SOME BASIC INFORMATION TO KNOW:

  • Types of Skin Lesions:
    • Abscess – caused by extracellular organism
    • Ulceration – caused by intracellular organism
  • Opportunistic — due to immunocompromised, overproliferation, proliferation in different body part.
  • Colonization vs. Infection:
    • Colonization — no immune response. Simply growing on tissue surface.
    • Infection — has immune response.
  • Carrier States:
    • Asymptomatic Carrier State — no disease
    • Incubatory Carrier State — disease during incubatory period of pathogen (needs to be strict pathogens!
    • Convalescent Carrier State — patient has recovered from disease but still has pathogen (still shedding the pathogen).
  • Infection vs Disease:
    • Infection — patient has been exposed and has elicited a measurable immune response
    • Disease — infection has progressed to point that there is damage to tissue or to bodily function. Infection does not always progress to disease!!
  • Reservoir vs. Sources:
    • Reservoir — where the organism replicates. Can be animals, can be water.
    • Sources — where the organism is immediately transmitted to man. Sources and reservoir can be the same but not always.
  • Types of Vectors:
    • Biological Vectors — insect that transmits infectious disease. Act as reservoir.
    • Mechanical Vectors — insect that transmits infectious disease. Acts as source. i.e. fly walking across your food carrying pathogens on their paws.
  • Transmission Routes:
    • Fomite — i.e. handkerchief
    • Zoonotic disease — animal to animal disease i.e. rabies.
    • Dead-end host — last host that pathogen can’t spread from.
  • Measures of Infectivity:
    • Pathogenicity — ability to cause VISIBLE disease
    • Infectious Dose 50 — number of microbes needed to INFECT 50% of exposed animals
    • Attack Rate — cases of disease per exposed causes
    • Virulence — ability to cause SEVERE disease
    • Lethal Dose 50 — number of microbes needed to KILL 50% of exposed animals.
    • Case Fatality Rate — number of deaths per clinically apparent cases
  • Clinical vs. Subclinical Infection
    • Clinical Infection — organism causes severe enough disease for patient to come to clinic
    • Subclinical Infection — very minor disease. i.e. Common Cold.
  • Transmission Patterns:
    • Point Source Outbreak — i.e. when everyone drank the same water to get the same disease outbreak. All cases from a point source outbreak will have same incubation period.
    • Continuous Source Outbreak — source not identified, so cases keep coming up. on graph, see multiple cohorts, one for each incubation period (see lotsa rise and fall)
    • Propagated Outbreak — person to person spread, taller successive waves of cases. Limited by Herd Immunity.
  • Acute vs. Chronic infection in serology:
    • Acute — IgM
    • Chronic — IgG
  • Sequelae vs. Complications:
    • Sequelae — long-term
    • Complications — temporary
  • Prodromal Period — first feelings of “not well” during disease at end of incubation period.
  • Signs vs. Symptoms:
    • Signs — what you observe
    • Symptoms — what you feel
  • Primary vs. Secondary Prevention:
    • Primary Prevention — prevent infection before exposure.
    • Secondary Prevention — prevent further progression of infection after exposure, i.e. rabies vaccine after exposure would stop the virus from progressing further before signs and symptoms show up.
  • Antibiotic Prophylaxis — giving antibiotics to asymptomatic people who we assume are carrying or will pick up a bacteria.
  • Patient Compliance — how much a patient is correctly following a medical advise.
  • Empiric Therapy — starting a therapy before you confirm what the disease actually is, usually to be on the safe side.
  • Aerobic vs. Anaerobic — what would they look like in a test tube?
    • Obligate Aerobic — all at surface
    • Obligate Anaerobic — all at bottom
    • Facultative Anaerobe Bacteria — most at surface (since aerobic conditions ideal but not required), but also spread throughout tube.
    • Microaerophiles — they gather just a little below the surface (require O2, but only a little bit)
    • Aerotolerant — all throughout tube (because not affected by O2)
  • Gram Negative vs. Gram Positive Color
    • Gram Positive — Purple
    • Gram Negative — Pink
  • Microscopy
    • Brightfield — light microscope
    • Darkfield — use for hard-to-see thin organisms like spirochetes
    • Fluorescent — use DFA (Direct Fluor. Ab stain), for organisms that are very virulent or difficult to culture.
