Microbial Processes Flashcards
What are ‘common source’ diseases?
Diseases come from one source and infect large no.s people simultaneously
What can cause water-borne diseases?
Bacteria - cholera, typhoid etc
Viruses - polio, hep A etc
Protozoa - giardiasis, amoebic dystentery
What causes cholera?
Vibrio cholerae - Gram -ve rod bacteria High infectious dose Attach to small intestinal epithelia Enterotoxin CtxAB causes fluid loss into small intestine Can kill in hours if untreated
What causes typhoid?
Salmonella typhi - Gram -ve rods
Invade Peyer’s patches in small intestine to reach lymph nodes
Multiply in macrophages to reach bloodstream, liver, spleen, gall bladder
High continuous fever, ‘rose spots’ on abdomen
Bacteria may persist in gall bladder leading to carrier state
What causes bacillary dysentery (Shigellosis)?
Shigella dysenteriae - Gram -ve
Small infectious dose
Attach to intestinal epithelium and invade cells
Generally self-limiting in healthy subjects
What causes amoebic dysentery?
Entamoeba histolytica - lobose amoeba without mitochondria
Infectious form - tetranucleate cyst
Excystation in intestine to 8 amebules
May live commensally eating bacteria or become pathogenic attacking mucosa and eating red blood cells
Movement down intestine leads to encystment
Severe ulceration - complications
What is Giardia lamblia?
Most common intestinal parasite in USA
Trophozoite - flagellate with 2 nuclei, 8 flagella, no mitochondria, and a ventral sucker
Infectious form - tetranucleate cyst
Trophoziotes attach to small intestinal epithelia, interfere with normal absorption - fatty diarrhoea
What is Cryptosporidium parvum?
Coccidian parasite that affects the intestinal and respiratory epithelium of vertebrates
Completes life cycle in single host
Infectious form - oocyst, releases 4 sporozoites which enter epithelial cells
What viruses can cause water-borne diseases?
Rotavirus - diarrhoea
Human enteric calicivirus - aka norovirus
Enterovirus - polio, hep A
