The use of concanavalin A to measure acute phase proteins by laser nephelometry

Concanavalin A (con A) binds specifically to alpha-D-glucosyl, alpha-D-mannosyl and sterically related structures. Many serum glycoproteins contain such residues and will therefore bind and precipitate con A. Using this principle, a nephelometric method was developed for measuring total con A binding proteins in serum. The effect of parameters such as con A to glycoprotein ratio, polymer enhancement, reaction time, stability of the complexes and potential inhibitory molecules such as glucose and calcium were assessed. A brief clinical evaluation of the assay in human sera showed that con A binding correlates well with specific acute phase protein-changes in inflammatory disease and may be used as an index of disease activity. Preliminary studies show that con A binding also reflects disease activity in a number of animal species and thus may provdie a much needed index of inflammation in the experimental animal and in veterinary practice, where species specific antisera to acute phase proteins are not widely available and protein analyses have been rather neglected. The assay is rapid, cheap and may be performed on automated nephelometric systems.

Determination of antibiotic sensitivities by the Sensititre system

The Sensititre system provides antibiotics dried in microtitre trays in appropriate concentrations for the determination of minimum inhibitory concentrations (MIC) when organisms are added in liquid culture medium and incubated overnight. Results with a variety of media--for Gram-negative bacilli tested with ampicillin, carbenicillin, cephaloridine, and gentamicin, staphylococci with penicillin, cloxacillin, fusidic acid, and gentamicin, and streptococci with penicillin, ampicillin, cephaloridine, and erythromycin--were usually very similar to those of agar dilution tests. Discrepant results are found in a few situations, and in some cases, especially those involving borderline resistance to fusidic acid and gentamicin among staphylococci and Gram-negative bacilli, we have been unable to suggest modfication to produce the right results. Despite these problems, fortunately few and identifiable, we recommend the system especially for use in laboratories that determine the MICs infrequently.

Antibiotic susceptibilities of streptococci from the mouth and blood of patients treated with penicillin or lincomycin and clindamycin

Patients undergoing dental extractions were non-randomly allocated to three groups, one of which received no antibiotic, one benzylpenicillin followed by oral penicillin for 5 days, and the third intramuscular lincomycin followed by oral clindamycin. Dental extraction was performed at the beginning of the course of chemotherapy. Streptococci were isolated from the extracted teeth, from blood cultures collected before and immediately after dental extraction, and from sutures removed from the gums 5-7 days after the operation. The species of these organisms was determined, and their susceptibilities to penicillin, clindamycin, cephaloridine, erythromycin and tetracycline were assessed. The majority of streptococci isolated from teeth belonged to the species Streptococcus sanguis, S. mitior, S. mutans and S. milleri. Occasional isolates of each of these organisms collected before the antibiotic could take effect were resistant to penicillin. Three of these species, but not S. mutans, were the commonest streptococci to be isolated from the blood after dental extraction. Penicillin completely suppressed dental bacteriaemia under the conditions of our investigation, and lincomycin reduced the incidence by about 60 per cent. The commonest streptococci from sutures were also S. sanguis, S. mitior, S. mutans and S. milleri. S. faecalis was also isolated, but only in patients who had received antibiotics. Among the non-faecalis organisms, penicillin resistance was significantly more frequent among isolates from patients given penicillin than from patients not given this antibiotic, and clindamycin resistance was significantly more frequent among isolates from patients given lincomycin and clindamycin than from patients not given these antibiotics.

