Drug resistance of enteric bacteria. 13. Distribution of R factors in Escherichia coli strains isolated from livestock

Escherichia coli strains isolated from 151 swine and 108 fowl, which were kept at the Animal Health Center, Maebashi, Japan, were surveyed for drug resistance and distribution of R factors. All of the swine and 38% of the fowl excreted E. coli strains resistant to tetracycline, chloramphenicol, streptomycin, and sulfanilamide, or certain combinations thereof. Among 278 resistant cultures isolated from swine, 13% were found to be resistant to one antibiotic, whereas 87% were resistant to more than one antibiotic. Among these resistant strains, 40% carried R factors which were transferable by the usual conjugal process. The resistance patterns of these R factors included 36% which were singly resistant and 64% which were multiply resistant. Among 54 resistant cultures isolated from fowl, 24% were singly resistant and 76% were multiply resistant. Of the resistant strains from fowl, 22% carried R factors. The resistance patterns of R factors included 50% of the singly resistant type and 50% which were multiply resistant. In spite of feeding with dairy products containing only tetracycline, a high incidence of multiple resistance was observed in the E. coli strains and the R factors isolated from these animals.

Experimental salmonellosis. X. Cellular immunity and its antibody in mouse mononuclear phagocytes

A cell-associated antibody was detected in the peritoneal mononuclear phagocytes (referred to as monocytes) of mice hyperimmunized with live vaccine of Salmonella enteritidis, by use of immune transfer and immune adherence hemagglutination techniques. The cellular antibody inhibited the growth of a virulent strain of S. enteritidis with the aid of complement and lysozyme on nutrient agar plates. This type of bactericidal antibody could not be detected in the monocytes of mice immunized with killed vaccine of S. enteritidis. The antibody extracted from the peritoneal monocytes of mice hyperimmunized with live vaccine was identified as a macroglobulin by ultracentrifugal analysis.

Experimental salmonellosis. 8. Postinfective immunity and its significance for conferring cellular immunity

In the process of live-vaccine immunization of Salmonella enteritidis infection in mice, the relation between the number of bacteria in the organs of mice and their protecting effect was studied. Treatment with antibiotics was used to control the number of immunizing bacteria in the tissues. Mice, which were infected with 10(-5) mg (1,000 mouse MLD) of virulent S. enteritidis and treated with kanamycin simultaneously, acquired high antilethal resistance against infection with the same organisms. However, the administration of large amounts of kanamycin, which caused a rapid decrease in bacterial numbers in the organs of infected mice, was incapable of conferring immunity. This indicated the necessity of persistence of live bacteria in the host for the production of immunity. A large number of microorganisms were maintained for 53 weeks in a diffusion chamber inserted into the mouse abdominal cavity. The mice implanted with diffusion chambers containing large numbers of virulent S. enteritidis did not acquire antilethal resistance against infection with the same organisms, although agglutinins against S. enteritidis were observed in these mice. Agglutinin was also found in the fluid contained in diffusion chambers inserted into mice immunized with a killed vaccine of S. enteritidis. This indicated that antibody penetrated the membrane filter of diffusion chambers from outside to inside and vice versa. From these results, it is suggested that contact of live microorganisms with the host cell is necessary for conferring postinfective immunity in salmonellosis.

Drug resistance of enteric bacteria. 8. Chromosomal location of nontransferable R factor in Escherichia coli

The R(21)(TC) factor, obtained by transduction of the R(10)(TC.CM.SM.SA) factor with phage epsilon to group E Salmonella, is not transferable by the normal conjugal process. However, when R(21)(TC)(+) transductants are infected with the F(13) factor, the nontransferable R(21)(TC) factor acquires transmissibility by conjugation. R(21)(TC)(+) conjugants of Escherichia coli K-12, to which only the R(21)(TC) factor was transmitted by cell-to-cell contact from an F' R(+) donor, were still unable to transfer their R(21)(TC) factor by conjugation. In crosses between Hfr and F(-)E. coli K-12 strains containing R(21)(TC), the gene responsible for tetracycline resistance was located on the E. coli K-12 chromosome between lac and pro, near lac.

