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Biomedical subjects

R L Kent

Publications and source records attributed to R L Kent.

85 records · Page 5Linked to original sources
PubMed1978

International comparison of prevalence of resistance to antibiotics.

Prevalence of bacterial resistance to antibiotics was found to be substantially different in two separate regions of the world. The average percent resistant to individual antibiotics was nearly three times greater, and the percent of isolates resistant to six or more antibiotics 14 times greater among isolates at the Hôpital St Joseph in Paris than among those at the Peter Bent Brigham Hospital in Boston or at any of six US hospitals. Differences were not due to culture sampling or susceptibility testing methods used in the hospitals. Differences were nearly as great between isolates from patients recently admitted to the two hospitals, suggesting differences in the bacterial flora of their communities. Similar systematic comparisons of resistance prevalence in different parts of the world might help to define optimal antibiotic usage practices.

Anti-Bacterial Agents↗
PubMed1978

Associations in emergence age among permenent teeth.

Associations in the timing of emergence among the permanent teeth of Boston children were obtained from a mixed longitudinal growth study of 414 Caucasian twin pairs examined annually. Correlations were estimated by the method of maximum likelihood for corresponding left-right teeth, upper-lower teeth, and all paired combinations from central incisor to second molar in a jaw quadrant of each sex. Strong positive correlations in emergence timing prevailed throughout the dentition. Principal component analyses on correlation matrices of jaw quadrant relations for boys and girls in the maxilla and mandible showed that three components effectively explained the emergence associations among the seven permanent teeth in each jaw quadrant. Factor analytic techniques further illustrated the nature of the three components and showed the emergence relations to be essentially the same in the maxilla and mandible for both sexes. The first component was a general maturation factor influencing all of an individual's teeth to be simultaneously early or late in emerging. The remaining two components were a molar factor, affecting almost exclusively the emergence timing of the permanent first and second molars, and a duration factor that affected the duration of the emergence process for non-molar teeth, contrasting particularly the incisors and premolars.

Adolescent↗
PubMed1978

A step function model using tooth counts to assess the developmental timing of the dentition.

Step functions representing median attainment ages of successive counts on numbers of permanent teeth present in the mouth were obtained separately for 12 early-emerging teeth (I1, I2 and M1) and for 16 late-emerging teeth (C, Pm1, Pm2, and M2). Displacement of each step function to best fit of individual tooth counts defined the variation in dental maturation for early teeth and for late teeth. Moreover, differences in the displacements of the two-step functions defined individual variations in the duration of the emergence process.

Age Factors↗
PubMed1976

Skin exfoliation and purulent conjunctivitis in a new mutant-the exfoliative mouse.

A spontaneous autosomal recessive mutation has been named the exfoliative mouse (genotype ex/ex). Exfoliative mice suffer a transient purulent conjunctivitis in their 3rd week and an exfoliative skin disease in their 4th week. Gram-negative bacilli are present in blood and cerebrospinal fluid during the conjunctivitis stage, and in skin during the exfoliative period. The mutant can be differentiated from the ichthyotic mouse mutant.

Animals↗
PubMed1975

Computer surveillance of shifts in the gross patient flora during hospitalization.

Data accumulating routinely in a hospital microbiology laboratory were computer-plotted according to the number of days the patient had been in the hospital when each culture was obtained. The rate at which patients were cultured fell slightly during hospitalization, while the rate at which isolates were obtained from them increased gradually. For some species, such as Escherichia coli or Staphylococcus aureus, isolation rates changed little during hospitalization. They rose as much as sevenfold for other species, such as Pseudomonas aeruginosa or Serratia marcescens, or for a particular antibiotype of Klebsiella pneumoniae while it was an endemic nosocomial problem. These differences persisted after deletion of repeat isolates from the same patient. They appeared to reflect general shifts in composition of patient flora during hospitalization. These shifts paralleled shifts in infecting flora as represented by similar plots of isolates from blood cultures.

Bacteria↗
PubMed1974

Characterization and prevalence of the different mechanisms of resistance to beta-lactam antibiotics in clinical isolates of Escherichia coli.

