Keys for Tropical Medicine 1

Overview of Tropical Medicine

Definition of the tropics

• Between the Tropic of Cancer (north latitude 23°26′) and the Tropic of Capricorn (south latitude 23°26′)
• Covers 40% of land surfaces and 40% of population

Top 3 causes of death in LMICs, HICs and worldwide in 2016

*Bold names are communicable diseases

Worldwide	LMICs	HICs
Ischemic heart disease Stroke Chronic obstructive pulmonary disease (COPD)	Lower respiratory infections Diarrhea Ischemic heart disease	Ischemic heart disease Stroke Alzheimer and other dementias

Changes of top 10 causes of death worldwide from 2010 to 2016

• Tuberculosis ranked down to the 10th in 2016 from the 6th in 2010
• HIV/AIDS ranked down out of 10 in 2016 from the 7th in 2010

List Neglected Tropical Diseases (NTDs) and what are not listed as NTDs

• List of NTDs by WHO

Virus	Dengue & Chikungunya (dengue virus, chikungunya virus) Rabies (rabies virus)
Bacteria	Buruli ulcer (Mycobacterium ulcerans) Leprosy (Mycobacterium leprosy) Trachoma (Chlamydia trachomatis) Yaws (Treponema pallidum pertenue)
Protozoa	Chagas disease, American trypanosomiasis (Trypanosoma cruzi) Human African trypanosomyasis, Sleeping sickness (Trypanosoma brucei spp.) Leishmaniasis (cutaneous and visceral) (Leishmania spp.)
Parasites - Nematodes	Dracunculiasis, Guinea worm (Dracunculus medinensis) Lymphatic filariasis (Wuchereria bancrofti, Brugia malayi) Onchocerciasis (Onchocerca volvulus) Soil-transmitted helminth infections
Parasites - Trematodes	Foodborne trematode infections Schistosomiasis (Schistosoma spp.)
Parasites - Cestodes	Echinococcosis (Echinococcus granulosus, E. multilocularis) Taeniasis/Cysticercosis (Taenia spp.)
Ectoarasites	Scabies, Tungiasis & other ectoparasites (mite, sandflea, etc.)
Fungi	Mycetoma, Chromoblastomycosis (chromomycosis) & other deep mycoses (various spp.)
Non-communicable	Snakebites

• These are NOT listed as NTDs
  • HIV/AIDS
  • Tuberculosis
  • Malaria
  • Lower respiratory infections
  • Diarrhea

Bacteria

Biological basis of Gram staining

• Bacteria have both of cell wall and cell membrane
  • Human and other animal cells have no cell wall
  • Plant cells have cell wall
• Some bacteria have thick cell wall without outer membrane
• Other bacteria have thin cell wall with outer membrane
• Cell wall contains a layer of Peptidoglycan

• Thick peptidoglycan layer catches and keep crystal violet with iodine
• Outer membrane catches crystal violet with iodine but easily lose them by ethanol rinsing

Classify major Gram-Positive cocci

There are so many species of gram-positive cocci.

• Catalase positive in tubes
  • Staphylococcus spp.
    • Coagulase positive in tubes
      • Staphylococcus aureus
    • Coagulase negative in tubes
      • Staphylococcus epidermidis
      • Staphylococcus saprophyticus
• Catalase negative in tubes
  • Streptococcus spp.
    • Alpha-hemolytic (partial hemolysis with green color)
      • Streptococcus pneumoniae
      • Streptococcus suis
      • viridans Streptococcus
    • Beta-hemolytic (complete hemolysis)
      • Group A (beta) streptococci (Streptococcus pyogenes)
      • Group B (beta) streptococci (Streptococcus agalactae)
      • Group C (beta) streptococci
      • Group G (beta) streptococci
    • Gamma-hemolytic (no hemolysis)
      • Streptococcus bovis
      • Enterococcus faecium
      • Enterococcus faecalis

Classify major Gram-Positive bacilli

Smaller number of bacilli show gram-positive.

• Spore forming
  • Aerobic
    • Bacillus anthracis
    • Bacillus cereus
  • Anaerobic
    • Clostridium tetani
    • Clostridium perfringens
• Non-spore forming
  • Aerobic
    • Corynebacterium diphtheria
  • Anaerobic
    • Listeria monocytogenes