Drug resistance of enteric bacteria. IX. Distribution of R factors in gram-negative bacteria from clinical sources

Many isolates belonging to the Enterobacteriaceae were collected in 1965 from the inpatients at geographically scattered hospitals in Japan. Among 2,650 Shigella strains examined, 58.4% were found to be drug-resistant; 95.0% of these resistant strains were multiply resistant. Among 434 resistant strains examined, 81% carried R factors that were transferable by cell-to-cell contact. Of 160 isolates of other enteric bacteria, drug-resistant strains included 84.2% of the Escherichia coli, 93.0% of the Klebsiella, and 90.0% of the Proteus cultures. Among these resistant strains, 70.3% of the E. coli, 66.7% of the Klebsiella, and 52.0% of the Proteus were multiply resistant. Of these resistant strains, 84.0% of the E. coli, 88.0% of the Klebsiella, and 50.0% of the Proteus strains carried R factors. These results indicate that R factors are widespread among gram-negative bacteria of clinical significance.

Experimental salmonellosis. VII. Comparison of the immunizing effect of live vaccine and materials extracted from Salmonella enteritidis

Kawakami, Masaya (Gunma University, Maebashi, Japan), Nobutaka Osawa, and Susumu Mitsuhashi. Experimental salmonellosis. VII. Comparison of the immunizing effect of live vaccine and materials extracted from Salmonella enteritidis. J. Bacteriol. 92:1585-1589. 1966.-Attempts were made to isolate the factors of live vaccine which immunize against Salmonella enteritidis infection in mice. Some effective substances were found in cellular extracts of this organism when those extracts were prepared by mild procedures. One of these substances was a heat-labile toxin (toxin L), which was found in an earlier study to be homogeneous as evidenced by chromatographic, ultracentrifugal, and serological analyses and which was phospholipoprotein in nature. Mice immunized with "toxin L" were protected against a 10 MLD challenge infection with a virulent strain to the same extent as animals immunized with live vaccine of an attenuated strain, SER. However, no agglutinin could be detected in sera of the animals given "toxin L." Another effective substance, endotoxin, a heat-stable toxin, which was extracted from the same organisms, demonstrated poor protective effect. Possible mechanisms of immunization with live vaccine in S. enteritidis infection in mice are discussed.

Drug resistance of enteric bacteria. VII. Recombination of R factors with tetracycline-sensitive mutants

Hashimoto, Hajime (Gunma University, Maebashi, Japan), and Susumu Mitsuhashi. Drug resistance of enteric bacteria. VII. Recombination of R factors with tetracycline-sensitive mutants. J. Bacteriol. 92:1351-1356. 1966.-The transmissible drug-resistance factor R is able to confer resistance to tetracycline (TC), chloramphenicol (CM), streptomycin (SM), and sulfonamide (SA) on a host bacterium when infected by cell-to-cell contact. Tetracycline-sensitive mutants were isolated from either CM- or SM-sensitive mutants of an R factor. Among 30 mutants isolated, 10 were point mutants which could recombine with each other, forming recombinant R factors able to grow on plates containing 50 mug/ml of TC. The recombination frequency of TC-resistant recombinants was 10(-2) to 10(-3) in bacterial cells carrying two types of TC-sensitive R factors by superinfection with both factors. Segregational patterns of the various markers on the R factor, i.e., chl, str, sul, and m, the locus determining R mating, and their linkage order, were investigated among TC-resistant recombinants of the R factor. When TC was used as the selective drug, the tet locus mapped on the R factor as an end marker. In view of the fact that these results are inconsistent with the linkage order of various markers reported previously, a circular genetic structure for the R factor which includes five tet-s and three chl-s loci is presented.

Drug resistance of enteric bacteria. VI. Introduction of bacteriophage P1CM into Salmonella typhi and formation of PldCM and F-CM elements

