A conductance medium to distinguish between Salmonella and Citrobacter spp.
Published methods for detecting Salmonella by conductance methods yield some Citrobacter spp. as false positives. A medium is described which, when used in conjunction with selenite-cystine/trimethylamine oxide/mannitol (SC/T/M) resolves this difficulty. It is based on the ability of Salmonella to decarboxylate lysine in the presence of selenite (4 g/l), after pre-enrichment in buffered peptone water supplemented with glucose and lysine for 7-17 h. Salmonella produced a conductance change of 250-400 microS in 24 h with a maximum rate of conductance change of 10-15 microS/10 min. 299 samples were tested and the only false positives were due to Hafnia alvei which gave no conductance response in the SC/T/M medium. Using both media in a two tube system would lead to a rapid clearance of Salmonella negative samples.
Ogden
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Torry Research Station, Ministry of Agriculture, Fisheries and Food, Aberdeen, U.K.
D000818:Animals; D002262:Carboxy-Lyases; D002417:Cattle; D002954:Citrobacter / Q000302:isolation & purification*; D003217:Conductometry; D003470:Culture Media; D005189:False Positive Reactions; D007700:Kinetics; D008239:Lysine; D008460:Meat; D010710:Phosphates; D011730:Pyridoxal; D012475:Salmonella / Q000302:isolation & purification*
D003470:Culture Media; D010710:Phosphates; D011730:Pyridoxal; D002262:Carboxy-Lyases; D008239:Lysine; C018279:sodium phosphate