Prevalance and resistance pattern of Salmonella serotypes in India.

During the period 1990-91, 3222 Salmonella strains were identified at the National Salmonella and Escherichia Centre (NSEC) at Central Research Institute, Kasauli. Of these, 2894 were from humans, 226 from poultry, 84 from animals and remaining 18 from reptiles, birds and other sources. These strains belonged to 53 different serotypes. These include 4 serotypes reported for the first time in India, namely S. kedogou, S. VP. bornheim, S. kisarawe and S. madras. Drug resistance studies revealed that 573 strains were sensitive to all the antibiotics commonly used, 1351 single drug resistant, 594 resistant to two drugs and 704 were multidrug resistant. One strain from human stool was resistant to all the antibiotics used. Prevalence of various Salmonella serotypes and their response to various drugs is discussed.

Merit of mobilization technique in transfer of non-autotransferable R-plasmids.

A total of 200 urinary isolates of Esch.coli received at National Salmonella and Escherichia Centre, Central Research Institute, Kasauli during the years 1995 to 1997 were studied for transferable drug resistance. Out of 188 strains, 134 strains showing resistance to either Nalidixic acid or Rifampicin were subjected to autotransferable resistance studies. Of these 134 strains 131 showed either partial or enbloc transfer of R-factor. Mobilization experiment successfully transferred resistance marker in 14 of the 68 isolates in which resistance to one or more drugs could not be transferred during conjugation experiment.

Adjuvant effect of DEAE-dextran and tetanus toxoid on whole cell heat inactivated phenol preserved typhoid vaccine.

Active mouse protection test (AMPT) and enzyme linked immunosorbent assay (ELISA) were used to determine the immunogenicity of whole cell typhoid vaccine when administered in conjunction with either tetanus toxoid (TT) or DEAE-Dextran (DD). Immunization of mice with whole cell typhoid vaccine showed enhanced potency either when administered in conjunction with TT or DD and values were statistically significant (p < 0.05) in comparison to conventional or standard typhoid vaccines. For ELISA, the mice were immunized with 2 different schedules, one in which a single dose of 0.25 ml subcutaneously (s/c) was administered and in another two doses of 0.25 ml each s/c, 14 days apart. In case of single dose schedule of immunization D vaccine (Whole cell typhoid + 5 mg/ml DD) showed significant increase of immune response (3.201 log10) as compared to plain vaccine (2.550 log10). Two dose schedule further increased the titres to 3.856 log10. DD adjuvanted vaccine showed higher potency by AMPT as compared to the TT adjuvanted vaccine or plain vaccine. The present study clearly demonstrates that a single dose of 0.25 ml which is equivalent to half of the conventionally used single human dose of typhoid vaccine adjuvanted with DD can significantly improve the immunogenicity of the vaccine.

Transferable beta lactam resistance against cephalosporins in Salmonella typhimurium strains in India.

From 14 strains of S. typhimurium which were resistant to three cephalosporins (cephalexin, cefadroxil and sodium cefotaxime) the resistance plasmids were transferred to two different strains (Escherichia coli K12F-Lac-Rifr and S. typhimurium LT2). The plasmids were autotransferable and the donors as well as transconjugants showed high levels of MIC (80-320 micrograms/ml or more) against these antimicrobial agents. The resistance was demonstrated to be mediated by a 15 kilobase plasmid.

Prevalence of copper resistant salmonellae in India.

Sixty eight of 330 strains of Salmonella belonging to three different serotypes, S. typhi, S. typhimurium and S. bareilly, referred to at the National Salmonella and Escherichia Centre, Central Research Institute, Kasauli, between 1989-1991 were found to be copper resistant. Maximum number of strains (39.1%) were resistant in S. bareilly serotype, followed by S. typhimurium (21.7%) and least in S. typhi (17.4%). Of the 15 States/Union Territories (UTs) from where Salmonella strains were received, copper resistance was observed in strains from 10 States/UTs. This resistance was maximum among the strains from Goa (85.7%).

Increasing prevalence of high degree resistance amongst Salmonella to different antibiotics.

National Salmonella & Escherichia Centre situated at Central Research Institute, Kasauli receives Salmonella strains from all over the country. Eight hundred and fourteen Salmonella strains belonging to 14 serotypes received during 1986 were studied for antibiotic resistance and Minimum Inhibitory concentration (MIC) with regard to ampicillin (A), chloramphenicol (C), furazolidone (Fz) and gentamicin (G). Resistance to ampicillin was found to be highest (80%) and furazolidone the least (0.1%). Similarly a large number of strains (31%) had very high MIC values greater than 640 mcg per ml for chloramphenicol, whereas only 3.4% strains were found to have MIC values greater than 640 mcg per ml for gentamicin. The present findings have been discussed in the light of similar data published from this Centre earlier and from other sources in India.