cholera

Question 1

Vibrio cholerae: basic ID features?

Answer 1

Curved motile gram-negative bacillus; oxidase-positive facultative anaerobe; highly motile with a unipolar sheathed flagellum. :contentReference[oaicite:0]{index=0}

Question 2

How many V. cholerae serogroups exist and what defines them?

Answer 2

> 200 serogroups, defined by differences in the O-specific polysaccharide (OSP) chains of LPS. :contentReference[oaicite:1]{index=1}

Question 3

Which V. cholerae serogroups cause epidemic cholera?

Answer 3

O1 and O139 cause epidemic cholera. :contentReference[oaicite:2]{index=2}

Question 4

Non-O1/non-O139 V. cholerae causes what?

Answer 4

Usually isolated gastroenteritis outbreaks (not large epidemics). :contentReference[oaicite:3]{index=3}

Question 5

V. cholerae O1: main serotypes?

Answer 5

Inaba and Ogawa (serotype switching during epidemics is documented). :contentReference[oaicite:4]{index=4}

Question 6

Which biotype causes the current (7th) cholera pandemic?

Answer 6

El Tor biotype (O1). :contentReference[oaicite:5]{index=5}

Question 7

V. cholerae genome structure?

Answer 7

Multipartite (2 circular chromosomes): large ~3 Mb (essential + pathogenicity genes) and small ~1 Mb (many unknown-function genes). :contentReference[oaicite:6]{index=6}

Question 8

Key role of lateral gene transfer in V. cholerae virulence?

Answer 8

Cholera toxin genes (ctxA/ctxB) are carried by a bacteriophage (CTXΦ) that integrated into a nontoxigenic precursor. :contentReference[oaicite:7]{index=7}

Question 9

Natural reservoir/where can V. cholerae persist outside humans?

Answer 9

Brackish estuaries/coastal seawaters (often with copepods/zooplankton); can thrive in warm, lower-salinity water with organic material. :contentReference[oaicite:8]{index=8}

Question 10

Main transmission route for cholera?

Answer 10

Ingestion of contaminated water/food (fecal–oral); can also be direct fecal–oral between individuals. :contentReference[oaicite:9]{index=9}

Question 11

How infectious is cholera stool output (shedding)?

Answer 11

Rice-water stool can be enormous (up to ~20 L/day) and may contain ~10^9 V. cholerae cells/mL. :contentReference[oaicite:10]{index=10}

Question 12

Infectious dose: high or low?

Answer 12

Generally high infectious dose; lower stomach acid (hypochlorhydria) lowers the infectious dose. :contentReference[oaicite:11]{index=11}

Question 13

What is TCP and why is it important?

Answer 13

Toxin-coregulated pilus (TCP) is critical for small-intestine colonization: microcolonies, protection from intestinal factors, and attachment to epithelium. :contentReference[oaicite:12]{index=12}

Question 14

tcpA encodes what?

Answer 14

The major subunit of TCP. :contentReference[oaicite:13]{index=13}

Question 15

What is the TCP pathogenicity island size (approx)?

Answer 15

~41 kb pathogenicity island acquired via horizontal gene transfer. :contentReference[oaicite:14]{index=14}

Question 16

Cholera toxin (CT): what does subunit B bind?

Answer 16

GM1 ganglioside on epithelial cell surfaces. :contentReference[oaicite:15]{index=15}

Question 17

CT mechanism (core steps)?

Answer 17

CTB binds GM1 → retrograde trafficking → CTA ADP-ribosylates G protein → ↑cAMP → ↑Cl− secretion by crypt cells + ↓absorption by villous cells → water into lumen → secretory diarrhea. :contentReference[oaicite:16]{index=16}

Question 18

Is CT alone sufficient to cause cholera-like diarrhea?

Answer 18

Yes—purified CT can induce cholera-like diarrhea in volunteers (microgram quantities). :contentReference[oaicite:17]{index=17}

Question 19

What is CTXΦ and what’s its receptor?

Answer 19

CTXΦ is the filamentous bacteriophage carrying ctxA/ctxB; it uses TCP as its receptor (precursor was TCP+ ctxAB−). :contentReference[oaicite:18]{index=18}

Question 20

Classic vs El Tor severity?

Answer 20

Classic biotype tends to cause more severe disease than El Tor; El Tor variants expressing classic-type CT may be more severe. :contentReference[oaicite:19]{index=19}

Question 21

Classic clinical picture of cholera?

Answer 21

Acute watery diarrhea that can become massive; vomiting common; progresses to “rice-water stool” (watery with white mucus flecks, fishy odor). :contentReference[oaicite:20]{index=20}

Question 22

How fast can cholera kill (why)?