Kondo, Eiko (Gunma University, Maebashi, Japan), and Susumu Mitsuhashi. Drug resistance of enteric bacteria. VI. Introduction of bacteriophage P1CM into Salmonella typhi and formation of P1dCM and F-CM elements. J. Bacteriol. 91:1787-1794. 1966.-Bacteriophage P1CM was introduced into Salmonella typhi by means of both phage infection and conjugation with Escherichia coli F(+) lysogenic for the phage. Upon incubation with a P1CM phage lysate, S. typhi and S. abony yield CM(r) cells which are lysogenic for P1CM, but S. typhimurium LT2 does not. The P1CM phage is adsorbed slightly to S. typhi, but no infectious centers are formed when the phage is plated on this strain. Tests on P1CM-adsorbing capacity of the S. typhi P1CM(+) strain and on plaque formation and transduction ability of the recovered phage from this strain indicated that the cell and the phage population did not have any special advantage over the original cell and phage population. Conjugation of S. typhi with E. coli F(+) carrying P1CM(+) gave three types of S. typhi CM(r) clones: those which carry the whole P1CM phage, those with the P1dCM element, and those with nontransferable CM(r). The second type has the F factor and is sensitive to f phages in spite of its typical behavior, serologically and biochemically, as S. typhi. It can donate the P1dCM and F(+) characters to E. coli F(-) or F(-)/P1 strains. As a consequence of conjugation with the E. coli F(+) strain, the CM(r) character of the third type of S. typhi, the nontransferable CM(r) element, acquired conjugational transferability, owing to the formation of the element, F-CM. This element can be transferred to an E. coli F(-) strain at a very high frequency (ca. 10(0)). Both the F and CM(r) determinants are jointly transduced with P1 phage and are jointly eliminated by acridine dye treatment.

Drug resistance of enteric bacteria. V. High frequency of transduction of R factors with bacteriophage epsilon

Kameda, Mitsuo (Gunma University, Maebashi, Japan), Kenji Harada, Mitsue Suzuki, and Susumu Mitsuhashi. Drug resistance of enteric bacteria. V. High frequency of transduction of R factors with bacteriophage epsilon. J. Bacteriol. 90:1174-1181. 1965.-In the transduction of R factors with phage epsilon(15), a lysate capable of transducing the markers for (TC) or (CM.SM.SA) resistance at high frequency was obtained. The transducing agent is a defective element called epsilon(15)dR(23) which lacks certain functions of phage epsilon(15). After lysogenization with normal epsilon(15) phage and ultraviolet (UV) induction, strains carrying the epsilon(15)dR(23) element produce lysates which have a high frequency of transduction (HFT) on group E(1)Salmonella. Lytic lysates prepared on phage epsilon(15) sensitive strain with the epsilon(15)dR(23) element have a low frequency of transduction (LFT). Lytic growth of phage epsilon(34) on an epsilon(15)dR(23) strain or UV induction of an epsilon(34) lysogenic strain containing epsilon(15)dR(23) results in LFT lysates on group E(2)Salmonella. On UV induction, group E(2)Salmonella (epsilon(15) lysogens) with the epsilon(15)dR(23) element give lysates which are HFT on group E(1)Salmonella but are LFT when tested on group E(2)Salmonella. In all instances, the production of drug-resistant transductants requires infection of the cell with only a single epsilon(15)dR(23) element. It appears that the resistance region of the R factor has replaced that portion of phage genome which is essential for vegetative replication and superinfection immunity. The epsilon(15)dR(23) element does not contain the genetic determinants of the R factor responsible for transmissibility, inhibition of F mating, and interference between two R factors.

Experimental salmonellosis. VII. In vitro transfer of cellular immunity by ribosomal fraction of mouse mononuclear phagocytes

Sato, Ichiei (Gunma University, Maebashi, Japan), and Susumu Mitsuhashi. Experimental salmonellosis. VII. In vitro transfer of cellular immunity by ribosomal fraction of mouse mononuclear phagocytes. J. Bacteriol. 90:1194-1199. 1965.-The mononuclear phagocytes (termed monocytes) of mice hyperimmunized with live vaccine of Salmonella enteritidis inhibited the intracellular growth of virulent strain 116-54 of S. enteritidis. Also, the monocytes withstood the degeneration of cells caused by the phagocytosis of bacteria in the absence of immune serum in the tissue culture medium, termed cellular immunity. When the nonimmune monocytes were incubated with the ribosomal fraction of immune monocytes, obtained from the abdominal cavity of mice hyperimmunized with live vaccine of S. enteritidis, they acquired cellular immunity, but the monocytes did not acquire immunity when ribosomal fractions from normal mouse monocytes or from the monocytes of mice immunized with killed vaccine of S. enteritidis were used. The transfer agent present in the ribosomal fraction of immune monocytes was inactivated by treatment with ribonuclease but not with deoxyribonuclease or with trypsin.