Gamaleya Research Institute of Epidemiology and Microbiology, Moscow; All-Russian Research Institute of Veterinary Virology and Microbiology, Moscow, Russia
Aim. To study the progress of infection caused by mutant Listeria monocytogenes with deletion of lmo0028 gene coding L,D-carboxypeptidase (protein involved in metabolism of peptidoglycan). Materials and methods. Deletion of lmo0028 gene was performed with site-specific mutagenesis method using wild-type strain EGDe. Virulence was studied on mice of BALB/c line. Results. Strain GIMd0028 with deletion of lmo0028 gene did not differ from parent strain on in vitro growth rate, cytotoxicity and production of listeriolysin O and phospholipase PlcA pathogenicity factors. Effective LD50 for wild-type strain EGDe was 1x104 CFU/mouse and 2x105 CFU/mouse for intravenous and intraperitoneal inoculation respectively. Deaths of animals were observed after 3 — 7 days. LD50 for mutant strain GIMd0028 was 1x105 CFU/mouse for intravenous inoculation. It was not possible to determine LD50 for intraperitoneal inoculation, and infection progressed atypically slowly. For example, deaths of animals were observed during 22 days (time of experiment) starting from day 4 when strain GIMd0028 in dose 106 CFU/mouse was used for inoculation. In average, death of 1 — 2 mice out of 75 inoculated was observed. Presence of L.monocytogenes was confirmed by its isolation from liver and brain of dead mice. Conclusion. Disruption of function of lmo0028 gene coding L,D-carboxypeptidase protein, which takes part in metabolism of peptidoglycan, changes dynamics of listeriosis.
Zh. Mikrobiol. (Moscow), 2009, No. 4, P. 55—59