A survey of clinical isolates from a hospital laboratory showed that Escherichia coli could be grouped into three classes of beta-lactam-antibiotic resistance by results of routine susceptibility testing to ampicillin, cephalothin, and carbenicillin. E. coli highly resistant to ampicillin and carbenicillin but not to cephalothin (class I) were found to have one of two levels of R factor-mediated, periplasmic-beta-lactamase which resembled R(TEM) and was located behind a permeability barrier to penicillins but not to cephalosporins. This permeability barrier appeared to act synergistically with the beta-lactamase in producing high levels of resistance to penicillins. E. coli highly resistant to ampicillin and cephalothin but not carbenicillin (class II) were found to have a beta-lactamase with predominantly cephalosporinase activity which was neither transferable nor releasable by osmotic shock. E. coli moderately resistant to one or to all three of these antibiotics (class III) were found to have low levels of different beta-lactamases including a transferable beta-lactamase which resembled R(1818). Thus, different mechanisms producing resistance to beta-lactam antibiotics could be deduced from the patterns of resistance to ampicillin, cephalothin, and carbenicillin found on routine susceptibility testing. E. coli of class I were much more prevalent than the other classes and the proportion of E. coli that were class I increased with duration of patient hospitalization. The incidence of class I E. coli rose only slightly over the past 7 years and that of class II E. coli remained constant despite increased usage of both cephalothin and ampicillin. These observations emphasize that the properties of the apparently limited number of individual resistance mechanisms that exist in a bacterial flora, such as their genetic mobility and linkages and the spectrum of their antibiotic inactivating enzymes and permeability barriers, may govern the effect that usage of an antibiotic has upon the prevalence of resistance to it and to other antibiotics.

Amidohydrolases↗
PubMedDate not supplied

Longitudinal principal components and non-linear regression models of early childhood growth.

The Jenss curve is a non-linear regression model which describes quite well the longitudinal length or weight measurements of an individual child from three months to six years. It is contrasted with modelling growth by longitudinal principal components analysis, an approach developed by Kent which is not restricted to any particular curve type or age range, and which can be thought of as providing the best fit among linear models having kappa parameters. Thus, in addition to being a model itself, it can be used to evaluate the success of other models. It is shown how this method differs from classical principal components. Data from Longitudinal Studies of Child Health and Development are used to explore these issues.

Child↗
PubMedDate not supplied

Laboratory surveillance of synergy between and resistance to trimethoprim and sulfonamides.

Results of susceptibility tests of Enterobacteriaceae isolated at 14 different centers demonstrate synergy between trimethoprim (TMP) and sulfamethoxazole (SMZ) against sulfonamide-susceptible isolates, which account for between less than 50% and greater than 75% of the isolates at different centers. Only 1%-4% of the isolates of Escherichia coli or Proteus mirabilis from the five centers in the United States were found to be resistant when tested with a disk containing both TMP and SMZ, but greater than 8% of such isolates from five of the other centers were resistant to the combination disk. A larger percentage of isolates of Klebsiella pneumoniae or Serratia marcescens were resistant, but the number varied from center to center. In the United States, resistance of human and animal isolates of Salmonella to the TMP-SMZ combination was almost completely absent, although greater than 50% of the animal isolates were resistant to sulfonamides. At a center that tested TMP and SMZ resistance with separate disks, resistance to TMP was found to be 30 times more common in sulfonamide-resistant than in sulfonamide-susceptible E. coli. This ratio may be useful as a monitor as treatment with TMP alone increases.

Bacteria↗
PubMedDate not supplied

The masked rat. An X-ray induced mutant with chronic blepharitis, alopecia, and pasteurellosis.

An autosomal recessive mutation had been previously X-ray-induced in the rat and named the masked rat (genotype mk/mk). This study describes the mutant's appearance, histology, and microflora. The rat's eyelids were swollen, often to the point of closure, and its face was partially covered by a brownish crust, giving the mutant a mask-like appearance. The chronic blepharitis was also accompanied by alopecia that appeared as bare patches across the mutant's back. Pasteurella pneumotropica was found in eyelids and on skin from all masked rats. The normal rat demonstrated a resistance to Pasteurella pneumotropica infection, or, conversely, the masked rat appeared to be genetically predisposed to pasteurellosis.

Alopecia↗
PubMedDate not supplied

Desktop publishing: a useful tool for scientists.

Desktop publishing offers features that are not available in word processing programs. The process yields an impressive and professional-looking document that is legible and attractive. It is a simple but effective tool to enhance the quality and appearance of your work and perhaps also increase your productivity.

Computer Graphics↗