A comparative study of unpassaged and animal passaged cultures of Listeria monocytogenes in rabbits.
Variants of a parent culture of Listeria monocytogenes were prepared by passaging it several times through rabbits. The resulting isolates (V1 to V6) were investigated and compared with the parent culture with particular emphasis on their phenotypic characters and their pathogenicity for rabbits. The variants maintained the morphological, cultural, biochemical and serological features of the parent strain. Although no significant decrease was noted in the total extracellular protein produced, 10 mg/ml of a 6-day culture broth grown at 34 degrees C for V6 as compared to 12.3 mg/ml for the parent culture, the phosphocholine-specific phospholipase C (PC-PLC) activity diminished with passaging. Pathogenicity for rabbits, as determined by viable count of the organism per gram of the infected organ, increased at each passage. Animals infected with V6 revealed a mean of 2.2 x 10(9) CFU/g of spleen as compared to the parent culture which had a count of 5.0 x 10(6) CFU/g. These observations indicate a lack of direct correlation between in vitro production of PC-PLC and virulence of L. monocytogenes for rabbits.
Vahidy
R
R
Department of Microbiology, University of Karachi, Pakistan.
Waseem
M
M
Khalid
S M
SM
D000818:Animals; D015169:Colony Count, Microbial; D003470:Culture Media; D008089:Listeria monocytogenes / Q000201:enzymology / Q000254:growth & development / Q000472:pathogenicity*; D011817:Rabbits; D010738:Type C Phospholipases / Q000378:metabolism*; D014774:Virulence
D003470:Culture Media; D010738:Type C Phospholipases