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Biomedical subjects

N Datta

Publications and source records attributed to N Datta.

At least 91 records · Page 5Linked to original sources
PubMed1974

R factors in strains of Salmonella typhi and Shigella dysenteriae 1 isolated during epidemics in Mexico: classification by compatibility.

All 17 Salmonella typhi strains tested from the epidemic in Mexico carried R factors of compatibility group H, conferring resistance to chloramphenicol, streptomycin, tetracycline, and sulfonamides. Some S. typhi strains carried, in addition, non-conjugative, ampicillin resistance plasmids and R factors of the I or A-C complex. All 20 Shigella dysenteriae 1 strains tested of epidemic origin carried O-group R factors. Ampicillin resistance in S. dysenteriae 1 was not proved to be plasmid borne. R factors of group H were not identified in any of the tested Mexican isolates other than S. typhi, but R factors of group O were identified in Escherichia coli, Shigella flexneri, and one strain of S. typhi, as well as in the epidemic S. dysenteriae. An R factor was identified which seemed to have two compatibility specificities, groups Iomega and O.

Disease Outbreaks↗
PubMed1974

Ampicillin resistance of Shigella sonnei.

The ampicillin resistance of clinical isolates of Shigella sonnei is due to beta-lactamase production. Two kinds of resistance are found: low level, nontransmissible; and high level, tranmissible. The nontransmissible type of resistance results from a chromosomal mutation which increases the production of a beta-lactamase that hydrolyses cephalosporins relatively rapidly and gives cephalothin resistance. The transmissible type of resistance is due to an R factor mediating the synthesis of a different beta-lactamase that does not significantly hydrolyze cephalosporins or confer cephalothin resistance. One clinical isolate is shown to possess simultaneously both these mechanisms of ampicillin resistance.

Ampicillin Resistance↗
PubMed1974

Molecular specificities of R factor-determined beta-lactamases: correlation with plasmid compatibility.

Beta (beta)-lactamases determined by 29 ampicillin resistance plasmids could be divided into two types. One, TEM-type, was very uniform with respect to substrate specificity but heterogeneous in absolute levels of beta-lactamase activity. The TEM-type beta-lactamase was determined by R factors of compatibility groups FII, Ialpha, Iepsilon, N, C, A, T, W, P, L, and X, and by prophage phi Amp. The other type, characterized by the ability to hydrolyze oxacillin, was less common, showed lower absolute levels of activity, and was heterogeneous as regards substrate specificities. Oxacillin-hydrolyzing beta-lactamases were determined by R factors of compatibility groups FI, Ialpha, N, C, and O.

Ampicillin↗
PubMed1974

R62, a naturally occurring hybrid R plasmid.

R62, a naturally occurring R factor, was shown to be a single deoxyribonucleic acid molecule composed of polynucleotide sequences typical of I group plasmids and also sequences typical of the N group. It determined I pili and belonged to the Ialpha compatibility group. Although compatible with plasmids of group N, R62 showed complex genetic reactions with N plasmids which are described and interpreted. It is concluded that R62 was the product of illegitimate recombination between an I group and an N group plasmid.

Ampicillin↗
PubMed1973

Effect of stay in hospital and oral chemotherapy on the antibiotic sensitivity of bowel coliforms.

The effects of oral chemotherapy and stay in hospital on the antibiotic resistance patterns of faecal coliform flora were studied. The coliform flora of 64% of 25 patients who were not receiving antibiotics was sensitive to all drugs tested. Hospitalization alone did not affect this proportion. The administration of tetracycline or ampicillin to patients, whether at home or in hospital, significantly increased the percentage of resistant bowel coliforms. Tetracycline showed a significantly greater effect than ampicillin. There was no significant increase in the percentage of patients with resistant flora after treatment with amoxycillin.

Amines↗
PubMed1972

R factors in hospital infection.

In order to assess the clinical importance of R factors 524 "coliform" infections were studied in a general hospital. Of these, 95 were caused by Pseudomonas aeruginosa. Among the remaining 429, 43% were caused by drug-resistant enterobacteria; resistance was frequently multiple and determined by transmissible R factors. Choice of therapy was thus limited but in every case at least one antibiotic, effective in vitro, was still available.

Anti-Bacterial Agents↗
PubMed1972

Trimethoprim resistance determined by R factors.

R factors conferring a high level of resistance to trimethoprim have been identified in one strain of Escherichia coli and one of Klebsiella aerogenes, both isolated from infected urines.

Anti-Bacterial Agents↗
PubMed1972

An epidemiological study of strains of Shigella sonnei from two related outbreaks.

During the winter of 1967-8 Sonne dysentery affected neighbouring North London primary schools. This was not simply due to cross-infection between the two schools, for two different, unusual strains of Sh. sonnei were distinguished. One was a novel kanamycin-resistant colicine type 7 strain, and as far as we know this was the first school outbreak due to such a strain to be documented. The other strain was kanamycin-sensitive and of colicine type 0 with a rare specific requirement for aspartic acid. There was some evidence to suggest that the kanamycin-resistant strain was more infective for adults and possibly more pathogenic than the kanamycin-sensitive.Studies on the transfer of drug resistance and of colicinogeny revealed that the factor determining colicine type 7 was carried on a transmissible plasmid, a new observation. Various drug resistances were also transmissible experimentally, and some were spontaneously unstable. Non-transferable ampicillin-resistance in the colicine type 7 strain and aspartic acid dependence in the colicine type 0 strain enabled all but one of the isolates to be classified into two distinct lines. No common ancestor was found and it was concluded that although occurring together they must have arisen from separate sources.

Adult↗
PubMed1972

Hybridization of variants of chloramphenicol acetyltransferase specified by fi + and fi - R factors.

An fi(-) type of R factor for transferable chloramphenicol resistance carries the structural gene for a novel species of chloramphenicol acetyltransferase (EC 2.3.1.99). The enzyme associated with the fi(-) plasmid is distinct from that described for fi(+) R factors. The fi(+)- and fi(-)-related variants of chloramphenicol acetyltransferase were hybridized in vivo and in vitro. Both techniques yielded only a single symmetrical heteromeric species rather than the three (A(3)B(1), A(2)B(2), and A(1)B(3)) hybrids predicted from the tetrameric (identical monomers) structure of chloramphenicol acetyltransferase.

Acetyltransferases↗