Journal of Hygiene

Research Article

The occurrence of salmonellas and lactose-negative Arizonas in reptiles in The Netherlands, and a comparison of three enrichment methods used in their isolation

J. P. Koopmana1 and F. G. J. Janssena1

a1 Central Animal Laboratory, Catholic University of Nijmegen, The Netherlands


A survey was conducted in 1971 in healthy reptiles supplied to the Central Animal Laboratory of Nijmegen for experimental animal research. In order to determine which salmonella serotypes occur, and whether there are several serotypes per animal, several strains of each positive sample were typed.

It was found that 160 of 169 samples contained salmonellas or lactose-negative Arizonas or both, and 95 different serotypes were isolated.

Of 127 animals examined individually, 67 were carriers of more than one sero-type, 42 animals having two types, 21 three types and 4 animals four types.

Three enrichment methods were compared. These were tetrathionate broth incubated at 37° C. (T37) and at 43° C. (T43), and selenite broth incubated at 37° C. (SB). All were incubated for 48 hr. before subculture on brilliant-green agar plates. The enrichment methods T37, T43 and SB produced 99, 125 and 123 positive samples respectively, when taken separately. The combinations of T 37 and T43, T37 and SB, and T43 and SB produced 145, 142 and 150 positive samples respectively.

The yield of serotypes in comparable samples showed no difference between the three enrichment methods. With the use of two methods the yield increased by about 38 % compared with one method, and the combination of three methods showed an increase in serotype yield of about 64 % compared with one method. A distinct preference by serotypes for definite enrichment methods was not proved.

(Received October 11 1972)