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Biomedical subjects

I B Duncan

Publications and source records attributed to I B Duncan.

At least 37 records · Page 2Linked to original sources
PubMed1980

Herpes simplex virus depresses antibody production by affecting T-cell function.

Many viruses enter lympho-reticular cells during pathogenesis and thereby induce immunosuppression, which is of practical importance in that it may be related to overall virulence. Immunosuppression may result from a selective infection, as viruses often show an affinity for different lymphocyte subpopulations: Epstein-Barr virus, for example, infects only a small percentage of B cells. We reported previously that herpes simplex virus (HSV) type 1 suppressed the induction of an antibody response to diphtheria toxoid in cultures of human tonsil cells, and that this seemed to result from the infection of a small percentage of T lymphocytes. However, as fully infectious virus was used in these experiments, it had probably spread from cell to cell in the course of the culture, so complicating the interpretation of the results. Accordingly, we have now reinvestigated the mechanism of immunosuppression using temperature-sensitivity (ts) mutants which fail to complete their growth cycle in the conditions selected for antibody synthesis. In this study, mutants tsB, tsD and tsF, derived from HSV type 1 strain 17, and ts 9, derived from HSV type 2 HG 52, were used. The results suggest that the immunosuppression is due to the selective infection by the viruses of helper T cells.

Antibody Formation↗
PubMed1979

O serotyping of Providencia stuartii isolates collected from twelve hospitals.

A collection of 829 isolates of Providencia stuartii, mostly from urological specimens of patients in 12 hospitals, were O serotyped. Hospitals varied in serotype distribution, but most isolates (97%) fell into one or another of 14 O types of P. stuartii. One type (O63) was found in 10 hospitals, and six types (O4, O17, O25, O52, O55, O56) were found in 5 or more hospitals. These seven types were more common than others and included 753 (91%) of the isolates. Only four isolates agglutinated in Providencia alcalifaciens antisera and, for increased efficiency in serotyping, it is recommended that separate schemes be employed for P. stuartii and P. alcalifaciens. Strains endemic in different hospitals may differ in serotype and give rise to nosocomial infections that are clinically recognizable when infections occur in obvious clusters. Nosocomial infections occurring in low frequency among patients not located close to each other in the hospital may be detected with the aid of serotyping.

Canada↗
PubMed1978

Comparison of bacteriophage typing, serotyping, and biotyping as aids in epidemiological surveillance of Klebsiella infections.

Bacteriophage typing was used to subdivide Klebsiella obtained from patients in a surgical intensive care unit during a 2-year period. The 15 phages employed to type the strains were propagated by a soft-agar layer technique. In all, 23 phage types were found among the 120 clinical strains. The phage types of repeat isolates were reproducible. Only 70% of the strains tested were phage typable, but when used in conjunction with capsular serotyping and biotyping, a much greater subdivision of the Klebsiella strains was achieved. The addition of phage typing to serobiotyping for epidemiological analysis suggested that the number of cross-infecting Klebsiella strains in the intensive care unit was few, but that these strains persisted in the unit for long periods of time and could infect different body sites.

Bacteriophage Typing↗
PubMed1977

Emergence of gentamicin-resistant Klebsiella in a general hospital.

Gentamicin had been in use in a general hospital for over 7 years before any gentamicin-resistant Klebsiella were observed. In 1974 and 1975, nine different gentamicin-resistant serobiotypes of Klebsiella were isolated from 35 patients. The first strain to appear had R-factor-mediated gentamicin resistance, and it infected 19 patients during a period of almost 2 years, spreading largely by case-to-case infection in patients with urinary catheters. It appeared to lose the capacity to transfer its gentamicin resistance after it had infected five of the patients. We had previously isolated on the same ward a gentamicin-susceptible Klebsiella of identical type, and it was found to be capable of acquiring an R-factor for gentamicin resistance. All of the other types of gentamicin-resistant Klebsiella infected few patients and did not persist in the hospital; four of them had R-factor-mediated resistance to gentamicin and all four, as did the original strain, cotransferred kanamycin, neomycin, and tobramycin resistance. Every gentamicin-resistant Klebsiella was susceptible to amikacin and netilmicin.

Aminoglycosides↗
PubMed1976

Preparation of typing antisera specific for O antigens of Pseudomonas aeruginosa.

Results of serotyping 966 clinical isolates of Pseudomonas aeruginosa showed that 72% agglutinated specifically in one or another of the 16 typing antisera, but 28% agglutinated in two or more and often in as many as 10 antisera; this polyagglutinability correlated with a high incidence of cross-reactivity among the antisera. Absorption of each typing antiserum with either cell suspensions of five O-type strains or with a suspension of a particular polyagglutinable strain (SMC 247) abolished cross-reactivity in the typing antisera without significantly reducing titers against the homologous strains. All but four of the polyagglutinable strains agglutinated specifically in one or another absorbed antisera. The cross-reactions of unabsorbed antisera were interpreted to have been caused by antibodies directed not against specific O antigens but against thermostable specificities that remain undefined.

