| Popis: |
Numbers of viable bacteria in second instar Culex pipiens quinquefasciatus larvae were determined following ingestion of pathogenic strain SSII-1 and nonpathogenic Bacillus sphaericus . Numbers of nonpathogenic B. sphaericus recovered from larvae declined rapidly after cessation of feeding, as did numbers of pathogenic SSII-1 cells fed at LD 20 dosage. When pathogenic cells were fed at LD 70 dosage, the number of B. sphaericus in larvae increased following initial decline. When chloroformtreated SSII-1 cultures, in which all bacteria except spores were dead, were fed at LD 10 and LD 98 dosages, no viable B. sphaericus were recovered from larvae. In all SSII-1 treatments, other bacterial flora multiplied rapidly in larvae following onset of mortality; the role of this multiplication in the pathogenesis was not determined. It is proposed that toxic material is released when SSII-1 cells are digested and that multiplication of B. sphaericus in the larval gut is not essential in the pathogenesis. There appears to be no difference in the pathogenesis when differing numbers of B. sphaericus . i.e., LD 10–20 or LD 70–98 dosages, are ingested. Possible nature of the toxic material is discussed. |