A comparison of methods for the immunoassay of serum apolipoprotein B in man

Three assays for serum apolipoprotein B, radioimmunoassay, automated immunoprecipitation and rocket immunoelectrophoresis were compared. The antiserum used was raised against lipoprotein of density 1.040-1.053 g/ml (lipoprotein B). Each of the methods had a high degree of specificity when tested against potential interfering substances. The lowest levels of apolipoprotein B could be measured with radioimmunoassay but this sensitivity entailed the use of high dilutions of serum and resulted in a lower precision. Concentration response curves of lipoprotein B solution and serum were parallel for radioimmunoassay and automated immunoprecipitation but were not for rocket immunoelectrophoresis. Serum apolipoprotein B could be assayed by immunoelectrophoresis, however, if serum calibrated against the protein concentration of lipoprotein B solution by either of the other two methods was used as a secondary standard. Such a secondary serum standard also proved advantageous for all the methods because of the relative stability of the apolipoprotein B content of serum as compared to aqueous solutions of lipoprotein B. The mean apolipoprotein B concentration in 29 normolipaemic subjects aged 20-30 years was 0.84 +/- 0.12 g/1 (mean +/- S.D.) by radioimmunoassay, 0.85 +/- 0.11 g/1 by automated immunoprecipitation and 0.88 +/- 0.11 g/1 by rocket immunoelectrophoresis. The correlation between apolipoprotein B levels measured by the three methods was good. The ratio of serum cholesterol to serum apolipoprotein B was unaffected by individual differences in serum cholesterol or triglyceride levels. There was no significant difference between fasting and post-prandial serum apolipoprotein B concentrations. Radioimmunoassay is particularly suited to the measurement of low levels of apolipoprotein B, automated immunoprecipitation for large numbers of samples and rocket immunoelectrophoresis, when care is taken in the interpretation of results, for small numbers of samples.

Activity of sulfamethoxazole and trimethoprim against Bacteroides fragilis

Minimum inhibitory concentrations (MICs) of sulfamethoxazole (SMX) and trimethoprim (TMP), alone and in three combinations, 20:1, 1:1, and 1:20, were determined on Diagnostic Sensitivity Test (DST) and Mueller-Hinton (MH) agars containing lysed blood for various inocula of 91 strains of Bacteroides fragilis from the U.S.A. and U.K. MICs of SMX were high with large inocula and higher on MH than DST, but results for TMP were less affected by these two factors. True SMX resistance was rare: 10 U.S.A. strains previously reported as resistant appeared to be susceptible. Maximum potentiation of MICs was observed when SMX and TMP were combined in ratios close to those of the ratios of their MICs, that is, SMX/TMP 20:1 for large inocula and the reverse for small inocula for determinations on DST and usually 20:1 for all inoculum sizes on MH. These observations explain some of the discrepancies in reports, but defer the problem of potential usefulness of the drugs in the treatment of infection with anaerobes to future study.

Tranquilizers or anti-depressants for chronic schizophrenics: a long term study

The relative efficacy of 4 tranquilizers was investigated in 66 chronic schizophrenics who had been hospitalized for 10.01 years (mean). The role of adding an anti-depressant was also studied. Following a 4 week placebo period, high dosage tranquilizers were given for 16 weeks and amitriptyline was added for the following 16 weeks. Statistical analyses of the various change measures revealed that patients worsened significantly on placebo, all 4 tranquilizers were significantly better than placebo for symptom reduction and maximum improvement was attained within 16 weeks of tranquilizer administration. No significant differences in efficacy were observed among the 4 tranquilizers and addition of amitriptyline did not confer any additional therapeutic advantage.

Serum gentamicin assay: a comparison and assessment of different methods

We have compared, in a clinical laboratory, three methods for estimating the concentration of gentamicin in serum. The adenylase method is most accurate, but requires considerable skilled technical time and expensive apparatus. The urease method requires an accurate pH meter but is otherwise inexpensive, but in our hands, although it produces results most rapidly, it also requires considerable technician time and is least accurate. The agar diffusion method requires no expensive apparatus, least technician time, and produces results of acceptable accuracy. It does, however, take longer than the other two methods to produce results.

Assessment of fetal lung maturity by estimation of amniotic fluid palmitic acid

The measurement of palmitic acid in amniotic fluid has been shown to be a rapid means of assessing the lecithin concentration. The level of palmitic acid increases quickly when the fetal lung matures at about 35 weeks' gestation, and the level in amniotic fluid obtained 24 hours or less before delivery clearly distinguishes which infants are likely to develop respiratory distress syndrome and which are mature.

In-vitro comparison of erythromycin, lincomycin, and clindamycin

The in-vitro antibacterial activities of erythromycin, lincomycin, and clindamycin, a new derivative of lincomycin, were compared. Clindamycin was always more active than lincomycin, and was either as active as erythromycin or more so against betahaemolytic streptococci, Streptococcus viridans, Str. pneumoniae, and erythromycin-sensitive Staphylococcus aureus. It was also fully active against most erythromycin-resistant strains of Staph. aureus. On the other hand, it was somewhat less active than erythromycin against Haemophilus influenzae and considerably less active than erythromycin against Str. faecalis and Neisseria gonorrhoeae.Clinical trials seem to be justified in infections with sensitive organisms for which erythromycin might have been indicated.