lesions; zoster lesions with severe pain and neuralgia
-Epstein-Barr: headache, malaise, fatigue, sore throat, enlarged lymph nodes and spleen, hepatitis, mononucleosis, haity lesions, tumors
III. Treatment
-herpes simplex: acyclovir, vidarabine, vaccines
-varicella-zoster: no treatments if normal; acyclovir, valacyclovir, vidarabine, leukocyte interferon in immunocompromised individuals, vaccine
-Epstein-Barr: acyclovir, no vaccine
West Nile Virus
I. Description
-flavivirus, transmitted in mosquitoes
II. Symptoms
-viremia, lymphadenopathy, rash, meningitis, encephalitis, flu-like symptoms, neurological impairments, respiratory failure
III. Treatment
-permanent antibody immunity, mosquito abatement
Dengue
I. Description
-mosquito-borne infection, flavivirus
II. Symptoms
-fever, malaise, chills, headache, pains, itchy rashes, enlarged lymph nodes, phobia of bright light
-hemorrhagic fever; dengue shock syndrome
III. Treatment
-mosquito control
Ebola Virus
I. Description
-RNA filovirus
II. Symptoms
-fever, headache, sore throat, muscle pain, abdominal pain, vomiting, diarrhea, hiccups, rash, internal/external bleeding, bloodshot eyes, shock and then death
III. Treatment
-no vaccine; treatment to maintain renal function and electrolytic balance, combat hemorrhage and shock
Polio Virus
I. Description
-enteroviruses, infection through mouth, can be found in blood after multiplication in tonsils and neck lymph nodes, attack of CNS
II. Symptoms
-fever, malaise, drowsiness, headache, nausea, vomiting, constipation, sore throat; stiffness and pain in the neck
-flaccid paralysis from destruction of lower motor neurons, muscle atrophy
III. Treatment
-live-virus and killed-virus vaccines, trivalent oral vaccine
Hepatitis: B/C
I. Description
-DNA hepadnavirus, establishing chronic infections; RNA hepacivirus
-saliva, sexual transmission; exposure to blood
II. Symptoms
-infectious mononucleosis, yellow fever, cytomegalic virus infection, herpes simplex, rubella, jaundice, nausea, vomiting, anorexia, mild fever, skin rash, necrotizing vasculitis, glomerulonephritis
III. Treatment
-interferon-alpha, lamivudine, ganciclovir, foscarnet, ribavirin
Plasmodium: vivax, ovale, malariae, falciparum (malaria)
I. Description
-mosquito bites release ameboid parasites � the sporozoites � enters the liver where development continues
-falciparum infections are worst
II. Symptoms
-chills, nausea, vomiting, headache, sweating � in cycles, with hepatomegaly
III. Treatment
-chloroquine, quinine, primaquine, mefloquine, elimination of mosquitoes
Human Immunodeficiency Virus/ Auto-Immune Deficiency Syndrome (HIV/AIDS)
I. Description
-RNA retrovirus, a lentivirus, HIV-1 and HIV-2 differing in one gene
-infection transmitted by exchange of body fluids and persists indefinitely
-T lymphocytes and macrophages hold HIV during infection
II. Symptoms
-drop and rebound in CD4 cell numbers, fatigue, rash, headache, nausea, night sweat, suppression of immune system, opportunistic infections, diarrhea, dwindling, weight loss, fever, shortness of breath, hairy leukoplakia, lymphadenopathy, lethargy, muscle aches
-neurologic dysfunction, dementia, poor memory, inability to concentrate, apathy, retardation, cancers
III. Treatment
-nucleoside, nonnucleoside inhibitors of reverse transcriptase and inhibitors of viral proteases; antiretroviral drugs; triple drug therapy; zidovudine (AZT), HIV vaccines
-safe sex, communication with doctors and significant others