Nachweis von Salmonella spp. bei Landschildkröten
In the present study an efficient procedure for detecting salmonellas in feces of tortoises should be established. First of all a survey of occurrence of salmonellas in reptiles and their importance for reptiles as well as for man is given. Next an appropriate incubation temperature for multiplying salmonellas of reptilian origin in a selective enrichment medium was evaluated. Furthermore 86 salmonella strains isolated from reptiles were tested on nine different selec-tive solid media for their appearance; these media were BPLS-, DCLS-, HE-, MLCB-, ÖNÖZ-, RAMBACH-, SS-, WS- and XLD-Agar. The media were reviewed according to their qualification in identifying those strains. Finally 167 fecal samples of tortoises of different species and two lizards from Munich area were examined according to the former established procedure whether or not they harboured salmonellas. Therewith the suitability of this method should be determined and the incidence of salmonellas of these tortoises should be investigated. Following results were obtained: The best growth of salmonellas resulted from RAPPAPORT-VASSILIADIS and selenite cystine enrichment broth at an incubation temperature of 35-37 °C. The higher critical temperature for incubation of RAPPAPORT-VASSILIADIS enrichment medium is 42 °C; especially Salmonella subspecies IIIb often are inhibited in this medium at this temperature. For isolating salmonellae as well as for inhibiting competing organisms, an incubation temperature of 41 °C is emphasized for enrichment in RAPPAPORT-VASSILIADIS broth. Neither temperature investigated had any inhibitory effect on the growth rate of salmonellas in selenite cystine medium, but its inhibitory activity on competing organisms proved strik-ingly less, too. RAPPAPORT´s enrichment medium supports growing of salmonellas of reptilian origin least of all. For isolation of salmonellas from tortoises BPLS- and XLD-agar proved best for direct strik-ing as well as after previous enrichment in either RAPPAPORT-VASSILIADIS or selenite cystine medium or both. For investigation of snakes and lizards MLCB- or eventually WS-agar should be used. For achieving a most reliable statement at least two different agar media should be used for direct plating as well as for enrichment subculture. RAPPAPORT-VASSILIADIS and se-lenite cystine enrichment medium should be used simultaneously and spread on at least twice at different times of incubation. On account of the intermittent excretion of salmonellas sev-eral fecal samples should be examined. The more extended the effort the better the results will be. Though a single negative result never is absolutely reliable. In this study the incidence of salmonellas in tortoises – investigating only a single sample from each animal – ranks at about 10 %. Two out of 18 tortoises positive for salmonellas originated from different private owners; the remaining 16 belonged to two stocks of a pet shop. Therefore statements about higher incidence of wild cut or home bred tortoises were not practicable.
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