    • Electron Microscopy — virus
  • Growth Media
    • Selective Media — selects for specific type — i.e. Thayer Martin Media selects for Neisseria
    • Differential Media — differentiates multiple organism — i.e. Blood Agar show different hemolysis pattern of different microbes
    • Enrichment Media — recovers hard-to-grow organisms. i.e. Cysteine Blood Agar
  • Differential Media (Blood Agar Plate)
    • Alpha hemolysis — greening of the blood
    • Beta hemolysis — complete lysis of the blood
    • Gamma hemolysis — partial lysis of the blood
  • Mannitol Salt Agar and MacConkey Agar are both selective and differential media.
    • Mannitol — Not only does the salt agar kill all bacteria but staph, only staph oreus ferments the mannitol on the agar.
    • MacConkey Agar — has dyes like Crystal Violet (which lets gram negatives grow). Then lactose differentiates between fermentors and nonfermentors.
  • Serotyping vs. Serology:
    • Serotyping – identify microbe’s antigens – use when organism is hard to grow or dangerous
    • Serology – identify patient’s immune status – use when organism is common or do not elicit antibody response until late into the disease (paired sera — take sera from two different times and look for rise in titer)
  • Sterilization vs. Disinfection:
    • Sterilization — eliminate all viable microbes
    • Disinfection — remove pathogens but not endospores
  • Classes of Drugs
    • Static — prevents growth
    • Cidal — destroys bacteria
  • If we use cidal antimicrobial, we rob our body from building up the immunity. But static antimicrobial is still useful, because it just stops the microbe from growing further and leaves enough for body to react.
  • If you choose to use empiric therapy, use a broad spectrum antibiotic! Because you are not sure what bacteria it is yet, so better to be broad.
  • Measures of Drug Susceptibility:
    • MIC — Minimum Inhibitory Concentration — smallest dose of drug needed to prevent growth of a microbe
    • AUC — Area Under the Curve — basically measures drug concentration for a duration time, used in pharmacies.
  • An example of synergy between two antibiotics
    • Penicillin or aminoglycoside is given, but not both, the cells are inhibited only.
    • Penicillin and aminoglycoside are given concurrently. Penicillin opens holes in the cell wall through with aminoglycosides can enter and reach the ribosomes and halt protein synthesis, therefore the cells are killed.
  • Drugs for Gram Negative vs. Gram Positive Bacteria
    • Gram negative – drugs has to get through LPS layer first. Need porin for drug to get across.
    • Gram positive – drug can easily get to them.
  • Know how to describe skin conditions:
    • Macular — red spots
    • Maculopapular — raised (edema)
    • Vesicular — fluid-filled sac 水泡
    • Bulla — large vesicular, often filled with blood.
    • Pustular — vesicular with pus (looks like pimple, cloudy fluid inside)
    • Petechial — hemorrhagic spots – evidence of blood underneath
    • Purpura — when petechials merge together… much larger.
    • Ecchymoses — even larger than purpura – bruise.
  • Causes of Maculopapular Examthems:
    • Streptococcus pyogenes (GAS)
    • Rubeola Virus
    • Rubella Virus
    • HHV6
    • Parvo B19 Virus
  • Causes of Vesicular Examthems:
    • Varicella-Zoster (Chickenpox, Shingles)
    • Coxsackie A
    • Variola (Smallpox)
    • Monkeypox
  • Causes of Stye:
    • Propionibacterium acnes
    • Staphylococcus aureus
  • Causes of Conjunctivitis:
    • Adenovirus
    • Neisseria gonorrhea
    • Hemophilus influenza
    • Streptococcus pneumoniae
  • Causes of Keratoconjunctivitis:
    • Fusarium
    • Chlamydia trachomatis
    • Pseudomonas aeruginosa
    • Acanthamoeba castellani
    • Aspergillosis
    • Onchocerca volvulus
    • Herpes Simplex Virus
    • Loa Loa
    • Bacillus cereus
  • Causes of Endophthalmitis:
    • Candida albicans
    • Bacillus cereus
    • Staphylococcus spp.
