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

Classification of major Gram-Positive cocci

Catalase Positive in tubes	Coagulase Positive in tubes			Coagulase Negative in tubes
	Staphylococcus aureus			Staphylococcus epidermidis Staphylococcus saprophyticus
Catalase Negative in tubes	α hemolytic (partial hemolysis) on media		β hemolytic (complete hemolysis) on media		γ hemolytic (no hemolysis) on media
	Streptococcus pneumoniae Streptococcus suis viridans Streptococcus		Group A (beta) streptococci (Streptococcus pyogenes) Group B (beta) streptococci (Streptococcus agalactae) Group C (beta) streptococci Group G (beta) streptococci		Streptococcus bovis Enterococcus faecium Enterococcus faecalis

Classification of major Gram-Positive bacilli

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

Classification of major Gram-Negative cocci

Classification of major Gram-Negative bacili

Lactose fermenting	Escherichia coli Klebsiella pneumoniae
Non-lactose fermenting	Shigella spp. Salmonella spp. Yersinia pestis
Non-fermenting	Pseudomonas aeruginosa Burkholderia pseudomallei

Protozoa

-> Overview_of_protozoa