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MICROBIOLOGY

Aerobic, gram negative, comma-shaped bacillus.

霍亂弧菌，格蘭氏陰性菌

Water-borne pathogen, humans acquire infection through ingesting contaminated water or food. 

V cholerae serogroup O1, biotype El Tor, originated in Asia but has caused pandemic infection throughout Africa and South America for ~40 yrs.

Newer serogroup, O139 described in SE Asia in 1992 now endemic.

Isolates described with resistance to ampicillin, tetracycline,ampicillin, aminoglycosides, sulphonamides, and trimethoprim.

CLINICAL

Cause of the secretory diarrheal syndrome, cholera.

Epidemic and endemic cause of massive diarrhea.

Most commonly found in Africa, South America, south and east Asia, eastern Europe.

Usually a non-invasive organism that causes diarrhea by elaboration of a toxin.

Along U.S. Gulf coast, transmission occurs but is rare, sporadic.

Incubation time usually 18-40 hrs, followed by nausea, abdominal rumbling followed by the onset of massive, watery diarrhea.

Most infections mild-moderate, ~1 in 20 develop severe disease.

Morbidity and mortality due to dehydration so severe as to elicit hypotension, shock and multi-organ failure. Many deaths occur within the first day.

Dx: stool cx, biochemical ID on isolate; specialized laboratories can diagnose by serological techniques, PCR.

Rarely a cause of skin/soft tissue infection, bacteremia, disseminated infections, which are usually caused by non-cholerae 

SITES OF INFECTION

Small intestine: cholera toxin induces secretion of Na and  bicarbonate-rich non-inflammatory fluid, so-called "rice water" stools.

Skin/soft tissue (rare): non-epidemic strains of V. cholerae.

TREATMENT治療方式

Fluid Replacement (Priority)主要是體液補充

Rapid replacement of water and electrolyte deficits, major goal to avoid mortality.

Maintenance fluids to replace ongoing measured losses.

IV replacement until oral hydration therapy can keep up with losses.

Severely dehydrated pts should have 10% of bodyweight repleted within 2-4h.

IV replacement fluid: Ringer's lactate with extra K+.

If unavailable, normal saline may be used but avoid dextrose water solutions as not with sufficient electrolyte characteristics to compensate for loses.

Oral rehydration solutions (ORS): use commercially prepared if available. To prepare, for 1L purest available water, add 2.6 g sodium chloride, 2.9 g trisodium citrate, 1.5 g potassium chloride, and 13.5 g glucose (or 50g boiled and cooled rice powder).

A rice-based ORS solution, in combination with tetracycline, is effective but not as good as a glucose-based ORS.

光是使用體液補充並無法消除霍亂弧菌，所以目前醫學會併用抗生素

Antibiotics抗生素

Reduces diarrhea duration, volume. Selection should be guided by knowledge of local susceptibility pattern of V. cholerae in circulation.

Administer antibiotic as soon as vomiting ceases.

Tetracycline 500 PO four times daily.

Doxycycline 100 mg PO twice daily.

Azithromycin 1000 mg PO x 1 dose.

Erythromycin 250 mg PO four times daily x 5 d.

TMP/SMX 160mg/800mg (DS) PO twice daily.

Ampicillin 500 mg PO four times daily.

Ciprofloxacin 250 mg PO once to twice daily.

Duration of antibiotic 1-3 days.

抗生素的使用建議：

Ampicillin 

Effective in general, but antibiotic resistance emerging.

 Trimethoprim + Sulfamethoxazole

Effective but resistance to this antibiotic emerging. Should be avoided where serovar O139 is known to be prevalent.

Azithromycin 

Probably the drug of choice in the adjunct antimicrobial treatment of cholera, in addition to oral rehydration therapy.

Ciprofloxacin 

Effective, but more expensive in developing world setting. Can be given in single dose (such as 1 g po to adults) during epidemics in developing countries; sometimes multiple doses needed in regions where resistance may be encountered due to higher minimal inhibitory concentrations of emerging resistant organisms (e.g., India).

Doxycycline 

Effective in general but antibiotic resistance emerging. Experts say that tetracyclines given to children with cholera in short courses "precludes staining of teeth and other adverse reactions encountered with long courses."

Oral rehydration solution 

The most important management of cholera.

Tetracycline 

Effective in general but antibiotic resistance growing. Experts say that tetracyclines given to children with cholera in short courses "precludes staining of teeth and other adverse reactions encountered with long courses."

FOLLOW UP

Without treatment, case-fatality rate is 50%.

As soon as able, patients should eat food without restriction.

OTHER INFORMATION

Avoid trimethoprim/sulfamethoxazole if causative agent is V. cholerae serovar O139, due to resistance.

Tetracycline or other abx useful for prophylaxis among close contacts.

Cholera vaccine (Dukoral from SBL Vaccines) not available in the U.S. (low efficacy, but improved from prior vaccine).