This is a series of lectures on microbiology, useful for both undergraduate and post graduate medical and paramedical students... This lecture covers cholera, typhoid, diarrhoea and dysentry
2. Overview
• Most infections of the g.i.t. are acquired through
contaminated food – food poisoning
• Food infection –
− Bacteria like - Cholera, E. coli, Salmonella,
shigella,
− viruses like enterovirus, rotavirus, hepatitis A
and E
− Parasites like G. lamblia
• Food intoxication – S. aureus, B. cereus, Cl.
Perfringens, Cl. botulinum
4. Factors responsible for spread
• Age – children more susceptible
• Personal hygiene
• Open air defecation
• Food at road side stalls
• Uncovered food
19. Resistance
• Resistant to cold – refrigerated food may
carry vibrio
• Donot survive at room temperature /
heating
• Susceptible to common drugs like
doxycycline
21. Cholera
• Acute diarrhoeal illness
• Painless ‘rice water’ stools
• Copius vomitting
• Fluid loss and dehydration
22.
23. • Due to two toxins released by bacteria in
intestine
• Toxin A and B
• Cause pouring of water from body into
intestines
• Extensive water depletion
25. Epidemiology
• Source – infected humans
• Mode of transmission – contaminated
water/food
• Cholera spreads as sporadic/epidemic or
pandemic forms
• Large movement of people such as during
fairs/festivals is associated with cholera
spread
28. Pandemic
• Cases seen over a long period of time
over continents
• Till 19th century, cholera was mainly
confined to India – mainly area of Ganga
plains – Bengal
• Total seven pandemics have been
identified.
36. Treatment
• More important is replacement of lost
fluid
• Antibiotics are of secondary importance
• Doxycycline
37. Enterobacteria
• Flora of large intestine
• Classified on basis of growth on Mac
Conkey’s medium
− Lactose fermenters – E. coli, Klebsiella
− Late lactose fermenters – shigella
− Non lactose fermenters - Salmonella
38.
39. Diarrhoea causing E. Coli
ETEC
Toxin causes release
of water into
intestinal lumen
Watery diarrhoea
EIEC
Invade intestinal wall
Dysentry
Entero invasive E Coli
Blood and mucous in
stools
EHEC
Does not invade
Bloody diarrhoea
Entero hemorrhagic
Toxin release
Colitis
Entero toxicogenic
E Coli
EPEC
Entero pathogenic
Infant watery
diarrhoea
45. Growth characteristics
• Colorless colonies on Mac conkey – Non
lactose fermenters
• Jet black colonies on Wilson and Blair due
to production of H2S
51. Clinical course
• Gradual onset with fever, abdominal pain
and constipation/diarrhoea
• Step ladder fever with bradycardia
• Spleen and liver are enarged
• Rose spots on skin in second week
60. Prophylaxis
• Best is improved sanitation
• Live oral vaccine – typhoral
• Injectable vaccine – typhim vi
• Protection lasts 3 years, booster required
afterwards
61. Shigella – BACILLARY DYSENTRY
• DYSENTRY – bacillary (shigella) and
amebic (parasitic)
• Also caused by EIEC, Campylobacter
62. • Gram negative rods
• Lactose non fermenters on Mac conkey
• Classified according to mannitol
fermentation
− Sh dysenteriae – mannitol non fermenter
− Sh flexneri, sh bodydii and sh sonnei –
mannitol fermeters
63. Bacillary dysentry
• Bacilli infect intestinal epithelial cells
• Spread to submucosa
• Inflammatory reaction with capillary
thrombosis
• Sloughing and necrosis of mucosa
• Ulcers
Notas do Editor
Age; EPEC and rotovirus tend you affect young children
Hygiene: fecooral
Acidity: protective barrier, low inoculm
Motility: expel the pathogens. Antimotility assoc with prolonged fever shedding shigella, complication c diff, HUS in ETEC
Flora: ex cdiff