Absorption↗
PubMed1975

Epidemiology of Pseudomonas aeruginosa infections investigated by pyocin typing.

All strains of Pseudomonas aeruginosa isolated in a large Canadian hospital over a 3-year period were typed by their pyocin production. Smaller collections of P. aeruginosa from other hospitals were also typed. Almost 3000 strains were examined. The typing method did not require use of complex reagents and was successful in subdividing P. aeruginosa into numerous types. No single type was restricted to infections of one particular kind. Infections of all kinds were associated with a wide variety of pyocin types. Extensive crossinfection with one particular pyocin type was observed only in urinary infection of patients with urologic disorders. The four pyocin types that were most frequent in our entire series have been reported as the commonest types causing infections in many other parts of the world.

Cross Infection↗
PubMed1975

Epidemiology and chemotherapy of opportunistic infections due to Pseudomonas and Klebsiella.

Pseudomonas and Klebsiella are now important agents of opportunistic infection. They are widely distributed in nature, and both groups consist of many distinct types. The distribution of types of Pseudomonas aeruginosa is the same in infections and in faecal carriers and this suggests that carriers may be a major source of infecting strains. Gentamicin is effective against almost all strains of pseudomonas; carbenicillin, though not effective alone against as high a proportion of strains, acts synergistically with gentamicin. The epidemiology of Klebsiella infections is poorly understood; symptomless colonization of patients with Klebsiella is frequently the preliminary to clinical infection. Klebsiella strains show a wide range of patterns of antibiotic sensitivity, and multiresistant strains very often owe their resistance to the acquisition of R factors.

Anti-Bacterial Agents↗
PubMed1974

Susceptibility of 1,500 isolates of Pseudomonas aeruginosa to gentamicin, carbenicillin, colistin, and polymyxin B.

A series of 1,500 strains of Pseudomonas aeruginosa was collected from a variety of sources to provide a group of strains which would truly represent the species. All of them were pyocine typed, and a wide range of types was included among the isolates from each source. The gentamicin, carbenicillin, colistin, and polymyxin minimal inhibitory concentration of each strain was measured by the agar dilution method employing the Steers inocula replicator. Over 99% of strains were inhibited by 8 mug of gentamicin per ml, by 256 mug of carbenicillin per ml, and by 4 mug of colistin per ml. The small number of strains more resistant to each antibiotic comprised a variety of different pyocine types. Few strains were found to be susceptible to tetracycline, chloramphenicol, kanamycin, or streptomycin at the single concentration tested.

Carbenicillin↗
PubMed1974

Combined biochemical and serological typing of clinical isolates of Klebsiella.

In a series of 640 strains of Klebsiella isolated from clinical specimens over a 7-month period, there were sufficient biochemical differences between strains to allow a biochemical typing system to be established. Biochemical tests were done in solid media inoculated with a modified Steers inocula replicator. Biotypes were designated by a numerical coding system; 29 distinct biotypes were found among the 640 strains of Klebsiella. Serotyping of 270 of the strains was done by the Quellung reaction, and 40 capsular types were identified. Numerical biotypes and serotypes of strains appeared to vary independently. When used in conjunction, the two methods subdivided the strains into many more distinct types than either used alone. With the combined method over 100 types of Klebsiella were distinguished among the 270 isolates.

Agar↗
PubMed1971

Preliminary physiological characterization of temperature-sensitive mutants of vesicular stomatitis virus.

Different temperature-sensitive mutants of vesicular stomatitis virus have been characterized in terms of their ability to induce synthesis of viral ribonucleic acid (RNA) in BHK-21 cells at 39 C (the restrictive temperature for these mutants). Mutants belonging to complementation groups I and IV (and probably II) did not induce actinomycin-resistant RNA synthesis in infected cells incubated at 39 C. All three mutants comprising complementation group III induced viral RNA synthesis at 39 C. The temperature sensitivity of the defective viral functions has also been studied by temperature-shift experiments. The functions associated with the mutants of groups I, II, and IV were required early, whereas the function associated with the group III mutants was not required until a late stage of the viral cycle. The heat sensitivity of extracellular virion was not correlated with complementation group.

Animals↗
PubMed1971

Isolation and characterization of temperature-sensitive mutants of vesicular stomatitis virus, New Jersey serotype.

Forty-eight temperature-sensitive (ts) mutants have been isolated from a wild-type strain of the New Jersey serotype of vesicular stomatitis virus (VSV) after exposure to the base analogue mutagen 5-fluorouracil. Of these mutants, 47 have been classified into 6 nonoverlapping complementation groups containing 21, 17, 4, 3, 2, and 1 mutant, respectively (1 mutant remaining unallocated). The ribonucleic acid (RNA) phenotype of 23 of these mutants has been established. Four of the six groups contain one or more mutants unable to synthesize detectable amounts of viral RNA under restrictive conditions (39 C). No complementation was observed in mixed infection with ts mutants from the five established complementation groups of the Indiana serotype of VSV.

Animals↗