ALKALINE PEPTONE WATER

 

o:p>A tran­sport and enrichment medium for Vibrio spp.

 

Code: CB1/3321

 

Typical formula g/l

 

Tryptone	10.0
Sodium chloride	10.0

 

Final pH 8.5 +/- 0.2

 

Directions

Suspend 20g in 1000 ml of cold distilled water, heat to dissolve, distribute and sterilise by autoclaving at 121^°C for 15 minutes. 

_{Description and in use technique}

_{Alkaline Peptone Water is recommended by OMS, APHA and FDA as a tran­sport and enrichment medium for Vibrio spp.} 

 

_{Generally the test sample is prepared by mixing 25 (or 50) g of sample with 225 (or 450) ml of Alkaline Peptone Water. The inoculated flasks are incubated at 37°C and plated on TCBS Agar after 6-8 hours and 16-24 hours of incubation. The final verification of characteristic colonies cultivated onto TCBS Agar may be performed according to the criteria given by the quoted literature. The differentiation between V.cholerae, V.parahaemolyticus, V.vulnificus and V. alginolyticus is obtained with the following test: Gram staining, motility, Oxidase test, OF test, Growth at 42°C, inhibition by O/129, reduction of nitrate to nitrite, arginine dehydrolase, lysine decarboxylase, ONPG, acid/gas from glucose, sucrose, cellobiose, halophytic characteristics. The so called 'cholera red reaction" (red colouration due to ni­trose - indole formation following to addition of a few drops of con­centrated sulphuric acid) may be tested on Alkaline Peptone Water culture after incubation at 37°C for 24 hours.  However, the test has a poor diagnostic value because a few non-pathogenic vibrios and, generally all the indole producing and ni­trate reducing organisms also give a positive reaction. A microscopic examination in dark field (X400) that permits to obser­ve the rapid and typical arrow mobility of vibrios is more useful for an early diagnosis. The appearance of the microscopic field was compared to that of a summer sky with shooting stars. The microscopic diagnosis can be confirmed by Benenson tech­nique, based on the specific inhibition of  Vibrio motility by O-group polyvalent antiserum.}

 

_{User quality assurance   (37°C-24 h)}

_{Productivity control}

_{V.cholerae NCTC 11218: growth}

_{Selectivity control}

_{E.coli ATCC 25922 : partially inhibited}

_Storage

_{Dehydrated medium: 15-30°C}

_{User prepared tubes: 1 month at 2-8°C}

_References  

_{APHA (1985) - Standard Methods for the Examination of Water and Wastewater, 16th ed.}

_{Benenson, A.S., Islam, M.R. & Greenough, W.B. (1964Bull, WHO, 30, 827.}

_{NMKL method n° 156, 2^nd ed. 1997.}