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Biomedical subjects

A N Chakrabarty

Publications and source records attributed to A N Chakrabarty.

At least 73 records · Page 4Linked to original sources
PubMed1980

Single bacteriocin typing scheme for the vibrio group of organisms.

A total of 743 strains of O-I "agglutinable" and 293 strains of O I "inagglutinable" Vibrio cholerae were subjected to bacteriocin typing based on deferred antagonism of eight indicator bacteria, including two strains of V. cholerae, by the method of Chakrabarty et al. (Infect. Immun. 1:293-299, 1970). A minor modification that was effected in the typing medium was replacement of iodoacetic acid by ammonium chloride (at a final concentration of 0.003%) which appeared to regulate bacteriocin production more accurately and increase the stability of the types. Of the agglutinable strains, 94% were found to be bacteriocinogenic and could be fitted into 11 of the earlier-reported types (Chakrabarty et al., Infect. Immun. 1:293-299, 1970), and 6 newer types were recognized. Likewise, 285 (90.7%) of the inagglutinable strains were found to be bacteriocinogenic and could be accommodated within 10 original and 8 newer types identified for the inagglutinable vibrios. Thirteen types were common to the two groups of vibrios. The single bacteriocin typing scheme appeared to be simple and adequate for both groups of organisms, and the producer as well as the indicator bacteria behaved remarkably stably in this typing scheme over many years.

Bacteriocins↗
PubMed1980

Antibiotic cross-resistance patterns of ambodryl and promazine resistant mutants.

The antihistaminic drug ambodryl (Am) and the tranquillizer promazine (Pr), which had previously shown significant antimicrobial activities, were used to select bacterial mutants representing different levels of resistance to their action. These Am and Pr mutants were found to have simultaneously developed cross-resistance to penicillin (Pe), streptomycin (Sm), chloramphenicol (Cm), tetracycline (Tc) and kanamycin (Km). Certain first-step Am mutants of sensitive wild-type bacteria which were also sensitive to these antibiotics developed resistance to Pe and Sm as well as to Pr and the antihistamine benadryl (Bn). The next-step mutant of Am resistance not only doubled its resistance to these antibiotics and chemotherapeutics, but broadened its resistance-spectrum to cover Tc and Cm. These observations on cross-resistances seem to be best explained on the basis of a reduction in cell-membrane permeability acting in a nonspecific manner. The role of such cross-resistance in accounting for an overall increase in the minimum inhibitory concentrations (MIC) of many drugs against several groups of bacteria is evaluated.

Anti-Bacterial Agents↗
PubMed1979

Clostridium perfringens type A: certain characters of epidemiologic significance.

Survival of spores of Cl. perfringens type A was significantly greater than that of vegetative cells in acid pH (pH 1.2). Survival of spores in soil varied from strain to strain. Time required for 5 million spores to be reduced to 500 per gram of soil varied from 2 to 8 months with an average of 4.5+/-2.3 months. Quantitative and qualitative heat resistance studies revealed that a majority of the Indian and all the American strains tested were heat-sensitive. These characters of Cl. perfringens have an important bearing on the epidemiology of food poisoning due to this agent.

Clostridium perfringens↗
PubMed1977

Incidence and elimination of R plasmids in Vibrio cholerae.

Of 124 strains of Vibrio cholerae, 32 were multiply resistant to antibiotics. This resistance appeared to be determined by R plasmids on the basis of their effective elimination by sodium dodecyl sulfate, acridine orange, ethidium bromide, and ultraviolet radiation.

Anti-Bacterial Agents↗