    • Pseudomonas aeruginosa
  • Causes of Retinitis:
    • Cytomegalovirus (HHV-5)
    • Toxoplasma gondii

KNOW THESE WORD ASSOCIATIONS FOR EXANTHEMS

  • Confluence of Rashes — Measles
  • No Confluence of Rashes — Rubella
  • German Measles — Rubella
  • Regular Measles — Rubeola
  • Paramyxoviridae — Measles, Mumps, Parainfluenza, RSV
  • H/F glycoprotein spikes –Measles, Mumps, Parainfluenza
  • F glycoprotein spike only — RSV
  • 3 C’s — Cough, Coryza, Conjunctivitis (symptoms of Measles)
  • Giant Cell Pneumonia — Paramyxoviridae (anything with Fusion peplomer, like Measles, Mumps, Parainfluenza, RSV)
  • SSPE — Measles sequelae
  • Newborn with ductus arteriosus, blindness, deafness, MR — Congenital Rubella Syndrome
  • Mother infected 1st trimester — Congenital Rubella Syndrome
  • Togaviridae Family — Rubella
  • ssDNA virus — B19 Parvovirus
  • Erythroid Tropism — B19 Parvovirus
  • Globoside Tropism — B19 Parvovirus
  • Erythema Infectiosum — B19 Parvovirus
  • Slapped Cheek Rash — Erythema Infectiosum (Fifth Disease),  B19 Parvovirus
  • Erythema Infectiosum (Fifth Disease) —  B19 Parvovirus
  • Rash in Sickle Cell Patients —  B19 Parvovirus
  • Infectious RNA — Rubella — because it has positive sense RNA
  • HHV-6 — Roseola
  • Linear dsDNA enveloped virus — Herpesviridae
  • Exanthem Subitum — Roseola (HHV-6)
  • Rash due to Delayed-Type Hypersensitivity — Strep Pyogenes
  • Rash due to T-Cells — Measles (Rubeola)
  • Rash due to Immune Complex — Rubella, Parvo, HHV-6 (Roseola)
  • Pastia’s Lines, Sandpaper skin, Circumoral Pallor, Strawberry Tongue — Scarlet Fever, Strep pyogenes
  • Scarletina — Strep pyogenes
  • SpeA, Spe B, Spe C — Strep pyogenes — A and C are superantigens
  • Transplacental Rash that kills fetus — Parvovirus
  • Low fever, followed by rash — German Measles/Rubella
  • High fever, followed by rash — Roseola (Exanthem Subitum)
  • Rash: Face → Trunk — Measles, Rubella
  • Rash: Chest → Extremities — Strep pyogenes (Scarlet Fever)
  • Pox & Cox — Vesicular Exanthems
  • dsDNA that replicates in cytoplasm — Poxviridae (smallpox, molluscum) → inclusion bodies.
  • Rash with mixed lesions — Varicella aka Chicken Pox
  • Rash with same-stage lesions — Variola aka Small Pox
  • Dew Drop on Rose Petal — Varicella aka Chicken Pox
  • Post-Herpetic Neuralgia — Shingles — complication of Shingles
  • Ramsay Hunt Syndrome — Shingles, Varicella → CN VII and VIII damage → facial palsy
  • CN VII and VIII damage — Ramsay Hunt Syndrome from Varicella
  • Aspirin use in Children — Reye’s Syndrome
  • Guarnieri bodies — Variola (Small Pox)
  • Variola — Small Pox
  • Small Pox — Variola
  • Rash: Face/Trunk –> Extremities — Chicken Pox aka Varicella
  • Rash: Face/Extremities –> Trunk — Small Pox aka Variola
  • Vaccinia Vacine — Smallpox
  • Hand, Foot, and Mouth Disease — Coxsackie Virus
  • Maculopapular Rash caused by Bacteria — Strep pyogenes (Scarlet Fever)
  • Replicates in T/B cells Rash — HHV-6 aka Roseola
  • Most Common Childhood Exanthem — HHV-6 aka Roseola
  • Roseola — HHV-6

KNOW THESE WORD ASSOCIATIONS FOR EYE DISEASES

  • Styes — Staph aureus and Propionibacterium acnes
  • Catalase/Coagulase Positive — Staph aureus
  • Protein A — Staph aureus
  • Protein M — Strep pyogenes
  • Glows Orange under Woods Lamp — Propionibacterium acnes
  • Grows in External Skin Fold — Staph aureus
  • Styes in children — Staph aureus
  • Styes in anyone — Proprionibacterium acnes
  • IgA Protease — Hemophilus influenza and Streptococcus pneumoniae
  • Conjunctivitis – Direct Contact — Hemophilus influenza
  • Conjunctivitis – Respiratory Droplets — Strep Pneumo
  • Conjunctivitis – Sexual Transmission — Neisseria gonorrhea
  • Conjunctivitis – Pools — Adenovirus
  • No Lancefield Strep — Strep pneumo
  • Lancefield A Strep — Strep pyogenes
  • Chocolate Agar — hemophilus influenza
  • Hemin and NAD required for growth — hemophilus influenza
  • PRP Capsule — Hemophilus influenza — makes it resistant to phagocytosis by PMNs.
