DISTINGUISHING
PATHOGENIC
ORGANISMS
Pathogenic organisms can be
macroscopic or microscopic
 Macroscopic organisms: can be seen with the
unaided eye
 Microorganisms: cannot be seen with the naked
eye
 Pathogens: any organism that causes a disease
 Most pathogenic organisms are microscopic or
just barely visible to the unaided eye
 Microscopic organisms include:
–
–
–
–
Bacteria
Viruses
Fungus
Parasites
Bacteria
– Cocci: spherical-shaped
• (ex: Streptococcus)
– Bacilli: rod-shaped
• (ex: Clostridium)
– Spirilli: spiral-shaped
• (ex: Treponema)
Virus
– Can be seen with an electron microscope
– Contain DNA or RNA
– Use the host cell to replicate
– Examples:
• Hepatitis
• Human papillomavirus (wart virus)
• Hantavirus (Korean hemorrhagic fever virus)
Fungi (Mycology)
– Microscopic
– Approximately 100 species are human
pathogens
– Infects humans by inhalation or
inoculation
– Examples:
• Yeast-Candida albicans
• Dermatophytes-Tinea capitis
– ringworm of the scalp
Macroscopic Organisms
 Parasite examples:
– Cestodes: Pork tapeworm
• Ex: Taenia solium
– Nematodes: Pinworm
• Ex: Enterobius vermicularis
– Trematodes: Intestinal flukes
• Ex: Clonorchis sinensis