Painless diarrhoea occurs with
Ans. d (V. cholerae). (Ref. Harrison's Internal Medicine 17th ed. Chapter 149).CHOLERA - Pathogenesis# Cholera toxin, which consists of a monomeric enzymatic moiety (the A subunit) and a pentameric binding moiety (the B subunit). The B pentamer binds to GM1 ganglioside, a glycolipid on the surface of epithelial cells that serves as the toxin receptor and makes possible the delivery of the A subunit to its cytosolic target. The activated A subunit (Al) irreversibly transfers ADP-ribose from nicotinamide adenine dinucleotide to its specific target protein, the GTP- binding regulatory component of adenylate cyclase. The ADP-ribosylated G protein upregulates the activity of adenylate cyclase; the result is the intracellular accumulation of high levels of cyclic AMP.# In intestinal epithelial cells, cyclic AMP inhibits the absorptive sodium transport system in villus cells and activates the secretory chloride transport system in crypt cells, and these events lead to the accumulation of sodium chloride in the intestinal lumen.# Since water moves passively to maintain osmolality, isotonic fluid accumulates in the lumen. When the volume of that fluid exceeds the capacity of the rest of the gut to resorb it, watery diarrhea results.Clinical features# After a 24- to 48-h incubation period, cholera begins with the sudden onset of painless watery diarrhea that may quickly become voluminous and is often followed shortly by vomiting.# Fever usually absent.# Acidosis can occur.# Characteristic appearance of stool: cloudy fluid with flakes of mucus, and no blood.# Clinical symptoms parallel volume contraction:- At losses of 3-5% of normal body weight, thirst develops;- at 5-8%, postural hypotension, weakness, tachycardia, and decreased skin turgor are documented; and- at >10%, oliguria, weak or absent pulses, sunken eyes (and, in infants, sunken fontanelles), wrinkled ("washerwoman") skin, somnolence, and coma are characteristic.Diagnosis:# Useful in culture and transport:- TcBC agar,- Cary Blair medium OR alkaline-peptone water-enrichment medium*Rx# Only the rapid and adequate replacement of fluids, electrolytes, and base is required.# Rice-based ORS is considered superior to standard ORS in the treatment of cholera.# For initial management of severely dehydrated patients, IV fluid replacement is preferable. Because profound acidosis (pH < 7.2) is common in this group, Ringer's lactate is the best choice.# Although not necessary for cure, the use of Single-dose tetracycline (2 g) or doxycycline (300 mg) is effective in adults but is not recommended for children <8 years of age.# For Children, furazolidone has been the recommended agent and trimethoprim-sulfamethoxazole 2nd choice.# Due to cost and toxicity issues related to other drugs, erythromycin is good choice for pediatric cholera.
Salmonella
Shigella
C. jejuni
V. cholerae
Vibrio