Diseases

Question 1

Clostridium difficile

Answer 1

Etiologic agent:

• Gram +, rod shaped
• Flagella, fimbriae
• Vegetative and spore states
• Anaerobic
• Toxin A & Toxin B

Pathophysiology/symptoms

• Toxins → pseudomembranous colitis → pus pockets → diarrhea, colon rupture, death
• Diarrhea 10-15x a day, nausea, weight loss, fever, dehydration

Transmission
-Fecal-oral: touching contaminated surface then touching mouth; mouth, food

Diagnosis

• Stool test: PCR, enzyme immunoassay, cell cytotoxicity assay
• Colonoscopy, X-ray

Prevention and treatment

• Handwashing and sterile techniques
• Antibiotics (vancomycin and metronidazole)
• Surgery (colectomy)
• Fecal microbiota transplant

Question 2

Gonorrhea vs Chlamydia

Answer 2

Etiologic agent

• G: Neisseria gonorrheae; non motile coccoid bacteria
  
  • Obligate intracellular bacterium (lack metabolic pathways)
• C: chlamydia trachomatis; gonococcal pili
  
  • Intracellular aerobic diplococcus
  • Oxidase +
  • Utilizes glucose

Pathophysiology/symptoms

• G: antigenic characteristics
  
  • Antibody resistant genes (penicillin)
  • Susceptibility to host re-infection
• C: epithelial columnar cells
  
  • Biphasic life cycle
  • Prevent phagosome-lysosome fusion & produce reticulate bodies

Transmission

• STD – oral and vaginal
• Vertical transmission: parent → newborn
• In fallopian tubes
• Super infection: chlamydia → gonorrhea

Diagnosis

• Cell cultures
• NAATS – non culture tests that amplify the sequence of nucleic acid (urethral or endourethral)

Prevention and treatment

• Antibiotics (doxycycline, azithromycin, erthyromycin, levoflaxin)
• Condoms and sex ed, STD testing

Question 3

Lyme disease

Answer 3

Etiologic agent

• Borella burgdorferi (bacteria) – spirochetes – very motile (specialized endoflagella)
• Aerobic or microaerobic
• Slow growth, very fastidious

Pathophysiology/symptoms

• Lesions
• Stage 1 early localized – lesions, red rings around bite site; lymph nodes swollen and normal symptoms (nausea, fever, etc)
• Stage 2 early disseminated – bacteria spreads thru blood to inflame tissues
• Stage 3 later/chronic – muscle and joint conditions, neurological, skin conditions

Transmission

• Backlegged deer tick
• Egg → larva → nymph → adult nymph transmits more often
• Humans aren’t only host – become infected by the deer or mice that they feed on

Diagnosis

• Tick exposure and blood tests
• 1. Enzyme-linked immune-sorbent assay (ELISA): reads antibodies; if positive →
• 2. Western blot test: reads antigens; rules out false positives

Prevention and treatment

• Antibiotics – recovery time varies
• 10-15% of patients who take antibiotics experience Jarisch-Herxheimer reaction → presents worse symptoms due to death of bacteria

Question 4

Norwalk Virus

Answer 4

Etiologic agent

• Single positive stranded RNA virus
• Hexagonal capsid, amorphous surface, 32 cup shaped depressions
• Icosahedral symmetry

Pathophysiology/symptoms

• Virus in small intestine → fat malabsorption → enzymatic dysfunction at brush border → leak flux and anion secretion → changes in gastric motility and delayed gastric emptying
• Nausea, vomiting, diarrhea, headaches, fever

Transmission
-Fecal-oral (contaminated vehicles); person to person; airborne

Diagnosis

• Electron microscopy
• ELISA immunoassay
• Nucleic acid amplification

Prevention and treatment

• Wash hands, food, sterile surfaces
• No vaccine, no treatment or medication
• Oral fluid and electrolyte replacement, antiemetics, analgesics, anti peristaltic agents

Question 5

Polio

Answer 5

Etiologic agent

• Picornaviridae (family), enterovirus (genus)
• Single stranded RNA core, surrounded by protein capsid
• Non enveloped, icosahedral

Pathophysiology/symptoms
-Mouth → replicates at pharynx & GI tract → lymphoid tissue → bloodstream → infect cells of CNS → replicate in motor neurons of anterior horn and brain stem → cell destruction → manifestation of polio myelitis

Transmission

• Fecal oral (contaminated food or water, sewage)
• Person to person (droplets)

Diagnosis

• Throat specimen, fecal specimen
• Virus isolation, RT-PCR, partial genome sequencing, serologic testing
• CSF analysis

Prevention and treatment

• Vaccine (IPV or OPV)
• Research and education
• Monitor sewage and water supplies

Question 6

Ebola

Answer 6

Etiologic agent

• Filoviridae (family), ebolavirus (genus)
• Linear strands of RNA
• Caused by 5 distinct viruses: ebola virus, Sudan virus, Tai’ Forest virus, Reston virus, Bundibugyo virus

Pathophysiology/symptoms

• Target immune cells, liver and adrenal glands
• Weakened immune system makes them susceptible to other diseases
• Liver overproduces coagulation proteins in blood → clots
• Adrenal gland raises BP & along w/weakened blood vessels → bleeding and swelling