Answer 22

Can cause death within hours due to severe dehydration and circulatory collapse. :contentReference[oaicite:21]{index=21}

Question 23

Severe cholera stool volume threshold?

Answer 23

Severe cholera can exceed >1 L/hour watery diarrhea. :contentReference[oaicite:22]{index=22}

Question 24

Fever in cholera?

Answer 24

Usually afebrile; may be hypothermic due to severe dehydration. :contentReference[oaicite:23]{index=23}

Question 25

Major host risk factors for severe cholera?

Answer 25

Blood group O; hypochlorhydria (low gastric acid). :contentReference[oaicite:24]{index=24}

Question 26

When should you suspect cholera clinically?

Answer 26

≥5 years with severe dehydration or death from acute watery diarrhea; also ≥2 years with acute watery diarrhea in cholera-endemic regions. :contentReference[oaicite:25]{index=25}

Question 27

Best selective media mentioned for V. cholerae isolation?

Answer 27

Thiosulfate citrate bile sucrose (TCBS) agar; also taurocholate tellurite gelatin agar; enrichment with alkaline peptone water improves recovery. :contentReference[oaicite:26]{index=26}

Question 28

Rapid microscopy clue for vibrios?

Answer 28

Darkfield microscopy shows “shooting star” motility, inhibited by specific antibodies. :contentReference[oaicite:27]{index=27}

Question 29

Cornerstone of cholera treatment?

Answer 29

Rapid assessment and aggressive fluid replacement (restore euvolemia and match ongoing losses). :contentReference[oaicite:28]{index=28}

Question 30

Severe dehydration definition and initial fluid target?

Answer 30

>10% deficit; typically >100 mL/kg IV within 3 hours (6 hours if <1 year), plus match ongoing losses (often 10–20 mL/kg/h). :contentReference[oaicite:29]{index=29}

Question 31

Preferred IV fluid for severe cholera?

Answer 31

Lactated Ringer’s solution (often with 5% dextrose); if unavailable, normal saline + dextrose. :contentReference[oaicite:30]{index=30}

Question 32

When switch from IV to ORS?

Answer 32

When mentally alert, often within 3–6 hours. :contentReference[oaicite:31]{index=31}

Question 33

ORS principle (why it works)?

Answer 33

Equimolar sodium + glucose maximizes absorption; WHO low-osmolarity ORS helps avoid hypernatremia. :contentReference[oaicite:32]{index=32}

Question 34

Home-made ORS recipe in notes?

Answer 34

1 L safe water + 12 tsp table salt + 6 tsp table sugar (and add potassium sources like coconut milk/bananas/orange juice). :contentReference[oaicite:33]{index=33}

Question 35

Role of antibiotics in cholera?

Answer 35

Secondary to fluids; give for moderate–severe dehydration—can reduce diarrhea volume ~50% and shorten duration; choose based on local resistance (often azithromycin or fluoroquinolone). :contentReference[oaicite:34]{index=34}

Question 36

What should be avoided in cholera (medication-wise)?

Answer 36

Antimotility agents (can cause misleading “improvement” and complications). :contentReference[oaicite:35]{index=35}

Question 37

With proper care, mortality in patients who reach care is about?

Answer 37

<1%. :contentReference[oaicite:36]{index=36}

Question 38

Oral killed cholera vaccines (examples)?

Answer 38

Dukoral, Shanchol, Euvichol (WHO-approved; O1/O139 coverage varies by product). :contentReference[oaicite:37]{index=37}

Question 39

Typical efficacy/duration of oral killed cholera vaccines?

Answer 39

~60–80% efficacy for ~6–60 months (varies by vaccine and age). :contentReference[oaicite:38]{index=38}

Question 40

US live attenuated oral cholera vaccine and protection?

Answer 40

Vaxchora (CVD 103 HgR): ~90% protection within ~10 days and ~80% at 90 days. :contentReference[oaicite:39]{index=39}

Question 41

How hard is cholera eradication and why?

Answer 41

Hard due to environmental reservoir; long-term control relies on safe water and sanitation. :contentReference[oaicite:40]{index=40}

Question 42

Main immunologic correlate used for protection?

Answer 42

Vibriocidal antibody response (complement-dependent bactericidal antibodies, often IgM against LPS/OSP). :contentReference[oaicite:41]{index=41}

Question 43

Protective immunity is mainly what type?

Answer 43

Largely serogroup-specific and toxin-independent, determined by OSP of LPS. :contentReference[oaicite:42]{index=42}