  • Neufeld Reaction — Strep pneumo — against quellung capsule
  • Quellung Capsule — Strep pneumo
  • Destroyed by bile — Strep pneumo
  • Alpha hemolytic– Strep pneumo
  • PCV — Strep pneumoniae — Polyvalent capsular vaccine or Pneumococcal conjugate vaccine (for newborns)
  • Diplococcus — Neisseria gonorrhea
  • No O antigen (LOS) — Neisseria (gonorrhea and meningitidis)
  • Thayer Martin medium — Neisseria gonorrhea — selective for the organism.
  • Ophthalmia neonatorum — Neisseria gonorrhea
  • Nonpurulenet Conjunctivities — Adenovirus
  • Keratoconjunctivitis in Heroin User or Contact Lens — Bacillus Cereus
  • Keratoconjunctivitis in Sex workers — Chlamydia trachomatis
  • Keratoconjunctivitis in Burn Victims — Pseudomonas aeruginosa
  • Keratoconjunctivitis from Hot Tub or Contact Lens — Acanthamoeba castellani
  • Rapid Keratoconjunctivitis — B. Cereus and Pseudomonas
  • Slow Keratoconjunctivitis — Acanthamoeba
  • EB/RB Stages — Chlamydia trachomatis — Elementary Body and Reticulate Body (replication)
  • Energy Parasite — Chlamydia trachomatis
  • Ocular Trachoma — Chlamydia trachomatis
  • Inclusion Conjunctivitis — Chlamydia — because intracellular
  • Eyelash rubs on Eyeball — Chlamydia — Ocular Trachoma, Inclusion Conjunctivitis
  • McCoy Cells — Chlamydia — used to recover Chlamydia in the lab.
  • Hypopyon — Pseudomonas — when infect anterior chamber.
  • Ring Infiltrate — Pseudomonas and Acanthamoeba
  • Biofilm, Efflux Pump, Pigments, Exotoxin A — Pseudomonas
  • Exotoxin A — Pseudomonas — used to inhibit protein synthesis by interfering with EF-2.
  • Gram negative, Oxidase Positive, Strict Aerobe, Lactose nonfermentor — Pseudomonas
  • Trophozoite — Acanthamoeba
  • Fungal Keratitis — Aspergillus and Fusarium
  • Rastaman — Aspergillus
  • Phialides — Fusarium — flasked-shaped fruiting bodies
  • Flasked-shaped fruiting bodies — Fusarium — Phialides
  • Sabouraud dextrose agar — Fungi
  • Dendritic Keratitis — Herpes Simplex Virus
  • African Eye Worm — Loa Loa
  • Mango Fly — Loa Loa
  • Calabar Swelling — Loa Loa
  • Black Fly — Onchocerca volvulus
  • River Blindness — Onchocerca (vs. Loa Loa has no skin presentation or blindness)
  • Lizard Skin — Onchocerca — depigmentation of skin
  • Pseudohyphae — Candida albicans
  • Common normal flora fungus — Candida
  • Cotton Candy in eye — Candida albicans Endophthalmitis
  • Painless Loss of Vision — Retinitis
  • Retinitis — CMV and Toxoplasma gondii
  • Ring Enhancing Lesion — Toxoplasma gondii
  • Handling Cat Feces during pregnancy — toxoplasma gondii
  • Sporozoan in Cats — Toxoplasma gondii
  • β-Hemolytic — Staph aureus, Strep pyogenes, B. cereus