Transmission

• Bodily fluids (sweat, vomit, urine, semen, mucus, diarrhea, etc)
• Can survive outside the body: several hrs in dry conditions, several days in fluids
• Zoonotic (bats)

Diagnosis
-ELISA, antigen capture detection tests, serum neutralization tests, RT-PCR assay, electron microscopy, virus isolation by cell culture

Prevention and treatment

• Reduce risk of wildlife to human contact
• Animals handled w/protective clothing and gloves

Question 7

Tuberculosis

Answer 7

Etiologic agent

• Mycobacterium tuberculosae
• Non motile, aerobe, acid fast, filamentous, waxy cell wall
• Facultative intracellular parasite
• Slightly curved baccilus

Pathophysiology/symptoms

• Use immune system to form granulomas called tubercles → can be dormant or not → tubercles can enlarge → cause cavities in the lungs → leak bacteria → severe coughing and bloody sputum → granulomas can travel
• Severe coughing, bloody sputum, chest pain, weakness

Transmission
-Person to person (droplets) coughing, sneezing, speaking

Diagnosis

• Clinical: signs, symptoms, history
• Imaging: x ray, CT, MRI
• Skin test, blood test
• Bacteriology: acid fast, culture, PCR

Prevention and treatment

• Vaccination (BCG)
• Meds: take the entire course
• If infected: stay home, ventilate the room, cover mouth, wear mask

Question 8

West Nile Virus

Answer 8

Etiologic agent

• Flaviviridae (family), flavivirus (genus)
• Spherical enveloped single stranded RNA virus
• Nonmotile, no staining
• Receptor mediated endocytosis

Pathophysiology/symptoms

• Bite → infection in keratinocytes → immune cells in epidermis → draining lymph nodes → peripheral organs
• Neuroinvasive mechanisms – disruption of BBB

Transmission

• Primary route: mosquitoes – feed on infected birds → feed on humans or animals → dead end hosts (humans, horses, dogs)
• Alternate routes: thru contact w/other infected animals, their blood or other tissues

Diagnosis
-IgG antibody sero-conversion, IgM antibody capture ELISA, MIA, PRN test, IFA, hemagluttination inhibition, RT-PCR assay, lumbar puncture, brain tests

Prevention and treatment

• Awareness – stay away from places w/a lot of mosquitoes; preventing infection in health care setting
• Treatment: no antiviral or adjunctive therapies approved or recommended

Question 9

Zika virus

Answer 9

Etiologic agent

• Flaviviridae (family), flavivirus (genus)
• Non motile

Pathophysiology/symptoms

• Infects epidermal keratinocytes → skin fibroblasts → Langerhaans cells → thought to continue to the blood stream and lymph nodes
• Swollen lymph nodes on side of neck, joint pain, rash, body aches

Transmission

• Mosquitoes
• Sexual transmission, in utero, blood transfusion

Diagnosis
-Urine sample or blood test

Prevention and treatment

• Nonspecific meds or vaccine
• Rest and acetaminophen
• Sexual protection, bug repellents, avoid bites, postpone travel if pregnant

Question 10

Giardia

Answer 10

Etiologic agent

• Giardia intestinalis
• Trophozoite form: rigid cytoskeleton, posterior flagella, 2 symmetrical nuclei, teardrop shape
• Cyst form: oval, smooth walled

Pathophysiology/symptoms

• Cyst ingested from water/food → exocystation occurs: in presence of acid or pancreatic enzymes → parasite passes into small bowel and multiply rapidly → pass into large bowel → cysts passed back into environment thru fecal matter → cycle repeats
• Diarrhea, gas

Transmission
-Fecal oral (contaminated food and water)

Diagnosis

• Symptoms: diarrhea, gas, abdominal cramps, nausea, weight loss
• Stool samples: identification of trophozoite and cysts in stool must be present

Prevention and treatment

• Good hygiene – avoid consuming contaminated food or water
• Multiple drugs: metronidazole, thinidazole, nitazoxanide

Question 11

Ringworm

Answer 11

Etiologic agent

• Tinea – fungus
• Dermatophyte, produce keratinase
• Dermatophyte cell walls contain mannin which inhibits the body’s immune response

Pathophysiology/symptoms

• Warm moist environments
• Fungus grows down stratum corneum → invades keratin → keratinase enzyme released to invade deeper
• Hair becomes brittle and breaks, skin grows concentrically

Transmission
-Direct and indirect (some from soil, some from object to human, domestic animals, infected human to human)

Diagnosis

• Depends on symptoms and lesion location
• Scraping of lesions, collecting bits of hair, scrapings of underneath nails, specimens treated
• Microscope, Wood’s lamp

Prevention and treatment

• Don’t share towels, shoes or sports gear; wear shower shoes
• Topical fungal agent, ointments (help speed up loss of outer skin layer)

Question 12

Chicken pox

Answer 12

Etiologic agent
-Varicella virus

Pathophysiology/symptoms

• Mucous membranes → host cells in nose surrounding lymph nodes → liver, spleen, sensory nerve tissues → skin cells
• Fever, fatigue, headache, itchiness, redness, blisters

Transmission

• Airborne
• Direct contact

Diagnosis
-Itchiness

Prevention and treatment
-Calamine lotion, colloidal oatmeal baths, short fingernails, no antibiotics, vaccine