Biomedical subjects
Publications and source records attributed to E Yourassowsky.
The collection and transport of specimens are important steps in bacteriological diagnosis. Using blood cultures and sputum as examples, the need for close collaboration between the laboratory and the clinic is demonstrated.
Carbohydrate fermentation by anaerobic gram-negative bacilli was easily detected using Taxo-Disks placed on supplemented Columbia Agar. After incubation, two drops of a 0.2% solution of bromothymol blue were added to each disk: yellow coloring was indicative of a positive reaction. In the esculin hydrolysis test paper disks impregnated with 2 mg of esculin were placed on the same medium. The results were read after addition of two drops of a 10% solution of ferric chloride. When testing slow-growing and/or serophilic anaerobic gram-negative bacilli, such as Bacteroides melaninogenicus or Bacteroides oralis, the supplemented Columbia Agar was enriched with 10% sterile horse serum. Discrepancies between results with the conventional tube technique and the disk method were occasionally observed with salicin only.
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A novel and accurate method for predicting gentamicin peak serum concentration is described. The method considers body weight and renal function as determined by the concentration of beta 2 microglobulin in plasma. In 32 subjects whose renal function ranged from normal to severely impaired, the peak serum concentration of gentamicin was more closely correlated with beta 2 microglobulin (r = 0.69) and with creatinine clearance (r = 0.69) than with serum creatinine (r = 0.53). A nomogram was constructed which related plasma beta 2 microglobulin concentrations and body weight to predicted gentamicin peak serum concentrations. When the nomogram was clinically applied, the predicted peak gentamicin concentrations corresponded closely to the actual measurements obtained (t = 0.64; P is not significant). We suggest that plasma beta 2 microglobulin concentrations compare favorably with serum creatinine values in the prediction of gentamicin peak concentrations in patients with renal impairment.
The growth curves automatically recorded and printed during the action of 10 cephalosporins on methicillin-susceptible and methicillin-resistant Staphylococcus aureus showed the following. (i) The biomass of methicillin-susceptible S. aureus exposed to the cephalosporins increased before lysis occurred (inoculum, 10(6) colony-forming units per ml). Lysis was more rapid with cephalothin and cephaloridine, whose minimal inhibitory concentrations were lowest. (ii) The same biomass increase followed by lysis occurred with methicillin-resistant S. aureus, and the speed of lysis was not different from those of cephalothin (without any regrowth), cefoxitin (with regrowth of a few strains), and cephaloridine (regrowth of all strains), with methicillin-susceptible strains. A 2-log increase of inoculum (10(8) colony-forming units per ml) did not modify significantly the speed of lysis with cephalothin, cephaloridine, and cefoxitin, but regrowth sometimes occurred. The early transitory lysis caused by cephaloridine, cephalothin, cefamandole, and cefoxitin was not suppressed by preincubation with 32 mug of methicillin per ml, but regrowth occurred more frequently. No lysis could be observed with cefazolin, cefotaxime, cephalexin, cephradine, cefuroxime, and cefaclor unless high concentrations were achieved. (iii) From a practical point of view, the early response of the growth curve (4 h) could not determine in every case whether a strain of S. aureus was resistant or susceptible to cephalosporin. A further study of the growth curve (18 of 24 h) was necessary for this purpose. Results obtained after a few hours with automated systems should be interpreted with great caution.
A new diagnostic kit, which contains a polyvalent antiserum for either Bacteroides fragilis or Bacteroides melaninogenicus, was tested for reliability and specificity on 146 clinical samples of different origin. A correlation between the culture and immunofluorescence was observed for B. fragilis in 87.39% of cases and for B. melaninogenicus in 81.48% of cases. When pure cultures were tested, aerobically as well as anaerobically, false-positive reactions were observed with staphylococci and Clostridium ramosum spores. The well-defined morphology of these bacteria and spores allows for the elimination of any diagnostic error. The method is rapid, and the margin for error is limited. The test gives a semiquantitative idea of the number of bacteroides organisms present in the clinical specimens even in the presence of a mixed flora.
