Biomedical subjects

L G Mathieu

Publications and source records attributed to L G Mathieu.

At least 37 records · Page 2Linked to original sources

PubMed1976

[Increase of resistance to Pseudomonas aeruginosa infection in mice caused by Staphylococcus aureus].

In our study of opportunistic pathogens, we have some indication that Staphylococcus aureus can increase resistance in mice against Pseudomonas aeruginosa. Intraperitoneal injections of sublethal doses of S. aureus had a protective effect in mice against lethal doses of P. aeruginosa, more so if living and coagulase-positive S. aureus strains were injected. This protective effect was obtained both with laboratory and freshly isolated hospital strains. The interval between these infections can be extended from 2 h up to 1 week and it is still possible to observe the resistance phenomenon. The increased resistance was accompanied by a decrease in viable units of P. aeruginosa in the peritoneal cavity of mice 6 h after the injection of this species. There was no protection by S. aureus against Candida albicans in similar experimental conditions. These observations indicate that intermicrobial ecology, understood here as the previous presence of another species in a host, may be a significant factor in the resistance to infection with opportunistic pathogens such as P. aeruginosa.

Antitoxins↗

PubMed1976

[Characteristics of the increased resistance of mice to Pseudomonas aeruginosa caused by Staphylococcus aureus].

Mice were protected against a lethal dose of Pseudomonas aeruginosa by a previous sublethal infection with Staphylococcus aureus. Under similar conditions, Staphylococcus epidermidis afforded only slight protection. The following characteristics of this increased resistance that we have observed are (1) survival of mice, and decrease of the number of viable units of P. aeruginosa in the peritoneal cavity of the same mice infected with S. aureus coagulase-positive strains, either from our laboratory collection or from hospital cases, when the time interval between the injection with staphylococci and that of P. aeruginosa was between 4 and 96 h; (2) absence of a net inhibitory effect in vitro on P. aeruginosa with serum from mice infected with a sublethal dose of coagulase-positive S. aureus; (3) changes in the appearance of peritoneal exudate cells after infection with a sublethal dose of S. aureus; P. aeruginosa injected afterwards in the peritoneal cavity of mice was eliminated; when P. aeruginosa was injected alone, "activated macrophages" were not observed and bacterial cells were present in large numbers in the exudate. The immunostimulation induced by a previous sublethal injection of S. aureus coagulase-positive strains seemed to be inhibited by the immunosuppressive drug cyclophosphamide, since mice were no longer protected against a lethal dose of P. aeruginosa. Cell immunity may intervene in such infections with opportunistic species and check the invasiveness of a gram-negative bacterium superinfecting a host already exposed to coagulase-positive S. aureus.

Animals↗

PubMed1975

Isolation and partial characterization of an Escherichia coli mutant resistant to colicin A.

An Escherichia coli K12 mutant resistant to colicin A-CA31 apparently through loss of its receptor sites has been isolated and partially characterized. Resistance to colicin A was accompanied with a decreased sensitivity to colicins L-398 and E2-CA42, and to acridine dyes. The mutant strain displayed the same general pattern of tolerance or sensitivity as the parent strain towards eight antibiotics, colicins C, D, E1, E3, F2, F3, G, I, K, and N; phages T1, T2, T5, T6, T7, F2, lambda vir, P1kc, phi 80, and BF23; and to methylene blue, triphenyltetrazolium chloride, ethylenediaminetetraacetate (EDTA), deoxycholate, and sodium dodecyl sulfate. Conjugation and transduction experiments showed that a locus controlling resistance to colicin A-CA31 mapped at 21 min on the genetic map of this E. coli K12 strain.

Acridines↗

PubMed1974