Biochemical, serologic, and sensitivity characteristics of salmonellae after long survival in soft agar

Of 60 strains of Salmonella kept in soft agar in sealed glass ampules for 35 to 40 years, 46 strains survived. The surviving strains were tested for biochemical reactions, antigenic properties, and sensitivity to seven antibiotics. Of these 46 strains, 40 were S. typhi, 2 were group A, and 4 were group B. No alterations in biochemical reactions and antigenic properties were found other than a complete loss of Vi antigen in six ampules containing surviving S. typhi. The sensitivity testing revealed a uniform absence of resistance to the antibiotics tested; only one strain of S. typhi was resistant to chloramphenicol. Comparison with the sensitivity of Salmonella isolated from infections in Greece from 1970 to 1972, revealed no difference in the sensitivity of S. typhi, but showed a marked increase in resistance of group B strains.