The in vitro study of the amoxicillin-clavulanate association has been carried out using a triple layer technique by means of paper strips which show a T configuration. Synergy observation proves to be most favorable with the following reservoir load: (a) when the latter is sufficiently low so that the inhibiting effect of the clavulanate and amoxicillin, taken in isolation, becomes weak or nil; (b) when the ratio between the two substances is amoxicillin 5, clavulanate 1. Under such conditions, the inhibition of the bacterial growth occurs solely in the confluence area of the substances. The neutralization of amoxicillin through penicillinase respectively after 4, 6 and 24 h of incubation makes possible an appraisal of the bactericidal action of the association.
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Three clinical pictures were found in ten cases of listeriosis after renal transplantation: septicemia (six cases), meningo-encephalitis (three cases) and asymtomatic but recurrent bacteriuria (one case). Several features demonstrate profound immunologic disturbances in the recipient: close relationship in 9 cases out of 10 between infection and high doses of immunosuppressive drugs, unfavorable outcome of graft (accelerated rejection in 4 cases out of 10) and association in one case with lethal pulmonary infection due to opportunistic agents (cytomegalovirus and Pneumocystis carinii).
During a hospital outbreak of Pseudomonas cepacia a traditional epidemiological investigation was proved to be misleading. Suppression of the suspected antiseptic did not stop the epidemics. A further investigation proved that it was due to the intravenous injection of contamineted anesthetic vials. Fever, chills, lack of hemodynamic disorders and of metastatic absceses characterize the clinical state of the infected patients. The removal of the catheters for perfusion was sometimes necessary to stop the bacteraemia. A lack of medical information is responsible of the outbreak.
A synergistic effect was shown with gentamicin and tobramycin by means of a triple layer agar technique and enzymatic inactivation of cefamandole after only four hours' incubation. When the strain is sensitive to cefamandole and aminoglycosides, synergy is observed against all the strains studied (Staphylococcus aureus, Proteus, Klebsiella, Escherichia coli, Enterobacter, and Haemophilus influenzae). No significant difference was noted between the cefamandole-tobramycin and the cefamandole-gentamicin combinations when the microbial strains were sensitive to the three antibiotics.
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In contrast to the results obtained with ampicillin, the minimum inhibitory concentrations of cefamandole against Haemophilus influenzae were within the same range (0.5 to 1.5 mug/ml) whether or not the strains were beta-lactamase producers. The minimum bactericidal concentrations were somewhat higher for beta-lactamase-positive strains (6.4 mug/ml) than for negative strains (1.2 mug/ml). In a culture with high initial microbial density, monitored by recording optical densities, the addition of 10 mug of cefamandole per ml brought about rapid lysis of a beta-lactamase-negative strain. Observation of a beta-lactamase-positive strain revealed, in the early part of the growth curve, absence of lysis and an increase of biomass similar to that observed in a drug-free control curve. In contrast to the results obtained with ampicillin, the culture consisted uniformly of spherical forms, probably in the process of division, which were capable of generating colonies. When the microbial density exposed to cefamandole was increased still further, persistent bacillary forms were observed, and after 24 h hydrolysis had eliminated every trace of microbiologically active cefamandole.
A strain of vibrio cholerae Heiberg type II, not agglutinable with any of the eight antisera corresponding to Heiberg's groups, and a nonmotile, methyl red-positivs of chronic external otitis.
A total of 314 strains of Haemophilus, isolated from clinical samples, were studied for the production of beta-galactosidase and beta-xylosidase. None of the H. influenzae strains studied (9 beta-lactamase positive strains and 129 beta-lactamase negative strains) possessed these enzymes. Both enzymes were almost constantly observed among strains of H. paraphrophilus (10 strains studied) and of H. paraphrohaemolyticus (9 strains studied). Among the other species (H. parainfluenzae, 55 strains; H. haemolyticus, 5 strains; H. parahaemolyticus, 97 strains), beta-galactosidase was present in about 30% of the strains studied whereas beta-xylosidase was detected occasionally (3% of the strains studied). Detection of these two enzymes could be a valuable test for the taxonomic study of the genus Haemophilus. However, the type of substrate used for the detection of beta-xylosidase is important: use of the para-nitro-phenyl-beta-xylopyranoside yielded more positive results than the use of its ortho-isomer.